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

Abstract

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.

Femoral Neck Hounsfield Units as an Adjunct for Bone Mineral Density After Combat-Related Lower Extremity Amputation

“…3,30,31 As bone remodels secondary to the magnitude of forces placed on it, these losses in amputees are believed to be secondary to prosthetic wear with socket suspension that may bypass skeletal loading, decreases in muscle strength, and decreased use of the limb for weightbearing and standing activities. [30][31][32] Prolonged immobilization and nonweightbearing further exacerbate this loss. After amputation, early limited weightbearing may occur as soon as 4-6 weeks but is frequently and substantially delayed by completion of flap reconstruction, union of concurrent fractures, healing of the softtissue envelope, resolution of edema, and prosthetic fitting.…”

Hounsfield Unit-Calculated Bone Mineral Density Loss Following Combat-Related Lower Extremity Amputations

“…extremity amputation, BMD loss is exacerbated by offloading of the osseous kinetic chain with prosthesis wear, delayed weightbearing due to healing or complications, or bone resorption resulting from complex regional pain syndrome [9][10][11][12][13] .…”

Osseointegration

“…Intramedullary anchorage allows for improved mobility and coordination, gait which more closely approximates a native limb and requires less energy expenditure, better proprioception, and obviation of the problems associated with the traditional socket and residuum. 2,3…”

“…There are a number of bone-anchored implants available, which typically achieve primary stability through press-fit and secondary stability through endosteal in-growth. Intramedullary anchorage allows for improved mobility and coordination, gait which more closely approximates a native limb and requires less energy expenditure, better proprioception, and obviation of the problems associated with the traditional socket and residuum 2,3…”