
 the unique anatomy and structural support in the thoracic spine create challenges for practitioners attempting surgery in the region .
due to the inherent rigidity of the region granted by the rib cage , spondylotic changes are significantly less common than in the cervical and lumbar spine .
the most common pathologies in the thoracic spine requiring corpectomy are tumors , trauma , and infection [ 24 ] .
treating these pathologies can require significant anterior reconstruction , made challenging due to the ribs and other adjacent critical structures including the lungs , pleura , aorta , and mediastinum .
obtaining adequate exposure for corpectomy is critical due to the relative intolerance of the thoracic spinal cord to manipulation and mobilization [ 1 , 3 , 6 ] .
additionally , the numerous comorbidities usually present in these patients often preclude the systemic stress of open surgery .  
minimally invasive techniques in the cervical and lumbar spine have been clearly demonstrated to lower surgical blood loss , pain , improve wound healing , and shorten hospital stay [ 810 ] . in the thoracic spine , their advent is allowing surgeons to consider treatment for patients who previously would have been relegated to bracing and palliative pain relief due to risks of open surgery .
reports have emerged describing minimally invasive variants to nearly every open thoracic approach to corpectomy [ 3 , 1115 ] .
we present here the treatment options described in the literature , with an emphasis on specific advantages , disadvantages , and surgical nuance ( table 1 ) .
  thoracotomy to access the anterior thoracic spine was first described in the 1950s . used initially primarily in the treatment of thoracic disc herniation , it found significant popularity in the 1970s and 1980s in response to the disappointing results for laminectomy for decompression and discectomy , due to poor outcomes associated with manipulation of the thoracic spinal cord [ 1 , 6 , 1719 ] .
surgery involves placing patients in the lateral position , making a lengthy incision laterally along the associated rib , performing thoracotomy , and retracting the lung anteriorly .
the parietal pleura is then split close to the rib head , allowing visualization of the costovertebral joint .
the costovertebral ligaments and rib head are removed creating anterolateral visualization of the vertebral body , allowing discectomy and corpectomy .
closure includes leaving a chest tube , typically for three days of recumbent drainage [ 1 , 17 , 18 ] .
while early reports showed good associated outcomes , surgical morbidity quickly prompted surgeons to explore other approaches [ 2 , 5 ] .
approach related complications include pulmonary contusion , atelectasis , pleural effusion , chylothorax , and hemothorax [ 5 , 7 ]
.   video - assisted thoracoscopy has allowed surgeons to avoid much of the incision- and dissection - related morbidity associated with thoracotomy [ 11 , 20 , 21 ] .
similar to thoracotomy , the patient is intubated with a double endotracheal tube with deflation of the ipsilateral lung , in a lateral position .
four thoracoscopic ports are placed via 2-centimeter incisions over the intercostal space , spaced widely throughout the chest , centered over the level of interest .
the thoracoscope is typically a 10  mm fixed endoscope , with angled options available . because the working distance to the spine ranges from 14 to 30  mm ,
specific adaptations of common surgical instruments are required , including drills , soft tissue dissectors , hemostatic agents , and spinal tools . similarly to open thoracotomy ,
the appropriate costovertebral joint is identified , with subsequent opening of the pleura , removal of the rib head , discectomy , corpectomy , and reconstruction [ 11 , 22 ] closure consists of copious irrigation , inspection of the ipsilateral lung , followed by placement of chest tubes [ 11 , 2325 ] .  
yanni et al . recently described a variation of this approach , focused on alleviating the challenge of manually holding the endoscope .
they conducted a similar exposure with port placement , but once the exposure was complete , they utilized one of the ports to place a tubular retractor against the spine , under direct visualization with the endoscope .
this allowed them direct lateral exposure comparable to the technique commonly used in the lumbar spine .  
the advent of thoracoscopy has allowed spine surgeons to reconsider the anterolateral approach to the thoracic spine .
existing series suggest that the technique is feasible , and it appears to be as successful as open surgery in allowing decompression and instrumentation [ 21 , 23 ] .
