- Is there evidence that artificial disc replacement (ADR) after neural decompression results in equal or improved outcomes compared with anterior cervical decompression and fusion (ACDF) for CSM?
- Is there evidence that skip laminectomy results in equal or improved outcomes compared with laminoplasty for CSM?
- Describe the outcomes of oblique corpectomy without fusion for CSM.
MATERIALS AND METHODS
Electronic Literature Search
We conducted a systematic search in MEDLINE and the Cochrane Collaboration Library for literature published through October 15, 2012. The search results were limited to human studies published in the English language containing abstracts. Identification of studies explicitly designed to evaluate outcomes associated with treatment of CSM was the primary focus. Terms specific to cervical myelopathy (cervical spondylotic myelopathy [Title/Abstract] OR cervical myelopathy [Title/Abstract] OR ((cervical spine OR cervical vertebrae) AND myelopath*) as well as those related to treatments and outcomes were used. Reference lists of key articles were also systematically checked to identify additional eligible articles. For questions 1 and 3, we sought to identify comparative studies (e.g., randomized controlled trials [RCTs], cohort studies) comparing ADR with ACDF and skip laminectomy with laminoplasty, whereas case series were considered for question 3. Articles were excluded if the patients were pediatric or were treated for tumor, trauma, infection, pathology requiring osteotomy, deformity correction, pathology of the thoracic spine, and ankylosing spondylitis, or if more than 20% of the subjects in the study had ossification of the posterior longitudinal ligament or previous adjacent segment pathology. We excluded studies that did not specifically report results for subjects with myelopathy and/or myeloradiculopathy diagnosis. Meeting abstracts/proceedings, white papers, editorials, case reports, cadaver or biomechanical studies, studies with less than 10 subjects for questions 1 and 2, and studies with less than 20 subjects for question 3 were also excluded.
Full text of the articles meeting the inclusion criteria were reviewed by 2 independent investigators (D.J.F., A.C.S.) to obtain the final collection of included studies. From the included articles, the following data were extracted: study design, patient demographics, inclusion and exclusion criteria, disease characteristics, treatment interventions, follow-up duration and the rate of follow-up for each treatment group (if reported or calculable), treatment outcomes, and complications.
Study Quality and Overall Strength of Body of Literature
Class-of-evidence (CoE) ratings were assigned to each included article independently by 2 reviewers (D.J.F., A.C.S.) using criteria set by The Journal of Bone & Joint Surgery1 for therapeutic studies and modified to delineate criteria associated with methodological quality and risk of bias based on recommendations made by the Agency for Healthcare Research and Quality.2,3 The appraisal system used in this article accounts for features of methodological quality and important sources of bias by combining epidemiologic principles with characteristics of study design to determine the class of evidence and is consistent with those used in previous focus issues.4 (See Supplemental Digital Content Tables, available at http://links.lww.com/BRS/A832, for study ratings.)
After individual article evaluation, the overall body of evidence with respect to each outcome was determined on the basis of precepts outlined by the Grading of Recommendation Assessment, Development and Evaluation Working Group5,6 and recommendations made by the Agency for Healthcare Research and Quality.2,3 Qualitative analysis was performed considering Agency for Healthcare Research and Quality–required and additional domains.7
The initial strength of the overall body of evidence was considered high if the majority of the studies were class I or II and low if the majority of the studies were class III or IV. Criteria for downgrading published evidence 1 or 2 levels included (1) inconsistency of results, (2) indirectness of evidence, (3) imprecision of the effect estimates (e.g., wide confidence intervals [CIs]), and (4) non-a priori statement of subgroup analyses. Alternatively, the body of evidence could be upgraded 1 or 2 levels on the basis of the following factors: (1) large magnitude of effect or (2) dose-response gradient. The final overall strength of the body of literature expresses our confidence that the effect size lies close to the true effect and the extent to which it is thought to be stable based on the adequacy or deficiencies in the body of evidence. An overall strength of “high” means that we are very confident that the true effect lies close to that of the estimated effect. A “moderate” rating means that we are moderately confident in the effect estimate; the true effect is likely to be close to the estimated effect, but there is a possibility that it is substantially different. An overall strength of “low” means that our confidence in the effect estimate is limited: The true effect may be substantially different from the estimate. Finally, a rating of “insufficient” means that we have very little confidence in the effect estimate: The true effect is likely to be substantially different than the estimated effect. In addition, this rating may be used if there is no evidence or it is not possible to estimate an effect. The Supplemental Digital Content Tables, available at http://links.lww.com/BRS/A832, contain the details of how we arrived at the strength of evidence for each key question.
