Association of Spinal Alignment Correction With Patient-Reported Outcomes in Adult Cervical Deformity: Review of the Literature.

Objective Adult cervical deformity (ACD) is a debilitating spinal condition that causes significant pain, neurologic dysfunction, and functional impairment. Surgery is often performed to correct cervical alignment, but the optimal amount of correction required to improve patient-reported outcomes (PROs) are not yet well-defined. Methods A review of the literature was performed and Fisher's z-transformation (Zr) was used to pool the correlation coefficients between alignment parameters and PROs. The strength of correlation was defined according to the following: poor (0 < r ≤ 0.3), fair (0.3 < r ≤ 0.5), moderate (0.5 < r ≤ 0.8), and strong (0.8 < r ≤ 1). Results Increased C2-C7 SVA was fairly associated with increased Neck Disability Index (NDI) (pooled Zr = 0.31; 95% CI, -0.03, 0.58). Changes in TS-CL poorly correlated with NDI (pooled Zr = -0.04; 95% CI, -0.23-0.30). Increased C7-S1 was poorly associated with worse EQ-5D (pooled Zr = -0.22; 95% CI, -0.36, -0.06). Correction of horizontal gaze (CBVA) did not correlate with legacy metrics. mJOA correlated with C2-slope, C7-S1, and C2-S1. Conclusion Spinal alignment parameters variably correlated with improved HRQoL and myelopathy after corrective surgery for ACD. Further studies evaluating legacy PROs, PROMIS, and ACD specific instruments are needed for further validation.