[Effects of femoral offset on soft tissue balance in total hip arthroplasty]

To analysis the effects of restoring neck length and femoral calcar of femoral component on the reconstruction of femoral offset and its affection on soft tissue balance in total hip arthroplasty with standard femoral components.

Sixty-eight patients (71 hips, 30 male and 38 female,ranging in age from 17 to 89 years,with an average of 63.5 years)undergone primary total hip arthroplasty were followed up. The postoperative hip scored according to Harris hip score symtem, and femoral offset,femoral calcar restored as well as neck length of femoral component were measured from the postoperative X-ray image, and the adductor muscle force was measured by Cybex-6000 isokinetic muscle strength testing system.

Femoral neck length had highly significant and positive correlation with femoral offset (r = 0.64, P < 0.001), and had more effects on femoral offset than restoring femoral calcar (t = 3.07, P < 0.01), but had no significant difference on postoperative Harris score. The postoperative femoral offset of patients operated for the femoral head osteonecrosis was less than those for the hip osteoarthrosis (t = 2.91, P < 0.01) and the femoral neck fracture (t = 3.31, P < 0.01). The adductor muscle force in patients who restored femoral offset were better than those failed to restore femoral offset.

There are several factors affecting femoral offset restoration for soft tissue balance in total hip arthroplasty with standard femoral components, among them, the key factor is the neck length of femoral component which is more significant than femoral calar restoration for reconstruction of femoral offset. The role of femoral offset on soft tissue balance in total hip arthroplasty was strengthening the postoperative adductor muscle.