Determining the time frame of maximum clinical improvement in surgical decompression for cervical spondylotic myelopathy when stratified by preoperative myelopathy severity: a cervical Quality Outcomes Database study

Connor BerlinDepartment of Neurosurgery, University of Virginia, Charlottesville, Virginia;

Search for other papers by Connor Berlin in
jns
Google Scholar
PubMed
Close
 MD
,
Alexandria C. MarinoDepartment of Neurosurgery, University of Virginia, Charlottesville, Virginia;

Search for other papers by Alexandria C. Marino in
jns
Google Scholar
PubMed
Close
 MD, PhD
,
Praveen V. MummaneniDepartment of Neurological Surgery, University of California, San Francisco, California;

Search for other papers by Praveen V. Mummaneni in
jns
Google Scholar
PubMed
Close
 MD, MBA
,
Juan UribeDepartment of Neurosurgery, Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, Arizona;

Search for other papers by Juan Uribe in
jns
Google Scholar
PubMed
Close
 MD
,
Luis M. TumialánDepartment of Neurosurgery, Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, Arizona;

Search for other papers by Luis M. Tumialán in
jns
Google Scholar
PubMed
Close
 MD
,
Jay TurnerDepartment of Neurosurgery, Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, Arizona;

Search for other papers by Jay Turner in
jns
Google Scholar
PubMed
Close
 MD, PhD
,
Michael Y. WangDepartment of Neurological Surgery, University of Miami, Miami, Florida;

Search for other papers by Michael Y. Wang in
jns
Google Scholar
PubMed
Close
 MD
,
Paul ParkDepartment of Neurological Surgery, University of Michigan, Ann Arbor, Michigan;

Search for other papers by Paul Park in
jns
Google Scholar
PubMed
Close
 MD
,
Erica F. BissonDepartment of Neurosurgery, University of Utah, Salt Lake City, Utah;

Search for other papers by Erica F. Bisson in
jns
Google Scholar
PubMed
Close
 MD, MPH
,
Mark ShaffreyDepartment of Neurosurgery, University of Virginia, Charlottesville, Virginia;

Search for other papers by Mark Shaffrey in
jns
Google Scholar
PubMed
Close
 MD
,
Oren GottfriedDepartment of Neurosurgery, Division of Spine, Duke University Medical Center, Durham, North Carolina;

Search for other papers by Oren Gottfried in
jns
Google Scholar
PubMed
Close
 MD
,
Khoi D. ThanDepartment of Neurosurgery, Division of Spine, Duke University Medical Center, Durham, North Carolina;

Search for other papers by Khoi D. Than in
jns
Google Scholar
PubMed
Close
 MD
,
Kai-Ming FuDepartment of Neurological Surgery, Weill Cornell Medicine, New York City, New York;

Search for other papers by Kai-Ming Fu in
jns
Google Scholar
PubMed
Close
 MD, PhD
,
Kevin FoleyDepartment of Neurosurgery, University of Tennessee, Memphis, Tennessee;

Search for other papers by Kevin Foley in
jns
Google Scholar
PubMed
Close
 MD
,
Andrew K. ChanDepartment of Neurological Surgery, University of California, San Francisco, California;

Search for other papers by Andrew K. Chan in
jns
Google Scholar
PubMed
Close
 MD
,
Mohamad BydonDepartment of Neurosurgery, Mayo Clinic Neuro-Informatics Lab, Mayo Clinic, Rochester, Minnesota;

Search for other papers by Mohamad Bydon in
jns
Google Scholar
PubMed
Close
 MD
,
Mohammed Ali AlviDepartment of Neurosurgery, Mayo Clinic Neuro-Informatics Lab, Mayo Clinic, Rochester, Minnesota;

Search for other papers by Mohammed Ali Alvi in
jns
Google Scholar
PubMed
Close
 MBBS, MS
,
Cheerag UpadhyayaMarion Bloch Neuroscience Institute’s Spine Program, Saint Luke Health System, Kansas City, Missouri;

Search for other papers by Cheerag Upadhyaya in
jns
Google Scholar
PubMed
Close
 MD
,
Domagoj CoricCarolina Neurosurgery & Spine Associates, Carolinas Medical Center, Charlotte, North Carolina;

Search for other papers by Domagoj Coric in
jns
Google Scholar
PubMed
Close
 MD
,
Anthony AsherCarolina Neurosurgery & Spine Associates, Carolinas Medical Center, Charlotte, North Carolina;

Search for other papers by Anthony Asher in
jns
Google Scholar
PubMed
Close
 MD
,
Eric A. PottsGoodman Campbell Brain and Spine, Indianapolis, Indiana; and

Search for other papers by Eric A. Potts in
jns
Google Scholar
PubMed
Close
 MD
,
John KnightlyAtlantic Neurosurgical Specialists, Altair Health Spine & Wellness Center, Morristown, New Jersey

Search for other papers by John Knightly in
jns
Google Scholar
PubMed
Close
 MD
,
Scott MeyerAtlantic Neurosurgical Specialists, Altair Health Spine & Wellness Center, Morristown, New Jersey

Search for other papers by Scott Meyer in
jns
Google Scholar
PubMed
Close
 MD
, and
Avery BuchholzDepartment of Neurosurgery, University of Virginia, Charlottesville, Virginia;

Search for other papers by Avery Buchholz in
jns
Google Scholar
PubMed
Close
 MD, MPH
Free access

OBJECTIVE

While surgical decompression is an important treatment modality for cervical spondylotic myelopathy (CSM), it remains unclear if the severity of preoperative myelopathy status affects potential benefit from surgical intervention and when maximum postoperative improvement is expected. This investigation sought to determine if retrospective analysis of prospectively collected patient-reported outcomes (PROs) following surgery for CSM differed when stratified by preoperative myelopathy status. Secondary objectives included assessment of the minimal clinically important difference (MCID).

METHODS

A total of 1151 patients with CSM were prospectively enrolled from the Quality Outcomes Database at 14 US hospitals. Baseline demographics and PROs at baseline and 3 and 12 months were measured. These included the modified Japanese Orthopaedic Association (mJOA) score, Neck Disability Index (NDI), quality-adjusted life-years (QALYs) from the EQ-5D, and visual analog scale from the EQ-5D (EQ-VAS). Patients were stratified by preoperative myelopathy severity using criteria established by the AO Spine study group: mild (mJOA score 15–17), moderate (mJOA score 12–14), or severe (mJOA score < 12). Univariate analysis was used to identify demographic variables that significantly varied between myelopathy groups. Then, multivariate linear regression and linear mixed regression were used to model the effect of severity and time on PROs, respectively.

RESULTS

For NDI, EQ-VAS, and QALY, patients in all myelopathy cohorts achieved significant, maximal improvement at 3 months without further improvement at 12 months. For mJOA, moderate and severe myelopathy groups demonstrated significant, maximal improvement at 3 months, without further improvement at 12 months. The mild myelopathy group did not demonstrate significant change in mJOA score but did maintain and achieve higher PRO scores overall when compared with more advanced myelopathy cohorts. The MCID threshold was reached in all myelopathy cohorts at 3 months for mJOA, NDI, EQ-VAS, and QALY, with the only exception being mild myelopathy QALY at 3 months.

CONCLUSIONS

As assessed by statistical regression and MCID analysis, patients with cervical myelopathy experience maximal improvement in their quality of life, neck disability, myelopathy score, and overall health by 3 months after surgical decompression, regardless of their baseline myelopathy severity. An exception was seen for the mJOA score in the mild myelopathy cohort, improvement of which may have been limited by ceiling effect. The data presented here will aid surgeons in patient selection, preoperative counseling, and expected postoperative time courses.

ABBREVIATIONS

ASA = American Society of Anesthesiologists; CSM = cervical spondylotic myelopathy; EQ-VAS = EQ-5D visual analog scale; MCID = minimal clinically important difference; mJOA = modified Japanese Orthopaedic Association; NASS = North American Spine Society; NDI = Neck Disability Index; PRO = patient-reported outcome; QALY = quality-adjusted life-year; QOD = Quality Outcomes Database.

