Proximal Bone Remodeling in Lower Limb Amputees Reconstructed With an Osseointegrated Prosthesis

Mobility outcomes and changes in bone mineral density (BMD) of the spine and femoral necks in response to unilateral osseointegrated implants was investigated over a 3-year period. A total of 48 unilateral amputees who received an osseointegrated implant, comprising 33 trans-femoral amputees (TFA) and 15 trans-tibial amputees (TTA), underwent dual-energy X-ray absorptiometry (DXA) scans of the lumbar spine (L2-L4) and femoral necks at baseline, 1-, and 3-years follow-ups. Mobility outcomes, including the Six-Minute-Walk Test (6MWT) and Timed-Up-and-Go (TUG), were measured before surgery, at 1 year, and more than 2 years following the osseointegration procedure. We observed a significant increase (p < 0.05) in Z-score values in the femoral neck of the amputated side in TFA patients without a femoral neck lag screw at the 1- and 3-year follow-ups, as well as in TFA patients with a lag screw present at 3-year follow-up. The BMD at 1-year follow-up was found to be positively correlated with pre-surgery 6MWT values in patients who were mobile using a traditional socket prosthesis before receiving an osseointegrated implant. These results suggest that osseointegrated implants induce a physiological response in the femoral neck of recipients and appear to be evidence of restored biomechanical loading in the proximal femur. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:2524-2530, 2019.