BIOMECHANICAL COMPARISON OF METHODS OF FIXATION OF ISOLATED OSTEOTOMIES OF THE POSTERIOR ACETABULAR COLUMN

Ten fresh frozen specimens of a hemipelvis, including the hip joint, c apsule and proximal femur, from elderly cadavers were used to evaluate three methods of internal fixation of isolated posterior column osteo tomies. Intact and reconstructed specimens were tested at 30-degrees a nd 60-degrees of hip flexion in a specially designed joint simulator T he three methods of fixation used were a single 3.5 mm reconstruction plate, two such plates, and a 4.5 mm lag screw with a single plate. Mo tion at the fracture site in three orthogonal directions, and the over all stiffness of the construct, were recorded simultaneously. No signi ficant differences were noted in stiffness for the three procedures an d all retained 80% of the intact stiffness. At 60-degrees of flexion, smaller interfragmentary compliances were allowed by fixation with a l ag screw and a neutralisation plate (p < 0.05). At 30-degrees, the pos ition of the load plane relative to the fracture Plane allowed less in terfragmentary motion, so that no significant differences were found b etween the 3 methods.