Medial Femoral Offset and Early Pelvic Obliquity Correction After Unilateral Total Hip Arthroplasty

Pelvic obliquity (PO) may alter perceived acetabular orientation and increase the risk of component malpositioning after total hip arthroplasty (THA). Femoral offset reconstruction influences pelvic mechanics during gait; however, the effect of intraoperative offset adjustment on postoperative PO remains unclear.

This cross-sectional study analyzed data from a prospective arthroplasty registry including adult patients who underwent unilateral cementless THA between 2018 and 2023 and had preoperative PO. Forty-six patients (mean age 66.8 ± 8.2 years) were included. Medial offset (MO), vertical offset, PO angle, and spinopelvic parameters were measured on standardized radiographs obtained preoperatively and at 6 months postoperatively. Patients were categorized based on postoperative improvement in PO. Functional outcomes were assessed using the Harris Hip Score and Western Ontario and McMaster Universities Osteoarthritis Index. Statistical analyses included correlation testing, chi-square analysis, and logistic regression.

Mean PO significantly improved from 3.4° preoperatively to 1.6° postoperatively (P = .027). Medial offset increased significantly, whereas vertical offset showed no significant change. In patients with obliquity toward the operative side, decreasing MO was associated with correction of PO (P = .037). Conversely, in patients with contralateral obliquity, increasing MO resulted in significant improvement (P = .028). Logistic regression confirmed greater improvement when MO was increased in patients with contralateral PO (P = .038). Improved PO was associated with significantly better functional outcomes (P < .001).

Medial offset adjustment based on the direction of preoperative PO contributes to restoration of coronal pelvic balance and improved function after THA.