Descriptive statistics for all studies were reported as presented in the articles since there was variability in the reporting of outcomes. For continuous outcome measures (e.g., the Japanese Orthopedic Association [JOA] scores), we reported the raw data and analytical statistics as detailed by the authors. For dichotomous outcomes (e.g., axial pain rates or complications), we reported the raw data and rates and calculated relative risks and their 95% CIs if not provided by the authors. Comparative statistics were recorded if included in the referenced articles. All calculations were performed using Stata 9.1 (StataCorp LP, College Station, TX).8
Clinical recommendations were made through a modified Delphi approach by applying the Grading of Recommendation Assessment, Development and Evaluation/Agency for Healthcare Research and Quality criteria that impart a deliberate separation between the strength of the evidence (i.e., high, moderate, low, or insufficient) and the strength of the recommendation. A more thorough description of this process can be found in the focus issue Methods article and has been described previously.9
The literature search yielded 141 unique, potentially relevant citations that were evaluated against the inclusion/exclusion criteria set a priori (Table 1). Two investigators independently considered studies for inclusion, and discrepancies in selection were resolved by discussion and, where necessary, evaluation of the full text. The majority of studies (n = 78) were excluded on the basis of title and abstract evaluation and the full text of 61 studies was reviewed, leading to exclusion of an additional 51 studies. The primary reason for exclusion was failure to report treatment outcomes specifically for patients with CSM. The details of the excluded studies are listed in the Supplemental Digital Content Tables, available at http://links.lww.com/BRS/A832.
For study question 1, 121 total citations were identified from the literature search that compared ACDF with ADR for the treatment of CSM. Of these, 73 were excluded by the title/abstract, and 48 full-text articles were evaluated to determine whether they met the inclusion/exclusion criteria. From these 48 studies, 46 were excluded because they did not report results separately in subjects with cervical myelopathy or myeloradiculopathy diagnosis, were review studies, or otherwise did not meet inclusion criteria. The remaining 2 studies met the inclusion criteria and are summarized in this report (Figure 3A). One study is an RCT comparing ACDF with ADR,10 and the other study is a prospective cohort study,11 which is a post hoc analysis of data from 2 RCTs.
For study question 2, 5 total citations were identified that compared laminoplasty with skip laminectomy. Of these, 1 was excluded by the title/abstract and 4 full-text articles were evaluated. One article included overlapping data with another study and was excluded. The remaining 3 articles met our inclusion criteria and are summarized in this report (Figure 3B). One study is an RCT comparing laminoplasty with skip laminectomy,12 1 study is a prospective cohort,13 and 1 study is a retrospective cohort comparing subjects who underwent skip laminectomy with a historic control group of subjects who received laminoplasty prior to December 1998.14
For study question 3, we identified 15 total citations from our literature search that reported on oblique corpectomy as a treatment of CSM. Six studies were excluded by the title/abstract and the 9 full-text articles were evaluated. Of these, 4 articles were excluded because they were technique articles, presented case series of less than 20 subjects, or otherwise did not meet inclusion criteria. The remaining 5 case series studies are summarized in this report (Figure 3B, C).15–19
Comparison of ACDF With Arthroplasty
Tables 2 and 3 summarize the characteristics of the included studies as well as outcomes and complications in studies comparing ACDF with ADR. One CoE II RCT10 and 1 CoE III prospective cohort study,11 which was a post hoc analysis of 2 RCTs, were included.
