Diagnostic study, Level I.

The Tape Locking Screw (TLS(®)) system, developed in 2003, is a new anterior cruciate ligament (ACL) reconstruction method that is based on three principles: one hamstring tendon is harvested, prepared into a short (50 to 60mm), four to five strand closed loop, with a diameter of 8 to 10mm and a 500N pre-load; the tunnels are shorter than usual (10 or 15mm) and created in a retrograde manner to match the diameter of each end of the graft. Maximum press-fit into the bone recesses is obtained by a specific graft introduction method; femoral and tibial fixation is provided by polyethylene terephthalate tape strips, or TLS(®) strips, that pass through each end of the closed tendon loop and attach to bone with a dedicated interference screw, the TLS(®) screw. Our preliminary clinical evaluation consisted of a follow-up of 134 patients.

The aim of this study was to evaluate at time-zero four tibial fixations on four major criteria: the elongation and cyclic stiffness of the hamstring graft construct under cyclic loading, the yield load and pullout stiffness under load at failure. Four fixation systems were tested: the Delta screw, the WasherLoc, the TightRope Reverse and the tape locking screw on 32 tibiae of adult pigs using 32 pairs of human semitendinosus and gracilis tendons. Two tests were performed: cyclic tests using loads at 70-220 N, to measure the elongation at the end of the cycles, followed by load-to-failure testing to measure the yield load and the cyclic stiffness. The mean elongation was 1.23 mm for the TLS, 3.81 mm for the Delta, 3.59 mm for the WasherLoc and 3.91 mm for the TightRope. The mean yield loads and SD were 1,015 ± 129 N for the TLS, 844 ± 394 N for the Delta, 511 ± 95 N for the WasherLoc and 567 ± 112 N for the TightRope. The results showed the significant superiority of TLS and Delta over WasherLoc and tibial TightRope in regard to yield load. The results showed the significant superiority of TLS over the other fixations in regard to slippage. The TLS system and the Delta screw provide a better quality of primary fixation to the tibia, but further in vitro studies are needed.

No abstract

The purpose of this study was to develop a radiological method which would be preoperatively available to help determine the best graft placement (with respect to isometricity as well as absence of graft impingement) for all knees. The radiological method is described in full detail. We also present the most significant experimental work supporting our development. Firstly, we studied the path followed by radio-opaque objects inserted in the mobile tibia around the fixed femur. Secondly, we compared the distances measured between selected femoral and tibial points radiologically (according to our method) and clinically (with a currently available isometer). The main results were: (1) every tibial point considered moves on an arc of a circle centered or a corresponding femoral point. We should then speak of pairs of isometric points instead of a single femoral isometric zone; (2) the more posterior the tibial point, the more anterior and distal the corresponding femoral point and vice versa; (3) the distance variations induced by rotation did not exceed 1.5 to 2.5 mm when measured either radiologically or clinically; (4) on the radiological and clinical measurements, the difference of length variations during flexion was also very small (mean 0.22 mm; SD 1.2 mm). We conclude that this very simple method allows us to find the femoral transition line for every knee (whatever its size, shape or dynamics). It aids preoperative planning in anterior cruciate ligament graft reconstruction.