Can robot-assisted total hip arthroplasty improve the incidence of self-reported leg length discrepancy? A Multicenter, Propensity Score Matching Comparative Study.

Background: Patients often report leg-length discrepancy (LLD) after total hip arthroplasty (THA). The factors behind self-reported LLD (sLLD) are unclear. Robot-assisted THA (RA-THA) offers improved precision, but its effect on sLLD has not been well studied. This study aimed to assess RA-THA's benefits in reducing sLLD and identify impacting factors.

Materials And Methods: Patients who underwent RA-THA or conventional THA (CON-THA) at three Chinese hospitals were reviewed. Propensity score matching (PSM) was used to match the RA-THA and CON-THA groups by preoperative data. Initially, 215 patients were enrolled; nine were excluded. The RA-THA group had 102 patients, and the CON-THA group had 104. After PSM, 74 patients remained in each group. Postoperative outcomes, including imaging data, clinical scores, and sLLD, were compared. Patients were categorized by whether the measured LLD (mLLD) post-surgery was less than 10mm. Disparities in data and surgical methods were compared. Univariate and multivariate logistic regression analyses identified sLLD predictors.

Results: The RA-THA group showed better postoperative mLLD, cup anteversion, inclination, and offset discrepancy, but no significant differences in sLLD at three years. The RA-THA percentage was higher in the mild LLD group (59.4%) and lower in the severe LLD group (32.7%). Patients who had mild LLD had a lower proportion of sLLD at three years. Logistic regression identified preoperative mLLD, preoperative Harris Hip Score (HHS), postoperative mLLD, and postoperative HHS as significant predictors of sLLD.

Conclusion: The RA-THA may not significantly reduce sLLD. Key predictors of sLLD included preoperative mLLD, preoperative HHS, postoperative mLLD, and postoperative HHS, highlighting the need for thorough preoperative assessment and patient education for better outcomes and satisfaction.