The 2004 Annual Meeting (January 14-20, 2004) of OASYS_NEW

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Evaluation of a Tissue Engineered Material for Flexor Tendon Grafting in a Rabbit Model

Murphy KD1, Mushkudiani IA2, Kao DS2, Levesque AY3, Hawkins HK4, and Gould LJ2. (1) Department of Surgery/Division of Plastic Surgery, University of Texas Medical Branch & Shriners Hospitals for Children, Galveston, Room 718, Route #1220, 815 Market Street, Galveston, TX, USA, (2) Division of Plastic Surgery, University of Texas Medical Branch, Galveston, 6.124 McCullough Building, 301 University Blvd, Galveston, TX, USA, (3) School of Medicine/Division of Plastic Surgery, University of Texas Medical Branch, Galveston, 6.124 McCullough Building, 301 University Blvd, Galveston, TX, USA, (4) Department of Pathology, University of Texas Medical Branch & Shriners Hospitals for Children, Galveston, Room 349, 815 Market Street, Galveston, TX, USA

Introduction: The ideal tendon repair material would combine ready availability, minimal donor-site morbidity and operative time, with reliable healing and good postoperative function. A commercially available tissue-engineered product of porcine small-intestinal submucosa (SIS) might be a suitable human flexor tendon substitute. We compared flexor tendon grafting using SIS to tendon autografting in the rabbit flexor zone II equivalent.

Methods: A 1cm segment of the FDP tendon was excised from the Zone II forepaw middle digit in forty male New Zealand White rabbits. Rabbits were randomized to repair of the tendon deficit with either reversed autograft or SIS. Both materials were passed beneath the A2 and A4 pulleys. Forepaws were statically splinted in wrist and MCPJ flexion for three weeks followed by unrestricted motion. Animals were sacrificed at 7, 14, 28, and 56 days. Specimens were analyzed for hydroxyproline content and tensile strength. Haematoxylin/Eosin and Movat-stained sections of the central graft and distal repair site were semiquantitatively scored by a blinded pathologist for total cellularity, inflammatory cell content, foreign-body reaction, vascularity, elastin, mature collagen content and new collagen deposition.

Results: Net autograft collagen degradation reduced hydroxyproline content to 80% by two weeks. Collagen deposition in the SIS was evident microscopically by one week. Hydroxyproline content in the SIS was equivalent to autograft by two weeks. New collagen deposition was slower in autograft than SIS (Movat). Greater increases in total and inflammatory cellularity occurred more rapidly in SIS than in autograft during the initial four weeks. However, a foreign-body reaction did not occur until four weeks after surgery. Neovascularization of SIS occurred more quickly than autograft and is markedly greater at 1,2 and 4 weeks (p=0.076-week 2). Although hydroxyproline content remained less than autograft at four weeks, SIS had better intrinsic tensile strength (suture removed) at four weeks than either autograft or suture material (p=0.059). Tendon excursion was poor in both groups. TGF-b and TGF-b receptor staining will be discussed.

Conclusions: SIS is a very promising tissue-engineered material for flexor tendon grafting. Early neovascularization and autogenous collagen deposition offsets initial collagen degradation. SIS intrinsic repair strength exceeds that of both autograft and suture strength by four weeks. Inflammatory adhesions to SIS may not affect human subjects performing early active motion. Evaluation at eight weeks will determine whether a foreign body reaction to SIS impairs healing at eight weeks, and the feasibility of proceeding with tendon grafting with SIS in human subjects.


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