In 2006, Schanke and coworkers found signs of degeneration in disc adjacent to Dynesys stabilization in 29% of discs after 2 years. In the same follow-up period, the authors reported complications in 17% of patients, with 4 loosen screws and 1 broken screw out of 96 screws. This proportion was maintained in a continuous follow up, after 2 years, and no progression of instability has been shown (Schaeren et al, 2008). Screw loosening was assessed by Ko and coworkers (2010). Seventy one patients, who underwent decompression and stabilization with Dynesys were evaluated. Loosening of the screws occurred in 19,7% of patients, but this did not affect their clinical improvement. It is interesting to note that such findings had never occurred in the middle vertebras in intermediary level. It´s more likely to occur on

Treatment of the dysfunctional segmental motion was assessed by Cansever and coworkers (2011), using radiologic parameters in postoperative time, in one year follow-up. Their results suggest that decompression with dynamic stabilization were effective for radiologic

A recent article described nonfusion method in lumbar spinal fractures (Kim et al, 2011). In a 4 year follow-up (2002 – 2006), their results suggests that this method is one of the most

Clinical results published with cosmic system, shows improvement in quality of life after dynamic stabilization, with decrease in visual analog scale of pain (Rodrigues et al. 2010, Strempel et al, 2006, Stremple et al, 2008). As complications, screw loosening was found in 5,2% and 5,03% cases, and just 1 case of adjacent disc degeneration was related. Screw

Rodrigues and coworkers (2010), in a retrospective evaluation of patients submitted to a pedicular dynamic stabilization with cosmic, showed an improvement in quality of life of these patients during the 29,5 months follow-up period. The SF-36 score ranging from 33.15% preoperatively, to 75.99% in the postoperative, was statistically significant using the *student t test* (p <0,0001). Maleci and coworkers (2011), using cosmic system, in a 2 year follow up period, showed good results, with a low complication rate. In this article, they emphasized advantages, such as reduction is surgical trauma, avoidance complication in graft donor site, and preservation of intervertebral cartilage. No spontaneous fusion has

Nonfusion techniques are new, compared to fusion, as an option in the surgical treatment for low back pain. As new techniques, long-term prospective studies must be designed to

effective to manage thoracolumbar fractures, especially in younger people.

breakage occurred in a low rate, but not all of them were symptomatic.

been observed in the follow-up, but a fibrous rigidity has been present.

minimum follow-up of 24 months.

marginal segments.

stability over time.

**7. Conclusion**

achieve their effectiveness.

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Strempel,A., Moosmann, D., Stoss, C., et al. (2006). Stabilization of the degenerated lumbar

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Trautwein FT, Lowery GL, Wharton ND, et al. (2010). Determination of the in vivo posterior

Tropiano P, Huang RC, Girardi FP, et al (2005) Lumbar total disc replacement. Seven to

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*Neurosurg Rev*, vol 32, No 3 (Jul 2009), pp. (335–341), ISSN 0344-5607 Sénégas J. (2002). Mechanical supplementation by non-rigid fixation in degenerative

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0362-2436

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eleven-year follow-up. *J Bone Joint Surg Am*, vol 87, No 3 (Mar 2005), pp. (490–496),

**10**

**Posterior Dynamic Stabilization:**

*Division of Neurosurgery, Saint George Hopsital University Medical Center,*

Neurogenic claudication was first related to lumbar stenosis (Verbiest H, 1954). Since, decompressive surgery was indicated in patients who failed to respond to conservative therapy. It is followed by posterior fusion in cases where the motion segment showed instability or in case where a secondary instability is expected to develop after surgery. However, while many patients have benefited from fusion procedures, successful fusion has

Evidence is growing that fusion may in fact have undesirable long-term effects on the remainder of the spine, particularly on the immediately adjacent motion segments(Kong D-S et.al, 2007; Etebar S, Cahil DW, 1999). This adjacent-level degeneration is typically seen rostral to a fused segment but may also occur caudal to a fusion, especially when the fusion occurs at the L4–5 level. The phenomenon is thought to be due to the altered biomechanics of the fused spine, where in abnormal forces acting upon the intervertebral discs and facet joints adjacent to the fused segment precipitate the accelerated failure of these stabilizing elements (Kanayama M et.al, 2001). From this evidence for adjacent-segment degeneration

Posterior dynamic stabilization, in which pedicle screw fixation is coupled with a flexible longitudinal connecting system, presumably allows for the normalization of intersegmental motion (Kaech DL et.al, 2001). This stands in contrast to traditional fusion surgery, in which the goal is complete and immediate elimination of motion and, ultimately, arthrodesis (Kaech DL et.al, 2000). While both strategies seek to address the underlying pathology of microinstability, the dynamic stabilization approach promises to do so in a more physiological manner. By "restoring" normal motion, mobility is theoretically preserved rather than eliminated, and the forces acting above and below the construct are altered to a lesser extent, reducing the potential undesirable effects of fusion (Kaech DL, Jinkins JR, 2002). Recently, new concepts, such as soft stabilization, dynamic stabilization, and motion preservation, have been explored as alternative treatment options to lumbar fusion.

not always been accompanied by clinical improvement (Adelt D et.al, 2007)

emerged the concept of "dynamic" or nonfusion stabilization of the lumbar spine.

**1. Introduction**

**2. Rational**

**The Interspinous Spacer**

Antonios El Helou and Moussa Alaywan

Antoine Nachanakian,

*Balamand Univerity,*

*Lebanon*

## **Posterior Dynamic Stabilization: The Interspinous Spacer**

Antoine Nachanakian, Antonios El Helou and Moussa Alaywan *Division of Neurosurgery, Saint George Hopsital University Medical Center, Balamand Univerity, Lebanon*

#### **1. Introduction**

188 Low Back Pain Pathogenesis and Treatment

Zigler JE. (2004) Spinal Jn Lumbar spine arthroplasty using the ProDisc II. *Spine J*, vol 4, No

Zucherman J, Hsu K, Hartjen C, et al. (2004). A prospective randomized multicenter study

*Spine*, vol30, No 12 (Jun 2005),. pp.(1351–1358), ISSN 0362-2436

for the treatment of lumbar spinal stenosis with the X STOP interspinous implant: 1-year results. *Eur Spine J*, vol 13, No 1 (Feb 2004), pp.(22–31), ISSN 0940-6719 Zucherman JF, Hsu KY, Hartjen CA, et al. (2005). A multicenter, prospective, randomized

trial evaluating the X STOP interspinous process decompression system for the treatment of neurogenic intermittent claudication. Two year follow-up results.

6 (Nov-Dec 2004), pp.(260S-267S), ISSN 1529-9430

Neurogenic claudication was first related to lumbar stenosis (Verbiest H, 1954). Since, decompressive surgery was indicated in patients who failed to respond to conservative therapy. It is followed by posterior fusion in cases where the motion segment showed instability or in case where a secondary instability is expected to develop after surgery. However, while many patients have benefited from fusion procedures, successful fusion has not always been accompanied by clinical improvement (Adelt D et.al, 2007)

Evidence is growing that fusion may in fact have undesirable long-term effects on the remainder of the spine, particularly on the immediately adjacent motion segments(Kong D-S et.al, 2007; Etebar S, Cahil DW, 1999). This adjacent-level degeneration is typically seen rostral to a fused segment but may also occur caudal to a fusion, especially when the fusion occurs at the L4–5 level. The phenomenon is thought to be due to the altered biomechanics of the fused spine, where in abnormal forces acting upon the intervertebral discs and facet joints adjacent to the fused segment precipitate the accelerated failure of these stabilizing elements (Kanayama M et.al, 2001). From this evidence for adjacent-segment degeneration emerged the concept of "dynamic" or nonfusion stabilization of the lumbar spine.

#### **2. Rational**

Posterior dynamic stabilization, in which pedicle screw fixation is coupled with a flexible longitudinal connecting system, presumably allows for the normalization of intersegmental motion (Kaech DL et.al, 2001). This stands in contrast to traditional fusion surgery, in which the goal is complete and immediate elimination of motion and, ultimately, arthrodesis (Kaech DL et.al, 2000). While both strategies seek to address the underlying pathology of microinstability, the dynamic stabilization approach promises to do so in a more physiological manner. By "restoring" normal motion, mobility is theoretically preserved rather than eliminated, and the forces acting above and below the construct are altered to a lesser extent, reducing the potential undesirable effects of fusion (Kaech DL, Jinkins JR, 2002). Recently, new concepts, such as soft stabilization, dynamic stabilization, and motion preservation, have been explored as alternative treatment options to lumbar fusion.

Posterior Dynamic Stabilization: The Interspinous Spacer 191

Preoperative patient evaluation included plain lumbar film, lumbar MRI, lumbar CT and

MRI assesses the canal and foramina stenosis and the joint synovium. In the latter, weakness or absence of the intracapsular (intra-articular) white signal on T2 weighted sequences

All patients with confirmed osteoporosis by osteodensitometry were excluded from this

**3. Decision making 3.1 Diagnostic criteria**

lumbar osteodensitometry.

type of treatment.

**3.2 Indications**

Lumbar CT assesses the lumbar facets.

Patients are eligible for enrolment if they have:

Fig. 1. Biforaminal stenosis at the level of L2-L3

consisting of bilateral lower limb paresthesia upon walking.

mainly due to facet degenerative disease (Figure 2).

signals is characteristic of degenerative disease of the joint.

Interspinous process spacers have been introduced as a possible alternative to spinal decompression and fusion for the treatment of neurogenic intermittent claudication (NIC) and discogenic lower back pain (Bowers C et.al, 2010). The interspinous devices distract the Neural Foramen, unload the intervertebral disc, and limit spinal extension, improving central canal and foraminal stenosis. Interspinous Distracter (ISD) is designed to stabilize the motion segment after neural elements decompression in lumbar stenosis, tolerating flexion and extension in this segment thus preserving the adjacent segment from deterioration.

The first interspinous device, the Wallis system (Abbott Spine), was developed in 1986 and used in patients with recurrent disc herniation. It was found to improve outcome in patients who underwent a second discectomy incorporating the Wallis device (Mariottini A, 2005). The second generation of the Wallis implant, made with elastic polyetheretherketone (PEEK), has been shown to reduce pain severity in patients with mild to moderate disc degeneration, lateral recess, central spinal stenosis, and significant lower back pain when used in combination with other surgical interventions. Other interspinous spacers used in Europe but not approved for use in the US include the DIAM (Medtronic Sofamor Danek) and the Coflex (Paradigm Spine) (Mariottini A, 2005; Sénégas J, 2002). The X-Stop device (St. Francis Medical Technologies) was approved by the US FDA in November 2005 and has been shown to be superior to nonoperative therapy in patients with NIC (Zucherman JF, 2004).

While the time course and prevalence of adjacent-segment disease are not fully known, there is increasing evidence in the spine literature that its effects may be seen soon after fusion surgery and in as many as 30% of patients(Christie SD et.al, 2005). In a recently published large retrospective analysis (Chen et.al, 2001) reported rate of clinical adjacentsegment disease was 30.3% and showed that patients in whom adjacent-level disease developed had significantly worse Oswestry Disability Index scores than those without adjacent-level disease. They further identified age > 50 years at time of surgery, increasing length of fusion, and extension of the fusion to L1–3 as significant risk factors for the development of adjacent level disease. No significant difference was identified between posterior and circumferential fusion.

