Where is acetabular reaming concentrated during total hip arthroplasty for hip osteoarthritis? A computed tomography-based simulation analysis

PURPOSE: The purpose of this study was to quantify the three-dimensional distribution of estimated acetabular bone requiring reaming during virtual cup placement in total hip arthroplasty (THA) for hip osteoarthritis (OA), providing a quantitative reference for direction-specific reaming patterns. METHODS: In this CT-based simulation analysis, preoperative CT data from 118 female hips that underwent primary THA for primary OA or mild developmental dysplasia of the hip (DDH) between 2021 and 2024 were used to simulate cup placement at the true acetabulum. The pelvis was oriented to the functional pelvic plane, and the cup was positioned at 20° anteversion and 40° inclination. The simulated reamed area was quantified at 12 clock-face positions. Simulated reamed areas were compared by diagnosis using Holm-adjusted Student's t tests and among positions using repeated-measures ANOVA with Holm adjustment. RESULTS: ) (p < 0.001). Post hoc comparisons showed larger reamed areas at 8 and 9 o'clock and smaller areas from 0 to 2 o'clock than at most other positions (p < 0.05). This posteriorly concentrated pattern was particularly evident in mild DDH, with smaller reamed areas from 0 to 2 o'clock and larger areas at 8 and 9 o'clock than at other positions. CONCLUSION: In this CT-based simulation study, simulated acetabular reaming was minimal in the anterosuperior region and greater posteriorly. These findings may provide anatomical information for understanding direction-specific reaming patterns, particularly in mild DDH.