anterior visualization allows surgeons to perform complete corpectomy , visualizing the posterior longitudinal ligament , the entire anterior spinal cord , ipsilateral pedicle and foramen .
the exposure allows a wide variety of grafts to be inserted , with the benefit of screw - plate fixation . above t11 ,
the surgeon can choose a right- or left - sided approach based on specific patient anatomy , to concentrate on visualization of affected critical structures including the azygos vein , aorta , thoracic duct , and artery of adamkiewicz .
t11 and t12 should be approached from the left to avoid the liver , and require caudal retraction of the hemidiaphragm [ 1 , 11 ] .  
a steep learning curve has been described for surgeons beginning to undertake the technique [ 11 , 27 ] .
intraoperative utilization of the multiple ports along with the endoscope can be facilitated by the use of fixed table based systems , but often can require significant assistant support .
introduction of a tubular retraction system may overcome this challenge , however [ 11 , 26 ] .
working in a ventral - to - dorsal direction limits visualization of the posterior longitudinal ligament and thecal sac , and forces the surgeon to continuously estimate the distance between the working instrument and the spinal cord .
additionally , patients with significant lung pathology limiting single lung ventilation or pleural adhesions are contraindicated from thoracoscopy .  
despite the disadvantages , thoracoscopy has been shown to reduce the incidence of pulmonary morbidity , intercostal neuralgia , and shoulder girdle dysfunction versus open thoracotomy [ 8 , 23 , 28 ] .
patients suffer significantly less pain and incisional morbidity in thoracoscopic cases , with a lower rate of postthoracotomy pain syndrome .
overall complication rates have been quoted to be significantly lower than those reported for thoracotomy , which ranges from 9 to 11.5% incidence of major complication [ 5 , 7 ] . nevertheless , the rate of complications including atelectasis , pneumothorax , hemothorax , and pleural effusion are still considerable , ranging from 14.1 to 29.4% [ 11 , 29 , 30 ] .
additionally , the burden of chest tube placement can still cause significant pain and limitation of postoperative patient mobilization .
  mccormick and moskovitch described the retropleural approach to the anterolateral thoracic spine in the early 1990s as a method to avoid the morbidity associated with thoracotomy [ 31 , 32 ] .
employing a retropleural approach allows for a ventral decompression without requiring entrance into the pleural cavity .
mccormick 's report described 15 patients undergoing treatment ranging from discectomy to two - level corpectomy . in his surgical technique
, a 12  cm incision is performed from the posterior axillary line to 4  cm lateral of midline , with exposure and removal of 810  cm of the rib . the endothoracic fascia is incised and dissected off of the parietal pleura , leaving a plane with only slight areolar tissue , which is dissected until the endothoracic fascia is opened over the rib head .
the costovertebral ligaments and proximal rib head are taken down to expose the vertebral body , facilitating corpectomy and reconstruction .
pleural tears are repaired primarily , and a chest tube is not required unless a significant tear is encountered . in the series of fifteen patients , adequate
decompression and reconstruction were performed in all cases , although four patients did require chest tube placement .  
the significant exposure - related morbidity of this approach has limited its appeal and usage .
recent descriptions of a minimally invasive retropleural approach , however , have reopened the anterolateral corridor for corpectomy .
he made a 5 - 6  cm incision laterally , removed an 810  cm segment of the rib , and dissected between the endothoracic fascia and pleura towards the rib head .
four out of thirty - eight patients ultimately required chest tube drainage , and all patients had adequate decompression and insertion of instrumentation .  
uribe et al . furthered this approach by describing a tubular retractor based retropleural approach in a cadaveric series and a small patient series . by using tubular dilators to perform the retropleural dissection
they perform a 6  cm incision , remove 5  cm of underlying rib , and dissect free the retropleural plane towards the ribhead .
corpectomy is performed in a pedicle - to - pedicle fashion , with an anterior shell of bone and the all ( anterior longitudinal ligament ) preserved to protect thoracic contents .
