Use of a guide instrument for compartmental knee arthroplasty.

To improve the positioning of the tibial component in compartmental knee arthroplasty a guide instrument was introduced. With the guide instrument the position in the frontal plane significantly improved from a mean medial slope of 10 degrees to 2 degrees. In the sagittal plane the change from a mean posterior slope of 5 degrees to 3 degrees was insignificant. The mean value for the Hip-Knee-Ankle angle (HKA) (ideal 180 degrees) was 186 degrees after "free-hand" operation and 183 degrees with the modified operative technique. Thus, it is possible with the aid of a guide instrument to improve the precision in compartmental knee arthroplasty.