Chondrocyte viability in refrigerated osteochondral allografts used for transplantation within the knee

Beneficial storage effects of epigallocatechin-3-o-gallate on the articular cartilage of rabbit osteochondral allografts

A fresh osteochondral allograft is one of the most effective treatments for cartilage defects of the knee. Despite the clinical success, fresh osteochondral allografts have great limitations in relation to the short storage time that cartilage tissues can be well-preserved. Fresh osteochondral grafts are generally stored in culture medium at 4 degrees C. While the viability of articular cartilage stored in culture medium is significantly diminished within 1 week, appropriate serology testing to minimize the chances for the disease transmission requires a minimum of 2 weeks. (-)-Epigallocatechin-3-O-gallate (EGCG) has differential effects on the proliferation of cancer and normal cells, thus a cytotoxic effect on various cancer cells, but a cytopreservative effect on normal cells. Therefore, a storage solution containing EGCG might extend the storage duration of articular cartilages. Rabbit osteochondral allografts were performed with osteochondral grafts stored at 4 degrees C in culture medium containing EGCG for 2 weeks and then the clinical effects were examined with macroscopic and histological assessment after 4 weeks. The cartilaginous structure of an osteochondral graft stored with EGCG was well-preserved with high cell viability and glycosaminoglycan (GAG) content of the extracellular matrix (ECM). After an osteochondral allograft, the implanted osteochondral grafts stored with EGCG also provided a significantly better retention of the articular cartilage with viability and metabolic activity. These data suggest that EGCG can be an effective storage agent that allows long-term preservation of articular cartilage under cold storage conditions.

Osteochondral integration of multiply incised pure cartilage allograft: repair method of focal chondral defects in a porcine model

BACKGROUND

A focal cartilage lesion has limited capacity to heal, and the repair modalities used at present are still unable to provide a universal solution. Pure cartilage graft implantation appears to be a simple option, but it has not been applied widely as cartilage will not reattach easily to the subchondral bone.

HYPOTHESIS

We used a multiple-incision technique (processed chondrograft) to increase cartilage graft surface. We hypothesized that pure cartilage graft with augmented osteochondral fusion capacity may be used for cartilage repair and we compared this method with other repair techniques.

STUDY DESIGN

Controlled laboratory study.

METHODS

Full-thickness focal cartilage defects were created on the medial femoral condyle of 9-month-old pigs; defects were repaired using various methods including bone marrow stimulation, autologous chondrocyte implantation, and processed chondrograft. After the repair, at weeks 6 and 24, macroscopic and histologic evaluation was carried out.

RESULTS

Compared with other methods, processed chondrograft was found to be similarly effective in cartilage repair. Defects without repair and defects treated with bone marrow stimulation appeared slightly irregular with fibrocartilage filling. Autologous chondrocyte implantation produced hyalinelike cartilage, although its cellular organization was distinguishable from the surrounding articular cartilage. Processed chondrograft demonstrated good osteochondral integration, and the resulting tissue appeared to be hyaline cartilage.

CONCLUSION

The applied cartilage surface processing method allows acceptable osteochondral integration, and the repair tissue appears to have good macroscopic and histologic characteristics.

CLINICAL RELEVANCE

If further studies confirm its efficacy, this technique could be considered for human application in the future.

Chondrocyte viability is higher after prolonged storage at 37 degrees C than at 4 degrees C for osteochondral grafts

BACKGROUND

Osteochondral allografts are currently stored at 4 degrees C for 2 to 6 weeks before implantation. At 4 degrees C, chondrocyte viability, especially in the superficial zone, deteriorates starting at 2 weeks. Alternative storage conditions could maintain chondrocyte viability beyond 2 weeks, and thereby facilitate increased graft availability and enhanced graft quality.

PURPOSE

The objective of the study was to determine the effects of prolonged 37 degrees C storage compared with traditional 4 degrees C storage on chondrocyte viability and cartilage matrix content.

STUDY DESIGN

Controlled laboratory study.

METHODS

Osteochondral samples from humeral heads of adult goats were analyzed (i) fresh, or after storage in medium for (ii) 14 days at 4 degrees C including 10% fetal bovine serum, (iii) 28 days at 4 degrees C including 10% fetal bovine serum, (iv) 28 days at 37 degrees C without fetal bovine serum, (v) 28 days at 37 degrees C including 2% fetal bovine serum, or (vi) 28 days at 37 degrees C including 10% fetal bovine serum. Portions of samples were analyzed by microscopy after LIVE/DEAD staining to determine chondrocyte viability and density, both en face (to visualize the articular surface) and vertically (overall and in superficial, middle, and deep zones). The remaining cartilage was analyzed for sulfated glycosaminoglycan and collagen.

