An experimental study of devices for internal fixation of distal femoral fractures

Tibial traction for distal femoral fractures, followed after four to eight weeks by plaster, is the common treatment. Because of improved methodology, the proportion of surgically treated fractures had increased. Stable osteosynthesis with different plates is an established therapy for distal femoral fractures. In elderly or other patients with bone fragility, however, these operations often fail. The majority of the distal femoral fractures occur in such patients, and traction in bed is therefore often used. A less rigid device was constructed to meet the special circumstances with bone fragility. This device consists of two Ender's nails: one is inserted from each condyle, and each is connected to two cancellous screws traversing both condyles. The strength of this semielastic osteosynthesis was compared with four existing devices (AO, Rush, Zickel, Ender). Fixation was carried out in 17 pairs of osteotomized postmortem preparations from patients older than 60 years of age. The specimens were submitted to constant bending rate, and the load deformation was registered. The fixation with the condylar plate was strongest and showed the lowest flexibility. The Ender's nails and the Rush pins showed a tendency to lose their Condylar stabilization early. This was less pronounced with the Zickel nail, which, however, tended to displace at the osteotomy site during insertion and fracture the proximal fragment due to the limited bending ability of the blade construction. The new, semielastic device (ECS) was constructed to meet the special circumstances with bone fragility. It consists of two cancellous screws traversing both condyles. It combined easy insertion with moderate flexibility and high residual strength. In extension, it deflected 40 degrees without influencing residual stability. It is an interesting alternative to rigid internal fixation or traction in bed for osteoporotic patients with distal femoral fractures. In combines rigid screw fixation in the condylar part with an elastic adjustment in the femoral shaft above.