Analysis of the causes of lower limb inequality after hip arthroplasty and prevention To investigate the causes of bilateral lower limb inequality after artificial hip replacement surgery and the corresponding preventive and curative measures. Methods: From 2005.1 to 2008.2, 126 patients with unilateral hip disease were treated with total hip replacement. The preoperative osteotomy plane of the femoral neck and the retained length of the femoral spine were determined by repeated measurements from the bilateral anterior superior iliac spine to the superior edge of the patella, standard x-ray orthopantomographs of the pelvis and the use of the femoral head template. RESULTS: After surgery, 102 cases (80.9%) had bilateral lower extremity isometric or length differences of 5 mm or less. the Harris score improved from a mean of 50 before surgery to 91.2. CONCLUSION: The postoperative unequal length of both lower limbs can be effectively prevented by preoperative measurement and assessment on orthogonal pelvic radiographs and intraoperative consideration of bone, soft tissue, prosthesis and other related factors.