Osteochondral allograft transplantation in cartilage repair: Graft storage paradigm, translational models, and clinical applications

Using engineering models to shorten cryoprotectant loading time for the vitrification of articular cartilage

Osteochondral allograft transplantation can treat full thickness cartilage and bone lesions in the knee and other joints, but the lack of widespread articular cartilage banking limits the quantity of cartilage available for size and contour matching. To address the limited availability of cartilage, vitrification can be used to store harvested joint tissues indefinitely. Our group's reported vitrification protocol [Biomaterials 33 (2012) 6061-6068] takes 9.5 h to load cryoprotectants into intact articular cartilage on bone and achieves high cell viability, but further optimization is needed to shorten this protocol for clinical use. Herein, we use engineering models to calculate the spatial and temporal distributions of cryoprotectant concentration, solution vitrifiability, and freezing point for each step of the 9.5-h protocol. We then incorporate the following major design choices for developing a new shorter protocol: (i) all cryoprotectant loading solution concentrations are reduced, (ii) glycerol is removed as a cryoprotectant, and (iii) an equilibration step is introduced to flatten the final cryoprotectant concentration profiles. We also use a new criterion-the spatially and temporally resolved prediction of solution vitrifiability-to assess whether a protocol will be successful instead of requiring that each cryoprotectant individually reaches a certain concentration. A total cryoprotectant loading time of 7 h is targeted, and our new 7-h protocol is predicted to achieve a level of vitrifiability comparable to the proven 9.5-h protocol throughout the cartilage thickness.

Comparison of three multi-cryoprotectant loading protocols for vitrification of porcine articular cartilage

Vitrification is a cryopreservation technique for the long-term storage of viable tissue, but the success of this technique relies on multiple factors. In 2012, our group published a working vitrification protocol for intact human articular cartilage and reported promising chondrocyte recovery after using a four-step multi-cryoprotectant (CPA) loading method that required 570 min. However, this protocol requires further optimization for clinical practice. Herein, we compared three multi-step CPA loading protocols to investigate their impact on chondrocyte recovery after vitrification of porcine articular cartilage on a bone base, including our previous four-step protocol (original: 570 min), and two shorter three-step protocols (optimized: 420 min, and minimally vitrifiable: 310 min). Four different CPAs were used including glycerol, dimethyl sulfoxide, ethylene glycol and propylene glycol. As vitrification containers, two conical tubes (50 ml and 15 ml) were evaluated for their heat transfer impact on chondrocyte recovery after vitrification. Osteochondral dowels were cored into two diameters of 10.0 mm and 6.9 mm with an approximately 10-mm thick bone base, and then allocated into the twelve experimental groups based on CPA loading protocol, osteochondral dowel size, and vitrification container size. After vitrification at -196 °C and tissue warming and CPA removal, samples in all groups were assessed for both chondrocyte viability and metabolic activity. The optimized protocol proposed based on mathematical modelling resulted in similar chondrocyte recovery to our original protocol and it was 150 min shorter. Furthermore, this study illustrated the role of CPA permeation (dowel size) and heat transfer (container size) on vitrification protocol outcome.

Assessment of Cell Viability of Fresh Osteochondral Allografts in N-Acetylcysteine-Enriched Medium

OBJECTIVE

The purpose of this study was to evaluate the effect of N-acetylcysteine (NAC)-enriched storage medium on fresh osteochondral viability at 4°C. Our hypothesis was that the cell viability of chondrocytes obtained from human osteochondral tissue and stored at 4°C significantly improves in the presence of NAC.

DESIGN

Controlled laboratory study. For this study, 8 samples of femoral condyle osteochondral tissue were obtained from patients undergoing total knee replacement. The samples were stored at either 4°C in phosphate-buffered saline (PBS) or at 3 different concentrations of NAC (NAC 1, 2, and 5 mM). Cell viability was analyzed at time 0 and 4 weeks by flow cytometry. The results of cell viability (median) were analyzed statistically using analysis of variance and Tukey's post hoc test. P values <0.05 were considered statistically significant.

RESULTS

The viability at time 0 was 95.5% ± 3.7%. At 4 weeks, the cell viability was 56.8% ± 20.1% in the control group (PBS), 83.8% ± 11.9% in the group stored with NAC 1 mM, 73.4% ± 13.6% in the group stored with NAC 2 mM, and 66.4% ± 27.7% in the group stored with NAC 5 mM. A statistically significant difference from the baseline viability (time 0) was observed in the PBS control group (P = 0.0018) but not in the other groups. A statistically significant difference was observed in the NAC 1 mM group compared with the PBS group (P = 0.0255).

CONCLUSION

The use of NAC at 1 mM concentration improves cell viability after 4 weeks of storage in chondrocytes obtained from human osteochondral tissue.

Use of Allografts in Orthopaedic Surgery: Safety, Procurement, Storage, and Outcomes

The use of allografts has become a vital option for orthopaedic surgeons in the treatment of a variety of musculoskeletal lesions, ranging from osteochondral defects in the glenohumeral joint to meniscal deficiency in the young athlete. Nevertheless, barriers to treating a patient with an allograft-based procedure may arise from concerns over disease transmission, the navigation of tissue banks that supply allografts, the process of obtaining insurance approval, or optimal storage methods. This review serves to support orthopaedic surgeons in the incorporation of allografts into their practice by quelling these potential concerns. Fresh osteochondral allografts, fresh-frozen meniscal allografts, soft tissue allografts, and off-the-shelf cartilage products are the focus of this review amid broad overviews of allograft safety and tissue bank practices in the United States.

Fresh Osteochondral Resurfacing of the Patellofemoral Joint

Large osteochondral lesions of the knee in young patients continue to be a challenge for orthopaedic surgeons and the focus of continual research. This is particularly true if the injury is a consequence of a dysplastic trochlea and involves both articular surfaces of the biomechanically complex patellofemoral joint. To obtain a healthy and congruent patellofemoral joint, the use of a bipolar fresh osteochondral allograft transplantation of the patella and trochlea is one of the few options to biologically treat these injuries. This would achieve a replacement of the entire articular surface of the patellofemoral joint with a high number of viable chondrocytes and respect the unique structural characteristics of the cartilage. The aim of this study was to obtain symptomatic and functional improvements while delaying the timing of prosthetic surgery. We present a reproducible although demanding surgical technique to perform a bipolar fresh osteochondral allograft transplantation of the patella and trochlea.

Chondral Delamination of Fresh Osteochondral Allografts after Implantation in the Knee: A Matched Cohort Analysis

INTRODUCTION

Delamination of the chondral surface of an osteochondral allograft (OCA) from the underlying cancellous bone has been described as a mode of failure after implantation in the knee. Our hypothesis was that increased storage time of the OCA is associated with increased risk of graft delamination after implantation.

