Effects of lower limb and pelvic pin positions on leg length and offset measurement errors in experimental total hip arthroplasty

Abstract Background Leg length (LL) and offset (OS) are important factors in total hip arthroplasty (THA). Because most LL OS callipers used THA depend on fixed points the pelvis femur, limb position could affect measurement error. This study was conducted a simulator to clarify effects of lower iliac pin errors determine permissible range for accurate measurement. Methods An instrument used. Two positions were tested: tubercle top crest intersecting with extension femoral axis. First, moved one direction (flexion-extension, abduction-adduction, or internal-external rotation), measured each position. Next, combinations three directions. Then, combined position, which resulted error within ±2 mm, determined Results Only 4° abduction/adduction caused 5–7 mm 2–4 OS, irrespective The flexion–extension internal–external rotation smaller than tubercle, though similar both positions. For LL, wider tubercle. Conclusion To minimize THA, adduction–abduction must be maintained. is preferred because it provides less