OBJECTIVE

While surgical decompression is an important treatment modality for cervical spondylotic myelopathy (CSM), it remains unclear if the severity of preoperative myelopathy status affects potential benefit from surgical intervention and when maximum postoperative improvement is expected. This investigation sought to determine if retrospective analysis of prospectively collected patient-reported outcomes (PROs) following surgery for CSM differed when stratified by preoperative myelopathy status. Secondary objectives included assessment of the minimal clinically important difference (MCID).

METHODS

A total of 1151 patients with CSM were prospectively enrolled from the Quality Outcomes Database at 14 US hospitals. Baseline demographics and PROs at baseline and 3 and 12 months were measured. These included the modified Japanese Orthopaedic Association (mJOA) score, Neck Disability Index (NDI), quality-adjusted life-years (QALYs) from the EQ-5D, and visual analog scale from the EQ-5D (EQ-VAS). Patients were stratified by preoperative myelopathy severity using criteria established by the AO Spine study group: mild (mJOA score 15–17), moderate (mJOA score 12–14), or severe (mJOA score < 12). Univariate analysis was used to identify demographic variables that significantly varied between myelopathy groups. Then, multivariate linear regression and linear mixed regression were used to model the effect of severity and time on PROs, respectively.

RESULTS

For NDI, EQ-VAS, and QALY, patients in all myelopathy cohorts achieved significant, maximal improvement at 3 months without further improvement at 12 months. For mJOA, moderate and severe myelopathy groups demonstrated significant, maximal improvement at 3 months, without further improvement at 12 months. The mild myelopathy group did not demonstrate significant change in mJOA score but did maintain and achieve higher PRO scores overall when compared with more advanced myelopathy cohorts. The MCID threshold was reached in all myelopathy cohorts at 3 months for mJOA, NDI, EQ-VAS, and QALY, with the only exception being mild myelopathy QALY at 3 months.

CONCLUSIONS

As assessed by statistical regression and MCID analysis, patients with cervical myelopathy experience maximal improvement in their quality of life, neck disability, myelopathy score, and overall health by 3 months after surgical decompression, regardless of their baseline myelopathy severity. An exception was seen for the mJOA score in the mild myelopathy cohort, improvement of which may have been limited by ceiling effect. The data presented here will aid surgeons in patient selection, preoperative counseling, and expected postoperative time courses.

In Brief

Researchers set out to determine if retrospective analysis of prospectively collected patient-reported outcomes (PROs) following surgery for cervical spondylotic myelopathy (CSM) differed when stratified by preoperative myelopathy status. Three months after surgical decompression for CSM appears to be an adequate time to achieve maximum improvement in PROs in most patients. This study adds value by providing new insight and more accurate time resolution into how and when patients can be expected to achieve clinical improvement following surgical decompression for CSM and provides the surgeon and patient with more accurate information for counseling and expected postoperative recovery time course.

Cervical spondylotic myelopathy (CSM) is the most common form of spinal cord disability in North America, with prevalence expected to continue increasing over the next decade.1 As a blanket term, CSM describes degeneration of the cervical spinal bony anatomy that results in canal narrowing, which leads to spinal cord compression and neurological impairment.1,2 Canal narrowing can be due to cervical spondylosis, ossification of the posterior longitudinal ligament, ossification of the ligamentum flavum, degenerative disc disease, or a combination of these pathologies, although other potential causes are possible.1,2 These degenerative processes can lead to anatomical instability, changes in alignment, narrowing of the spinal canal, and subsequently, cervical myelopathy. Ultimately, for patients in whom nonoperative measures fail, definitive treatment is surgical decompression of the cervical spine.3

Decompressive surgery for CSM is performed either anteriorly or posteriorly.2,4 Anterior approaches include but are not limited to anterior cervical discectomy and fusion and anterior cervical corpectomy and fusion.5 Common posterior approaches include laminectomy with posterior spinal fusion or cervical laminoplasty.6,7 Important factors that influence the decision for type of approach include sagittal alignment, location of the compression, number of compressed levels, amount of instability or subluxation, type of pathology, bone quality, and surgeon experience.2

Although traditionally reserved for moderate to severe myelopathy, surgery is now increasingly offered to those with mild myelopathy.1,3 While surgical decompression is an important treatment modality for CSM, it is unclear at what time point patients can expect maximal benefit from surgical intervention postoperatively. While other studies have attempted to determine the time point of maximum benefit, they have been limited by small sample size, lack of comparison to minimal clinically important difference (MCID), or temporal resolution.810

Here, we used the NeuroPoint Alliance Quality Outcomes Database (QOD), a national multicenter registry that prospectively enrolls patients undergoing elective spine surgery, to address these questions. Specifically, we sought to determine if retrospective analysis of prospectively collected patient-reported outcomes (PROs) following surgery for CSM differed when stratified by preoperative myelopathy status and to determine when patients experience maximal clinical benefit from surgery. It should be noted that our group has previously published on this work but only regarding the modified Japanese Orthopaedic Association (mJOA) score, which is a PRO measure known to be limited by ceiling effect.11 The present study is an expansion of this work, with analysis of other PROs more reflective of a patient’s overall health state and postoperative improvement (beyond myelopathy score). Importantly, we evaluate our results in the context of clinically meaningful outcomes via MCID analysis, which was not done previously.

Methods

Study Design

This study was a retrospective analysis of prospectively collected data in patients with CSM who were registered in the NeuroPoint Alliance QOD. The QOD is a prospectively collected registry established to define risk-adjusted morbidity and clinical outcomes following common surgical spine procedures.12 The cervical database was initiated in 2013 and includes 175 hospitals, 613 surgeons, and more than 25,000 cases.12 All surgical cases represented in this study were initiated from January 2016 to December 2018 and were pulled from a select group of 14 US hospitals.12 This study protocol was approved by the University of Virginia institutional review board.

A total of 1151 patients from January 1, 2016, through December 31, 2018, with CSM undergoing elective surgery were prospectively enrolled in the study. Inclusion criteria were patients for whom baseline PRO data were available, age ≥ 18 years, and a primary diagnosis of CSM. Exclusion criteria were diagnosis of fracture, neurological paralysis due to preexisting spine disease or injury, tumor, traumatic dislocation, deformity, spinal infection, and age < 18 years.

Patients with missing values for the regression being fit were completely omitted. No imputation for missing values was performed. An average of 15% of patients were omitted for incomplete data or lost to follow-up at 3 months, and an average of 31% of patients were omitted at 12 months. This follow-up rate is comparable to those of previous studies.10,13,14

Patient Demographics

Patient baseline demographics included the following: age, sex, primary versus revision surgery, BMI, insurance status, past medical history (including smoking, diabetes mellitus, coronary artery disease, peripheral vascular disease, anxiety, depression, arthritis, chronic obstructive pulmonary disease, Parkinson’s disease, and multiple sclerosis), ambulation status, symptom duration, ethnicity, race, education level, employment status (i.e., if unemployed due to disability), American Society of Anesthesiologists (ASA) class, and surgical approach (anterior vs posterior).

Patient-Reported Outcomes

Selected PROs comprised previously validated and widely used clinical outcome measures and included the following: the mJOA score for severity of myelopathy,15,16 Neck Disability Index (NDI) for neck specific disability,17 the EQ-5D health survey for calculating health utility, a measure of overall quality of life (referred to in this study as quality-adjusted life-years [QALYs]), and EQ-5D visual analog scale (EQ-VAS) for health status.18,19 These PROs were collected at baseline and following surgical interventions for CSM at 3 and 12 months postoperatively.

