Adjacent Segment Pathology Research Articles

Risk-factor analysis of adjacent-segment pathology requiring surgery following anterior, posterior, fusion, and nonfusion cervical spine operations: survivorship analysis of 1358 patients.

Adjacent-segment pathology is an important issue involving the cervical spine, but there have been few comprehensive studies of this problem. The purpose of the current study was to determine the risk factors for adjacent-segment pathology and to compare the survivorship of adjacent segments in patients who underwent cervical spine operations including arthrodesis and motion-sparing procedures. This was a retrospective analysis of a consecutive series of 1358 patients with radiculopathy, myelopathy, or myeloradiculopathy who underwent cervical spine surgery performed by a single surgeon. We calculated the annual incidence of adjacent-segment pathology requiring surgery and, with use of Kaplan-Meier analysis, determined survivorship. Cox regression analysis was used to identify risk factors. The index surgical procedures included cervical arthrodesis (1095 patients; 1038 anterior, twenty-nine posterior, and twenty-eight combined anterior and posterior), posterior decompression (214 patients; 145 laminoplasty and sixty-nine foraminotomy), arthroplasty (thirty-two patients), and a combination of arthroplasty and anterior arthrodesis (seventeen patients). Secondary surgery on adjacent segments occurred at a relatively constant rate of 2.3% per year (95% confidence interval, 1.9 to 2.9). Kaplan-Meier analysis predicted that 21.9% of patients would need secondary surgery on adjacent segments by ten years postoperatively. Factors increasing the risk were smoking, female sex, and type of procedure. The posterior arthrodesis group (posterior-only or combined anterior and posterior arthrodesis) had a 7.5-times greater risk of adjacent-segment pathology requiring reoperation than posterior decompression, and a 3.0-times greater risk than the anterior arthrodesis group. However, when we compared the anterior cervical arthrodesis group, the arthroplasty group (arthroplasty or hybrid arthroplasty), and the posterior decompression group to each other, there were no significant differences. Age, neurological diagnosis, diabetes, and number of surgically treated segments were not significant risk factors. Patients treated with posterior or combined anterior and posterior arthrodesis were far more likely to develop clinical adjacent-segment pathology requiring surgery than those treated with posterior decompression or anterior arthrodesis. Smokers and women had a higher chance of clinical adjacent-segment pathology after cervical spine surgery.

Radiographic Adjacent Segment Pathology after Treatment with TDR or ACDF at One or Two Levels at Five Years

Radiographic Adjacent Segment Pathology after Treatment with TDR or ACDF at One or Two Levels at Five Years

Iatrogenic contributions to cervical adjacent segment pathology: review article.

Anterior cervical discectomy and fusion (ACDF) is widely accepted as a predictably excellent procedure. On the other hand, adjacent level pathology following ACDF is a well-known phenomenon which undercuts surgical outcome. However, the extent to which ACDF accelerates this phenomenon in the naturally degenerating cervical spine is still to be understood. To summarize the current evidence concerning adjacent segment pathology in the light of biomechanics, natural history, postoperative course, and comparison between ACDF and total disc replacement (TDR). This is a study of published articles. Articles were searched by the topic of adjacent disc pathology in cervical spine through Google Scholar and Pubmed. After review, 37 published articles were deemed suitable for the subject of this study. Biomechanical and clinical data strongly suggest that ASP is a presentation of the iatrogenically accelerated natural aging process of cervical spine. However, power study analysis with assumption showed that current RCTs are unlikely to prove this suggestion. Available data suggests that iatrogenic factors play a significant role in adjacent segment pathology following ACDF.

Use of Nitinol Rods for Lumbosacral Spine Fixation (Prospective Randomized Clinical Study)

One hundred thirty operations were performed in patients (57 males, 73 females) with degenerative lumbar spine diseases during the period from 2010 to 2012. Mean age of patients made up 57 (45-82) years. Depending on the type of intervention all patients were divided into 2 groups: in 60patients (1 st group) dynamic stabilization with nitinol rods without fusion and in 70patients (2 nd group) rigid fixation of lumbar spine with titanium rods was performed. Outcomes were analyzed in 1.5 years after surgery. VAS, ODI and SF36 questionnaires showed improvement of patients’ condition in both groups. Restoration of lordosis was from 22 to 35° and from 23 to 37° in 1 st and 2 nd groups, respectively. No screw instability, bone tissue resorption around the screws and adjacent segment pathology was noted in group 1. Functional X-rays showed preservation of mobility (5+1.2°). In 2 nd group formation of pseudarthrosis was recorded in 5patients, adjacent segment pathology - in 20 including 5 patients who required repeated surgical intervention. Transpedicular lumbosacral spine fixation using nitinol rods is an effective technique that enables to preserve movements in lumbosacral spine in combination with stable fixation

