as the cervical spine degenerates with age , there is increased risk of undesirable conditions such as displacement or degeneration of intervertebral disc , slackness of annulus fibrosis , osteophytosis of vertebral body and instability .
degenerative cervical disc may cause posterior neck pain , radiating pain on arm or shoulder , or cervical myelopathy .
anterior cervical discectomy and fusion ( acdf ) is a safe and standard operation for the treatment of degenerative cervical disc disease concerned with radiculopathy or myelopathy29 ) .
the main purposes of intervertebral cage are biomechanical support , restoration of disc height , maintaining of cervical lordosis and ideal osteointegration4,17,19 ) .
tricortical iliac crest autobone graft results in numerous complications including breaking of bone graft , collapsing , pseudoarthrosis , subsidence , angular deformation , protrusion of bone block , pain or bleeding of donor site and infection22,30,31 ) .
the most frequently donor site related complication is pain , and infection of harvest site could be a nettlesome problem23 ) . to solve these problems , various types of artificial cages providing immediate firmness without a plate system
a standard cage alone for acdf is an effective method to treat degenerative cervical disease23 ) .
short term clinical follow up data has been published less than 18 months after acdf with the polyetheretherketone ( peek ) cage . in the current study , we present a retrospective long term(mean period : 36 months ) study of thirty consecutive patients after acdf with solis cage with iliac autobone graft .
we collected information from charts of patients who visited our neurosurgical department from march 2006 to july 2008 , retrospectively . only patients with single level acdf without anterior cervical plate were eligible for the study , and thirty patients were selected ( male : 20 patients and female : 10 patients ) .
the mean age was 47.67.1 years ( range from 28 to 63 years old ) .
the patients who complained of radiculopathy were 21 , myelopathy were 2 and myeloradiculopathy were 7 patients .
mean follow - up period was 36.48.1 months ( ranged from 23 to 49 months ) .
a right side skin incision was done in all cases ; fluoroscopy was used to check the target level .
complete removal of the disc , lateral decompression and end plate flattening for maximal contact with cage was performed .
after selection of ideal trial size by using intraoperative fluoroscopy , harvested cancellous bone from the iliac crest filled in the hollow space of the cage .
finally , we checked that the radiopaque titanium spike was in an adequate location by fluoroscopy .
we used the japanese orthopedic association ( joa ) score for evaluation of myelopathy and visual analogue scale ( vas ) for radiating pain to estimate postoperative clinical outcome .
we assessed degree of pain relief between preoperative and postoperative ( last follow - up ) status by using two scoring systems .
three parameters were used to evaluate radiologic outcome : anterior disc height ( adh ) , interbody height ( ih ) and segmental interbody angle ( sia ) ( fig .
they were checked by plain x - ray on true lateral standing and classified into flexion , extension and neutral position view and 3d ct scan every 6 months after the surgery .
fusion was defined according to trabecular bony formation across interfaces between cage and endplates and bony bridge formation between endplates .
fusion was classified into 3 classifications : grade i , bridging bone partially filling the cage ; grade ii , bridging bone filling the cage ; and grade iii , bridging bone within and around the cage26 ) .
we collected information from charts of patients who visited our neurosurgical department from march 2006 to july 2008 , retrospectively . only patients with single level acdf without anterior cervical plate were eligible for the study , and thirty patients were selected ( male : 20 patients and female : 10 patients ) .
the mean age was 47.67.1 years ( range from 28 to 63 years old ) .
the patients who complained of radiculopathy were 21 , myelopathy were 2 and myeloradiculopathy were 7 patients .
mean follow - up period was 36.48.1 months ( ranged from 23 to 49 months ) .
a right side skin incision was done in all cases ; fluoroscopy was used to check the target level .
complete removal of the disc , lateral decompression and end plate flattening for maximal contact with cage was performed .
after selection of ideal trial size by using intraoperative fluoroscopy , harvested cancellous bone from the iliac crest filled in the hollow space of the cage .
finally , we checked that the radiopaque titanium spike was in an adequate location by fluoroscopy .
we used the japanese orthopedic association ( joa ) score for evaluation of myelopathy and visual analogue scale ( vas ) for radiating pain to estimate postoperative clinical outcome .
we assessed degree of pain relief between preoperative and postoperative ( last follow - up ) status by using two scoring systems .
three parameters were used to evaluate radiologic outcome : anterior disc height ( adh ) , interbody height ( ih ) and segmental interbody angle ( sia ) ( fig .
they were checked by plain x - ray on true lateral standing and classified into flexion , extension and neutral position view and 3d ct scan every 6 months after the surgery .
fusion was defined according to trabecular bony formation across interfaces between cage and endplates and bony bridge formation between endplates .
fusion was classified into 3 classifications : grade i , bridging bone partially filling the cage ; grade ii , bridging bone filling the cage ; and grade iii , bridging bone within and around the cage26 ) .
we compared vas for neck and arm between preoperative and last follow - up status , additionally , joa score was also used .