The mJOA scale ranges from 0 to 18, with lower scores indicating increasing severity of myelopathy.15,16 The total score is generated from summing subscores from upper-extremity motor function, lower-extremity motor function, and urinary function assessments. The NDI ranges from 0 to 100, with higher scores representing worse function. The total score is generated from summing and then doubling subscores from 10 sections: pain intensity, personal care, lifting, reading, headaches, concentration, work, driving, sleeping, and recreation.17 The EQ-5D preference-based health state is used to generate the QALY, which ranges from −0.1 to 1.0. The QALY calculation incorporates health-related quality of life and survival, with higher scores indicating improved health states.18,19 The EQ-VAS is taken from the EQ-5D questionnaire. It is a visual analog scale ranging from 0 to 100, with 0 representing “worst imaginable health state” and 100 representing “best imaginable health state.”18,19

Statistical Analysis

To determine how postoperative PROs differed when stratified by preoperative myelopathy status, patients were stratified by myelopathy status established by the AO Spine study group: mild (mJOA score 15–17), moderate (mJOA score 12–14), or severe (mJOA score < 12).15 All statistical analysis was conducted using R (R Project for Statistical Computing). Univariate tests (ANOVA for continuous variables or the chi-square test for categorical variables) were used to identify demographic variables that significantly varied between myelopathy groups. To examine whether PROs differed between severity groups at each time point (baseline, 3 months, and 12 months), a multivariate linear regression model was fit for data from each time point that included as regressors all univariate significant demographic variables as well as dummy variables designating mild and severe myelopathy (such that a significant β weight for either of these represented a difference in PROs compared with PROs in patients with moderate myelopathy). To examine whether PROs changed significantly as a function of time for patients with a particular myelopathy severity, a linear mixed-model regression was fit for each severity designation; this included subject intercept as a random effect as well as main effects for univariate significant demographic variables as well as dummy variables designating baseline and 12-month values (such that a significant β weight for each of these variables represented a difference in PRO from those measured at the 3-month time point). Time courses were modeled in this way to both determine whether significant improvement occurred by the 3-month time point and determine whether additional significant improvement occurred by 12 months or whether the 3-month time point represented maximal improvement.

MCID

The MCID has been described by others as a method to determine the threshold for clinically significant changes in PROs.1922 Since statistically significant changes in PROs may not necessarily be clinically meaningful to the patient, the MCID attempts to address this concern by defining a threshold at which clinically significant change occurs. We based the MCID analysis on a series of previously published work that demonstrated that the anchor-based minimum detectable change method is most appropriate (both statically and clinically) for determining MCID when compared with other methods such as the average change approach, the change difference approach, or receiver operating characteristic curve analysis.19,23 We included separately calculated cutoff thresholds for mild, moderate, and severe myelopathy, as it is known that MCID values vary with myelopathy severity.21

Our method utilizes the North American Spine Society (NASS) patient satisfaction index as an anchor to define responders and nonresponders when determining MCID. Responders were defined as patients with a 3-month NASS score of 1 or 2 (1, “The treatment met my expectations”; 2, “I did not improve as much as I had hoped, but I would undergo the same treatment for the same outcome”), and nonresponders were defined as patients with an NASS score of 3 or 4 (3, “I did not improve as much as I had hoped, and I would not undergo the same treatment for the same outcome”; 4, “I am the same or worse than before treatment”), which is common practice.24,25 We focused on the 3-month time point and used 3-month NASS scores in this MCID calculation because that is when patient response to treatment was deemed maximal according to our initial statistical analysis. We did not calculate MCID values at the 12-month time point (see Discussion for further details).

The MCID for each PRO was defined as the upper value of the 95% confidence interval for the change in that PRO seen in the cohort of nonresponders (NASS score 3 or 4) from baseline to 3 months. MCIDs were calculated for each PRO and severity (mild, moderate, or severe) cohort.19

Results

A total of 1151 patients from January 1, 2016, through December 31, 2018, with CSM undergoing elective surgery were prospectively enrolled in the QOD at 14 US hospitals. All PRO averages are summarized in Table 1. Analysis of baseline patient demographics revealed significant differences in BMI, insurance status, past medical history, race, employment status, ASA class, and surgical approach when patients were stratified by myelopathy status (p < 0.05) (Table 2). For example, patients with severe myelopathy were more likely to be smokers; have diabetes mellitus, coronary artery disease, depression, arthritis, chronic obstructive pulmonary disease, or multiple sclerosis; be unemployed due to disability; have difficulty with ambulation; and be in a higher ASA class (Table 2).

TABLE 1.

Mean PROs stratified by myelopathy severity at baseline, 3 months, and 12 months

Time PointMean (no. of patients)
Mild MyelopathyModerate MyelopathySevere Myelopathy
mJOAmJOA
 Baseline15.4 (252)13.0 (454)9.1 (445)
 3 mos15.7 (201)*14.4 (384)*12.6 (359)*
 12 mos15.3 (183)14.1 (333)12.5 (311)
NDI
 Baseline28 (252)36 (452)47 (443)
 3 mos17 (206)*22 (398)*28 (367)*
 12 mos14 (180)19 (340)26 (313)
EQ-VAS
 Baseline70 (242)61 (439)52 (434)
 3 mos77 (203)*70 (390)*64 (361)*
 12 mos76 (174)70 (328)66 (294)
QALY
 Baseline0.69 (225)0.59 (415)0.46 (417)
 3 mos0.82 (190)0.74 (383)*0.66 (355)*
 12 mos0.82 (172)0.74 (320)0.66 (295)

Patients were stratified by myelopathy criteria established by the AO Spine study group: mild (mJOA score 15–17), moderate (mJOA score 12–14), or severe (mJOA score < 12).

Results that met the cutoff threshold for MCID analysis at 3 months using NASS scores of 3 and 4 as nonresponders.

TABLE 2.

Baseline demographics of the study patient population

Mild MyelopathyModerate MyelopathySevere Myelopathyp Value*
Mean (SD) age, yrs59.64 (11.71)60.48 (11.43)61.14 (11.78)0.269 (ANOVA)
Male, %54.454.449.70.294
Primary revision, %96.498.097.30.736
Mean (SD) BMI29.1 (6.06)30.5 (6.27)30.4 (6.73)0.016 (ANOVA)
Payer, %<0.001
 Uninsured0.41.81.3
 Medicare29.839.642.7
 Medicaid5.25.39.4
 VA0.82.23.6
 Private63.951.142.9
Past medical history, %
 Smoker12.717.021.30.014
 DM14.322.224.70.005
 CAD5.28.812.80.003
 PVD1.64.63.80.116
 Anxiety16.317.420.70.273
 Depression15.120.027.4<0.001
 Arthritis23.028.033.00.017
 COPD4.46.29.70.02
 Parkinson’s disease2.00.70.40.445
 MS0.41.12.70.038
Ambulation, %<0.001
 Independent96.089.265.8
 w/ assistance3.610.629.9
 Nonambulatory0.40.24.3
Symptom duration, %0.112
 <3 mos13.913.211.7
 3–12 mos37.732.427.9
 >12 mos38.944.949.7
Ethnicity, %0.118
 Hispanic/Latino2.82.64.0
 Non-Hispanic/Latino90.493.892.1
 No answer6.83.53.8
Race, %
 Native American0.40.20.70.581
 Asian2.00.90.70.240
 Black10.711.721.6<0.001
 Pacific Islander1.20.20.20.119
 White77.081.570.60.001
Education level, %
 <High school4.05.96.30.075
 High school34.936.638.7
 2-yr degree13.917.219.8
 4-yr degree25.422.719.1
 Postcollege17.514.110.6
Unemployed because of disability4.010.615.50.003
ASA class, %<0.001
 I4.41.31.3
 II56.746.533.3
 III32.543.854.8
 IV0.41.82.5
Surgical approach, %0.003
 Posterior24.629.736.6
 Anterior75.470.363.4

CAD = coronary artery disease; COPD = chronic obstructive pulmonary disease; DM = diabetes mellitus; MS = multiple sclerosis; PVD = peripheral vascular disease; VA = Veterans Affairs.

Boldface type indicates statistical significance.

Chi-square test unless specified otherwise.

