Laminectomy and fusion versus laminoplasty for the treatment of degenerative cervical myelopathy: results from the AOSpine North America and International prospective multicenter studies

BACKGROUND CONTEXT

It remains unclear whether cervical laminoplasty (LP) offers advantages over cervical laminectomy and fusion (LF) in patients undergoing posterior decompression for degenerative cervical myelopathy (DCM).

PURPOSE

The objective of this study is to compare outcomes of LP and LF.

STUDY DESIGN/SETTING

This is a multicenter international prospective cohort study.

PATIENT SAMPLE

A total of 266 surgically treated symptomatic DCM patients undergoing cervical decompression using LP (N=100) or LF (N=166) were included.

OUTCOME MEASURES

The outcome measures were the modified Japanese Orthopaedic Association score (mJOA), Nurick grade, Neck Disability Index (NDI), Short-Form 36v2 (SF36v2), length of hospital stay, length of stay in the intensive care unit, treatment complications, and reoperations.

METHODS

Differences in outcomes between the LP and LF groups were analyzed by analysis of variance and analysis of covariance. The dependent variable in all analyses was the change score between baseline and 24-month follow-up, and the independent variable was surgical procedure (LP or LF). In the analysis of covariance, outcomes were compared between cohorts while adjusting for gender, age, smoking, number of operative levels, duration of symptoms, geographic region, and baseline scores.

RESULTS

There were no differences in age, gender, smoking status, number of operated levels, and baseline Nurick, NDI, and SF36v2 scores between the LP and LF groups. Preoperative mJOA was lower in the LP compared with the LF group (11.52±2.77 and 12.30±2.85, respectively, p=.0297). Patients in both groups showed significant improvements in mJOA, Nurick grade, NDI, and SF36v2 physical and mental health component scores 24 months after surgery (p<.0001). At 24 months, mJOA scores improved by 3.49 (95% confidence interval [CI]: 2.84, 4.13) in the LP group compared with 2.39 (95% CI: 1.91, 2.86) in the LF group (p=.0069). Nurick grades improved by 1.57 (95% CI: 1.23, 1.90) in the LP group and 1.18 (95% CI: 0.92, 1.44) in the LF group (p=.0770). There were no differences between the groups with respect to NDI and SF36v2 outcomes. After adjustment for preoperative characteristics, surgical factors and geographic region, the differences in mJOA between surgical groups were no longer significant. The rate of treatment-related complications in the LF group was 28.31% compared with 21.00% in the LP group (p=.1079).

CONCLUSIONS

Both LP and LF are effective at improving clinical disease severity, functional status, and quality of life in patients with DCM. In an unadjusted analysis, patients treated with LP achieved greater improvements on the mJOA at 24-month follow-up than those who received LF; however, these differences were insignificant following adjustment for relevant confounders.

Riluzole blocks perioperative ischemia-reperfusion injury and enhances postdecompression outcomes in cervical spondylotic myelopathy

Although surgical decompression is considered the gold standard treatment for cervical spondylotic myelopathy (CSM), a proportion of cases show postoperative decline or continue to exhibit substantial neurological dysfunction. To investigate this further, we first examined data from the prospective multicenter AOSpine North America CSM study, finding that 9.3% of patients exhibited postoperative functional decline (ΔmJOA, ≤-1) and that 44% of patients were left with substantial neurological impairment 6 months postoperatively. Notably, 4% of patients experienced perioperative neurological complications within 20 days after surgery in otherwise uneventful surgeries. To shed light on the mechanisms underlying this phenomenon and to test a combination therapeutic strategy for CSM, we performed surgical decompression in a rat model of CSM, randomizing some animals to also receive the U.S. Food and Drug Administration-approved drug riluzole. Spinal cord blood flow measurements increased after decompression surgery in rats. CSM rats showed a transient postoperative neurological decline akin to that seen in some CSM patients, suggesting that ischemia-reperfusion injury may occur after decompression surgery. Riluzole treatment attenuated oxidative DNA damage in the spinal cord and postoperative decline after decompression surgery. Mechanistic in vitro studies also demonstrated that riluzole preserved mitochondrial function and reduced oxidative damage in neurons. Rats receiving combined decompression surgery and riluzole treatment displayed long-term improvements in forelimb function associated with preservation of cervical motor neurons and corticospinal tracts compared to rats treated with decompression surgery alone.

