Achieving the required medial offset and limb length in total hip arthroplasty

The magnitude of the medial offset and limb length discrepancy after a total hip arthroplasty (THA) significantly affects the biomechanics of the hip. If both of these components are not properly restored, the rate of dislocation may increase. In addition limb length inequality can be a cause for legal problems. We have used a method of intraoperative assessment to restore both the length and the medial offset, and assessed this by comparing the medial offset and leg length in the pre- and post-operative radiographs in 39 consecutive THAs. The median medial offset was 93.9% (range: 85 to 100) preoperatively and 94.2% (range: 85 to 110) postoperatively, compared with the unaffected contralateral side. The median limb length discrepancy was improved from a preoperative -4.84 mm (range: 0 to -30) to a postoperative -0.06 mm (range: -9 to +16). In conclusion, this technique is a simple, accurate and reliable way of restoring the medial femoral offset and correcting the limb length inequality.