Abstract
Study Design
Prospective cohort study.
Objectives
The significance of failing to achieve the minimum clinically important difference (MCID) early after surgery for degenerative cervical myelopathy (DCM) remains unclear. To compare postoperative clinical outcomes among early-, delayed-, and persistent non-responders for DCM and to clarify the clinical significance of delayed neurological recovery.
Methods
A total of 655 patients with moderate-to-severe DCM were categorized according to the achievement of the MCID in the Japanese Orthopaedic Association (JOA) score: early responders (MCID at 6 months), delayed responders (no MCID at 6 months but MCID at 2 years), and persistent non-responders (no MCID at either time point). Neurological, pain-related, and patient-reported outcomes were compared among the groups. Among patients without MCID achievement at 6 months, binary logistic regression analysis was performed to identify the factors associated with delayed MCID achievement.
Results
Among patients without MCID achievement at 6 months, 36.9% achieved the MCID by 2 years. Binary logistic regression identified the 6-month JOA score, upper extremity function in the JOA Cervical Myelopathy Evaluation Questionnaire, and physical component summary of the 36-Item Short Form Health Survey as associated factors. Pain-related measures, autonomic function, and mental health status did not differ significantly among the groups.
Conclusions
Approximately one-third of patients without early MCID achievement subsequently achieved the MCID within 2 years. Failure to achieve the MCID at 6 months does not necessarily indicate poor long-term outcomes, supporting the importance of continued postoperative follow-up.
Keywords: degenerative cervical myelopathy, minimum clinically important difference, Japanese orthopaedic association score, neurological recovery, patterns of neurological recovery, delayed recovery, patient-reported outcome measures, associated factors
Introduction
Degenerative cervical myelopathy (DCM) is the leading cause of spinal cord dysfunction in adults and includes cervical spondylotic myelopathy (CSM) and ossification of the posterior longitudinal ligament (OPLL), frequently resulting in progressive neurological impairment and diminished quality of life (QOL).1,2 Posterior decompression is widely recognized as the standard treatment for patients with moderate-to-severe disease, with numerous studies confirming its effectiveness in halting disease progression and enhancing both neurological function and patient-reported outcome measures (PROMs).2-4
In assessing surgical outcomes for DCM, there has been a growing emphasis on patient-centered measures, including the concept of the minimum clinically important difference (MCID). The MCID signifies the smallest change in an outcome measure that patients perceive as beneficial and is widely used to assess the clinical relevance of postoperative improvement.5,6 Achieving the MCID in the Japanese Orthopaedic Association (JOA) score is recognized as a significant indicator of neurological recovery after surgery.7,8 Meanwhile, the natural course of postoperative recovery in DCM varies, and neurological improvement may continue beyond the early postoperative period in some patients. 9 Despite the clinical significance of this issue, limited attention has been paid to patients who do not achieve the MCID in the early postoperative phase.10,11 Specifically, it remains unclear whether failure to achieve MCID at 6 months reliably predicts poor long-term outcomes or if a subset of patients can experience delayed but meaningful recovery over time. Furthermore, the characteristics of delayed responders and their postoperative recovery patterns have not been well characterized.
In a previous analysis of the same prospective multicenter registry, MCID achievement was evaluated as a binary 2-year outcome, focusing on preoperative associated factors and their associations with PROMs. 8 However, that study did not examine postoperative recovery patterns or delayed MCID achievement. Therefore, this secondary longitudinal subgroup analysis compared clinical outcomes among early responders, delayed responders, and persistent non-responders after posterior decompression without fusion for DCM and identified factors associated with MCID achievement by 2 years among patients who had not achieved it at 6 months postoperatively.
Materials and Methods
Study Design and Patient Demographics
This study was a secondary longitudinal subgroup analysis of a prospectively collected multicenter registry used in our previous publication. 8 The prospective observational registry was conducted at 10 spine centers in Japan. Although the study protocol was approved by the institutional review boards of the participating institutions in 2018 (approval number: 20180045), patient enrollment occurred between February 2019 and December 2022. 12 During the recruitment period, all consecutive patients who underwent cervical spine surgery at the participating institutions were prospectively enrolled in the registry after providing written informed consent. A total of 1,482 patients with cervical spine disorders constituted the source population for the present study. Among them, patients diagnosed with DCM were identified. To obtain a homogeneous surgical cohort, patients who underwent anterior cervical procedures or posterior fusion were excluded, leaving those who underwent posterior decompression without fusion. Patients with mild DCM, defined as a preoperative JOA score ≥15, were also excluded because a 2.5-point improvement could not be theoretically achieved without exceeding the maximum JOA score of 17, potentially introducing a ceiling effect in MCID-based analyses. Patients with missing JOA scores at 6 months, 1 year, or 2 years postoperatively were also excluded. After applying these inclusion and exclusion criteria, 69 patients were excluded because of incomplete follow-up, and 655 patients were included in the final analysis (Figure 1). All patients included in the present study were also part of the previously published cohort. All procedures were performed using open surgical techniques. Posterior decompression procedures included open-door laminoplasty, double-door laminoplasty, and selective laminectomy. Surgical indications, approaches, and the extent of posterior decompression were determined at each institution according to standard clinical practice. Estimated blood loss (EBL) was recorded intraoperatively, and perioperative complications were prospectively documented using a standardized case report form.
Figure 1.
Flow diagram of patient selection. Of the 1,482 registered patients, 1,105 were diagnosed with DCM after excluding other diagnoses (n = 377). After excluding patients who underwent anterior surgery, posterior fusion, or had mild DCM (JOA score ≥15) (n = 216), 889 patients underwent posterior decompression without fusion. Among these, 655 patients with complete follow-up data at 6 months, 1 year, and 2 years were included in the final analysis of this study
Clinical Outcome Measures
Neurological status was assessed using the JOA score. 13 The change in the JOA score from baseline (ΔJOA) and the JOA recovery rate (%) were calculated to quantify neurological improvement.13,14 In accordance with previous studies, an improvement of ≥ 2.5 points in the JOA score was defined as the MCID for patients with DCM. 7 Pain intensity was evaluated using a 100-mm visual analog scale (VAS). Neuropathic pain symptoms were assessed using the Neuropathic Pain Symptom Inventory (NPSI). 15 Functional outcomes and health-related QOL (HRQOL) were evaluated using the JOA Cervical Myelopathy Evaluation Questionnaire (JOACMEQ)16,17 and the 36-Item Short Form Health Survey (SF-36). 18
All clinical outcomes were assessed preoperatively and at 6 months, 1 year, and 2 years postoperatively. Perioperative complications were defined as any adverse events that occurred within 30 days after surgery.
Group Classification Based on MCID Achievement
Patients were categorized into three groups based on their MCID achievement at 6 months and 2 years postoperatively: Early responder (achieved MCID at 6 months, n = 362), Delayed responder (did not achieve MCID at 6 months but did so at 2 years, n = 108), Persistent non-responder (did not achieve MCID at either time point, n = 185).