The Relationship Between Preoperative Clinical Presentation and Quantitative Magnetic Resonance Imaging Features in Patients With Degenerative Cervical Myelopathy

BACKGROUND: Degenerative cervical myelopathy encompasses a group of conditions resulting in progressive spinal cord injury through static and dynamic compression. Although a constellation of changes can present on magnetic resonance imaging (MRI), the clinical significance of these findings remains a subject of controversy and discussion.

OBJECTIVE: To investigate the relationship between clinical presentation and quantitative MRI features in patients with degenerative cervical myelopathy.

METHODS: A secondary analysis of MRI and clinical data from 114 patients enrolled in a prospective, multicenter study was conducted. MRIs were assessed for maximum spinal cord compression (MSCC), maximum canal compromise (MCC), signal changes, and a signal change ratio (SCR). MRI features were compared between patients with and those without myelopathy symptoms with the use of t tests. Correlations between MRI features and duration of symptoms were assessed with the Spearman ρ.

RESULTS: Numb hands and Hoffmann sign were associated with greater MSCC (P &lt; .05); broad-based, unstable gait, impairment of gait, and Hoffmann sign were associated with greater MCC (P &lt; .05); and numb hands, Hoffmann sign, Babinski sign, lower limb spasticity, hyperreflexia, and T1 hypointensity were associated with greater SCR (P &lt; .05). Patients with a T2 signal hyperintensity had greater MSCC and MCC (P &lt; .001).

CONCLUSION: MSCC was associated with upper limb manifestations, and SCR was associated with upper limb, lower limb, and general neurological deficits. Hoffmann sign occurred more commonly in patients with a greater MSCC, MCC and SCR. The Lhermitte phenomenon presented more commonly in patients with a lower SCR and may be an early indicator of mild spinal cord involvement. Research to validate these findings is required.

Optimal Timing of Surgical Decompression for Acute Traumatic Central Cord Syndrome: A Systematic Review of the Literature

BACKGROUND

Traumatic central cord syndrome (TCCS) is an incomplete spinal cord injury defined by greater weakness in upper versus lower extremities, variable sensory loss, and variable bladder, bowel, and sexual dysfunction. The optimal timing of surgery for TCCS remains controversial.

OBJECTIVE

To determine whether timing of surgery for TCCS predicts neurological outcomes, length of stay, and complications.

METHODS

Five databases were searched through March 2015. Articles were appraised independently by 2 reviewers, and the evidence synthesized according to Grading of Recommendation Assessment, Development and Evaluation principles.

RESULTS

Nine studies (3 prognostic, 5 therapeutic, 1 both) satisfied inclusion criteria. Low level evidence suggests that patients operated on <24 hours after injury exhibit significantly greater improvements in postoperative American Spinal Injury Association motor scores and the functional independence measure at 1 year than those operated on >24 hours after injury. Moderate evidence suggests that patients operated on <2 weeks after injury have a higher postoperative Japanese Orthopaedic Association score and recovery rate than those operated on >2 weeks after injury. There is insufficient evidence that lengths of hospital or intensive care unit stay differ between patients who undergo early versus delayed surgery. Furthermore, there is insufficient evidence that timing between injury and surgery predicts mortality rates or serious or minor adverse events.

CONCLUSION

Surgery for TCCS <24 hours after injury appears safe and effective. Although there is insufficient evidence to provide a clear recommendation for early surgery (<24 hours), it is preferable to operate during the first hospital admission and <2 weeks after injury.

Predicting the minimum clinically important difference in patients undergoing surgery for the treatment of degenerative cervical myelopathy

OBJECTIVE

The minimum clinically important difference (MCID) is defined as the minimum change in a measurement that a patient would identify as beneficial. Before undergoing surgery, patients are likely to inquire about the ultimate goals of the operation and of their chances of experiencing meaningful improvements. The objective of this study was to define significant predictors of achieving an MCID on the modified Japanese Orthopaedic Association (mJOA) scale at 2 years following surgery for the treatment of degenerative cervical myelopathy (DCM).

