Supplemental Digital Content 1. Patient demographics and surgical characteristics based on achieving a minimum clinically important difference improvement in the modified Japanese Orthopaedic Association score following surgery.
No MCID Improvement
N=170 MCID Improvement
N=204 P-Value
Follow-Up (years) 2.12 (1.63) 1.98 (1.57) 0.398
Sex (female) 73 (42.9%) 110 (53.9%) 0.044*
Age (years) 61.3 (9.98) 58.0 (10.5) 0.002*
Body Mass Index 30.7 (6.15) 30.2 (5.92) 0.479
Charlson Comorbidity Index 0.74 (0.96) 0.62 (1.02) 0.252
Diabetes 32 (18.8%) 31 (15.2%) 0.427
Smoking Status: 0.119
Current Smoker 15 (8.82%) 16 (7.84%)
Former Smoker 58 (34.1%) 51 (25.0%)
Non-smoker 97 (57.1%) 137 (67.2%)
Symptom Duration: 0.408
< 1 Year 99 (58.2%) 109 (53.4%)
> 1 Year 71 (41.8%) 95 (46.6%)
Concomitant Radiculopathy 49 (28.8%) 82 (40.2%) 0.029*
Baseline mJOA Severity: 0.091
Mild 84 (49.4%) 85 (41.7%)
Moderate 58 (34.1%) 67 (32.8%)
Severe 28 (16.5%) 52 (25.5%)
Levels Fused 2.20 (0.99) 2.43 (0.95) 0.026*
Revision Surgery 3 (1.76%) 6 (2.94%) 0.519
Hospital Readmission 5 (2.94%) 6 (2.94%) 1.000
*Indicates statistical significance (p<0.05).
Abbreviations: Minimum Clinically Important Difference (MCID), Modified Japanese Orthopaedic Association score (mJOA)
Supplemental Digital Content 2. Patient demographics and surgical characteristics for patients with mild myelopathy
Preoperative mJOA 15-16
Preoperative mJOA 17
P-Value
N=107 N=62
Follow-Up (years): 1.88 (1.52) 2.08 (1.75) 0.738
Sex: 0.216
Female 48 (44.9%) 21 (33.9%)
Male 59 (55.1%) 41 (66.1%)
Age (years): 57.3 (11.0) 59.5 (9.64) 0.177
BMI (kg/m2): 29.3 (5.71) 28.9 (5.10) 0.792
CCI: 0.50 (0.86) 0.65 (0.94) 0.321
Diabetes: 15 (14.0%) 8 (12.9%) 1.000
Smoking Status: 0.690
Current Smoker 7 (6.54%) 6 (9.68%)
Former Smoker 29 (27.1%) 18 (29.0%)
Non-Smoker 71 (66.4%) 38 (61.3%)
Symptom Duration: 1.000
< 1 Year 61 (57.0%) 35 (56.5%)
> 1 Year 46 (43.0%) 27 (43.5%)
Concomitant Radiculopathy: 37 (34.6%) 20 (32.3%) 0.890
Levels Fused: 2.20 (0.99) 2.21 (0.94) 0.748
Revision Surgery: 2 (1.87%) 1 (1.61%) 1.000
Hospital Readmission: 2 (1.87%) 0 (0.00%) 0.533
*Indicates statistical significance (p<0.05).
Supplemental Digital Content 3. Multivariate linear regression identifying magnitude of improvement of clinical outcomes for patients with mild myelopathy. Patients are stratified into modified Japanese Orthopaedic Association scores of 15-16 or 17.
PCS-12 MCS-12 NDI VAS Arm VAS Neck
Predictors Estimate 95% CI P-Value Estimate 95% CI P-Value Estimate 95% CI P-Value Estimate 95% CI P-Value Estimate 95% CI
Preoperative mJOA
15-16 Ref. Ref. Ref. Ref. Ref.
17 1.10 -2.23 – 4.43 0.519 0.67 -3.11 – 4.44 0.729 -2.24 -7.66 – 3.18 0.420 0.49 -0.54 – 1.53 0.349 0.27 -0.62 – 1.15
Age -0.09 -0.24 – 0.06 0.254 -0.02 -0.19 – 0.16 0.837 0.14 -0.11 – 0.39 0.279 0.01 -0.03 – 0.06 0.525 -0.002 -0.04 – 0.04
Male Sex -2.38 -5.83 – 1.07 0.178 -1.53 -5.44 – 2.38 0.444 2.21 -3.43 – 7.85 0.443 0.07 -0.98 – 1.13 0.890 0.51 -0.40 – 1.42
BMI -0.22 -0.51 – 0.08 0.147 -0.17 -0.51 – 0.16 0.314 -0.09 -0.57 – 0.39 0.718 0.02 -0.08 – 0.11 0.731 -0.02 -0.10 – 0.06
Symptom Duration
< 1 Year Ref. Ref. Ref. Ref. Ref.
> 1 Year 3.53 0.20 – 6.85 0.039* -0.08 -3.85 – 3.69 0.966 -9.69 -15.13 – -4.25 <0.001* -0.52 -1.55 – 0.50 0.320 -0.88 -1.76 – 0.01 Radiculopathy 2.60 -0.81 – 6.01 0.137 0.48 -3.39 – 4.35 0.809 -4.67 -10.26 – 0.90 0.102 -1.61 -2.66 – -0.55 0.003* -0.26 -1.18 – 0.65 Levels Fused 0.81 -0.83 – 2.45 0.334 -1.23 -3.10 – 0.63 0.196 -0.95 -3.66 – 1.75 0.491 -0.13 -0.64 – 0.39 0.627 -0.38 -0.82 – 0.06
BMI: body-mass index
*Indicates statistical significance (p<0.05)
Supplemental Digital Content 4. Multivariate linear regression for one-year postoperative patient reported outcome measures.
Predictor MCS-12 P-Value PCS-12 P-Value NDI P-Value VAS Neck P-Value
mJOA Severity:
Mild Reference Reference Reference Reference
Moderate -1.73 0.175 -2.04 0.082 4.42 0.015* 0.73 0.005*
Severe -4.10 0.009* -4.66 0.001* 8.91 <0.001* 0.87 0.008*
mJOA MCID Improvement 3.98 0.001* 5.95 <0.001* -11.00 <0.001* -0.76 0.001* Age (years) 0.39 <0.001* 0.50 <0.001* 0.50 <0.001* 0.33 <0.001*
Sex (male) 0.13 0.018* -0.03 0.586 -0.16 0.036* -0.04 0.001*
Body Mass Index 1.22 0.276 1.22 0.223 -1.66 0.290 -0.05 0.839
Levels Fused 0.00 0.982 -0.09 0.294 -0.13 0.335 -0.02 0.406
Symptom Duration > 1 Year -0.32 0.567 0.18 0.721 -0.30 0.704 -0.06 0.630
Radiculopathy -0.44 0.694 0.38 0.708 -1.40 0.379 -0.11 0.639
Baseline PROM Score -2.40 0.040* 0.28 0.785 0.47 0.774 0.06 0.795
*Indicates statistical significance (p<0.05).
∆: One-year postoperative value minus preoperative value
Abbreviations: Mental Health Component Score (MCS-12), Minimum Clinically Important Difference (MCID), modified Japanese Orthopaedic Association (mJOA), Neck Disability Index (NDI), Patient Reported Outcome Measure (PROM), Physical Health Component Score (PCS-12), Visual Analog Scale (VAS)