reconstruction is performed with an expandable cage and autograft , with ventrolateral screw - plate fixation .
a midline posterior incision is then performed , and posterior percutaneous screws are placed for reinforcement .
one of their four reported cases required chest tube placement , and there were no perioperative complications .
kasliwal and deutsch also described a similar approach for thoracic discectomy , utilizing a 2  cm incision to place an expandable tubular retraction system through a retropleural corridor in 7 patients . a case report from keshavarzi et al .
advantages of this approach include excellent anterior column reconstruction and little risk to the spinal cord
. however , a significant challenge , particularly at the thoracolumbar junction , is manipulation of the diaphragm .
dakwar and colleagues performed an anatomic study on 9 cadavers , examining the variants of diaphragmatic insertion points .
they noted that while the diaphragmatic insertion is released with partial rib resection and mobilization of the pleura , by pursuing tubular dilation , the fibers of the diaphragm are not being cut .
however , other challenges associated with the retropleural approach include risk to the lumbar plexus , the mechanical difficulty of decompressing the canal from this angle , and risk to the segmental arteries .

 the lateral extracavitary approach was first described by capener in 1954 , and modified by larson et al . [ 37 , 38 ] .
it has since been modified and popularized by numerous modern spine surgeons [ 3942 ] .
it provides a posterolateral , oblique approach to the vertebral body and spinal canal without entering the pleural cavity or retropleural dissection .
the common description of the procedure describes a hockey stick incision , with the short limb extending 8  cm laterally of midline , in either prone or 3/4 prone position .
the thoracodorsal fascia is exposed and the erector spinae muscles are elevated off the ribs . the rib is dissected free , cut 610  cm laterally , and removed after disarticulation of the costovertebral joint . with minimal retraction , discectomy and corpectomy
can be performed under direct visualization , although the contralateral edge of the vertebral body and pedicle are not visualized
. a wide variety of grafts can be introduced , and standard posterior pedicle screw / rod fixation achieved .
a chest tube is only required in case of pleural violation [ 3844 ] .   given the extensive muscle dissection required for the lateral extracavitary approach , the application of mis techniques may provide distinct advantages .
the first description of minimally invasive posterolateral corpectomy was published by kim et al . in a series of cadaveric procedures and a small series of patients .
they started with a four cm long incision four cm laterally from midline . a k wire ( kirschner wire )
was docked on the ipsilateral facet near the pedicle , followed by dilators and an expandable tubular retractor .
the proximal rib was removed , followed by removal of the costovertebral ligaments , rib head , intercostal vessels , and ipsilateral pedicle .
discectomy and corpectomy were performed with preservation of the ventral body , all , and contralateral vertebral margins .
titanium mesh , autograft , or expandable cages were used for reconstruction , and vertebral body screws and rods were sometimes used for supplementation .
an average of 79.2% corpectomy was performed in the cadaveric cases , although the contralateral side was unable to be decompressed .
average estimated blood loss was 495  ml , operating room time was 5.8 hours , and hospital stay was 4.7 days in the clinical series .
images from a representative case and cadaveric surgery are shown here ( figures 1 and 2 ) .  
khoo et al . described their experience with removal of thoracic disks and interbody fusion utilizing a similar minimally invasive posterolateral thoracic approach in 13 patients , and compared the cohort to patients undergoing traditional transthoracic surgery .
they utilized a 2  cm incision and docked the k wire at the junction of the ipsilateral transverse process and pedicle .
they performed diskectomy without thecal sac retraction by rotating the bed in an oblique fashion .
their one - year outcomes were equivalent to open surgery , and most patient metrics favored the minimally invasive approach .
described their outcomes in minimally invasive posterolateral corpectomy in a recent manuscript outlining a cadaveric series and surgical management of three patients .
they had appropriate decompression and instrumentation in all three patients , estimated blood loss of 517  ml , and average operating room time of 4.75 hours .
they were able to achieve a mean of 72% vertebral body resection in the cadaveric series , without contralateral decompression .