the mean vas for neck at the last exam was 2.50.8 and for arm was 3.21.1 ( p - value < 0.05 ) . in joa scoring assessment for 9 patients who were suffered from myelopathy ,
score improved from 11.12.9 at preoperative status to 14.52.6 at last exam(p - value < 0.05 ) . among 30 cases ,
22 patients were performed 3 dimensional ct scan ( 3d ct ) at last follow - up and remainders were checked by cervical dynamic plain x - ray .
radiological fusion rate was accomplished by 100% in selected group after 36 months after the surgery .
grade i fusion were found in 1 case , grade ii were in 3 cases and grade iii were in 18 cases on 3 dct scan . on plain x - ray ,
grade i fusion was no case , grade ii were 1 cases and grade iii were 7 cases ( fig .
the mean adh was 6.271.47 mm before the surgery and improved to 10.631.32 mm after the surgery ( p - value < 0.05 ) .
some degree of subsidence occurred at the last follow - up and final adh was 8.321.08mm(p - value < 0.05 ) . in same way ,
ih improved from 36.73.35 mm to 41.24.23mm(p - value < 0.05 ) and slightly decreased to 38.73.75 mm at the last exam(p - value < 0.05 ) ; however , we still achieved an increase of ih .
the mean preoperative sia was -3.353.44 and postoperative sia was -6.853.01 ( p - value < 0.05 ) . at the final exam ,
sia was -3.213.61 , not statistically different between postoperative sia and final exam sia ( p - value=0.813 ) .
we had no complications concerned with the surgery itself except one case of osteomyelitis . during the follow - up period
the superficial osteomyelitis of iliac bone donor site developed in 1 patient and a culture study of the infection site confirmed methicillin resistant staphylococcus aureus ( mrsa ) infection .
we performed local debridement and irrigation and treated with vancomycin intravenous treatment for 10 days .
we compared vas for neck and arm between preoperative and last follow - up status , additionally , joa score was also used .
the mean vas for neck at the last exam was 2.50.8 and for arm was 3.21.1 ( p - value < 0.05 ) . in joa scoring assessment for 9 patients who were suffered from myelopathy ,
score improved from 11.12.9 at preoperative status to 14.52.6 at last exam(p - value < 0.05 ) .
among 30 cases , 22 patients were performed 3 dimensional ct scan ( 3d ct ) at last follow - up and remainders were checked by cervical dynamic plain x - ray .
radiological fusion rate was accomplished by 100% in selected group after 36 months after the surgery .
grade i fusion were found in 1 case , grade ii were in 3 cases and grade iii were in 18 cases on 3 dct scan . on plain x - ray ,
grade i fusion was no case , grade ii were 1 cases and grade iii were 7 cases ( fig .
the mean adh was 6.271.47 mm before the surgery and improved to 10.631.32 mm after the surgery ( p - value < 0.05 ) .
some degree of subsidence occurred at the last follow - up and final adh was 8.321.08mm(p - value < 0.05 ) . in same way , ih improved from 36.73.35 mm to 41.24.23mm(p - value < 0.05 ) and slightly decreased to 38.73.75 mm at the last exam(p - value < 0.05 ) ; however , we still achieved an increase of ih .
the mean preoperative sia was -3.353.44 and postoperative sia was -6.853.01 ( p - value < 0.05 ) . at the final exam , sia was -3.213.61 , not statistically different between postoperative sia and final exam sia ( p - value=0.813 ) .
we had no complications concerned with the surgery itself except one case of osteomyelitis . during the follow - up period
the superficial osteomyelitis of iliac bone donor site developed in 1 patient and a culture study of the infection site confirmed methicillin resistant staphylococcus aureus ( mrsa ) infection .
we performed local debridement and irrigation and treated with vancomycin intravenous treatment for 10 days .
acdf has been performed for treatment of cervical degenerative disease and applied to infectious disease , cervical trauma and tumorous condition10 ) .
clinically , acdf with cage system began to be used regularly after clinical success of prospective research year 200013 ) .
single level acdf with autograft shows over 95% of fusion rate and approximately 80% of neurologic improvement15,24,25 ) .
some reports postulated there was no need for fusion after cervical discectomy and fusion should be considered only when instability occurs32 ) .
the limitation of a cage - alone procedure is weak initial mechanical stability and subsidence to endplate . a cervical anterior plate and screw system provides reduction of kyphotic angulation , prevention of implant migration , and increases fusion rate and durable fixation .
there may be , however , dysphasia due to plate and loosening , breakage of screw , plate migration and stress shield3,5,15 ) . innovative development of surgical instrument have reduced complications of the anterior plate system .
however , complications are still reported even though dynamic plate or self locking screw is suggested27 ) .
the peek cages are biologically inactive which means they do not induce a corrosive reaction and provide high versatility and good mechanical properties while causing minimal artifacts on mri and ct8,9 ) .
furthermore , excellent radiolucency gives information that surgeon can use to adjust the cage at an optimal location during operation , and bone fusion can be readily evaluated by plain x - ray11,34 ) .
