Fatigue testing of a proximal femoral hip component.

The Gothenburg Osseointegrated Titanium (GOT) implant is a novel total hip replacement including a metaphyseal loading proximal femoral component fixed in the retained femoral neck. Endurance testing was performed under conditions analogous to ISO 7206-4: 1989. The cement-free implant is not fixed distally within the intramedullary canal, so distal embedding (as specified in the standard) would have been unrealistic. Instead glass-fibre-reinforced epoxy (GFRE) bushings were used to model reduced bone support mid-length at the medial cortex and distally at the lateral cortex. Such support simulated proximal bone loss, realistically reproducing the effect of osteolysis or fixation failure. Under such conditions the component survived unbroken for 10 million cycles at 3.0 kN peak load.

Penetration in trochanteric fractures of the femur treated with rigid nail plates.

One hundred and twelve trochanteric fractures have been analysed. A Jewett nail-plate was used in 81 patients and a Thorton nail-McLaughlin plate in 31. Penetration of the nail into or through the hip joint was the only complication studied in detail. It occurred in 41 cases: 31 (38 per cent) with the Jewett nails and 10 (33 per cent) in the other group. Both groups are comparable in that the nail-plate acts as a single rigid unit and the nail/plate angle varied, but the overall incidence of migration of the nail was similar. All the 112 cases were reviewed as one group. Penetration was more common in comminuted unstable types of fracture, in those poorly fixed, and in the older patients. Sixteen (14 per cent) well-fixed fractures showed penetration. It appears that one important additional reason for penetration in this series was the rigidity of the device and the poor quality of the bone. The incidence of nail penetration in comminuted unstable fractures of the femur might be reduced by using methods of fixation other than rigid nail-plates.