RESUMEN
BACKGROUND: Acetabular fractures are rare injuries, but there is an increasing number of elderly people with ventral medial instability in cases of central subluxation of the femoral head in osteoporotic acetabular fractures. Common plate osteosynthesis cannot enable medial support of the quadrilateral surface. The new "acetabular wing plate" is anatomically shaped to fix the arcuate line and the quadrilateral surface. The plate pushes the femoral head back to lateral. The aim of this study was the biomechanical comparison with common plate concepts before clinical use of the new implant. METHODS: For biomechanical testing eight artificial fracture models of the pelvis with anterior column fractures were used. They were implemented into a set-up of a one-leg stand model in the material test machine. Cyclical movements with axial pressure to the sacrum up to 250 N were given to the model. Fracture gap movement was measured with an optoelectronic 3D camera measuring system. In all pelvic models all screw holes were drilled by use of drill guides before first mechanical loading. The measurements were randomly done first with the new acetabular wing plate or with the pelvic low profile plate. Absolute and relative fracture gap movement and movements of the pelvic fragments were measured as well. RESULTS: The fracture gap movement and the fragment rotation were comparable in both groups. There was a slightly higher stability in the group of the acetabular wing plate but without statistical significance. In the pelvic low profile group two screw loosenings were found, but the models were able to be tested also with the acetabular wing plate. The new plate was clinically used in the first eight patients due to the good biomechanical results. In all cases the osteosyntheses were done by use of the Stoppa approach and the first window of the ilioinguinal approach. Application of the plate was mostly easy, the plate was also used as a reduction tool. Postoperative controls show anatomic reduction and correct implant position in all eight cases. The three month follow-up examinations confirm the continuing good reduction during fracture healing with the acetabular wing plate.