Limb length inequality in patients after primary total hip arthroplasty : analysis of radiological assessment and influencing risk factors based on a district general hospital experience of 338 cases

Abstract

Background and objective Limb length inequality (LLI) is a frequent and recurring issue after total hip arthroplasty (THA). It is often a source of patient dissatisfaction and litigation. This study reviewed the incidence of LLI in a UK District General Hospital in light of published evidence and identified the preoperative and intraoperative risk factors for LLI. Methods This was a retrospective study involving 380 consecutive unilateral primary total hip replacements over a period of 12 months. Patient demographics, clinical, radiological, and operative details were collected from the National Joint Registry (NJR) database and hospital records. The limb length was measured radiologically [OrthoView WorkstationTM (Materialise UK, Southampton, UK)], pre- and postoperatively, by two authors. They assessed the vertical distance between the intra-acetabular teardrop line and the medial apex of the lesser trochanters. After excluding complex primary, revision cases, tilted X-rays, and hip replacement for trauma patients, 338 cases were included in the final analysis. Results The mean postoperative LLI was 2.7 mm with a standard deviation (SD) of 6.56 mm. Only 5.3% of patients had LLI >15 mm. None of the studied variables showed a statistically significant correlation with LLI. Even with the apparent difference in the mean LLI between templating and not templating before surgery (2.19 vs. 3.53), the p-value was 0.06, which was below the level of statistical significance. There was a weakly positive Pearson correlation between body mass index (BMI) and the incidence of lengthening of the limb. Conclusion The cause of LLI after THA is multifactorial. No single factor can be singled out as the most significant contributor to this complication.