Comparison of limb-length discrepancy after THA: with and without computer navigation.

Limb-length discrepancy following total hip arthroplasty (THA) is often cited as a reason for patient dissatisfaction and for hip instability. Various intraoperative techniques have been described to help restore normal limb length after THA. The purpose of this study was to assess whether a computer-navigated surgical technique would help restore limb-length equality following THA.A retrospective study of 150 consecutive patients compared a free-hand (non-navigated) THA technique vs a computer-navigated THA technique. Each group contained 75 patients. The primary outcome measurement was limb-length discrepancy, which was evaluated using a digital anteroposterior pelvic radiograph. Secondary outcome measurements included a Harris Hip Score questionnaire and a single question evaluating the subjective feeling of the operative limb (longer, shorter, or equal). At a minimum 1-year follow-up, results showed that computer-navigated THA helped restore limb-length equality. An average leg-length difference of 0.3 mm (SD=0.3 mm) was found with computer-navigated THA compared with a leg-length difference of 1.8 mm (SD=0.7 mm) when a non-navigated THA was used. This was statistically significant. Both groups had similar Harris Hip Scores (computer-navigated group, 84.8; non-navigated group, 84.2; P=.835), and no difference was found between the 2 groups regarding the patient's perception of the operative limb length.This study demonstrated that computer-navigated THA resulted in improved restoration of normal limb length and limited significant outliers but did not show improvement in Harris Hip Scores or patient's perception of limb-length equality.