METHODS

Seven hundred fifty-seven patients were prospectively enrolled in either the AOSpine North America or International study at 26 global sites. Fourteen patients had a perfect preoperative mJOA score of 18 and were excluded from this analysis (n = 743). Data were collected for each participating subject, including demographic information, symptomatology, medical history, causative pathology, and functional impairment. Univariate log-binominal regression analyses were conducted to evaluate the association between preoperative clinical factors and achieving an MCID on the mJOA scale. Modified Poisson regression using robust error variances was used to create the final multivariate model and compute the relative risk for each predictor.

RESULTS

The sample consisted of 463 men (62.31%) and 280 women (37.69%), with an average age of 56.48 ± 11.85 years. At 2 years following surgery, patients exhibited a mean change in functional status of 2.71 ± 2.89 points on the mJOA scale. Of the 687 patients with available follow-up data, 481 (70.01%) exhibited meaningful gains on the mJOA scale, whereas 206 (29.98%) failed to achieve an MCID. Based on univariate analysis, significant predictors of achieving the MCID on the mJOA scale were younger age; female sex; shorter duration of symptoms; nonsmoking status; a lower comorbidity score and absence of cardiovascular disease; and absence of upgoing plantar responses, lower-limb spasticity, and broad-based unstable gait. The final model included age (relative risk [RR] 0.924, p < 0.0001), smoking status (RR 0.837, p = 0.0043), broad-based unstable gait (RR 0.869, p = 0.0036), and duration of symptoms (RR 0.943, p = 0.0003).

CONCLUSIONS

In this large multinational prospective cohort, 70% of patients treated surgically for DCM exhibited a meaningful functional gain on the mJOA scale. The key predictors of achieving an MCID on the mJOA scale were younger age, shorter duration of symptoms, nonsmoking status, and lack of significant gait impairment.

Comparison of Outcomes of Surgical Treatment for Ossification of the Posterior Longitudinal Ligament Versus Other Forms of Degenerative Cervical Myelopathy: Results from the Prospective, Multicenter AOSpine CSM-International Study of 479 Patients

BACKGROUND

Degenerative cervical myelopathy (DCM) is an all-encompassing term that includes cervical spondylotic myelopathy (CSM), ossification of the posterior longitudinal ligament (OPLL), and other spinal abnormalities that cause cervical cord compression. It is unclear whether surgery is equally effective and safe for patients with OPLL as it is for those with other forms of DCM. The purpose of this study was to compare surgical outcomes of patients with OPLL and those with other forms of DCM.

METHODS

Four hundred and seventy-nine patients with symptomatic DCM were prospectively enrolled in the CSM-International study at sixteen sites. Patients' functional status was evaluated using the modified Japanese Orthopaedic Association scale (mJOA) and the Nurick score. Quality of life was assessed using patient-reported outcome measures, including the Neck Disability Index (NDI) and the Short Form (SF)-36. Postoperative functional and quality-of-life outcomes were assessed at two years of follow-up, and scores were compared between patients with and without OPLL.

RESULTS

Of 479 patients, 135 (28.2%) had radiographic evidence of OPLL, and 344 (71.8%) had other forms of DCM. The two groups did not differ significantly in demographics, surgical approach, or baseline myelopathy severity. Patients with OPLL achieved similar functional outcomes by two years following surgery compared with patients with other forms of DCM. With respect to quality of life, the NDI and most of the subscales of the SF-36 were not different between the two diagnostic groups. There was a higher risk of perioperative complications in the OPLL group (p = 0.054), although this relationship did not reach statistical significance. Rates of neurological complications did not differ significantly between diagnostic groups.

CONCLUSIONS

Surgical decompression for the treatment of OPLL resulted in improvements in functional status and quality of life comparable to those seen in patients with other forms of DCM. Patients with OPLL were at a higher risk of perioperative complications than patients with other forms of DCM.

