The Impact of Unilateral Transfemoral Amputation on Lumbar Bone and Muscle Quality

Objective To examine the long-term perioperative changes in lumbar bone density, muscle size and fatty atrophy, and facet degeneration after transfemoral amputation (TFA). Design All patients who underwent TFA at an academic center between 2002-2022 were retrospectively identified. Patients were required to have preoperative and postoperative CT (>1 year) and regularly utilize a prosthesis. Preoperative to postoperative changes in lumbar and muscular vertebral Hounsfield units (HU), facet degeneration, and bilateral psoas, quadratus lumborum, multifidus, and erector spinae cross-sectional area (CSA) were determined. Results A total of 42 patients met the inclusion criteria. There were significant preoperative to postoperative decreases in HUs in the L1 and L3 vertebral bodies were -17.69 and -25.35, respectively. There were significant pre- to post-operative increases in L4-5 and L5-S1 facet degeneration grade. There were significant pre- to post-operative decreases in amputated side psoas HU and CSA. There were also significant pre- to post-operative HU decreases in the bilateral multifidus and erector spinae muscles, where the changes were more pronounced on the contralateral side. Conclusion TFA was associated with progression of lumbar facet degeneration, small scale decreases in lumbar bone quality, amputated side psoas atrophy, and bilateral fatty infiltration of the multifidus and erector spinae.