Commentary on: “Sagittal alignment as a predictor of clinical adjacent segment pathology requiring surgery after anterior cervical arthrodesis”

COMMENTARY ON Park MS, Kelly MP, Lee D-H, et al. Sagittal alignment as a predictor of clinical adjacent segment pathology requiring surgery after anterior cervical arthrodesis. Spine J 2014;14:1228–34 ( in this issue ).

Is It Real Adjacent Segment Pathology by Stress Concentration After Limited Fusion in Degenerative Lumbar Scoliosis?

A retrospective comparative study. To investigate adjacent segment pathology (ASP) after limited lumbar fusion in the treatment of degenerative lumbar scoliosis (DLS). The assessment of appropriate surgical techniques for DLS remains one of the most controversial topics in spinal surgery. So far, there has been no study specifically addressing why ASP shows different patterns with respect to different fusion levels after instrumented lumbar fusion for DLS. Fifty-nine patients were enrolled and divided into 2 groups with respect to the proximal fusion level: group I consisted of 29 patients who underwent fusion below the proximal neutral vertebrae, and group II consisted of 30 patients who underwent fusion to the proximal neutral vertebrae. Clinical and radiological assessments were performed with an average of 59.4 months of follow-up. The number of radiological findings for ASP was determined on the basis of a 7-point scale that gave 1 point for each radiological finding. The 2 groups were analyzed according to radiological ASP (RASP). The Oswestry Disability Index and visual analogue scale scores were recorded prospectively. Overall, RASP developed in 16 (27.1%) patients. In group I, 12 (41.4%) of 29 patients, and in group II, 4 (13.3%) of 30 patients showed RASP. Group I yielded an average of 4.5 points, and group II, 1.8 points. RASP scores were much higher in group I than in group II, with statistical significance (P = 0.000). In group I, 4 patients underwent revision surgery, but in group II, only 1 patient did so. RASP displayed variance according to different fusion levels. RASP in group I showed similar patterns to the natural progression of DLS. It is suggested that fusion be included at least at the proximal neutral vertebrae to reduce RASP although RASP with different patterns is unavoidable. 4.

The difference in superior adjacent segment pathology after lumbar posterolateral fusion by using 2 different pedicle screw insertion techniques in 9-year minimum follow-up.

A prospective study was performed. To test the hypothesis that different pedicle screw insertion positions would increase the likelihood of superior adjacent segment degeneration (ASD). Lumbar fusion surgery is a widely accepted treatment of lumbar diseases, such as lumbar stenosis, trauma, tumor, and spondylolisthesis. Fusion and clinical success rates have increased because of improvements in instrumentation and bone graft material. In contrast, numerous complications and problems of fusion surgery have been reported, with ASD being one of the most important. This prospective study included 210 patients with low-grade isthmic spondylolisthesis. From January 1999 to December 2003, patients were randomized underwent posterolateral fusion using 2 different pedicle screw insertion positions. The patients were followed up postoperatively and were assessed with regard to radiological and clinical outcomes. Radiological outcomes were assessed mainly on the basis of disc degeneration, facet joint degeneration, and bone fusion. Clinical outcomes were evaluated mainly with the use of visual analogue scale for pain and the Oswestry Disability Index. A total of 178 of 210 (84.7%) patients were available for at least 9-year radiological and clinical follow-up data: 85.3% (87/102) patients in group A and 84.3% (91/108) patients in group B. Bone fusion was achieved in all patients at the last follow-up. ASD was proven in 110 (61.8%) of 178 patients. The incidences of radiographical and symptomatic ASD were 57.9% (103/178) and 3.9% (7/178), respectively. The incidence of ASD in group B was significantly lower than that in group A. Results of clinical outcomes showed lower visual analogue scale and Oswestry Disability Index scores in 2 groups than preoperative scores, but group B had greater improvement on the Oswestry Disability Index scores than group A in patients with ASD. The degeneration of superior adjacent segment is closely related to the position of the pedicle screws during lumbar fusion surgery. The position of the pedicle screw farther from the facet joint surface can reduce the degeneration of superior adjacent segment. 3.