they introduced a first tube to perform a costotransversectomy and corpectomy on the more affected side .
the lateral extracavitary approach is one of the most widely validated approaches for corpectomy in the thoracic spine .
decompression and neurologic outcomes are excellent , and complications are typically minor and self - limited [ 3941 ] .
nevertheless , muscle - dissection - related morbidity is severe , and the substantial tissue dissection and blood loss place severe systemic stress on the patient .
one series described an average of 3100  ml of blood loss and 7.74 hours per case , although these numbers may have been exaggerated by a small number of complicated cases .
in contrast , minimally invasive posterolateral corpectomy appears to provide adequate decompression and instrumentation , with less blood loss and operative time .
an important advantage of this approach as opposed to midline posterior approaches is preservation of the midline posterior tension band .
it also allows the ability to create longer constructs by placing percutaneous screws above and below the level of corpectomy .
  the transpedicular approach has been extensively utilized in patients whose comorbidities limit transthoracic and lateral extracavitary approaches [ 4751 ] .
outcomes appear favorable when compared with other open techniques , and the technique has been described for a wide range of pathology [ 47 , 50 , 5254 ] .
surgery consists of midline incision two levels above and below the level of pathology , with dissection to the lateral edge of the transverse processes .
the posterior elements are removed , along with the bilateral facets , demonstrating the thecal sac and pedicles .
the pedicles are then taken down , exposing the vertebral body for corpectomy and adjacent level discectomy .
multiple techniques have been described for placement of an expandable cages in the transpedicular approach : including thecal sac mobilization , rib head osteotomy , rib head disarticulation , and trap - door rib head osteotomy , with thinning of the rib to allow greenstick fracture and displacement with subsequent displacement [ 47 , 52 , 53 ] .  
deutsch et al . performed minimally invasive transpedicular corpectomy in 8 patients with metastatic tumors .
they focused on patients older than 68 years of age , who were deemed to be poor candidates for open surgery , with less than one year of life expectancy , but significant neurologic deficit .
they first performed a 3  cm incision above the transverse process of the more affected side .
they used sequential dilators and an expandable tubular retractor to visualize the posterior elements , then took down the ipsilateral transverse process , proximal lamina , and pedicle .
they did not instrument as they did not feel that stability had been compromised , and given the palliative nature of the procedures .  
they describe the procedure for 8 patients and compare it to a similar open cohort .
they perform a midline incision two levels above and below the level of interest , preserving the fascia .
a midline fascial opening is performed over the level of interest , and an expandable tubular retraction system is placed .
the posterior elements are removed , followed by removal of the pedicles and adjacent level diskectomy .
they comment that removing the tubular retractor and placing a cerebellar helps to insert the cage , along with rotating the cage while inserting it between the vertebral bodies .
, they showed lower blood loss , similar operative time , and similar complication rates .
  the varying approach corridors to the thoracic spine offer different advantages and drawbacks ( figure 5 ) .
the anterior ( transthoracic and thoracoscopic ) approaches allows the broadest decompression of the vertebral body with the ability to visualize the entire anterior thecal sac , but presents complications associated with entering the thorax , and risks related to working adjacent to the aorta and azygos vein [ 5 , 23 , 29 , 55 ] . working in a ventral - to - dorsal direction forces the surgeon to constantly estimate his distance to the thecal sac .
the retropleural approach offers a similar view to thoracoscopy without entering the pleura , but even the existing minimally invasive descriptions require at least a 68  cm incision , substantial rib resection , and an extensive retropleural dissection [ 12 , 33 ] .
this dissection is technically demanding , results in an increased risk of pleural violation and chest tube placement , and may be mechanically more awkward than the transthoracic approaches .
the posterolateral approach allows surgeons to use a more familiar surgical angle ( figure 4 ) .
the minimally invasive variant spares much of the muscle dissection classically associated with the lateral extracavitary approach , decreasing blood loss , and surgical time [ 3 , 45 ] .
