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Comparison of Graft Length Changes During Knee Motion Among 5 Different Anatomic Single-Bundle Anterior Cruciate Ligament Reconstruction Approaches: A Biomechanical Study

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Comparison of Graft Length Changes During Knee Motion Among 5 Different Anatomic Single-Bundle Anterior Cruciate Ligament Reconstruction Approaches: A Biomechanical Study

Yoshie Tanabe et al. Orthop J Sports Med.

Abstract

Background: In several anatomic single-bundle anterior cruciate ligament (ACL) reconstruction (ASB-ACLR) procedures, the femoral and tibial tunnel apertures are created at different locations within the native ACL attachment area.

Hypothesis: Graft length changes during knee motion will be different among ASB-ACLR procedures with different femoral and tibial tunnel aperture locations.

Study design: Controlled laboratory study.

Methods: A total of 12 cadaveric knees were used in this study. In each knee, 4 and 3 thin tunnels were created within the ACL attachment area on the femur and the tibia, respectively. Using 1 of 5 different combinations of femoral and tibial tunnel aperture location, 5 ASB-ACLRs were performed on each knee. In each reconstruction approach, a strong thread was used in place of the tendon graft, and the tibial graft end was tethered to a custom-made isometric positioner at 0° of knee flexion, with an approximately 12-N load applied to the thread. Then, each specimen underwent 5 cycles of knee flexion-extension motion in a range between 0° and 120°, and graft length changes were determined for each SB-ACLR approach.

Results: The length changes of the graft were significantly different among the 5 ASB-ACLRs. The maximum length change values of the 3 grafts that were implanted between the femoral and tibial centers of the posterolateral bundle attachments or implanted into the femoral tunnel created at the center of the fanlike extension fiber attachment were significantly greater than those of the graft implanted between the centers of the anteromedial bundle attachments (P < .0001) and of the graft implanted between the centers of the whole ACL attachments (P < .0001).

Conclusion: The length changes of the graft during knee motion were significantly different among the 5 ASB-ACLR approaches, even though all of the tunnel apertures were created within the femoral and tibial attachments of the native ACL.

Clinical relevance: The grafts in the first 3 graft locations may be so relaxed during knee flexion that they cannot resist anterior drawer loads exerted on the tibia.

Keywords: ACL; anatomic reconstruction; biomechanics; graft isometry; graft length; single bundle.

Conflict of interest statement

One or more of the authors has declared the following potential conflict of interest or source of funding: The threads and fixation devices used in this study were donated by Smith & Nephew Endoscopy Japan. AOSSM checks author disclosures against the Open Payments Database (OPD). AOSSM has not conducted an independent investigation on the OPD and disclaims any liability or responsibility relating thereto.

