Hip muscle geometry and function following a transfemoral amputation - a cross-sectional study protocol

Abstract

Background: Individuals with a transfemoral amputation often experience limited walking abilities and difficulties with balance. These difficulties may arise not only from the loss of a limb but also from changes in the muscles in the residual limb post-amputation, such as muscle atrophy, increased intermuscular fat, and alterations in muscle architecture. This can result in loss of muscle function. Individuals with a transfemoral amputation indeed show decreased muscle strength in the residual limb compared to the intact limb. Although research has shown that muscle strength deficits in individuals with a transfemoral amputation are associated with difficulties in daily functioning, residual limb control, and walking performance, the specific role of residual muscle adaptations in contributing to these strength deficits and functional challenges remains unclear. Therefore, this paper presents a cross-sectional study protocol to investigate hip muscle geometry and function following transfemoral amputation, with the goal of understanding muscle adaptations and their functional consequences. Additionally, the influence of various amputation related factors, including the surgical technique, will be investigated.

Methods: Individuals aged 18 years or older who have undergone a unilateral transfemoral amputation within the past 1-5 years and are actively using a prosthesis (K-level ≥ 2) will be recruited. Participant characteristics such as age, sex, weight, height, cause, and date of amputation will be collected via a questionnaire. Study measurements will include a 1,5T Magnetic Resource Imaging scan to gather data on muscle geometry and femur length for both the residual and intact limbs, and a dynamometer strength test (isokinetic and isometric) to assess the hip muscle strength for each muscle group. The L Test of Functional Mobility will be performed to evaluate physical function. If possible, participants will be grouped based on the surgical technique used (myodesis vs. myoplasty) to allow group comparisons. Within-subjects differences will be assessed as the differences between the intact and residual limb, and Pearson’s correlation coefficients will be used to examine the relationships between muscle geometry and hip muscle strength. Ethical approval has been obtained by the Medical Ethical committee of the University Medical Center Groningen (METc 2024/392).