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Document Title: Kitamura-AJARS-Aug05.shtml
Article Title: Primary Stability of Three Posterior Cruciate Ligament Reconstruction Procedures: A Biomechanical In Vitro Study
Authors: Nobuto Kitamura, Kazunori Yasuda, Harukazu Tohyama M.D., Ph.D., Masanori Yamanaka R.P.T., Ph.D. and Yoshie Tanabe R.P.T., M.S.
Publication: Arthroscopy: The Journal of Arthroscopic & Related Surgery
Date: August 2005
Volume 21, Issue 8, August 2005, Pages 970-978
Keywords: Posterior cruciate ligament, PCL reconstruction, graft-fixation methods, strength, durability, flexor-tendon graft, biomechanics, cyclic loading test.
(Reference-denoting numbers appear in the same font and point size as the document text. As with all Knee Library documents, this article is provided in full-text form, complete with all figures and tables.)
Comments: This lab-type study looks at the primary (i.e. as-installed, with no rehabilitation yet) three different methods of PCL reconstruction. To simulate the cyclical loadings typical of the human knee, and to address the long-standing concern about fatigue-related failure, they carried out tensile testing to 5000 cycles. They found that, just like in ACL reconstruction, the PCL-graft fixation method used is important in terms of strength and fatigue resistance. One attribute that is challenging to test in a laboratory is the propensity of each graft-fixation method to the "bungee-cord effect". And, given the overarching importance of this phenomenon, it would have been nice if the authors would have delved into this in detail. This effect occurs when the graft is fixed only at the ends furthest from the knee-joint line, since it means that the body of the graft inside the bone tunnel is left free to slide with respect to the tunnel walls (and given that all grafts have natural elasticity), thus inhibiting healing and incorporation. Two graft-fixation techniques which tend to be prone to the bungee-cord effect are the Endobutton (used with some sort of tape, such as the Leeds-Keio polyester tape which saw use in this study) and the post-screw. These two methods, not surprisingly, did not bring stellar results in the biomechanical testing. The safest bet is to use the well-proven interference screw and the bone-patellar-tendon-bone graft, a method which brings the overwhelmingly valuable security of bone-to-bone healing. And, traditional interference-screw fixation avoids the bungee-cord worries of the post-screw, the Endobutton, and the polyester tape. Staples, if used to help fix the graft inside the bone tunnels (i.e. not just at the end furthest from the joint), are also a viable option, but on their own they are not able to snugly anchor the graft along its entire length inside the tunnel. Only interference screws can do this.
Abstract
Purpose: Posterior cruciate ligament (PCL) reconstruction procedures have not been thoroughly evaluated under cyclic loading conditions. We tested the hypothesis that PCL reconstruction with a quadrupled flexor-tendon graft and fixation using tapes and staples is biomechanically superior to that fixed with sutures, a button, and a post-screw, and is comparable to reconstruction with a bone—patellar tendon—bone (BPTB) graft.
Study Design: In vitro biomechanical study.
Methods: A total of 45 porcine knees were used. The quadrupled flexor-tendon graft was fixed using the suture/button/post-screw procedure in 15 knees, and with the tape/staples procedure in another 15 knees. The remaining 15 knees underwent reconstruction with a BPTB graft secured with screws as the standard control. In each group of 15 knees, 5 underwent tensile testing without cyclic loading, and 10 underwent the same tensile test after 5,000 cycles of load-controlled or displacement-controlled loading.
Results: Each type of cyclic loading produced larger biomechanical changes in the knees fixed with the suture/button/post-screw procedure than in the knees secured using the other 2 procedures.
Conclusions: In PCL reconstruction, the tape/staples procedure is biomechanically superior to the suture/button/post-screw procedure, and is comparable to the BPTB/screws procedure with regard to the ultimate failure load. Neither of the procedures using the quadrupled flexor-tendon graft was comparable to the BPTB graft in linear stiffness and the initial displacement after load-controlled cyclic testing.
Clinical Relevance: The biomechanical behaviors of PCL-reconstructed knees are significantly different, depending on surgical techniques.
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Copyright Arthroscopy: The Journal of Arthroscopic & Related Surgery, Arthroscopy Association of North America, Published by Elsevier of Holland, August 2005. For details regarding copyright as it applies to this page, please visit the page entitled Site Terms of Use and Aspects of Copyright on this site.
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