Our experience is based on 87 cases performed between September 2008 and January 2011 with different lumbar spine pathologies (Table1). The ages of our patient were between 45 and 70 years, with a mean age of 55 years. All patients were treated with Interspinous Distracter (ISD).

Table 1. Pathology of the patients at the time of presentation.

#### **3. Decision making**

190 Low Back Pain Pathogenesis and Treatment

Interspinous process spacers have been introduced as a possible alternative to spinal decompression and fusion for the treatment of neurogenic intermittent claudication (NIC) and discogenic lower back pain (Bowers C et.al, 2010). The interspinous devices distract the Neural Foramen, unload the intervertebral disc, and limit spinal extension, improving central canal and foraminal stenosis. Interspinous Distracter (ISD) is designed to stabilize the motion segment after neural elements decompression in lumbar stenosis, tolerating flexion and extension in this segment thus preserving the adjacent segment from

The first interspinous device, the Wallis system (Abbott Spine), was developed in 1986 and used in patients with recurrent disc herniation. It was found to improve outcome in patients who underwent a second discectomy incorporating the Wallis device (Mariottini A, 2005). The second generation of the Wallis implant, made with elastic polyetheretherketone (PEEK), has been shown to reduce pain severity in patients with mild to moderate disc degeneration, lateral recess, central spinal stenosis, and significant lower back pain when used in combination with other surgical interventions. Other interspinous spacers used in Europe but not approved for use in the US include the DIAM (Medtronic Sofamor Danek) and the Coflex (Paradigm Spine) (Mariottini A, 2005; Sénégas J, 2002). The X-Stop device (St. Francis Medical Technologies) was approved by the US FDA in November 2005 and has been shown to be superior to nonoperative therapy in patients with NIC (Zucherman JF,

While the time course and prevalence of adjacent-segment disease are not fully known, there is increasing evidence in the spine literature that its effects may be seen soon after fusion surgery and in as many as 30% of patients(Christie SD et.al, 2005). In a recently published large retrospective analysis (Chen et.al, 2001) reported rate of clinical adjacentsegment disease was 30.3% and showed that patients in whom adjacent-level disease developed had significantly worse Oswestry Disability Index scores than those without adjacent-level disease. They further identified age > 50 years at time of surgery, increasing length of fusion, and extension of the fusion to L1–3 as significant risk factors for the development of adjacent level disease. No significant difference was identified between

Our experience is based on 87 cases performed between September 2008 and January 2011 with different lumbar spine pathologies (Table1). The ages of our patient were between 45 and 70 years, with a mean age of 55 years. All patients were treated with Interspinous

**cases Pathology Male / female**

33 Bi-Foraminal stenosis 24/9 21 Lig. flavum hypertrophy 6/15 18 Suspended vertebrae 12/6 9 Facet syndrome All females 6 Adjacent syndrome 3/3

Table 1. Pathology of the patients at the time of presentation.

**ratio**

deterioration.

2004).

posterior and circumferential fusion.

Distracter (ISD).

**Number of**

#### **3.1 Diagnostic criteria**

Preoperative patient evaluation included plain lumbar film, lumbar MRI, lumbar CT and lumbar osteodensitometry.

MRI assesses the canal and foramina stenosis and the joint synovium. In the latter, weakness or absence of the intracapsular (intra-articular) white signal on T2 weighted sequences signals is characteristic of degenerative disease of the joint.

Lumbar CT assesses the lumbar facets.

All patients with confirmed osteoporosis by osteodensitometry were excluded from this type of treatment.

#### **3.2 Indications**

Patients are eligible for enrolment if they have:

Fig. 1. Biforaminal stenosis at the level of L2-L3

Posterior Dynamic Stabilization: The Interspinous Spacer 193

In our institution, patients are admitted for 24 hours before the day of the procedure. In preop, the patient is asked to hold anti-platelets and other anti-coagulation for 5 days. Only

Post op, spinal cord X-ray of the operated region is done. The patient is ambulated with

Several models of interspinous distracter (ISD) have been proposed to stabilize the spine tolerating in the same time a certain degree of mobility of the concerned motion segment and preserving the adjacent segment from later damage. Biomechanical studies show that those devices offer a non-rigid fixation and can return a destabilized specimen back to the intact condition in terms of motion in flexion/extension and axial rotation (Samani J, 2002; Tsai KJ et.al, 2006) . It is a biomechanical alternative to a total laminectomy with pedicle

Furthermore the implant does not significantly change the intradiscal pressures at the adjacent levels, yet it significantly unloads the intervertebral disc at the instrumented level

Thus the characteristics of those devices meet the profile needed for cases where minor to moderate instability is expected in the treatment of lumbar stenosis preventing as well a

The procedure is done under general anesthesia. All patients were operated in a prone position, flexed on a Wilson surgical frame with the thoracolumbar spine segment in neutral to a slightly kyphotic position, avoiding hyperlordosis for a better interspinous distraction.

Different interspinous spacers types, the DIAM (Medtronic Sofamor Danek), the Coflex (Paradigm Spine) and The X-Stop device (St. Francis Medical Technologies), are used in our

A set of lumbar laminectomy is used. In addition, a set of interspinous spacer measurer is

LMWH can be tolerated up to 12 hours before the procedure.

Usually, the patients had regular follow up at 1, 3 and 12 months.

in the neutral and extended positions (Vena P et.al, 2005).

utilized to define the depth and width of the spacer to be used.

future deterioration of the adjacent motion segment.

over time

**3.4 Hospitalization and follow up**

**3.5 Biomechanics of interspinous spacer:**

screw and rod fixation (Lee CK, 1988).

**3.6 Surgery**

**<IP_ADDRESS> Preparation**

**<IP_ADDRESS> Product used**

institution (Figure 4).

**<IP_ADDRESS> The instrument used**

**3.6.1 Operative technique**

abdominal belt for 1 month.

stabilization is done to decrease and/or avoid the harmful effects of rigid fusion like, listhesis, instability, hypertrophic facet joint arthritis, herniated nucleus pulposus, and stenosis.

Fig. 2. L4 **Suspended vertebra** treated with 2 interspinous spacers L3-L4 and L4-L5, fixing the L4**.**

Fig. 3. Facet syndrome: lack of synovial fluid at the level of L4-L5 joint; a sign of degeneration.

#### **3.3 Contra indications**

#### **3.4 Hospitalization and follow up**

192 Low Back Pain Pathogenesis and Treatment

Fig. 3. Facet syndrome: lack of synovial fluid at the level of L4-L5 joint; a sign of

Fig. 2. L4 **Suspended vertebra** treated with 2 interspinous spacers L3-L4 and L4-L5, fixing

stenosis.

the L4**.**

degeneration.

**3.3 Contra indications**

stabilization is done to decrease and/or avoid the harmful effects of rigid fusion like, listhesis, instability, hypertrophic facet joint arthritis, herniated nucleus pulposus, and

> In our institution, patients are admitted for 24 hours before the day of the procedure. In preop, the patient is asked to hold anti-platelets and other anti-coagulation for 5 days. Only LMWH can be tolerated up to 12 hours before the procedure.

> Post op, spinal cord X-ray of the operated region is done. The patient is ambulated with abdominal belt for 1 month.

Usually, the patients had regular follow up at 1, 3 and 12 months.

#### **3.5 Biomechanics of interspinous spacer:**

Several models of interspinous distracter (ISD) have been proposed to stabilize the spine tolerating in the same time a certain degree of mobility of the concerned motion segment and preserving the adjacent segment from later damage. Biomechanical studies show that those devices offer a non-rigid fixation and can return a destabilized specimen back to the intact condition in terms of motion in flexion/extension and axial rotation (Samani J, 2002; Tsai KJ et.al, 2006) .

Furthermore the implant does not significantly change the intradiscal pressures at the adjacent levels, yet it significantly unloads the intervertebral disc at the instrumented level in the neutral and extended positions (Vena P et.al, 2005).

Thus the characteristics of those devices meet the profile needed for cases where minor to moderate instability is expected in the treatment of lumbar stenosis preventing as well a future deterioration of the adjacent motion segment.

#### **3.6 Surgery**

#### **3.6.1 Operative technique**

#### **<IP_ADDRESS> Preparation**

The procedure is done under general anesthesia. All patients were operated in a prone position, flexed on a Wilson surgical frame with the thoracolumbar spine segment in neutral to a slightly kyphotic position, avoiding hyperlordosis for a better interspinous distraction.

#### **<IP_ADDRESS> Product used**

Different interspinous spacers types, the DIAM (Medtronic Sofamor Danek), the Coflex (Paradigm Spine) and The X-Stop device (St. Francis Medical Technologies), are used in our institution (Figure 4).

#### **<IP_ADDRESS> The instrument used**

A set of lumbar laminectomy is used. In addition, a set of interspinous spacer measurer is utilized to define the depth and width of the spacer to be used.

Posterior Dynamic Stabilization: The Interspinous Spacer 195

Fig. 5. Interspinous distracter implanted between spinous processes L3-L4 and L4-L5, the desinserted and retracted laterally supraspinous ligament, will be sutured to its initial place.

(Figure 6).

**3.7 Long term results**

post op period, the pain was at 4.9/10 on VAS.(Table 2).

2.1/10 on VAS, and up to 45% of patients were pain free.

Control lumbo-sacral x-ray is done in 2 views to evaluate the created distraction. All patients were put in a lumbar brace, for a period of one month during their daily activities

Overall improvement was noted in ISD-treated patients, with considerable satisfaction in 75 % of patients on average. The patient at first reported an improvement of their radicular pain with a mean reduction of 3/10 on visual analog scale (VAS) (scale for 0: absent pain to 10 severe intolerable pain necessitating Intra venous treatment). In the pre-operative, radicular pain when existent had a mean score of 8.3/10 on VAS. Whereas, in the immediate

Postoperative walking distance progressively increased during the next 3 months. Patients achieved maximum improvement after an average period of 6 months, with a mean score of

The prominent characteristic of this surgery is a low level of postoperative pain.

Fig. 4. Right case of DIAM spacer. Left case of X-Stop spacer.

#### **3.6.2 Operative procedure**

The level of the procedure is localized under fluoroscopy after positioning. Middline vertical skin incision is done. Dissection of the subcutaneous layer and the paraspinal muscles until identification of the articular facets.

The decompression of the neural elements for stenosis is made through surgical interlaminar fenestrations with flavectomy and opening of the lateral recess, and not by the old-fashioned laminectomy. For the insertion of the ISD the interspinous ligament is resected with temporary disinsertion and retraction of the supraspinous ligament.

Adequate preparation of the interspinous space; removal of all soft tissues and flattening of the bony walls to a straight parallel nidus were ended with an adequate insertion.

