INFLUENCE OF LIGAMENT TENSION ON GAP’S DETERMINING IN TKA BY CAS TECHNIQUE

Abstract

To obtain a good outcome in TKA is mandatory to reach a balanced flexion-extension gap. That requires, during surgery, to choose the amount of bone resection and the position of the prosthetic component, mainly the femoral one. These choices are based upon some bone landmarks, but overall could be based upon a proper ligament’s tension, as a preview of ideal kinematics.> About this topic several Authors published in the last decade, but the determination of a value of ligament’s tension still remains a big issue.

So we made an hydraulic knee analyzer (HKA® ) computer integrated and we tested and validated by a cadaveric study. Aims of this study are: to validate the reproducibility, in vivo, of the results of the cadaveric study, and subsequently to evaluate the outcome between two groups of patients undergone to surgery, one by conventional technique and the other by C.A.S. The previous cadaveric study, that was done on ten fresh knees by HKA®, highlighted a relation between ligament’s tension in flexion and in extension, 4 bar vs 6 bar. Twenty patients were operated by C.A.S. (Navitrack® Centerpulse-Zimmer) and HKA®, Twenty patients were operated conventionally, by the same surgeon and utilizing the same prosthesis (Innex® Centerpulse-Zimmer). Preoperative and postoperative study was performed by: long lenghth lower limb x-ray, IKSS score and SF 36 score.

In all the C.A.S. patients it’s got a rectangular and balanced gap, both in flexion and extension, utilizing a 4 bar in flexion and 6 bar in extension, as shown in the cadaveric study.

The comparison between two groups of patients has underlined a better functional outcome in the C.A.S. group.