Statistical Analyses
Continuous variables are presented as means with standard deviations, whereas categorical variables are shown as frequencies and percentages. To evaluate the differences in baseline characteristics and surgical variables among the three groups, continuous variables were analyzed using analysis of variance, and categorical variables were assessed using the chi-squared test. For clinical outcomes, general linear models were used to adjust for potential confounders, and the results are presented as adjusted means with 95% confidence intervals (CIs). Furthermore, for patients who did not reach the MCID at 6 months, a binary logistic regression analysis was conducted to identify factors associated with achieving the MCID at 2 years. Candidate variables were selected from univariate analyses (Supplemental Tables 1 and 2); those with p < 0.20 were entered into the multivariate model, along with age at surgery and sex. To evaluate whether 6-month clinical variables could predict 2-year MCID achievement in patients who had not reached MCID at 6 months, a receiver operating characteristic (ROC) curve analysis was performed. A combined model derived from variables identified through logistic regression analysis was employed to generate the predicted probabilities. The area under the curve (AUC) was calculated, and the optimal cutoff point was determined using the Youden index. To evaluate the robustness of the primary analysis, a sensitivity analysis was conducted using the JOA recovery rate as an alternative responder definition. The JOA recovery rate was calculated as (postoperative JOA score − preoperative JOA score)/(17 − preoperative JOA score) × 100. Patients were reclassified as early responders if the recovery rate was ≥50% at 6 months, delayed responders if it was <50% at 6 months but ≥50% at 2 years, and persistent non-responders if it remained <50% at both time points.
All statistical analyses were performed using SPSS version 29.0 (IBM Corp., Armonk, NY, USA).
Results
There were no significant differences among these groups in terms of age at the time of surgery (early responders 69.1 ± 11.6, delayed responders 67.5 ± 12.4, and persistent non-responders 68.9 ± 11.3 years; p = 0.446), sex distribution (%men: 70.7%, 70.4%, and 71.4%; p = 0.981), body mass index (BMI) (24.5 ± 4.0, 24.4 ± 3.7, and 24.9 ± 3.9 kg/m2; p = 0.551), smoking status (%current smoker: 18.8%, 18.5%, and 18.4%; p = 0.462), or diagnosis (%CSM: 82.3%, 74.1%, and 77.8%; p = 0.132). Comorbidities were also comparable across the groups. However, the duration of symptoms was significantly shorter in the early responders (20.7 ± 34.4 months) than in the delayed responders (28.1 ± 47.9 months) and persistent non-responders (28.9 ± 42.9 months) (p = 0.040) (Table 1). Baseline demographic characteristics, comorbidities, surgical variables, and perioperative complications were compared between patients included in the final analysis (n = 655) and those excluded because of incomplete follow-up (n = 69) (Supplemental Table 3). No statistically significant differences were observed between the two groups.
Table 1.
Patient Baseline Demographic Information on 655 Patients With DCM
| | Early responder group (n = 362) | Delayed responder group (n = 108) | Persistent non-responder group (n = 185) | p-value |
|---|---|---|---|---|
| Age at the time of surgery (y/o) | 69.1 ± 11.6 | 67.5 ± 12.4 | 68.9 ± 11.3 | 0.446 |
| Sex (n, %) | ||||
| Men | 256 (70.7%) | 76 (70.4%) | 132 (71.4%) | 0.981 |
| Women | 106 (29.3%) | 32 (29.6%) | 53 (28.6%) | |
| Diagnosis (n, %) | ||||
| CSM | 298 (82.3%) | 80 (74.1%) | 144 (77.8%) | 0.132 |
| OPLL | 64 (17.7%) | 28 (25.9%) | 41 (22.2%) | |
| Body mass index (kg/m2) | 24.5 ± 4.0 | 24.4 ± 3.7 | 24.9 ± 3.9 | 0.551 |
| Current smoker (n, %) | 68 (18.8%) | 20 (18.5%) | 34 (18.4%) | 0.462 |
| Comorbidities (%) | ||||
| Hypertension | 49.7 | 47.2 | 54.1 | 0.476 |
| Diabetes mellitus | 22.7 | 21.3 | 29.7 | 0.135 |
| Cardiac disease | 11.3 | 10.2 | 10.3 | 0.906 |
| Malignant tumor | 10.8 | 8.3 | 9.0 | 0.628 |
| Cerebrovascular disease | 5.2 | 6.5 | 10.3 | 0.088 |
| Respiratory disease | 4.4 | 6.5 | 7.6 | 0.295 |
| Connective tissue disease | 1.4 | 1.9 | 1.6 | 0.933 |
| Psychiatric disease | 3.9 | 2.8 | 2.2 | 0.542 |
| Presence of intraspinal high signal intensity area on T2-weighted MRI (n, %) | 280 (77.3%) | 77 (71.3%) | 145 (78.4%) | 0.337 |
| Duration of symptoms (month) | 20.7 ± 34.4 | 28.1 ± 47.9 | 28.9 ± 42.9 | 0.040* |
Values indicate mean ± standard deviation, *p < 0.05, statistically significant difference.
DCM, degenerative cervical myelopathy; CSM, cervical spondylotic myelopathy; OPLL, ossification of the posterior longitudinal ligament; MRI, magnetic resonance imaging.
No significant differences were noted among the three groups regarding the surgical procedure (p = 0.372), operative time (94.2 ± 38.1, 101.1 ± 38.7, and 97.0 ± 38.6 minutes; p = 0.246), EBL (37.7 ± 64.6, 33.5 ± 45.3, and 38.8 ± 60.5 mL; p = 0.758), or the number of operated laminae (4.0 ± 1.1, 4.2 ± 1.1, and 3.9 ± 1.2; p = 0.077). However, among the perioperative complications, the incidence of segmental motor paralysis (C5 palsy) varied significantly across the groups (0.8%, 2.8%, and 4.3%; p = 0.025), with the highest rate occurring in the persistent non-responders (Table 2).
Table 2.
Comparison of Surgical Information and Perioperative Complications
| | Early responder group (n = 362) | Delayed responder group (n = 108) | Persistent non-responder group (n = 185) | p-value |
|---|---|---|---|---|
| Surgical procedure (n, %) | ||||
| OD | 108 (29.8%) | 39 (36.1%) | 54 (29.2%) | 0.372 |
| DD | 64 (17.7%) | 11 (10.2%) | 31 (16.8%) | |
| SL | 190 (52.5%) | 58 (53.7%) | 100 (54.1%) | |
| Intraoperative information | ||||
| Operative time (min) | 94.2 ± 38.1 | 101.1 ± 38.7 | 97.0 ± 38.6 | 0.246 |
| EBL (mL) | 37.7 ± 64.6 | 33.5 ± 45.3 | 38.8 ± 60.5 | 0.758 |
| Number of operated laminae | 4.0 ± 1.1 | 4.2 ± 1.1 | 3.9 ± 1.2 | 0.077 |
| Perioperative complications (n, %) | ||||
| Segmental motor paralysis (C5) | 3 (0.8%) | 3 (2.8%) | 8 (4.3%) | 0.025* |
| SSI | 1 (0.3%) | 3 (2.8%) | 3 (1.6%) | 0.059 |
| Epidural hematoma | 3 (0.8%) | 1 (0.9%) | 2 (1.1%) | 0.958 |
| Dural tear | 2 (0.6%) | 0 (0.0%) | 3 (1.6%) | 0.241 |
| Neurological deterioration | 4 (1.1%) | 3 (2.8%) | 8 (4.3%) | 0.055 |
Values indicate mean ± standard deviation, *p < 0.05, statistically significant difference.
