The cemented unicondylar knee arthroplasty. An in vitro comparison of three cement techniques.

Three cementation techniques were investigated to determine their effect on initial fixation of unicondylar tibial components. Twenty-one anatomic specimens were divided into three groups. In Groups A and B, the medial tibial plateau was minimally resected. Group A was drill interdigitated and pulse lavaged, Group B was left "as cut". In Group C, the articular cartilage was curetted, exposing the subchondral bone entirely. An Ortholoc II unicondylar prosthesis was cemented onto the tibias, after which a 981-N load was applied anteromedially at 1 Hz for 10,000 cycles. Measurements for anterior and posterior micromotion were taken at the first cycle, every ten cycles for the first 100 cycles, every 100 cycles for the first 1000, and every 250 cycles thereafter. Measurements for anterior subsidence and posterior liftoff were taken after every 1000 cycles. Group A was found to be significantly better than Group B in anterior micromotion, posterior micromotion, and posterior liftoff in all load cycles. Group A was also found to be significantly better than Group C in anterior micromotion, posterior micromotion, and posterior liftoff in all load cycles. The performance of Groups B and C was highly variable. Both groups had specimens with extreme micromotions in response to low loads. Group A provided consistent and superior results. This study shows that cementation techniques employing multiple-drill-hole interdigitation and pulse lavage produce rigid initial fixation and consistent excellent results. Cementing to the smooth subchondral bone or unlavaged cancellous bone was unreliable.