Gait-analytical studies in patients treated by valgus tibial head osteotomy

So far, the use of imaging methods has been the only way of evaluating unicompartmental gonarthritis caused by malalignment of lower extremity axes and the results of operative correction. Unfortunately, radiological visualization does not give any information about the actual loads on the joint, i.e. the forces and moments acting on it under dynamic conditions. These can be determined by means of gait-analytical measurements. The authors explain how the anomalous loading that occurs in the knee joint in the case of varus gonarthritis can be calculated and assessed. The mean maximum varus moment of knee joints in a group of patients with varus deformity was 0.74 Nm\kg, which was significantly higher than that in a control group (0.63 Nm\kg). Even after correction of the axes, increased maximum moments - some of them independent of the angle of the knee and of the correction angle - were observed in 30% of the cases investigated. These cases were found to be characterized by a predisposition to revarization. Knee joints in which the preoperative varus moment was significantly high or there was a tendency to undercorrection were especially likely to show these features. For these reasons, valgus tibial head osteotomies should generally be performed with slight overcorrection. If the preoperative gait analysis has already confirmed that significantly increased varus forces are in play, a definite overcorrection to about 5degrees beyond the physiological angle should be the aim.