Influence of transfemoral amputation length on resulting loads at the osseointegrated prosthesis fixation during walking and falling

Background: Transfemoral amputation is a surgical measure in which the surgeon typically conserves as much tissue and bone as possible. Osseointegrated fixation of prostheses is a promising alternative to conventional socket-based fixation. However, osseointegrated prostheses pose some risk of possible bone fracture under unexpected high-impact loading scenarios, such as a fall, and this should be protected against by a safety element. The aim of the present study was to determine the effect of amputation height on the forces and moments at the bone-prosthesis interface during normal gait and three falling scenarios.

Methods: Forces and moments at four amputation heights were determined from a multi-body simulation driven by data captured from an able-bodied participant.

Findings: In all three falling scenarios, forces were relatively independent of amputation height, while moments generally displayed considerable increases with shorter residual limb length. Peak moments ranged from 105Nm (SD 75) (most distal amputation height) to 229Nm (SD 99) (most proximal amputation height) for a "falling during gait" scenario.

Interpretation: Our findings reveal the dependence of interface loads on amputation height in normal gait and falling. This information may lead to improved prosthesis safety elements against bending moments.