Correlation of Myelopathy to Regional Neck Disability: A Surgical Approach-Specific Analysis in 217 Patients

Introduction Outcomes for cervical spondylotic myelopathy (CSM) have been measured by numerous health-related quality of life (HRQOL) scales such as the disease-specific modified Japanese Orthopaedic Association (mJOA) and the regional-specific neck disability index (NDI). However, there is no literature analyzing the correlation of myelopathy improvement to regional neck disability changes after surgery.Materials and Methods Post hoc analysis of a prospective, multicenter database of patients with CSM. A total of 217 patients (78%) met the following inclusion criteria: symptomatic CSM, age over 18 years, and 6 months follow-up with mJOA and NDI. The patient population had a mean age of 57 years and 42% were females (n= 92). NDI and mJOA were analyzed at baseline and 6 months post-op for the entire group. Correlations were also analyzed by the following subgroups: anterior approach group (AAG, n= 141) and posterior approach group (PAG, n= 76).Results From baseline to 6 months, there was a statistically significant improvement in both mJOA (BL 12.87–6 M 15.25, p< 0.0001) and NDI (BL 42.25–6M 31.61, p< 0.0001) in the overall group. There was a significant small negative correlation between NDI and mJOA at baseline (R=  − 0.34, p< 0.0001) and at 6-month follow-up (R=  − 0.44, p< 0.0001). Within the AAG, there was also a significant negative correlation between NDI and mJOA at baseline (R=  − 0.31, p< 0.0001) and 6 months (R=  − 0.53, p< 0.0001). Within the PAG, there was also a significant negative correlation between NDI and mJOA at baseline (R=  − 0.43, p< 0.0001) and 6 months (R=  − 0.34, p= 0.003).Conclusion Overall, NDI has a significant negative correlation with mJOA at baseline and postoperatively in patients with CSM. This correlation increases postoperatively in the overall group. The PAG showed a decrease in the correlation coefficient after surgery, whereas the AAG showed an increase. This could be because the posterior approach tended to be a more extensive surgery for multilevel disease in older patients, compared with the anterior approach, resulting in more soft tissue disruption and a delay in neck active motion. Regardless of the approach, mJOA still remains significantly correlated with NDI.