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Background: Recently, anatomic anterior cruciate ligament (ACL) reconstruction is emphasized to improve joint laxity and to potentially avert initiation of cartilage degeneration. There is a paucity of information on the efficacy of ACL reconstructions by currently practiced tunnel creation techniques in restoring normal joint laxity.Study Design: Controlled laboratory study.Hypothesis: Anterior cruciate ligament reconstruction by the anteromedial (AM) portal technique, outside-in (OI) technique, and modified transtibial (TT) technique can equally restore the normal knee joint laxity and ACL forces.Methods: Eight fresh-frozen human cadaveric knee specimens were tested using a robotic testing system under an anterior tibial load (134 N) at 0°, 30°, 60°, and 90° of flexion and combined torques (10-N·m valgus and 5-N·m internal tibial torques) at 0° and 30° of flexion. Knee joint kinematics, ACL, and ACL graft forces were measured in each knee specimen under 5 different conditions (ACL-intact knee, ACL-deficient knee, ACL-reconstructed knee by AM portal technique, ACL-reconstructed knee by OI technique, and ACL-reconstructed knee by TT technique).Results: Under anterior tibial load, no significant difference was observed between the 3 reconstructions in terms of restoring anterior tibial translation (P > .05). However, none of the 3 ACL reconstruction techniques could completely restore the normal anterior tibial translations (P < .05). Under combined tibial torques, both AM portal and OI techniques closely restored the normal knee anterior tibial translation (P > .05) at 0° of flexion but could not do so at 30° of flexion (P < .05). The ACL reconstruction by the TT technique was unable to restore normal anterior tibial translations at both 0° and 30° of flexion under combined tibial torques (P < .05). Forces experienced by the ACL grafts in the 3 reconstruction techniques were lower than those experienced by normal ACL under both the loading conditions.Conclusion: Anterior cruciate ligament reconstructions by AM portal, OI, and modified TT techniques are biomechanically comparable with each other in restoring normal knee joint laxity and in situ ACL forces.Clinical Relevance: Anterior cruciate ligament reconstructions by AM portal, OI, and modified TT techniques result in similar knee joint laxities. Technical perils and pearls should be carefully considered before choosing a tunnel creating technique. [ABSTRACT FROM AUTHOR]

Background: Anterior cruciate ligament (ACL) deficiency alters 6 degrees of freedom knee kinematics, yet only anterior translation and internal rotation have been the primary measures in previous studies. Purpose: To compare the 6 degrees of freedom knee kinematics and the graft forces after single- and double-bundle ACL reconstructions under various external loading conditions. Study Design: Controlled laboratory study. Methods: Ten human cadaveric knees were tested with a robotic testing system under 4 conditions: intact, ACL deficient, singlebundle reconstructed with a quadrupled hamstring tendon graft, and double-bundle reconstructed with 2 looped hamstring tendon grafts. Knee kinematics and forces of the ACL or ACL graft in each knee were measured under 3 loading conditions: an anterior tibial load of 134 N, a simulated quadriceps muscle load of 400 N, and combined tibial torques (10 N·m valgus and 5 N·m internal tibial torques) at 0°, 15°, 30°, 60°, and 90° of knee flexion. Results: The double-bundle reconstruction restored the anterior and medial laxities closer to the intact knee than the single-bundle reconstruction. However, the internal rotation of the tibia under the simulated quadriceps muscle load was significantly decreased when compared with the intact knee after both reconstructions, more so after double-bundle reconstruction (P < .05). The entire graft force of the double-bundle reconstruction was more similar to that of the intact ACL than that of the single-bundle reconstruction. However, the posterolateral bundle graft in the double-bundle reconstructed knee was overloaded as compared with the intact posterolateral bundle. Conclusion: The double-bundle reconstruction can better restore the normal anterior-posterior and medial-lateral laxities than the single- bundle reconstruction can, but an overloading of the posterolateral bundle graft can occur in a double-bundle reconstructed knee. Clinical relevance: Both single-bundle and double-bundle techniques cannot restore the rotational laxities and the ACL force distributions of the intact knee. [ABSTRACT FROM AUTHOR]

Background: The function of the anteromedial (AM) and posterolateral (PL) bundles of the anterior cruciate ligament (ACL) during gait has not been reported. Hypothesis: The AM and PL bundles have distinct functional behavior during the stance phase of treadmill gait. Study Design: Descriptive laboratory study. Methods: Three-dimensional models of the knee were created by magnetic resonance images from 8 healthy subjects. The contour of the 2 bundle attachments were constructed on each model. Each bundle was represented by a straight line connecting its tibial and femoral attachment centroids. Next, the knee kinematics during the stance phase of gait was determined with a dual fluoroscopic imaging system. The relative elongation, sagittal plane elevation, coronal plane elevation, and transverse plane deviation of the 2 bundles were measured directly from heel strike to toe-off. Results: At heel strike, the AM and PL bundles had first peak elongation of 9% ± 7% and 9% ± 13%, respectively. At 50% progress of the stance phase, both bundles were maximally elongated, 12% ± 7% for the AM bundle and 13% ± 15% for the PL bundle. No significant difference was found for each bundle between 40% and ±0% of the stance phase (P > .05). With increasing knee flexion, the sagittal plane and coronal plane elevations of the 2 bundles decreased, whereas the deviation angles increased. Conclusion: Both bundles are anisometric and function in a similar manner during the stance phase of gait. They were maximally elongated throughout the midstance where they were stretched maximally to resist anterior tibial translation. Clinical relevance: This information can be useful for further improving anatomical ACL reconstructions to better reproduce the 2 bundle functions. It may also be useful for designing postoperative rehabilitation regimens to prevent overstretch of the grafts. [ABSTRACT FROM AUTHOR]