Proper depth of the incorporation of ISD was determined following direct spacing of 3-4 mm between the deepest point of the device and the dural sac placing through that space a midsize hook.

One or two interspinous spaces were treated according to the preoperative plan. ISD were inserted, the laterally retracted supraspinous ligament was always stitched to its initial location at the top of the spinous processes (Figure 5).

Discectomy is performed in cases where the protruded/ herniated disc is still compressing the root(s) despite the ligaments resection and the bone recalibrations are done. In cases where the disc is protruded/ herniated, medially dissectomies was not done.

Regular closure of layers and placing of deep hemovac drain ended the surgery.

#### **3.6.3 Post-operative care**

The patient is out of bed the day after surgery and discharged on day 3 after surgery, or on day 2 when drain was not inserted.

The level of the procedure is localized under fluoroscopy after positioning. Middline vertical skin incision is done. Dissection of the subcutaneous layer and the paraspinal muscles until

The decompression of the neural elements for stenosis is made through surgical interlaminar fenestrations with flavectomy and opening of the lateral recess, and not by the old-fashioned laminectomy. For the insertion of the ISD the interspinous ligament is

Adequate preparation of the interspinous space; removal of all soft tissues and flattening of

Proper depth of the incorporation of ISD was determined following direct spacing of 3-4 mm between the deepest point of the device and the dural sac placing through that space a

One or two interspinous spaces were treated according to the preoperative plan. ISD were inserted, the laterally retracted supraspinous ligament was always stitched to its initial

Discectomy is performed in cases where the protruded/ herniated disc is still compressing the root(s) despite the ligaments resection and the bone recalibrations are done. In cases

The patient is out of bed the day after surgery and discharged on day 3 after surgery, or on

resected with temporary disinsertion and retraction of the supraspinous ligament.

the bony walls to a straight parallel nidus were ended with an adequate insertion.

where the disc is protruded/ herniated, medially dissectomies was not done. Regular closure of layers and placing of deep hemovac drain ended the surgery.

Fig. 4. Right case of DIAM spacer. Left case of X-Stop spacer.

location at the top of the spinous processes (Figure 5).

**3.6.2 Operative procedure**

midsize hook.

**3.6.3 Post-operative care**

day 2 when drain was not inserted.

identification of the articular facets.

Fig. 5. Interspinous distracter implanted between spinous processes L3-L4 and L4-L5, the desinserted and retracted laterally supraspinous ligament, will be sutured to its initial place.

Control lumbo-sacral x-ray is done in 2 views to evaluate the created distraction. All patients were put in a lumbar brace, for a period of one month during their daily activities (Figure 6).

#### **3.7 Long term results**

Overall improvement was noted in ISD-treated patients, with considerable satisfaction in 75 % of patients on average. The patient at first reported an improvement of their radicular pain with a mean reduction of 3/10 on visual analog scale (VAS) (scale for 0: absent pain to 10 severe intolerable pain necessitating Intra venous treatment). In the pre-operative, radicular pain when existent had a mean score of 8.3/10 on VAS. Whereas, in the immediate post op period, the pain was at 4.9/10 on VAS.(Table 2).

Postoperative walking distance progressively increased during the next 3 months. Patients achieved maximum improvement after an average period of 6 months, with a mean score of 2.1/10 on VAS, and up to 45% of patients were pain free.

The prominent characteristic of this surgery is a low level of postoperative pain.

Posterior Dynamic Stabilization: The Interspinous Spacer 197

In postoperative scanning follow-up of the patients examined, a mineralization of the spinous process in contact with the implant was found, in particular at its base which

Patients are improved in all their clinical aspects: low back pain, radicular pain and walking distance. Moderate to severe low back pain improved in 75% of patients, leg pain and claudication were improved in 87% and walking distance improved in 74% of the patients (Park S-C et.al, 2009). Patient satisfaction is 89%. These results were achieved by 1 year and

As described above the procedure has minimal post-operative back pain. And so, after the decompression done by removal of ligamentum flavum and the re-establishment of normal dynamics of the spine play a major role in the resolution of back pain. Restoration of the height of the intervertebral disc relieve the pressure on the sino-vertebral nerve which plays a major role in decreasing paraspinal muscles spasm and though the back pain. In general, back pain evaluated by the VAS with a mean score of 8.2/10 preoperatively resolves in 78 %

In general, material are well tolerated. The rate of complications is between 1 and 10 % over

Early complications include device dislocation/malposition, spinous process fractures,

One case of migration was observed in one series (Dieter A et.al, 2007). There were no

A potential complication of placement of an ISP device is fracture of the spinous processes,

In our experience, we do osteodensitometry for all patients to assess bone density in pre-op.

During operation, we should avoid bone erosions of the adjacent spinous processes.

erosion of the spinous process, infection, hematoma, and neurological sequelae.

appears to absorb high stresses due to lordosis (Sawnson KE et. al, 2003).

all. Two sets of complications exists; the early and the delayed.

broken or permanently deformed implants in all series.

**3.8.1 How to avoid complications <IP_ADDRESS> Fracture of the spinous process**

particularly related to osteopenic patients.

Bi-Foraminal stenosis 73 % Lig. flavum hypertrophy 83 % Suspended vertebrae 67 % Facetar syndrome 66 % Adjacent syndrome 96 %

Table 2. Percentage of improvement in each case.

did not deteriorate over the long-term.

of patients immediately.

**3.8 Complications**

**Cases Improvement after treatment with ISD**

Fig. 6. Top: Bi foraminal stenosis more so at the level L4-L5 then at L3-L4 levels. Bottom: Xray of adjacent interspinous spacer.

 Fig. 6. Top: Bi foraminal stenosis more so at the level L4-L5 then at L3-L4 levels. Bottom: X-

ray of adjacent interspinous spacer.

Table 2. Percentage of improvement in each case.

In postoperative scanning follow-up of the patients examined, a mineralization of the spinous process in contact with the implant was found, in particular at its base which appears to absorb high stresses due to lordosis (Sawnson KE et. al, 2003).

Patients are improved in all their clinical aspects: low back pain, radicular pain and walking distance. Moderate to severe low back pain improved in 75% of patients, leg pain and claudication were improved in 87% and walking distance improved in 74% of the patients (Park S-C et.al, 2009). Patient satisfaction is 89%. These results were achieved by 1 year and did not deteriorate over the long-term.

As described above the procedure has minimal post-operative back pain. And so, after the decompression done by removal of ligamentum flavum and the re-establishment of normal dynamics of the spine play a major role in the resolution of back pain. Restoration of the height of the intervertebral disc relieve the pressure on the sino-vertebral nerve which plays a major role in decreasing paraspinal muscles spasm and though the back pain. In general, back pain evaluated by the VAS with a mean score of 8.2/10 preoperatively resolves in 78 % of patients immediately.

#### **3.8 Complications**

In general, material are well tolerated. The rate of complications is between 1 and 10 % over all. Two sets of complications exists; the early and the delayed.

Early complications include device dislocation/malposition, spinous process fractures, erosion of the spinous process, infection, hematoma, and neurological sequelae.

One case of migration was observed in one series (Dieter A et.al, 2007). There were no broken or permanently deformed implants in all series.

#### **3.8.1 How to avoid complications**

#### **<IP_ADDRESS> Fracture of the spinous process**

A potential complication of placement of an ISP device is fracture of the spinous processes, particularly related to osteopenic patients.

In our experience, we do osteodensitometry for all patients to assess bone density in pre-op. During operation, we should avoid bone erosions of the adjacent spinous processes.

Posterior Dynamic Stabilization: The Interspinous Spacer 199

mobility and decrease nerve roots compression. It offers an alternative to rigid stabilization for lumbar stenosis with mild to moderate instability. If indicated, its use is favored compared to rigid stabilization because it preserve motion and has less harmful effect

Chen CS, Cheng CK, Liu CL, Lo WH: Stress analysis of the disc adjacent to interbody fusion

Christian Bowers, M.D., Amin Amini, M.D., M.Sc., Andrew T. Dailey, M.D. and Meic H.

Christie SD, Song KK, Fessler, RG. "Dynamic Interspinous Process Technology." *Spine* 30-

Dieter Adelt, MD, Jacques Samani, MD, Woo-Kyung Kim, MD, PhD, Marcus Eif, MD, Gary

Doo-Sik Kong MD, Eun-Sang Kim MD, PhD, Whan Eoh, MD, PhD. One year outcome

Etebar S, Cahil DW. Risk factor for adjacent-segmental failure following lumbar fixation

Kanayama M, Hashimoto T, Shigenobu K, Harada M, Oha F, Ohkoshi Y, Tada H,

Kaech DL, Jinkins JR. The interspinous 'U': a new restabilization device for the lumbar spine Spinal Restabilization Procedures. *Elsevier Science B.V*.; 2002:355–362 Lee CK. Accelerated degeneration of the segment adjacent to a lumbar fusion. *Spine* 1988;

Mariottini A, Pieri S, Giachi S, Carangelo B, Zalaffi A, Muzii FV, et al: Preliminary results of

Sénégas J: Mechanical supplementation by non-rigid fixation in degenerative intervertebral lumbar segments: the Wallis system. *Eur Spine J* 11 (Suppl 2):S164–S169, 2002 Samani, J. "Study of a Semi-Rigid Interspinous U Fixation System." Spinal Surgery, *Child*

Schlegel JD, Smith JA, Schleusener RL. Lumbar motion segment pathology adjacent to thoracolumbar, lumbar, and lumbosacral fusions. Spine 1996;21:970–8 Seong-cheol Park, Sang Hoon Yoon, Yong-Pyo Hong, Ki-jeong Kim, M, Sang-Ki Chung,

a soft novel lumbar intervertebral prothesis (DIAM) in the degenerative spinal

Hyun-Jib Kim. Minimum 2-Year Follow-Up Result of Degenerative Spinal Stenosis Treated with Interspinous U (CoflexTM). *J Korean Neurosurg Soc* 46 : 292-299, 2009

compared with posterolateral lumbar fusion*. J Neurosurg* 2001; 95:5-10 Kaech DL, Fernandez C, Lombardi-Weber D. "The Interspinous U: A New Restabilization Device for the Lumbar Spine." *Spinal Restabilization Procedures*, 2000;30:355-362 Kaech DL, Fernandez C, Haninec P. "Preliminary Experience with the Interspinous U

associated with the X-Stop device. *Neurosurg Focus* 28 (6):E8, 2010

Schmidt, M.D.Dynamic interspinous process stabilization: review of complications

L.Lowery, MD, Phd and Robert J. Chomiak, MS. CoflexTM Interspinous Stabilisation: Clinical and Radiographic results from an international multicenter

evaluation after interspinous implantation for degenerative spinal stenosis with

with rigid instrumentation for degenerative instability*. J Neurosurg* 1999; 90:163-

Yamamoto K, Yamane S. Adjacent-segment morbidity after graft ligamentoplasty

compared to the risk of failed back syndrome.

2005(16S):S73-78

169.

