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Abstract Presented at the 26th Annual Meeting of the Arthroscopy Association of North America| Volume 23, ISSUE 6, SUPPLEMENT , e23-e24, June 2007

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Clinical and Microscopic Evaluation of Implanted Refrigerated and Frozen Osteochondral Allografts (SS-46)

      Summary

      The purpose of the current study was to evaluate patients who underwent refrigerated or frozen allograft transplantation No significant difference in chondrocyte viability was noted on histological or electron microscopy analysis between refrigerated and frozen allografts at the time of implantation. A trend towards greater improvement in WOMAC, KSS was noted in the frozen allograft group when compared to the refrigerated allograft group. Both refrigerated and frozen large osteochondral allografts appear to be function well clinically at 4 year follow-up.

      Purpose

      Treatment options for full thickness osteochondral lesions include microfracture, transplanting cultivated autologous chondrocytes, or osteochondral tissue. The use of fresh osteochondral allografts has been well documented, with “fresh” indicating graft harvest within 24 hours of the donor’s death and time to implantation of < 7 days. Deep frozen allografts have also been used; however, diminished cell viability and matrix degeneration have been cited. The purpose of the current study was to clinically and radiographically evaluate patients who underwent refrigerated or frozen allograft transplantation and analyze the relationship between functional outcome and allograft histological and electron microscopic grading.

      Methods

      Between 1998 and 2002, 58 patients underwent transplantation for a cartilage defect of the femur and/or patella with a refrigerated or frozen allograft. Inclusion criteria were as follows: activity level of Tegner 3 or greater, a contained articular cartilage defect; damage limited to < 2 compartments, failure of conservative measures > 3 months. All patients underwent clinical evaluation including the Knee Society Score (KSS), WOMAC Score and a VAS for pain. Failure was defined as conversion to a unicondylar/total knee arthroplasty. All failures were included in the overall analysis and also analyzed separately. Three plugs were sterilely harvested and prepared for evaluation. The following scoring system was utilized for each slide: 0 = all cells lethally injured; 1+ = majority of cells with marked-lethal injury; 2+ = minority of cells with marked-lethal injury; 3+ all cells viable. For electron microscopy the above scoring scheme above was also applied. Statistical analyses were performed using JMP software system. Significance was determined at the 0.05 level.

      Results

      Among the 26 patients, analysis were available in 25 (96%). There were 11 males and 15 females. The average age was 48 years. The average follow-up was 46 months. The average BMI was 32. The average graft size was 4.5 cm2. The 4 scores for histological and electron microscopy evaluation were combined into 2 grades. When pre-operative WOMAC and KSS were compared, there was no statistical difference between the 2 groups. No significant difference in chondrocyte viability was noted on histological or electron microscopy between refrigerated and frozen allografts at the time of implantation. A trend towards greater improvement in WOMAC, KSS was noted in the frozen allograft group, although not statistically significant (p=0.07) An improvement in knee range of motion was noted in frozen allograft patients compared to those with a refrigerated allograft (p=0.02). There was no correlation between post-op x-ray score and outcome. 24% were considered failures and were analyzed separately. All failures were refrigerated allografts. No failures were noted if the histology score was Grade 2 or if the electron microscopy score was Grade 2. The likelihood ratio for a patient to do well if the initial histological score was 2 was 8.4 and if the electron microscopy score was 2 was 1.4.

      Conclusions

      Both refrigerated and frozen large osteochondral allografts appear to be function well clinically at 4 year follow-up. Long term follow-up is further needed.