Background: The in situ forces of the anteromedial (AM) and posterolateral bundles (PL) of the anterior cruciate ligament (ACL) under simulated functional loads such as simulated muscle loads have not been reported. These data are instrumental for improvement of the anatomical double-bundle ACL reconstruction. Hypothesis: The load-sharing patterns of the 2 bundles are complementary under simulated muscle loads. Study Design: Descriptive laboratory study. Methods: Eight cadaveric knees in this study were sequentially studied using a robotic testing system. Each knee was tested under 3 external loading conditions including (1) a 134-N anterior tibial load; (2) combined rotational loads of 10 N·m of valgus and 5 N·m internal tibial torques; and (3) a 400-N quadriceps muscle load with the knee at 0°, 15°, 30°, 60°, and 90° of flexion. The in situ forces of the 2 bundles of ACL were determined using the principle of superposition. Results: Under the anterior tibial load, the PL bundle carried peak loads at full extension and concurrently had significantly lower force than the AM bundle throughout the range of flexion (P<.05). Under the combined rotational loads, the PL bundle contributed to carrying the load between 0° and 30°, although less than the AM bundle. Under simulated muscle loads, both bundles carried loads between 0° and 30°. There was no significant difference between the 2 bundle forces at all flexion angles (P >.05). Conclusion: Under externally applied loads, in general, the AM bundle carried a greater portion of the load at all flexion angles, whereas the PL bundle only shared the load at low flexion angles. The bundles functioned in a complementary rather than a reciprocal manner to each other. Clinical Relevance: The data appear to support the concept that both bundles function in a complementary manner. Thus, how to re-create the 2 bundle functions in an ACL reconstruction should be further investigated. [ABSTRACT FROM AUTHOR]

Background: Screw and suture fixations are the most commonly used methods of fixation in treatment of anterior cruciate ligament tibial avulsion fractures. Even though a few biomechanical studies have compared the stability of the 2 fixation techniques, a clinical comparison has not yet been reported. Hypothesis: The authors hypothesized that both fixations would be identical in all studied clinical outcome measures at a minimum 2-year follow-up. Study Design: Cohort study; Level of evidence, 3. Materials and Methods: Thirty-three patients treated with either screw fixation (16 patients) or suture fixation (17 patients) within 1 month of the anterior cruciate ligament tibial avulsion fracture (type II or III) without associated ligamentous injury were included. All patients were evaluated at a minimum 2-year follow-up in terms of Lysholm knee scores and return to preinjury activities. Knee stability was compared based on the Lachman test and stress radiography. Results: No significant differences were found between the 2 groups in terms of average Lysholm knee scores (91.7 in the screw group and 92.7 in the suture group, P = .413) at follow-up. All patients except 2 (1 in each group) returned to preinjury activity levels. However, flexion contractures (5° to 10°) were found in 3 patients in the screw group and 2 patients in the suture group without significant intergroup difference. Stabilities based on the Lachman test and instrumented stress radiography were also similar between the 2 groups at follow-up. However, 2 patients in the screw group and 1 in the suture group showed more than 5 mm laxity compared with the contralateral knee on stress radiographs. Conclusion: Both the screw and suture fixation techniques for the anterior cruciate ligament tibial avulsion fracture produced relatively good results in terms of functional outcomes and stability without any significant differences. However, some patients in both groups showed residual laxity or flexion contractures. [ABSTRACT FROM AUTHOR]

Background: The intent of double-bundle anterior cruciate ligament reconstruction is to reproduce the normal anterior cruciate ligament anatomy and improve knee joint rotational stability. However, no consensus has been reached on the advantages of this technique over the single-bundle technique. Hypothesis: We hypothesized that double-bundle anterior cruciate ligament reconstruction could provide better intraoperative stability and clinical outcome than single-bundle reconstruction. Type of study: Cohort study; Level of evidence, 2. Methods: Forty patients with anterior cruciate ligament injury in one knee were recruited; 20 were allocated to a double-bundle anterior cruciate ligament reconstruction group and 20 to a single-bundle anterior cruciate ligament reconstruction group. Intraoperative stabilities at 30° of knee flexion were compared between the 2 groups using a navigation system. Clinical outcomes including Lysholm knee scores, Tegner activity scores, Lachman and pivot-shift test results, and radiographic stabilities were also compared between the 2 groups after a minimum of 2 years of follow-up. Results: Intraoperative anterior and rotational stabilities after anterior cruciate ligament reconstruction in the double-bundle group were significantly better than those in single-bundle group (P = .020 and P < .001, respectively). Nineteen patients (95%) in each group were available at a minimum 2-year follow-up. Clinical outcomes including Lysholm knee and Tegner activity scores were similar in the 2 groups at 2-year follow-up (P > .05). Furthermore, stability results of the Lachman and pivot-shift tests, and radiologic findings at 2-year follow-up failed to reveal any significant intergroup differences (P > .05). Conclusion: Although double-bundle anterior cruciate ligament reconstruction produces better intraoperative stabilities than single-bundle anterior cruciate ligament reconstruction, the 2 modalities were found to be similar in terms of clinical outcomes and postoperative stabilities after a minimum of 2 years of follow-up. [ABSTRACT FROM AUTHOR]