Probability of Severe Frailty Development among Operative and Non-Operative Adult Spinal Deformity Patients: An Actuarial Survivorship Analysis over a 3-year Period.

BACKGROUND: Little is known of how frailty, a dynamic measure of physiological age, progresses relative to age or disability status. Operative treatment of adult spinal deformity (ASD) may play a role in frailty remediation and maintenance.

PURPOSE: Compare frailty status, severe frailty development, and factors influencing severe frailty development among ASD patients undergoing operative or non-operative treatment.

DESIGN: Retrospective review with maximum follow up of 3 years.

SETTING: Prospective, multicenter, ASD database.

PARTICIPANTS: Patients were consecutively enrolled from 13 participating centers.

INCLUSION CRITERIA: ≥18 years undergoing either operative or non-operative treatment for ASD, exclusion criteria: spinal deformity of neuromuscular etiology, presence of active infection, or malignancy. The mean age of the participants analyzed were 54.9 for the operative cohort and 55.0 for the non-operative cohort.

MAIN OUTCOMES: Frailty status, severe frailty development and factors influencing severe frailty development.

METHODS: ASD patients (coronal scoliosis≥20°, sagittal vertical axis (SVA)≥5cm, Pelvic Tilt (PT)≥25°, or thoracic kyphosis≥60°) >18y/o, with Base Line (BL) frailty scores were included. Frailty was scored from 0-1 (not frail: <0.3, frail 0.3-0.5, severe frailty >0.5) through the use of ASD-FI which has been validated using the International Spine Study Group (ISSG) ASD database, European Spine Study Group (ESSG) ASD database, and the Scoli-RISK-1 Patient Database. The International Spine Study Group (ISSG) is funded through research grants from DePuy Synthes and individual donations, and supported the current work. Operative (Op) and Non-Operative (Non-Op) patients were propensity matched. T-tests compared frailty among treatment groups and BL, 1Y, 2Y, and ≥3Y. An actuarial Kaplan-Meier survivorship analysis with Log Rank (Mantel-Cox) test, adjusting for patients lost to follow-up, determined probability of severe frailty development. Multivariate Cox Regressions gauged the effect of sagittal malalignment, patient and surgical details on severe frailty development.

RESULTS: The analysis includes 472 patients (236 Op, 236 Non-Op) selected by propensity score matching from a cohort of 1172. Demographics and comorbidities were similar between groups (p>0.05). Op exhibited decreased frailty at all follow up intervals compared to BL (BL:0.22 vs Y1:0.18; Y2:0.16; Y3:0.15, all p<0.001). Non-Op displayed similar frailty from BL to 2Y follow up, and increased frailty at 3Y follow up (0.23 vs 0.25, p=0.014). Compared to Non-Op, Op had lower frailty at 1Y (0.18 vs 0.24), 2Y (0.16 vs 0.23) and 3Y (0.15 vs 0.25) (all p<0.001). Cumulative probability of maintaining non-severe frailty was (Op:97.7%, Non-Op:94.5%) at 1Y, (Op:95.1%, Non-Op:90.4%) at 2Y, and (Op:95.1%, Non-Op:89.1%) at ≥3Y, (p=0.018). Amongst all patients, baseline depression (HR: 2.688[1.172-6.167], p=0.020), NRS back pain scores (HR: 1.247[1.012-1.537], p=0.039), and non-operative treatment (HR: 2.785[1.167-6.659], p=0.021) predicted severe frailty development with having a HR>1.0 and p-value<0.05. Among operative patients, 6-week postoperative residual SVA malalignment (SRS-Schwab SVA + modifier) (HR: 15.034[1.922-116.940], p=0.010) predicted severe frailty development indicated by having a HR>1.0 and p-value <0.05.

CONCLUSIONS: Non-Op patients were more likely to develop severe frailty, and at a quicker rate. Baseline depression, increased NRS back pain scores, non-operative treatment, and postoperative sagittal malalignment at 6-week follow-up significantly predicted severe frailty development. Operative intervention and postoperative sagittal balance appear to play significant roles in frailty remediation and maintenance in adult spinal deformity patients. Frailty is one factor, in a multifactorial conservation, that may be considered when determining operative or non-operative values for ASD patients. Operating before the onset of severe frailty, may result in a lower complication risk and better long term clinical outcomes.

LEVEL OF EVIDENCE: III.