RESULTS

The 37 degrees C storage maintained high chondrocyte viability compared with 4 degrees C storage. Viability of samples after 28 days at 37 degrees C was approximately 80% at the cartilage surface en face, approximately 65% in the superficial zone, and approximately 70% in the middle zone, which was much higher than approximately 45%, approximately 20%, and approximately 35%, respectively, in 4 degrees C samples after 28 days, and slightly decreased from approximately 100%, approximately 85%, and approximately 95%, respectively, in fresh controls. Cartilage thickness, glycosaminoglycan content, and collagen content were maintained for 37 degrees C and 4 degrees C samples compared with fresh controls.

CONCLUSION

The 37 degrees C storage of osteochondral grafts supports long-term chondrocyte viability, especially at the vulnerable surface and superficial zone of cartilage.

CLINICAL RELEVANCE

Storage of allografts at a physiologic temperature of 37 degrees C may prolong storage duration, improve graft availability, and improve treatment outcomes.

What do we really know about allografts?

The use of allografts in sports medicine is becoming increasingly popular, and, therefore, this issue of Clinics in Sports Medicine is dedicated to the use of allografts in sports medicine. The majority of indications are related to the use of soft tissue grafts for ligament reconstruction, osteochondral (OC) allografts for articular surface reconstruction, and meniscal allografts for meniscal transplantation. There is an increasing amount of science and literature dealing with healing and outcomes, but many questions still remain. There are a number of issues, controversies, and lack of long-term outcomes to make definitive statements on what is really known about allograft use in sports medicine.

Osteochondral allografts: state of the art

The use of osteochondral allografts to treat focal osteochondral lesions continues to gain popularity, supported by long-term results. Clinicians must be knowledgeable concerning the possible risks of disease transmission, graft rejection, infection, and graft failure to advise the patient and obtain an informed consent. With advancing scientific and clinical research, future operative indications will likely continue to expand. A significant amount of literature regarding storage methods has recently been published; it is hoped that continued research will lead to techniques for prolonged graft storage to prevent availability concerns.

Refrigerated osteoarticular allografts to treat articular cartilage defects of the femoral condyles. A prospective outcomes study

BACKGROUND

Because of concerns about infections with the use of fresh osteoarticular allografts, osteoarticular allografts are currently stored hypothermically for a minimum of fourteen days to allow for serologic and microbiologic testing prior to implantation. Refrigerated osteoarticular allograft transplants are often used to treat symptomatic chondral and osteochondral defects in young, active patients. Chondrocyte viability has been shown to decrease substantially when allografts are stored for longer than twenty-eight days. The purpose of this study was to examine the clinical and functional outcomes of patients receiving refrigerated osteoarticular allografts between fifteen and twenty-eight days after procurement.

METHODS

Twenty-three consecutive patients (twenty-three knees) who underwent treatment of focal articular cartilage defects of the femoral condyles with refrigerated osteoarticular grafts were prospectively followed for an average of three years. The average age of the implanted refrigerated allografts was 20.3 days. The patients were assessed preoperatively and postoperatively with validated outcome surveys.

RESULTS

The mean modified Cincinnati knee ratings significantly improved from baseline to the time of the final follow-up, with an increase from 27.3 to 36.5 on the subscale rating for function (p<0.01), from 21.9 to 32.5 on the subscale rating for symptoms (p<0.03), and from 49.2 to 69.0 for the overall score (p<0.02). The mean International Knee Documentation Committee subjective score improved from 52 points at baseline to 68.5 points at the time of the final follow-up (p<0.03). A significant improvement was also found for effusions and functional testing (the single-leg hop) (p<0.001 for both). Radiographic evaluation at the time of the final follow-up revealed that twenty-two of the twenty-three grafts were in stable position with good osseous incorporation into host bone. No graft failure was encountered.

CONCLUSIONS

Transplantation of refrigerated osteoarticular allografts stored between fifteen and twenty-eight days provides significant functional and clinical improvement after an average follow-up of three years in patients treated for a full-thickness osteochondral defect of the femoral condyle, with similar outcomes to historical reports of patients with fresh allograft implants.