In an RCT,10 subjects with cervical myelopathy were randomized to undergo arthroplasty with implantation of a Bryan cervical disc prosthesis (n = 41) or ACDF (n = 42) and were followed for 36 months after treatment, achieving a 97.6% (81/83) follow-up rate. One-level procedures were performed in 54.2% (45/83) of subjects, 37.3% (31/83) of subjects underwent 2-level treatment, and 3-level decompressions and reconstructions were performed in 8.5% (7/83) of subjects. A statement of concealed allocation was not reported in this article, and sample size calculations were not provided. Although raw data were not presented for numerous outcomes, the authors reported that subjects who underwent ADR demonstrated significantly greater improvement than ACDF subjects in the JOA score (P < 0.02), Neck Disability Index (NDI; P < 0.0001), and 36-Item Short Form Health Survey (P < 0.05). Regarding complications, more subjects in the ACDF group experienced dysphagia than recipients of ADR (16.7% vs. 2.4%, P = 0.057).
A prospective cohort study examined a subset of subjects enrolled in 2 US Food and Drug Administration Investigational Device Exemption RCTs for the Prestige ST or Bryan artificial cervical disc who had evidence of single-level cervical myelopathy and were reported by Riew et al11 in a post hoc analysis. Subjects underwent ADR (Prestige, n = 59; Bryan, n = 47) or ACDF (Prestige, n = 52; Bryan, n = 41) and were followed for 24 months. In the Prestige trial, the NDI (arthroplasty 21.4 ± 20.1 at 24 mo vs. 22.4 ± 22.2 ACDF, P = not significant [NS]) as well as arm and neck pain outcomes (not reported [NR], P = NS), measured via visual analogue scale, was similar between ADR and ACDF groups, whereas these outcomes significantly favored the ADR group in the Bryan trial (arm pain: NR, P < 0.013; neck pain: NR, P < 0.013; NDI: 29.9 ± 26.3 ACDF vs. 16.5 ± 16.7 ADR at 24 months, P = 0.008). In both trials, there were nonsignificant differences that favored the ADR groups compared with ACDF in improvement of gait function, measured with the Nurick grade (Prestige ADR: 47.9%, 95% CI: 33.3%–62.8% vs. ACDF: 37.8%, 95% CI: 22.5%–55.2%, P = NS; Bryan ADR: 46.2%, 95% CI: 30.1%–62.8% vs. ACDF: 26.7%, 95% CI: 12.3%–45.9%, P = NS), and neurological function, which included an assessment of motor function, sensation, and reflexes (Prestige ADR: 89.8%, 95% CI: 77.8%–96.6%, P = NS vs. ACDF: 81.1%, 95% CI: 64.9%–92.0%; Bryan ADR; 89.7%, 95% CI: 75.8%–97.1% vs. ACDF: 76.7%, 95% CI: 57.7%–90.1%, P = NS). These nonsignificant differences may be partly due to imprecision of effect estimates. Reoperation rates were similar for ACDF and ADR groups in both trials (Prestige ADR: 1.7% [1/59] vs. ACDF: 3.8% [2/52]; Bryan ADR 2.1% [1/47] vs. ACDF 2.4% [1/41]).
Comparison of Laminoplasty With Skip Laminectomy
Tables 2 and 4 summarize the characteristics of included studies as well as outcomes and complications in studies comparing laminoplasty with skip laminectomy. One CoE II RCT,12 1 CoE III prospective cohort study,13 and 1 CoE III retrospective cohort study14 were included.