OD, open-door laminoplasty; DD, double-door laminoplasty; SL, selective laminectomy; EBL, estimated blood loss; SSI, surgical site infection.
The preoperative JOA score was lowest in the early responders (10.0 [95% CIs: 9.8–10.3]) compared to the delayed responders (11.2 [10.8–11.6]) and persistent non-responders (12.2 [12.0–12.6]) (p < 0.001). At 2 years, both early and delayed responders exhibited significantly higher JOA scores (14.5 [14.2–14.7] and 15.0 [14.6–15.4]) than persistent non-responders (13.1 [12.8–13.4]) (p < 0.001). The ΔJOA was markedly greater in the early (4.4 [4.2–4.6]) and delayed (3.8 [3.4–4.2]) responders than in the persistent non-responders (0.8 [0.6–1.1]) (p < 0.001). Similarly, the JOA recovery rate was significantly higher in early (64.6% [61.7–67.5]) and delayed (69.7% [64.4–75.0]) responders than in persistent non-responders (19.5% [15.4–23.6]) (p < 0.001). Although most VAS and NPSI scores were similar, pain or numbness from the chest to the toe at 2 years was significantly lower in delayed responders (28.8 [23.0–34.6] mm) than in persistent non-responders (36.9 [32.3–41.4] mm) (p = 0.048) (Table 3). Among patients who did not achieve the MCID at 6 months, those classified as delayed responders continued to show improvement, whereas persistent non-responders exhibited minimal recovery. Conversely, early responders demonstrated limited progress beyond 6 months, indicating a plateau (Figure 2). Because the study groups were defined based on MCID achievement at the 2-year follow-up, comparisons of the 2-year JOA score, ΔJOA, and JOA recovery rate should be considered descriptive rather than confirmatory.
Table 3.
Comparison of Neurological and Pain-Related Clinical Outcomes
| | Early responder group (n = 362) | Delayed responder group (n = 108) | Persistent non-responder group (n = 185) | p-value |
|---|---|---|---|---|
| Cervical JOA score | ||||
| Preoperation † | 10.0 (9.8–10.3) | 11.2 (10.8–11.6) | 12.2 (12.0–12.6) | < 0.001*** |
| 2 years after surgery ⁑ | 14.5 (14.2–14.7) | 15.0 (14.6–15.4) | 13.1(12.8–13.4) | < 0.001*** |
| ΔJOA score ⁑ | 4.4 (4.2–4.6) | 3.8 (3.4–4.2) | 0.8 (0.6–1.1) | < 0.001*** |
| JOA score recovery rate (%) ⁑ | 64.6 (61.7–67.5) | 69.7 (64.4–75.0) | 19.5 (15.4–23.6) | < 0.001*** |
| VAS | ||||
| Pain or stiffness in neck or shoulders (mm) | ||||
| Preoperation † | 45.0 (41.9–48.0) | 46.8 (41.1–52.4) | 45.5 (41.2–49.8) | 0.861 |
| 2 years after surgery ⁑ | 37.2 (34.0–40.3) | 39.7 (34.0–45.4) | 41.1 (36.7–45.6) | 0.347 |
| Tightness in chest (mm) | ||||
| Preoperation † | 10.4 (8.2–12.5) | 11.4 (7.6–15.3) | 9.9 (6.9–12.9) | 0.827 |
| 2 years after surgery ⁑ | 10.2 (8.0–12.4) | 9.5 (5.5–13.4) | 12.4 (9.3–15.5) | 0.413 |
| Pain or numbness in arms or hands (mm) | ||||
| Preoperation † | 64.8 (61.7–67.8) | 60.6 (55.0–66.2) | 57.7 (53.3–62.0) | 0.127 |
| 2 years after surgery ⁑ | 41.2 (37.8–44.7) | 45.1 (39.0–51.3) | 47.8 (43.0–52.7) | 0.086 |
| Pain or numbness in chest to toe (mm) | ||||
| Preoperation † | 42.9 (39.4–46.3) | 37.9 (31.6–44.3) | 39.8 (35.0–44.7) | 0.328 |
| 2 years after surgery ⁑ | 30.8 (27.6–34.0) | 28.8 (23.0–34.6) | 36.9 (32.3–41.4) | 0.048* |
| NPSI | ||||
| Burning | | | | |
| Preoperation † | 1.7 (1.4–2.0) | 2.5 (1.9–3.0) | 2.1 (1.7–2.6) | 0.041* |
| 2 years after surgery ⁑ | 1.6 (1.4–1.9) | 1.3 (0.8–1.8) | 1.8 (1.4–2.2) | 0.263 |
| Pressing | ||||
| Preoperation † | 1.9 (1.7–2.2) | 2.6 (2.1–3.1) | 2.1 (1.7–2.4) | 0.061 |
| 2 years after surgery ⁑ | 1.6 (1.4–1.9) | 1.5 (1.0–1.9) | 1.7 (1.3–2.1) | 0.722 |
| Paroxysmal | ||||
| Preoperation † | 1.2 (1.0–1.5) | 1.3 (0.9–1.7) | 1.5 (1.2–1.8) | 0.481 |
| 2 years after surgery ⁑ | 1.1 (0.9–1.4) | 1.1 (0.7–1.5) | 1.1 (0.8–1.4) | 0.982 |
| Evoked | ||||
| Preoperation † | 1.7 (1.5–2.0) | 2.1 (1.7–2.6) | 1.7 (1.4–2.1) | 0.283 |
| 2 years after surgery ⁑ | 1.3 (1.1–1.5) | 1.4 (1.0–1.8) | 1.5 (1.2–1.8) | 0.713 |
| Paresthesia/dysesthesia | ||||
| Preoperation † | 3.2 (2.9–3.5) | 3.0 (2.5–3.6) | 3.2 (2.8–3.6) | 0.863 |
| 2 years after surgery ⁑ | 2.0 (1.7–2.3) | 2.3 (1.8–2.8) | 2.6 (2.2–3.0) | 0.062 |
| Total | ||||
| Preoperation † | 19.6 (17.5–21.6) | 22.3 (18.5–26.0) | 20.5 (17.7–23.4) | 0.456 |
| 2 years after surgery ⁑ | 15.0 (12.9–17.1) | 14.9 (11.1–18.6) | 17.0 (14.0–19.9) | 0.529 |
Values are presented as adjusted means (95% confidence intervals).
