The Effect of Patient Age on Recovery Kinetics in 149 Adult Spinal Deformity Patients with 2-Year Follow-Up: A Novel Area under the Curve Analysis

Abstract

Introduction Elderly patients (pts) with adult spinal deformity (ASD) have worse baseline health-related quality of life (HRQOL) measures than younger patients. Current methods of reporting outcomes are limited to static time points perhaps diminishing the health impact of the entire postoperative recovery experience. This study aims to identify the effect of age on the recovery kinetics by examining the effect of HRQOL over time via an area under the curve analysis (AUC). Materials and Methods A retrospective review of a multicenter, prospective ASD database was included. The inclusion criteria included patients with ASD and ≥ 18 years. Patients were stratified by the following age groups: ≤ 45, 46 to 64, 65 to 74, ≥ 75 years. HRQOL collected included Oswestry Disability Index (ODI), Short Form-36 (PCS/MCS), and Scoliosis Research Society-22 (SRS22) at baseline, 6 weeks, 1 and 2 years, postoperatively. All HRQOL was normalized to each patients' baseline scores as a comparison relative to where the patients started. An AUC was then calculated across the entire 2 years. Standard HRQOL and AUC means were compared between the groups. Results A total of 149 pts met inclusion criteria (≤ 45:32, 46 to 64:67, 65 to 74:38, ≥75:12). Older patients had significantly worse pre-op ODI, PCS, SRS activity, pain, and total compared with their respective younger age groups ( p < 0.05 for all) with the exception of 65 to 74 versus ≥ 75 and 46 to 64 versus 65 to 74 ( p > 0.05 for all). All age groups significantly improved all HRQOL at 2 years compared with pre-op ( p < 0.05 for all) except SRS mental and MCS for all age groups and ODI and SRS activity for ≤45 ( p > 0.05). However, normalized 2-year AUC HRQOL for the younger pts was worse than their respective older age groups for ODI, PCS, SRS activity, pain, and total. Conclusion On the basis of the static HRQOL analysis, all the age groups improved HRQOL at 2 years following surgery with older pts having worse pre-op HRQOL than younger pts. AUC analysis, however, suggests that the recovery kinetics is significantly worse for younger pts than the older pts.