Utility of Psoas Muscle Index as Predictor of Worse Outcomes Following Major Amputation from Peripheral Vascular Disease.

BACKGROUND: Frailty has been reported as a predictor of adverse outcomes after various surgical procedures. There are several models for defining frailty, including 5-factor modified frailty index, clinical frailty scale, and psoas muscle index. Low psoas muscle index has been associated with higher postoperative mortality and complications after various surgical procedures. Our objective was to assess psoas muscle index as a predictor of outcomes after major amputation in patients with peripheral vascular disease.

METHODS: We performed retrospective chart review of patients with peripheral vascular disease who underwent major amputation at a safety-net hospital from 2016 to 2022. Psoas index was evaluated based on computed tomography scans within 6 months of amputation. Outcomes included postoperative 30-day mortality, wound complications, respiratory complications, cardiac complications, and 1-year mortality. Psoas muscle index was calculated using psoas muscle area measured from computed tomography scans at the level of the L4 vertebral body divided by the body surface area. Univariate and multivariate analysis was used to compare postoperative outcomes by gender and by psoas muscle index.

RESULTS: A total of 106 patients were analyzed (68 males, 38 females). Females had higher rates of above-knee amputation (AKA) compared to males (55.2% vs. 27.9%, P = 0.04). Males had a significantly higher baseline mean psoas muscle index compared to females (1,088 mm2/m2 vs. 787 mm2/m2, P < 0.01). AKA within 30 days (20% vs. 10.8%, P = 0.05) and respiratory complications (9.5% vs. 1.2%, P = 0.04) were more likely in patients with low psoas muscle index compared to those with high psoas muscle index when low psoas muscle index was defined as the lowest 20th percentile of patients. Females with a low psoas muscle index were more likely to have wound complications (60% vs. 21%, P = 0.03). Females were more likely to require AKA within 30 days after below knee amputation (19.4% vs. 9%, P = 0.02) and have a higher rate of mortality at 1 year (45.8% vs. 23.1%, P = 0.04) compared to males regardless of psoas index.

CONCLUSIONS: Our results demonstrate that low psoas muscle index is associated with worse outcomes after major amputation for peripheral vascular disease, particularly in female patients. These data may be helpful for preoperative risk assessment and decision-making regarding amputation level.