*p < 0.05, ** < 0.01, *** < 0.001, statistically significant difference.
MCID, minimum clinically important difference; JOA, Japanese Orthopaedic Association; Δ, change from preoperative to postoperative values; VAS, visual analog scale; NPSI, Neuropathic Pain Symptom Inventory.
†Adjusted for differences in patient demographics (p < 0.05 in Table 1): duration of symptoms.
Figure 2.
Temporal changes in the JOA score across the three groups. The early responder group showed rapid improvement within 6 months, followed by a plateau. Among patients who did not achieve the minimal clinically important difference (MCID) at 6 months, delayed responders demonstrated continued improvement up to 2 years, whereas persistent non-responders showed minimal recovery beyond 6 months
After 2 years, JOACMEQ cervical spine function (82.4 [77.4–87.5] vs. 74.4 [70.5–78.3]; p = 0.046), upper extremity function (87.0 [83.7–90.4] vs. 79.1 [76.4–81.7]; p < 0.001), and lower extremity function (68.3 [63.0–73.6] vs. 59.8 [55.7–63.8]; p = 0.002) were notably higher in delayed responders than in persistent non-responders. QOL scores were also significantly elevated in early (55.1 [53.1–57.1]) and delayed (53.1 [49.5–56.6]) responders compared to persistent non-responders (46.1 [43.3–48.9]) (p < 0.001). Similarly, the physical component summary (PCS) of the SF-36 was significantly higher in both early (38.1 [35.8–39.4]) and delayed (38.0 [35.6–40.3]) responders than in persistent non-responders (33.4 [31.5–35.2]) (p < 0.001), while no significant differences were found in the mental component summary (MCS) score (Table 4).
Table 4.
Functional Outcomes and Health-Related Quality of Life Assessed Using the JOACMEQ and SF-36
| | Early responder group (n = 362) | Delayed responder group (n = 108) | Persistent non-responder group (n = 185) | p-value |
|---|---|---|---|---|
| JOACMEQ | ||||
| Cervical spine function | ||||
| Preoperation † | 64.4 (61.5–67.4) | 67.3 (61.9–72.7) | 69.4 (65.2–73.6) | 0.162 |
| 2 years after surgery ⁑ | 77.1 (74.3–79.8) | 82.4 (77.4–87.5) | 74.4 (70.5–78.3) | 0.046* |
| Upper extremity function | ||||
| Preoperation † | 69.3 (67.1–71.6) | 78.4 (74.2–82.6) | 76.6 (73.4–79.9) | < 0.001*** |
| 2 years after surgery ⁑ | 85.3 (83.4–87.2) | 87.0 (83.7–90.4) | 79.1 (76.4–81.7) | < 0.001*** |
| Lower extremity function | ||||
| Preoperation † | 52.8 (49.8–55.8) | 61.5 (56.0–67.1) | 59.4 (55.1–63.7) | 0.006** |
| 2 years after surgery ⁑ | 68.4 (65.5–71.3) | 68.3 (63.0–73.6) | 59.8 (55.7–63.8) | 0.002** |
| Bladder function | ||||
| Preoperation † | 70.0 (67.8–72.1) | 72.2 (68.2–76.1) | 72.1 (69.0–75.2) | 0.430 |
| 2 years after surgery ⁑ | 73.1 (70.9–75.3) | 74.9 (70.9–79.0) | 71.9 (68.7–75.0) | 0.497 |
| Quality of life | ||||
| Preoperation † | 44.1 (42.3–45.9) | 46.8 (43.6–50.1) | 43.8 (41.2–46.3) | 0.289 |
| 2 years after surgery ⁑ | 55.1 (53.1–57.1) | 53.1 (49.5–56.6) | 46.1 (43.3–48.9) | < 0.001*** |
| SF-36 | ||||
| PCS | ||||
| Preoperation † | 31.3 (30.0–32.6) | 34.3 (31.9–36.7) | 33.4 (31.6–35.3) | 0.044* |
| 2 years after surgery ⁑ | 38.1 (35.8–39.4) | 38.0 (35.6–40.3) | 33.4 (31.5–35.2) | < 0.001*** |
| MCS | ||||
| Preoperation † | 51.1 (50.1–52.1) | 50.7 (48.9–52.5) | 50.5 (49.1–51.9) | 0.755 |
| 2 years after surgery ⁑ | 52.9 (52.0–53.9) | 51.6 (49.9–53.4) | 51.9 (50.5–53.3) | 0.305 |
Values are presented as adjusted means (95% confidence intervals).
*p < 0.05, ** < 0.01, *** < 0.001, statistically significant difference.
JOACMEQ, JOA cervical myelopathy evaluation questionnaire; SF-36, short-form 36; PCS, physical component summary; MCS, mental component summary.
†Adjusted for differences in patient demographics (p < 0.05 in Table 1): duration of symptoms.
⁑Adjusted for differences in patient demographics and surgical characteristics (p < 0.05 in Table 1 and 2): duration of symptoms and perioperative complication (segmental motor paralysis).
Among the patients who did not achieve MCID at 6 months after surgery, 36.9% eventually achieved MCID at 2 years. Sensitivity analysis using the JOA score recovery rate as an alternative responder definition yielded comparable findings (Supplemental Table 4). With a recovery-rate threshold of ≥50%, 38.9% (131/337) of patients who had not reached the threshold at 6 months subsequently achieved it by 2 years, supporting the robustness of the primary MCID-based analysis. When comparing persistent non-responders to delayed responders at 6 months, the baseline demographic and surgical characteristics were largely similar between the two groups (Tables 5 and 6). At 6 months, delayed responders had higher PCS scores (37.8 ± 10.8 vs. 34.5 ± 10.8; p = 0.024). In contrast, other pain-related and patient-reported outcomes showed no significant differences between the groups. Binary logistic regression analysis identified the 6-month JOA score (odds ratio [OR], 0.777; 95% CI, 0.658–0.918; p = 0.003), JOACMEQ upper extremity function (1.023; 1.000–1.047; p = 0.044), and PCS score (1.039; 1.001–1.078; p = 0.045) as factors associated with subsequent MCID achievement (Table 7). ROC curve analysis of the combined model incorporating the 6-month JOA score, SF-36 PCS, and JOACMEQ upper extremity function demonstrated a modest discriminative ability (AUC = 0.647). The optimal cutoff value of the predicted probability was 0.45, yielding a sensitivity of 37.4% and a specificity of 84.1% (Figure 3).
Table 5.