Cold preservation of rat osteochondral tissues in two types of solid organ preservation solution, culture medium and saline

We compared Dulbecco's modified Eagle's medium (DMEM), saline, Euro-Collins (EC) solution and University of Wisconsin (UW) solution to determine which was best for cold preservation of rat osteochondral tissues (OCTs). After 7 days' cold preservation, OCTs kept in UW solution had the highest relative viable cell number by the tetrazolium assay and the lowest activity of lactate dehydrogenase released from damaged cells. Histological evaluation revealed chondrocyte deformity, such as shrunken cytoplasm and pyknotic nuclei, particularly in the deeper layer of articular cartilage after preservation in saline and EC solution and predominantly in all layers if preserved in DMEM. In contrast, chondrocyte morphology in all layers of the articular cartilage preserved in UW solution was relatively unchanged and remained similar to fresh OCTs. It is therefore concluded that UW solution is the most suitable for cold preservation of rat OCTs as well as solid organs.

Enhancing osteochondral allograft viability: effects of storage media composition

Osteochondral allograft transplantation is a well-accepted treatment for articular cartilage damage. However, chondrocyte viability declines during graft storage, which may compromise graft performance. We first tested the hypothesis that the composition of commonly used storage media affects the viability of articular chondrocytes over time; we then tested the hypothesis that the addition of insulin growth factor-1 or the apoptosis inhibitor ZVAD-fmk could enhance the storage properties of serum-free media. Bovine osteochondral grafts were stored at 4 degrees C in lactated Ringer's, Dulbecco's modified eagle's media (DMEM), DMEM supplemented with either insulin growth factor-1 or ZVAD-fmk, and a commercial storage media. Chondrocyte viability in lactated Ringer's declined rapidly to 20.4% at 2 weeks. Viability in DMEM declined more slowly to 54.8% at 2 weeks and 31.2% at 3 weeks. Viability in commercial storage media was 83.6% at 3 weeks and 44.8% at 4 weeks. Viability was increased in DMEM + insulin growth factor-1 (56.4%) and DMEM + ZVAD (52.4%) at 3 weeks compared with DMEM alone. These results confirm the hypotheses that media composition greatly influences chondrocyte viability during cold storage and that insulin growth factor-1 and ZVAD improve the storage properties of DMEM.

Material properties of fresh cold-stored allografts for osteochondral defects at 1 year

Little is known about the long-term properties of fresh cold-stored osteochondral allograft tissue. We hypothesized fresh cold-stored tissue would yield superior material properties in an in vivo ovine model compared to those using freeze-thawed acellular grafts. In addition, we speculated that a long storage time would yield less successful grafts. We created 10-mm defects in medial femoral condyles of 20 sheep. Defects were reconstructed with allograft plugs stored at 4 degrees C for 1, 14, and 42 days; control specimens were freeze-thawed or defect-only. At 52 weeks, animals were euthanized and retrieved grafts were analyzed for cell viability, gross morphology, histologic grade, and biomechanical and biochemical analysis. Explanted cold-stored tissue had superior histologic scores over freeze-thawed and defect-only grafts. Specimens stored for 1 and 42 days had higher equilibrium moduli and proteoglycan content than freeze-thawed specimens. We observed no difference among any of the cold-stored specimens for chondrocyte viability, histology, equilibrium aggregate modulus, proteoglycan content, or hypotonic swelling. Reconstructing cartilage defects with cold-stored allograft resulted in superior histologic and biomechanical properties compared with acellular freeze-thawed specimens; however, storage time did not appear to be a critical factor in the success of the transplanted allograft.

The 5.5-year results of MegaOATS--autologous transfer of the posterior femoral condyle: a case-series study

INTRODUCTION

Large osteochondral defects of the weight-bearing zones of femoral condyles in young and active patients were treated by autologous transfer of the posterior femoral condyle (large osteochondral autogenous transplantation system (MegaOATS)). The technique presented is a sound and feasible salvage procedure to address large osteochondral defects in weight-bearing zones.

METHODS

Thirty-six patients between July 1996 and December 2000 were included. Thirty-three patients (10 females, 23 males) were evaluated by the Lysholm score and X-ray scans. A random sample of 16 individuals underwent magnetic resonance imaging analysis. The average age at the date of surgery was 34.3 (15 to 59) years, and the mean follow up was 66.4 (46 to 98) months. The mean defect size was 6.2 (2 to 10.5) cm2, in 27 patients affecting the medial femoral condyle and in six patients affecting the lateral femoral condyle. Trauma or osteochondrosis dissecans were pathogenetic in 82%.

RESULTS

The Lysholm score in all 33 individuals showed a highly significant increase from a preoperative median 49.0 points to a median 86.0 points (P < or = 0.001). Twenty-seven patients returned to recreational sports. X-ray scans showed a rounding of the osteotomy edge in 24 patients, interpreted as a partial remodelling of the posterior femoral condyle. Preoperative osteoarthritis in 17 individuals was related to significant lower Lysholm scores (P = 0.014), but progression in 17 patients did not significantly influence the score results (P = 0.143). All 16 magnetic resonance imaging examinations showed vital and congruent grafts.