For mJOA score, patients in the mild myelopathy cohort did not demonstrate significant change at 3 or 12 months postoperatively when compared with baseline (βbaseline = −0.13; β12mo = −0.20; both p > 0.05) (Fig. 1). However, both moderate and severe myelopathy cohorts demonstrated maximal improvement in average mJOA score at 3 months postoperatively (moderate: βbaseline = −1.016, p < 0.001; β12mo = −0.26, p > 0.05; severe: βbaseline = −3.28, p < 0.001; β12mo = 0.06, p > 0.05) (Fig. 1). Additionally, at each time point, the intergroup mJOA score differed significantly between cohorts (baseline: βsevere = −3.76, p < 0.001; βmild = 2.42, p < 0.001; 3-month: βsevere = −1.38, p < 0.001; βmild = 1.30, p < 0.001; 12-month: βsevere = −1.13, p < 0.001; βmild = 1.37, p < 0.001), indicating that although the cohorts had an improvement in their mJOA scores as time went on, they remained distinct (patients with mild myelopathy had higher mJOA scores than those with moderate myelopathy at each time point, patients with moderate myelopathy had higher mJOA scores than those with severe myelopathy at each time point) and thus did not recover to the same mJOA scores (Fig. 1). Although the mild myelopathy cohort did not demonstrate significant improvement in mJOA score, they retained their significantly higher mJOA score at 3 and 12 months postoperatively when compared with more severe myelopathy groups (Fig. 1).

FIG. 1.
FIG. 1.

The mJOA score for patients at baseline (preoperatively) and 3 and 12 months after surgery for CSM. Patients are stratified by myelopathy criteria established by the AO Spine study group: mild (mJOA score 15–17), moderate (mJOA score 12–14), or severe (mJOA score < 12). Of note, baseline groups differ significantly by myelopathy status. Moderate and severe myelopathy groups are significantly improved at 3 months from baseline. Mild myelopathy maintains a significantly higher mJOA score after surgical intervention when compared with moderate and severe myelopathy. Error bars for standard error of the mean are shown but, in some cases, may be smaller than the actual designated shape. Significance codes are used to denote intra- and intergroup significance. ***p < 0.001. Figure is available in color online only.

For NDI, mild myelopathy patients achieved significant improvement in average NDI at 3 months and continued to improve at 12 months (βbaseline = 8.93, p < 0.001; β12mo = −5.02, p < 0.01) (Fig. 2). Both moderate and severe myelopathy patients achieved maximal NDI score improvement at 3 months postoperatively without further improvement at 12 months (moderate: βbaseline = 13.48, p < 0.001; β12mo = −2.34, p > 0.05; severe: βbaseline = 19.80, p < 0.001; β12mo = −0.38, p > 0.05) (Fig. 2). Interestingly, at baseline and 12 months, myelopathy cohorts had significantly different NDI scores, but at 3 months NDI scores did not differ among myelopathy cohorts (baseline: βsevere = 10.37, p < 0.001; βmild = −9.02, p < 0.001; 3-month: βsevere = 3.42, p > 0.05; βmild = −3.86, p > 0.05; 12-month: βsevere = 4.47, p < 0.05; βmild = −5.58, p < 0.05) (Fig. 2).

FIG. 2.
FIG. 2.

NDI (%) for patients at baseline (preoperatively) and 3 and 12 months after surgery for CSM. Patients are stratified by myelopathy criteria established by the AO Spine study group. Baseline groups differ significantly by myelopathy status. All severity groups are significantly improved in NDI at 3 months from baseline, with further improvement in the mild myelopathy cohort at 12 months. Error bars for standard error of the mean are shown but, in some cases, may be smaller than the actual designated shape. Significance codes are used to denote intra- and intergroup significance. *p < 0.05; **p < 0.01; ***p < 0.001. Figure is available in color online only.

For EQ-VAS, patients in all myelopathy cohorts achieved maximal improvement at 3 months, without further improvement at 12 months (mild: βbaseline = −7.82, p < 0.01; β12mo = −1.45, p > 0.05; moderate: βbaseline = −8.70, p < 0.001; β12mo = −0.18, p > 0.05; severe: βbaseline = −12.56, p < 0.001; β12mo = 1.47, p > 0.05) (Fig. 3). Regarding time course change, all myelopathy cohorts differed in baseline EQ-VAS (baseline: βsevere = −5.64, p < 0.01; βmild = 8.27, p < 0.01) (Fig. 3). At 3 months, mild and moderate myelopathy differed in EQ-VAS, but the difference between moderate and severe myelopathy was not statistically significant (3-month: βsevere = −3.20, p > 0.05; βmild = 6.52, p < 0.05) (Fig. 3). At 12 months, EQ-VAS was not significantly different among myelopathy cohorts (12-month: βsevere = −0.05, p > 0.05; βmild = 4.71, p > 0.05) (Fig. 3).

FIG. 3.
FIG. 3.

EQ-VAS for patients at baseline (preoperatively) and 3 and 12 months postsurgery for CSM. Patients are stratified by myelopathy criteria established by the AO Spine study group. Baseline groups differ significantly by myelopathy status. All severity groups are significantly improved in EQ-VAS at 3 months from baseline, with no further improvement at 12 months. Mild myelopathy maintains its significantly higher EQ-VAS score at 3 months after surgical intervention when compared with moderate and severe myelopathy. Error bars for standard error of mean are shown but, in some cases, may be smaller than the actual designated shape. Significance codes are used to denote intra- and intergroup significance. *p < 0.05; **p < 0.01; ***p < 0.001. Figure is available in color online only.

For QALYs, patients in all myelopathy cohorts achieved maximal improvement at 3 months without further improvement at 12 months (mild: βbaseline = −0.140, p < 0.001; β12mo = −0.035, p > 0.05; moderate: βbaseline = −0.150, p < 0.001, β12mo = −0.024, p > 0.05; severe: βbaseline = −0.201, p < 0.001; β12mo = 0.007, p > 0.05) (Fig. 4). At the baseline and 3-month time points, myelopathy cohorts differed significantly in their means (baseline: βsevere = −0.093, p < 0.001; βmild = 0.104, p < 0.001; 3-month: βsevere = −0.045, p < 0.05; βmild = 0.090, p < 0.01) (Fig. 4). At 12 months, mild and moderate myelopathy differed significantly by QALY, but not moderate and severe myelopathy cohorts (12-month: βsevere = −0.011, p > 0.05; βmild = 0.064, p < 0.05) (Fig. 4).

FIG. 4.
FIG. 4.

QALYs for patients at baseline (preoperatively) and 3 and 12 months postsurgery for CSM. Patients are stratified by myelopathy criteria established by the AO Spine study group. Baseline groups differ significantly by myelopathy status. All severity groups are significantly improved in QALYs at 3 months from baseline, with no further improvement at 12 months. Mild myelopathy maintains a significantly higher QALY score after surgical intervention when compared with moderate and severe myelopathy. Error bars for standard error of mean are shown but, in some cases, may be smaller than the actual designated shape. Significance codes are used to denote intra- and intergroup significance. *p < 0.05; **p < 0.01; ***p < 0.001. Figure is available in color online only.

MCID values calculated using 3-month NASS scores as an anchor, listed in order for mild, moderate, and severe myelopathy, respectively, were as follows: mJOA MCID = −0.06, 0.86, and 2.48; NDI MCID = −5.5%, −7.3%, and −12.3%; EQ-VAS MCID = 9.6, 0.3, and 4.7; and QALY MCID = 0.14, 0.02, and 0.14. Based on these cutoff values, the MCID threshold was reached in all myelopathy cohorts at 3 months for mJOA, NDI, EQ-VAS, and QALY, with the only exception being mild myelopathy QALY at 3 months (Table 1).

Discussion

To the best of our knowledge, this is the largest retrospective analysis of prospectively collected data on patient-reported surgical outcomes for CSM that includes MCID analysis. Our sample size of 1151 patients is greater than that in previous studies810 and contains the largest North American cohort of CSM patients with outcome data at 12 months (n = 833).10

The significant preoperative differences observed in all PROs across myelopathy severities justify the use of established AO Spine–defined criteria for myelopathy severities (mild myelopathy, mJOA score 15–17; moderate, mJOA score 12–14; severe, mJOA score < 12).15 Our data show that most patients undergoing surgery for CSM—irrespective of their baseline myelopathy severity—can be expected to achieve maximal improvement in their functional disability, neck disability, overall health status, and quality of life by 3 months postoperatively, with an incremental improvement at 12 months seen in the mild myelopathy NDI score (Figs. 14). An exception was in the mild myelopathy cohort mJOA score (but not NDI, EQ-VAS, or QALY scores), which did not reach statistical significance at 3 or 12 months postoperatively.

