Transplantation of vitrified osteochondral allografts revealed equivalent cartilage repair to fresh osteochondral allografts in a swine model

Despite improvements in treatment options and techniques, articular cartilage (AC) repair continues to be a challenge for orthopedic surgeons. The use of osteochondral allografts for AC repair is currently limited by the availability and short shelf life of donor cartilage. AC vitrification-which is an ice-free cryopreservation technology-will increase the availability of viable graft tissue for large joint defects. Although different protocols have been developed for AC vitrification, it is still unknown if vitrified and fresh osteochondral grafts are equivalent in terms of long-term joint resurfacing efficacy. In the present study, we compared the ability of vitrified porcine osteochondral dowels to repair full thickness cartilage defects to that of fresh porcine osteochondral dowels kept for 21 days at 4 °C. Eighteen pigs were randomly assigned to three experimental groups according to the kind of osteochondral dowel they received transplanted to medial femoral condyles: Long-Term Vitrified osteochondral dowel group (n = 6), Short-Term Vitrified osteochondral dowel group (n = 6), and Fresh osteochondral dowel group (n = 6). Lameness score was evaluated before and after transplantation surgery. Animals were euthanized 6 months after transplantation to obtain medial femoral condyles, and the contralateral condyle was used as the positive (no defect) control. Samples were evaluated for macroscopic appearance, morphometric-microstructural measures of bone, chondrocyte density, proteoglycan distribution, and repair tissue quality. The overall repair quality in all grafts (including fresh controls) was incomplete likely due to the animal model and surgical technique. In the areas where repair was documented, this study demonstrated that the repair effect of vitrified transplanted dowels (both Long-Term and Short-Term) was equivalent to that of the Fresh dowels that were stored for 21 days at 4 °C when comparing lameness scores, quality of regenerated cartilage based on direct visualization of the gross appearance (ICRS Scores), chondrocyte density, proteoglycan distribution within the extracellular matrix, morphometric measures of bone quantity and microstructural quality, and microscopic histological characteristics of the repair tissue. The vitrification of osteochondral dowels will mitigate the short shelf life of commonly used fresh osteochondral transplants, significantly increasing their availability for use by physicians and patients.