The radiolucent zone in arthroplasty of the knee.

Roentgenograms of 138 knee joint arthroplasties were examined for the presence and extent of a radiolucent zone at the bone-cement interface. Such a zone was significantly more common around the plastic tibial part than around the metallic femoral part of non-hinged prostheses. This observation argues for the theory that the development of heat plays a part in the causation of the zone. In some cases a zone was demonstrable within 1 month of the operation. The frequency and the sizes of such zones increased during the first 6 months after the operation. There was no definite correlation between the development of a radiolucent zone and the clinical symptoms.