Lack of improvement in mild myelopathy mJOA score may have been limited by the ceiling effect of the mJOA score, which is previously documented.11 Additionally, in clinical practice, the mJOA score may be less suited for tracking clinical recovery in patients with mild myelopathy, and other PROs may be more sensitive to clinically meaningful change. Another alternative is that patients with a mild mJOA score may take longer to achieve postsurgical improvement in myelopathy status, beyond the 12-month limitation of the present study.26 This notion may be supported by the observation that the mild myelopathy cohort demonstrated continued statistical improvement in their NDI score out to 12 months (Fig. 2). It is important to note that our group is still in the process of collecting 24-month prospective data on these PROs.

Although we did not observe statistical improvement in mJOA score in the mild myelopathy cohort, as mentioned above, there was significant improvement in NDI, EQ-VAS, and QALY at 3 months. Thus, patients with less-severe myelopathy are still likely to have appreciable benefits from surgical intervention (i.e., in quality of life, neck disability, and overall health status). In addition, Figs. 14 demonstrate that the mild myelopathy cohort maintains and achieves a significantly higher level of functioning defined by PROs at 3 and 12 months postoperatively, more so than those with advanced myelopathy states. It is feasible that early operative intervention in mild myelopathy patients may result in preservation of function. Further studies are needed to compare PROs in mild myelopathy cohorts who undergo early operative intervention versus observation alone to determine this.27

Minimal Clinically Important Difference

We calculated our own study-specific MCID values rather than using previously published values. This choice was made in part due to the wide variability of reported MCID thresholds for various etiologies and procedures.19,20,2831 Additionally, MCID values are usually calculated for a homogeneous cohort (e.g., patients undergoing anterior cervical discectomy and fusion for cervical radiculopathy), and each study population undergoing a specific surgery theoretically has unique stressors and pain perceptions before and after surgery that will be elicited in both PROs and satisfaction scores.19 MCID values are overall questionably generalizable, and therefore MCID values were calculated from our unique study population. As mentioned above, patients with an NASS score of 3 or 4 were deemed nonresponders. Our calculated MCID values for mJOA, NDI, EQ-VAS, and QALY are comparable to the findings of previous studies.1921,32

Patient improvement surpassed MCID thresholds in mJOA, NDI, EQ-VAS, and QALY by 3 months after surgery, irrespective of a patient’s baseline myelopathy severity. The mild myelopathy QALY cohort at 3 months was an exception, where the change from baseline QALY was 0.13 but the cutoff MCID threshold was 0.14 (Table 1), and thus threshold was not reached.

Overall, patient improvement was significant but, more importantly, clinically meaningful by 3 months postoperatively. We did not calculate MCID cutoff thresholds at 12 months because our initial statistical analysis (Figs. 14) did not demonstrate further improvements in the majority of PROs at 12 months postoperatively.

Comparison With Previous Studies

As mentioned above, our study sample size of 1151 patients is larger than previous works surveyed810 and contains the largest North American cohort of CSM patients with outcome data at 12 months (n = 833).10 Our MCID analysis demonstrates maximum improvement in patient outcome measures at 3 months postoperatively (except mild myelopathy QALY). While others (e.g., Gulati et al. and Fehlings et al.) have demonstrated statistical improvement in selected PROs at 12 months postoperatively, their analysis did not include a follow-up time point prior to 1 year and did not include an MCID analysis.8,9

When compared with other studies, we believe that there are multiple strengths to our investigation. A recent publication by Karim et al. from a Canadian Prospective Multicenter Study demonstrated clinically meaningful improvement in PROs (e.g., NDI, EQ-5D, and SF-12 Physical Component Summary) among surgically decompressed patients with CSM mostly at 12 months postoperatively (as well as significant improvements in patients at 3 months, such as in NDI score) but employed several previously published definitions of MCID.10 Although some of these findings may complement our current observations, we believe that the use of previously published MCID values, instead of the calculation of population-specific values (as done here), as well as smaller sample size (n = 391 vs 1151), may account for the differences in time to maximal improvement observed.10 Indeed, by the authors’ own admission, a limitation to their investigation was their reliance on previously published MCID values.10

Additionally, this study is an expansion of previous work, which assessed postoperative improvement in mJOA score (not other PROs) in CSM patients at 3 and 12 months postoperatively, without an MCID analysis.11 In that study, as here, we demonstrate that most patients appear to experience maximal improvement from baseline to 3 months, regardless of baseline preoperative myelopathy severity.11

Patient Counseling

The observation of relatively maximal improvement in PROs at 3 months may aid surgeons in determining whether surgical intervention for CSM has been deemed successful by the patient. If improvement is not observed by patients in the immediate postoperative period, the 3-month time point would appear to be an adequate reference to counsel patients on when to reasonably expect improvement. This observation is also useful in managing patient expectations preoperatively, specifically that postoperative improvement may be expected around 3 months. Having this defined time course of recovery can help surgeons decide how much time is adequate to wait and observe patient recovery and whether further interventions may be needed. Of course, there are exceptions in patients with milder myelopathy, in which case change in functional disability per mJOA criteria may be harder to determine for the abovementioned reasons. Nonetheless, even these patients may benefit from surgical intervention since they were shown to achieve and maintain higher PRO scores at 3 and 12 months postoperatively, demonstrating likely preservation of neurological function from cervical decompression. Although this study suggests that clinical improvement is not expected after 12 months, we are currently in the process of collecting 24-month time point data on this.

Regarding how the severity of preoperative myelopathy status affects potential benefit from surgical intervention, it appears that all cohorts (mild, moderate, and severe myelopathy patients), despite differing significantly in their baseline mJOA, NDI, EQ-VAS, and QALY scores, will benefit from surgical intervention. It is unclear whether patients in the stratified myelopathy cohorts achieve the same level of recovery, as intergroup differences were or were not significantly different based on the time point and PRO measured (Figs. 14). Nonetheless, the observation of improvement even in the moderate and severe myelopathy cohorts is important, as patients with advanced myelopathy may be thought to have more irreversible scarring and neurological damage.33 Although we did not assess how preoperative myelopathy duration affects potential recovery, our data clearly demonstrate that there is room for clinical improvement from surgical decompression for CSM.

Limitations

There are several study limitations. Bias in PROs was minimized by using standardized questionnaires for mJOA, EQ-5D, and NDI administered by trained providers. Our study is limited by temporal resolution, as data were only collected at baseline and 3 and 12 months postoperatively. Although on average 3 months was adequate to observe maximum clinical improvement from surgery, this reference may have been different if there were additional time points. As mentioned above, we are currently in the process of collecting 24-month data. Additionally, multi- and univariate analyses were used where appropriate to control for demographic factors, but there are potentially other covariates that exist that were not recorded or controlled for. Finally, the lack of statistical improvement in the mild myelopathy cohort mJOA score may be limited by ceiling effect. Since the mild myelopathy cohort was defined as mJOA scores 15–17 and the upper limit of the test is 18, detection of statistical improvement may have been limited by the sensitivity of the clinical questionnaire.

Conclusions

Using stratification by myelopathy severity, we observed that patients undergoing surgical decompression for CSM can experience maximum improvement in their quality of life, neck disability, functional disability, and overall health by 3 months postoperatively, as assessed by statistical regression and MCID analyses. This improvement is observed regardless of a patient’s baseline myelopathy severity. An exception was seen in the mild myelopathy cohort, which demonstrated MCID improvement at 3 months in all PROs but did not demonstrate significant improvement in mJOA score when only assessed by statistical analysis. The time course of improvement in mJOA score for mild myelopathic patients may be constrained by mJOA ceiling effect and/or the 12-month time limitation of this study. It is important to note that there were incremental improvements in patients with mild myelopathy at 12 months (specifically, NDI score), and this cohort was theoretically able to maintain baseline higher functional status from operative intervention when compared with more advanced myelopathy states. The data presented here will aid surgeons in patient selection, preoperative counseling, and expected postoperative time courses.

