Until today it is unknown whether preservation of the joint capsule positively affects patient reported outcome (PROs) in DAA-THA. A recent RCT found no clinical difference at 1 year. Since 2015 we preserve the capsule suture it at the end. We here evaluate whether this change had any effect on PROs and revisions, 2 years post-operatively.

Two subsequent cohorts operated by the senior author were compared. The capsule was resected in the first cohort (January 2012 – December 2014) and preserved in the second cohort (July 2015 – December 2017). No other technical changes have been introduced between the two cohorts. Patient demographics, Charlson Comorbidity Index (CCI), and surgical data were collected from our clinical information system. 2-years PROs questionnaires (OHS, COMI Hip) were obtained. Data was analyzed with generalized multiple regression analysis.

430 and 450 patients were included in the resected and preserved cohorts, respectively. Demographics, CCI surgical time and length of stay were equal in both groups. Blood loss was less in the preserved cohort (p<.05). Four patients had a revision (1 vs 3, n.s.). Once corrected for demographics, capsule preservation had significant worse PROs: +0.24 COMI (p<.001) and −1.6 OHS points (p<.05), however, effects were much smaller than the minimal clinically important difference (0.95 and 5 respectively). The date of surgery (i.e. surgeon's age) was not a significant factor.

In this large retrospective study, we observed statistically significant, but probably clinically not relevant, worse PROs with capsule preservation. It might be speculated that the not resected hypertrophied capsule could have caused this difference.