Mechanical Evaluation of Posterior Wall Acetabular Facture Fixation: Patient-Specific Implants Versus Conventional Implants.

Abstract

The aim of the study was to design a standardized mechanical test setup and a corresponding finite element analysis to assess the stability and strength of both patient-specific and conventional implants for posterior wall acetabular fractures. Ten synthetic hemi-pelves with posterior wall fractures were biomechanically tested with two types of implants: a patient-specific implant (PSI) and a seven-hole plate conventional implant. 3D-printed guides ensured reproducibility. The models were tested using an Instron machine. The protocol involved 10,000 cyclic load cycles with static tests at 3200 N before and after to simulate early postoperative weightbearing conditions. Construct stiffness, stiffness over cyclic loading and fracture gapping were measured and compared. A finite element analysis was created with similar conditions to investigate stresses within the synthetic bone and fixation materials. The mechanical tests showed comparable stiffness for PSI (1.75 kN/mm) and the conventional implant (1.71 kN/mm, p = 0.47). Stability over 10,000 cycles was similar, and fracture gapping remained minimal (0.0-0.8 mm) without significant differences. No failure or plastic deformation occurred under 3200 N loading. Finite element analysis confirmed that von Mises stresses remained below the yield stress. This study introduces a reproducible workflow for biomechanical testing of acetabular fractures using synthetic bone models and 3D-printed guides. It serves as a step-by-step guideline and standard reference for pelvic biomechanical testing. Both patient-specific and conventional implants, using a seven-hole plate construct with one or two screws through the plate in the fracture fragment, provide stable fixation for large posterior wall fragments.