Figures

Figure 1.
Figure 1.
Specimen preparation. (A and B) The whole attachment area of the ACL was divided into 8 partitions according to the functional anatomy-based division method. Areas A, B, C, and D comprised the fanlike extension fiber attachment area, and areas E, F, G, and H comprised the direct midsubstance fiber attachment area. (C) The center of each area on the femur was defined as points A through H. A Kirschner wire was inserted at points C, E, and H and the midpoint (point F/G) between points F and G. (D) A Kirschner wire was inserted at points 1, 2, and 3 on the tibia. Point 1 was the center of the anteromedial bundle attachment, and point 3 was the center of the PL bundle attachment. Point 2 was the midpoint between the points 1 and 3.
Figure 2.
Figure 2.
This schematic picture shows the femoral and tibial tunnel aperture locations created in the 5 anatomic single-bundle reconstruction procedures. The femoral and tibial centers of the tunnel (H, E, F/G, and C on the femur; 1, 2, and 3 on the tibia; see Figure 1) were marked on the same photograph of the native femur–anterior cruciate ligament–tibia complex, which was taken at 0° and 90° of knee flexion, respectively. Each line shows a distance between the femoral and tibial centers. The photographs depict a cadaveric knee that was not used for the present study.
Figure 3.
Figure 3.
(A) A custom-made isometric positioner was composed of an outer metal cylinder, an inner metal cylinder, and (B) a coil spring. The outer cylinder was fixed on the tibial cortex. A thread graft was tethered to the inner cylinder. The coil spring, the spring coefficient of which was 716 N/m, was installed between the outer and inner cylinders. IC, inner cylinder; OC, outer cylinder; PI, position indicator.
Figure 4.
Figure 4.
The apparatus to fix the femur. The tibia was free to allow knee motion in 6 degrees of freedom. A hinge-type circular protractor of the goniometer was set at the center of the knee motion. The examiner manually made 5 cycles of flexion-extension motion of the tibia using a smooth rod to avoid applying any varus-valgus or rotatory forces.
Figure 5.
Figure 5.
Relative length changes in the 5 thread grafts. The length at 0° of knee flexion was defined as the reference length (zero). Each point and error bar shows the mean of the length change values from 12 measurements and the standard deviation, respectively. A negative value indicates a decrease in the graft length. A 2-way analysis of variance showed a significant difference not only among the flexion angles (P < .0001) but also among the 5 grafts (P < .0001). According to a post hoc test, a significant difference was found between graft H-1 and each of the other 4 grafts (P < .0001 for all) as well as between graft F/G-2 and each of grafts C-1 and C-2 (P < .0001 for both).
Figure 6.
Figure 6.
Comparison of the maximum length change among the 5 thread grafts. Each bar and error bar shows the mean of 12 measurements and the standard deviation, respectively: graft H-1 (3.0 ± 0.8 mm), graft E-3 (5.9 ± 1.0 mm), graft F/G-2 (4.6 ± 0.6 mm), graft C-1 (6.8 ± 1.5 mm), graft C-2 (6.7 ± 1.2 mm). A 1-way analysis of variance showed a significant difference (P < .0001) among the 5 grafts. The results of the post hoc test are shown in the graph.
Figure 7.
Figure 7.
Changes in the load applied to each thread graft by the spring installed in the isometric positioner. A 2-way analysis of variance did not show any significant difference among the flexion angles or among the 5 grafts.
Figure 8.
Figure 8.
To confirm the length data from the thread grafts in the study, we made experimental observations of grafts H-1, F/G-2, and C-2 at 0° and 90° of knee flexion, using a semitendinosus tendon in 3 additional knee specimens. At 0° of knee flexion, each tendon graft was tense. At 90° of knee flexion, graft H-1 was mostly tense and graft F/G-2 was slightly loosened, while graft C-2 was extremely slack.

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References

    1. Arnold MP, Kooloos J, van Kampen A. Single-incision technique misses the anatomical femoral anterior cruciate ligament insertion: a cadaver study. Knee Surg Sports Traumatol Arthrosc. 2001;9(4):194–199. - PubMed
    1. Bull AMJ, Andersen HN, Basso O, Targett J, Amis AA. Incidence and mechanism of the pivot shift: an in vitro study. Clin Orthop Relat Res. 1999;363:219–231. - PubMed
    1. Fleming B, Beynnon BD, Johnson RJ, McLeod WD, Pope MH. Isometric versus tension measurements: a comparison for the reconstruction of the anterior cruciate ligament. Am J Sports Med. 1993;21(1):82–88. - PubMed
    1. Forsythe B, Kopf S, Wong AK, et al. The location of femoral and tibial tunnels in anatomic double-bundle anterior cruciate ligament reconstruction analyzed by three-dimensional computed tomography models. J Bone Joint Surg Am. 2010;92(6):1418–1426. - PubMed
    1. Furia JP, Lintner DM, Saiz P, Kohl HW, Noble P. Isometry measurements in the knee with the anterior cruciate ligament intact, sectioned, and reconstructed. Am J Sports Med. 1997;25(3):346–352. - PubMed

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