A Consistent Intra-Articular Landmark for Safer Transacetabular Screw Placement: A Topographic Cadaveric Study

Abstract Background Transacetabular screw fixation enhances initial stability in cementless total hip arthroplasty but risks injury to adjacent neurovascular structures. The junction of the posterior articular surface of the lunate surface and the ischial ramus was identified as a consistent and reproducible intra-articular landmark, and this anatomical study was designed to evaluate its potential use as a reliable guide for screw orientation and to improve surgical safety. Methods In a two-part study design, including topographic dry-bone morphometry on 50 adult hemipelves and cadaveric dissection in 4 male donors. Acetabular bone thickness and the spatial relationships of simulated screw trajectories to intrapelvic neurovascular structures were mapped. The acetabulum was divided into 12 radial sectors from the landmark, with two levels analyzed along each radius (A: central; B: peripheral), resulting in 24 measurement points. Results Sectors 5B–7B were characterized by greater bone stock and wider neurovascular clearance, whereas points such as 1 A, 2 A, and 12B were identified as higher-risk regions, with bone thickness < 7 mm and neurovascular proximity ≤ 5 mm. The landmark was consistently visible and easily identifiable following acetabular reaming. Conclusion These findings support the use of this landmark as a side-independent and intraoperatively accessible reference that may improve anatomical orientation for screw placement, particularly in cases where external landmarks are obscured. Further clinical validation in live surgical settings is warranted to confirm its safety and utility.