CONCLUSION

Patients significantly improve in the Lysholm score, in daily-life activity levels and in return to recreational sports. Thirty-one out of 33 patients were comfortable with the results and would undergo the procedure again. The MegaOATS technique is therefore recommended as a salvage procedure for young individuals with large osteochondral defects in the weight-bearing zone of the femoral condyle.

Optimizing CO2 normalizes pH and enhances chondrocyte viability during cold storage

Fresh osteochondral allografts are an important treatment option for the repair of full-thickness articular cartilage defects. Viable chondrocytes within the transplanted tissue are considered important to maintaining matrix integrity. The purpose of this study is to determine whether an increase in pH decreases chondrocyte viability during cold storage and whether equilibration of Dulbecco's modified Eagle's medium (DMEM) in 5% CO(2) normalizes pH and increases chondrocyte survival during storage at 4 degrees C. Freshly isolated bovine articular chondrocytes cultured in alginate beads were stored for up to 5 days at 4 degrees C or 37 degrees C in DMEM exposed to ambient air or in DMEM equilibrated with 5% CO(2). Chondrocyte viability was determined by flow cytometry. Physiologic pH was maintained when DMEM was equilibrated with 5% CO(2), while pH increased in ambient air. After 5 days of storage at 4 degrees C, chondrocyte necrosis was higher when stored in ambient air than if equilibrated with 5% CO(2). No decrease in chondrocyte viability was observed with storage at 37 degrees C. In addition, chondrocyte viability in bovine cartilage osteochondral cores was examined after storage for 14 days at 4 degrees C in DMEM with and without HEPES, and with and without 5% CO(2). Under these conditions, the superficial layer of chondrocytes was more viable when stored in DMEM with HEPES or DMEM equilibrated with 5% CO(2) than when stored in DMEM in ambient air. This data shows that an increase in pH decreased bovine chondrocyte viability when refrigerated at 4 degrees C in DMEM, and that optimization of CO(2) normalized pH and improved chondrocyte viability during cold storage in DMEM.

Reversal of suppressed metabolism in prolonged cold preserved cartilage

Chondrocytes in cold preserved cartilage are metabolically suppressed. The goal of this study was to address this metabolic suppression and seek ways to reverse it. Specifically, we examined the roles of rewarming protocols and nitric oxide (NO) in this metabolic suppression. Bovine and canine full-thickness articular cartilage explants were cultured under various temperature conditions, and NO production, proteoglycan (PG) synthesis, and cell viability were measured. Nitric oxide was shown to be negatively correlated with PG synthesis following abrupt rewarming of cold preserved osteochondral allografts. Gradual rewarming of the allograft tissue decreased NO production with higher PG synthesis. Inhibition of nitric oxide synthases (NOS) led to a decrease in NO production and a concomitant increase in PG synthesis. We were able to partially reverse metabolic suppression of cold preserved osteochondral allograft material with gradual rewarming and decrease NO production with NOS inhibition. Chondrocytes in cold preserved allograft material may be metabolically suppressed predisposing the graft to failure in vivo. Minimizing this loss of metabolic function by gradual graft rewarming and decreasing NO production by NOS inhibition at the time of graft implantation may have implications on graft survival in vivo.

Fluorescent viability stains overestimate chondrocyte viability in osteoarticular allografts

BACKGROUND

Allografts from many tissue banks are carefully processed and stored with the goal of preserving chondrocyte viability. However, the importance of living chondrocytes for graft stability is unclear, in part because actual viabilities of individual allografts at the time of placement are seldom known.

HYPOTHESES

Cell yields from allograft and fresh cartilage differ significantly if chondrocyte viability in allografts is lower than indicated by fluorescence staining with conventional viability probes. In addition, transmission electron microscopy will show significant differences in the percentage of morphologically abnormal chondrocytes in allograft and fresh cartilage.

STUDY DESIGN

Controlled laboratory study.

METHODS

Fluorescence viability staining, chondrocyte yield, and chondrocyte characteristics were studied in 8 commercial osteochondral allografts (7 hemicondyles, 1 talus) and 4 freshly harvested cartilage samples from an adult distal femur (age, 46 years), from an adult talus (age, 51 years), and from an adult tibial plateau (age, 29 years) and from a juvenile distal tibia (age, 9 years). Selected fresh and allograft specimens were repeatedly frozen and thawed to deliberately kill chondrocytes by membrane disruption. The findings were analyzed to determine if allograft and fresh cartilage were significantly different with respect to each of the 3 different outcome measures.