Acknowledgments

We thank Marieke Jones, PhD, at the University of Virginia Health Sciences Library for statistical consultation.

Disclosures

Dr. Mummaneni: consultant for DePuy Spine, Globus Medical, and Stryker; royalties from DePuy Spine, Thieme Publishing, and Springer Publishing; shareholder in Spinicity/ISD; and grants/funding from AO Spine (spine fellowship grant), ISSG (MIS Deformity), NREF (QOD), PCORI (CSM-S Trial), Alan and Jacqueline Stuart Spine Outcomes Center (SLIP-II), Joan O’Reilly Endowed Professorship, and NIH/NIAMS (UCSF REACH). Dr. Uribe: consultant for NuVasive, SI Bone, and Viseon; and royalties from NuVasive and SI Bone. Dr. Turner: consultant for NuVasive, SeaSpine, and ATEC; royalties from SeaSpine; and support of non–study-related clinical or research effort from NuVasive and SeaSpine. Dr. Wang: consultant for DePuy Synthes, Spineology, Stryker, NuVasive, and Surgalign; and shareholder in ISD, Kinesiometrics, and Medical Device Partners. Dr. Park: consultant for Globus, NuVasive, DePuy Synthes, and Accelus; royalties from Globus; and non–study-related grant support: Depuy Synthes, ISSG, Cerapedics, and SI Bone. Dr. Bisson: stock ownership in nView and Mirus; consultant for Stryker, Medtronic, and Proprio; direct stock ownership in Proprio; and grant support from PCORI and NREF. Dr. Gottfried: royalties from Pioneer Medical, Inc.; and consultant for Medtronic. Dr. Than: consultant for Bioventus, DePuy Synthes, and Integrity Implants. Dr. Fu: consultant for J&J. Dr. Foley: consultant for Medtronic; royalties from Medtronic; shareholder in Accelus, Companion Spine, Discgenics, DuraStat, Medtronic, NuVasive, Practical Navigation, RevBio, SpineWave, Tissue Differentiation Intelligence, Triad Life Sciences, True Digital Surgery, and Vori Health; patent holder for Discgenics, Medtronic, and NuVasive; and board of directors for Discgenics, DuraStat, RevBio, Tissue Differentiation Intelligence, Triad Life Sciences, and True Digital Surgery. Dr. Chan: non–study-related clinical or research effort from Orthofix. Dr. Coric: consultant for SpineWave, Medtronic, Globus Medical, Integrity Implants, Premia Spine, Aesculap, and NuVasive; royalties from SpineWave, Medtronic, Globus Medical, Stryker, and Integrity Implants; stock options in SpineWave, Pressio, Premia Spine, and 3Spine. Dr. Potts: consultant and royalties from Medtronic. Dr. Buchholz: consultant for Siemens, Alphatec, and Medtronic.

Author Contributions

Conception and design: Uribe, Tumialan, Turner, Wang, Park, Bisson, Shaffrey, Gottfried, Than, Fu, Foley, Chan, Bydon, Alvi, Upadhyaya, Coric, Asher, Potts, Knightly, Meyer, Buchholz. Acquisition of data: Mummaneni, Uribe, Tumialan, Turner, Wang, Park, Bisson, Shaffrey, Gottfried, Than, Fu, Foley, Chan, Bydon, Alvi, Upadhyaya, Coric, Asher, Potts, Knightly, Meyer, Buchholz. Analysis and interpretation of data: Berlin, Marino. Drafting the article: Berlin, Marino, Turner, Wang, Bisson, Gottfried, Buchholz. Critically revising the article: Berlin, Mummaneni, Uribe, Tumialan, Turner, Wang, Park, Bisson, Shaffrey, Gottfried, Than, Fu, Chan, Bydon, Upadhyaya, Buchholz. Reviewed submitted version of manuscript: Berlin, Mummaneni, Uribe, Tumialan, Park, Bisson, Shaffrey, Gottfried, Than, Fu, Chan, Bydon, Upadhyaya, Buchholz. Approved the final version of the manuscript on behalf of all authors: Berlin. Statistical analysis: Marino. Administrative/technical/material support: Berlin. Study supervision: Bisson, Buchholz.

Supplemental Information

Previous Presentations

Portions of this work were presented orally at the Spine Summit 2021, AANS/CNS Joint Section on Disorders of the Spine and Peripheral Nerves, San Diego, California, July 28–31, 2021.

References

  • 1

    Kalsi-Ryan S, Karadimas SK, Fehlings MG. Cervical spondylotic myelopathy: the clinical phenomenon and the current pathobiology of an increasingly prevalent and devastating disorder. Neuroscientist. 2013;19(4):409421.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 2

    Nouri A, Tetreault L, Singh A, Karadimas SK, Fehlings MG. Degenerative cervical myelopathy: epidemiology, genetics, and pathogenesis. Spine (Phila Pa 1976). 2015;40(12):E675E693.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 3

    Fehlings MG, Tetreault LA, Riew KD, et al. A clinical practice guideline for the management of patients with degenerative cervical myelopathy: recommendations for patients with mild, moderate, and severe disease and nonmyelopathic patients with evidence of cord compression. Global Spine J. 2017;7(3)(suppl):70S83S.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 4

    Hitchon PW, Woodroffe RW, Noeller JA, Helland L, Hramakova N, Nourski KV. Anterior and posterior approaches for cervical myelopathy: clinical and radiographic outcomes. Spine (Phila Pa 1976). 2019;44(9):615623.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 5

    Lau D, Chou D, Mummaneni PV. Two-level corpectomy versus three-level discectomy for cervical spondylotic myelopathy: a comparison of perioperative, radiographic, and clinical outcomes. J Neurosurg Spine. 2015;23(3):280289.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 6

    Yoon ST, Hashimoto RE, Raich A, Shaffrey CI, Rhee JM, Riew KD. Outcomes after laminoplasty compared with laminectomy and fusion in patients with cervical myelopathy: a systematic review. Spine (Phila Pa 1976). 2013;38(22)(suppl 1):S183S194.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 7

    Lau D, Winkler EA, Than KD, Chou D, Mummaneni PV. Laminoplasty versus laminectomy with posterior spinal fusion for multilevel cervical spondylotic myelopathy: influence of cervical alignment on outcomes. J Neurosurg Spine. 2017;27(5):508517.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 8

    Fehlings MG, Wilson JR, Kopjar B, et al. Efficacy and safety of surgical decompression in patients with cervical spondylotic myelopathy: results of the AOSpine North America prospective multi-center study. J Bone Joint Surg Am. 2013;95(18):16511658.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 9

    Gulati S, Vangen-Lønne V, Nygaard ØP, et al. Surgery for degenerative cervical myelopathy: a nationwide registry-based observational study with patient-reported outcomes. Neurosurgery. 2021;89(4):704711.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 10

    Karim SM, Cadotte DW, Wilson JR, et al. Effectiveness of surgical decompression in patients with degenerative cervical myelopathy: results of the Canadian prospective multicenter study. Neurosurgery. 2021;89(5):844851.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 11

    Khan I, Archer KR, Wanner JP, et al. Trajectory of improvement in myelopathic symptoms from 3 to 12 months following surgery for degenerative cervical myelopathy. Neurosurgery. 2020;86(6):763768.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 12

    QOD Spine Registries. NeuroPoint Alliance. Updated 2021. Accessed May 13, 2022. https://www.neuropoint.org/registries/qod-spine/#1519913148052-7431e7be-7f5f

    • Search Google Scholar
    • Export Citation
  • 13

    Badhiwala JH, Witiw CD, Nassiri F, et al. Efficacy and safety of surgery for mild degenerative cervical myelopathy: results of the AOSpine North America and International prospective multicenter studies. Neurosurgery. 2019;84(4):890897.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 14

    Fehlings MG, Ibrahim A, Tetreault L, et al. A global perspective on the outcomes of surgical decompression in patients with cervical spondylotic myelopathy: results from the prospective multicenter AOSpine international study on 479 patients. Spine (Phila Pa 1976). 2015;40(17):13221328.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 15

