Impact of capsular preservation on patient-reported outcomes and complication rates in total hip arthroplasty using the direct anterior approach

Aims It is not known whether preservation of the capsule of the hip positively affects patient-reported outcome measures (PRoMs) in total hip arthroplasty using the direct anterior ap-proach (DAA- THA). A recent randomized controlled trial found no clinically significant differ- ence at one year postoperatively. This study aimed to determine whether preservation of the anterolateral capsule and anatomical closure improve the outcome and revision rate, when compared with resection of the anterolateral capsule, at two years postoperatively. Methods Two consecutive groups of patients whose operations were performed by the senior au-thor were compared. The anterolateral capsule was resected in the first group of 430 pa- tients between January 2012 and December 2014, and preserved and anatomically closed in the second group of 450 patients between July 2015 and December 2017. There were no other technical changes between the two groups. Patient characteristics, the charl-son comorbidity Index (ccI), and surgical data were collected from our database. PRoM questionnaires, consisting of the oxford Hip Score (oHS) and core outcome Measures Index (coMI- Hip), were collected two years postoperatively. Data were analyzed with generalized multiple regression analysis. Results The characteristics, ccI, operating time, and length of stay were similar in both groups. There was significantly less blood loss in the capsular preservation group (p = 0.037). The revision rate (n = 3, (0.6%) in the resected group, and 1 (0.2%) in the preserved group) did not differ significantly (p = 0.295). Once adjusted for demographic and surgical factors, the preserved group had significantly worse PROMs: + 0.24 COMI -Hip (p < 0.001) and-1.6 OHS points (p = 0.017). However, the effect sizes were much smaller than the minimal clinically important differences (MCIDs) of 0.95 and 5, respectively). The date of surgery (influencing, for instance, the surgeon's age) was not a significant factor. conclusion Based on the McID, the lower PRoMs in the capsular preservation group do not seem to have clinical relevance. They do not, however, confirm the expected benefit of capsular preservation reported for the posterolateral approach.

Automated summary

This study compared the outcome and revision rate of total hip arthroplasty with preservation or resection of the anterolateral capsule. The results showed that there was no significant difference in revision rate between the two groups, but the preserved group had worse patient-reported outcome measures. However, these differences were smaller than the clinically important thresholds.