Performance-Based Functional Outcomes 12 and 24 Months After Transfemoral Osseointegration in Service Members With Traumatic Unilateral and Bilateral Lower Limb Loss

Objective: To evaluate functional outcomes at 12 months and 24 months after transfemoral osseointegration (OI) using established performance-based assessments. Design: Pre-post observational single cohort. Setting: Military treatment facility. Participants: Forty-seven (N=47) service members (mean age ± SD, 38±9y) with traumatic unilateral (n=22) and bilateral (n=25) lower limb loss. Before OI, n=2 unilateral and n=7 bilateral were not ambulatory on full-length prostheses. Interventions: Transfemoral OI (2-stage threaded implant). Main Outcome Measures: Six-Minute Walk Test (6MWT), timed Up and Go (TUG), 4 Square Step Test (4SST), (Bilateral) Amputee Mobility Predictor ([B]AMP), and Comprehensive High-level Activity Mobility Predictor (CHAMP). Results: For both unilateral and bilateral cohorts, the median performance-based functional outcomes were similar at 12 months and 24 months after vs before OI: 6MWT (373 and 385 m vs 417 m; p>.31), TUG (9.7 and 9.6s vs 9.8s; p>.53), 4SST (9.5 and 10.6s vs 10.8s; p>.11), and CHAMP (12.6 and 10.6 vs 12.3; p>.44). Median BAMP scores were greater at 12 months (p=.029) and 24 months (p=.014) after vs before OI among the bilateral cohort (30 and 35 vs 16); median AMP scores were similar (p>.10) among the unilateral cohort across time points (39 and 43 vs 40). Among the 9 participants not ambulating with full-length prostheses before OI, 8 became capable of ambulation on full-length prostheses 24 months after OI. Conclusions: While a lack of improvement in these particular outcomes is not exclusively suboptimal, particularly considering the median scores at baseline reported here generally exceeded those of other cohorts (both before and sometimes even after OI), these findings contrast with previous self-reported improvements in function after OI among service members with traumatic lower limb loss. As such, these data seemingly emphasize the importance of a comprehensive approach with both subjective and objective (multidisciplinary) outcomes to more fully characterize OI, particularly within unique patient populations like young service members with traumatic lower limb loss.