Achievement of Minimum Clinically Important Difference for Modified Japanese Orthopaedic Association Score Following Posterior Cervical Decompression and Fusion

Introduction: Posterior cervical decompression and fusion (PCDF) is commonly utilized for myelopathy. The modified Japanese Orthopaedic Association (mJOA) score is a patient reported outcome measure (PROM) that is useful for myelopathy. The minimum clinically important difference (MCID) quantifies the smallest PROM change associated with patient-appreciable improvement. This study aimed to compare surgical outcomes and PROMs based on preoperative myelopathy severity and identify predictors of achievement of MCID postoperatively.

Methods: Adult patients who underwent elective PCDF at a tertiary center with available PROMs were retrospectively identified (2010-2022). Surgeries indicated for trauma, tumor, infection, or combined anterior-posterior approaches were excluded. Patients were categorized into mild, moderate, or severe myelopathy cohorts, per preoperative mJOA score. MCID thresholds were 1, 2, and 3 mJOA points, for mild, moderate, and severe patients, respectively—per prior literature. Demographic, surgical variables, outcomes, and PROMs were collected. Descriptive statistics and linear regressions were performed (alpha 0.05).

Results: 137 patients were included (62 mild, 48 moderate, 27 severe)—groups were demographically similar. Severe myelopaths had longer length of stay (3.16  1.18 (severe) vs. 2.66  1.76 (mild) and 3.151.84 (moderate) days, p=0.016), and higher likelihood of achieving MCID at 1-year postoperatively (51.9% (severe) vs. 22.6% (mild) and 45.8% (moderate), p=0.008). Improvements in mJOA score were significantly greater for the severe cohort at all time points, up to 2 years postoperatively. Linear regression identified moderate and severe myelopathy as independently predictive of greater mJOA improvement compared to mild.

Conclusion : Although the severe cohort had longer hospital stay postoperatively, they reached 1-year MCID at higher rates and experienced consistent improvement in mJOA. Groups were similar in surgical characteristics, complications, and reoperation. Surgeons should counsel patients regarding the benefit of surgical intervention for myelopathy, regardless of severity. Surgery can provide noticeable improvement in symptoms without obvious increase in surgical risks.