Laxity in posterior cruciate sparing and posterior stabilized total knee prostheses

Two series of consecutive total knee replacements were compared retrospectively: 118 HLS II posterior stabilized prostheses (Group 1) versus 138 HLS CP posterior cruciate ligament sparing prostheses (Group 2). Both implants were made by the same manufacturer. The prostheses had been inserted between 1989 and 1992. Mean followup was 4 years. The authors looked for evidence of laxity in the coronal and the sagittal planes, the correlation of laxity with other factors, and the effect of laxity on the objective and subjective outcome as measured with the Knee Society score. Group 2 had significantly more clinical and radiologic laxity. There was little difference between the two groups regarding the overall objective and subjective outcome; however, there was a significantly higher rate of excellent results in Group 1. Longer followup will be required to see whether the implants with laxity are at heightened risk for tibial component wear.