13:375-377

in lumbar spine. *Med Eng Phys* 23:483–491, 2001

retrospective study. *Paradigm spine journal*.1-2007:1

segmental instability. *Paradigm spinal journal*.2-2007:1

pathology. *Acta Neurochir Suppl* 92:129–131, 2005

Device." *Rachis* 2001; 13:303-304

*Orthopaedics*, 2002; 1707

**5. References**

Intraoperative spinous process fracture occurred in < 1% of all cases.

Patient with the delayed spinous process fracture at more than a year had what has recently been referred to as a "sandwich phenomenon" fracture of the middle spinous process in adjacent double-level ISD placement.

#### **<IP_ADDRESS> Neurological manifestations and reoperation**

Recurrent symptoms required reoperation, microsurgical decompression and posterolateral fusion in 1.2% of cases (Figure 7).

To avoid this type of complications, a complete posterior decompression through ligamentum flavum excision and discectomy in the presence of herniated disc should be done.

Selection of patient without spondylolysthesis is mandatory to avoid postero-lateral fusion later on.

#### **4. Conclusion**

Interspinous spacer after surgical decompression for spinal stenosis by excision of Ligamentum flavum demonstrates excellent short term and long term results for improvement in back pain, neurogenic claudication and patient satisfaction. It provides restoration of disc height and reduction of vertebral slip. It helps in restoring normal lumbar mobility and decrease nerve roots compression. It offers an alternative to rigid stabilization for lumbar stenosis with mild to moderate instability. If indicated, its use is favored compared to rigid stabilization because it preserve motion and has less harmful effect compared to the risk of failed back syndrome.

#### **5. References**

198 Low Back Pain Pathogenesis and Treatment

Patient with the delayed spinous process fracture at more than a year had what has recently been referred to as a "sandwich phenomenon" fracture of the middle spinous process in

Recurrent symptoms required reoperation, microsurgical decompression and posterolateral

To avoid this type of complications, a complete posterior decompression through ligamentum flavum excision and discectomy in the presence of herniated disc should be

Selection of patient without spondylolysthesis is mandatory to avoid postero-lateral fusion

Intraoperative spinous process fracture occurred in < 1% of all cases.

Fig. 7. Adjacent segment syndrome treated by interspinous distracter

Interspinous spacer after surgical decompression for spinal stenosis by excision of Ligamentum flavum demonstrates excellent short term and long term results for improvement in back pain, neurogenic claudication and patient satisfaction. It provides restoration of disc height and reduction of vertebral slip. It helps in restoring normal lumbar

adjacent double-level ISD placement.

fusion in 1.2% of cases (Figure 7).

done.

later on.

**4. Conclusion**

**<IP_ADDRESS> Neurological manifestations and reoperation**

**11**

**Development and Clinical Evaluation**

**in the Treatment of Degenerative**

Michal Filip1, Petr Linzer1 and Jakub Strnad2

**Lumbar Spine Disease**

*1Neurosurgical Dept. KNTB Zlín,*

*2LASAK Ltd., Praque, Czech Republic*

**of Bioactive Implant for Interbody Fusion**

Due to new information about the pathophysiology and biomechanics of degenerative lumbar spine disease, the surgical treatment of this disease has undergone a significant increase over the past forty years. Novel diagnostic approaches and the development of new materials provided the impetus to produce new types of instrumentation, and these instruments have led to the modernization of interbody fusion including PLIF, TLIF and ALIF methods. These interventions are currently performed in either an open mini-invasive or endoscopic manner. The open interventions are indicated in cases where the spinal canal stenosis is caused by severe degenerative lesions affecting the motion of intervertebral discs, joints, ligaments, or vertebral arch. Despite the development of other surgical techniques (e.g., functional disc substitutes, dynamic stabilization), the posterior interbody fusion represents a powerful approach in the surgical treatment of degenerative stenosis of the

The PLIF method was first applied in the 1940s by Briggs and Milligan who inserted crushed bone grafts into the intervertebral space, and the bone grafts insertion technique was further developed by Cloward (Cloward, 1953). Due to complications associated with autografts (i.e., pain at the sampling site, procedure prolongation, etc.), the PLIF surgical technique was improved in the 1980s, and new implants constructed of various materials were developed (Bienik and Swiecki, 1991; Brantigan et al, 1994; Khoo et al, 2002; Šrámek et al, 2010). Likewise, novel diagnostic tools have been developed including MRI, 3D CT, SPECT-CT (Crock, 1976, Modic et al, 1988; Blumenthal et al, 1988), and new materials (e.g., ceramic, titanium, PEEK) have yielded new types of implants leading to the modernization of the interbody fusion via PLIF techniques (Alexander et al, 2002; Bessho et al, 1997; Brayan et al, 2002; Ciappetta et al, 1997; Kokubo, 1990; Yamamuro, 1995; Hashimoto et al, 2002; Thalgott et al, 2002; Sandhu, 2003). Currently, the majority of implants for PLIF consist of two separate components, including the solid cage shape and osseoconductive material (i.e., TCP, BMP) that ensures osteoblastic activity and the interbody fusion formation. To date, no material with both suitable mechanic properties and high grade bioactivity is currently

**1. Introduction**

spinal canal.

## **Development and Clinical Evaluation of Bioactive Implant for Interbody Fusion in the Treatment of Degenerative Lumbar Spine Disease**

Michal Filip1, Petr Linzer1 and Jakub Strnad2 *1Neurosurgical Dept. KNTB Zlín, 2LASAK Ltd., Praque, Czech Republic*

#### **1. Introduction**

200 Low Back Pain Pathogenesis and Treatment

Swanson KE, Lindsey DP, Hsu KY, Zucherman JF, Yerby SA. The effects of an interspinous

Tsai KJ, Murakami H, Lowery GL, Hutton WC. A biomechanical evaluation of the

Vena P, Franzoso G, Gastaldi D, Contro R and Dallolio V. "A finite element model of the L4–

Verbiest H, A radicular syndrome from developmental narrowing of the lumbar vertevral

Zucherman JF, Hsu KY, Hartjen CA, Mehalic TF, Implicito DA, Martin MJ, et al: A

stabilization effects of an interspinous device (CoflexTM™). *J Surg Orthop Adv*

L5 spinal motion segment: biomechanical compatibility of an interspinous device."

prospective randomized multi-center study for the treatment of lumbar spinal stenosis with the X STOP interspinous implant: 1-year results*. Eur Spine J* 13: 22–31,

implant on intervertebral disc pressures. *Spine*. 2003; 28:26–32.

*Comput Methods Biomech Biomed Engin.* 2005 Feb;8(1):7-16.

canal*. J Bone Joint Surg* 36B-1954:230-237

2006;15(3):167-72.

2004

Due to new information about the pathophysiology and biomechanics of degenerative lumbar spine disease, the surgical treatment of this disease has undergone a significant increase over the past forty years. Novel diagnostic approaches and the development of new materials provided the impetus to produce new types of instrumentation, and these instruments have led to the modernization of interbody fusion including PLIF, TLIF and ALIF methods. These interventions are currently performed in either an open mini-invasive or endoscopic manner. The open interventions are indicated in cases where the spinal canal stenosis is caused by severe degenerative lesions affecting the motion of intervertebral discs, joints, ligaments, or vertebral arch. Despite the development of other surgical techniques (e.g., functional disc substitutes, dynamic stabilization), the posterior interbody fusion represents a powerful approach in the surgical treatment of degenerative stenosis of the spinal canal.

The PLIF method was first applied in the 1940s by Briggs and Milligan who inserted crushed bone grafts into the intervertebral space, and the bone grafts insertion technique was further developed by Cloward (Cloward, 1953). Due to complications associated with autografts (i.e., pain at the sampling site, procedure prolongation, etc.), the PLIF surgical technique was improved in the 1980s, and new implants constructed of various materials were developed (Bienik and Swiecki, 1991; Brantigan et al, 1994; Khoo et al, 2002; Šrámek et al, 2010). Likewise, novel diagnostic tools have been developed including MRI, 3D CT, SPECT-CT (Crock, 1976, Modic et al, 1988; Blumenthal et al, 1988), and new materials (e.g., ceramic, titanium, PEEK) have yielded new types of implants leading to the modernization of the interbody fusion via PLIF techniques (Alexander et al, 2002; Bessho et al, 1997; Brayan et al, 2002; Ciappetta et al, 1997; Kokubo, 1990; Yamamuro, 1995; Hashimoto et al, 2002; Thalgott et al, 2002; Sandhu, 2003). Currently, the majority of implants for PLIF consist of two separate components, including the solid cage shape and osseoconductive material (i.e., TCP, BMP) that ensures osteoblastic activity and the interbody fusion formation. To date, no material with both suitable mechanic properties and high grade bioactivity is currently

Development and Clinical Evaluation of Bioactive

successful surgical technique (Kurz et al, 1989).

**2.2 Development of a new implant for PLIF**

Implant for Interbody Fusion in the Treatment of Degenerative Lumbar Spine Disease 203

operated segment necessary for osteointegration of the grafts via their remodeling and PLIF formation (Bauer and Muschler, 2000). The advantage of a recently collected autolog bone graft has been the presence of live bone cells with mineralized extracellular matrix. The biological activity, structure and proteins of bone morphogenesis are important prerequisites of the fusion. In addition, clinical experiences from the first half of the 20th century have proved better surgical outcomes with autolog grafts in comparison to simple decompression (Cloward, 1953; Dawson et al, 1981; Dick, 1987; Carlson et al, 1988). Autolog grafts in this form have been the gold standard for PLIF in the majority of spondylosurgical clinics through the end of the 20th century. Despite improving surgical outcomes with a growing number of operated patients, new complications still exist regarding this otherwise

The most common complications associated with this surgery include problems with bone graft sampling in that limitations are present in bone size and structure that may be safely collected from a live patient in cases of extensive intervention. Furthermore, patients can suffer from unpleasant reactions including debilitating postoperative pain, infection, seroma, cosmetic defects, nerve injury, hip fractures, vessel injury and blood loss. These adverse reactions can occur in 10 to 39% of cases (Arrington et al, 1996; Banwart el al, 1994; Banwart et al, 1995). Therefore, these reactions and other problems have led to search for artificial materials for PLIF. The optimal material for PLIF substituting bone grafts should ideally have the following characteristics. First, the material should show solid structural support (load resistance immediately after implantation). Second, the material should display osseoconductivity and bioactivity or the ability to bind with a bone, fusion support without any other additional material (e.g., bone, BCP etc.). Third, the material should provide the possibility for a radiographical assessment of the bone fusion process. Finally, the material should show biomechanic properties (elasticity modulus similar to bone).