METHODS

Prospective data on 13 patients with evidence of OCA delamination identified on magnetic resonance imaging or during subsequent surgery from 2000 to 2015 were reviewed. A cohort of 33 patients without evidence of graft delamination were then matched to the delamination group based on recipient age, sex, body mass index (BMI), and chondral defect location. The matched cohort size was established based on a power calculation for determining differences in OCA storage times. All patients had a minimum 2-year follow-up.

RESULTS

There was no difference in donor age, donor sex, and graft storage time between groups (30 vs. 31 days, P = 0.78). There were no differences between number of previous ipsilateral knee surgeries (1.8 vs. 0.84, P = 0.26), BMI (26.8 vs. 25.0 kg/m², P = 0.31), total chondral defect size (6.5 vs. 5.8 cm², P = 0.41) or preoperative Marx activity scores between groups.

CONCLUSION

There is no association between OCA storage time, activity level scores, or number of previous ipsilateral knee surgeries and graft delamination in our patient population. Further work is needed to identify the etiology for this mode of failure of OCAs.

Pulse Lavage Fails to Significantly Reduce Bone Marrow Content in Osteochondral Allografts: A Histological and DNA Quantification Study

BACKGROUND

Current clinical practice calls for pulse lavage of fresh osteochondral allografts (OCAs) to reduce immunogenicity; however, there is limited evidence of its effectiveness in reducing allogenic bone marrow elements.

PURPOSE

To evaluate the effectiveness of pulse lavage in removing marrow elements from trabecular bone in fresh OCA transplantation.

STUDY DESIGN

Controlled laboratory study.

METHODS

The authors evaluated 48 fresh OCA plugs with 4 different common sizes (14- and 24-mm diameter, 6- and 10-mm thickness). Within each size group, half of the samples underwent pulse lavage (n = 6) with saline solution and half were left untreated (no lavage; control group, n = 6). For each treatment and size group, 3 samples were analyzed for DNA content as an indicator of the number of residual nucleated cells; the other 3 samples were histologically analyzed to assess the presence and distribution of cells within subchondral bone pores in 3 specific locations within the plug: peripheral, intermediate, and core.

RESULTS

Osteochondral plugs treated with pulse lavage did not show a significant decrease in DNA content in comparison with untreated plugs. Overall, histological analysis did not show a significant difference between the treated and untreated groups (P = .23). Subgroup analysis by size demonstrated decreased marrow content in treated versus untreated groups in the thinner plug sizes (14 × 6 mm and 24 × 6 mm). Histological evaluation by zone demonstrated a significant difference between groups only in the peripheral zone (P = .04).

CONCLUSION

Pulse lavage has limited effectiveness in removing marrow elements, in particular in plugs that are larger in diameter and, more importantly, in thickness. Better techniques for subchondral bone treatment are required for more thorough removal of potentially immunogenic marrow elements.

CLINICAL RELEVANCE

OCA transplantation has become an established treatment modality. Unfortunately, OCA is not without limitations, chiefly its mode of failure through inadequate integration of the allograft subchondral bone with subsequent collapse. In an effort to improve integration, current clinical practice calls for pulse lavage to remove allogenic bone marrow from the subchondral bone in hopes of decreasing the immunogenicity of the graft and facilitating revascularization.

Unipolar allograft reconstruction for post-traumatic avascular necrosis of the distal tibia: A review of the literature, technique, and case series

BACKGROUND

Avascular necrosis of the distal tibial plafond following ankle trauma is an underreported and potentially devastating phenomenon. Beyond conservative treatment options, surgical intervention has been limited to ankle arthrodesis, which sacrifices motion and may have longterm sequellae for adjacent hindfoot joints. Total ankle replacement has been historically contraindicated. Unipolar allograft reconstruction provides an option for joint salvage. We present a literature overview, implantation technique, and two cases utilizing matched unipolar distal tibial allograft.

METHODS

Two younger patients underwent distal tibia allograft reconstruction for tibial plafond collapse due to post-traumatic avascular necrosis. They were followed to assess for clinical improvement and radiographic graft subsidence.

RESULTS

Both patients returned to work and activity. One patient had no graft subsidence at four years, but the other patient became symptomatic with graft subsidence at one year.

CONCLUSIONS

Distal tibia allograft reconstruction can be utilized as a joint salvage surgery for post-traumatic avascular necrosis with collapse of the tibial plafond in younger patients that prefer an alternative to arthrodesis. Results may be mixed and necessitate an engaged, activated patient.

LEVEL OF EVIDENCE

IV.

Metabolic responses of osteochondral allografts to re-warming

Symptomatic chondral and osteochondral defects affect a large and growing number of patients. A safe and effective surgical treatment for large articular defects is osteochondral allograft (OCA) transplantation. One of the major causes of failure for OCA transplantation is loss of essential chondrocyte viability during the preservation and storage period. It is also possible that metabolic responses of the OCA when transitioning from storage temperature to body temperature may contribute to mechanisms causing failure. The present study was designed to compare MOPS^SM -preserved OCAs to those stored using the current standard of care (SOC) method with respect to metabolic responses when rewarmed for transplantation to and maintenance at body temperature (37°C). It was theorized that grafts stored using the MOPS^SM protocol would maintain significantly higher chondrocyte viability and produce significantly lower levels of inflammatory mediators and degradative enzymes, and significantly higher levels of chemokines compared to grafts stored using the SOC protocol. Left over SOC and MOPS^SM -stored OCA tissues were collected after surgery, and cartilage explants were cultured for 6 days. Media was analyzed for biomarkers using commercially available assays. Cartilage from SOC grafts released significantly higher levels of PGE2, MMP-1, MMP-2, and MMP-13, and significantly lower levels of IL-8 and Gro-α, compared to cartilage from MOPS^SM -stored grafts. Clinical significance: These data suggest that OCAs stored using the MOPS^SM protocol have potentially less detrimental initial inflammatory and degradative responses to re-warming for transplantation compared to OCAs stored using the current tissue bank protocols. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1530-1536, 2019.