Comparison of Demographic and Surgical Information Between Persistent Non-responder and Delayed Responder Group
| | Delayed responder group (n = 108) | Persistent non-responder group (n = 185) | p-value |
|---|---|---|---|
| Age at the time of surgery (y/o) | 67.5 ± 12.4 | 68.9 ± 11.3 | 0.342 |
| Sex (n, %) | |||
| Men | 76 (70.4%) | 132 (71.4%) | 0.858 |
| Women | 32 (29.6%) | 53 (28.6%) | |
| Diagnosis (n, %) | |||
| CSM | 80 (74.1%) | 144 (77.8%) | 0.464 |
| OPLL | 28 (25.9%) | 41 (22.2%) | |
| Body mass index (kg/cm2) | 24.4 ± 3.7 | 24.9 ± 3.9 | 0.324 |
| Current smoker (n, %) | 20 (18.5%) | 34 (18.4%) | 0.215 |
| Comorbidities (%) | |||
| Hypertension | 47.2 | 54.1 | 0.246 |
| Diabetes mellitus | 21.3 | 29.7 | 0.115 |
| Cardiac disease | 10.2 | 10.3 | 0.982 |
| Malignant tumor | 8.3 | 9.0 | 0.803 |
| Cerebrovascular disease | 6.5 | 10.3 | 0.271 |
| Respiratory disease | 6.5 | 7.6 | 0.728 |
| Connective tissue disease | 1.9 | 1.6 | 0.883 |
| Psychiatric disease | 2.8 | 2.2 | 0.739 |
| Presence of intraspinal high signal intensity area on T2-weighted MRI (n, %) | 77 (71.3%) | 145 (78.4%) | 0.172 |
| Duration of symptoms (month) | 28.1 ± 47.9 | 28.9 ± 42.9 | 0.881 |
| Surgical procedure (n, %) | |||
| OD | 39 (36.1%) | 54 (29.2%) | 0.214 |
| DD | 11 (10.2%) | 31 (16.8%) | |
| SL | 58 (53.7%) | 100 (54.1%) | |
| Intraoperative information | |||
| Operative time (min) | 101.1 ± 38.7 | 97.0 ± 38.6 | 0.389 |
| EBL (mL) | 33.5 ± 45.3 | 38.8 ± 60.5 | 0.428 |
| Number of operated laminae | 4.2 ± 1.1 | 3.9 ± 1.2 | 0.033 |
| Perioperative complications (n, %) | |||
| Segmental motor paralysis (C5) | 3 (2.8%) | 8 (4.3%) | 0.502 |
| SSI | 3 (2.8%) | 3 (1.6%) | 0.500 |
| Epidural hematoma | 1 (0.9%) | 2 (1.1%) | 0.899 |
| Dural tear | 0 (0.0%) | 3 (1.6%) | 0.183 |
| Neurological deterioration | 3 (2.8%) | 8 (4.3%) | 0.502 |
Values indicate mean ± standard deviation, *p < 0.05, statistically significant difference.
DCM, degenerative cervical myelopathy; CSM, cervical spondylotic myelopathy; OPLL, ossification of the posterior longitudinal ligament; MRI, magnetic resonance imaging; OD, open-door laminoplasty; DD, double-door laminoplasty; SL, selective laminectomy; EBL, estimated blood loss; SSI, surgical site infection.
Table 6.
Comparison of Neurological and Clinical Outcomes Between Persistent Non-responder and Delayed Responder Group
| | Delayed responder group (n = 108) | Persistent non-responder group (n = 185) | p-value |
|---|---|---|---|
| Cervical JOA score (6 months after surgery) | 12.5 ± 2.4 | 13.0 ± 2.2 | 0.053 |
| Cervical JOA score (2 years after surgery) | 15.0 ± 2.0 | 13.1 ± 2.1 | <0.001*** |
| ΔJOA score (from 6 months to 2 years) | 2.5 ± 1.6 | 0.1 ± 1.2 | <0.001*** |
| VAS (6 months after surgery) | |||
| Pain or stiffness in neck or shoulders (mm) | 39.9 ± 3.0 | 40.6 ± 28.3 | 0.843 |
| Tightness in chest (mm) | 7.6 ± 14.2 | 10.6 ± 18.8 | 0.172 |
| Pain or numbness in arms or hands (mm) | 49.7 ± 30.7 | 52.7 ± 30.7 | 0.458 |
| Pain or numbness in chest to toe (mm) | 37.2 ± 31.8 | 39.3 ± 33.3 | 0.614 |
| NPSI (6 months after surgery) | |||
| Burning | 1.8 ± 2.8 | 2.1 ± 2.8 | 0.316 |
| Pressing | 1.5 ± 2.3 | 1.8 ± 2.3 | 0.312 |
| Paroxysmal | 1.0 ± 1.6 | 1.3 ± 2.1 | 0.184 |
| Evoked | 1.6 ± 2.0 | 1.8 ± 2.4 | 0.335 |
| Paresthesia/dysesthesia | 2.6 ± 2.4 | 2.9 ± 2.8 | 0.280 |
| Total | 16.0 ± 17.0 | 19.5 ± 20.0 | 0.168 |
| JOACMEQ (6 months after surgery) | |||
| Cervical spine function | 77.1 ± 25.6 | 75.0 ± 25.1 | 0.526 |
| Upper extremity function | 83.9 ± 19.5 | 80.5 ± 17.5 | 0.161 |
| Lower extremity function | 68.5 ± 26.1 | 62.8 ± 25.7 | 0.090 |
| Bladder function | 76.0 ± 20.5 | 74.8 ± 18.3 | 0.642 |
| Quality of life | 49.6 ± 19.6 | 46.3 ± 17.1 | 0.167 |
| SF-36 (6 months after surgery) | |||
| PCS | 37.8 ± 10.8 | 34.5 ± 10.8 | 0.024* |
| MCS | 51.8 ± 9.9 | 51.0 ± 9.5 | 0.509 |
Values indicate mean ± standard deviation, * p < 0.05, statistically significant difference.
JOA, Japanese Orthopaedic Association; VAS, visual analog scale; NPSI, Neuropathic Pain Symptom Inventory; JOACMEQ, JOA cervical myelopathy evaluation questionnaire; SF-36, short-form 36; PCS, physical component summary; MCS, mental component summary.
Table 7.
Binary Logistic Regression Analysis of Predictors of Delayed MCID Achievement Among Patients Who Did Not Achieve MCID at 6-Month
| Variable | Odds ratio | 95% CI | p value |
|---|---|---|---|
| JOA score (6 months after surgery) | 0.777 | 0.658–0.918 | 0.003** |
| JOACMEQ Upper extremity function (6 months after surgery) | 1.023 | 1.000–1.047 | 0.044* |
| SF-36 PCS (6 months after surgery) | 1.039 | 1.001–1.078 | 0.045* |
*p < 0.05, ** < 0.01, statistically significant difference.
MCID, minimum clinically important difference; JOA, Japanese Orthopaedic Association; CI; confidence interval, VAS, visual analog scale; JOACMEQ, JOA cervical myelopathy evaluation questionnaire.
Figure 3.