    Tetreault L, Kopjar B, Nouri A, et al. The modified Japanese Orthopaedic Association scale: establishing criteria for mild, moderate and severe impairment in patients with degenerative cervical myelopathy. Eur Spine J. 2017;26(1):7884.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 16

    Kalsi-Ryan S, Singh A, Massicotte EM, et al. Ancillary outcome measures for assessment of individuals with cervical spondylotic myelopathy. Spine (Phila Pa 1976). 2013;38(22)(suppl 1):S111S122.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 17

    Richardson SS, Berven S. The development of a model for translation of the Neck Disability Index to utility scores for cost-utility analysis in cervical disorders. Spine J. 2012;12(1):5562.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 18

    Jansson KA, Németh G, Granath F, Jönsson B, Blomqvist P. Health-related quality of life (EQ-5D) before and one year after surgery for lumbar spinal stenosis. J Bone Joint Surg Br. 2009;91(2):210216.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 19

    Parker SL, Godil SS, Shau DN, Mendenhall SK, McGirt MJ. Assessment of the minimum clinically important difference in pain, disability, and quality of life after anterior cervical discectomy and fusion: clinical article. J Neurosurg Spine. 2013;18(2):154160.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 20

    Carreon LY, Glassman SD, Campbell MJ, Anderson PA. Neck Disability Index, short form-36 physical component summary, and pain scales for neck and arm pain: the minimum clinically important difference and substantial clinical benefit after cervical spine fusion. Spine J. 2010;10(6):469474.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 21

    Tetreault L, Nouri A, Kopjar B, Côté P, Fehlings MG. The minimum clinically important difference of the modified Japanese Orthopaedic Association scale in patients with degenerative cervical myelopathy. Spine (Phila Pa 1976). 2015;40(21):16531659.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 22

    Khan I, Pennings JS, Devin CJ, et al. Clinically meaningful improvement following cervical spine surgery: 30% reduction versus absolute point-change mcid values. Spine (Phila Pa 1976). 2021;46(11):717725.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 23

    Auffinger BM, Lall RR, Dahdaleh NS, et al. Measuring surgical outcomes in cervical spondylotic myelopathy patients undergoing anterior cervical discectomy and fusion: assessment of minimum clinically important difference. PLoS One. 2013;8(6):e67408.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 24

    Daltroy LH, Cats-Baril WL, Katz JN, Fossel AH, Liang MH. The North American Spine Society Lumbar Spine Outcome Assessment instrument: reliability and validity tests. Spine (Phila Pa 1976). 1996;21(6):741749.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 25

    Mummaneni PV, Bydon M, Alvi MA, et al. Predictive model for long-term patient satisfaction after surgery for grade I degenerative lumbar spondylolisthesis: insights from the Quality Outcomes Database. Neurosurg Focus. 2019;46(5):E12.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 26

    Tamai K, Suzuki A, Terai H, et al. Time course of physical and mental well-being improvements after cervical surgery. Spine (Phila Pa 1976). 2021;46(5):E303E309.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 27

    Badhiwala JH, Ahuja CS, Akbar MA, et al. Degenerative cervical myelopathy—update and future directions. Nat Rev Neurol. 2020;16(2):108124.

  • 28

    Parker SL, Adogwa O, Mendenhall SK, et al. Determination of minimum clinically important difference (MCID) in pain, disability, and quality of life after revision fusion for symptomatic pseudoarthrosis. Spine J. 2012;12(12):11221128.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 29

    Parker SL, Adogwa O, Paul AR, et al. Utility of minimum clinically important difference in assessing pain, disability, and health state after transforaminal lumbar interbody fusion for degenerative lumbar spondylolisthesis. J Neurosurg Spine. 2011;14(5):598604.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 30

    Parker SL, Mendenhall SK, Shau D, et al. Determination of minimum clinically important difference in pain, disability, and quality of life after extension of fusion for adjacent-segment disease. J Neurosurg Spine. 2012;16(1):6167.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 31

    Parker SL, Mendenhall SK, Shau DN, et al. Minimum clinically important difference in pain, disability, and quality of life after neural decompression and fusion for same-level recurrent lumbar stenosis: understanding clinical versus statistical significance. J Neurosurg Spine. 2012;16(5):471478.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 32

    Hu X, Jing M, Zhang M, Yang P, Yan X. Responsiveness and minimal clinically important difference of the EQ-5D-5L in cervical intraepithelial neoplasia: a longitudinal study. Health Qual Life Outcomes. 2020;18(1):324.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 33

    Vidal PM, Karadimas SK, Ulndreaj A, et al. Delayed decompression exacerbates ischemia-reperfusion injury in cervical compressive myelopathy. JCI Insight. 2017;2(11):92512.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • Collapse
  • Expand

Images from Gami et al. (pp 713–721).

  • View in gallery
    FIG. 1.

    The mJOA score for patients at baseline (preoperatively) and 3 and 12 months after surgery for CSM. Patients are stratified by myelopathy criteria established by the AO Spine study group: mild (mJOA score 15–17), moderate (mJOA score 12–14), or severe (mJOA score < 12). Of note, baseline groups differ significantly by myelopathy status. Moderate and severe myelopathy groups are significantly improved at 3 months from baseline. Mild myelopathy maintains a significantly higher mJOA score after surgical intervention when compared with moderate and severe myelopathy. Error bars for standard error of the mean are shown but, in some cases, may be smaller than the actual designated shape. Significance codes are used to denote intra- and intergroup significance. ***p < 0.001. Figure is available in color online only.

  • View in gallery
    FIG. 2.

    NDI (%) for patients at baseline (preoperatively) and 3 and 12 months after surgery for CSM. Patients are stratified by myelopathy criteria established by the AO Spine study group. Baseline groups differ significantly by myelopathy status. All severity groups are significantly improved in NDI at 3 months from baseline, with further improvement in the mild myelopathy cohort at 12 months. Error bars for standard error of the mean are shown but, in some cases, may be smaller than the actual designated shape. Significance codes are used to denote intra- and intergroup significance. *p < 0.05; **p < 0.01; ***p < 0.001. Figure is available in color online only.

  • View in gallery
    FIG. 3.

    EQ-VAS for patients at baseline (preoperatively) and 3 and 12 months postsurgery for CSM. Patients are stratified by myelopathy criteria established by the AO Spine study group. Baseline groups differ significantly by myelopathy status. All severity groups are significantly improved in EQ-VAS at 3 months from baseline, with no further improvement at 12 months. Mild myelopathy maintains its significantly higher EQ-VAS score at 3 months after surgical intervention when compared with moderate and severe myelopathy. Error bars for standard error of mean are shown but, in some cases, may be smaller than the actual designated shape. Significance codes are used to denote intra- and intergroup significance. *p < 0.05; **p < 0.01; ***p < 0.001. Figure is available in color online only.

  • View in gallery
    FIG. 4.

    QALYs for patients at baseline (preoperatively) and 3 and 12 months postsurgery for CSM. Patients are stratified by myelopathy criteria established by the AO Spine study group. Baseline groups differ significantly by myelopathy status. All severity groups are significantly improved in QALYs at 3 months from baseline, with no further improvement at 12 months. Mild myelopathy maintains a significantly higher QALY score after surgical intervention when compared with moderate and severe myelopathy. Error bars for standard error of mean are shown but, in some cases, may be smaller than the actual designated shape. Significance codes are used to denote intra- and intergroup significance. *p < 0.05; **p < 0.01; ***p < 0.001. Figure is available in color online only.

