Multi‐body simulation of various falling scenarios for determining resulting loads at the prosthesis interface of transfemoral amputees with osseointegrated fixation

Abstract

Conventionally, transfemoral amputees are treated with a shaft prosthesis fitted over the residual limb. To improve the quality of life of such patients, in particular those with complications relating to conventional attachment (e.g., skin irritation, stump ulcers, and poor motor-control with short stumps), osseointegrated prosthesis fixation implants have been developed and implanted in a limited population of patients. To assess possible damage to the implant/prosthesis during falling scenarios, the loads in high-risk situations were estimated using a multi-body simulation of motion. Five falling scenarios were identified and performed by healthy volunteer wearing safety equipment. Kinematic data and ground reaction forces were captured as input for the inverse-dynamics-based simulations, from which the forces and moments at a typical implant-prosthesis interface location were computed. The estimated peak loads in all five scenarios were of a magnitude that could lead to bone fracture. The largest peak force observed was 3274 ± 519 N, with an associated resultant moment of 176 ± 55 Nm on the prosthesis-implant interface. A typical femur is prone to fracture under this load, thus illustrating the need for a safety-release element in osseointegrated prosthesis fixation.

Stiffness and ultimate load of osseointegrated prosthesis fixations in the upper and lower extremity

“…Compared to previous findings regarding loads at the osseointegrated prosthesis fixation of the lower extremity during falling [12], the present results illustrate the high risk of fracture. Welke et al reported bending moments at the osseointegrated prosthesis fixation of up to 176 Nm for forward falling on one knee and 187 Nm for falling backwards.…”

“…Therefore our findings underline the need for the use of a safety element to prevent such fractures as they are related to complicated revision and in the long term a substantial loss of quality of life. The ultimate bending moments observed are considerably below simulated resulting peak moments for dynamic falling scenarios [12], and it should be considered that the duration of load application during falling is range of hundreds of milliseconds.…”

“…Typical falling scenarios [9] generate bending moment as predominate loads [10-12] which could lead to periprosthetic fractures [13] and implant failure [14]. Risk analysis and self-reported questionnaires concerning additional loads have identified axial pulling forces as likely to occur while catching one’s foot [15].…”

Adaptive Sports Technology and Biomechanics: Prosthetics

“…This prosthesis was tested in 5 falling scenarios, with estimated peak loads in all 5 scenarios of a magnitude that could lead to bone fracture. Therefore it is imperative to add a safety‐release element in osseointegrated prosthesis fixation [49].…”

Simulation Case Study: Using Simscape for Human Knee Joint Models

“…Results gained from these models can be used in the development of prostheses to improve functions of leg prostheses. For example, multibody models are developed for the investigation of interactions taking place in the human body of amputees wearing prostheses during various falling scenarios as it is done in [1].…”