Navigated knee kinematics after cutting of the ACL and its secondary restraint.

PURPOSE: The purpose of this study is to evaluate the kinematics changes of the knee after cutting of the ACL with or without injury of the anterolateral structures. METHODS: In this study, the role of the ACL and one of the secondary restraints in controlling knee stability using a navigation system was evaluated. The kinematics of the knee was evaluated in different conditions of instability: ACL intact, after dissection of the posterolateral (PL) bundle, after dissection of the anteromedial (AM) bundle, and after lesion of the lateral capsular ligament (LCL). Anterior tibial translation and rotation were measured with a computer navigation system in 10 fresh-frozen cadaveric knees by use of a manual maximum load. Anterior translation was evaluated at 30°, 60°, and 90° of flexion; rotation at 0°, 15°, 30°, 45°, 60°, and 90°. RESULTS: Cutting the PL bundle does not increase anterior translation and rotation of the knee. Cutting the AM bundle significantly increased the anteroposterior (AP) translation at 30° and 60° (P = 0.01), but does not increase rotation of the knee. Cutting the LCL increased anterior translation at 60° (P = 0.04) and rotation at 30°, 45°, and 60° (P = 0.03). CONCLUSIONS: Within the testing conditions of this study, the PL bundle does not affect anterior translation and rotation of the knee; the AM bundle is the primary restraint of the anterior translation but does not affect rotation of the knee while the lesion of the LCL increases tibial rotation and could be related to the pivot shift phenomenon, so it is more correct and biomechanical valid to assess and repair the associated lesion of the antero-lateral structure of the knee at the time of ACL surgery.

Biomechanical evaluation of different anterior cruciate ligament fixation techniques for hamstring graft.

BACKGROUND: A number of anterior cruciate ligament (ACL) fixation techniques are currently in use. Slippage or failure of the graft by excessive loading or aggressive rehabilitation may result in an unstable knee. Load and slippage of the ACL graft varies according to the fixation technique used. METHODS: Graft slippage, load to failure, and stiffness were evaluated using an animal model. Six soft tissue ACL fixation techniques and bone cement as a fixation device were tested: group A, Endo Button CL-Bio RCI; group B, Swing Bridge-Evolgate; group C, Rigidfix-Intrafix; group D, Bone Mulch-Washer Lock; group E, Transfix-Retroscrew; group F, Transfix-Deltascrew; group G, Kryptonite bone cement. Maximum failure load, stiffness, and slippage at the 1st and 1000th cycles and mode of failure were evaluated. RESULTS: The maximum failure load was significantly higher in group B (1030 N) and significantly lower in group E (483 N) than in the others. The stiffness of group B (270 N/mm) was significantly higher than the others. As for the mode of failure, group C showed failure in the femoral side in all tests (four device ruptures and two tendon ruptures on the femoral side). All failures of the other groups occurred on the tibial side except one test in group A. All failures in group G were due to slippage of the tendons. CONCLUSION: Load to failure and stiffness was significantly different between the ACL fixation techniques. All but one of the fixation techniques showed sufficient properties for adequate postoperative rehabilitation. Bone cement used as a fixation device in soft tissue grafts did not seem to provide adequate initial fixation suitable for early rehabilitation after ACL reconstruction.

Double bundle or single bundle plus extraarticular tenodesis in ACL reconstruction? A CAOS study.

Anatomic reconstructions of anterior cruciate ligament (ACL) with double bundle gracilis and semitendonosus tendons graft, reproducing AM and PL bundles, have been introduced to offer a better biomechanical outcome, especially during rotatory loads. On the other hand, many methods of tenodesing the lateral aspect of the tibia to the femur to reduce internal rotation (IR) of the tibia and minimize anterior translation of the tibia relative to the femur as a backup for intra-articular reconstruction, have been also suggested. The goal of this study is to evaluate the effect, on the IR of the tibia, of a lateral reconstruction in addition to a standard single bundle ACL reconstruction as compared with an anatomic double bundle ACL reconstruction. Computer assisted ACL reconstruction has been used because it could be very effective in evaluating the global kinematic performance of the reconstructed knee. We selected 20 consecutive ACL reconstruction procedures to be performed in males in our hospital. Patients were alternately assigned to one of the two groups--group A: standard single bundle ACL reconstruction with doubled gracilis and semitendinosus tendons graft with an arthroscopically assisted two incisions technique and a lateral extraarticular reconstruction; group B: double bundle ACL reconstruction with doubled gracilis and semitendinosus tendons graft with an arthroscopically assisted two incisions technique. In all ACL reconstruction procedures navigation process was performed. Both surgical techniques reduced significantly AP displacement, IR and external rotation (ER) of the tibia respect to pre-operative ACL deficient condition (p<0.05). Comparing the group A after the single bundle reconstruction and the group B after the AM bundle fixation, non differences were found in AP displacement, IR and ER of the tibia (p=0.75, p=0.07 and p=0.07 respectively; power: 0.94). Comparing the group A after the addition of the lateral tenodesis and group B after the PL bundle fixation (AM+PL) no differences in AP tibial displacement and in ER of tibia were found (p=0.9 and 0.15, respectively; power: 0.99); however a significant reduction in IR of the tibia was found in group A after the addition of the lateral tenodesis respect to the group B after the addition of the PL bundle (p=0.0001; power: 0.26). On the basis of our study, the addition of a lateral extraarticular reconstruction to a standard single bundle ACL reconstruction with hamstrings tendons graft in an "in vivo" reconstruction, is more effective in reducing the IR of the tibia at 30 degrees of knee flexion, as compared with a standard single bundle ACL reconstruction and with an anatomic double bundle reconstruction is confirmed.