Cells, soluble factors and matrix harmonically play the concert of allograft integration

Implantation of allograft tissues has massively grown over the last years, especially in the fields related to sports medicine. Beside the fact that often no autograft option exists, autograft related disadvantages as donor-site morbidity and prolonged operative time are drastically reduced with allograft tissues. Despite the well documented clinical success for bone allograft procedures, advances in tissue engineering raised the interest in meniscus, osteochondral and ligament/tendon allografts. Notably, their overall success rates are constantly higher than 80%, making them a valuable treatment option in orthopaedics, especially in knee surgery. Complications reported for allografting procedures are a small risk of disease transmission, immunologic rejection, and decreased biologic incorporation together with nonunion at the graft-host juncture and, rarely, massive allograft resorption. Although allografting is a successful procedure, improved techniques and biological knowledge to limit these pitfalls and maximize graft incorporation are needed. A basic understanding of the biologic processes that affect the donor-host interactions and eventual incorporation and remodelling of various allograft tissues is a fundamental prerequisite for their successful clinical use. Further, the importance of the interaction of immunologic factors with the biologic processes involved in allograft incorporation has yet to be fully dissected. Finally, new tissue engineering techniques and use of adjunctive growth factors, cell based and focused gene therapies may improve the quality and uniformity of clinical outcomes. The aim of this review is to shed light on the biology of meniscus, osteochondral and ligament/tendon allograft incorporation and how collection and storage techniques may affect graft stability and embodiment.Level of evidence V.

Treatment of unstable knee osteochondritis dissecans in the young adult: results and limitations of surgical strategies-The advantages of allografts to address an osteochondral challenge

Joint surface incongruence resulting from osteochondritis dissecans (OCD) alters the articular physiologic congruence, increasing the contact stress on adjacent joint surfaces and accelerating wear and the cascade of joint degeneration. Accordingly, the restoration of articular surface integrity is of major importance, especially in young adults where, in lesions left untreated or following simple fragment excision, early osteoarthritis can be anticipated. Therefore, the treatment algorithm in unstable knee OCD of the young adult foresees surgical options to restore the articular surface. Several procedures have been proposed, including refixation of the detached fragment bone marrow stimulation, osteochondral autograft implantation, fresh osteochondral allograft transplantation, and cell-based or cell-free regenerative techniques. The aim of this review was to summarize the evidence for these surgical strategies, reporting their results and limitations. The overall evidence documents positive results for each of the assorted surgical procedures applied to treat unstable OCD, thus indicating support for their selected use to treat osteochondral defects paying particular attention to their specific indications for the lesion characteristics. The fixation of a good quality fragment should be pursued as a first option, while unfixable small lesions may benefit from autografts. For large lesions, available cell-based or cell-free osteochondral scaffold are a feasible solution but with limitation in terms of regenerated tissue quality. In this light, fresh allografts may offer articular surface restoration with viable physiologic osteochondral tissue providing a predictably successful outcome, and therefore they may currently represent the most suitable option to treat unstable irreparable OCD lesion in young adults. LEVEL OF EVIDENCE: V.

Osteochondral Allograft Transplantation of the Femoral Condyle Utilizing a Thin Plug Graft Technique

BACKGROUND

Previous studies showed clinical benefit and durable results of osteochondral allograft (OCA) transplantation for the treatment of femoral condyle lesions. However, the majority of these studies are difficult to interpret owing to the mixed results of different techniques and anatomic locations.

PURPOSE

To evaluate the outcome of OCA transplantation with thin plug grafts for treatment of isolated femoral condyle osteochondral lesions.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

This study included 187 patients (200 knees) who underwent OCA transplantation for isolated osteochondral lesions on the femoral condyle between 1999 and 2014. For all cases, a thin plug technique was used with commercially available surgical instruments and the minimum amount of bone necessary for fixation. Evaluation included International Knee Documentation Committee score, Knee injury and Osteoarthritis Outcome Score, and patient satisfaction. Frequency and type of further surgery were assessed. Failure of the allograft was defined as further surgery involving removal of the allograft.

RESULTS

Mean follow-up was 6.7 years (range, 1.9-16.5 years). The mean age of patients at the time of surgery was 31 years, and 63% were male. The medial femoral condyle was affected in 69% of knees. A single thin plug graft was used in 145 knees (72.5%), and 2 grafts were used in 55 knees (27.5%). Mean allograft area was 6.3 cm², and graft thickness was 6.5 mm (cartilage and bone combined). Further surgery was required for 52 knees (26%), of which 16 (8% of entire cohort) were defined as allograft failures (4 OCA revisions, 1 arthrosurface, 6 unicompartmental knee arthroplasties, and 5 total knee arthroplasties). Median time to failure was 4.9 years. Survivorship of the allograft was 95.6% at 5 years and 91.2% at 10 years. Among patients with grafts remaining in situ at latest follow-up, clinically meaningful improvement in pain, function, and quality of life was reported. Satisfaction was reported by 89% of patients.

CONCLUSION

OCA transplantation with a thin plug graft technique is a valuable procedure for the treatment of femoral condyle osteochondral lesions, resulting in significant improvement in clinical scores, high patient satisfaction, and low reoperation and clinical failure rates.

Emerging therapies for cartilage regeneration in currently excluded 'red knee' populations

The field of articular cartilage repair has made significant advances in recent decades; yet current therapies are generally not evaluated or tested, at the time of pivotal trial, in patients with a variety of common comorbidities. To that end, we systematically reviewed cartilage repair clinical trials to identify common exclusion criteria and reviewed the literature to identify emerging regenerative approaches that are poised to overcome these current exclusion criteria. The term “knee cartilage repair” was searched on clinicaltrials.gov. Of the 60 trials identified on initial search, 33 were further examined to extract exclusion criteria. Criteria excluded by more than half of the trials were identified in order to focus discussion on emerging regenerative strategies that might address these concerns. These criteria included age (<18 or >55 years old), small defects (<1 cm²), large defects (>8 cm²), multiple defect (>2 lesions), BMI >35, meniscectomy (>50%), bilateral knee pathology, ligamentous instability, arthritis, malalignment, prior repair, kissing lesions, neurologic disease of lower extremities, inflammation, infection, endocrine or metabolic disease, drug or alcohol abuse, pregnancy, and history of cancer. Finally, we describe emerging tissue engineering and regenerative approaches that might foster cartilage repair in these challenging environments. The identified criteria exclude a majority of the affected population from treatment, and thus greater focus must be placed on these emerging cartilage regeneration techniques to treat patients with the challenging “red knee”.

The cost-effectiveness of osteochondral allograft transplantation in the knee

PURPOSE

Osteochondral allografts (OCA) consist of a layer of hyaline cartilage and a layer of underlying bone. They are used to repair combined defects of articular cartilage and bone. Such defects often occur in people far too young to have knee arthroplasty, for whom the main alternative to OCA is conservative symptomatic care, which will not prevent development of osteoarthritis. The aim of this report was to assess the cost-effectiveness of osteochondral allograft transplantation in the knee.

METHODS

Systematic review of evidence on clinical effectiveness and economic modelling.