Transverse Process Hooks at Upper Instrumented Vertebra Provide More Gradual Motion Transition Than Pedicle Screws

Biomechanical study in a porcine model. To determine whether transverse process hooks (TPHs) placed at the proximal end of a long posterior spinal fusion construct provide a more gradual transition to normal motion of the adjacent cephalad motion segment compared with an all pedicle screw (APS) construct. Proximal junctional kyphosis after instrumentation with long posterior spinal constructs has been increasingly associated with incidence of adjacent segment pathologies. Clinical studies have suggested that proximal anchor type may affect the incidence of proximal junctional kyphosis. Biomechanical tests were conducted on porcine thoracic spines before and after implantation of a long spinal fusion construct. In all specimens, dual long rods (Co-Cr) were implanted posteriorly using pedicle screws at T7-T15. Upper instrumented vertebra, T6, received either TPHs (n = 7) or pedicle screws (APSs) (n = 6). Each specimen was tested in flexion-extension then lateral bending. Moments were applied, and vertebral displacements were recorded. Range of motion (ROM) and stiffness (K) were determined for each motion segment. Differences between TPH and APS at the transition were determined using t tests. In flexion-extension, ROM at the most proximal instrumented motion segment was 9% of control for APS versus 21% of control for TPH. Difference between APS and TPH at UIV was 0.5° (P < 0.008). Stiffness of TPH at T6-T7 was significantly lower than APS in FE (P < 0.003). For APS, the greatest mean ROM occurred at the first uninstrumented segment, whereas TPH maintained the pattern of monotonic increases in mean ROM from distal to proximal. TPHs at the upper instrumented vertebra provided a more gradual transition to normal motion compared with pedicle screws in long posterior spinal fusion constructs. TPH at the upper instrumented vertebra may be postulated to decrease the incidence of postoperative proximal junctional kyphosis compared with APS. N/A.

Cervical Disc Arthroplasty and Adjacent Segment Pathology

The advantages of arthroplasty include maintenance of motion, avoiding nonunions, and avoiding plate and screw complications such as backout, esophageal erosion, and periplate ossification. Thus far, the purported long-term benefit of reducing the incidence of adjacent segment pathology has not been born out in FDA-IDE trials reporting on up to 5-year results. Only one disc showed a difference. There is, however, some unpublished data that suggests that at &gt; 5 years, another arthroplasty has benefits over ACDF. In this study, I will review the available data. Disclosure of Interest None declared

The Incidence of Adjacent Segment Breakdown in Polysegmental Thoracolumbar Fusions of Three or More Levels with Minimum 5-Year Follow-up.

Study Design Retrospective cohort study. Objective To identify the incidence of adjacent segment pathology (ASP) after thoracolumbar fusion of three or more levels, the risk factors for the development of ASP, and the need for further surgical intervention in this particular patient population. Methods A retrospective analysis of a prospective surgical database identified 217 patients receiving polysegmental (≥ 3 levels) spinal fusion with minimum 5-year follow-up. Risk factors were evaluated, and the following data were obtained from the review of radiographs and charts: radiographic measures—levels fused, fusion status, presence of ASP; clinical measures—patient assessment, Oswestry Disability Index (ODI), and the need for further surgery. Results The incidence of radiographic ASP (RASP) was 29%; clinical or symptomatic ASP (CASP), 18%; and those requiring surgery, 9%. Correlation was observed between ODI and ASP, symptomatic ASP, and need for revision surgery. Age, preoperative degenerative diagnosis, and absence of fusion demonstrated significant association to ASP. Conclusions ASP was observed in a significant number of patients receiving polysegmental fusion of three or more levels. ODI scores correlated to RASP, CASP, and the need for revision surgery.

