Does the Presence of Preoperative Myelomalacia Impact Outcomes Following ACDF?

Abstract

Retrospective cohort. To compare outcomes after ACDF amongst patients with versus without preoperative myelomalacia. Evidence correlating preoperative myelomalacia with postoperative patient-reported outcome measures (PROMs) after anterior cervical discectomy and fusion (ACDF) is limited. Patients who underwent primary, elective ACDF for myelopathy with 1-year follow-up were included. PROMs were collected at 3/6/12 months, including: Modified Japanese Orthopaedic Association (mJOA), Neck Disability Index (NDI), Visual Analog Scale (VAS) Neck and Arm, and SF-12 Physical (PCS) and Mental (MCS) Component Summary. Preoperative myelomalacia was identified via keyword search and manual chart review. Myelomalacia and non-myelomalacia groups were compared on bivariable and multivariable analyses. A sub-analysis was performed comparing outcomes between single versus multilevel myelomalacia. 518 patients were included (163 with myelomalacia). Groups were similar for MCS and mJOA at all time points. Myelomalacia patients demonstrated lower VAS neck scores at 1 year (2.11±2.32 vs. 2.58±2.40, P=0.034), less common achievement of MCID for 1-year NDI (48.5% vs. 60.3%, P=0.015), and improved 1-year PCS scores (40.2±11.7 vs. 37.8±10.8, P=0.024). Multivariable regression demonstrated that MCID for mJOA and NDI was predicted only by preoperative PROM scores and/or demographic variables. Patients with 2+ levels of myelomalacia had worse preoperative mJOA scores (12.3±3⊡66 vs. 14.3±3⊡25, P=0.008) but more common achievement of MCID at 3 months (78.6% vs. 41.7%, P=0.042) when compared to those with single-level myelomalacia. However, multivariate analyses demonstrated that only higher preoperative mJOA independently decreased 3-month mJOA improvement (estimate: -0.54, P=0.011 for 3 mo and estimate: -0.73, P<0.001 for 1 y). Myelomalacia was associated with similar mJOA improvement but less NDI improvement, which was attributable to smoking status and less severe baseline disease. Multisegmental myelomalacia correlated with worse baseline mJOA, but only preoperative mJOA impacted mJOA improvement on multivariable analysis. Myelomalacia alone does not appear to negatively impact PROMs after ACDF for myelopathy.