titanium spikes on upper and bottom can make easy to anchor the vertebral body and provide immediate fixation , therefore cage migration is prevented .
elastic modulus is defined as the capacity of returning to its initial shape when load is removed .
lower elastic modulus shows a more natural characteristic with respect of bone material and lead to reduction of stress shield and increase bony fusion rate33 ) . among several cervical implants ,
high elastic mismatch between cage and bone can affect bone growth , promoting cortical thinning and subsidence in the case of metallic cages18,34 ) . generally , it is acceptable that bone fusion is achieved around 3 to 6 months after the surgery when using the peek cage .
cho et al . reported 100% of bone fusion in forty cases was achieved by using peek cage comparing 93.1% of bone fusion when using iliac tricortical bonegraft9 ) . in this study , we achieved 100% of fusion rate . only cancellous bone from the iliac crest might be great role of increase fusion rate and small size of patient group might be another cause .
the frequency of harvest autograft has decreased gradually , because of the relatively high rate of complications18 ) .
complications of tricortical iliac bone graft are various such as displacement bone graft , pseudoarthrosis , hematoma , pain , nerve injury and infection of donor site20 ) .
the incidence of related complications has been reported to be as high as 20% to 50%1,28 ) . moreover
, the low stabilization support of iliac crest grafts requires instrumentation with anterior plate34 ) . to reduce complications related with donor site ,
many types of material have been studied to substitute autologous bone , but none of these have showed advantage over autologous bone6,16 ) .
many complications related with iliac bone graft have been reduced with the use of cage system23 ) . in our patient group , the wound incision on the donor site was performed minimally and harvested only small amount of cancellous bone to minimize related complications .
numerous materials have been tried to substitute for autologous bone graft to reduce donor site related complications
. the ultimate material could provide immediate structural support and osteogenic intergration23 ) . since introduction of the cervical cage ,
numerous types of cage have been designed ; however subsidence of cage was reported frequently .
ha et al . studied subsidence in standalone solis cage and found 8.1% of cages had subsidence greater than 3mm12 ) .
noted that a decrease of disc height after operation did not affect clinical outcome20 ) .
lee et al . found that subsidence occurred on radiologic evaluation at last follow - up when they used dmb rather than autologous bone graft23 ) .
however , our data shows that at 36 months follow - up ih is still maintained compared to preoperative ih which implies autologous bone graft helps earlier bone fusion than dbm .
symptomatic adjacent segment problems occur at rate of 2.9% per year during ten years after acdf with autologous bone graft , the risk was lower in multilevel acdf than in single level , and the fusion rate declines as the number of involved levels increase11,14 ) . in our study
, we could not find degeneration of adjacent levels , but we concluded that this is due to small size of patient group . in current study , the complications of acdf with the peek cage did not include breaking , pseudoarthrosis , kyphotic angulation , protrusion of cage itself , and severe subsidence . however , one patient suffered from infection of donor site .
local heating and pus discharge occurred at right iliac crest where cancellous bone was harvested and culture study performed .
methicillin - resistant staphylococcus aureus ( mrsa ) was detected and vancomycin was prescribed for a week . to establish a role of the peek cage in acdf
the authors searched many articles to find a long term follow - up study for clinical outcome after acdf with peek cage longer than 36 months but we believe that this study is the first report for long term follow - up .
acdf with the solis cage provides favorable clinical outcomes and radiologic fusion rates comparing with other classical or alternative cervical fusion methods .
it does not cause plate relating complication and radiologic opacity of cage spike enable to locate a cage at optimal location by using fluoroscope .
there have been several reports that describe the efficacy of acdf with peek cage for short term follow - up , but long term(more than 24 months ) follow - up studies are rare .
we present here a long term follow - up study for acdf with peek cage and its clinical efficacy is favorable .
 objectiveto evaluate the utility of anterior cervical discectomy and fusion ( acdf ) with polyetheretherketone ( peek ) cage and autograft through long term(average 36 months ) follow-up.methodsthirty selected patients ( male:20/female:10 ) who suffered from cervical radiculopathy , myelopathy or radiculomyelopathy underwent a single level acdf with peek cage and autograft from iliac crest from march 2006 to july 2008 in single institute . 
 we followed patients for an average 36.48.1 months ( ranged from 23 to 49 months ) . 
 the japanese orthopedic association ( joa ) score for evaluation of myelopathy and visual analogue scale ( vas ) for radiating pain was used to estimate postoperative clinical outcome . 
 plain x - ray on true lateral standing flexion , extension and neutral position view and 3d ct scan were used every 6 months after surgery during follow - up period.resultsthe mean vas and joa scoring improved significantly after the surgery and radiological fusion rate was accomplished by 100% 36 months after the surgery . 
 we had no complication related with the surgery except one case of osteomyelitis . 
 there was one case of grade i fusion , four cases of grade ii , and 25 cases of grade iii by radiologic evaluation.conclusionthis long term follow - up study for acdf with peek cage shows that this surgical method is comparable with other anterior cervical fusion methods in terms of clinical outcomes and radiologic fusion rate . 