Clinical adjacent-segment pathology after anterior cervical discectomy and fusion: results after a minimum of 10-year follow-up

Background contextAnterior cervical discectomy and fusion using cervical plates has been seen as effective at relieving cervical radiculopathy and myelopathy symptoms. Although it is commonly used, subsequent disc degeneration at levels adjacent to the fusion remains an important problem. However, data on the frequency, impact, and predisposing factors for this pathology are still rare. PurposeTo evaluate the incidence, predisposing factors, and impact of radiographic and clinical adjacent-segment pathologies after anterior cervical discectomy and fusion using cervical plates and to analyze the efficacy of this surgical method over the long term, after a minimum follow-up period of 10 years. Study designRetrospective clinical study. Patient sampleOur study was a retrospective analysis of 177 patients who underwent anterior cervical discectomy and fusion using cervical plates, with follow-up periods of at least 10 years (mean 16.2 years). Outcome measuresRadiographic adjacent-segment pathology using plain radiographs and clinical adjacent-segment pathology after anterior cervical discectomy and fusion using cervical plates. MethodsWe defined a new grading system of plain radiographic evidence of degenerative changes in adjacent discs after anterior cervical discectomy and fusion using cervical plates; Grade 0 is considered normal, and Grade V consists the presence of posterior osteophytes and a decrease in disc height to less than 50% of normal. The incidence, predisposing factors, and impact of radiographic and clinical adjacent-segment pathologies were analyzed according to etiologies, number of fused segments, and plate-to-disc distance. ResultsRadiographic and clinical adjacent-segment pathologies were found in 92.1% and 19.2%, respectively, of patients. By etiology, clinical adjacent-segment pathology was observed in 13.5% of patients who had sustained trauma, 12.7% of those with disc herniation, and 33.3% of those with spondylosis. By number of fused segments, clinical adjacent-segment pathology was found in 13.2% of patients who underwent single-level fusion and in 32.1% of those who underwent multilevel fusion surgeries. Patients with a plate-to-disc distance of less than 5 mm, who had spondylosis, or who underwent multilevel fusion had a higher incidence of clinical adjacent-segment pathology after anterior cervical discectomy and fusion using cervical plates than other groups did (p<.05). Of all patients, only 6.8% needed follow-up surgery. ConclusionsWe found that over the long term, at a minimum follow-up point of 10 years, a plate-to-disc distance of less than 5 mm, having spondylosis, and undergoing multilevel fusion were predisposing factors for the occurrence of clinical adjacent-segment pathology. Nevertheless, the incidence of clinical findings of adjacent-segment pathology was much lower than the incidence of radiographic findings. Also, the rate of follow-up surgery was low. Therefore, anterior cervical discectomy and fusion using cervical plates can be considered a safe and effective procedure.

Lumbar Clinical Adjacent Segment Pathology

Retrospective case series. To evaluate reoperations for lumbar adjacent segment pathology (ASP) during a 10-year period. ASP after lumbar arthrodesis is an important clinical problem. There remains controversy, however, on the distribution of the most commonly affected levels. Thirty-one patients undergoing revision operation for ASP in the lumbar spine were included in this study. Patients' charts were evaluated for demographic data including age at index and revision operations, time to revision operation, and index and revision levels fused. L4-L5 was the most commonly instrumented level in both single-level (n = 12), and multilevel (n = 13) index fusions. The mean length of time from the index operation to revision surgery was 81 months (range, 11-570 mo). Kaplan-Meier analysis predicted a disease-free survival rate of 32.3% at 5 years and of 12.9% at 10 years after the index operation. L3-L4 was the most commonly affected level by ASP with 75% (16/20) requiring reoperation. L2-L3 was the next most commonly affected level at 52% (14/27). The L5-S1 disk was relatively protected from ASP, with only 4/17 (24%) disks at risk developing ASP. A subgroup analysis of patients undergoing revision after a single-level L4-L5 arthrodesis revealed ASP at L3-L4 in 83% (10/12) of patients, compared with only 3/12 (25%) at L5-S1 (P < 0.05). Of all cases of ASP, the proximal segments were involved 90% of the time. ASP most commonly affects proximal levels in the lumbar spine. In this cohort of patients undergoing revision fusion for ASP, 90% of affected levels were rostral to the index level(s). In patients undergoing L4-L5 single-level arthrodesis, L3-L4 is at high risk, whereas L5-S1 is somewhat protected. Surgeons should pay particular attention to proximal levels when planning a lumbar arthrodesis, however, motion segments distal to fusion may not be as protected as previously thought. 4.

Adjacent segment pathology following anterior decompression and fusion using cage and plate for the treatment of degenerative cervical spinal diseases.