As described in chapter 2.1, we considered using an implant made from a synthetic material for PLIF in the early 1990s to eliminate the disadvantages of autografts (Madawi et al, 1996). The most available implants were constructed of medical steel (Bagby, 1988). However, these implants did not meet our notion of sufficient strength accompanied by bioactivity. Spondylosurgeons in Charkov (Professor Gruntovskij) have successfully used corundum implants in combination with hydroxyapatite for PLIF in the surgical treatment of degenerative lumbar spine disease in the 1980s. According to results of this clinic, the success of this implant resulted from its prism shape with projections firmly anchored in the intervertebral space that helped the implant to fixate the segment with or without transpedicular fixation following operation. Due to its bioinertion, hydroxyapatite was added, and this soft material was placed around the corundum (Rowlings, 1993; Gogolewski et al, 1993). Therefore, this implant stimulated formation of osteoblasts, and served as a conductor for their migration between adjacent surfaces of adjoining vertebral bodies. In the early 1990s, another type of prosthesis produced from bioactive glass-ceramic was developed by Electric Nippon Glass, and was used by Japanese orthopedists for PLIF (Yamamuro, 1995, Kokubo, 1990). While transpedicular fixation was added to PLIF due to its fragility, the bioactivity of the implant surface allowed fusion due to migration of bone cells along its surface without addition of any supporting material (e.g., bone,

available. For instance, solid materials (e.g., medical steel, titanium, PEEK) lack bioactivity that is able to support the osseoconduction (Carlson et al, 1988; Williams and McNamara, 1987; Zdeblick and Philips, 2003). Likewise, bioactive or resorbable materials (e.g., glassceramic, hydroxyapatite, polysacharides) do not meet the mechanical requirements for fusion implants of intervertebral discs (Hench el al, 1971; Filip et al, 1996; Sobale et al, 1990; McAfee, 1986).

Currently, the majority of implants consist of cages that form various shapes. The perimeter is constructed from a solid material that ensures the structural strength. The centre of the cage is hollow and is filled by bone grafts or osseoconductive material (e.g. bi- or tri-calcium phosphate) to promote bone fusion in this part of the implant. The optimal implant for an interbody fusion should imitate the properties of the bone tissue by combining sufficient mechanical strength as well as bioactive surface. Therefore, the mechanical strength and the shape of the implant should ensure the primary stability of the segment of the lumbar spine following the operation. Furthermore, the bioactive surface should allow stimulation of osteoblast proliferation at the interface of the implant and bone, and should promote activation of their migration along the implant surface. The bioactive surface should also act as a conductor for osteoblast migration to the fixed vertebral bodies to form the fusion. This quality would prevent the requirement for additional filling of the implant by osseoconductive material. The aim of our work was to create an implant with optimal strength and bioactivity in an attempt to replace the use of autografts and two-compartment implants for PLIF.

#### **2. Research**

#### **2.1 Advantages and disadvantages of PLIF surgical technique using autografts**

When the conservative treatment fails, patients from categories LS syndrome and FBS syndrome (Failed Back Surgery syndrome) are often referred to surgical management via posterior interbody fusion (Benzel et al, 2003; Cloward, 1953; Crock, 1976; Daniaux, 1986; Dove, 1990; Gurr et al, 1999; Cho et al, 2002). The indication for this surgery is based on neurological finding. In general, the patient predominantly either suffers from back pain associated with progression of root lesion in a lower extremity or with neurogenic claudications in the lower limbs, and shows no reaction to the full conservative therapy algorhytm (Anderson, 2000; Brinnckman et al, 1989; Brodke et al, 1997; Cloward, 1953, Hrabálek et al, 2009; Paleček et al, 1994; Fischgrund et al, 1997). Furthermore, the disease is supported by graphic images of compression of the neural structures caused by degenerative lesions (Knudson, 1944; Crock, 1978; Modick et al, 1983; Sonntag and Theodore, 2000). The desired clinical effect can be achieved by the decompression of neural structures together with spondylodesis of the affected spine segment using PLIF (Steffee, 1988; Hashimoto el al, 2002; Dick, 1987; Wang et al, 2005). When surgical treatment is necessary, no acceptable scientific long-term evidence of efficacy exists for any type of surgical treatment of the degenerative lumbar spine disease (Brodke et al, 1997; Benzel, 2003; Sonntag and Theodore, 2000; Paleček et al, 1994).

We performed PLIF using autografts that were developed in the 1980s. An autograft (mostly iliac crest bone grafts) stripped of connective tissue was inserted under compression into the intervertebral space. The best stability was achieved by transpedicular fixation of the

available. For instance, solid materials (e.g., medical steel, titanium, PEEK) lack bioactivity that is able to support the osseoconduction (Carlson et al, 1988; Williams and McNamara, 1987; Zdeblick and Philips, 2003). Likewise, bioactive or resorbable materials (e.g., glassceramic, hydroxyapatite, polysacharides) do not meet the mechanical requirements for fusion implants of intervertebral discs (Hench el al, 1971; Filip et al, 1996; Sobale et al, 1990;

Currently, the majority of implants consist of cages that form various shapes. The perimeter is constructed from a solid material that ensures the structural strength. The centre of the cage is hollow and is filled by bone grafts or osseoconductive material (e.g. bi- or tri-calcium phosphate) to promote bone fusion in this part of the implant. The optimal implant for an interbody fusion should imitate the properties of the bone tissue by combining sufficient mechanical strength as well as bioactive surface. Therefore, the mechanical strength and the shape of the implant should ensure the primary stability of the segment of the lumbar spine following the operation. Furthermore, the bioactive surface should allow stimulation of osteoblast proliferation at the interface of the implant and bone, and should promote activation of their migration along the implant surface. The bioactive surface should also act as a conductor for osteoblast migration to the fixed vertebral bodies to form the fusion. This quality would prevent the requirement for additional filling of the implant by osseoconductive material. The aim of our work was to create an implant with optimal strength and bioactivity in an attempt to replace the use of autografts and two-compartment

**2.1 Advantages and disadvantages of PLIF surgical technique using autografts**

When the conservative treatment fails, patients from categories LS syndrome and FBS syndrome (Failed Back Surgery syndrome) are often referred to surgical management via posterior interbody fusion (Benzel et al, 2003; Cloward, 1953; Crock, 1976; Daniaux, 1986; Dove, 1990; Gurr et al, 1999; Cho et al, 2002). The indication for this surgery is based on neurological finding. In general, the patient predominantly either suffers from back pain associated with progression of root lesion in a lower extremity or with neurogenic claudications in the lower limbs, and shows no reaction to the full conservative therapy algorhytm (Anderson, 2000; Brinnckman et al, 1989; Brodke et al, 1997; Cloward, 1953, Hrabálek et al, 2009; Paleček et al, 1994; Fischgrund et al, 1997). Furthermore, the disease is supported by graphic images of compression of the neural structures caused by degenerative lesions (Knudson, 1944; Crock, 1978; Modick et al, 1983; Sonntag and Theodore, 2000). The desired clinical effect can be achieved by the decompression of neural structures together with spondylodesis of the affected spine segment using PLIF (Steffee, 1988; Hashimoto el al, 2002; Dick, 1987; Wang et al, 2005). When surgical treatment is necessary, no acceptable scientific long-term evidence of efficacy exists for any type of surgical treatment of the degenerative lumbar spine disease (Brodke et al, 1997; Benzel, 2003;

We performed PLIF using autografts that were developed in the 1980s. An autograft (mostly iliac crest bone grafts) stripped of connective tissue was inserted under compression into the intervertebral space. The best stability was achieved by transpedicular fixation of the

McAfee, 1986).

implants for PLIF.

Sonntag and Theodore, 2000; Paleček et al, 1994).

**2. Research**

operated segment necessary for osteointegration of the grafts via their remodeling and PLIF formation (Bauer and Muschler, 2000). The advantage of a recently collected autolog bone graft has been the presence of live bone cells with mineralized extracellular matrix. The biological activity, structure and proteins of bone morphogenesis are important prerequisites of the fusion. In addition, clinical experiences from the first half of the 20th century have proved better surgical outcomes with autolog grafts in comparison to simple decompression (Cloward, 1953; Dawson et al, 1981; Dick, 1987; Carlson et al, 1988). Autolog grafts in this form have been the gold standard for PLIF in the majority of spondylosurgical clinics through the end of the 20th century. Despite improving surgical outcomes with a growing number of operated patients, new complications still exist regarding this otherwise successful surgical technique (Kurz et al, 1989).

The most common complications associated with this surgery include problems with bone graft sampling in that limitations are present in bone size and structure that may be safely collected from a live patient in cases of extensive intervention. Furthermore, patients can suffer from unpleasant reactions including debilitating postoperative pain, infection, seroma, cosmetic defects, nerve injury, hip fractures, vessel injury and blood loss. These adverse reactions can occur in 10 to 39% of cases (Arrington et al, 1996; Banwart el al, 1994; Banwart et al, 1995). Therefore, these reactions and other problems have led to search for artificial materials for PLIF. The optimal material for PLIF substituting bone grafts should ideally have the following characteristics. First, the material should show solid structural support (load resistance immediately after implantation). Second, the material should display osseoconductivity and bioactivity or the ability to bind with a bone, fusion support without any other additional material (e.g., bone, BCP etc.). Third, the material should provide the possibility for a radiographical assessment of the bone fusion process. Finally, the material should show biomechanic properties (elasticity modulus similar to bone).

#### **2.2 Development of a new implant for PLIF**

As described in chapter 2.1, we considered using an implant made from a synthetic material for PLIF in the early 1990s to eliminate the disadvantages of autografts (Madawi et al, 1996). The most available implants were constructed of medical steel (Bagby, 1988). However, these implants did not meet our notion of sufficient strength accompanied by bioactivity. Spondylosurgeons in Charkov (Professor Gruntovskij) have successfully used corundum implants in combination with hydroxyapatite for PLIF in the surgical treatment of degenerative lumbar spine disease in the 1980s. According to results of this clinic, the success of this implant resulted from its prism shape with projections firmly anchored in the intervertebral space that helped the implant to fixate the segment with or without transpedicular fixation following operation. Due to its bioinertion, hydroxyapatite was added, and this soft material was placed around the corundum (Rowlings, 1993; Gogolewski et al, 1993). Therefore, this implant stimulated formation of osteoblasts, and served as a conductor for their migration between adjacent surfaces of adjoining vertebral bodies. In the early 1990s, another type of prosthesis produced from bioactive glass-ceramic was developed by Electric Nippon Glass, and was used by Japanese orthopedists for PLIF (Yamamuro, 1995, Kokubo, 1990). While transpedicular fixation was added to PLIF due to its fragility, the bioactivity of the implant surface allowed fusion due to migration of bone cells along its surface without addition of any supporting material (e.g., bone,

Development and Clinical Evaluation of Bioactive

space (Figure 2).

add transpedicular fixation in high-grade instabilities.

Implant for Interbody Fusion in the Treatment of Degenerative Lumbar Spine Disease 205

We also planned to apply such PLIF methods alone in both low-grade instabilities and to

Fig. 1. Outline of the implant and its position in the interbody space (1992).

Fig. 2. Glass-ceramic implant plus application fork (1992).

