Effects of the balanced gap technique on femoral component rotation in TKA.

UNLABELLED: Femoral component rotation from a total knee prosthesis can be determined by either a measured resection technique or a balanced gap technique. With the balanced gap implantation technique, femoral component rotation can vary freely within the restrictions produced by soft tissue structures. Because internal rotation might cause patella problems, the effect of ligament releases on femoral component rotation in a prospective clinical study was studied. Femoral component rotation was measured intraoperatively with a tensor applied in flexion at 150 N in 87 knees. Great interpatient variability was found; femoral component rotation, reference from the posterior condyles, ranged from -4 degrees to 13 degrees . There was no difference in femoral component rotation of knees with or without ligament releases in extension. However, knees with major medial release had less external femoral component rotation than knees with minor lateral releases. Preoperative alignment had no influence on femoral component rotation. The use of the balanced gap implantation technique theoretically will result in a balanced flexion gap, but the amount of femoral component rotation will be variable owing to patient variability and variation in ligament releases.

LEVEL OF EVIDENCE: Level II, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.