Residual osteochondral debris represents a clinical problem associated with arthroscopic debridement and curettage of joint surfaces. At the Oregon State University Veterinary Teaching Hospital (OSU-VTH), during a period from January, 1983 to August, 1986, incidence of radiographically recognizable osteochondral debris in the carpal joints of postarthroscopic equine patients was excessive. Uncertainty exists regarding the fate and effects of this debris on the normal equine joint. Reports in human medical literature implicate osteochondral debris as both an inflammatory stimulus and a mechanical abrasive in the pathogenesis of osteoarthrosis. This study was designed to evaluate the fate and effects of surgically implanted autogenous osteochondral fragments, intended to mimic remaining operative debris, on various physical and biochemical parameters of normal equine middle carpal joints over a six month time period. Four autogenous osteochondral fragments, removed from the lateral trochlear ridge of the talus, were arthroscopically placed as loose bodies into a randomly selected middle carpal joint in each of 10 young horses (2 to 4 years old). The contralateral middle carpal joint, subjected to a sham procedure, served as control. Postoperative therapy was consistent with usual treatment of clinical arthroscopic patients. Lameness evaluation, radiographic examination, carpal circumference measurement, and synovial fluid analysis were performed preoperatively and at scheduled intervals postoperatively. After two months of confinement, the horses were subjected to an increasing level of exercise, intended to mimic a four month conditioning program. Animals were euthanatized at 1 month (1), 2 months (2), 4 months (1), and 6 months (6). Gross and microscopic examination of remaining fragments, articular cartilage, and synovial membrane of each middle carpal joint was performed. Clinically, increased joint circumference, effusion, lameness, and radiographic appearance of degenerative joint disease distinguished implanted from control joints over the six month period. Implanted joints were grossly characterized by grooved, excoriated cartilage surfaces and synovium which was thickened, erythematous, and irregular. Loose bodies became adhered to synovium at their subchondral bone surface within four weeks after placement into the joint. At four weeks, bone within fragments was undergoing necrosis, while cartilage was preserved. At eight weeks, fragments were radiographically inapparent, grossly evident as pale plaques on the synovial surface, and composed of dense fibrous connective tissue. Histologically, synovial membrane specimens from implanted joints demonstrated significant (P < 0.05) inflammatory change two months after implantation. Mononuclear cells infiltrated the synovial layers. Significant physical damage (P < 0.05) was apparent within the articular cartilage two and six months after surgery. Chondrocyte degenerative change was significant (P < 0.05) six months after surgery. Generalized reduction in Safranin-O uptake was not apparent within each level of cartilage samples, but focal reduction in staining was readily apparent in cartilage layers adjacent to physical defects. Synovitis, physical articular damage, and focal chondrocyte degenerative change resulted from a combination of 1) direct mechnical abrasion by the implants or implant-derived debris, 2) an induced effect of osteochondral debris on the synovium, 3) synovitis-induced cartilage degeneration, and 4) supraphysiologic loading associated with exercise. In this study, osteochondral loose bodies of a defined size and shape were resorbed by the synovium within two months after joint implantation. These fragments directly and indirectly induced synovitis and significant articular cartilage degeneration. Methods to prevent and reduce residual postoperative debris and damage associated with its presence are discussed. Implementation of this methodology should reduce the potential for subsequent articular pathology. / Graduation date: 1991

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Call number: LD2668 .T4 1984 N97 / Master of Science