**2.4 Implant made of material BAS-0 in clinical practice**

The implant was inserted using a specially developed instrumentation into the interbody

Implant BAS-O was registered by the Ministry of Health of the Czech Republic with registration number 89/492/98-IIB in 1992. After registration of the implant and based on experimental results, we introduced the implant into clinical practice in 1994. Based on the advantages from the experimental studies (e.g., stability in the operated space, restoration of anatomy, elimination of the risk of bone grafts sampling, etc.), we expected that these results would be confirmed. From 1994 to 1999, we used this technique in 65 patients observing the indication criteria and the surgical procedure described in the previous chapters. We assessed clinic and graphic postoperative findings in 25 patients out of this population during follow-ups conducted three, six, and twelve months after the intervention. The average age of the patients was 52 years. In 22 patients, the operation represented the first

hydroxyapatite) (Sobale, 1990; Yamamuro, 1995). Based on these experiences, we began searching for a material for PLIF implant that would combine the advantages of both the shape and the strength of corundum and the bioactivity of glass-ceramic used in the early 1990s. Thereby, the combination of these two properties would allow strong anchoring of this material in the intervertebral space, the restoration of anatomy in the operated segment, the stabilization of unstable segment, and the formation of interbody fusion associated with osseoconductive properties without addition of another material and without the risk of migration.

#### **2.3 Experimental development of glass-ceramic implant (BAS-O)**

Unlike bioinert or biotolerant materials, bioactive glass-ceramic material BAS-O, forms a strong chemical bond with live bone tissue (Fatley et al, 1979; Urban, 1992). Material BAS-O is prepared by progressive steps, such as sintering, controlled crystallization and others. The controlled crystallization allows control of processes that determine the bioactive ability of the final material including material transformation, the control of chemical structure, and the structure of the glass phase (Strnad, 1992). The ability of this material to form a strong bond with bone tissue results from the formation of an apatite layer on the material surface resulting in the connection of the bioactive material with body fluid. Crystallographic chemical characteristic of apatite released on the material surface is similar to the organic part of the bone tissue. Thereby, the stability of the operated segment without micromovements and the tight contact of the material without microgaps are necessary for perfect chemical bond BAS-O / live tissue. Otherwise, a risk of connective tissue penetration exists that can prevent the chemical bond on the bone / implant interface (Kokubo, 1990; Urban, 1992).

The most important finding for the planned use of the lumbar implant necessitated that the biochemical and mechanical properties of the glass-ceramic BAS-O mimic the cortical bone tissue. According to the Young model, the shape of their implant exceeded twice the strength of the vertical load, and was close to its flexural strength. Therefore, we based our implant shape on our previous experiences and according to the models that we observed during our study visits. Together with size and shape development, we also created application instrumentation used for the intervertebral space as well as the operation procedure. At this time, the fragility of the ceramic in the contact with steel represented our only disadvantage in that this fragility could cause problems with insertion using metal application instrumentation. The application instrumentation was coated by Teflon in order to prevent damage to the implant. A rectangular prism-shaped implant (25 mm long, 8 mm high and 10 mm wide) was progressively developed after repeated experiments with cadavers from 1991 to 1993 (Filip et al, 1995). "Winglets" have been placed on the opposite sides of the prism (Figure 1).

The winglets cut into the adjacent vertebral bodies after its rotation by 90 degrees, and the implant was firmly attached within the space without a risk of migration into the spinal canal. Due to its bioactivity, the implant should stimulate migration of bone cells along its surface to form interbody fusion. The application technique for the glass-ceramic implant was the same as with other implants for PLIF. During experimental application in cadavers, the implants were well-anchored in the vertebral bodies without compression of dural sac in the spinal canal, and this placement was confirmed by imaging techniques (X-ray and CT).

hydroxyapatite) (Sobale, 1990; Yamamuro, 1995). Based on these experiences, we began searching for a material for PLIF implant that would combine the advantages of both the shape and the strength of corundum and the bioactivity of glass-ceramic used in the early 1990s. Thereby, the combination of these two properties would allow strong anchoring of this material in the intervertebral space, the restoration of anatomy in the operated segment, the stabilization of unstable segment, and the formation of interbody fusion associated with osseoconductive properties without addition of another material and without the risk of

Unlike bioinert or biotolerant materials, bioactive glass-ceramic material BAS-O, forms a strong chemical bond with live bone tissue (Fatley et al, 1979; Urban, 1992). Material BAS-O is prepared by progressive steps, such as sintering, controlled crystallization and others. The controlled crystallization allows control of processes that determine the bioactive ability of the final material including material transformation, the control of chemical structure, and the structure of the glass phase (Strnad, 1992). The ability of this material to form a strong bond with bone tissue results from the formation of an apatite layer on the material surface resulting in the connection of the bioactive material with body fluid. Crystallographic chemical characteristic of apatite released on the material surface is similar to the organic part of the bone tissue. Thereby, the stability of the operated segment without micromovements and the tight contact of the material without microgaps are necessary for perfect chemical bond BAS-O / live tissue. Otherwise, a risk of connective tissue penetration exists that can prevent the chemical bond on the bone / implant interface (Kokubo, 1990;

The most important finding for the planned use of the lumbar implant necessitated that the biochemical and mechanical properties of the glass-ceramic BAS-O mimic the cortical bone tissue. According to the Young model, the shape of their implant exceeded twice the strength of the vertical load, and was close to its flexural strength. Therefore, we based our implant shape on our previous experiences and according to the models that we observed during our study visits. Together with size and shape development, we also created application instrumentation used for the intervertebral space as well as the operation procedure. At this time, the fragility of the ceramic in the contact with steel represented our only disadvantage in that this fragility could cause problems with insertion using metal application instrumentation. The application instrumentation was coated by Teflon in order to prevent damage to the implant. A rectangular prism-shaped implant (25 mm long, 8 mm high and 10 mm wide) was progressively developed after repeated experiments with cadavers from 1991 to 1993 (Filip et al, 1995). "Winglets" have been placed on the opposite

The winglets cut into the adjacent vertebral bodies after its rotation by 90 degrees, and the implant was firmly attached within the space without a risk of migration into the spinal canal. Due to its bioactivity, the implant should stimulate migration of bone cells along its surface to form interbody fusion. The application technique for the glass-ceramic implant was the same as with other implants for PLIF. During experimental application in cadavers, the implants were well-anchored in the vertebral bodies without compression of dural sac in the spinal canal, and this placement was confirmed by imaging techniques (X-ray and CT).

**2.3 Experimental development of glass-ceramic implant (BAS-O)**

migration.

Urban, 1992).

sides of the prism (Figure 1).

We also planned to apply such PLIF methods alone in both low-grade instabilities and to add transpedicular fixation in high-grade instabilities.

Fig. 1. Outline of the implant and its position in the interbody space (1992).

The implant was inserted using a specially developed instrumentation into the interbody space (Figure 2).

Fig. 2. Glass-ceramic implant plus application fork (1992).

#### **2.4 Implant made of material BAS-0 in clinical practice**

Implant BAS-O was registered by the Ministry of Health of the Czech Republic with registration number 89/492/98-IIB in 1992. After registration of the implant and based on experimental results, we introduced the implant into clinical practice in 1994. Based on the advantages from the experimental studies (e.g., stability in the operated space, restoration of anatomy, elimination of the risk of bone grafts sampling, etc.), we expected that these results would be confirmed. From 1994 to 1999, we used this technique in 65 patients observing the indication criteria and the surgical procedure described in the previous chapters. We assessed clinic and graphic postoperative findings in 25 patients out of this population during follow-ups conducted three, six, and twelve months after the intervention. The average age of the patients was 52 years. In 22 patients, the operation represented the first

Development and Clinical Evaluation of Bioactive

**BAS-O implant position on X-ray Assessment**

Table 2. Assessment of position change using X-ray.

ceramic implants (1998).

Implant for Interbody Fusion in the Treatment of Degenerative Lumbar Spine Disease 207

**Month 3**

Our results indicated that we achieved a mean improvement of I grade in the aforementioned population according to ODI assessment during twelve months [60% (severe invalidity) and 42% (moderate invalidity) with mild progression in long-term; 38% at month three and 42% at month twelve]. Using X-ray, we diagnosed implant damage without fragment(s) migration towards the spinal canal or in the prevertebral direction in five patients (20%) after twelve months. Initially, we utilized the sole interbody fixation (stand alone technique) mainly in patients with low grade instability. We found that the clinical condition stabilized in these patients, and the postoperative imaging investigation showed good fixation of the operated segment without prosthetic damage and with

No damage, no migration 25 23 20 Damage, no migration 2 3 5 (20%)

adequate postoperative changes around the nerve structures (Figure 4).

Fig. 4. MRI performed three years after operation of segment L4/5 using a pair of glass-

In case of 1st or 2nd grade translation as previously defined by Meyerding, we added posterior transpedicular fixation of the whole segment to the implant application. The assessments of the population showed advantages and disadvantages associated with the glass-ceramic implant. For example, the operation time was shortened, and firm anchoring in the interbody space was confirmed due to the shape and elimination of risk associated with bone graft sampling. However, the limiting factor for the universal use, in particular for application stand alone technique, was the mechanical resistance to bending at the ultimate load as well as the probable discongruence of the implant and the bone bed, especially related to shorter implants (under 10 mm). This finding was reflected by implant damage on X-ray in the clinical practice (see Table 2). Due to the relatively good results previously observed (Filip et al, 1996), we extended the stand alone technique to higher grades of translation. However, the lower mechanical resistance of the glass-ceramic to bending was observed, and damage of the implant was detected several months after the operation. This problem affected five patients following operation using this technique during twelve months. Despite implant damage, no migration towards the spinal canal or

**Assessment Month 6**

**Assessment Month 12**

on the spinal segment affected by degenerative instability of various types. We applied the implant BAS-O according to the experimental study. Additionally, PLIF was performed using a pair of implants by the stand alone technique in ten patients (Figure 3), and PLIF was conducted using one or two implants with additional transpedicular fixation by various companies in fifteen patients (Synthes, Stryker etc.).

Fig. 3. Fixation of L4/5 instability using a pair of glass-ceramic implants by stand alone technique (1995).

We assessed our results three, six and twelve months after the operation using the ODI score (Oswestry Disability Index; see Table 1). The Oswestry Disability Index (ODI) has become one of the principal condition-specific outcome measures used in the management of spinal disorders. We also used imaging techniques that were available at the time (i.e., X-ray, CT, rarely MRI), and we assessed the change of the implant position in the operated space (i.e., damage, dislocation) using the postoperative imaging techniques (X-ray; see Table 2).

Table 1. Clinical assessment according to ODI score.

Table 2. Assessment of position change using X-ray.

206 Low Back Pain Pathogenesis and Treatment

on the spinal segment affected by degenerative instability of various types. We applied the implant BAS-O according to the experimental study. Additionally, PLIF was performed using a pair of implants by the stand alone technique in ten patients (Figure 3), and PLIF was conducted using one or two implants with additional transpedicular fixation by various

Fig. 3. Fixation of L4/5 instability using a pair of glass-ceramic implants by stand alone

**Primary instability [n] 8**

Before operation 60 55 67 58

operation 39 36 44 38

operation 40 39 42 38

operation 42 40 46 41

**Degenerative listhesis grade I–II [n] 11**

**Isthmic listhesis up to grade II [n] 6**

We assessed our results three, six and twelve months after the operation using the ODI score (Oswestry Disability Index; see Table 1). The Oswestry Disability Index (ODI) has become one of the principal condition-specific outcome measures used in the management of spinal disorders. We also used imaging techniques that were available at the time (i.e., X-ray, CT, rarely MRI), and we assessed the change of the implant position in the operated space (i.e., damage, dislocation) using the postoperative imaging

companies in fifteen patients (Synthes, Stryker etc.).

technique (1995).

techniques (X-ray; see Table 2).

