The biomechanics of interference screw fixation of patellar tendon anterior cruciate ligament grafts

Abstract

Twenty-seven paired human cadaveric knee specimens were used to determine the effect of surgical technique and various interference screw parameters on the pullout strength of patellar tendon femoral bone blocks. The study compared the fixation strength of endoscopically inserted and conventional "rear-entry" screws of different diameters and lengths. In all tests the most frequent mode of failure was bone block pullout from the interference screw. There was no significant difference in fixation strength between 9-mm diameter screws inserted through a conventional rear-entry technique and 7-mm diameter screws inserted through an endoscopic technique. There was no significant effect of screw length on fixation strength. The pullout force for 20-mm long screws increased on average 120% when 7-mm diameter screws were compared with 5.5-mm diameter screws. There was no significant effect of increased screw core diameter on fixation strength. There was a weak positive correlation (r2 = 0.45) between screw insertion torque and pullout force. Our measured mean pullout force for the 7-mm endoscopically inserted screws of 362 +/- 198 N represents 20.1% of the failure load of the normal young adult anterior cruciate ligament. Our data indicate that properly inserted 7-mm diameter endoscopic interference screws can provide fixation strengths of patellar tendon anterior cruciate ligament grafts equivalent to those of conventional 9-mm diameter rear-entry, outside-in screws.

Fixation strength of interference screw fixation in bovine, young human, and elderly human cadaver knees: Influence of insertion torque, tunnel-bone block gap, and interference

“…(695 N). Brown et al [1] reported that insertion torque is a weak predictor of failure load (R 2 = 0.45, P < 0.05). Based on their linear correlation, a mean insertion torque of 1 ft.-lb.…”

Comparative biomechanical study of the Ligament Plate® and other fixation devices in ACL reconstruction

“…3 The Ligament Plate® (Solco Biomedical, Seoul, Korea) Fig. 2 The implants are from left to right: EndoButton®, TransFix®, BioScrew®, and Ligament Plate® ful early rehabilitation, fixation strength of the graft is the most important factor [3,6,18].…”

“…The grafts most commonly used are the BPTB and hamstring tendon. With the technical improvement of the femoral fixation devices the use of hamstring tendons in ACL reconstruction is on the rise [6]. In this study, the Ligament Plate® (Solco Biomedical, Seoul, Korea) was developed as a femoral fixation device that can provide adequate early fixation strength, and the usefulness of the Ligament Plate® was evaluated through biomechanical comparative studies with other fixation devices.…”

A Prospective study on the functional outcome following arthroscopic ACL reconstruction with the femoral interference screw placed through the PT (Patellar Tendon) portal and the AM (Antero-Medial) portal

“…The surgical reconstruction of the anterior cruciate ligament with Bone-Patellar tendon-Bone autograft represents an attempt to re-establish knee kinematics. It has the added advantage of bone to bone healing and it does not sacrifice the knee stabilizers [11] .Various factors affect the pullout strength of the graft: bone block size, quality of bone, gap between bone block and tunnel, screw diameter and length and the angle between screw and bone block (parallel or divergent) [30][31][32][33][34][35][36] . Parallel placement of the screw with respect to femoral and tibial tunnel is desired as it is one of the factors which affect the pullout strength of the graft [32] .…”