Navigation in ACL reconstruction

Only a global kinematics evaluation of graft performance, made during surgery, could represent a real improvement in anterior cruciate ligament (ACL) reconstruction. This paper describes a new protocol for an accurate and extensive computer-assisted in vivo evaluation of joint laxities during ACL reconstruction. Our protocol allows a quantitative evaluation of all residual instabilities: it would be very helpful in the evaluation of graft performances. Fifteen in vivo kinematics evaluations during ACL reconstruction were performed using an optical localizer and custom software. The capability of the protocol was studied by analyzing the accuracy and the repeatability of the results, the ergonomics of the setup, time taken, interactions with the surgical steps, and efficacy of the acquisitions. Repeatability of the tests, at maximum force, remained under 1 mm/2°. Repeatability in tibia position and orientation was lower than 1 mm/4°. Secondary laxities during stress tests remained under 2 mm/3°. Added time to surgery was about 11 min. ACL graft increased joint stability up to 52% with respect to the preoperative level. The simplicity and morbidity of the test procedure and system was minimally invasive and allowed a quantitative evaluation of knee laxities at time zero. The repeatability of tests opens the way for future research on In vivo evaluation of different ACL reconstruction techniques, which may lead to a better understanding of associated lesions and their role in the global knee stability.