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Research Papers

Effect of Implanting a Soft Tissue Autograft in a Central-Third Patellar Tendon Defect: Biomechanical and Histological Comparisons

[+] Author and Article Information
Kirsten R. C. Kinneberg1

 University of Cincinnati, School of Energy, Environmental, Biological and Medical Engineering, Biomedical Engineering Program, 2901 Woodside Drive, 601 Engineering Research Center, Cincinnati, OH 45220Kirsten.kinneberg@gmail.com

Marc T. Galloway

 Cincinnati SportsMedicine & Orthopaedic Center, 7423 Mason-Montgomery Rd., Mason, OH 45040-8082mgalloway@csmoc.com

David L. Butler

Jason T. Shearn

 University of Cincinnati, School of Energy, Environmental, Biological and Medical Engineering, Biomedical Engineering Program, 2901 Woodside Drive, 601 Engineering Research Center, ML0048, Cincinnati, OH 45220jason.shearn@uc.edu

1

Corresponding author.

J Biomech Eng 133(9), 091002 (Oct 04, 2011) (6 pages) doi:10.1115/1.4004948 History: Received June 21, 2011; Accepted August 23, 2011; Published October 04, 2011; Online October 04, 2011

Previous studies by our laboratory have demonstrated that implanting a stiffer tissue engineered construct at surgery is positively correlated with repair tissue stiffness at 12 weeks. The objective of this study was to test this correlation by implanting a construct that matches normal tissue biomechanical properties. To do this, we utilized a soft tissue patellar tendon autograft to repair a central-third patellar tendon defect. Patellar tendon autograft repairs were contrasted against an unfilled defect repaired by natural healing (NH). We hypothesized that after 12 weeks, patellar tendon autograft repairs would have biomechanical properties superior to NH. Bilateral defects were established in the central-third patellar tendon of skeletally mature (one year old), female New Zealand White rabbits (n = 10). In one limb, the excised tissue, the patellar tendon autograft, was sutured into the defect site. In the contralateral limb, the defect was left empty (natural healing). After 12 weeks of recovery, the animals were euthanized and their limbs were dedicated to biomechanical (n = 7) or histological (n = 3) evaluations. Only stiffness was improved by treatment with patellar tendon autograft relative to natural healing (p = 0.009). Additionally, neither the patellar tendon autograft nor natural healing repairs regenerated a normal zonal insertion site between the tendon and bone. Immunohistochemical staining for collagen type II demonstrated that fibrocartilage-like tissue was regenerated at the tendon-bone interface for both repairs. However, the tissue was disorganized. Insufficient tissue integration at the tendon-to-bone junction led to repair tissue failure at the insertion site during testing. It is important to re-establish the tendon-to-bone insertion site because it provides joint stability and enables force transmission from muscle to tendon and subsequent loading of the tendon. Without loading, tendon mechanical properties deteriorate. Future studies by our laboratory will investigate potential strategies to improve patellar tendon autograft integration into bone using this model.

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Copyright © 2011 by American Society of Mechanical Engineers
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Figures

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Figure 1

Force-displacement curves (mean ± SEM). PTA (n = 6) and NH (n = 6) repairs both exceeded the peak in vivo force required for activities of daily living (100 N; in vivo force and displacement, IVF and IVD, respectively) [(29),30]. However, PTA and NH repairs do not match the normal central-third PT (Normal; n = 8 [(17),18]) or TEC (n = 7 [18]) repair curves. Portions of this figure re-printed with permission from Juncosa-Melvin, (2006) [18].

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Figure 2

H&E staining and IHC staining for collagen type III (Col3) of the tendon mid-substance for both NH and PTA after 12 weeks of healing. Col3 (brown) is primarily localized to the central-third repairs tissue (R) for natural healing (NH) samples and localized to the graft-native strut (NS) interface for PTA samples. Neo-vascularization is visible in the native struts (NS) and central-third repair (R) regions for both tissues (the central-third repair is labeled as R for both NH and PTA samples). Scale bar = 200 μm.

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Figure 3

Histological images of patellar and tibial tendon-to-bone insertion sites. Insertion site images are shown with H&E staining and immunohistochemical staining for type II collagen (Col2). After 12 weeks of healing, proper insertion sites were not regenerated by PTA or NH. The insertion sites in the native struts (NS) appear unaffected by the surgical procedure. H&E images are labeled to reflect: B, bone; T, tendon; FS, fibrous scar; MFC/FC, mineralized fibrocartilage/fibrocartilage zones of the insertion site, respectively (note: these zones are not as distinct in the patella as they are in the tibia); areas resembling neo-vascularization are marked with an asterisk. Scale bar = 200 μm.

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