RESULTS

The evidence on osteochondral allograft transplantation comes from observational studies, but often based on good quality prospective registries of all patients having such surgery. Without controlled trials, it was necessary to use historical cohorts to assess the effect of osteochondral grafts. There is good evidence that OCA are clinically effective with a high graft survival rate over 20 years. If an OCA graft fails, there is some evidence that revision with a second OCA is also effective, though less so than primary OCA. Economic modelling showed that osteochondral allograft transplantation was highly cost-effective, with costs per quality adjusted life year much lower than many other treatments considered cost effective.

CONCLUSIONS

Osteochondral allograft transplantation appears highly cost-effective though the cost per quality adjusted life year varies according to the widely varying costs of allografts. Based on one small study, revision OCA also appears very cost-effective, but more evidence is needed.

LEVEL OF EVIDENCE

II.

Bushenhuoxue Formula Facilitates Articular Cartilage Repair and Attenuates Matrix Degradation by Activation of TGF-β Signaling Pathway

Objective

To investigate the effect and underlying mechanism of Bushenhuoxue (BSHX) formula on articular cartilage repair.

Methods

Twenty-four full-thickness cartilage defect rats were divided into two groups: model group and BSHX group (treated with BSHX formula). Macroscopic observation and histopathological study were conducted after 4- and 8-week treatment. Additionally, we also evaluated chondrocyte proliferation, extracellular matrix (ECM) deposition, cartilage degradation, and chondrocyte hypertrophy-related genes expression in chondrogenic ATDC5 cells cultured in BSHX formula-mediated serum. Moreover, we assessed aforementioned genes expression and pSMAD2/3 protein level in Tgfβr2 siRNA transfected chondrogenic ATDC5 cells in order to address whether BSHX formula exerts cartilage repairing effect through TGF-β signaling.

Results

Neocartilage regeneration promotion effect was observed in cartilage defect rats after BSHX formula treatment, with increases in Col2 and pSMAD2 and decreases in Mmp13 and Runx2. Moreover, cell proliferation, the elevated Col2a1, Aggrecan and pSMAD2/3, reduced Mmp13, Adamts5, Col10a1, and Runx2 expression were also observed in chondrogenic ATDC5 cells cultured in BSHX formula-mediated serum. Besides, the expression alteration of ECM deposition, cartilage degradation, chondrocyte hypertrophy-related genes, and pSMAD2/3 protein levels presented in Tgfβr2 downregulated chondrogenic ATDC5 cells couldn't be adjusted by BSHX formula treatment.

Conclusion

By activation of TGF-β signaling, BSHX formula can promote articular cartilage repair by accelerating chondrocyte proliferation and maintaining chondrocyte phenotype, upregulate ECM accumulation, and inhibit matrix degradation.

Implication of antibodies against human leukocyte antigen in simultaneous presentation of fetal and neonatal alloimmune thrombocytopenia and neutropenia

Fetal and neonatal alloimmune thrombocytopenia (FNAIT) and neonatal alloimmune neutropenia (NAN) are two rare complications of newborns caused by antibodies against paternal inherited antigens. Human platelet (HPA) and neutrophil antigens (HNA) are the common targets. Human leukocyte antigen (HLA) class I proteins are also expressed on platelets and neutrophils and anti-HLA antibodies have occasionally been implicated in these complications. We report a premature twin infant who presented with severe thrombocytopenia and neutropenia clinically compatible with FNAIT and NAN, from a mother with no identifiable HPA or HNA antibodies, but with very high levels of complement-fixing antibodies against paternal inherited HLA. These antibodies were also detected in the infant. HLA antibodies are commonly present in multiparous women who deliver healthy infants. They can, however, be cytotoxic and cause clinical complications after blood products transfusion (TRALI and becoming refractory to platelets transfusion) and after organ transplantation (allogeneic organ rejection).

Rabbit xenogeneic transplantation model for evaluating human chondrocyte sheets used in articular cartilage repair

Research on cartilage regeneration has developed novel sources for human chondrocytes and new regenerative therapies, but appropriate animal models for translational research are needed. Although rabbit models are frequently used in such studies, the availability of immunocompromised rabbits is limited. Here, we investigated the usefulness of an immunosuppressed rabbit model to evaluate directly the efficacy of human chondrocyte sheets through xenogeneic transplantation. Human chondrocyte sheets were transplanted into knee osteochondral defects in Japanese white rabbits administered with immunosuppressant tacrolimus at a dosage of 0.8 or 1.6 mg/kg/day for 4 weeks. Histological evaluation at 4 weeks after transplantation in rabbits administered 1.6 mg/kg/day showed successful engraftment of human chondrocytes and cartilage regeneration involving a mixture of hyaline cartilage and fibrocartilage. No human chondrocytes were detected in rabbits administered 0.8 mg/kg/day, although regeneration of hyaline cartilage was confirmed. Histological evaluation at 12 weeks after transplantation (i.e., 8 weeks after termination of immunosuppression) showed strong immune rejection of human chondrocytes, which indicated that, even after engraftment, articular cartilage is not particularly immune privileged in xenogeneic transplantation. Our results suggest that Japanese white rabbits administered tacrolimus at 1.6 mg/kg/day and evaluated at 4 weeks may be useful as a preclinical model for the direct evaluation of human cell‐based therapies.

Osteochondral Allograft Transplantation and Opening Wedge Tibial Osteotomy: Clinical Results of a Combined Single Procedure

Objective To evaluate the outcome of patients who have undergone simultaneous osteotomy and osteochondral allograft (OCA) transplantation. Our hypothesis is that use of high tibial osteotomy and fresh OCA in a combined procedure is safe and effective without increasing morbidity in comparison to OCA alone. Design A case series of 17 patients underwent tibial osteotomy and simultaneous OCA during a single surgery. Osteotomy was indicated when axial alignment was within the affected compartment. Patients had a minimum of 2 years of follow-up after surgery. The mean graft size was 8.7 cm², with 82% located on the medial femoral condyle alone and 18% involving the medial femoral condyle and one or more other sites. Data collection included demographics, osteotomy correction, graft site(s) and area, and clinical evaluation. Failure was defined as conversion to arthroplasty. Results Two of 17 patients (12%) failed at a mean of 9.3 years. The remaining 15 patients (88%) had intact allografts with mean survival of 8.1 years (SD 3.3). Five patients (29%) had an additional procedure, all undergoing osteotomy hardware removal. Of those with surviving allografts, mean pain and function scores improved significantly from the preoperative to postoperative assessment and International Knee Documentation Committee total scores improved significantly from 40.9 ± 15.4 preoperative to 75.5 ± 24.0 at latest follow-up ( P = 0.003); 92% of patients were satisfied with the results of the surgery. No postoperative complications occurred. Conclusion Combining high tibial osteotomy and OCA in properly selected patients is safe and effective.