In an RCT,12 subjects with cervical myelopathy and evidence of spinal cord compression on magnetic resonance imaging were randomized by birth month to a modified double-door laminoplasty (n = 21) or skip laminectomy (n = 20) and were followed for at least 12 (mean 28.1 ± 10.1) months. Randomization by birth month did not allow for random sequence generation or concealed allocation and sample size calculations and intent-to-treat analyses were not performed. JOA scores (14.4 laminoplasty vs. 13.6 skip laminectomy, P = NS) and recovery rates, based upon JOA scores (60.6% laminoplasty vs. 57.5% skip laminectomy; P = NS), were similar between treatment groups at final follow-up. Neck visual analogue scale pain score was also similar between treatment groups (12.9 ± 21.1 laminoplasty vs. 21.7 ± 16.4 skip laminectomy, P = NS). Other outcome measures (C2–C7 lordosis, range of motion [ROM] at C2–C7, and recovery rate of ROM) were measured with radiographs, and no significant differences between groups were reported. No short-term complications (C5 paresis, infection, nerve injury) were reported in either treatment group.
In a prospective cohort study,13 50 consecutive subjects operated on for CSM with magnetic resonance imaging evidence of spinal cord compression underwent a double-door laminoplasty (n = 25) or a skip laminectomy (n = 25). Subjects were followed for a minimum of 24 months (range, 26.4–to 51.6 mo). ROM % (postoperative ROM/preoperative ROM), measured with radiographs, found motion to be significantly preserved in the skip laminectomy group compared with the laminoplasty group (84% skip laminectomy vs. 46% laminoplasty, P < 0.05). Cervical pain, measured with the 12-Item Short Form Health Survey (SF-12), was similar between groups at final follow-up (2.95 laminoplasty vs. 3.45 skip laminectomy, P = NS). Wound infection was reported in 1 subject in both treatment groups (1/25, 4.0%), with no other complications reported.
Shiraishi et al19 presented outcomes on subjects with multisegmental CSM and at least 24 months of follow-up for whom a complete set of preoperative and postoperative magnetic resonance images and plain radiographs was available. In addition to CSM, a proportion of subjects presented with developmental spinal canal stenosis (34.0%, 32/94), ossification of the posterior longitudinal ligament (9.6%, 9/94), localized ossification of the posterior longitudinal ligament associated with developmental spinal canal stenosis (8.5%, 8/94), calcification of yellow ligament (7.4%, 7/94), or calcification of yellow ligament associated with developmental spinal canal stenosis (2.1%, 2/94). Subjects underwent skip laminectomy December 1998 or later (n = 43) and were compared with a group of historic control subjects who underwent open door laminoplasty prior to December 1998 (n = 51). The recovery rates, based on JOA score, were similar between treatment groups and the effect estimates were large (60.1%, 95% CI: 28.6%–100% laminoplasty vs. 59.2%, 95% CI: 33%–80% skip laminectomy; P = NS). The ROM % found motion to be significantly preserved in the skip laminectomy group compared with the laminoplasty group (98.0%, 95% CI: 79.1%–123.5% skip laminectomy vs. 44%, 95% CI: 80.3%–102% laminoplasty; P < 0.05), although the CI reported in the article for the laminoplasty group is not consistent with the effect estimate. Regarding complications, short-term complication of C5 paresis (5.7%, 3/51) was reported in the laminoplasty group, and fracture of preserved laminae (7.0%, 3/43) and cerebrospinal fluid leakage (4.7%, 2/43) were reported in the skip laminectomy group. Long-term paresis was reported in 1 subject (1/51, 2.0%) in the laminoplasty group, with no other long-term complications reported.
