A novel system improves preservation of osteochondral allografts

Osteochondral Allograft Reaming Significantly Affects Chondrocyte Viability

BACKGROUND

Chondrocyte viability is associated with the clinical success of osteochondral allograft (OCA) transplantation.

PURPOSE

To investigate the effect of distal femoral OCA plug harvest and recipient site preparation on regional cell viability using traditional handheld saline irrigation versus saline submersion.

STUDY DESIGN

Controlled laboratory study.

METHODS

For each of 13 femoral hemicondyles, 4 cartilage samples were harvested: (1) 5-mm control cartilage, (2) 15-mm OCA donor plug harvested with a powered coring reamer and concurrent handheld saline irrigation ("traditional"), (3) 15-mm OCA donor plug harvested while submerged under normal saline ("submerged"), and (4) 5-mm cartilage from the peripheral rim of a recipient socket created with a 15-mm cannulated counterbore reamer to a total depth of 7 mm with concurrent handheld saline irrigation ("recipient"). The 15 mm-diameter plugs were divided into the central 5 mm and the peripheral 5 mm (2 edges) for comparisons. Samples were stained using calcein and ethidium, and live/dead cell percentages were calculated and compared across groups.

RESULTS

Compared with the submerged group, the traditional group had significantly lower percentages of live cells across the whole plug (71.54% ± 4.82% vs 61.42% ± 4.98%, respectively; P = .003), at the center of the plug (72.76% ± 5.87% vs 62.30% ± 6.11%, respectively; P = .005), and at the periphery of the plug (70.93% ± 4.51% vs 60.91% ± 4.75%, respectively; P = .003). The traditional group had significantly fewer live cells in all plug regions compared with the control group (77.51% ± 9.23%; P < .0001). There were no significant differences in cell viability between the control and submerged groups (whole: P = .590; center: P = .713; periphery: P = .799). There were no differences between the central and peripheral 5-mm plug regions for the traditional (62.30% ± 6.11% vs 60.91% ± 4.75%, respectively; P = .108) and submerged (72.76% ± 5.87% vs 70.93% ± 4.51%, respectively; P = .061) groups. The recipient group (61.10% ± 5.02%) had significantly lower cell viability compared with the control group (P < .0001) and the periphery of the submerged group (P = .009) but was equivalent to the periphery of the traditional group (P = .990).

CONCLUSION

There was a significant amount of chondrocyte death induced by OCA donor plug harvesting using a powered coring reamer with traditional handheld saline irrigation, which was mitigated by harvesting the plug while the allograft was submerged under saline.

CLINICAL RELEVANCE

Mitigating this thermally induced damage by harvesting the OCA plug while the allograft was submerged in saline maintained chondrocyte viability throughout the plug and may help to improve the integration and survival of OCAs.

Cell-Mediated Immune Responses May Play Roles in Osteochondral Allograft Transplantation Osteointegration Failures

Prolonged and incomplete osteochondral allograft (OCA) osteointegration is consistently cited as a major mechanism for OCA treatment failure. Subrejection immune responses may play roles in this mode of failure. Preimplantation OCA preparation techniques, including subchondral bone drilling, thorough irrigation, and autogenous bone marrow aspirate concentrate saturation, may dampen immune responses and improve OCA osteointegration. This study sought to further characterize potential immune system contributions to OCA transplantation treatment failures by analyzing donor-recipient ABO and Rh-factor mismatches and histological and immunohistochemical assessments of transplanted OCA tissues recovered from revision surgeries. Using a dedicated registry, OCA transplant recipients with documented treatment failures who met inclusion criteria (n = 33) as well as age-, body mass index-, and joint-matched patients with successful outcomes (n = 70) were analyzed to compare matched cohorts of patients with successful versus failed OCA transplantation outcomes. Tissues recovered from 18 failed OCA transplants and portions of 7 nonimplanted OCA controls were further analyzed to provide contributing evidence for potential immune response mechanisms. For patients analyzed, no statistically significant differences in proportions for treatment success versus failure based on mismatches for ABO type, Rh factor, or both were noted. Further, no statistically significant differences in proportions for histological immune response presence or absence based on mismatches for ABO type, Rh factor, or both were noted. Twelve (67%) of the failed OCA tissues contained lymphocyte aggregations in the subchondral bone, which were comprised of combinations of CD3 + , CD4 + , CD8 + , and CD20+ lymphocytes. The mechanisms of failure for these 12 OCA transplants involved insufficient OCA osteointegration. Results of this study suggest that T- and B-cell-mediated subrejection immune responses may play roles in OCA transplant treatment failures independent of donor-recipient blood type mismatch effects.