A Clinical Prediction Rule for Functional Outcomes in Patients Undergoing Surgery for Degenerative Cervical Myelopathy: Analysis of an International Prospective Multicenter Data Set of 757 Subjects

BACKGROUND

Cervical spondylotic myelopathy (CSM) is a progressive spinal condition that is often managed surgically. Knowledge of important predictors of surgical outcome can provide decision support to surgeons and enable them to effectively manage their patients' expectations. The purpose of this study was to identify the most important clinical predictors of surgical outcome in patients with CSM using data from two multinational prospective studies.

METHODS

A total of 757 patients treated surgically for CSM participated in either the CSM-North America or the CSM-International study. The model was designed to distinguish between patients who achieved a modified Japanese Orthopaedic Association (mJOA) score of ≥16 at the one-year follow-up and those who did not (mJOA < 16). A score of 16 was chosen as the cutoff as an mJOA of ≥16 translates to minimal impairment. Univariate analyses evaluated the relationship between outcome and various clinical predictors. Multivariate Poisson regression was used to create the final prediction rule and estimate relative risks.

RESULTS

Based on univariate analyses, the probability of achieving a score of ≥16 decreased with the presence of certain symptoms, including gait dysfunction, the presence of certain signs such as lower limb spasticity, positive smoking status, higher comorbidity score, more severe preoperative myelopathy, and older age. The final model consisted of six significant and clinically relevant predictors: baseline severity score (relative risk [RR], 1.11; 95% confidence interval [CI], 1.07 to 1.15), impaired gait (RR, 0.76 [ref. = absence]; 95% CI, 0.66 to 0.88), age (RR, 0.91 per decade; 95% CI, 0.85 to 0.96), comorbidity score (RR, 0.93; 95% CI, 0.88 to 0.98), smoking status (RR, 0.78 [ref. = non-smoking]; 95% CI, 0.65 to 0.93), and duration of symptoms (RR, 0.95; 95% CI, 0.90 to 0.99).

CONCLUSIONS

Patients were more likely to achieve a score of ≥16 (indicating minimal impairment) if they were younger, had milder preoperative myelopathy, did not smoke, had fewer and less severe comorbidities, did not present with impaired gait, and had shorter symptom duration.

Translating state-of-the-art spinal cord MRI techniques to clinical use: A systematic review of clinical studies utilizing DTI, MT, MWF, MRS, and fMRI

BACKGROUND

A recent meeting of international imaging experts sponsored by the International Spinal Research Trust (ISRT) and the Wings for Life Foundation identified 5 state-of-the-art MRI techniques with potential to transform the field of spinal cord imaging by elucidating elements of the microstructure and function: diffusion tensor imaging (DTI), magnetization transfer (MT), myelin water fraction (MWF), MR spectroscopy (MRS), and functional MRI (fMRI). However, the progress toward clinical translation of these techniques has not been established.

METHODS

A systematic review of the English literature was conducted using MEDLINE, MEDLINE-in-Progress, Embase, and Cochrane databases to identify all human studies that investigated utility, in terms of diagnosis, correlation with disability, and prediction of outcomes, of these promising techniques in pathologies affecting the spinal cord. Data regarding study design, subject characteristics, MRI methods, clinical measures of impairment, and analysis techniques were extracted and tabulated to identify trends and commonalities. The studies were assessed for risk of bias, and the overall quality of evidence was assessed for each specific finding using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) framework.

RESULTS

A total of 6597 unique citations were identified in the database search, and after full-text review of 274 articles, a total of 104 relevant studies were identified for final inclusion (97% from the initial database search). Among these, 69 studies utilized DTI and 25 used MT, with both techniques showing an increased number of publications in recent years. The review also identified 1 MWF study, 11 MRS studies, and 8 fMRI studies. Most of the studies were exploratory in nature, lacking a priori hypotheses and showing a high (72%) or moderately high (20%) risk of bias, due to issues with study design, acquisition techniques, and analysis methods. The acquisitions for each technique varied widely across studies, rendering direct comparisons of metrics invalid. The DTI metric fractional anisotropy (FA) had the strongest evidence of utility, with moderate quality evidence for its use as a biomarker showing correlation with disability in several clinical pathologies, and a low level of evidence that it identifies tissue injury (in terms of group differences) compared with healthy controls. However, insufficient evidence exists to determine its utility as a sensitive and specific diagnostic test or as a tool to predict clinical outcomes. Very low quality evidence suggests that other metrics also show group differences compared with controls, including DTI metrics mean diffusivity (MD) and radial diffusivity (RD), the diffusional kurtosis imaging (DKI) metric mean kurtosis (MK), MT metrics MT ratio (MTR) and MT cerebrospinal fluid ratio (MTCSF), and the MRS metric of N-acetylaspartate (NAA) concentration, although these results were somewhat inconsistent.

