Does the direct anterior learning curve persist after fellowship training? A single-center comparative cohort study

The direct anterior approach (DAA) for total hip arthroplasty (THA) has historically been associated with a learning curve affecting both operative efficiency and early complications. Whether contemporary adult-reconstruction fellowship training modifies that curve is not established. We compared 90-day complication rates and operative times between newly graduated fellowship-trained DAA surgeons and one experienced DAA surgeon at a single high-volume center.

This retrospective cohort study included 600 primary THAs performed via a DAA from a single institution between November 2019 and February 2025 with a minimum of 90-day follow-up. Intra- and post-operative complications were compared between the following two groups: the first 100 cases of each of three junior fellowship-trained arthroplasty surgeons ("Junior") and the most recent 300 cases of a senior fellowship-trained arthroplasty surgeon ("Senior"). The study was powered to detect a 5% absolute difference in overall complication rates. Patient-reported outcome measures (PROMs) were analyzed as exploratory secondary endpoints.

Operative complications were infrequent in both cohorts, with a numerically higher rate in the Junior group that did not reach statistical significance (Junior 27 [9.0%] vs Senior 20 [6.7%]; absolute difference + 2.3%, 95% CI - 2.0% to + 6.6%, p = 0.362). No subgroup comparison reached statistical significance: DVT (1.0 vs 0.7%, p = 1.000), PE (0.3 vs 0.3%, p = 1.000), hematoma (0.3 vs 1.0%, p = 0.624), dislocation (1.3 vs 0.3%, p = 0.373), periprosthetic fracture (1.7 vs 1.0%, p = 0.725), neurapraxia (1.3 vs 2.0%, p = 0.752), prosthetic joint infection (1.0 vs 0.3%, p = 0.624), or wound complications (3.3 vs 2.0%, p = 0.448). All subgroup analyses were exploratory and underpowered for individually rare events. Medical events were infrequent and similar between groups (Junior 13 [4.3%] vs Senior 17 [5.7%], p = 0.575). Combining operative and medical complications, 40 events (13.3%) occurred in the Junior cohort and 37 (12.3%) in the Senior cohort (p = 0.807). Operative time was significantly longer among Junior surgeons (92.3 vs 68.5 min, p < 0.001). In exploratory analyses limited by 90-day PROM follow-up of 35% (Junior) and 48% (Senior), 90-day SF-12 and WOMAC scores were similar among respondents; given the incomplete follow-up, these descriptive findings are best regarded as hypothesis-generating rather than conclusive about functional recovery.

Within a single high-volume center using standardized ERAS pathways, three fellowship-trained surgeons performing their first 100 DAA THAs had significantly longer operative times than one experienced DAA surgeon, with no evidence of a large difference in 90-day complication rates. Because the study was powered only to detect a 5% absolute difference, it cannot exclude smaller or rare-event differences and does not establish equivalence. These data generate the hypothesis that contemporary fellowship training combined with protocolized perioperative care shifts the early DAA learning curve toward efficiency rather than safety; confirmation requires an adequately powered, multicenter study.