  • 1

    Kalsi-Ryan S, Karadimas SK, Fehlings MG. Cervical spondylotic myelopathy: the clinical phenomenon and the current pathobiology of an increasingly prevalent and devastating disorder. Neuroscientist. 2013;19(4):409421.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 2

    Nouri A, Tetreault L, Singh A, Karadimas SK, Fehlings MG. Degenerative cervical myelopathy: epidemiology, genetics, and pathogenesis. Spine (Phila Pa 1976). 2015;40(12):E675E693.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 3

    Fehlings MG, Tetreault LA, Riew KD, et al. A clinical practice guideline for the management of patients with degenerative cervical myelopathy: recommendations for patients with mild, moderate, and severe disease and nonmyelopathic patients with evidence of cord compression. Global Spine J. 2017;7(3)(suppl):70S83S.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 4

    Hitchon PW, Woodroffe RW, Noeller JA, Helland L, Hramakova N, Nourski KV. Anterior and posterior approaches for cervical myelopathy: clinical and radiographic outcomes. Spine (Phila Pa 1976). 2019;44(9):615623.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 5

    Lau D, Chou D, Mummaneni PV. Two-level corpectomy versus three-level discectomy for cervical spondylotic myelopathy: a comparison of perioperative, radiographic, and clinical outcomes. J Neurosurg Spine. 2015;23(3):280289.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 6

    Yoon ST, Hashimoto RE, Raich A, Shaffrey CI, Rhee JM, Riew KD. Outcomes after laminoplasty compared with laminectomy and fusion in patients with cervical myelopathy: a systematic review. Spine (Phila Pa 1976). 2013;38(22)(suppl 1):S183S194.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 7

    Lau D, Winkler EA, Than KD, Chou D, Mummaneni PV. Laminoplasty versus laminectomy with posterior spinal fusion for multilevel cervical spondylotic myelopathy: influence of cervical alignment on outcomes. J Neurosurg Spine. 2017;27(5):508517.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 8

    Fehlings MG, Wilson JR, Kopjar B, et al. Efficacy and safety of surgical decompression in patients with cervical spondylotic myelopathy: results of the AOSpine North America prospective multi-center study. J Bone Joint Surg Am. 2013;95(18):16511658.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 9

    Gulati S, Vangen-Lønne V, Nygaard ØP, et al. Surgery for degenerative cervical myelopathy: a nationwide registry-based observational study with patient-reported outcomes. Neurosurgery. 2021;89(4):704711.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 10

    Karim SM, Cadotte DW, Wilson JR, et al. Effectiveness of surgical decompression in patients with degenerative cervical myelopathy: results of the Canadian prospective multicenter study. Neurosurgery. 2021;89(5):844851.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 11

    Khan I, Archer KR, Wanner JP, et al. Trajectory of improvement in myelopathic symptoms from 3 to 12 months following surgery for degenerative cervical myelopathy. Neurosurgery. 2020;86(6):763768.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 12

    QOD Spine Registries. NeuroPoint Alliance. Updated 2021. Accessed May 13, 2022. https://www.neuropoint.org/registries/qod-spine/#1519913148052-7431e7be-7f5f

    • Search Google Scholar
    • Export Citation
  • 13

    Badhiwala JH, Witiw CD, Nassiri F, et al. Efficacy and safety of surgery for mild degenerative cervical myelopathy: results of the AOSpine North America and International prospective multicenter studies. Neurosurgery. 2019;84(4):890897.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 14

    Fehlings MG, Ibrahim A, Tetreault L, et al. A global perspective on the outcomes of surgical decompression in patients with cervical spondylotic myelopathy: results from the prospective multicenter AOSpine international study on 479 patients. Spine (Phila Pa 1976). 2015;40(17):13221328.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 15

    Tetreault L, Kopjar B, Nouri A, et al. The modified Japanese Orthopaedic Association scale: establishing criteria for mild, moderate and severe impairment in patients with degenerative cervical myelopathy. Eur Spine J. 2017;26(1):7884.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 16

    Kalsi-Ryan S, Singh A, Massicotte EM, et al. Ancillary outcome measures for assessment of individuals with cervical spondylotic myelopathy. Spine (Phila Pa 1976). 2013;38(22)(suppl 1):S111S122.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 17

    Richardson SS, Berven S. The development of a model for translation of the Neck Disability Index to utility scores for cost-utility analysis in cervical disorders. Spine J. 2012;12(1):5562.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 18

    Jansson KA, Németh G, Granath F, Jönsson B, Blomqvist P. Health-related quality of life (EQ-5D) before and one year after surgery for lumbar spinal stenosis. J Bone Joint Surg Br. 2009;91(2):210216.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 19

    Parker SL, Godil SS, Shau DN, Mendenhall SK, McGirt MJ. Assessment of the minimum clinically important difference in pain, disability, and quality of life after anterior cervical discectomy and fusion: clinical article. J Neurosurg Spine. 2013;18(2):154160.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 20

    Carreon LY, Glassman SD, Campbell MJ, Anderson PA. Neck Disability Index, short form-36 physical component summary, and pain scales for neck and arm pain: the minimum clinically important difference and substantial clinical benefit after cervical spine fusion. Spine J. 2010;10(6):469474.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 21

    Tetreault L, Nouri A, Kopjar B, Côté P, Fehlings MG. The minimum clinically important difference of the modified Japanese Orthopaedic Association scale in patients with degenerative cervical myelopathy. Spine (Phila Pa 1976). 2015;40(21):16531659.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 22

    Khan I, Pennings JS, Devin CJ, et al. Clinically meaningful improvement following cervical spine surgery: 30% reduction versus absolute point-change mcid values. Spine (Phila Pa 1976). 2021;46(11):717725.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 23

    Auffinger BM, Lall RR, Dahdaleh NS, et al. Measuring surgical outcomes in cervical spondylotic myelopathy patients undergoing anterior cervical discectomy and fusion: assessment of minimum clinically important difference. PLoS One. 2013;8(6):e67408.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 24

    Daltroy LH, Cats-Baril WL, Katz JN, Fossel AH, Liang MH. The North American Spine Society Lumbar Spine Outcome Assessment instrument: reliability and validity tests. Spine (Phila Pa 1976). 1996;21(6):741749.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 25

    Mummaneni PV, Bydon M, Alvi MA, et al. Predictive model for long-term patient satisfaction after surgery for grade I degenerative lumbar spondylolisthesis: insights from the Quality Outcomes Database. Neurosurg Focus. 2019;46(5):E12.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 26

    Tamai K, Suzuki A, Terai H, et al. Time course of physical and mental well-being improvements after cervical surgery. Spine (Phila Pa 1976). 2021;46(5):E303E309.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 27

    Badhiwala JH, Ahuja CS, Akbar MA, et al. Degenerative cervical myelopathy—update and future directions. Nat Rev Neurol. 2020;16(2):108124.

  • 28

    Parker SL, Adogwa O, Mendenhall SK, et al. Determination of minimum clinically important difference (MCID) in pain, disability, and quality of life after revision fusion for symptomatic pseudoarthrosis. Spine J. 2012;12(12):11221128.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 29

    Parker SL, Adogwa O, Paul AR, et al. Utility of minimum clinically important difference in assessing pain, disability, and health state after transforaminal lumbar interbody fusion for degenerative lumbar spondylolisthesis. J Neurosurg Spine. 2011;14(5):598604.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 30

    Parker SL, Mendenhall SK, Shau D, et al. Determination of minimum clinically important difference in pain, disability, and quality of life after extension of fusion for adjacent-segment disease. J Neurosurg Spine. 2012;16(1):6167.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 31

    Parker SL, Mendenhall SK, Shau DN, et al. Minimum clinically important difference in pain, disability, and quality of life after neural decompression and fusion for same-level recurrent lumbar stenosis: understanding clinical versus statistical significance. J Neurosurg Spine. 2012;16(5):471478.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 32

    Hu X, Jing M, Zhang M, Yang P, Yan X. Responsiveness and minimal clinically important difference of the EQ-5D-5L in cervical intraepithelial neoplasia: a longitudinal study. Health Qual Life Outcomes. 2020;18(1):324.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 33

    Vidal PM, Karadimas SK, Ulndreaj A, et al. Delayed decompression exacerbates ischemia-reperfusion injury in cervical compressive myelopathy. JCI Insight. 2017;2(11):92512.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation

Metrics

All Time Past Year Past 30 Days
Abstract Views 1707 1707 0
Full Text Views 648 648 317
PDF Downloads 498 498 154
EPUB Downloads 0 0 0