Is There a Learning Curve for the 5-Year Implant Survival Rate of Total Hip Arthroplasty Using the Direct Anterior Approach with a Traction Table? - A Prospective Cohort Study

Abstract

The direct anterior approach (DAA) for total hip arthroplasty (THA) is attracting attention as a minimally invasive surgery, but the learning curve to master this approach is a concern, and its effect on long-term results is unknown. The purpose of this prospective cohort study was to clarify how the learning curve affects the five-year results of DAA THA with a traction table. Of 402 THA cases using DAA with a mobile traction table and fluoroscopy, 249 cases composed of the first 50 cases for each surgeon were assessed during a learning curve, and 153 cases were evaluated after more than 50 cases of experience. The five-year-implant survival rate was 99.2% both during and after the learning curve. The two-year complication rate in the learning curve group was 8.9 versus 5.9%, which was not statistically significant. The two-to-five-year complication rates also did not differ between cohorts (0 versus 0.7%). Both groups demonstrated decreased complication rates when comparing two-year complications to the two-to-five-year complications. Clinical scores significantly improved by two years and were maintained at five years in both groups. The cup-safe zone success rates were 96.4% during the learning curve and 98.7% after the learning curve. The stem-safe zone success rates were 97.2% during the learning curve and 96.1% after the learning curve. Surgical time was approximately 20 minutes shorter after the first 50 cases than during the learning curve (70.8 versus 90.6 minutes, P = 0.001). Intraoperative blood loss was significantly less after the learning curve than during the learning curve. This study implicates that the learning curve affects perioperative results such as surgical time and intraoperative blood loss, but has little effect on short-term results up to two years after surgery and no effect on mid-term results from two to five years after surgery.