ROC curve for the combined model evaluating factors associated with subsequent MCID achievement. The model included the 6-month JOA score, SF-36 PCS, and JOACMEQ upper extremity function. The AUC was 0.647, indicating modest discriminative ability to identify patients who subsequently achieved the MCID by 2 years among those who had not achieved the MCID at 6 months postoperatively
Discussion
This prospective multicenter study revealed distinct postoperative patterns of neurological recovery after posterior decompression without fusion for DCM among early responders, delayed responders, and persistent non-responders. Notably, approximately one-third of the patients who did not achieve the MCID at 6 months eventually experienced clinically meaningful neurological improvement by 2 years. These findings suggest that early postoperative outcomes do not necessarily predict the final clinical outcome and that neurological recovery extends beyond the early postoperative period in some patients. As the study groups were defined according to MCID achievement at the 2-year follow-up, differences in the 2-year JOA score, ΔJOA, and JOA recovery rate were expected by design and should be interpreted as descriptive rather than confirmatory.
Previous studies, including our previous analysis of the same multicenter registry, have primarily concentrated on identifying associated factors of MCID achievement by examining preoperative factors such as age, comorbidities, symptom duration, and baseline neurological status, or by comparing overall postoperative outcomes between patients who achieved MCID and those who did not.5,7,8,10,19,20 While these studies have offered valuable insights into factors linked to clinically meaningful improvement, they have generally treated MCID achievement as a singular endpoint and have not explored the temporal progression of recovery. Notably, there has been limited focus on patients who do not show early postoperative improvement. This study distinguishes itself by evaluating recovery based on the timing of MCID achievement, categorizing patients into early responders, delayed responders, and persistent non-responders. Additionally, the analysis concentrated on patients who did not achieve MCID at 6 months, examining their subsequent patterns of neurological recovery. Clinically, failing to achieve MCID at 6 months alone may not warrant early conclusions regarding treatment outcomes. While baseline neurological severity is often regarded as a key factor in determining postoperative recovery, our findings indicate that patterns of neurological recovery cannot be solely attributed to the baseline JOA score. Interestingly, patients with lower preoperative JOA scores were more likely to be classified as early responders, whereas those with higher baseline scores were more often categorized as persistent non-responders. This inverse relationship suggests that the potential for measurable improvement and the timing of clinically meaningful recovery are influenced by factors beyond the initial severity, such as postoperative neurological status and functional capacity.
Lower preoperative JOA scores are associated with higher rates of MCID achievement, indicating a greater potential for measurable improvement.7,8,21 Furthermore, better preoperative functional status and PROMs have been linked to more favorable postoperative recovery in patients with DCM.8,22 In this study, among patients who did not achieve MCID at 6 months, binary logistic regression analysis identified three factors associated with subsequent MCID achievement at 2 years: lower JOA scores at 6 months, higher upper extremity function as assessed by the JOACMEQ, and higher PCS scores from the SF-36. Lower JOA scores at 6 months indicated residual neurological impairment. In contrast, better upper extremity function and physical health status suggest preserved motor function and overall physical condition, which may aid in neurological recovery beyond the early postoperative period. One possible explanation is that patients with better physical function may participate more effectively in postoperative rehabilitation programs. However, because rehabilitation practices were not evaluated in the present study, this interpretation should be considered hypothesis-generating. The associations were small for the JOACMEQ upper extremity function and SF-36 PCS and moderate for the 6-month JOA score. Additionally, the combined model demonstrated only modest discriminative ability (AUC = 0.647) with limited sensitivity, indicating that these variables should be regarded as associated factors rather than clinically applicable predictors. External validation and calibration analyses are necessary before such a model can be considered for clinical prediction. The inverse association between higher JOA scores and MCID achievement likely reflects a ceiling effect; with a maximum of 17 points, patients with higher baseline function have limited room for improvement. Thus, failure to reach the MCID may reflect scale constraints rather than poor clinical recovery.
An additional finding of this study was that several symptom-based and patient-reported domains showed no differences among the three groups. Specifically, most pain-related measures were comparable across the groups. Additionally, assessments of bladder function using the JOACMEQ and mental health status using the SF-36 MCS revealed no significant differences at the 2-year postoperative follow-up. These results suggest that improvements in neurological function, as measured by the JOA score, are not related to changes in sensory symptoms, autonomic function, or mental health. Motor function tends to recover after posterior decompression without fusion, whereas sensory symptoms and autonomic function often recover slowly or remain partially impaired.23,24 Moreover, neuropathic pain persists in some patients because of irreversible spinal cord changes, even when neurological improvement is achieved. 25 Clinically, achieving the MCID in neurological function does not guarantee improvements in subjective symptoms or mental health. Therefore, ongoing outpatient management, including pharmacological treatment for neuropathic pain when clinically indicated, may be beneficial after the surgery. However, as postoperative pharmacological management was not evaluated in the present study, the potential influence of such treatments on delayed neurological recovery remains uncertain.
This study had several limitations. First, the surgical strategies were not randomized, which introduced the potential for selection bias. In addition, surgical approach selection was based on surgeon preference and patient characteristics, and the cohort was therefore not strictly consecutive. Unmeasured factors could have influenced both treatment decisions and outcomes. Second, although this was a prospective multicenter study, center-level clustering was not explicitly considered in the statistical analysis. Differences in surgical indications, perioperative management, rehabilitation protocols, and follow-up practices among the participating institutions may have influenced the observed outcomes. Future studies using hierarchical or mixed-effects models could help evaluate the impact of such center effects. Third, only patients who underwent posterior decompression without fusion were included, limiting the generalizability of our findings to other surgical approaches. Fourth, the duration of symptoms was based on patient self-reporting, which introduces the potential for recall bias. Fifth, we applied a uniform MCID threshold of a 2.5-point improvement in the JOA score, although achieving this threshold depends on the baseline neurological status owing to the ceiling effect inherent in the 17-point JOA scale. To minimize this limitation, patients with mild DCM (preoperative JOA score of ≥15) were excluded. Additionally, a sensitivity analysis using the JOA recovery rate as an alternative responder definition yielded findings consistent with the primary analysis, supporting the robustness of our conclusions. However, future studies should further evaluate these findings using other validated responder definitions. Sixth, the follow-up period was limited to 2 years, and long-term outcomes remain uncertain. Seventh, the study cohort consisted entirely of patients treated in Japan, and differences in patient characteristics, surgical practices, and healthcare systems may limit the generalizability of these findings to other populations. Particularly, the relatively high proportion of patients with OPLL and the lower mean BMI observed in this cohort may differ from those in North American populations, where patients are more often overweight or obese, potentially limiting the generalizability of the findings.26-28 Furthermore, postoperative rehabilitation protocols, rehabilitation intensity, outpatient follow-up practices, and pharmacological management, including neuropathic pain medications, were not collected in the present registry. Consequently, we were unable to evaluate their potential influence on delayed neurological recovery or MCID achievement. These factors should be incorporated into future studies. Finally, only patients with complete follow-up data were included, which could introduce attrition bias if those lost to follow-up differed systematically from those who remained in the study. However, a comparison between the included and excluded patients demonstrated no statistically significant differences in demographic, clinical, surgical, or perioperative characteristics (Supplemental Table 3), suggesting that the impact of attrition bias on the present findings is likely limited. Nevertheless, because missing data in longitudinal studies are unlikely to be completely random, the findings should be interpreted cautiously. Future studies employing methods such as mixed-effects models or multiple imputation may further address the issue of missing data. Despite these limitations, this study is strengthened by its large multicenter prospective cohort, the use of validated PROMs, and a study design that enables the assessment of postoperative patterns of neurological recovery, including delayed MCID achievement beyond the early postoperative period.
