***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
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    Input: In ventral fusion after anterior cervical discectomy there is still a remarkable number of cage subsidence and segmental kyphosis seen . The aim of the present study is to assess whether the cage design influences the extent of correction loss during follow-up . Sixty patients with single-level cervical disc herniation were r and omly treated with two different cervical inter-body cages ( group1 : Solis ™ cage , Stryker Company and group2 : Shell ™ cage , AMT Company ) . Clinical and radiological follow-up was done before and after surgery , 3 and 6 months post-surgery . Clinical follow-up was done with the help of Odom ’s criteria . Both groups were similar in the baseline parameters ( age , sex , treated level ) . Statistically , the subsidence was significantly higher at 3 and 6-month follow-ups in group1 than in group2 , however , clinical results showed no significant differences . In 67 % , subsidence was seen in the anterior lower aspect of the treated segment . Segmental kyphosis was seen in seven patients of group1 and two patients of group2 . A significant correlation is found between Odom ’s criteria and subsidence . Although there was no significant difference in a short-term clinical result between the two treatment groups , we recommend the use of cages which preserve the determined segmental height and lordosis OBJECT The authors compare clinical outcome and fusion rates after iliac crest autograft (ICAG)- and rectangular titanium cage (RTC)-augmented fusion in patients undergoing anterior cervical discectomy ( ACD ) . METHODS One hundred consecutive patients with 127 levels of cervical disc disease refractory to conservative treatment were r and omized into one of the two treatment groups ( ICAG/RTC fusion ) . The visual analog scale was used by the patient to rate overall pain and head , neck , arm , and donor site pain separately . Myelopathy was documented according to Japanese Orthopaedic Association and Nurick grading systems . Outcome was analyzed using Odom criteria , the 36-Item Short Form ( SF-36 ) , and Patient Satisfaction Index scales . Fusion rates were assessed on st and ard and flexion-extension radiographs . Follow-up data of at least 12 months ' duration were available for 95 patients . More residual overall pain after 12 months was documented in patients who underwent ICAG fusion ( 3.3 + /- 2.5 [ ICAG ] and 2.2 + /- 2.4 [ RTC ] ; p < 0.05 ) . Although arm and head pain were minimal in both groups , neck pain proved to be the predominant symptom ( 2.7 + /- 2.5 [ ICAG ] and 1.9 + /- 2.1 [ RTC ] ) , which resolved in only 67 and 48 % of RTC- and ICAG-treated patients , respectively ( p < 0.05 ) . Myelopathy improved comparably in both groups . Regardless of increased pain in ICAG-treated patients , PSI and SF-36 scores were not significantly different between groups ( only four [ 8 % ] of 47 ICAG-treated patients and five [ 10 % ] of 48 RTC-treated patients were unsatisfied ) . Good to excellent functional recovery according to Odom criteria was observed in 75 and 79 % of ICAG- and RTC-treated patients , respectively . Fusion rates were 81 and 74 % , respectively ( p = 0.51 ) . CONCLUSIONS Fusion rates and clinical outcome at 12 months after ACD were comparable between patients who underwent ICAG and RTC fusion . The use of rectangular cages , however , avoids donor site morbidity and reduces overall pain and , thus , seems to be an advantageous treatment alternative OBJECT The aim of this in vitro study was to determine the influence of simulated postoperative neck movements  on the stabilizing effect and subsidence of four different anterior cervical interbody fusion devices . Emphasis was placed on the relation between subsidence and spinal stability . METHODS The flexibility of 24 human cervical spine specimens was tested before and directly after being stabilized with a WING , BAK/C , AcroMed I/F cage , or with bone cement in st and ard flexibility tests under 50 N axial preload . Thereafter , 700 pure moment loading cycles ( + /- 2 Nm ) were applied in r and omized directions to simulate physiological neck movements . Additional flexibility tests in combination with measurements of the subsidence depth were conducted after 50 , 100 , 200 , 300 , 500 , and 700 loading cycles . In all four groups , simulated postoperative neck movements caused an increase of the range of motion ( ROM ) ranging from 0.4 to 3.1 degrees and of the neutral zone from 0.1 to 4.2 degrees . This increase in flexibility was most distinct in extension followed by flexion , lateral bending , and axial rotation . After cyclic loading , ROM tended to be lower in the group fitted with AcroMed cages ( 3.3 degrees in right lateral bending , 3.5 degrees in left axial rotation , 7.8 degrees in flexion , 8.3 degrees in extension ) and in the group in which bone cement was applied ( 5.4 degrees , 2.5 degrees , 7.4 degrees , and 8.8 degrees , respectively ) than in those fixed with the WING ( 6.3 degrees , 5.4 degrees , 9.7 degrees , and 6.9 degrees , respectively ) and BAK cages ( 6.2 degrees , 4.5 degrees , 10.2 degrees , and 11.6 degrees , respectively ) . CONCLUSIONS Simulated repeated neck movements not only caused an increase of the flexibility but also subsidence of the implants into the adjacent vertebrae . The relation between flexibility increase and subsidence seemed to depend on the implant design : subsiding BAK/C cages partially supported stability whereas subsiding WING cages and AcroMed cages did not The complications of autogenous bone grafting cause spinal surgeons to seek alternative methods for cervical spinal fusion . This prospect i ve study was conducted to evaluate the safety and efficacy of rectangular titanium cages as compared to the widely performed iliac crest autograft fusion . Thirty-six patients with cervical disc disease in whom an anterior cervical approach was indicated for discectomy were included in a prospect i ve controlled study protocol with 1-year follow-up . The first 18 consecutive patients received iliac crest autograft , while the next 18 received rectangular titanium cages . According to Odom 's criteria , 15 of 18 ( 83 % ) patients in both groups experienced good to excellent functional recovery . According to the patient satisfaction index , 17 of 18 ( 94 % ) in both groups were satisfied . There were no significant differences in neck or arm pain . Fusion was present after 1 year in 16 of 18 ( 89 % ) patients in the iliac crest autograft group and 15 of 18 ( 83 % ) in the rectangular titanium cage group . In the autograft group , one case of pseudarthrosis was present , and marked hip pain was observed in four patients . There were no implant-related complications in the cage group . The authors conclude that titanium cages in anterior cervical discectomy constitute a safe and efficient alternative to iliac crest bone autograft We carried out a prospect i ve study to determine whether the addition of a recombinant human bone morphogenetic protein ( rhBMP-2 ) to a machined allograft spacer would improve the rate of intervertebral body fusion in the spine . We studied 77 patients who were to undergo an interbody fusion with allograft and instrumentation .  The first 36 patients received allograft with adjuvant rhBMP-2 ( allograft/rhBMP-2 group ) , and the next 41 , allograft and demineralised bone matrix ( allograft/demineralised bone matrix group ) . Each patient was assessed clinical ly and radiologically both pre-operatively and at each follow-up visit using st and ard methods . Follow-up continued for two years . Every patient in the allograft/rhBMP-2 group had fused by six months . However , early graft lucency and significant ( > 10 % ) subsidence were seen radiologically in 27 of 55 levels in this group . The mean graft height subsidence was 27 % ( 13 % to 42 % ) for anterior lumbar interbody fusion , 24 % ( 13 % to 40 % ) for transforaminal lumbar interbody fusion , and 53 % ( 40 % to 58 % ) for anterior cervical discectomy and fusion . Those who had undergone fusion using allograft and demineralised bone matrix lost only a mean of 4.6 % ( 0 % to 15 % ) of their graft height . Although a high rate of fusion ( 100 % ) was achieved with rhBMP-2 , significant subsidence occurred in more than half of the levels ( 23 of 37 ) in the lumbar spine and 33 % ( 6 of 18 ) in the cervical spine . A 98 % fusion rate ( 62 of 63 levels ) was achieved without rhBMP-2 and without the associated graft subsidence . Consequently , we no longer use rhBMP-2 with allograft in our practice if the allograft has to provide significant structural support Study Design All patients of spinal interbody fusion using polyetheretherketone ( PEEK ) cages and recombinant human bone morphogenetic protein (rhBMP)-2 performed over a 16-month period were review ed . Objective To determine the suitability of PEEK cages when used in