RESULTS

Although fluorescent staining indicated that approximately 75% of chondrocytes were viable (calcein AM-labeled) in allograft cartilage, counterstaining with 4,'6-diamidino-2-phenylindole showed that fewer than 30% contained identifiable nuclei. In contrast, 100% of cells labeled as viable contained nuclei in fresh cartilage. Killing chondrocytes by freeze-thawing before staining did not diminish calcein AM staining in allograft cartilage but caused a significant reduction in fresh cartilage. The average yield of chondrocytes from allograft cartilage was less than 200,000/100 mg tissue, significantly lower than in fresh cartilage, which averaged more than 1.5 million/100 mg tissue. The yield from freeze-thawed controls was less than 24,000/100 mg. Cell numbers increased after 7 days of culture in all cases except for chondrocytes from freeze-thawed cartilage, an indication that the isolated cells were viable. Morphologic analysis by transmission electron microscopy revealed significant increases in the numbers of chondrocytes with pyknotic or absent nuclei or with disintegrated plasma membranes in allograft versus fresh cartilage.

CONCLUSION

Conventional fluorescence probes are unreliable for analyzing chondrocyte viability in osteoarticular allografts. Alternative methods for assessment of viability, such as cell culture and ultrastructural imaging, may provide more accurate assessment of viability in allografts.

CLINICAL RELEVANCE

Conventional staining methods that overestimate chondrocyte viability in osteoarticular allografts may mislead investigators attempting to assess the effects of chondrocyte viability on graft stability following implantation. A more reliable means to measure chondrocyte viability will be required to accurately assess these effects.

Colloidal 90Y used for radiation synovectomy decreases the viability of chondrocytes in human cadaveric samples

OBJECTIVE

To analyse the early effect of colloidal 90Y beta irradiation, as used for radiation synovectomy (RSV), on the viability of human chondrocytes in an ex-vivo model.

METHODS

Twenty osteochondral plugs (6 mm in diameter) were procured from femoral condyles of an adult male donor and stored in normal saline at 4 degrees C. The cartilage surfaces of 10 plugs were contaminated with colloidal 90Y citrate corresponding to the standard knee RSV dose (185 MBq) matched for the sample size (430 kBq). The remaining 10 plugs served as controls. At days 1, 2, 3, 6 and 13, two osteochondral plugs from each group were stained for viability with live/dead probes and scanned under a confocal laser microscope. The ratios of viable (green channel) and non-viable (red channel) pixels were acquired in four cartilage depth regions and statistically analysed with a regression model.

RESULTS

The irradiation did not significantly alter the viable/non-viable pixel ratio during the first 2 days, but longer exposures led to a significant and time progressive reduction from 8.7% (day 3) to 12.5% (day 13). The ratio was less affected deeper in the cartilage, where it increased about 1% for every 100 microm from the surface.

CONCLUSIONS

Surface exposure of human cadaveric cartilage to a therapeutic dose of colloidal 90Y decreased chondrocyte viability, expressed as the viable/non-viable pixel ratio, in the early post-irradiation period. The findings established in the ex-vivo simulation may reflect the changes in knee cartilage occurring after RSV therapy.

Cell viability and protein composition in cryopreserved cartilage

Chondrocyte survival in frozen-stored osteochondral allografts is low. We analyzed different storage conditions to determine the best for maintenance or storage for preserving cartilage. We hypothesized cell viability and extracellular protein content could be improved with better cryopreservation. Articular cartilage from nine sheep femoral condyles were stored at 4 degrees C, -80 degrees C, and -196 degrees C with and without cryopreservative agents for 1 month. We determined cell viability and performed Western blot analysis for TGF-beta, IGF-1, and MMP-2, 9, and 13. We observed decreases in viability in cartilage stored at 4 degrees C: 36.2% viability when stored without solution, 40.4% in phosphate-buffered saline, and 48.1% in culture medium. TGF-beta and IGF-1 decreased in the first week in all groups. The groups stored at -80 degrees C and -196 degrees C contained less protease in the last 2 weeks. In the groups stored at 4 degrees C in phosphate-buffered saline, we detected no increase in the levels of MMPs. Our data discourage the use of frozen cartilage because of the decrease of cell viability and elevation in MMPs. However, modifying the freezing conditions might moderate these changes and improve the state of preserved cartilage.

