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Scientific Article   |    
Effect of the Angle of the Femoral and Tibial Tunnels in the Coronal Plane and Incremental Excision of the Posterior Cruciate Ligament on Tension of an Anterior Cruciate Ligament Graft: An in Vitro Study
Richard Simmons, MS; Stephen M. Howell, MD; M. L. Hull, PhD
View Disclosures and Other Information
Investigation performed at the University of California at Davis, Davis, California

Richard Simmons, MS
1153 Calle Emparrado, San Marcos, CA 92069

Stephen M. Howell, MD
8100 Timberlake, Suite F, Sacramento, CA 95823. E-mail address for S.M. Howell: sebhowell@aol.com

M.L. Hull, PhD
Department of Mechanical Engineering, Bainer Hall, 1 Shields Avenue, University of California at Davis, Davis, CA 95616

In support of their research or preparation of this manuscript, one or more of the authors received grants or outside funding from the ACL Study Group, courtesy of AirCast Corporation. In addition, one or more of the authors received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity (Arthrotek, Inc.). No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the authors are affiliated or associated.

J Bone Joint Surg Am, 2003 Jun 01;85(6):1018-1029
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Abstract

Background: High tension in an anterior cruciate ligament graft adversely affects both the graft and the knee; however, it is unknown why high graft tension in flexion occurs in association with a posterior femoral tunnel. The purpose of the present study was to determine the effect of the angle of the femoral and tibial tunnels in the coronal plane and incremental excision of the posterior cruciate ligament on the tension of an anterior cruciate ligament graft during passive flexion.

Methods: Eight cadaveric knees were tested. The angle of the tibial tunnel was varied to 60°, 70°, and 80° in the coronal plane with use of three interchangeable, low-friction bushings. The femoral tunnel, with a 1-mm-thick posterior wall, was drilled through the tibial tunnel bushing with use of the transtibial technique. After the graft had been tested in all three tibial bushings with one femoral tunnel, the femoral tunnel was filled with bone cement and the tunnel combinations were tested. Lastly, the graft was replaced in the 80° femoral and tibial tunnels, and the tests were repeated with excision of the lateral edge of the posterior cruciate ligament in 2-mm increments. Graft tension, the flexion angle, and anteroposterior laxity were recorded in a six-degrees-of-freedom load-application system that passively moved the knee from 0° to 120° of flexion.

Results: The graft tension at 120° of flexion was affected by the angle of the femoral tunnel and by incremental excision of the posterior cruciate ligament. The highest graft tension at 120° of flexion was 169 ± 9 N, which was detected with the graft in the 80° femoral and 80° tibial tunnels. The lowest graft tension at 120° of flexion was 76 ± 8 N, which was detected with the graft in the 60° femoral and 60° tibial tunnels. The graft tension of 76 N at 120° of flexion with the graft in the 60° femoral and 60° tibial tunnels was closer to the tension in the intact anterior cruciate ligament. Excision of the lateral edge of the posterior cruciate ligament in 2 and 4-mm increments significantly lowered the graft tension at 120° of flexion without changing the anteroposterior position of the tibia.

Conclusions: Placing the femoral tunnel at 60° in the coronal plane lowers graft tension in flexion. Our results suggest that high graft tension in flexion is caused by impingement of the graft against the posterior cruciate ligament, which results from placing the femoral tunnel medially at the apex of the notch in the coronal plane.

Clinical Relevance: For the surgeon who prefers the transtibial technique, the present study shows that controlling the angle of the tibial tunnel controls the angle of the femoral tunnel and the graft tension in flexion.

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    References

    Accreditation Statement
    These activities have been planned and implemented in accordance with the Essential Areas and policies of the Accreditation Council for Continuing Medical Education (ACCME) through the joint sponsorship of the American Academy of Orthopaedic Surgeons and The Journal of Bone and Joint Surgery, Inc. The American Academy of Orthopaedic Surgeons is accredited by the ACCME to provide continuing medical education for physicians.
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    Stephen M. Howell, M.D.
    Posted on November 24, 2003
    Dr. Howell responds to Dr. Arnold
    University of California

    > > > We appreciate your letter and your kind comments regarding our recent article.

