Comparison of the mechanical performance of three types of unilateral, dynamizable external fixators. An experimental study.

Due to the increasing popularity of unilateral dynamizable external fixators for treating tibial shaft fractures, many new devices are being introduced onto the market. Especially in such half-frame fixators, the choice of any particular device depends above all on the stability of its construction. This study compares the biomechanical stability of three systems tested in axial compression, torsion, and both anterior-posterior and medial-lateral bending. In terms of the nondynamized phase, the AO/ASIF tubular fixator (as a one-plane, double-tube, unilateral frame) and the Martin Mono-Dynafix are, in general, less stable than the Orthofix fixator. After dynamization, the AO/ASIF system becomes particularly weak and offers low resistance especially to torque and any force that is perpendicular to the plane of assembly. The other two tested devices evinced much more stability; the Orthofix fixator seems superior to the Dynafix due to the different diameter of its screws.

Dislocation and fracture-dislocation of the hip.

Of 54 patients with posterior dislocations of the hip of type I and type II (Stewart and Milford 1954), 47 were followed for a mean period of 6.7 years (2 to 11). Of these, 23 had dislocation with minimal lesions of the acetabulum (type I) and 24 had an avulsed dorsocranial fragment (type II). All were reduced by closed methods within six hours. The subsequent treatment of type I dislocations was conservative. At the beginning of the period type II injuries were treated conservatively, but surgery was increasingly chosen for later cases. Type I dislocations had significantly better results (p < 0.05) than type II fracture-dislocations, regardless of the method of treatment. There were no essential differences between the results of surgical and conservative treatment in type II dislocations.

Fractures of the posterior tibial margin: their role in the prognosis of malleolar fractures.

One hundred forty-two patients with malleolar fractures were followed up for an average of 5.7 years postoperatively. In 80 cases (56.4%) we found no lesion of the distal articular surface of the tibia; 62 patients (43.6%) had a fracture of the posterior tibial margin. Both groups were closely matched with regard to fractures of the lateral and medial malleolus. The long-term results were significantly poorer when a fracture of the posterior tibial margin was additionally present, even in cases with a small marginal fragment of the lip of the tibia. Further, we found a clear relationship between the articular involvement and the incidence of post-traumatic osteoarthrosis in cases with no additional osteosynthesis of the fragment. In cases of larger fragments, the long-term results after anatomic reduction and additional osteosynthesis were on the whole far better than in cases treated conservatively.