| Objective: We performed this study to determine whether intact cartilage would survive cryopreservation, and compare the reparative effects of two groups of cryopreserved osteochondral allografts with different procedures.Methods: Thirty three to four months aged New Zealand rabbit have been used. Accroding their weights, the six smallest be employed as donaters, the rest were divided into experimental group and control group at random.Under a general anesthesia and with use of aseptic techniques, either the left or the right knees of the donaters were exposed by a medial parapatellar arthrotomy. Both condyles of the femur and the intercondylar groove were exposed and plugs were harvested from the weight-bearing surface. Their dimensions was 33 mm and 4mm of thickness, including some subchondral bone. These plugs, taken at random from either condyle, were also divided into experimental group and control group.During the operation, Hank's balanced salt solution(HBSS) was sprayed on the surface of the cartilage to keepthem wet. With a pin, nine drills were made on the surface ofeach graft in experimental group. Among the drills, three in lines and three in rows, each distance between them is equal. The allografts were immersed in 10% dimethylsulfoxide( DMSO) for 2.5 hours, then transfered into a programmable freezing chamber. The cryopreservationwas performed with a rate of 0.5 from 4 to -35. and maintained for 15 mintues, then at a rate of 1 /min to -75, for 20 minutes. Subsequently, all the groups were stored in liquid nitrogen for more than 96 hours. After a fresh defect was created on the receiptor's medial condyle, an allograft was taken out of liquid nitrogen by group and quickly thawed in warm water bath at 37 for two or three minutes, then washed in BBSS for three times and implanted properly. Graft fixation was limited to press-fitting and no postoperative immobilization was used, and animal activity was restricted only by the cage dimension.Half grafts were harvested at four weeks and eight weeks postoperation respectively. Immediately after the sacrifice of the animals, the knee joint was exposed and the distal femur with the graft in it photographed. Joint appearance and macroscopic observations of the femoral condyles, such as colour, glistening, irregularities, or osteophytes, was recorded. A minor part from the graft was taken for amino acid analysis. Additionly, the femoral head and meniscs were removed from the opposite lower limber, as specimen of hyaline cartilage and fibrou cartilagerespectively. The aboving samples for amino acid analysis were stored in condition of -20, while the remaining graft and its surrounding osteochondral tissue were fixed with 10% formalin more than 24 hours. Fixed femurs were cut with an oscillating saw, and specimen were decalcified and, after the usual dehydration and paraffin embedding, sectioned at 5 |im on a rotary microtome. Sections were stained with hematoxylin and eosin. We chose Shapiro and Glimcher's quantitative scoring scale, which also includes macroscopic data and was designed to evaluate changes after meniscectomy in the rabbit.The cartilage slices taken from the cartilage of the both groups were dried and weighted, then dydrolyzed adequately, which permitted the quantitation of hydroxyproline and hydroxylysine using an amino acid analyzer. The hydroxylysine/hydroxyproline (HYL/HYP) ratio, used to detemine the collagen type, was obtained by dividing the the quantity of hydroxylysine by the quantity of hydroxyproline present in each sample.A statistical analysis of results has been made using the nonparametric Wilcoxon test, while that of amino acide analysis using ANOVA and Nowman Keuls test.Results: At four weeks postoperation, the knee functions of most animals were fairly well, seldom with complications such as adherent, osteophytes and so on. The surface of grafts were smooth and shining, indistinguishable from theirsurroundings. Another four weeks later, the appearance of grafts remained normal grossly, b...
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