Clinical, histologic, and radiographic outcomes of distal femoral resurfacing with hypothermically stored osteoarticular allografts

BACKGROUND

Fresh osteoarticular allograft transplantation has a long history of clinical success. These grafts have typically been implanted less than 1 week from donor asystole.

HYPOTHESIS

Osteoarticular allografts stored 4 to 6 weeks represent a viable alternative to treat full-thickness cartilage and osteochondral defects of the distal femur as measured by clinical, histologic, and magnetic resonance imaging (MRI) criteria.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Osteoarticular allografts were implanted after a mean graft storage time (at 4 degrees C) of 36 days (range, 28-43). Sixty-seven patients received massive hypothermically stored osteoarticular allografts. Ten knees in 8 of these patients underwent second-look arthroscopic evaluation and biopsy at a mean of 40 months (range, 23-60) after implantation. Clinical assessment was performed using multiple outcome measures and sequential MRI evaluations. Biopsy specimens were obtained from the graft as well as from native articular cartilage at the time of second-look arthroscopy for histologic analysis.

RESULTS

The mean International Knee Documentation Committee scores were as follows: preoperative, 27 (range, 9-55); postoperative, 79 (range, 56-99); P = .002. The mean Lysholm scores were as follows: preoperative, 37 (range, 12-47); postoperative, 78 (range, 55-90); P = .002. The mean Short Form-36 physical scores were as follows: preoperative, 38 (range, 24-55); postoperative, 51 (range, 39-61); P = .002. The mean Tegner scores were as follows: preoperative, 4.3 (range, 1-9); postoperative, 5.3 (range, 4-7); P = .16. The mean International Cartilage Repair Society score at follow-up was 10 (nearly normal) (range, 7-11). The mean modified Outerbridge scores were as follows: preoperative, 4.3 (range, 3-5); postoperative, 0.6 (range, 0-1); P = .002. The mean graft and native cartilage cellular density and viability were not statistically different.

CONCLUSIONS

Fresh-stored osteoarticular grafts for full-thickness articular surface defects of the distal femur appear to offer a viable biological method to restore knee function. Our study suggests that osteoarticular grafts stored in cell culture medium at 4 degrees C for 4 to 6 weeks provide successful short-term clinical outcomes.

Prospective evaluation of prolonged fresh osteochondral allograft transplantation of the femoral condyle: minimum 2-year follow-up

BACKGROUND

Focal articular cartilage lesions of the knee in young patients present a therapeutic challenge. Little information is available pertaining to the results after implantation of prolonged fresh grafts.

HYPOTHESIS

Prolonged fresh osteochondral allografts present a viable option for treating large full-thickness articular cartilage lesions.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

This study presents the results of 25 consecutive patients who underwent prolonged fresh osteochondral allograft transplantation for defects in the femoral condyle. The average patient age was 35 years (range, 17-49 years). The average length of follow-up was 35 months (range, 24-67 months). Prospective data were collected using several subjective scoring systems, as well as objective and radiographic assessments.

RESULTS

Statistically significant improvements (P < .05) were seen for the Lysholm (39 to 67), International Knee Documentation Committee scores (29 to 58), all 5 components of the Knee injury and Osteoarthritis Outcome Score (Pain, 43 to 73; Other Disease-Specific Symptoms, 46 to 64; Activities of Daily Living Function, 56 to 83; Sport and Recreation Function, 18 to 46; Knee-Related Quality of Life, 22 to 50), and the Short Form-12 physical component score (36 to 40). Overall, patients reported 84% (range, 25% to 100%) satisfaction with their results and believed that the knee functioned at 79% (range, 35% to 100%) of their unaffected knee. Radiographically, 22 of the grafts (88%) were incorporated into host bone.

CONCLUSION

Fresh osteochondral allograft transplantation is an acceptable intermediate procedure for treatment of localized osteochondral defects of the femur. At 2-year follow-up, it is well incorporated and offered consistent improvements in pain and function.

CLINICAL RELEVANCE

Prolonged fresh allograft transplantation is a safe and effective technique for addressing symptomatic osteoarticular lesions in the knees of young patients.

Comparison of fresh osteochondral autografts and allografts: a canine model

BACKGROUND

Osteochondral autografts and allografts have been widely used in the treatment of isolated grade IV articular cartilage lesions of the knee. However, the authors are not aware of any study that has prospectively compared fresh osteochondral autografts to fresh allografts with regard to imaging, biomechanical testing, and histology.

HYPOTHESIS

The imaging, biomechanical properties, and histologic appearance of fresh osteochondral autograft and fresh allograft are similar with respect to bony incorporation into host bone, articular cartilage composition, and biomechanical properties.