Tsmu solution improves rabbit osteochondral allograft preservation and transplantation outcome

To compare the effects of Tsmu solution with vitrification on chondrocyte viability and examine histological and biomechanical properties of osteochondral allografts (OCAs) after storage, OCAs from femoral condyles of New Zealand rabbits were harvested, stored for 35 days in Tsmu solution or by in vitro vitrification, and subjected to in vivo and in vitro assays. Stored OCAs were transplanted into knee femoral condyle cartilage defects in recipient rabbits. Chondrocyte viability and histological changes of cartilage grafts were assessed in vitro. Gross assessment, chondrocyte viability, histological assessment, OCA biomechanics, and immunological markers were evaluated in vivo 6 months after transplantation. Fresh OCAs served as in vitro and in vivo controls. Chondrocyte viability and scores for cartilage surface and histological quantitative assessment were superior for Tsmu solution compared with vitrification, but inferior compared with fresh OCAs in vitro and in vivo. With the exception of interleukin 6 content, biomechanical features of samples stored in Tsmu solution were superior to vitrification, and inferior to fresh OCAs in vivo. Thus, Tsmu solution provided suitable storage that improved chondrocyte viability, intact OCA cartilage matrix architecture, and transplantation outcomes.

Fresh Osteochondral Patellar Allograft Resurfacing

The treatment of articular cartilage lesions in young patients is certainly a complex matter and subject of continuous research, particularly for those located at the patellofemoral joint, given its peculiar biomechanical characteristics. Osteochondral grafts can be of relatively small size when the defect is focal and in an area that allows good stability and consequently the graft's integration. In case of large or multifocal lesions, it is possible to consider an osteochondral transplantation of the entire articular surface of the patella. We present a simple and reproducible technique to perform a patellar fresh osteochondral allograft resurfacing attempting to reduce the symptoms and delay a prosthetic implant in young patients with advanced patellar chondral injuries.

Editorial Commentary: To Treat or Not to Treat? Are We Any Closer to Knowing What to Do With Cartilage Lesions of the Tibia?

The increasing interest and use of cartilage repair procedures in the knee has led to a better understanding of when and how chondral lesions should be treated. Nonetheless, there are still key areas where we lack understanding and need better data to guide clinical decision making. One of these areas is how to manage lesions of the tibia, particularly when they occur in conjunction with the more commonplace lesions of the femoral condyle. In this setting, a tibial chondral lesion may reflect a bigger clinical problem-a "bipolar defect" or more advanced joint disease-"established osteoarthritis." My preferred treatment for these tibial lesions is to ignore the lesion (or perform a chondroplasty at most), except in cases of osteochondritis dissecans, focal defects in association with cysts, or tibial plateau fracture malunion.

Does Treatment of the Tibia Matter in Bipolar Chondral Defects of the Knee? Clinical Outcomes with Greater Than 2 Years Follow-up

PURPOSE

To compare the osteochondral allograft (OCA) outcomes of bipolar defects with isolated femoral defects and to investigate the optimal treatment of bipolar defects by comparing femoral OCA with tibial debridement to femoral OCA and tibial microfracture.

METHODS

A series of patients with 2-year follow-up from March 2004 to September 2015 after femoral OCA for bipolar chondral defects was identified. Group 1 contained patients with tibial defects treated with debridement and group 2 contained patients with microfractured tibial defects. A third group (group 3) with isolated femoral defects treated with OCA was identified and matched by gender, body mass index (BMI), laterality, and OCA size to groups 1 and 2. Patient-specific, defect-specific, intraoperative, and postoperative data including patient-reported outcomes were collected on all patients. The study groups were compared using analyses of variance, paired sample t tests, and χ-square analyses.

RESULTS

Thirty-six patients who had femoral OCA for bipolar lesions were identified with 20 patients in group 1 and 16 patients in group 2. Group 3 had 20 patients. There were no differences between the 3 groups in terms of gender (P = .616), BMI (P = .271), number of previous surgeries (P = .451), femoral or tibial defect size (P = .296), and OCA size (P = .981). Preoperative to postoperative patient-reported clinical outcomes (PROs) revealed statistical and clinically meaningful improvement in all 3 groups, but did not differ between groups. Patient-specific and defect-specific factors did not correlate with PROs. The graft survivorship for group 1 was 85% at 4.5 years, 100% for group 2 at 2.5 years, and 95% for group 3 at 3.8 years.

CONCLUSIONS

Regardless of tibial treatment, patients with bipolar defects treated with femoral OCA have clinically meaningful improvements in PROs and excellent graft survivorship comparable to isolated femoral OCAs at more than 2 years.

LEVEL OF EVIDENCE

Level III, case-control study.

Validation of the Missouri Osteochondral Allograft Preservation System for the Maintenance of Osteochondral Allograft Quality During Prolonged Storage

BACKGROUND

Fresh osteochondral allografts (OCAs) are limited in availability. The Missouri Osteochondral Allograft Preservation System (MOPS) has been reported to effectively preserve OCAs twice as long as current tissue bank protocols in preclinical studies.

HYPOTHESIS

The viable chondrocyte density (VCD) in OCAs preserved for up to 70 days using the MOPS will not be significantly different from day 0, and the VCD in MOPS-preserved OCAs will be significantly higher than for standard tissue bank preservation. Media changes during preservation will significantly improve the VCD.

STUDY DESIGN

Controlled laboratory study.

METHODS

Femoral condyles harvested from qualified donors (n = 12) were quartered (n = 48), assigned to 1 of 4 treatment groups (tissue bank protocol at 4°C or MOPS at 25°C, with or without media changes), and preserved for 0, 28, 56, or 70 days and assessed for the VCD and histopathological characteristics. In addition, osteochondral explants were created from the femoral condyles of 12 donors (n = 36 explants), assigned to the same groups and time points, and tested for biomechanical properties.

RESULTS

MOPS-preserved OCAs maintained the day 0 VCD through 56 days. OCAs stored using current tissue bank protocols had a significantly lower VCD compared with day 0 and the MOPS by day 28. OCA histological and biomechanical properties did not significantly change from day 0 for any group.

CONCLUSION

The MOPS preserved essential OCA viability and quality at significantly higher levels than current tissue bank protocols for at least 56 days after procurement.

CLINICAL RELEVANCE

Improving the viability and duration of OCA preservation provides potential benefits to tissue banks, donor families, surgeons, and patients with respect to tissue use, financial costs, and outcomes.

