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.