**Mean [n] 25**

Table 1. Clinical assessment according to ODI score.

**ODI score of our population [%]**

3 months after

6 months after

12 months after

Our results indicated that we achieved a mean improvement of I grade in the aforementioned population according to ODI assessment during twelve months [60% (severe invalidity) and 42% (moderate invalidity) with mild progression in long-term; 38% at month three and 42% at month twelve]. Using X-ray, we diagnosed implant damage without fragment(s) migration towards the spinal canal or in the prevertebral direction in five patients (20%) after twelve months. Initially, we utilized the sole interbody fixation (stand alone technique) mainly in patients with low grade instability. We found that the clinical condition stabilized in these patients, and the postoperative imaging investigation showed good fixation of the operated segment without prosthetic damage and with adequate postoperative changes around the nerve structures (Figure 4).

Fig. 4. MRI performed three years after operation of segment L4/5 using a pair of glassceramic implants (1998).

In case of 1st or 2nd grade translation as previously defined by Meyerding, we added posterior transpedicular fixation of the whole segment to the implant application. The assessments of the population showed advantages and disadvantages associated with the glass-ceramic implant. For example, the operation time was shortened, and firm anchoring in the interbody space was confirmed due to the shape and elimination of risk associated with bone graft sampling. However, the limiting factor for the universal use, in particular for application stand alone technique, was the mechanical resistance to bending at the ultimate load as well as the probable discongruence of the implant and the bone bed, especially related to shorter implants (under 10 mm). This finding was reflected by implant damage on X-ray in the clinical practice (see Table 2). Due to the relatively good results previously observed (Filip et al, 1996), we extended the stand alone technique to higher grades of translation. However, the lower mechanical resistance of the glass-ceramic to bending was observed, and damage of the implant was detected several months after the operation. This problem affected five patients following operation using this technique during twelve months. Despite implant damage, no migration towards the spinal canal or

Development and Clinical Evaluation of Bioactive

Tensile strength, flexural strength\*

Implant for Interbody Fusion in the Treatment of Degenerative Lumbar Spine Disease 209

Compressive strength (MPa)<PHONE_NUMBER>

Elasticity modulus (GPa) 100–120 25 220 Fracture persistence (MPa·m-1/2) ~40–100 2-12 2 Table 3. Comparison of mechanical properties of titanium, bone and glass-ceramic BAS-0.

The mechanically and chemically modified surface of the bioactive titanium by LASAK technology is able to induce the production of calcium-phosphate (apatite), and this compound arises from the interaction between the surface of the material and body fluid within hours to days. The chemical and crystallographical properties of this mineral are nearly identical with the bone apatite. Experimental studies with bioactive and bioinert titanium demonstrated that titanium with a bioactive surface better tolerates unfavourable conditions for osseointegration, as gaps between the implant and the bone (Strnad et al, 2003). Bioinert titanium allows penetration of fibrous tissue into the interface implant/bone, and promotes instability or migration of implants towards the spinal canal in conditions requiring spondylosurgery. However, a firm interaction between the calcium-phosphate layer of the implant and the surrounding bone forms immediately after application if bioactive titanium with technological

Strength parameters and bioactivity would be expected to improve conditions for osseointegration in the intervertebral space, as compared to implants generated from bioinert materials and glass-ceramic. Therefore, this type of material appears to be optimal for the development of a new implant for PLIF. Based on our experiences with the glassceramic BAS-O, we designed a new implant model constructed from this material. Due to different properties of these two materials (glass-ceramic/biotitanium), we modified the shape of the implant, and we designed new application instrumentation. The basic model was the shape of skewed prism (4o) (20 mm long, 8 mm wide, with graduated high 6, 8 and 10 mm). The implant was equipped with two pairs of projections or winglets (2 mm high) on the opposite sides of the prism. The compression and bending load of our original model for PLIF was virtually mathematically tested using computer technology in cooperation with ČVUT Prague. These tests showed that the shape of the skewed prism with winglets can theoretically ensure the restoration of the anatomy of the operated segment of lumbar spine without a risk of a plunge into the adjacent vertebral bodies both during compression

Based on these mathematical analyses, we maintained the basic shape of the implant with the above mentioned parameters. The higher strength of the material allowed us to design simplified application instrumentation. We used a thread in the implant body instead of the Teflon-coated fork used in the implant BAS-O. Due to its strength, no opposite space dilatation was necessary before the application as a result of the bioactive titanium implant, and no risk of damage of the implant shape by metal loaders was detected. Therefore, the handling of the implant during an intervention is easy and safe. The shape of the implant ensured good restoration of the anatomy of the operated area (restoration of the interbody space and its stability) with minimal risk of implant plunge into the adjacent vertebral bodies, as demonstrated by imaging investigations. Other benefits of the new implant

modification according to LASAK is used, which ultimately eliminates this risk.

and flexion and without a risk of its damage (Figure 6).

included higher strength and shape variability.

(MPa) 240–680 200\* 170–218\*

Titanium Bone Glass-ceramic

across vertebral bodies occurred resulting from the construction with retention winglets and the chemical bond (Figure 5).

Fig. 5. Slide progression at L4/5 during overload of glass-ceramic implants in 2nd grade instability according to Meyerding.

We also added transpedicular fixation of the affected segment in case a patient experienced clinical impairment(s) due to implant damage and instability progression. We did not observe implant damage in the fixed segments in this study; however, we stopped using the stand alone technique with the glass-ceramic implant for PLIF after this experience. Unfortunately, we failed to directly demonstrate osseoconductive properties of the glassceramic implant BAS-0 for PLIF that was associated with fusion of the adjacent vertebral bodies by migrating bone tissue along the glass-ceramic body from 1994 to 1999.

#### **2.5 Experimental development of bioactive titanium in forms by LASAK**

The LASAK Company developed bioactive titanium with original surface modification at the end of the 1990s. Due to the limitations of the glass-ceramic implant mentioned above, we have been developing a new type of implant combining bioactive properties and higher mechanical resistance in cooperation with LASAK Company since 1998. Characteristics of this material (higher strength, bioactivity) have provided optimal implant characteristics for PLIF (Yan, 1997; Strnad, 2010). The material used for this implant is technically pure titanium (grade 3) which is dedicated for surgical implants (Regulation ISO 5832-2:1993(E): Implants for surgery, ISO 5835-2). To ensure bioactivity of this material, the implant surface is chemically modified by LASAK technology (Adjudication on Permission to Use a Medical Device No. 82/125/00-IIB by State Institute for Drugs Control of the Ministry of Health of the Czech Republic). Mechanical properties of this material are identical to pure titanium, and its strength and fracture persistence are several times better than characteristics of the bone tissue and the glass-ceramic material (see Table 3).

across vertebral bodies occurred resulting from the construction with retention winglets and

Fig. 5. Slide progression at L4/5 during overload of glass-ceramic implants in 2nd grade

bodies by migrating bone tissue along the glass-ceramic body from 1994 to 1999.

**2.5 Experimental development of bioactive titanium in forms by LASAK**

bone tissue and the glass-ceramic material (see Table 3).

We also added transpedicular fixation of the affected segment in case a patient experienced clinical impairment(s) due to implant damage and instability progression. We did not observe implant damage in the fixed segments in this study; however, we stopped using the stand alone technique with the glass-ceramic implant for PLIF after this experience. Unfortunately, we failed to directly demonstrate osseoconductive properties of the glassceramic implant BAS-0 for PLIF that was associated with fusion of the adjacent vertebral

The LASAK Company developed bioactive titanium with original surface modification at the end of the 1990s. Due to the limitations of the glass-ceramic implant mentioned above, we have been developing a new type of implant combining bioactive properties and higher mechanical resistance in cooperation with LASAK Company since 1998. Characteristics of this material (higher strength, bioactivity) have provided optimal implant characteristics for PLIF (Yan, 1997; Strnad, 2010). The material used for this implant is technically pure titanium (grade 3) which is dedicated for surgical implants (Regulation ISO 5832-2:1993(E): Implants for surgery, ISO 5835-2). To ensure bioactivity of this material, the implant surface is chemically modified by LASAK technology (Adjudication on Permission to Use a Medical Device No. 82/125/00-IIB by State Institute for Drugs Control of the Ministry of Health of the Czech Republic). Mechanical properties of this material are identical to pure titanium, and its strength and fracture persistence are several times better than characteristics of the

the chemical bond (Figure 5).

instability according to Meyerding.

Table 3. Comparison of mechanical properties of titanium, bone and glass-ceramic BAS-0.

The mechanically and chemically modified surface of the bioactive titanium by LASAK technology is able to induce the production of calcium-phosphate (apatite), and this compound arises from the interaction between the surface of the material and body fluid within hours to days. The chemical and crystallographical properties of this mineral are nearly identical with the bone apatite. Experimental studies with bioactive and bioinert titanium demonstrated that titanium with a bioactive surface better tolerates unfavourable conditions for osseointegration, as gaps between the implant and the bone (Strnad et al, 2003). Bioinert titanium allows penetration of fibrous tissue into the interface implant/bone, and promotes instability or migration of implants towards the spinal canal in conditions requiring spondylosurgery. However, a firm interaction between the calcium-phosphate layer of the implant and the surrounding bone forms immediately after application if bioactive titanium with technological modification according to LASAK is used, which ultimately eliminates this risk.

Strength parameters and bioactivity would be expected to improve conditions for osseointegration in the intervertebral space, as compared to implants generated from bioinert materials and glass-ceramic. Therefore, this type of material appears to be optimal for the development of a new implant for PLIF. Based on our experiences with the glassceramic BAS-O, we designed a new implant model constructed from this material. Due to different properties of these two materials (glass-ceramic/biotitanium), we modified the shape of the implant, and we designed new application instrumentation. The basic model was the shape of skewed prism (4o) (20 mm long, 8 mm wide, with graduated high 6, 8 and 10 mm). The implant was equipped with two pairs of projections or winglets (2 mm high) on the opposite sides of the prism. The compression and bending load of our original model for PLIF was virtually mathematically tested using computer technology in cooperation with ČVUT Prague. These tests showed that the shape of the skewed prism with winglets can theoretically ensure the restoration of the anatomy of the operated segment of lumbar spine without a risk of a plunge into the adjacent vertebral bodies both during compression and flexion and without a risk of its damage (Figure 6).

Based on these mathematical analyses, we maintained the basic shape of the implant with the above mentioned parameters. The higher strength of the material allowed us to design simplified application instrumentation. We used a thread in the implant body instead of the Teflon-coated fork used in the implant BAS-O. Due to its strength, no opposite space dilatation was necessary before the application as a result of the bioactive titanium implant, and no risk of damage of the implant shape by metal loaders was detected. Therefore, the handling of the implant during an intervention is easy and safe. The shape of the implant ensured good restoration of the anatomy of the operated area (restoration of the interbody space and its stability) with minimal risk of implant plunge into the adjacent vertebral bodies, as demonstrated by imaging investigations. Other benefits of the new implant included higher strength and shape variability.

