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Comparative Study
, 39 (12), 2604-10

Biomechanical Evaluation of Knee Joint Laxities and Graft Forces After Anterior Cruciate Ligament Reconstruction by Anteromedial Portal, Outside-In, and Transtibial Techniques

Affiliations
Comparative Study

Biomechanical Evaluation of Knee Joint Laxities and Graft Forces After Anterior Cruciate Ligament Reconstruction by Anteromedial Portal, Outside-In, and Transtibial Techniques

Jae Ang Sim et al. Am J Sports Med.

Abstract

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.

Figures

Figure 1
Figure 1
Intra-articular position of the tibial guide tip (DePuy Mitek) for transtibial technique.
Figure 2
Figure 2
Femoral graft fixation in the outside-in technique was achieved by flipping an EndoButton (Smith & Nephew Endos-copy) on a 14-mm spiked washer (DePuy Mitek), which was impacted onto the lateral femoral cortex at the tunnel entrance.
Figure 3
Figure 3
Anterior tibial translations under 134-N anterior tibial load. “I” and “D” represent statistically significant differences compared with the ACL-intact knee and ACL-deficient knee, respectively (P < .05). Error bars represent standard deviation. ACLR-AM, ACL reconstruction by anteromedial portal technique; ACLR-OI, ACL reconstruction by outside-in technique; ACLR-TT, ACL reconstruction by transtibial technique.
Figure 4
Figure 4
Anterior cruciate ligament (ACL) and ACL graft forces under 134-N anterior tibial load. “I” represents statistically significant difference compared with the ACL-intact knee (P < .05). Error bars represent standard deviation. ACLG-AM, ACL graft force in ACL reconstruction by anteromedial portal technique; ACLG-OI, ACL graft force in ACL reconstruction by outside-in technique; ACLR-TT, ACL graft force in ACL reconstruction by transtibial technique.
Figure 5
Figure 5
Anterior tibial translations under 10-N·m valgus and 5-N·m internal tibial combined torques. “I”, “D”, “A”, and “O” represent statistically significant differences compared with the ACL-intact knee, ACL-deficient knee, ACL-reconstructed knee by anteromedial portal technique, and ACL-reconstructed knee by outside-in technique, respectively (P < .05). Error bars represent standard deviation. ACLR-AM, ACL reconstruction by anteromedial portal technique; ACLR-OI, ACL reconstruction by outside-in technique; ACLR-TT, ACL reconstruction by transtibial technique.
Figure 6
Figure 6
Anterior cruciate ligament (ACL) and ACL graft forces under 10-N·m valgus and 5-N·m internal tibial combined torques. “I” and “O” represent statistically significant differences compared with the ACL-intact knee and ACL-reconstructed knee by outside-in technique, respectively (P < .05). Error bars represent standard deviation. ACLG-AM, ACL graft force in ACL reconstruction by anteromedial portal technique; ACLG-OI, ACL graft force in ACL reconstruction by outside-in technique; ACLR-TT, ACL graft force in ACL reconstruction by transtibial technique.

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