Chondrocyte-collagen composites were evaluated for resurfacing of large articular defects. Isolated chondrocytes were cultured in expanded collagen scaffolds for 7-10 days to provide a composite containing 3.6 x 10(4) cells/mm3. The graft was transplanted into 15 mm full thickness articular defects in the femoropatellar joint of 12 horses using arthroscopic techniques. Ungrafted defects in the opposite femoropatellar joint served as controls. Synovial fluid, clinical progress and pain responses were evaluated in groups of 6 horses over 4-month and 8-month periods. Following termination, gross, histochemical and histologic evaluations of the repair tissues and synovial membrane were performed. Arthroscopic defect debridement and chondrocyte implantation resulted in minimal post-operative effusion or pain, and synovial fluid constituents were not significantly different in grafted and ungrafted joints. Gross differences in grafted defects were not apparent. Increased chondrocyte numbers and cartilage histochemical staining were evident in the deeper layers of grafted defects, whereas ungrafted defects were almost entirely fibrous tissue. The surface layers of grafted defects were fibrous tissue. There were no synovial fluid cellular responses, synovial membrane histiocytic reaction or subchondral bone infiltrates to suggest immune-related reaction to the allograft cells. Chondrocyte-collagen grafts were arthroscopically implanted and resulted in improved cartilage healing in extensive defects. However, the structural organization of the surface layers was inadequate and suggested poor long-term durability.

An endoscopically assisted technique for internally dividing the palmar or plantar annular ligament was developed in six cadaver limb specimens and two anesthetized horses. Under arthroscopic view, a slotted cannula was inserted into the digital sheath through a stab wound proximal to the annular ligament and advanced through the fetlock canal superficial to the flexor tendons with the slot oriented toward the fibers of the annular ligament. Division of the annular ligament by 90-degree tipped open and guarded blades was observed and verified by direct arthroscopic view. At necropsy, complete division of the annular ligament without iatrogenic damage to the neurovascular structures was confirmed by dissection. Annular ligament division was performed in seven horses with complex tenosynovitis conditions. Tenoscopic examination and removal of tendon and digital sheath adhesions, masses, and bands was followed by endoscopically assisted annular ligament transection. At follow-up, five horses were sound athletes without recurrent digital sheath problems, one horse had residual lameness, and one horse was still convalescing.

Chondrocyte-laden collagen scaffolds were evaluated in extensive cartilage defects in an equine model. Arthroscopic techniques were used to implant a chondrocyte-collagen culture product in 15-mm defects in the lateral trochlear ridge of the femoropatellar joint of 12 horses. Ungrafted control defects were formed in the opposite joint. Groups of six horses were terminated at 4 and 8 months after implantation and the repair sites, adjacent cartilage, and remote cartilage within each femoropatellar joint examined biochemically. Eight months following surgery the relative proportions of type II collagen in grafted and ungrafted defects, determined using the ratio of cyanogen bromide cleavage products alpha 1(II)CB10/alpha 2(I)CB3,5, were not significantly different (31.57 +/- 2.76% and 26.88 +/- 2.76%, respectively). Aggrecan content was significantly improved in grafted defects (85.61 +/- 6.51 and 74.91 +/- 10.31 micrograms/mg dry weight). Cartilage surrounding grafted defects also showed improved maintenance of cartilage glycosaminoglycan content. Thus, chondrocyte grafting in collagen scaffold vehicles improved the aggrecan content in extensive cartilage defects and surrounding normal cartilage. However, given the continued disparity between repair tissue and normal cartilage aggrecan content, and the low proportion of type II collagen in grafted defects, the utility of collagen scaffolds for chondrocyte grafting of large cartilage defects seems limited.