Study DesignRetrospective study.PurposeTo analyze the incidence and prevalence of clinical adjacent segment pathology (CASP) following anterior decompression and fusion with cage and plate augmentation for degenerative cervical diseases.Overview of LiteratureNo long-term data on the use of cage and plate augmentation have been reported.MethodsThe study population consisted of 231 patients who underwent anterior cervical discectomy and fusion (ACDF) with cage and plate for degenerative cervical spinal disease. The incidence and prevalence of CASP was determined by using the Kaplan-Meier survival analysis. To analyze the factors that influence CASP, data on preoperative and postoperative sagittal alignment, spinal canal diameter, the distance between the plate and adjacent disc, extent of fusion level, and the presence or absence of adjacent segment degenerative changes by imaging studies were evaluated.ResultsCASP occurred in 15 of the cases, of which 9 required additional surgery. At 8-year follow-up, the average yearly incidence was 1.1%. The rate of disease-free survival based on Kaplan-Meier survival analysis was 93.6% at 5 years and 90.2% at 8 years. No statistically significant differences in CASP incidence based on radiological analysis were observed. Significantly high incidence of CASP was observed in the presence of increased adjacent segment degenerative changes (p<0.001).ConclusionsACDF with cage and plate for the treatment of degenerative cervical disease is associated with a lower incidence in CSAP by 1.1% per year, and the extent of preoperative adjacent segment degenerative changes has been shown as a risk factor for CASP.

Symptomatic Adjacent Segment Pathology after Posterior Lumbar Interbody Fusion for Adult Low-Grade Isthmic Spondylolisthesis

The incidence of symptomatic adjacent segment pathology (ASP) after fusion surgery for adult low-grade isthmic spondylolisthesis (IS) has been reported to be relatively low compared with other lumbar disease entities. However, there has been no study of symptomatic ASP incidence using posterior lumbar interbody fusion (PLIF) with pedicle screw instrumentation. We investigated the incidence of symptomatic ASP after PLIF with pedicle screw instrumentation for adult low-grade IS and identified significant risk factors for symptomatic ASP. We retrospectively studied records of 40 consecutive patients who underwent PLIF with pedicle screw instrumentation at the Department of Orthopaedic Surgery, Kansai Rosai Hospital, Amagasaki, Japan. The patients were followed for ≥ 4 years. Patients' medical records were retrospectively examined for evidence of symptomatic ASP. Age at time of surgery, sex, fusion level, whole lumbar lordosis, segmental lordosis, preexisting laminar inclination angle, and facet tropism at the cranial fusion segment were analyzed to identify risk factors for symptomatic ASP. Four patients (ASP group) developed symptomatic ASP at the cranial segment adjacent to the fusion. There were no significant differences in age, sex, fusion level, lumbar lordosis, segmental lordosis, or facet tropism at the cranial segment adjacent to the fusion between the ASP and the non-ASP groups. In contrast, laminar inclination angle at the cranial vertebra adjacent to the fusion was significantly higher in the ASP group than in the non-ASP group. Four patients (10%) developed symptomatic ASP after PLIF with transpedicular fixation for adult low-grade IS. Preexisting laminar horizontalization at the cranial vertebra adjacent to the fusion was a significant risk factor for symptomatic ASP.

Reoperation and Revision Rates of 3 Surgical Treatment Methods for Lumbar Stenosis Associated With Degenerative Scoliosis and Spondylolisthesis

Retrospective cohort analysis. To compare early treatment failures, survivorship, and clinical outcomes of 3 procedures used to treat symptomatic lumbar spinal stenosis and degenerative deformity. Symptomatic lumbar stenosis is commonly seen in association with degenerative deformity, often leading to more complex surgical treatment, with laminectomy and fusion, supplanting laminectomy alone. More recently, the interspinous process spacer (ISP), developed to treat straightforward spinal stenosis, has been used in patients with spinal deformity to limit morbidity, although no studies have compared outcomes in this patient population. A retrospective cohort analysis of 90 consecutive patients, mean age 70 years, with 5-year mean follow-up (minimum, 2 yr), treated for stenosis with associated deformity with ISP device placement, laminectomy alone, or laminectomy and short-segment fusion. Early failure was defined as return to the operating room for revision of the index level or adjacent segment within 2 years. A Kaplan-Meier survival analysis was performed, and clinical outcomes and patient satisfaction was assessed. Reoperation within 2 years was noted in 16.7% of patients treated for spinal stenosis and mild deformity. There was a significantly higher rate of same-level recurrence in the ISP group (33.3%), than the laminectomy (8.3%) and lami/fusion groups (0%) (P< 0.0001). Early reoperation due to adjacent segment pathology (ASP) was most common in the lami/fusion group (13.3%). Kaplan-Meier analysis revealed lowest survival for the ISP group and highest survival in the laminectomy-alone group at 2 years (P= 0.043) and 5 years (P= 0.007). Early failure was significantly more common in patients treated with an ISP device for spinal stenosis and lumbar deformity, whereas reoperation due to symptomatic adjacent segment pathology was most common in patients treated with laminectomy and fusion. Laminectomy alone had the highest rate of survival. 3.