STUDY DESIGN

Controlled laboratory study.

METHODS

Eighteen adult dogs underwent bilateral knee osteochondral graft implantation after creation of an Outerbridge grade IV cartilage defect. One knee received an autograft, and the contralateral knee received a fresh allograft. Nine dogs were sacrificed at 3 months, and 9 dogs were sacrificed at 6 months. Graft analysis included gross examination, radiographs, magnetic resonance imaging, biomechanical testing, and histology.

RESULTS

Magnetic resonance imaging demonstrated excellent bony incorporation of both autografts and allografts. Biomechanical testing demonstrated no significant difference between autografts versus allografts versus control at 3 or 6 months (P = .36-.91). A post hoc calculation showed 80% power to detect a 30% difference between allograft and control. Histologic examination showed normal cartilage structure for both autografts and allografts.

CONCLUSION

Fresh osteochondral autograft and fresh allograft tissues are not statistically different with respect to bony incorporation, articular cartilage composition, or biomechanical properties up to 6 months after implantation.

CLINICAL RELEVANCE

The use of fresh allograft tissue to treat osteochondral defects eliminates morbidity associated with harvesting autograft tissue without compromising the results of the surgical procedure.

Does subchondral bone affect the fate of osteochondral allografts during storage?

BACKGROUND

Osteochondral allografts currently are hypothermically stored for a minimum of 14 days to a maximum of 28 days before surgical implantation, making storage conditions increasingly important. Previous studies have suggested that graft deterioration during storage may result from degradative factors and residual marrow elements in the subchondral bone.

HYPOTHESIS

Allografts stored with large bone-to-cartilage ratios will be compromised after prolonged storage compared with grafts with minimal bone.

STUDY DESIGN

Controlled laboratory study.

METHODS

Osteochondral plugs were harvested from 16 fresh human femoral condyles and randomly assigned to 1 of 3 groups based on bone-to-cartilage ratios: 1:1, 5:1, or 10:1. These ratios were considered on the basis that the 1:1 ratio is the minimum bone necessary to press-fit an allograft and 10:1 is the present ratio used by tissue banks for allograft storage. After 14 and 28 days of storage at 4 degrees C, the specimens were assessed for viability and viable cell density using confocal microscopy, proteoglycan synthesis by (35)SO4 incorporation, and glycosaminoglycan content.

RESULTS

All grafts underwent a significant decline in viable cell density, proteoglycan synthesis, and chondrocyte viability (particularly in the superficial region) after 14 days of storage, but no differences were observed between the 1:1, 5:1, or 10:1 ratio groups at either day 14 or day 28. In addition, no significant difference was noted in the glycosaminoglycan content in any of the groups.

CONCLUSION

Osteochondral allografts stored with a 10:1 bone-to-cartilage ratio, similar to tissue-banking ratios, performed no worse than allografts stored with minimal bone, suggesting that the bone-to-cartilage ratio plays little to no role in the degradation of allografts during prolonged storage.

CLINICAL RELEVANCE

As the practice of osteochondral allograft resurfacing becomes more commonplace, it is important that surgeons understand the factors that affect graft quality.

The Repair Response to Osteochondral Implant Types in a Rabbit Model

Current treatments for damaged articular cartilage (i.e., shaving the articular surface, perforation or abrasion of the subchondral bone, and resurfacing with periosteal and perichondrial resurfacing) often produce fibrocartilage, or hyaline-appearing repair that is not sustained over time (Henche 1967, Ligament and Articular Cartilage Injuries. Springer-Verlag, New York, NY, pp. 157-164; Insall 1974, Clin. Orthop. 101: 61-67; Mitchell and Shepard 1976, J. Bone Joint Surg. [Am.] 58: 230-233; O'Driscoll et al. 1986, J. Bone Joint Surg. [Am.] 68: 1017-1035; 1989, Trans. Orthop. Res. Soc. 14: 145; Kim et al. 1991, J. Bone Joint Surg. [Am.] 73: 1301-1315). Autologous chondrocyte transplantation, although promising, requires two surgeries, has site-dependent and patient age limitations, and has unknown long-term donor site morbidity (Brittberg et al. 1994, N Engl. J. Med. 331: 889-895; Minas 2003, Orthopedics 26: 945-947; Peterson et al. 2003, J. Bone Joint Surg. Am. 85-A(Suppl. 2): S17-S24). Osteochondral allografts remain a widely used method of articular resurfacing to delay arthritic progression. The present study compared the histological response to four types of osteochondral implants in a rabbit model: autograft, frozen, freeze-dried, and fresh implants. Specimens implanted in the femoral groove were harvested at 6 and 12 weeks. Results showed similar restoration of the joint surface regardless of implant type, with a trend toward better repair at the later timepoint. As has been observed in other studies (Frenkel et al. 1997, J. Bone Joint Surg. 79B: 281-286; Toolan et al. 1998, J. Biomed. Mater. Res. 41: 244-250), each group in this study had at least one specimen in which a healthy-appearing surface on the implant was not well-integrated with host tissues. Although the differences were not statistically significant, freeze-dried implants at both timepoints had the best histological scores. The osteochondral grafts tested successfully restored the gross joint surface and congruity. At 12 weeks, no significant differences were observed between the various allografts and autologous osteochondral grafts.