Tables 2 and 5 summarize the characteristics of included studies as well as outcomes and complications in studies that reported results of oblique corpectomy in subjects with CSM. No comparative studies were found in the literature; consequently, 5 CoE IV case series were included.15–19 The subject population ranged from 40 to 268 subjects, and mean follow-up ranged from 7 to 96 months. In 3 articles, raw data were reported, but statistics comparing preoperative with postoperative values were not performed.16–18
For neurological outcomes, significant improvements in Nurick grade were reported at follow-up, compared with preoperative levels, in 2 studies (Chacko: 3.55 ± 0.73 preoperation vs. 2.46 ± 0.73 last follow-up, P < 0.001; Rocchi: 2.68 preoperation vs. 1.18 at 12 months, P = 0.002).15,19 JOA scores had also significantly improved at follow-up in these 2 studies (Chacko: 11.43 ± 2.10 preoperation vs. 14.15 ± 1.74 postoperation, P < 0.001; Rocchi: 12.3 preoperation vs. 14.6 at 12 months, P = 0.004).15,19 Other investigators reported JOA scores, although comparative statistics between baseline and follow-up were not provided (Chibbaro: 8.1 preoperation vs. 16.2 at last follow-up; Kiris: 12.83 ± 3.05 preoperation vs. 12.90 ± 2.60 at 6 mo).16,18 Regarding functional outcomes, Chacko and colleagues reported a significant decrease in neck ROM at last follow-up (29.52º ± 11.11º preoperation vs. 19.75º ± 9.51º last follow-up; P < 0.001), whereas Chibbaro and colleagues showed decreased NDI levels at last follow-up, although comparative statistics between pre- and post-treatment levels were not performed (55.2 preoperation vs. 26.2 last follow-up; P = NR).12,13 Neck pain was reported in 2 studies, both of which indicated decreased levels at follow-up, although comparative statistics between preoperative and postoperative levels were not performed (Chibbaro, 0–100 visual analogue scale: 65 preoperation vs. 25 last follow-up, P = NR; Kiris, 0–10 scale: 3.7 ± 3.8 preoperation vs. 2.2 ± 2.3 at 6 mo, P = NR).16,18 Regarding complications, transient Horner syndrome was reported in 4 studies, with rates ranging from 5.2% (14/268) to 32.1% (32/109), whereas the rates of permanent Horner syndrome ranged from 0% (0/48) to 10.0% (4/40). In these 4 studies, the cumulative rate of transient Horner syndrome was 15.7% (73/465) and that of permanent Horner syndrome was 3.4% (16/465).
The overall strength of evidence ratings for each key question and related outcomes are detailed in Table 6. The overall strength of evidence for the comparative effectiveness and safety of ACDF compared with ADR (question 1) for improvement of neurological, functional, pain, and safety outcomes was considered insufficient, meaning that we have very little confidence in the estimated effects. A flow diagram of the literature search (Figure 3A) details the paucity of true direct comparable reports of ACDF with ADR procedures in CSM. Inconsistency in results reporting and concerns regarding precision were the primary reasons the evidence strength was downgraded. Differences in measurement instruments and scales also made comparisons across studies difficult.
For the effectiveness and safety of laminoplasty compared with skip laminectomy procedures in CSM subjects, the overall strength of evidence was considered low for improvement of neurological outcomes, meaning that our confidence in the effect estimate is limited; the true effect may be substantially different from the estimate. Regarding improvement of functional, pain, and safety outcomes, the rating was insufficient, meaning that we have very little confidence in the estimated effects. Inconsistency in results reporting and imprecise or unknown precision of estimates led to a downgrade in the strength of evidence.
For key question 3, no studies comparing oblique corpectomy without fusion to other treatment options were found. The overall strength of evidence for improvement of neurological, functional, pain, and safety outcomes was considered insufficient. Only 5 case series studies (CoE IV) are available, resulting in baseline level of evidence graded as low. Inconsistency in results reporting and imprecise or unknown precision of estimates led to downgrading the evidence quality.