Sagittal alignment as a predictor of clinical adjacent segment pathology requiring surgery after anterior cervical arthrodesis

Background contextPostoperative malalignment of the cervical spine may alter cervical spine mechanics and put patients at risk for clinical adjacent segment pathology requiring surgery. PurposeTo investigate whether a relationship exists between cervical spine sagittal alignment and clinical adjacent segment pathology requiring surgery (CASP-S) following anterior cervical fusion (ACF). Study designRetrospective matched study. Patient sampleA total of 122 patients undergoing ACF between 1996 and 2008 were identified, with a minimum of 2 years of follow-up. Outcome measuresRadiographs were reviewed to measure the sagittal alignment using C2 and C7 sagittal plumb lines, distance from the fusion mass plumb line to the C2 and C7 plumb lines, the alignment of the fusion mass, caudally adjacent disc angle, the sagittal slope angle of the superior end plate of the vertebra caudally adjacent to the fusion mass, T1 sagittal angle, overall cervical sagittal alignment, and curve patterns by Katsuura classification. MethodsA total of 122 patients undergoing ACF between 1996 and 2008 were identified, with a minimum of 1 year of follow-up. Patients were divided into groups according to the development of CASP (control/CASP-S) and by number/location of levels fused. Radiographs were reviewed to measure the sagittal alignment using C2 and C7 sagittal plumb lines, distance from the fusion mass plumb line to the C2 and C7 plumb lines, the alignment of the fusion mass, caudally adjacent disc angle, the sagittal slope angle of the superior end plate of the vertebra caudally adjacent to the fusion mass, T1 sagittal angle, overall cervical sagittal alignment, and curve patterns by Katsuura classification. Appropriate statistical tests were performed to calculate relationships between the variables and the development of CASP-S. No funds were received in support of this work. No benefits in any form have been or will be received from a commercial party related directly or indirectly to the subject of this article. ResultsThe groups were similar with regard to demographic and surgical variables. Lordosis was preserved in 82% (50/61) of the control group but in only 66% (40/61) of the CASP-S group (p=.033). More patients with a straight curve pattern developed CASP-S. The distance from the C2 to the C7 plumb line and T1 sagittal slope angle were lower in the CASP-S group with C5–C6 fusions compared with the control group. Also, the distance from C5–C6 fusion mass to C7 plumb line and C7 sagittal slope angle were lower in the CASP-S group with C5–C6 fusions. ConclusionsOur results suggest that malalignment of the cervical spine following an ACF at C5–C6 has an effect on the development of clinical adjacent segment pathology requiring surgery.

Clinical and Radiographic Adjacent Segment Pathology of the Cervical Spine

Clinical and Radiographic Adjacent Segment Pathology of the Cervical Spine

Cervical adjacent segment pathology following fusion: Is it due to fusion

Adjacent segment pathology affects 25% of patients within ten years of anterior cervical diskectomy and fusion (ACDF). Laboratory studies demonstrate fused segments increase adjacent level stress including elevated intradiscal pressure and increased range of motion. Radiographic adjacent segment pathology (RASP) has been associated to ACDF in multiple statistically significant studies. Randomized controlled trials (RCTs) comparing anterior cervical discectomy and arthroplasty (ACDA) and ACDF have confirmed ACDF accelerates RASP. The question of greatest clinical interest is whether ACDA, artificial disc surgery, results in fewer adjacent level surgeries than ACDF. Current RCT follow up results reveal only non statistically significant trends favoring ACDA yet the post operative periods are only two to four years. Statistically significant increased RASP in ACDF patients however is already documented. The RCT patients' average ages are in the mid forties with an expected longevity of up to forty more years. Early statistically significant increased RASP in the ACDF patients supports our prediction that given sufficient follow up of ten or more years, fusion will lead to statistically significant higher rate of adjacent level surgery compared to artificial disc surgery.

Does postsurgical cervical deformity affect the risk of cervical adjacent segment pathology? A systematic review.

