The aim of this study was to assess changes in hip abductor muscle volume, composition, and strength 6- and 12-months after osseointegration implant surgery compared to the pre-operative situation using a SSP.
All consecutive patients who were scheduled for a unilateral transfemoral osseointegration surgery in the Radboudumc (Nijmegen, the Netherlands) between February 2020 and May 2021 were eligible for inclusion.
Muscle volume and composition of the hip abductor muscles was obtained using T1-weighted MRI and DIXON sequence. The muscles were segmented using 3D Slicer software to obtain a 3D reconstruction. Hip abductor strength was measured with a portable handheld dynamometer.
In total, 11 participants were included, with a median age of 63 (54; 67) years and 7 (3; 18) years after primary amputation. For muscle volume and composition we only report the outcomes of first 6 participants. The remaining data is currently being analysed.
Hip abductor muscle volume and composition
In the residual limb, the individual muscle volume increased at both follow-ups compared to baseline, but did not reach significance in the m. tensor fasciae latae at the 6-month follow-up and in the m. gluteus medius and m. piriformis at the 12-month follow-up. The total hip abductor volume increased significantly at 6-month (1238±191cm3) and 12-month follow-up (1275±199cm3) compared to baseline (1155±179cm3).
In the sound limb, the individual muscle volume did not change significantly, except the m. gluteus medius which increased at the 6-month follow-up compared to baseline. The total hip abductor volume did not change significantly at 6-month (1549±151cm3) or 12-month (1565±148cm3) follow-up compared to baseline (1527±175cm3).
In the residual limb, the total fat fraction decreased at both follow-ups compared to baseline, but this difference did not reach significance. In the sound limb, the total fat fraction did not change significantly at both follow-ups compared to baseline.
Hip abductor strength
Both the residual and sound limb hip abductor strength increased at 6-month (residual; 0.88±0.04Nm/kg, sound; 1.05±0.07Nm/kg) and 12-month (residual; 1.04±0.08 Nm/kg, sound; 1.26±0.11Nm/kg) follow-up compared to baseline (residual; 0.87±0.05 Nm/kg, sound; 1.01±0.05Nm/kg), but only the increase at 12-month follow-up was statistically significant.
Even years after the primary amputation, BAP use significantly increased hip abductor muscle volume and strength in the residual limb within 12-months, but these were not normalized compared to sound limb. The hip abductor muscle tissue composition did not follow the positive trend of hip abductor muscle volume and strength regeneration.
Degeneration at tissue level is severe after a leg amputation. This study provides insight into the possibility for regeneration, influence of type of prosthesis, and the need for tailored rehabilitation after a leg amputation.
Muscle
Prosthesis
