Background
Global femoral offset (GFO), a sum of acetabular offset (AO), and femoral offset (FO) have been reported to influence outcomes after total hip arthroplasty (THA). There are several reports on the optimal offset using plain radiographs; however, internal and ex-ternal rotations of the hip affect the offset value, and it produces unclear results when the non-surgical side is not intact. We aimed to investigate the relationship between functional hip score evaluated using the Harris hip score (HHS) and its effect on the AO, FO, GFO, anterior fem-oral offset (AFO), anterior pelvic offset (APO), and global pelvic offset (GPO) after THA, and iden-tify the optimal offset value. Materials and Methods: This study was done cross-sectionally and ret-rospectively in a single center. A total of 140 patients with hemilateral osteoarthritis of the hip (HOA) who underwent THA were included in the analysis, and parameters were examined using three-dimensional pelvic and femoral models generated from computed tomography. Results: There was a significant binomial correlation among modified HHS, FO, and GFO, with maximum values of 21.3 mm and 40 mm/100 cm body height, respectively. Conclusions: The pelvic and femo-ral parameters were measured and evaluated through alignment with a specific coordinate system. Based on our findings, preoperative planning using the parameters is expected to improve post-operative hip function, even when the nonoperative side is not suitable as a reference, as in bilateral HOA cases.