<black square>OBJECTIVE: To determine extent of improvement in the Oswestry Disability Index (ODI) required to achieve patient satisfaction among frail patients undergoing lumbar fusion surgery. METHODS: This retrospective study recruited consecutive patients who underwent lumbar fusion surgery from June 2020 to July 2022. Patient-and procedure-specific variables were included. Baseline and 3-month ODI was assessed. Patient satisfaction was assessed at 1 year after surgery. Multivariable logistic regression adjusting for age, sex, and body mass index was conducted to determine the impact of frailty on patient satisfaction. Receiver operating characteristic analysis determined threshold values for relative ODI improvement and postoperative ODI indicative of patient satisfaction. RESULTS: The final analysis included 418 patients with mean (SD) age of 70.4 (11.1) years. Median [interquartile range] baseline preoperative ODI was 57.5 [37.5-65.0] with ODI of 17.5 [7.5-27.7] at 3 months after surgery. Median improvement in ODI was 42.5 [22.5-53.1], and relative ODI improvement was 68.7 [41.2-75.3]. Among nonfrail/prefrail patients, those with higher baseline ODI (odds ratio 1.24, 95% confidence interval 1.04-1.64, P < 0.001) had significantly higher probability of experiencing postoperative satisfaction. However, frail patients with lower baseline ODI (odds ratio 0.92, 95% confidence interval 0.87-0.96, P < 0.001) were more likely to experience postoperative satisfaction. In nonfrail/prefrail patients, postoperative ODI 526 with sensitivity of 80% and specificity of 71% or relative ODI improvement >= 55% with sensitivity of 74% and specificity of 68% was associated with patient satisfaction. Accordingly, in frail patients, postoperative ODI 517 with sensitivity of 75% and specificity of 65% or relative ODI improvement >= 67% with sensitivity of 71% and specificity of 69% was linked to patient satisfaction. CONCLUSIONS: Frail patients with lower preoperative ODI were significantly more likely to experience postoperative satisfaction, whereas nonfrail/prefrail patients with higher preoperative ODI were significantly more likely to experience postoperative satisfaction. Among frail patients, relative ODI improvement z67% or postoperative ODI 517 indicated patient satisfaction; in nonfrail/prefrail patients, relative ODI improvement z55% or postoperative ODI 526 indicated patient satisfaction.