    In the experiment we did not obtain radiographs of each femoral tunnel placement. We only obtained one AP and Lateral radiograph with the tibial guide wire in place BEFORE drilling any of the femoral tunnels. Hence we don't have any radiographic record of the femoral tunnel placement for any of the knees. > > >

    As you correctly stated in your letter,the position of the femoral tunnel is defined by the tibial tunnel. We would be interested in learning of a technique that we might use to retrospectively gather the information concerning the placement of the femoral tunnel so that we may fulfill your request.> > > Sincerely, > > > Stephen M. Howell, MD

    M.P. Arnold
    Posted on October 31, 2003
    Factors Influencing the Tension of Anterior Cruciate Ligament Grafts
    University Hospital, The Netherlands

    To the Editor:

    We read with great interest "Effect of the angle of the femoral and tibial tunnels in the coronal plane and incremental excision of the posterior cruciate ligament on tension of an anterior cruciate ligament graft: an in vitro study“ (2003;85:1018-29) by R. Simmons et al.

    We agree with the authors that the most important tunnel in the transtibial tunnel technique is the tibial tunnel. In their paper they clearly show that, once the tibial tunnel is drilled, the place of the femoral tunnel is defined. It is generally accepted that changes in the femoral tunnel position have a more important effect on graft forces than differences in tibial tunnel placement (1-6). In particular femoral tunnels placed too shallow along the Blumensaat’s line may lead to unfavourable high graft forces in flexion (2,4,7).

    In their Figure 9, the authors show that different angles of the tibial tunnel in the coronal plane lead to different insertional positions of the femoral graft. We would ask the authors to provide the data regarding the resulting femoral tunnel placements. In our opinion, these data are essential to more easily compare their findings to those of other papers that address tension in ACL grafts.

    Marco P. Arnold, MD Albert van Kampen, MD, PhD Department of Orthopaedic Surgery Department of Orthopaedic Surgery University Hospital UMC St. Radboud P.O. Box 30.001 Hanzeplein 1 Th. Craanenlaan 7 NL – 9700 RB Groningen 6700 HB Nijmegen The Netherlands Netherlands m.arnold@orth.azg.nl

    1. Amis AA, Beynnon B, Blankevoort L, Chambat P, Christel P, Durselen L, Friederich N, Grood E, Hertel P, Jakob R et al. Proceedings of the ESSKA scientific workshop on reconstruction of the anterior and posterior cruciate ligaments. Knee Surg Sports Traumatol Arthrosc. 1994;2:124-32.

    2. Amis AA, Jakob RP. Anterior cruciate ligament graft positioning, tensioning and twisting. Knee Surg Sports Traumatol Arthrosc. 1998;6:S2- S12.

    3. Bylski Austrow DI, Grood ES, Hefzy MS, Holden JP, Butler DL. Anterior cruciate ligament replacements: A mechanical study of femoral attachment location, flexion angle at tensioning, and initial tension. J Orthop Res. 1990;8:522-31.

    4. Friederich NF, O'Brien WR. Anterior cruciate ligament graft tensioning versus knee stability. Knee Surg Sports Traumatol Arthrosc. 1998;6:S38-42.

    5. Grontvedt T, Pena F, Engebretsen L. Accuracy of femoral tunnel placement and resulting graft force using one- or two-incision drill guides. A cadaver study on ten paired knees. Arthroscopy. 1996;12:187-92.

    6. Hefzy MS, Grood ES, Noyes FR. Factors affecting the region of most isometric femoral attachments. Part ii: The anterior cruciate ligament. Am J Sports Med. 1989;17:208-16.

    7. Müller W: The knee. Form, function and ligament reconstruction. Berlin, Heidelberg, New York: Springer; 1982.

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