Conclusion
Among patients with DCM who underwent posterior decompression without fusion, approximately one-third of those who did not reach the MCID at 6 months eventually achieved it by 2 years. Lower JOA scores and better functional and physical status at 6 months were associated with later MCID achievement. Conversely, symptom-based measures, such as pain, sensory disturbance, autonomic function, and mental health status, showed comparable outcomes regardless of MCID achievement. These findings suggest that failing to achieve the MCID at 6 months does not necessarily predict poor long-term outcomes, indicating the importance of continued postoperative follow-up.
Supplemental Material
Supplemental Material for Patterns of Neurological Recovery after Posterior Decompression Without Fusion for Degenerative Cervical Myelopathy According to the Timing of Minimum Clinically Important Difference Achievement by Toshiki Okubo, Narihito Nagoshi, Junichi Yamane, Takahiro Kitagawa, Kanehiro Fujiyoshi, Tatsuya Yamamoto, Kazuya Kitamura, Takeshi Ikegami, Kentaro Ago, Takahito Iga, Kazuki Takeda, Masahiro Ozaki, Satoshi Suzuki, Morio Matsumoto, Masaya Nakamura, Kota Watanabe in Global Spine Journal.
Acknowledgments
We express our sincere gratitude to all participating institutions for their collaboration. In preparing this manuscript, we used ChatGPT (OpenAI) and Grammarly (Grammarly Inc.) to improve grammar and correct typographical errors. These tools were used exclusively to enhance clarity and readability, and did not alter the scientific content or interpretation of the findings. The authors take full responsibility for the content of this manuscript.
Author Contributions: TO contributed to data collection, analysis, and manuscript preparation. NN, JY, MM, MN, and KW supervised the study. TO and NN managed the data. TK, KF, TY, KK, TI, KA, TI, KT, MO, and SS contributed to data collection and provided guidance on the manuscript content.
Funding: The authors received no financial support for the research, authorship, and/or publication of this article.
The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Supplemental Material: Supplemental material for this article is available online.
ORCID iDs
Toshiki Okubo https://orcid.org/0000-0003-0912-7422
Narihito Nagoshi https://orcid.org/0000-0001-8267-5789
Takahiro Kitagawa https://orcid.org/0000-0001-6746-8546
Tatsuya Yamamoto https://orcid.org/0000-0001-9935-9985
Kazuya Kitamura https://orcid.org/0000-0003-0117-4152
Kazuki Takeda https://orcid.org/0000-0003-3857-4985
Kota Watanabe https://orcid.org/0000-0002-4830-4690
Ethical Considerations
The study protocol was approved by the Institutional Review Board (approval number: 20180045).
Consent to Participate
We confirmed that all methods were carried out in accordance with relevant guidelines and regulations. Informed consent was obtained from all subjects.
Data Availability Statement
The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.*
References
- 1.Nouri A, Tetreault L, Singh A, Karadimas SK, Fehlings MG. Degenerative cervical myelopathy: Epidemiology, genetics, and pathogenesis. Spine (Phila Pa 1976). 2015;40(12):E675-E693. doi: 10.1097/BRS.0000000000000913. [DOI] [PubMed] [Google Scholar]
- 2.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;7:70S-83S. doi: 10.1177/2192568217701914. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 3.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 multicenter study. J Bone Joint Surg Am. 2013;95:1651-1658. doi: 10.2106/JBJS.L.00589. [DOI] [PubMed] [Google Scholar]
- 4.Tetreault LA, Kopjar B, Vaccaro A, et al. A clinical prediction model to determine outcomes in patients with cervical spondylotic myelopathy undergoing surgical treatment. J Bone Joint Surg Am. 2013;95:1659-1666. doi: 10.2106/JBJS.L.01323. [DOI] [PubMed] [Google Scholar]
- 5.Zhou F, Zhang Y, Sun Y, Zhang F, Pan S, Liu Z. Assessment of the minimum clinically important difference in neurological function and quality of life after surgery in cervical spondylotic myelopathy patients: a prospective cohort study. Eur Spine J. 2015;24(12):2918-2923. doi: 10.1007/s00586-015-4208-3. [DOI] [PubMed] [Google Scholar]
- 6.Chung AS, Copay AG, Olmscheid N, Campbell D, Walker JB, Chutkan N. Minimum clinically important difference: current trends in the spine literature. Spine (Phila Pa 1976). 2017;42(14):1096-1105. doi: 10.1097/BRS.0000000000001990. [DOI] [PubMed] [Google Scholar]
- 7.Kato S, Oshima Y, Matsubayashi Y, Taniguchi Y, Tanaka S, Takeshita K. Minimum clinically important difference and patient acceptable symptom state of Japanese Orthopaedic Association score in degenerative cervical myelopathy patients. Spine (Phila Pa 1976). 2019;44:691-697. doi: 10.1097/BRS.0000000000002928. [DOI] [PubMed] [Google Scholar]
- 8.Okubo T, Nagoshi N, Yamane J, et al. Achieving the minimum clinically important difference in Japanese Orthopaedic Association score after surgery for degenerative cervical myelopathy: Predictive factors and impact on patient-reported outcome measures. Global Spine J. 2026;16(2):1010-1020. doi: 10.1177/21925682251370640. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 9.Chiba K, Ogawa Y, Ishii K, et al. Long-term results of expansive open-door laminoplasty for cervical myelopathy- -average 14-year follow-up study. Spine (Phila Pa 1976). 2006;31(26):2998-3005. doi: 10.1097/01.brs.0000250307.78987.6b. [DOI] [PubMed] [Google Scholar]
- 10.Tetreault L, Wilson JR, Kotter MR, et al. Predicting the minimum clinically important difference in patients undergoing surgery for the treatment of degenerative cervical myelopathy. Neurosurg Focus. 2016;40(6):E14. doi: 10.3171/2016.3.FOCUS1665. [DOI] [PubMed] [Google Scholar]
- 11.Kato S, Oshima Y, Matsubayashi Y, Taniguchi Y, Tanaka S, Takeshita K. Minimum clinically important difference in outcome scores among patients undergoing cervical laminoplasty. Eur Spine J. 2019;28(5):1234-1241. doi: 10.1007/s00586-019-05945-y. [DOI] [PubMed] [Google Scholar]
