Biomechanical analisis of secondary dislocation of posterior wall fragment after operative fixation of acetabular posterior wall fracture – case study

Abstract

Background: Fracture of the posterior wall is the most common pattern in acetabular fractures. The anatomical reduction and stable fixation of this articular fracture is a prerequisite for a favorable functional outcome but it is not enough in itself. In some patients, even physical therapy with initial passive motion and continued active exercises without weight bearing could lead to excessive loading on the injured cartilage and, in some cases, even to dislocation of fragments and early post-traumatic osteoarthritis. Our biomechanical studies demonstrated high loading of the acetabulum even during standard physical therapy.

Case report: This article describes, using these mathematical models, a patient in whom a secondary dislocation of the fragments of the posterior wall occurred due to involuntary fast movements of the hip after surgical fixation. We have found that absolute values of hip joint reaction force and peak contact hip stress depend on the speed of movement and the angle of abductin and are significantly higher than during full weight bearing.

Conclusions: We recommends to avoid fast movements and isometric exercises in early postoperative period.