Analysis of the infra-acetabular corridor: sex-specific differences in the secure area and insertion angle in infra-acetabular screw placement.

Abstract

A majority of older adult acetabular fracture patients have a fracture of the anterior component, and repair of the acetabular anterior component with infra-acetabular screw (IAS) fixation is crucial. The aim of this study was to clarify the sex-specific differences in the secure infra-acetabular corridor for safe IAS placement. Three-dimensional pelvic computed tomography (CT) images of 50 males and 50 females with an average age of 77.5 years were analyzed. The secure insertion path of IAS was simulated on the ZedHip system (Lexi Co., Ltd., Japan), and length, angle, and diameters of the infra-acetabular corridor were measured. The lengths of the corridors were 99.0±4.6mm in males and 91.5±5.3mm in females (p<0.01). The angle of the corridor to Y axis in the axial plane on the functional pelvic plane (FPP) was 5.1±4.9° in males and 8.6±5.3° in females (p<0.01). However, in 32% of the cases it was deemed that a IAS could not be inserted because the diameters of the corridor were too narrow to insert the screw. On simulation, the corridor length was shorter and corridor angle was larger in females. In one third of cases the infra-acetabular corridor simulation showed it was impossible to insert the IAS, so it is crucial to scrutinize the infra-acetabular corridor on CT images during preoperative planning for IAS insertion in acetabular fractures.