An Efficiency Curve, Not a Safety Curve: Outcomes of Fellowship-Trained Surgeons in Their First 100 Direct Anterior THAs

Technical Summary: Efficiency vs. Safety in Fellowship-Trained DAA Surgeons

Problem Statement
The direct anterior approach (DAA) for total hip arthroplasty (THA) has historically been associated with a steep learning curve, particularly for surgeons converting to the technique mid-career without formal training. Early adoption phases have been characterized by elevated rates of specific complications, including intraoperative femoral fractures, lateral femoral cutaneous nerve (LFCN) neurapraxia, component malpositioning, and superficial wound issues. These risks typically cluster within the first 50–100 independent cases. While emerging literature suggests that dedicated fellowship training might mitigate these risks, no study has directly compared the outcomes of newly graduated, fellowship-trained surgeons performing their first independent cases against established, high-volume senior DAA surgeons. The central question is whether the historical "safety" learning curve persists for surgeons who receive specific DAA exposure during their training.

Methodology
This retrospective cohort study analyzed 600 primary, elective DAA THAs performed at a single academic institution between November 2019 and February 2025. The study design compared two distinct cohorts:

• Junior Cohort (n=300): The first 100 consecutive primary DAA cases performed by each of three junior fellowship-trained arthroplasty surgeons. All three surgeons completed North American arthroplasty fellowships with a specific emphasis on DAA, logging over 100 DAA cases during their training.
• Senior Cohort (n=300): The most recent 300 consecutive DAA cases performed by a single senior fellowship-trained surgeon with over ten years of practice experience in the approach.

All surgeons utilized intraoperative fluoroscopy for component positioning. Crucially, all junior surgeons operated within the institution's established Enhanced Recovery After Surgery (ERAS) protocols from the outset of their independent practice, ensuring standardized perioperative pathways (multimodal analgesia, anticoagulation, early mobilization) identical to the senior surgeon.

Key Outcomes and Results
The study evaluated intra-operative and post-operative complications within 90 days, operative time, and patient-reported outcome measures (PROMs).

• Complication Rates: There was no statistically significant difference in the overall incidence of operative complications between the junior and senior cohorts (10.0% vs. 7.7%, p=0.39). Subgroup analyses revealed no significant differences in specific adverse events, including:
  • Dislocation (1.3% vs. 0.3%, p=0.37)
  • Periprosthetic fracture (1.7% vs. 1.0%, p=0.73)
  • Neuropraxia (1.3% vs. 2.0%, p=0.75)
  • Prosthetic joint infection (1.0% vs. 0.3%, p=0.62)
  • Wound complications (2.3% vs. 2.3%, p=1.00)
  • Medical events (DVT, PE, transfusion, etc.) were also comparable, with a non-significant trend toward slightly more medical events in the senior cohort.
• Operative Time: A significant difference was observed in efficiency. The junior cohort had a mean operative time of 92.3 minutes compared to 68.5 minutes for the senior surgeon (p<0.001). Sequential quartile analysis of the junior surgeons demonstrated a clear efficiency learning curve, with mean operative times decreasing from 108.3 minutes in the first 25 cases (Q1) to 84.6 minutes in the final 25 cases (Q4). In contrast, the senior surgeon's operative time remained stable across all time blocks.
• Patient-Reported Outcomes (PROMs): At baseline, patients treated by junior surgeons had significantly worse preoperative SF-12 physical scores and WOMAC scores (pain, stiffness, function) compared to the senior cohort. However, by 90 days, PROMs were statistically indistinguishable between groups. Notably, in the subset of patients with paired data, the junior cohort demonstrated significantly greater absolute improvement in SF-12 physical scores, WOMAC pain, and WOMAC function compared to the senior cohort.

Significance and Claims
The paper concludes that the historical "safety" learning curve associated with the DAA may not apply to surgeons who undergo dedicated fellowship training in the approach. The study posits that while an efficiency curve exists (evidenced by longer operative times for junior surgeons), a safety curve does not.

The authors claim that the combination of specific DAA-focused fellowship training and standardized institutional ERAS pathways effectively eliminates the disparity in complication rates between junior and senior surgeons. The findings suggest that for fellowship-trained surgeons, the transition to independent practice does not incur a functional penalty or increased risk of adverse events, even when operating on patients with worse baseline functional status. The study asserts that in modern training environments, the primary differentiator between junior and senior DAA surgeons is operative efficiency rather than patient safety or short-term functional outcomes.

Limitations Noted by Authors
The authors acknowledge several limitations, including the single-institution nature of the study, the relatively low mean BMI of the cohort compared to national averages, and the 90-day follow-up window which may miss late-onset complications. Additionally, the PROM analysis is considered exploratory due to follow-up rates below 50% in both cohorts, and the study was powered to detect a 5% difference in complications, meaning smaller differences in rare adverse events could not be ruled out.