Systematic review. To assess whether the presence or magnitude of postsurgical malalignment in the coronal (scoliosis) or sagittal plane (kyphosis/spondylolisthesis) affects the risk of cervical adjacent segment pathology (ASP). ASP occurs in selected patients who have undergone surgical treatment for cervical spondylosis. The reasons are multifactorial; however, postsurgical alignment may play a key role. To elucidate this issue, a systematic review of the literature was undertaken. A systematic search in PubMed was conducted for literature published in English language through February 15, 2012. Studies in adults, designed to evaluate postsurgical sagittal or coronal malalignment as risk factors for radiographical or clinical ASP, were sought. Studies of pediatric or oncological patients were excluded. Case reports, case series, and patient populations of less than 10 patients were also excluded. Unadjusted risk ratios (RRs) and 95% confidence intervals were calculated to evaluate the association between alignment and the risk for developing ASP. The search yielded 338 citations. Of that, 311 were excluded at the title and abstract level. Of the 27 selected for full-text review, 5 poor-quality retrospective studies met the inclusion criteria and described sagittal imbalance measures as risk factors for radiological ASP after anterior surgery. No studies examined ASP after posterior cervical surgery. Three studies provided data from which unadjusted RRs and 95% confidence intervals could be calculated. These studies showed an increased risk of ASP associated with malalignment (RR, 2.24 [95% confidence interval, 1.40-3.56]; RR, 2.40 [1.33, 4.33]; RR, 1.32 [0.96, 1.81]). No study evaluating coronal imbalance as a risk factor for cervical ASP was found and none reported on clinical ASP. There is low-grade evidence from 3 published studies that postsurgical sagittal imbalance may increase the risk for cervical radiological ASP. An attempt should be made to maintain or restore cervical lordosis in surgical intervention for cervical disorders. Strength of Statement: Weak.

Methodology for the Systematic Reviews on an Adjacent Segment Pathology

A systematic review. To provide a detailed description of the methods undertaken in the systematic search and analytical summary of adjacent segment pathology (ASP) issues and to describe the process used to develop consensus statements and clinical recommendations regarding factors associated with the prevention and treatment of ASP. We present methods used in conducting the systematic, evidence-based reviews and development of expert panel consensus statements and clinical recommendations on the classification, natural history, risk factors, and treatment of radiographical and clinical ASP. Our intent is that clinicians will combine the information from these reviews with an understanding of their own capacities and experience to better manage patients at risk of ASP and consider future research for the prevention and treatment of ASP. A systematic search and critical review of the English-language literature was undertaken for articles published on the classification, risk, risk factors, and treatment of radiographical and clinical ASP. Articles were screened for relevance using a priori criteria, and relevant articles were critically reviewed. Whether an article was included for review depended on whether the study question was descriptive, one of therapy, or one of prognosis. The strength of evidence for the overall body of literature in each topic area was determined by 2 independent reviewers considering risk of bias, consistency, directness, and precision of results using a modification of the Grades of Recommendation Assessment, Development and Evaluation (GRADE) criteria. Disagreements were resolved by consensus. Findings from articles meeting inclusion criteria were summarized. From these summaries, consensus statements or clinical recommendations were formulated among subject experts through a modified Delphi process using the GRADE approach. A total of 3382 articles were identified and screened on 14 topics relating to the classification, risks, risk factors, and treatment of radiographical and clinical ASP. Of these, 127 met our predetermined inclusion criteria and were used to answer specific clinical questions within each topic. Lack of precision in the terminology related to adjacent segment disease and critical evaluation of definitions used across included articles led to a consensus to use ASP and suggest it as a standard. No validated comprehensive classification system for ASP currently exists. The expert panel developed a consensus definition of radiographical and clinical ASP (RASP and CASP). Some of the highlights from the analyses included the annual, 5- and 10-year risks of developing cervical and lumbar ASP after surgery, several important risk factors associated with the development of cervical and lumbar ASP, and the possibility that some motion sparing procedures may be associated with a lower risk of ASP compared with fusion despite kinematic studies demonstrating similar adjacent segment mobility following these procedures. Other highlights included a high risk of proximal junctional kyphosis (PJK) following long fusions for deformity correction, postsurgical malalignment as a potential risk factor for RASP and the paucity of studies on treatment of cervical and lumbar ASP. Systematic reviews were undertaken to understand the classification, risks, risk factors, and treatment of RASP and CASP and to provide consensus statements and clinical recommendations. This article reports the methods used in the reviews.