Preserving medial iliofemoral ligament avoids excessive leg lengthening in total hip arthroplasty using anterolateral-supine approach.

Background: In this study, we compared postoperative leg length discrepancy (LLD) after total hip arthroplasty using the anterolateral-supine approach (ALSA THA) with or without medial iliofemoral ligament (mILFL) preservation and examined the effect of the remaining mILFL on postoperative LLD. Methods: This was a single-center, retrospective case control study. Unilateral primary THA with a preoperative LLD <15 mm, in which the contralateral side was intact, was included. After ALSA THA, we compared the absolute values of postoperative LLDs and examined the ratio of postoperative LLD >5 mm with and without mILFL preservation. Demographic data, clinical scores, and operative data were collected. Statistical significance was set at p < 0.05. Results: We included 341 hips (preservation group: 283 hips; resection group: 58 hips). The mean (range) absolute values of the postoperative LLDs were 2.3 (0-15.9) mm and 3.4 (0-14.8) mm, respectively. There was no significant difference between the two groups (p = 0.36). The proportion of postoperative LLD >5 mm differed significantly between the groups (4.4 % and 20.0 %, respectively; p < 0.01). Multiple logistic regression analysis showed that resection of the mILFL was the only significant factor that caused excessive leg lengthening (odds ratio, 5.28; 95 % confidence interval, 2.12-13.10, p < 0.01). Significant differences were reported in surgical time (81 (38-132) and 96 (54-157), respectively; p < 0.01) and intraoperative blood loss (297 (50-1170) and 388 (100-1150), respectively; p < 0.01). However, no significant differences in clinical scores, dislocation (including instability), or reoperation rates were observed between the two groups. Conclusion: In patients with a preoperative LLD <15 mm, preserving the mILFL in ALSA THA avoids excessive leg lengthening and may lead to shorter LLD without any difficulties.