- 12.Kobayashi Y, Nagoshi N, Yamane J, et al. Patient demographics of cervical spine surgery in Japan: Prospective multicenter cohort study. World Neurosurg X. 2026;30:100590. doi: 10.1016/j.wnsx.2026.100590. [DOI] [Google Scholar]
- 13.Hirabayashi K, Miyakawa J, Satomi K, Maruyama T, Wakano K. Operative results and postoperative progression of ossification among patients with ossification of cervical posterior longitudinal ligament. Spine (Phila Pa 1976). 1981;6(4):354-364. doi: 10.1097/00007632-198107000-00005. [DOI] [PubMed] [Google Scholar]
- 14.Hirabayashi K, Watanabe K, Wakano K, Suzuki N, Satomi K, Ishii Y. Expansive open-door laminoplasty for cervical spinal stenotic myelopathy. Spine (Phila Pa 1976). 1983;8(7):693-699. doi: 10.1097/00007632-198310000-00003. [DOI] [PubMed] [Google Scholar]
- 15.Bouhassira D, Attal N, Fermanian J, et al. Development and validation of the Neuropathic Pain Symptom Inventory. Pain. 2004;108:248-257. doi: 10.1016/j.pain.2003.12.024. [DOI] [PubMed] [Google Scholar]
- 16.Fukui M, Chiba K, Kawakami M, et al. JOA Back Pain Evaluation Questionnaire (JOABPEQ)/JOA Cervical Myelopathy Evaluation Questionnaire (JOACMEQ). The report on the development of revised versions. April 16, 2007. The Subcommittee of the Clinical Outcome Committee of the Japanese Orthopaedic Association on Low Back Pain and Cervical Myelopathy Evaluation. J Orthop Sci. 2009;14(3):348-365. doi: 10.1007/s00776-009-1337-8. [DOI] [PubMed] [Google Scholar]
- 17.Nikaido T, Kikuchi S, Yabuki S, Otani K, Konno S. Surgical treatment assessment using the Japanese orthopedic association cervical myelopathy evaluation questionnaire in patients with cervical myelopathy: a new outcome measure for cervical myelopathy. Spine (Phila Pa 1976). 2009;34(23):2568-2572. doi: 10.1097/BRS.0b013e3181b35a8e. [DOI] [PubMed] [Google Scholar]
- 18.Fukuhara S, Bito S, Green J, Hsiao A, Kurokawa K. Translation, adaptation, and validation of the SF-36 Health Survey for use in Japan. J Clin Epidemiol. 1998;51:1037-1044. doi: 10.1016/s0895-4356(98)00095-x. [DOI] [PubMed] [Google Scholar]
- 19.Machino M, Ando K, Kobayashi K, et al. Prediction of outcome following laminoplasty of cervical spondylotic myelopathy: Focus on the minimum clinically important difference. J Clin Neurosci. 2020;81:321-327. doi: 10.1016/j.jocn.2020.09.065. [DOI] [PubMed] [Google Scholar]
- 20.Evaniew N, Cadotte DW, Dea N, et al. Clinical predictors of achieving the minimal clinically important difference after surgery for cervical spondylotic myelopathy: an external validation study from the Canadian Spine Outcomes and Research Network. J Neurosurg Spine. 2020;33(2):129-137. doi: 10.3171/2020.2.SPINE191495. [DOI] [PubMed] [Google Scholar]
- 21.Zhang JT, Wang LF, Wang S, Li J, Shen Y. Risk factors for poor outcome of surgery for cervical spondylotic myelopathy. Spinal Cord. 2016;54(12):1127-1131. doi: 10.1038/sc.2016.64. [DOI] [PubMed] [Google Scholar]
- 22.Nagoshi N, Yamane J, Okubo T, et al. Clinical indicators of surgical outcomes in degenerative cervical myelopathy assessed using the JOACMEQ: A prospective multicenter study. Spine (Phila Pa 1976). 2025;50(19):1319-1326. doi: 10.1097/BRS.0000000000005428. [DOI] [PubMed] [Google Scholar]
- 23.Kanematsu R, Hanakita J, Inoue T, et al. Analysis of neurogenic bowel and bladder dysfunction following decompression surgery for cervical spondylotic myelopathy: A prospective cohort study. Global Spine J. 2025;15(2):587-593. doi: 10.1177/21925682231202381. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 24.Setojima Y, Fujii K, Funayama T, et al. Predictive factors for bladder function recovery following cervical OPLL surgery: a comprehensive analysis. Spine J. 2026;26(1):119-125. doi: 10.1016/j.spinee.2025.07.027. [DOI] [PubMed] [Google Scholar]
- 25.Nagoshi N, Yamane J, Okubo T, et al. Prevalence and surgical outcomes of neuropathic pain in degenerative cervical myelopathy: A multicenter prospective cohort study. Spine (Phila Pa 1976). 2026;51(1):9-15. doi: 10.1097/BRS.0000000000005482. [DOI] [PubMed] [Google Scholar]
- 26.Okubo T, Nagoshi N, Yamane J, et al. Do surgical outcomes differ between cervical spondylotic myelopathy and ossification of the posterior longitudinal ligament? A prospective multicenter study of 935 patients with degenerative cervical myelopathy. Spine (Phila Pa 1976). 2025;51:1233-1240. doi: 10.1097/BRS.0000000000005533. Published online 8 October. [DOI] [PubMed] [Google Scholar]
- 27.Wilson JR, Tetreault LA, Schroeder G, et al. Impact of elevated body mass index and obesity on long-term surgical outcomes for patients with degenerative cervical myelopathy: Analysis of a combined prospective dataset. Spine (Phila Pa 1976). 2017;42(3):195-201. doi: 10.1097/BRS.0000000000001859. [DOI] [PubMed] [Google Scholar]
- 28.Okubo T, Nagoshi N, Yamane J, et al. Body mass index and surgical outcomes in degenerative cervical myelopathy: Findings from a prospective multicenter cohort of 935 patients. Spine (Phila Pa 1976). 2025. doi: 10.1097/BRS.0000000000005554. Published online 3 November 2025 [DOI] [PubMed] [Google Scholar]
Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Supplementary Materials
Supplemental Material for Patterns of Neurological Recovery after Posterior Decompression Without Fusion for Degenerative Cervical Myelopathy According to the Timing of Minimum Clinically Important Difference Achievement by Toshiki Okubo, Narihito Nagoshi, Junichi Yamane, Takahiro Kitagawa, Kanehiro Fujiyoshi, Tatsuya Yamamoto, Kazuya Kitamura, Takeshi Ikegami, Kentaro Ago, Takahito Iga, Kazuki Takeda, Masahiro Ozaki, Satoshi Suzuki, Morio Matsumoto, Masaya Nakamura, Kota Watanabe in Global Spine Journal.
Data Availability Statement
The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.*