Promoted Chondrogenesis of Cocultured Chondrocytes and Mesenchymal Stem Cells under Hypoxia Using In-situ Forming Degradable Hydrogel Scaffolds

We investigated the effects of different oxygen tension (21% and 2.5% O₂) on the chondrogenesis of different cell systems cultured in pH-degradable PVA hydrogels, including human articular chondrocytes (hACs), human mesenchymal stem cells (hMSCs), and their cocultures with a hAC/hMSC ratio of 20/80. These hydrogels were prepared with vinyl ether acrylate-functionalized PVA (PVA-VEA) and thiolated PVA-VEA (PVA-VEA-SH) via Michael-type addition reaction. The rheology tests determined the gelation of the hydrogels was controlled within 2-7 min, dependent on the polymer concentrations. The different cell systems were cultured in the hydrogel scaffolds for 5 weeks, and the safranin O and GAG assay showed that hypoxia (2.5% O₂) greatly promoted the cartilage matrix production with an order of hAC > hAC/hMSC > hMSC. The real time quantitative PCR (RT-PCR) revealed that the hMSC group exhibited the highest hypertrophic marker gene expression (COL10A1, ALPL, MMP13) as well as the dedifferentiated marker gene expression (COL1A1) under normoxia conditions (21% O₂), while these expressions were greatly inhibited by coculturing with a 20% amount of hACs and significantly further repressed under hypoxia conditions, which was comparative to the sole hAC group. The enzyme-linked immunosorbent assay (ELISA) also showed that coculture of hMSC/hAC greatly reduced the catabolic gene expression of MMP1 and MMP3 compared with the hMSC group. It is obvious that the hypoxia conditions promoted the chondrogenesis of hMSC by adding a small amount of hACs, and also effectively inhibited their hypotrophy. We are convinced that coculture of hAC/hMSC using in situ forming hydrogel scaffolds is a promising approach to producing cell source for cartilage engineering without the huge needs of primary chondrocyte harvest and expansion.

Editorial Commentary: The Acellular Osteochondral Allograft, the Emperor Has New Clothes

For larger lesions (>2.5-cm²), clinical evidence and practice have shown that fresh osteochondral allograft have good durability, with 88% return to sport and greater than 75% 10-year survival rates for treatment of large femoral condyle lesions. That said, the use of fresh osteochondral allografts in clinical practice is limited by the availability of acceptable donor tissues for eligible patients in a timely fashion. Significant diminution of chondrocyte viability and density occurs during the preservation and storage period. All osteochondral allografts are not equal in performance and outcome. Chondrocyte density and viability are critical for successful transplantation and outcome in the short and long term. This commentary highlights the high failure rates of tissue when it is acellular.

Effects of Autogenous Bone Marrow Aspirate Concentrate on Radiographic Integration of Femoral Condylar Osteochondral Allografts

BACKGROUND

Transplantation of fresh osteochondral allografts (OCAs) is an attractive treatment option for symptomatic articular cartilage lesions in young, healthy patients. Because the lack of OCA bone integration can be a cause of treatment failure, methods for speeding and enhancing OCA bone integration to mitigate this potential complication are highly desirable.

PURPOSE

To determine if autogenous bone marrow aspirate concentrate (BMC) treatment of large femoral condylar OCAs would be associated with superior radiographic OCA bone integration compared with nontreated allografts during the critical first 6 months after surgery.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

A review of patients enrolled in a prospective registry who were treated with transplantation of large OCAs to one or both femoral condyles at our institution from March 12, 2013 to March 14, 2016 was performed. Patients were stratified into 2 groups based on BMC treatment versus no BMC treatment; the treatment was nonrandomized and was rooted in a shift in practice and a continuing effort to optimize OCA transplantation at our institution. Patients were excluded if they did not have orthogonal view radiographs performed at 6 weeks, 3 months, and 6 months postoperatively. Each condyle undergoing OCA transplantation was assessed individually by an independent musculoskeletal radiologist, who was blinded to the treatment group and time point. OCAs were assessed with respect to graft integration (0%-100%; 0 = no integration, 100 = complete integration) and degree of sclerosis (0-3; 0 = normal, 1 = mild sclerosis, 2 = moderate sclerosis, and 3 = severe sclerosis) of the graft at each time point.

RESULTS

This study identified 17 condyles in 15 patients who underwent OCA transplantation without BMC and 29 condyles in 22 patients who underwent OCA transplantation with BMC. The BMC group had significantly ( P = .033) higher graft integration scores at 6 weeks, 3 months, and 6 months after surgery. Graft sclerosis was significantly ( P = .017) less in the BMC group at 6 weeks and 3 months, with no significant difference at 6 months after surgery. When combining the groups to examine the influence of smoking on graft integration, nonsmokers had significantly ( P = .007) higher graft integration scores at 6 months.

CONCLUSION

Large femoral condylar OCAs treated with autogenous BMC before implantation showed superior radiographic integration to bone and less sclerosis during the initial 6-month postoperative period. BMC treatment of OCAs may mitigate the failure of OCA bone healing.

Fresh Osteochondral Allograft Transplantation: Is Graft Storage Time Associated With Clinical Outcomes and Graft Survivorship?

BACKGROUND

Regulatory concerns and the popularity of fresh osteochondral allograft (OCA) transplantation have led to a need for prolonged viable storage of osteochondral grafts. Tissue culture media allow a longer storage time but lead to chondrocyte death within the tissue. The long-term clinical consequence of prolonged storage is unknown.

HYPOTHESIS

Patients transplanted with OCAs with a shorter storage time would have lower failure rates and better clinical outcomes than those transplanted with OCAs with prolonged storage.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

A matched-pair study was performed of 75 patients who received early release grafts (mean storage, 6.3 days [range, 1-14 days]) between 1997 and 2002, matched 1:1 by age, diagnosis, and graft size, with 75 patients who received late release grafts (mean storage time, 20.0 days [range, 16-28 days]) from 2002 to 2008. The mean age was 33.5 years, and the median graft size was 6.3 cm². All patients had a minimum 2-year follow-up. Evaluations included pain, satisfaction, function, failures, and reoperations. Outcome measures included the modified Merle d'Aubigné-Postel (18-point) scale, International Knee Documentation Committee (IKDC) form, and Knee Society function (KS-F) scale. Clinical failure was defined as revision OCA transplantation or conversion to arthroplasty.

RESULTS

Among patients with grafts remaining in situ, the mean follow-up was 11.9 years (range, 2.0-16.8 years) and 7.8 years (range, 2.3-11.1 years) for the early and late release groups, respectively. OCA failure occurred in 25.3% (19/75) of patients in the early release group and 12.0% (9/75) of patients in the late release group ( P = .036). The median time to failure was 3.5 years (range, 1.7-13.8 years) and 2.7 years (range, 0.3-11.1 years) for the early and late release groups, respectively. The 5-year survivorship of OCAs was 85% for the early release group and 90% for the late release group ( P = .321). No differences in postoperative pain and function were noted between the groups. Ninety-one percent of the early release group and 93% of the late release group reported satisfaction with OCA results.