nevertheless , the unilateral approach likely limits the surgeon to a maximum of 80% corpectomy , and the contralateral pedicle , pll , and ventral thecal sac can not be clearly visualized in cadaveric studies . also ,
placement of percutaneous screws is typically required for reinforcement , which requires a second , parallel incision .
this technique may also require a significant learning curve for the surgeon [ 3 , 45 ] .
the midline transpedicular approaches use a familiar midline trajectory , with either a miniopen approach through midline fascial opening , or bilateral expandable tubular retractors [ 1315 ] .
this approach allows bilateral decompression , cage reconstruction , and posterior instrumentation through a single exposure .
nevertheless , placement of the cage still requires either significant manipulation of the rib head or thecal sac , and working with the spinal cord directly between the surgeon and the vertebral body poses clear risks for injury [ 15 , 49 ] .
anterior and anterolateral approaches will dictate anterior only instrumentation systems , while posterolateral and posterior approaches better allow for posterior pedicle screws in the same position , with or without anterior cage reconstruction .
anterior approaches allow plating for stabilization over a wide variety of grafts , ranging from autograft to cages [ 11 , 21 ] .
the posterolateral approach allows for multiple types of anterior grafts as well , but supporting plate / screw systems are limited to a unilateral lateral orientation . as a result , most surgeons are performing a second incision for placement of percutaneous screws [ 3 , 46 ] .
the midline posterior approach is secured with percutaneous screws , with or without expandable cage grafting . in the posterior approach , supporting plating can not be performed over the graft .
studies have demonstrated that anterior - only constructs for thoracic reconstruction are feasible and appear at least as efficacious as posterior only constructs , although they may be less biomechanically sound [ 56 , 57 ] .
anterior reconstruction has also been suggested to carry the advantage of correcting kyphosis and preventing secondary kyphosis [ 11 , 57 , 58 ] .  
descriptions of minimally invasive techniques for corpectomy are currently very limited by small sample size and limited followup .
while some of the series have made early attempts to compare outcomes to the more established open procedures , comparisons are made only on the basis of intraoperative data such as blood loss and feasibility of decompression and instrumentation .
long - term instrumentation outcomes , fusion rates , and patient morbidity and mortality data are still lacking at this time .
thus , continued followup will be required before these minimally invasive techniques can be held in equipoise with established open procedures .
nevertheless , surgeons should be aware of these technical possibilities , and should consider their incorporation in modern surgical practice .
  comprehensive discussion of emerging techniques in lumbar and thoracolumbar corpectomy would easily command an independent paper . nevertheless , most emerging techniques in minimally invasive lumbar corpectomy utilize similar principals to the thoracic techniques , specifically blunt tubular muscle and plane splitting , to minimize blood loss and tissue trauma .
lateral and anterior techniques in the lumbar spine and thoracolumbar junction provide similar advantages for decompression and reconstruction .
we present an illustrative case of a 21-year - old male who suffered an l4 burst fracture and underwent mis lateral corpectomy and reconstruction ( figure 3 ) .
  minimally invasive approaches for corpectomy in the thoracic spine offer substantial exposure - related advantages compared to their open counterparts .
descriptions are new and will require larger series and greater long - term followup to become fully validated .
choice of exposure approach should be driven by a patient 's specific pathology , anatomy , and medical comorbidities .
 the rapid expansion of minimally invasive techniques for corpectomy in the thoracic spine provides promise to redefine treatment options in this region . 
 techniques have evolved permitting anterior , lateral , posterolateral , and midline posterior corpectomy in a minimally invasive fashion . 
 we review the numerous techniques that have been described , including thoracoscopy , tubular retraction , and various instrumentation techniques . 
 minimally invasive techniques are compared to their open predecessors from a technical and complication standpoint . 
 advantages and disadvantages of different approaches are also considered , with an emphasis on surgical strategies and nuance . 
1. Background
2. Transthoracic
3. Retropleural
4. Posterolateral
5. Posterior
6. Discussion
7. Lumbar and Thoracolumbar Corpectomy
8. Conclusion