Low body mass index is a risk factor for increased post-operative mortality and poor functional improvement in distal femur fractures among patients aged over 65: A multicentre (TRON) study.

BACKGROUND

Distal femur fractures have been reported to have a mortality rate comparable to hip fractures, but the risk is still unknown. Recent studies have reported that low body mass index (BMI) is a risk factor for mortality in the elderly. We investigated the efficacy of low BMI for predicting the risk of mortality in distal femur fractures in patients aged over 65 within 18 months after injury and its impact on postoperative clinical outcomes and mortality.

METHODS

Data from patients followed for more than six months were obtained from our trauma research group's database. We investigated risk factors for increased mortality using Cox proportional hazards models. We divided the analysed cases into low (<18.5 kg/m) and high (>18.5 kg/m) BMI groups. We adjusted the background characteristics of the groups by patient matching, and evaluated the postoperative mortality, complication rate, and knee society score (KSS).

RESULTS

We identified 216 patients, including 58 (26.9%) with low BMI values. Low BMI was an independent risk factor for mortality in all models (Hazard Ratio: 2.9, p = 0.011). The overall survival rate of the low BMI group at 18 months was significantly lower than that of the high BMI group (70.7% vs. 89.1%; p = 0.003). The complication rates of the low BMI and high BMI groups were not significantly different (33.3% vs. 22.2%; p = 0.283). The mean KSS values at 3, 6, and 12 months in the low BMI group was significantly worse than that in the high BMI group (78.7 ± 16.2 vs. 84.8 ± 13.1; p = 0.035, 82.2 ± 16.9 vs. 89.7 ± 8.9; p = 0.005, 86.4 ± 13.0 vs. 91.4 ± 8.4; p = 0.020, respectively).

CONCLUSIONS

Our study indicated that low BMI was independent associated with increased mortality and impaired postoperative functional recovery in distal femur fractures of the elderly patients.