CONCLUSION

The transplantation of OCA tissue with prolonged storage is safe and effective for large osteochondral lesions of the knee and has similar clinical outcomes and satisfaction to the transplantation of early release grafts.

Lactated Ringer-based storage solutions are equally well suited for the storage of fresh osteochondral allografts as cell culture medium-based storage solutions

BACKGROUND

Due to the rising interest in Europe to treat large cartilage defects with osteochondrale allografts, research aims to find a suitable solution for long-term storage of osteochondral allografts. This is further encouraged by the fact that legal restrictions currently limit the use of the ingredients from animal or human sources that are being used in other regions of the world (e.g. in the USA). Therefore, the aim of this study was A) to analyze if a Lactated Ringer (LR) based solution is as efficient as a Dulbecco modified Eagle's minimal essential medium (DMEM) in maintaining chondrocyte viability and B) at which storage temperature (4°C vs. 37°C) chondrocyte survival of the osteochondral allograft is optimally sustained.

METHODS

300 cartilage grafts were collected from knees of ten one year-old Black Head German Sheep. The grafts were stored in four different storage solutions (one of them DMEM-based, the other three based on Lactated Ringer Solution), at two different temperatures (4 and 37°C) for 14 and 56days. At both points in time, chondrocyte survival as well as death rate, Glycosaminoglycan (GAG) content, and Hydroxyproline (HP) concentration were measured and compared between the grafts stored in the different solutions and at the different temperatures.

RESULTS

Independent of the storage solutions tested, chondrocyte survival rates were higher when stored at 4°C compared to storage at 37°C both after short-term (14days) and long-term storage (56days). At no point in time did the DMEM-based solution show a superior chondrocyte survival compared to lactated Ringer based solution. GAG and HP content were comparable across all time points, temperatures and solutions.

CONCLUSION

LR based solutions that contain only substances that are approved in Germany may be just as efficient for storing grafts as the USA DMEM-based solution gold standard. Moreover, in the present experiment storage of osteochondral allografts at 4°C was superior to storage at 37°C.

Review of Mechanical, Processing, and Immunologic Factors Associated With Outcomes of Fresh Osteochondral Allograft Transplantation of the Talus

Osteochondral lesions of the talus (OLTs) are an increasingly implicated cause of ankle pain and instability. Several treatment methods exist with varying clinical outcomes. Due in part to successful osteochondral allografting (OCA) in other joints, such as the knee and shoulder, OCA has gained popularity as a treatment option, especially in the setting of large lesions. The clinical outcomes of talar OCA have been inconsistent relative to the positive results observed in other joints. Current literature regarding OCA failure focuses mainly on 3 factors: the effect of graft storage conditions on chondrocyte viability, graft/lesion size, and operative technique. Several preclinical studies have demonstrated the ability for bone and cartilage tissue to invoke an immune response, and a limited number of clinical studies have suggested that this response may have the potential to influence outcomes after transplantation. Further research is warranted to investigate the role of immunological mechanisms as an etiology of OCA failure.

LEVEL OF EVIDENCE

Level V, expert opinion.

Two-stage late reconstruction with a fresh large osteochondral shell allograft transplantation (FLOCSAT) for a large ostechondral defect in a non-union after a lateral tibia plateau fracture 2-year follow up

This is the description of a 58-year-old female patient presenting 8 months after a horse riding accident with significant pain and inability to walk independently. Imaging revealed a large osseous defect of the lateral tibia plateau which was not united posteriorly. The patient refused knee replacement and we developed a patient specific two-step procedure for her. Step 1: Filling of the defect with a large cortico-cancellous autograft from the posterior iliac crest; step 2: Transplantation of a fresh large osteochondral shell allograft (FLOCSAT). The postoperative protocol included continuous passive motion (CPM), partial weight bearing for three months, and physiotherapy. Based on the concept of immuno-privileged cartilage tissue, the patient did not get any immuno-suppressive therapy. Pain-, activity of daily living, Lysholm and Tegner scores were evaluated before defect filling surgery with autograft, before allograft transplantation, and at 12 and 24 months after allograft transplantation. There were no complications. Radiographic analyses with plain films and CT scans revealed solid osseous integration within 3 month. The patient regained excellent functionality in both, activities of daily living and sports (back to horse riding, trampolin jumping). Knee arthroscopy after 1year showed excellent condition of the lateral meniscus and the cartilage of the lateral tibia plateau. Chimerism/DNA analysis of a cartilage biopsy showed, that at 1year 32% of the donor cells have been already replaced by the patient's own cells. To our knowledge, this is the first case of a patient who sustained such a large defect during a tibia plateau fracture, and got successfully treated with a fresh large osteochondral shell allograft transplantation in a two-step procedure.

Joint Preservation Techniques in Orthopaedic Surgery

CONTEXT

With increasing life expectancy, there is growing demand for preservation of native articular cartilage to delay joint arthroplasties, especially in younger, active patients. Damage to the hyaline cartilage of a joint has a limited intrinsic capacity to heal. This can lead to accelerated degeneration of the joint and early-onset osteoarthritis. Treatment in the past was limited, however, and surgical treatment options continue to evolve that may allow restoration of the natural biology of the articular cartilage. This article reviews the most current literature with regard to indications, techniques, and outcomes of these restorative procedures.

EVIDENCE ACQUISITION

MEDLINE and PubMed searches relevant to the topic were performed for articles published between 1995 and 2016. Older articles were used for historical reference. This paper places emphasis on evidence published within the past 5 years.

STUDY DESIGN

Clinical review.

LEVEL OF EVIDENCE

Level 4.

RESULTS

Autologous chondrocyte implantation and osteochondral allografts (OCAs) for the treatment of articular cartilage injury allow restoration of hyaline cartilage to the joint surface, which is advantageous over options such as microfracture, which heal with less favorable fibrocartilage. Studies show that these techniques are useful for larger chondral defects where there is no alternative. Additionally, meniscal transplantation can be a valuable isolated or adjunctive procedure to prolong the health of the articular surface.

CONCLUSION

Newer techniques such as autologous chondrocyte implantation and OCAs may safely produce encouraging outcomes in joint preservation.