CONCLUSIONS

State-of-the-art spinal cord MRI techniques are emerging with great potential to improve the diagnosis and management of various spinal pathologies, but the current body of evidence has only showed limited clinical utility to date. Among these imaging tools DTI is the most mature, but further work is necessary to standardize and validate its use before it will be adopted in the clinical realm. Large, well-designed studies with a priori hypotheses, standardized acquisition methods, detailed clinical data collection, and robust automated analysis techniques are needed to fully demonstrate the potential of these rapidly evolving techniques.

The Practical Application of Clinical Prediction Rules: A Commentary Using Case Examples in Surgical Patients with Degenerative Cervical Myelopathy

Study Design Commentary. Objective This commentary aims to discuss the practical applications of a clinical prediction rule (CPR) developed to predict functional status in patients undergoing surgery for the treatment of degenerative cervical myelopathy. Methods Clinical cases from the AOSpine CSM-North America study were used to illustrate the application of a prediction rule in a surgical setting and to highlight how this CPR can be used to ultimately enhance patient care. Results A CPR combines signs and symptoms, patient characteristics, and other predictive factors to estimate disease probability, treatment prognosis, or risk of complications. These tools can influence allocation of health care resources, inform clinical decision making, and guide the design of future research studies. In a surgical setting, CPRs can be used to (1) manage patients' expectations of outcome and, in turn, improve overall satisfaction; (2) facilitate shared decision making between patient and physician; (3) identify strategies to optimize surgical results; and (4) reduce heterogeneity of care and align surgeons' perceptions of outcome with objective evidence. Conclusions Valid and clinically-relevant CPRs have tremendous value in a surgical setting.

Survival and Clinical Outcomes in Surgically Treated Patients With Metastatic Epidural Spinal Cord Compression: Results of the Prospective Multicenter AOSpine Study

PURPOSE

Although surgery is used increasingly as a strategy to complement treatment with radiation and chemotherapy in patients with metastatic epidural spinal cord compression (MESCC), the impact of surgery on health-related quality of life (HRQoL) is not well established. We aimed to prospectively evaluate survival, neurologic, functional, and HRQoL outcomes in patients with MESCC who underwent surgical management.

PATIENTS AND METHODS

One hundred forty-two patients with a single symptomatic MESCC lesion who were treated surgically were enrolled onto a prospective North American multicenter study and were observed at least up to 12 months. Clinical data, including Brief Pain Inventory, ASIA (American Spinal Injury Association) impairment scale, SF-36 Short Form Health Survey, Oswestry Disability Index, and EuroQol 5 dimensions (EQ-5D) scores, were obtained preoperatively, and at 6 weeks and 3, 6, 9, and 12 months postoperatively.

RESULTS

Median survival time was 7.7 months. The 30-day and 12-month mortality rates were 9% and 62%, respectively. There was improvement at 6 months postoperatively for ambulatory status (McNemar test, P < .001), lower extremity and total motor scores (Wilcoxon signed rank test, P < .001), and at 6 weeks and 3, 6, and 12 months for Oswestry Disability Index, EQ-5D, and pain interference (paired t test, P < .013). Moreover, at 3 months after surgery, the ASIA impairment scale grade was improved (Stuart-Maxwell test P = .004). SF-36 scores improved postoperatively in six of eight scales. The incidence of wound complications was 10% and 2 patients required a second surgery (screw malposition and epidural hematoma).