Indications for allografts

Allografts continue to be popular in orthopaedic reconstruction procedures of the knee. Approximately 1 million musculoskeletal allografts were distributed in the United States in 2004 alone. Ligament allografts, osteochondral allografts, and meniscal transplants have all demonstrated success in knee reconstructions. The advantages of allograft tissue include the lack of donor site morbidity, shorter operative times, ease of sizing, and a lack of clinically significant immunologic reactions. These advantages should be weighed against the risk for disease transmission, increased cost, and increased time of graft incorporation. Throughout the consent process, comprehensive patient education is imperative to assist in this important decision.

Analysis of stored osteochondral allografts at the time of surgical implantation

BACKGROUND

To date, the morphological, biochemical, and biomechanical characteristics of articular cartilage in osteochondral allografts that have been stored have not been fully described.

HYPOTHESIS

Osteochondral allografts procured and stored commercially for a standard period as determined by tissue banking protocol will have compromised chondrocyte viability but preserved extracellular matrix quality.

STUDY DESIGN

Controlled laboratory study.

METHODS

Unused cartilage from 16 consecutive osteochondral allografts was sampled during surgery after tissue bank processing and storage. Ten grafts were examined for cell viability and viable cell density using confocal microscopy, proteoglycan synthesis via 35SO4 uptake, and glycosaminoglycan content and compared with fresh cadaveric articular cartilage. Biomechanical assessment was performed on the 6 remaining grafts by measuring the indentation stiffness of the cartilage.

RESULTS

The mean storage time for the transplanted specimens was 20.3 +/- 2.9 days. Chondrocyte viability, viable cell density, and 35SO4 uptake were significantly lower in allografts at implantation when compared to fresh, unstored controls, whereas matrix characteristics, specifically glycosaminoglycan content and biomechanical measures, were unchanged. In addition, chondrocyte viability in the stored allografts was preferentially decreased in the superficial zone of cartilage.

CONCLUSION

Human osteochondral allografts stored for a standard period (approximately 3 weeks) before implantation undergo decreases in cell viability, especially in the critically important superficial zone, as well as in cell density and metabolic activity, whereas matrix and biomechanical characteristics appear conserved. The exact clinical significance of these findings, however, is unknown, as there are no prospective studies examining clinical outcomes using grafts stored for extended periods.

CLINICAL RELEVANCE

Surgeons who perform this procedure should understand the cartilage characteristics of the graft after 21 days of commercial storage in serum-free media.

Management of big osteochondral defects of the knee using osteochondral allografts with the MEGA-OATS technique

Treatment of osteochondral defects in weight-bearing areas of the knee, especially when they are sizeable and involve considerable subchondral bone loss, is a challenging problem. We report our experience on the use of osteochondral allografts with the MEGA-OATS technique in the management of large osteochondral defects of the knee in young patients. Five patients (3 male and 2 female) were included in this study; their age ranged from 22 to 41 years and the mean size of the defect covered was 30 x 30 mm. They were followed for a minimum of 2.5 years (mean: 32.8 months, range 30-36). An age- and size-matched fresh frozen, non-irradiated distal femoral allograft was used to obtain the donor plug, which was then inserted in the recipient area in a press-fit fashion. Patients' Lysholm knee score increased from 37.8 pre-operatively to 73.8 post-operatively. Tegner activity score increased in all five patients; it improved from a mean of 2 pre-operatively (range 1-3) to 4 post-operatively (range 2-7). Four out of five patients returned to work and three went back to sporting activities. With this technique one can cover sizeable osteochondral defects, and compensate for significant subchondral bone loss, while accurate reconstruction of the curvature of the femoral condyle is allowed. We believe that it is a viable salvage option in young patients with big osteochondral defects of the knee. It offers very satisfactory functional results and does not compromise patients' future options.