The article by Williams et al. addresses an extremely important issue related to cartilage-repair technology. Various surgical modalities to address cartilage defects and/or cartilage-bone defects, particularly in the knee, have now become part of the armamentarium for orthopaedic surgeons, particularly those involved in sports medicine. Osteochondral allografts are commonly used for larger defects that are not amenable to surface treatments (e.g., microfracture, autologous chondrocyte transplantation, and mosaicplasty). This paper therefore plays an important role not only by discussing the use of osteochondral allografts for posttraumatic defects but also by addressing the issue of fresh tissue versus preserved tissue.
At the present time, tissue banks in North America have to wait approximately thirty days before tissue can be delivered because of the necessary testing that is performed to exclude viral as well as bacterial contamination. Prior to the establishment of tissue banks, only a few centers with comprehensive transplant programs were able to access fresh tissues for transplantation. Long-term studies at these institutions have revealed that fresh tissue, because of chondrocyte viability and maintenance of the matrix, has advantages over cryopreserved tissue. Although cryopreserved cartilage can remain structurally intact for many years, analysis of retrieval specimens has revealed no evidence of the presence of viable chondrocytes1. On the other hand, retrieval specimens of fresh osteochondral allografts have been shown to contain viable chondrocytes and a healthier cartilage as a result of maintenance of the matrix2,3. In longer-term studies, the survivorship of fresh osteochondral allografts was 85% at ten years4,5. These results have encouraged orthopaedic surgeons who perform cartilage repair procedures to pursue the use of fresh tissue rather than cryopreserved tissue4,5. Chondrocyte viability decreases significantly (p < 0.001) after two weeks of preservation, and therefore, ideally, tissue banks should aim for graft delivery by two weeks or less6.
The authors have presented results of a small series of patients who had a relatively short period of clinical follow-up (mean, forty-eight months) and magnetic resonance imaging follow-up (mean, twenty-five months). Despite this weakness of the study, I think that this is a very important paper because it examines the issue of fresh tissue versus preserved tissue and, even more importantly, because it has established excellent protocols—both clinical and radiographic—to evaluate the results of cartilage transplantation.
In their study, the authors transplanted tissue that had been stored for an average of thirty days and then compared their results with those from studies in which transplanted tissue had been stored for seven days or less. Four of the nineteen patients in the series underwent additional surgery during the average follow-up time of forty-eight months. In one patient, the graft had to be repositioned, and in two patients, collapse and fragmentation of the first graft necessitated revision osteochondral allograft transplantation. A fourth patient underwent a total knee arthroplasty two years following the transplantation. The reoperation rate was high but, in my opinion, acceptable, considering that it was early in the authors' experience with fresh tissue. It should also be understood that this trephine technique is relatively new technology and has only been available for about five years.
In my experience with the use of fresh tissue, I have found it necessary to do realignment osteotomies in approximately 60% of our patients. The authors only did two realignment osteotomies in this series of nineteen patients, and I would have expected the prevalence to be higher. In my series, even if the patient had a deformity that was very minimal, I performed realignment osteotomy so that the graft would not be placed in a compartment that was overloaded. I would like to respectfully suggest that the authors perhaps could have improved their results by being somewhat more aggressive about the use of osteotomy in conjunction with the placing of these grafts. The two grafts in their series that failed because of collapse and fragmentation might have benefited by an osteotomy done at the same time as the transplant.
The authors should be complimented for their use of magnetic resonance imaging to evaluate the status of these grafts. The cartilage-sensitive magnetic resonance imaging technology available to this group is the best in the world and is an extremely important part of this paper. It is being adopted by many other centers. Their finding of a correlation of the clinical result with the osseous integration of the graft is extremely important. It has been my opinion that the fate of the osseous part of the graft is even more important than that of the cartilage because if the bone resorbs or fractures before the osseous part is integrated, then the cartilage will surely fail. Also, collapse of the osseous part of the graft leads to incongruity on the joint surface. Thus, for the cartilage to remain structurally intact, the bone obviously must remain structurally intact, and, for that to happen, the bone has to be integrated in a uniform fashion. The authors have demonstrated this very well with their magnetic resonance imaging studies. They concluded that the results of magnetic resonance imaging can be used to assess allograft appearance following implantation and may be an effective tool for predicting outcome. The authors have established magnetic resonance imaging criteria that are extremely important for any clinical research related to cartilage transplantation.
In summary, I think that this article is an important one, even though it reports on a small series with a relatively short period of follow-up. The authors have established objective clinical and radiographic parameters to evaluate osteochondral allografts, and they have discussed the issues related to the use of fresh versus cryopreserved tissue. I look forward to future publications from this institution in the future.
*The author did not receive any outside funding or grants in support of his research for or preparation of this work. Neither he nor a member of his immediate family received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, division, center, clinical practice, or other charitable or nonprofit organization with which the author, or a member of his immediate family, is affiliated or associated.
1. Enneking WF, Mindell ER. Observations on massive retrieved human allografts. J Bone Joint Surg Am. 1991;73:1123-42.
2. Oakeshott RD, Farine I, Pritzker KP, Langer F, Gross AE. A clinical and histologic analysis of failed fresh osteochondral allografts. Clin Orthop Relat Res. 1988;233:283-94.
3. McGoveran BM, Pritzker KP, Shasha N, Price J, Gross AE. Long-term chondrocyte viability in a fresh osteochondral allograft. J Knee Surg. 2002;15:97-100.
4. Aubin PP, Cheah HK, Davis AM, Gross AE. Long-term followup of fresh femoral osteochondral allografts for posttraumatic knee defects. Clin Orthop Relat Res. 2001;391 Suppl:S318-27.
5. Gross AE, Shasha N, Aubin P. Long-term followup of the use of fresh osteochondral allografts for posttraumatic knee defects. Clin Orthop Relat Res. 2005:435:79-87.
6. Williams SK, Amiel D, Ball ST, Allen RT, Wong VW, Chen AC, Sah RL, Bugbee WD. Prolonged storage effects on the articular cartilage of fresh human osteochondral allografts. J Bone Joint Surg Am. 2003;85:2111-20.