CONCLUSION

Surgical intervention, as an adjunct to radiation and chemotherapy, provides immediate and sustained improvement in pain, neurologic, functional, and HRQoL outcomes, with acceptable risks in patients with a focal symptomatic MESCC lesion who have at least a 3 month survival prognosis.

A systematic review of clinical and surgical predictors of complications following surgery for degenerative cervical myelopathy

OBJECTIVE

Although generally safe and effective, surgery for the treatment of cervical spondylotic myelopathy (CSM) is associated with complications in 11%-38% of patients. Several predictors of postoperative complications have been proposed but few are used to detect high-risk patients. A standard approach to identifying "at-risk" patients would improve surgeons' ability to prevent and manage these complications. The authors aimed to compare the complication rates between various surgical procedures used to treat CSM and to identify patient-specific, clinical, imaging, and surgical predictors of complications.

METHODS

The authors conducted a systematic review of the literature and searched MEDLINE, MEDLINE in Process, EMBASE, and Cochrane Central Register of Controlled Trials from 1948 to September 2013. Cohort studies designed to evaluate predictors of complications and intervention studies conducted to compare different surgical approaches were included. Each article was critically appraised independently by 2 reviewers, and the evidence was synthesized according to the principles outlined by the Grading of Recommendation Assessment, Development and Evaluation (GRADE) Working Group.

RESULTS

A total of 5472 citations were retrieved. Of those, 60 studies met the inclusion criteria and were included in the review. These studies included 36 prognostic cohort studies and 28 comparative intervention studies. High evidence suggests that older patients are at a greater risk of perioperative complications. Based on low evidence, other clinical factors such as body mass index, smoking status, duration of symptoms, and baseline severity score, are not predictive of complications. With respect to surgical factors, low to moderate evidence suggests that estimated blood loss, surgical approach, and number of levels do not affect rates of complications. A longer operative duration (moderate evidence), however, is predictive of perioperative complications and a 2-stage surgery is related to an increased risk of major complications (high evidence). In terms of surgical techniques, higher rates of neck pain were found in patients undergoing laminoplasty compared with anterior spinal fusion (moderate evidence). In addition, with respect to laminoplasty techniques, there was a lower incidence of C-5 palsy in laminoplasty with concurrent foraminotomy compared with nonforaminotomy (low evidence).

CONCLUSIONS

The current review suggests that older patients are at a higher risk of perioperative complications. A longer operative duration and a 2-stage surgery both reflect increased case complexity and can indirectly predict perioperative complications.

Prevalence of Klippel-Feil Syndrome in a Surgical Series of Patients with Cervical Spondylotic Myelopathy: Analysis of the Prospective, Multicenter AOSpine North America Study

Study Design Prospective study. Objective To evaluate the prevalence of Klippel-Feil syndrome (KFS) in a prospective data set of patients undergoing surgical treatment for cervical spondylotic myelopathy (CSM) and to evaluate if magnetic resonance imaging (MRI) features in patients with KFS are more pronounced than those of non-KFS patients with CSM. Methods A retrospective analysis of baseline MRI data from the AOSpine prospective and multicenter CSM-North American study was conducted. All the patients presented with at least one clinical sign of myelopathy and underwent decompression surgery. The MRIs and radiographs were reviewed by three investigators. The clinical and imaging findings were compared with patients without KFS but with CSM. Results Imaging analysis discovered 5 of 131 patients with CSM (∼3.82%) had single-level congenital fusion of the cervical spine. The site of fusion differed for all the patients. One patient underwent posterior surgery and four patients received anterior surgery. Postoperative follow-up was available for four of the five patients with KFS and indicated stable or improved functional status. All five patients demonstrated pathologic changes of adjacent segments and hyperintensity signal changes in the spinal cord on T2-weighted MRI. Multiple MRI features, most notably maximum canal compromise (p = 0.05) and T2 signal hyperintensity area (p = 0.05), were worse in patients with CSM and KFS. Conclusions The high prevalence of KFS in our surgical series of patients with CSM may serve as an indication that these patients are prone to increased biomechanical use of segments adjacent to fused vertebra. This supposition is supported by a tendency of patients with KFS to present with more extensive MRI evidence of degeneration than non-KFS patients with CSM.