Lateral unicompartmental knee arthroplasty: survivorship and technical considerations at an average follow-up of 12.4 years.

Successful medial unicompartmental knee arthroplasty is becoming standard; however, the "screw-home" mechanism, internal femoral rotation on a fixed tibia as the knee is fully extended, should be taken into account with lateral compartment arthroplasty. Twenty-nine consecutive lateral unicompartmental arthroplasties were performed with our unique tibial component positioning in 10 degrees to 15 degrees of internal rotation to compensate for the "screw-home" mechanism. The Hospital for Special Surgery knee score and serial radiographs were used in the evaluation of each patient. The mean duration of follow-up was 12.4 years with no revisions. The HSS score was excellent or good in all knees. The average postoperative femoral-tibial alignment was 5 degrees of valgus, and the average posterior tibial slope was 6 degrees . Lateral unicompartmental arthroplasty can provide excellent long-term results with modified positioning of the tibial component.