Anthropometric Measurement About the Safe Zone for Transacetabular Screw Placement in Total Hip Arthroplasty in Asian Middle-Aged Women: In Vivo Three-Dimensional Model Analysis

Although the pelvic vascular injury caused by a transacetabular screw is rare, it is a major local complication of total hip arthroplasty. We aimed to obtain anthropometric data about the safe zone for the placement of transacetabular screws by analyzing the three-dimensional (3D) reconstruction model and determine the safe length of transacetabular screws by performing the 3D simulated surgery.

We reviewed 50 hips of 25 patients who underwent lower extremity angiographic computed tomography scans retrospectively. We reconstructed the 3D models of 50 hips with normal pelvic bone and vascular status using the customized computer software. We measured the central angle and safe depth of the safe zone of the transacetabular screws on the 3D models. We also performed the 3D simulated surgery to confirm the safe length of screws in each hole of the customized cup implant.

The measured central angle of the posterior-superior area was 79.5°. And we determined a mean safe depth of 49.8 mm in the safe zone, with a central angle of 47.7°. During the 3D simulated surgery, we determined a mean safe length of the transacetabular screw of 43.3 mm when applied to a lateral hole on a line bisecting the posterior-superior area.

Although our study was limited by the use of a virtual computer program, the quantitative measurements obtained can help reduce the incidence of pelvic vascular injury during transacetabular screw fixation in total hip arthroplasty.