conjunction with rhBMP-2 in interbody spinal fusion . Summary of Background Data Bone morphogenetic proteins are increasingly being used in spinal fusion to promote osteogenesis . PEEK is a semicrystalline aromatic polymer that is used as a structural spacer to maintain the disc and foraminal height . Their use has led to increased and predictable rates of fusion . However , not many reports of the adverse effects of their use are available . Methods Fifty-nine consecutive patients of interbody spinal fusion in the cervical or lumbar spine using a PEEK cage and rhBMP-2  were followed for an average of 26 months after surgery . A clinical examination and a record of Oswestry Disability Index , Visual Analog Scale for pain , and a pain diagram were performed preoperatively and at every follow-up visit . All patients had plain radiographs carried out to assess fusion . Ten patients of lumbar spine fusion were additionally evaluated with a computed tomography scan . Results All cases demonstrated an appreciable amount of new bone formation by 6 to 9 months in the cervical spine and by 9 to 12 months in the lumbar spine . End plate resorption was visible radiologically in all cervical spine fusions and majority of lumbar fusions . Cage migration was observed to occur maximally in patients with transforaminal lumbar interbody fusion and posterior lumbar interbody fusion . Disc space subsidence was seen in both cervical and lumbar arthrodesis with the latter showing a lesser incidence , but with a greater degree of collapse . Conclusions PEEK cages and rhBMP-2 when used in spinal fusion give consistently good fusion rates . However , the early role of BMP in the resorptive phase may cause loosening , cage migration , and subsidence A variety of bone graft substitutes , interbody cages , and anterior plates have been used in cervical interbody fusion , but no controlled study was conducted on the clinical performance of β-tricalcium phosphate ( β-TCP ) and the effect of supplemented anterior plate fixation . The objective of this prospect i ve , r and omized clinical study was to evaluate the effectiveness of implanting interbody fusion cage containing β-TCP for the treatment of cervical radiculopathy and /or myelopathy , and the fusion rates and outcomes in patients with or without r and omly assigned plate fixation . Sixty-two patients with cervical radiculopathy and /or myelopathy due to soft disc herniation or spondylosis were treated with one- or two-level discectomy and fusion with interbody cages containing β-TCP . They were r and omly assigned to receive supplemented anterior plate ( n = 33 ) or not ( n = 29 ) . The patients were followed up for 2 years postoperatively . The radiological and clinical outcomes were assessed during a 2-year follow-up . The results showed that the fusion rate ( 75.0 % ) 3 months after surgery in patients treated without anterior cervical plating was significantly lower than that ( 97.9 % ) with plate fixation ( P < 0.05 ) , but successful bone fusion was achieved in all patients of both groups at 6-month follow-up assessment . Patients treated without anterior plate fixation had 11 of 52 ( 19.2 % ) cage subsidence at last follow-up . No difference ( P > 0.05 ) was found regarding improvement in spinal curvature as well as neck and arm pain , and recovery rate of JOA score at all time intervals between the two groups . Based on the findings of this study , interbody fusion cage containing β-TCP following one- or two-level discectomy proved to be an effective treatment for cervical spondylotic radiculopathy and /or myelopathy . Supplemented anterior plate fixation can promote interbody fusion and prevent cage subsidence but do not improve the 2-year outcome when compared with those treated without anterior plate fixation In a multicenter , prospect i ve , r and omized , nonblinded , 2-year study , 279 patients with degenerative lumbar disc disease were r and omly divided into two groups that underwent interbody fusion using two tapered threaded fusion cages . The investigational group ( 143 patients ) received rhBMP-2 on an absorbable collagen sponge , and a control group ( 136 patients ) received autogenous iliac crest bone graft . Plain radiographs and computed tomographic scans were used to evaluate fusion at 6 , 12 , and 24 months after surgery 
    Output:
    
Subsidence irrespective of the measurement technique or definition does not appear to have an impact on successful fusion and /or clinical outcomes .