The majority of patients with symptomatic cervical spinal cord compression are treated with anterior decompression and fusion, laminectomy with or without fusion, and laminoplasty. Alternative procedures for the treatment of symptomatic cervical spinal cord compression due to degenerative disease have been described and these merit attention. The alternative anterior procedures were developed with the goal of maintaining motion after adequate anterior decompression. Skip laminectomy was developed to be a less invasive alternative to laminoplasty. The strength of this report is the use of a structured rigorous systematic search and review of numerous full-text articles to identify studies that assessed the efficacy of arthroplasty, oblique corpectomy without fusion, and skip laminectomy as alternative procedures for symptomatic CSM. Unfortunately, a paucity of high-quality literature exists. Furthermore, variable outcomes were reported in the included studies. Although limited data are available from these included studies on alternative treatment techniques, the small sample sizes, limited follow-up, quality of most studies, and instability of estimates preclude making conclusions regarding treatment options.
Myelopathy often occurs in the settings of congenital stenosis upon which is imposed degenerative changes and these are frequently multilevel. The arthroplasty studies included in this review address a very specific population, and their results may not be generalizable. Almost all of the patients had only 1- or 2-level disease and the mean age was less than 50 years. An extensive decompression should be performed when planning reconstruction with an artificial disc, but even after an optimal anterior procedure, there may be residual canal stenosis due to the congenitally small canal and ligamentous hypertrophy. This is particularly true in patients with more advanced and/or multilevel disease, and in this setting, it may be more appropriate to eliminate motion with a fusion.
The complication profiles of laminoplasty and skip laminectomy are interesting. Laminoplasty was associated with a 5.7% incidence of temporary C5 palsy, whereas this deficit did not occur in the skip laminoplasty cohort for reasons unknown. There were no cerebrospinal fluid leakages reported with laminoplasty but the skip laminectomy group had a 4.7% incidence of cerebrospinal fluid leakage, again for unknown reasons. There was no evidence that these leakages resulted in any long-term morbidity.
The outcome data for oblique corpectomy lack a control group. The relatively high rate of postoperative Horner syndrome is concerning. The procedure uses an approach starting lateral to the carotid sheath, and the sympathetic chain lying on the longus colli is in the surgical field and often requires at least some manipulation. An anterior approach for either multilevel discectomy or corpectomy only exposes the medial portion of the longus colli and, therefore, does not place the sympathetic chain at risk. Fountas et al20 performed a retrospective review of 1015 ACDFs and reported 1 case (0.1%) of temporary unilateral Horner syndrome that resolved spontaneously within 6 weeks. This contrasts sharply with the cumulative 15.7% rate of Horner syndrome and 3.4% of permanent Horner syndrome associated with oblique corpectomy. Although this complication may lessen with experience, it will almost certainly always be greater than that realized with other anterior and posterior decompressive operations.
Comparative prospective studies with long-term follow-up and standardized outcome measures are needed to appropriately assess treatment outcomes associated with all of these alternative techniques.
Evidence-Based Clinical Recommendations.
Recommendation 1. No recommendation can be made from comparative literature regarding treatment outcomes comparing ADR to ACDF for CSM.
Overall Strength of Evidence. Insufficient
Strength of Recommendation. Strong
Recommendation 2. No recommendation can be made from comparative literature regarding treatment outcomes comparing laminoplasty to skip laminectomy for CSM.
Overall Strength of Evidence. Low
Strength of Recommendation. Strong
Summary Statements. Oblique corpectomy is an option in selected cases of CSM. It should not be considered a first line treatment strategy due to the relatively high morbidity associated with this procedure.
- There is a lack of high-quality data comparing arthroplasty, oblique corpectomy, and skip laminectomy with “standard” surgical decompression with or without fusion.
- To enhance shared decision making, rigorous prospective studies using validated outcome measures with long-term follow-up are required.
Supplemental digital content is available for this article. Direct URL citations appearing in the printed text are provided in the HTML and PDF version of this article on the journal's web site (www.spinejournal.com).
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cervical spondylotic myelopathy; arthroplasty; oblique corpectomy; skip laminectomy; cervical myelopathy
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