0
Articles   |    
Biomechanical Consequences of Replacement of the Anterior Cruciate Ligament with a Patellar Ligament Allograft. Part I: Insertion of the Graft and Anterior-Posterior Testing*
KEITH L. MARKOLF, PH.D.†; DANIEL M. BURCHFIELD, M.D., PH.D.†; MATTHEW M. SHAPIRO, M.D.†; BRENT R. DAVIS, M.D.†; GERALD A. M. FINERMAN, M.D.†; JAMES L. SLAUTERBECK, M.D.†, LOS ANGELES, CALIFORNIA
View Disclosures and Other Information
Investigation performed at the Department of Orthopaedic Surgery, Biomechanics Research Section, University of California at Los Angeles, Los Angeles.
J Bone Joint Surg Am, 1996 Nov 01;78(11):1720-7
5 Recommendations (Recommend) | 3 Comments | Saved by 3 Users Save Case

Abstract

Nineteen fresh-frozen knee specimens from cadavera were tested for anterior-posterior laxity with 200 newtons of force applied to the tibia. A cylindrical cap of subchondral bone containing the tibial insertion of the anterior cruciate ligament was isolated with a coring cutter and was potted in acrylic. A thin wire was connected to the undersurface of the cap, and relative displacement between the cap and the tibia was measured with an isometer as the knee was extended. The cap of bone was connected to a load-cell that recorded force in the intact ligament during anterior-posterior testing with the tibia locked in neutral, internal rotation, and external rotation. The anterior cruciate ligament was then resected, and a femoral tunnel was drilled at the site where the isometer readings from the wire were the same as those obtained for the intact anterior cruciate ligament. A bone-patellar ligament-bone graft was used to reconstruct the anterior cruciate ligament, and the isometer measurements were repeated with the graft in place. The graft was pre-tensioned at 30 degrees of flexion to restore normal anterior-posterior laxity. Anterior-posterior laxity tests were repeated at this level of pre-tension (laxity-matched pre-tension) as well as at a level that was forty-five newtons greater (over-tension). The moment required to extend the knee was measured before and after insertion of the graft at both levels of pre-tension.When the tibia was locked in positions of internal and external rotation, the anterior-posterior laxities and the forces in the anterior cruciate ligament (generated by an anterior force applied to the tibia) were significantly less than the corresponding values with the tibia in neutral rotation at 20, 30, and 45 degrees of flexion (p = 0.05). Isometer readings for the intact anterior cruciate ligament indicated that the cap of bone retracted into the joint a mean and standard deviation of 3.1 ± 0.8 millimeters as the knee was extended from 30 degrees of flexion to full extension. For each specimen, the isometer measurements for the trial wire and for the graft were within 1.5 millimeters of those for the intact anterior cruciate ligament. At laxity-matched pre-tension (mean, 28.2 ± 16.8 newtons), the mean anterior-posterior laxities of the reconstructed knees were within 1.0 millimeter of the corresponding means for the intact knees between 0 and 45 degrees of flexion. Over-tensioning of the graft by forty-five newtons decreased the anterior-posterior laxity a mean of 1.2 millimeters at 30 degrees of flexion. Over-tensioning of the graft did not change the moment required to bring the knee to full extension.CLINICAL RELEVANCE: When performing an anterior laxity test with the knee flexed 20 to 30 degrees, the examiner should place the tibia in a position of neutral rotation, as this is the position of greatest laxity at which all anterior force applied to the tibia will be resisted by the anterior cruciate ligament. It is important to recognize that the intact anterior cruciate ligament does not behave in a so-called isometric fashion. Approximately three millimeters of retraction of a trial wire into the joint during the last 30 degrees of extension (as measured with an isometer) is reasonable in order to achieve changes in the length of the graft that approximate those of the intact anterior cruciate ligament.

Figures in this Article
    Sign In to Your Personal ProfileSign In To Access Full Content
    Not a Subscriber?
    Get online access for 30 days for $35
    New to JBJS?
    Sign up for a full subscription to both the print and online editions
    Register for a FREE limited account to get full access to all CME activities, to comment on public articles, or to sign up for alerts.
    Register for a FREE limited account to get full access to all CME activities
    Have a subscription to the print edition?
    Current subscribers to The Journal of Bone & Joint Surgery in either the print or quarterly DVD formats receive free online access to JBJS.org.
    Forgot your password?
    Enter your username and email address. We'll send you a reminder to the email address on record.

     
    Forgot your username or need assistance? Please contact customer service at subs@jbjs.org. If your access is provided
    by your institution, please contact you librarian or administrator for username and password information. Institutional
    administrators, to reset your institution's master username or password, please contact subs@jbjs.org

    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.
    CME Activities Associated with This Article
    Submit a Comment
    Please read the other comments before you post yours. Contributors must reveal any conflict of interest.
    Comments are moderated and will appear on the site at the discretion of JBJS editorial staff.

    * = Required Field
    (if multiple authors, separate names by comma)
    Example: John Doe





    Related Content
    The Journal of Bone & Joint Surgery
    JBJS Case Connector
    Topic Collections
    Related Audio and Videos
    PubMed Articles
    Clinical Trials
    Readers of This Also Read...
    JBJS Jobs
    04/16/2014
    Georgia - Choice Care Occupational Medicine & Orthopaedics
    01/08/2014
    Pennsylvania - Penn State Milton S. Hershey Medical Center
    04/16/2014
    Ohio - OhioHealth Research and Innovation Institute (OHRI)