Experimental studies on half-joint transplantation. Antigenicity of fresh allografted articular cartilage and changes in the articular cartilage

The use of fresh-frozen bone in oral surgery: a clinical study of 14 consecutive cases

BACKGROUND

Although autologous bone is considered the gold standard among the grafting materials used in implant therapy, it does have a number of drawbacks, in particular morbidity at the site of donation and the limited amount of bone available. To overcome these limitations a number of alternative bone materials have been employed in the last few years. In this study we report the results of the use of homologous fresh-frozen bone from a tissue bank in patients undergoing reconstruction of bone defects in the oral cavity.

MATERIAL AND METHODS

Between June 2004 and October 2008, 14 consecutive patients underwent bone reconstruction with fresh-frozen bone from a tissue bank. Four to eight months after surgery, implants were placed in the newly formed bone.

RESULTS

No problems were recorded during the post-operative course. In all cases treatment was successful and osteointegrated implants were placed in the newly formed bone after 4-8 months. All implants showed good osteointegration (100% overall success rate, mean follow-up 20 months), allowing loading with a fixed cemented prosthesis.

CONCLUSIONS

Our results support the previous findings that homologous fresh-frozen bone can be considered a valid alternative to autologous bone for the reconstruction of bone defects in the oral cavity in patients undergoing implant therapy.

Analysis of cartilage tissue on a cellular level in fresh osteochondral allograft retrievals

BACKGROUND

Fresh human osteochondral allografting is a biological cartilage replacement technique used to treat articular and osteoarticular defects in the knee. A small number of grafts fail, and we analyzed every retrieved graft during a 4-year period in order to learn more about the potential causes of failure.

HYPOTHESIS

A large percentage of chondrocytes still remain viable many years after fresh osteochondral allografting.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Retrieval specimens were obtained at the time of revision surgery and immediately analyzed. Chondrocyte viability and viable cell density were determined using a live/dead staining technique followed by confocal microscopy. Glycosaminoglycan content was a measure of the cartilage matrix. Radiolabeled sulfate uptake served as a biochemical marker of chondrocyte metabolic activity. Cartilage and subchondral bone were examined histologically.

RESULTS

Fourteen patients yielded a total of 26 retrieval specimens that had been originally implanted as individual fresh osteochondral allografts. Average graft survival was 42 months. Chondrocyte viability was 82% +/- 17%, and chondrocyte viable cell density was 15 590 +/- 5900 viable cells/mm(3). Retrieved tissue demonstrated radiolabeled sulfate uptake of 437 +/- 270 counts per minute and 3.5% +/- 0.8% hexosamine per dry weight. Histologically, all specimens showed some degree of cartilage fibrillation. There was evidence of bone allograft incorporation in most specimens, as well as pannus formation in 4 specimens, but no evidence of immune rejection.

CONCLUSION

A small percentage of fresh osteochondral allografts fail, but the precise cause is unknown. The main theories for failure investigated here include immunologic rejection, failure of bony incorporation, and chondrocyte death causing breakdown of the cartilage matrix. We show that chondrocytes remain viable many years after transplantation, allograft bone incorporates, and immune rejection does not seem to play a primary role in failure.

CLINICAL RELEVANCE

Fresh osteochondral allografting is becoming more common in the treatment of articular cartilage defects in the knee. Our findings support the paradigm of fresh osteochondral allografting, the transplantation of hyaline cartilage with biological incorporation of the underlying bone scaffold. The reasons for failure of a small percentage of grafts remain unclear.

Human articular cartilage storage in cell culture medium: guidelines for storage of fresh osteochondral allografts

The viability of transplanted articular cartilage is one of the determinants of outcome following the transplantation of osteochondral allografts. Disappointing results from cryopreservation have led to the practice of fresh transplantation of articular segments, especially for posttraumatic defects. To date, no studies have demonstrated in vitro viability rates for refrigerated human cartilage awaiting transplantation. This study evaluates the effects of storage on the viability of human chondrocytes using cell culture medium. Human articular cartilage obtained from notchplasties was stored for up to 48 hours in cell culture medium. Radioactive 35S-sulfate uptake was determined at 0, 24, and 48 hours, as a measure of protein, synthesis, and chondrocyte viability. Specimens were stored at 4 degrees C in culture medium. Results showed an average decrease in 35S-sulfate uptake of 0.8% at 24 hours and 6.4% at 48 hours, indicating a high level of chondrocyte viability after refrigeration. Because transplantation typically is performed within 24 hours of tissue harvest, it appears that nearly 100% of chondrocytes should survive fresh transplantation.

Effect of tissue culture storage on the in vivo survival of canine osteochondral allografts

In vitro studies in our laboratory have shown that the biomechanical and biochemical characteristics of osteochondral grafts can be preserved for as long as 28 days under tissue culture conditions. This study represents an attempt to extend these results to an in vivo model. In adult mongrel dogs, either an autograft, a fresh allograft, or a stored allograft was placed in a standardized defect on the weight-bearing surface of the medial femoral condyle. The stored grafts were kept at 4 degrees C in tissue culture medium for 14 days prior to implantation. The animals were killed at 12 weeks. Cartilage from the contralateral knee served as a control. The modulus and permeability of the cartilage were assessed with confined compression creep tests. The collagen and glycosaminoglycan contents were measured, and the cartilage was analyzed histologically with hematoxylin and eosin and safranin O stains. Grossly, the cartilage appeared viable at harvest. The histologic results were similar in the treatment groups, with the same spectrum of mild degenerative changes being noted in each group. The glycosaminoglycan content was significantly less in the autograft group than in its control group and than in the fresh allograft group. The glycosaminoglycan content did not differ significantly between fresh and stored allografts. The collagen content, modulus, and permeability did not differ either between experimental and control groups or between graft types. Our results support the conclusion that osteochondral allografts can be stored for as many as 14 days without significantly affecting the results of the procedure.