Allografts: Osteochondral, Shell, and Paste

There is an increasing need for articular cartilage restoration procedures. Hyaline cartilage lacks intrinsic healing capacity. Persistent osteochondral defects can lead to early and rapid degenerative changes. Microfracture and autologous chondrocyte implantation provide reasonable outcomes for smaller defects without bone loss. However, these techniques have limited effectiveness for lesions greater than 4 cm² or with significant bony involvement. Ostochondral allografts provide an option for these lesions. This article reviews osteochondral allografts for articular defects. Emerging options provide different approaches to difficult cartilage defects. We discuss current screening, procurement, and storage methods, surgical techniques, outcomes, and bacterial/viral transmission.

Pulsed lavage cleansing of osteochondral grafts depends on lavage duration, flow intensity, and graft storage condition

Introduction

Osteochondral allograft (OCA) transplantation is generally effective for treating large cartilage lesions. Cleansing OCA subchondral bone to remove donor marrow elements is typically performed with pulsed lavage. However, the effects of clinical and experimental parameters on OCA marrow removal by pulsed lavage are unknown. The aim of the current study was to determine the effects on marrow cleansing in human osteochondral cores (OCs) of (1) lavage duration, (2) lavage flow intensity, and (3) OC sample type and storage condition.

Methods

OCs were harvested from human femoral condyles and prepared to a clinical geometry (cylinder, diameter = 20 mm). The OCs were from discarded remnants of Allograft tissues (OCA) or osteoarthritis patients undergoing Total Knee Replacement (OCT). The experimental groups subjected to standard flow lavage for 45 seconds (430 mL of fluid) and 120 seconds (1,150 mL) were (1) OCT/FROZEN (stored at -80°C), (2) OCT/FRESH (stored at 4°C), and (3) OCA/FRESH. The OCA/FRESH group was subsequently lavaged at high flow for 45 seconds (660 mL) and 120 seconds (1,750 mL). Marrow cleansing was assessed grossly and by micro-computed tomography (μCT).

Results

Gross and μCT images indicated that marrow cleansing progressed from the OC base toward the cartilage. Empty marrow volume fraction (EMa.V/Ma.V) increased between 0, 45, and 120 seconds of standard flow lavage, and varied between groups, being higher after FROZEN storage (86–92% after 45–120 seconds) than FRESH storage of either OCT or OCA samples (36% and 55% after 45 and 120 seconds, respectively). With a subsequent 120 seconds of high flow lavage, EMa.V/Ma.V of OCA/FRESH samples increased from 61% to 78%.

Conclusions

The spatial and temporal pattern of marrow space clearance was consistent with gradual fluid-induced extrusion of marrow components. Pulsed lavage of OCAs with consistent time and flow intensity will help standardize marrow cleansing and may improve clinical outcomes.

Osteochondral Allograft Transplantation of the Knee: Analysis of Failures at 5 Years

BACKGROUND

Osteochondral allograft transplantation (OAT) is being performed with increasing frequency, and the need for reoperations is not uncommon.

PURPOSE

To quantify survival for OAT and report findings at reoperations.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

A review of prospectively collected data of 224 consecutive patients who underwent OAT by a single surgeon with a minimum follow-up of 2 years was conducted. The reoperation rate, timing of reoperation, procedure performed, and findings at surgery were reviewed. Failure was defined by revision OAT, conversion to knee arthroplasty, or gross appearance of graft failure at second-look arthroscopic surgery.

RESULTS

A total of 180 patients (mean [±SD] age, 32.7 ± 10.4 years; 52% male) who underwent OAT with a mean follow-up of 5.0 ± 2.7 years met the inclusion criteria (80% follow-up). Of these, 172 patients (96%) underwent a mean of 2.5 ± 1.7 prior surgical procedures on the ipsilateral knee before OAT. Forty-eight percent of OAT procedures were isolated, while 52% were performed with concomitant procedures including meniscus allograft transplantation (MAT) in 65 (36%). Sixty-six patients (37%) underwent a reoperation at a mean of 2.5 ± 2.5 years, with 32% (21/66) undergoing additional reoperations (range, 1-3). Arthroscopic debridement was performed in 91% of patients with initial reoperations, with 83% showing evidence of an intact graft; of these, 9 ultimately progressed to failure at a mean of 4.1 ± 1.9 years. A total of 24 patients (13%) were considered failures at a mean of 3.6 ± 2.6 years after the index OAT procedure because of revision OAT (n = 7), conversion to arthroplasty (n= 12), or appearance of a poorly incorporated allograft at arthroscopic surgery (n = 5). The number of previous surgical procedures was independently predictive of reoperations and failure; body mass index was independently predictive of failure. Excluding the failed patients, statistically and clinically significant improvements were found in the Lysholm score, International Knee Documentation Committee score, Knee injury and Osteoarthritis Outcome Score, and Short Form-12 physical component summary at final follow-up ( P < .001 for all), with inferior outcomes (albeit overall improved) in patients who underwent a reoperation.

CONCLUSION

In this series, there was a 37% reoperation rate and an 87% allograft survival rate at a mean of 5 years after OAT. The number of previous ipsilateral knee surgical procedures was predictive of reoperations and failure. Of the patients who underwent arthroscopic debridement with an intact graft at the time of arthroscopic surgery, 82% experienced significantly improved outcomes, while 18% ultimately progressed to failure. This information can be used to counsel patients on the implications of a reoperation after OAT.

The effects of low-dose radiotherapy on fresh osteochondral allografts: An experimental study in rabbits

Objective

The aim of this study was to investigate the effects of low-dose fractionated radiotherapy on cartilage degeneration after distal femoral fresh massive osteochondral allograft transplantation.

Methods

Twenty-four New Zealand White rabbits were divided into three groups of 8 rabbits each. All rabbits underwent distal femoral medial condyle fresh massive osteochondral allograft transplantation from California rabbits. The group 1 underwent transplantation without any preliminary process. The group 2 underwent fractionated local radiotherapy of 100 cGy for five days starting on the transplantation day. The group 3 included the rabbits to which the grafts transplanted after radiating in vitro by a single dose radiation of 1500 cGy. The hosts were sacrificed twelve weeks later. Anteroposterior and lateral radiographs were taken. Synovial tissue, cartilaginous tissue, and subchondral bone were assessed histopathologically.

Results

Nonunion was present in three cases of group 2 and one of group 3 in which cartilage degeneration was more severe. Synovial hypertrophy and pannus formation were more obvious in non-radiated rabbits. Hypocellularity and necrosis of the subchondral bone were rare in group 2. More cartilage tissue impairment was present in group 3 compared to group 1.

Conclusion

In osteochondral massive allograft transplantations, the immune reaction of the host could be precluded with radiotherapy, and the side-effects can be prevented by low-dose fractionated regimen. The total dose of fractionated radiotherapy for an immune suppression should be adjusted not to damage the cartilage tissue, but to avoid articular degeneration in the long term.