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 sig-nificant pain, neurologic dysfunction, and functional impairment. Surgery is often per -formed to correct cervical alignment, but the optimal amount of correction required to im -prove patient-reported outcomes (PROs) are not yet well-defined. Methods: A review of the literature was performed and Fisher 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 C2-7 sagittal vertical axis was fairly associated with increased Neck Dis-ability Index (NDI) (pooled Zr = 0.31; 95% confidence interval [CI],-0.03 to 0.58). Chang-es in T1 slope minus cervical lordosis poorly correlated with NDI (pooled Zr =-0.04; 95% CI,-0.23 to 0.30). Increased C7-S1 was poorly associated with worse EuroQoL 5 -Dimen-sion (pooled Zr =-0.22; 95% CI,-0.36 to-0.06). Correction of horizontal gaze did not correlate with legacy metrics. Modified Japanese Orthopedic Association correlated with C2-slope, C7-S1, and C2-S1. Conclusion: Spinal alignment parameters variably correlated with improved health-related quality of life and myelopathy after corrective surgery for ACD. Further studies evaluating legacy PROs, Patient-Reported Outcomes Measurement System, and ACD specific instru-ments are needed for further validation.