Experimental tests concerning the biomechanical behaviour of pertrochanteric osteosyntheses

The biomechanical behaviour of pertrochanteric fractures stabilized by means of an angled plate or flexible condylar nails was characterized by mechanical testing. The stability and the types of motion occurring under dynamic load in the vicinity of the fracture and the effect on the implant were examined. The mechanical test results corroborated clinical experiences. In the case of extramedullary anchorage of implants, stability under load is possible only if an intact cortex on the medial side of the fracture guarantees the bearing of compressive load. With flexible condylar nails, however, it is possible to achieve a permanent load capacity up to approximately 100 kp, even if medial support is lacking, by putting the fracture in a valgus position so that the load-bearing arm is shortened. It was also possible to estimate the actual loading on the operated leg within the immediate postoperative phase by means of the "stabilization effect".