Development and Clinical Evaluation of Bioactive

implantation].

original magnification - 200x).

**2.6 Implaspin in clinical practice**

winglets into the adjacent vertebral bodies (figure 7).

Implant for Interbody Fusion in the Treatment of Degenerative Lumbar Spine Disease 211

We removed the whole motion segment with implants from cadavers after experimental operations, and we assessed their localization and the degree of their damage by X-ray and CT scans (Filip et al, 2001). Both investigations showed proper localization of the implants in the intervertebral spaces without any contact with the spinal canal or perforation of the

Additionally, their shape and surface were not damaged by the new type of instrumentation. Therefore, we assumed that these findings would transfer from experimental studies into clinical practice. However, we were not able to verify the osseoconductive properties of the implant surface in the cadavers. A perfect contact was observed between the surrounding bone tissue resulting from the simple application in cadavers, which was a good precondition for supporting osseointegration in the interbody space via osteoblasts´ migration along its surface. Thus, we verified the osseoconductive properties of the BIO surface of the implant in an animal model (Strnad, 2008). The implant surface in the direct contact with newly produced bone tissue yielded the following values [BIC (%) = 48,5 ± 2,9, 66,0 ± 7,4 and 90,6± 7,0, respectively, two, five and twelve weeks after

Fig. 8. Histological section of the interface of newly formed bone tissue on the BIO surface of

Encouraged by these experimental results, we began to use this type of implant in clinical practice in indications for PLIF instead of the glass-ceramic implant since 2002 (Figure 9).

The operation technique PLIF was identical to the operation technique used in cadavers (Filip et al, 2010). For example, we decompressed the nervous structures through posterior median line approach, and we then radically removed the degenerated intervertebral disc under the control of the operation microscope. Afterwards, we removed the surfaces of the adjacent vertebral bodies, and we then inserted the bioactive titanium implant using the innovated instrumentation (Figure 10). Finally, we added transpedicular fixation of the

the titanium implant twelve weeks after implantation. This figure illustrates the osseoconductive properties of the surface (optical microscope, toluidine blue staining,

whole segment (Synthes, Signus, Easy spine, etc.) (Figure 11).

Fig. 6. Illustration of the mathematical testing of the implant model.

Fig. 7. Implaspin in the intersomatic space of a cadaver by CT (2001).

Fig. 6. Illustration of the mathematical testing of the implant model.

Fig. 7. Implaspin in the intersomatic space of a cadaver by CT (2001).

We removed the whole motion segment with implants from cadavers after experimental operations, and we assessed their localization and the degree of their damage by X-ray and CT scans (Filip et al, 2001). Both investigations showed proper localization of the implants in the intervertebral spaces without any contact with the spinal canal or perforation of the winglets into the adjacent vertebral bodies (figure 7).

Additionally, their shape and surface were not damaged by the new type of instrumentation. Therefore, we assumed that these findings would transfer from experimental studies into clinical practice. However, we were not able to verify the osseoconductive properties of the implant surface in the cadavers. A perfect contact was observed between the surrounding bone tissue resulting from the simple application in cadavers, which was a good precondition for supporting osseointegration in the interbody space via osteoblasts´ migration along its surface. Thus, we verified the osseoconductive properties of the BIO surface of the implant in an animal model (Strnad, 2008). The implant surface in the direct contact with newly produced bone tissue yielded the following values [BIC (%) = 48,5 ± 2,9, 66,0 ± 7,4 and 90,6± 7,0, respectively, two, five and twelve weeks after implantation].

Fig. 8. Histological section of the interface of newly formed bone tissue on the BIO surface of the titanium implant twelve weeks after implantation. This figure illustrates the osseoconductive properties of the surface (optical microscope, toluidine blue staining, original magnification - 200x).

#### **2.6 Implaspin in clinical practice**

Encouraged by these experimental results, we began to use this type of implant in clinical practice in indications for PLIF instead of the glass-ceramic implant since 2002 (Figure 9).

The operation technique PLIF was identical to the operation technique used in cadavers (Filip et al, 2010). For example, we decompressed the nervous structures through posterior median line approach, and we then radically removed the degenerated intervertebral disc under the control of the operation microscope. Afterwards, we removed the surfaces of the adjacent vertebral bodies, and we then inserted the bioactive titanium implant using the innovated instrumentation (Figure 10). Finally, we added transpedicular fixation of the whole segment (Synthes, Signus, Easy spine, etc.) (Figure 11).

Development and Clinical Evaluation of Bioactive

angle 4% to maintain lordosis in the lumbar area (Figure 12).

Fig. 12. Fixation L4/5 (Implaspin plus transpedicular screws Signus).

inside or around the implants.

According to the experimental studies, tight contact with the surrounding bone tissue was necessary to activate the bioactivity of the surface. This contact was ensured by the shape of the implant and the winglets that penetrated into the spongious bone tissue of the adjacent vertebral bodies, and was the precondition for migration of the osteoblasts along the implant body resulting in the formation of a junction of the adjacent vertebral bodies by bone tissue without the need to sample bone grafts or to add supporting synthetic materials

In 2002 to 2007, operations were performed on 57 patients using the bioactive implant Implaspin in the Neurosurgery Clinic of the Faculty Hospital in Ostrava and in the Neurosurgery Department of Tomáš Baťa´s Regional Hospital in Zlín. We assessed a population of 25 patients with follow-up examinations conducted two or more years following surgery, according to the clinical condition. The follow-ups were also based on the generally used score system ODI and imaging methods (X-ray, CT, MRI) that occurred three, six, twelve and 24 months after surgery. During the follow-ups, we examined the patients for signs of implant damage, instability of the operated segment, and signs of supposed osteoblastic activity of the bioactive surface of the implant on the scans. Results of the ODI questionnaire showed that with Implaspin, our success rate improved by 1 degree (59%–40%), or we stabilized the clinical condition of the majority of the patients long-term (2

Implant for Interbody Fusion in the Treatment of Degenerative Lumbar Spine Disease 213

the correct position with winglet penetration into the spongious tissue of the adjacent vertebral bodies. We have selected the size empirically according to the extent of osteochondrosis of the affected disc and the degenerative lesions of the surrounding tissues on scans (X-ray, CT, MRI) during the intervention. In the majority of cases, we used implants (8 or 10 mm high) with

Fig. 9. Implant from bioactive titanium – Implaspin (2002).

Fig. 10. Insertion of Implaspin into the interbody space.

Fig. 11. Transpedicular application of screws (SIGNUS)

To date, we have not observed any complications associated with the implant application into the interbody space. According to the postoperative scans, the implant was always placed in

Fig. 9. Implant from bioactive titanium – Implaspin (2002).

Fig. 10. Insertion of Implaspin into the interbody space.

Fig. 11. Transpedicular application of screws (SIGNUS)

To date, we have not observed any complications associated with the implant application into the interbody space. According to the postoperative scans, the implant was always placed in the correct position with winglet penetration into the spongious tissue of the adjacent vertebral bodies. We have selected the size empirically according to the extent of osteochondrosis of the affected disc and the degenerative lesions of the surrounding tissues on scans (X-ray, CT, MRI) during the intervention. In the majority of cases, we used implants (8 or 10 mm high) with angle 4% to maintain lordosis in the lumbar area (Figure 12).

Fig. 12. Fixation L4/5 (Implaspin plus transpedicular screws Signus).

According to the experimental studies, tight contact with the surrounding bone tissue was necessary to activate the bioactivity of the surface. This contact was ensured by the shape of the implant and the winglets that penetrated into the spongious bone tissue of the adjacent vertebral bodies, and was the precondition for migration of the osteoblasts along the implant body resulting in the formation of a junction of the adjacent vertebral bodies by bone tissue without the need to sample bone grafts or to add supporting synthetic materials inside or around the implants.

In 2002 to 2007, operations were performed on 57 patients using the bioactive implant Implaspin in the Neurosurgery Clinic of the Faculty Hospital in Ostrava and in the Neurosurgery Department of Tomáš Baťa´s Regional Hospital in Zlín. We assessed a population of 25 patients with follow-up examinations conducted two or more years following surgery, according to the clinical condition. The follow-ups were also based on the generally used score system ODI and imaging methods (X-ray, CT, MRI) that occurred three, six, twelve and 24 months after surgery. During the follow-ups, we examined the patients for signs of implant damage, instability of the operated segment, and signs of supposed osteoblastic activity of the bioactive surface of the implant on the scans. Results of the ODI questionnaire showed that with Implaspin, our success rate improved by 1 degree (59%–40%), or we stabilized the clinical condition of the majority of the patients long-term (2

Development and Clinical Evaluation of Bioactive

body of the L3 (white colour).

Implant for Interbody Fusion in the Treatment of Degenerative Lumbar Spine Disease 215

with Implaspin. The study was conducted before the surgery as well as two and six months after the intervention, and we assessed the anatomical changes and metabolic activity at the location where the implants were applied by using the combined scans. The investigation provided preoperative signs of instability localized to the affected space in the area of the disc in all four patients. We detected a hyperintense signal at the operated segment two to three months after the surgery, which was a sign of osteoblast activity on the surface of the implant. We also observed a decrease of this activity (hypointense signal) six months after the surgery as well as a change on the surface of the implant using the combined CT scans.

Fig. 13. Implants applied into the spaces L3/4 and L4/5 on SPECT CT. The figure shows the surface of the implant with the bone tissue (grey-black colour) and the titanium screw in the

Fig. 14. Implants on a SPECT-CT scan. The bone growth at the border of bone tissue (grey)

and Implaspin (white) is visible in the space L4/5.

and more years), which corresponds to results of other clinics using other implant types (Bessho et al, 1997; Brantigan et al 1993; Brayan et al, 2002; Bienik and Swiecki, 1991; Ciappetta et al, 1997; see Table 4).

Table 4. Mean Oswestry score values before surgery and at regular visits (FBSS – failed back surgery syndrome; IS – isthmic spondylolisthesis; DI – degenerative instability).

The assessment of the implant position on scans (X-ray, CT, MRI) at postoperative visits demonstrated no signs of implant damage or implant migration out of the intersomatic space. These investigations have not yet shown any signs of instability of the operated segment (i.e., formation of new osteophytes, progression of hypertrophy of the articular facets, and migration of the implant at the site of application). We observed one severe complication in the population which was caused by an inaccurate application of the transpedicular screws. The wound healed in this patient, and the neurological findings stabilized after removal of the screws. The stabilization of the condition may be supported by the implant shape and the winglets which prevented instability even after the removal of the transpedicular screws. This finding was confirmed by the imaging investigations. Based on the clinical condition and the absence of instability signs on imaging investigations, we concluded that the formation of bone fusion was due to osteopblasts´ migration along the bioactive of Implaspin surface.

#### **2.7 Assessment of bioactivity of the implant using SPECT-CT**