Ex vivo storage of human osteochondral allografts: Long-term analysis over 300 days using a Ringer-based solution

Large osteochondral defects are a major challenge in orthopedics, for which osteochondral allograft (OCA) transplantation is nowadays considered as an option, especially in young patients. However, a major issue with OCA is the need for graft storage, which ensures adequate cartilage integrity over time. The aim of this study was to test how long a Ringer-based storage solution can provide good graft quality after explantation and thus meet the requirements for OCA. For this purpose, human osteochondral allografts of the knee and ankle were analyzed. Live/Dead analysis was performed and glycosaminoglycan, as well as hydroxyproline content, were measured as crucial chondrocyte integrity factors. Furthermore, biomechanical tests focusing on stress relaxation and elastic compression modulus were performed. The critical value of 70% living chondrocytes, which corresponds to a number of 300 cells/mm², was reached after an average of 16 weeks of storage. In addition, a constant cell shrinkage was observed over time. The amount of glycosaminoglycan and hydroxyroline showed a slight and constant decrease over time, but no significant differences when compared from Day 0 to the values at Weeks 40-43. Biomechanical testing also revealed no significant differences at the different time points. Therefore, the results show that the Ringer-based storage solution at 4°C is able to provide a chondrocyte survival of 70% until Week 16. This is comparable to previously published storage solutions. Therefore, the study contributes to the establishment of a Ringer-based osteochondral allograft transplantation system for countries where medium-based storage solution cannot be approved.

Effect of Press-Fit Size on Insertion Mechanics and Cartilage Viability in Human and Ovine Osteochondral Grafts

OBJECTIVE

The osteochondral allograft procedure uses grafts constructed larger than the recipient site to stabilize the graft, in what is known as the press-fit technique. This research aims to characterize the relationships between press-fit size, insertion forces, and cell viability in ovine and human osteochondral tissue.

DESIGN

Human (4 donors) and ovine (5 animals) articular joints were used to harvest osteochondral grafts (4.55 mm diameter, N = 33 Human, N = 35 Ovine) and create recipient sites with grafts constructed to achieve varying degrees of press fit (0.025-0.240 mm). Donor grafts were inserted into recipient sites while insertion forces were measured followed by quantification of chondrocyte viability and histological staining to evaluate the extracellular matrix.

RESULTS

Both human and ovine tissues exhibited similar mechanical and cellular responses to changes in press-fit. Insertion forces (Human: 3-169 MPa, Ovine: 36-314 MPa) and cell viability (Human: 16%-89% live, Ovine: 2%-76% live) were correlated to press-fit size for both human (force: r = 0.539, viability: r = -0.729) and ovine (force: r = 0.655, viability: r = -0.714) tissues. In both species, a press-fit above 0.14 mm resulted in reduced cell viability below a level acceptable for transplantation, increased insertion forces, and reduced linear correlation to press-fit size compared to samples with a press-fit below 0.14 mm.

CONCLUSIONS

Increasing press-fit size required increased insertion forces and resulted in reduced cell viability. Ovine and human osteochondral tissues responded similarly to impact insertion and varying press-fit size, providing evidence for the use of the ovine model in allograft-related research.

High-Speed Centrifugation Efficiently Removes Immunogenic Elements in Osteochondral Allografts

OBJECTIVES

The current clinical pulse lavage technique for flushing fresh osteochondral allografts (OCAs) to remove immunogenic elements from the subchondral bone is ineffective. This study aimed to identify the optimal method for removing immunogenic elements from OCAs.

METHODS

We examined five methods for the physical removal of immunogenic elements from OCAs from the femoral condyle of porcine knees. We distributed the OCAs randomly into the following seven groups: (1) control, (2) saline, (3) ultrasound, (4) vortex vibration (VV), (5) low-pulse lavage (LPL), (6) high-pulse lavage (HPL), and (7) high-speed centrifugation (HSC). OCAs were evaluated using weight measurement, micro-computed tomography (micro-CT), macroscopic and histological evaluation, DNA quantification, and chondrocyte activity testing. Additionally, the subchondral bone was zoned to assess the bone marrow and nucleated cell contents. One-way ANOVA and paired two-tailed Student's t-test are used for statistical analysis.

RESULTS

Histological evaluation and DNA quantification showed no significant reduction in marrow elements compared to the control group after the OCAs were treated with saline, ultrasound, or VV treatments; however, there was a significant reduction in marrow elements after LPL, HPL, and HSC treatments. Furthermore, HSC more effectively reduced the marrow elements of OCAs in the middle and deep zones compared with LPL (p < 0.0001) and HPL (p < 0.0001). Macroscopic evaluation revealed a significant reduction in blood, lipid, and marrow elements in the subchondral bone after HSC. Micro-CT, histological analyses, and chondrocyte viability results showed that HSC did not damage the subchondral bone and cartilage; however, LPL and HPL may damage the subchondral bone.

CONCLUSION

HSC may play an important role in decreasing immunogenicity and therefore potentially increasing the success of OCA transplantation.

Characterizing Osteochondral Allograft Biomechanics for Optimizing Transplant Success: A Systematic Review

Osteochondral allograft (OCA) transplantation has been largely successful in treating symptomatic articular cartilage lesions; however, treatment failures persist. While OCA biomechanics have been consistently cited as mechanisms of treatment failure, the relationships among mechanical and biological variables that contribute to success after OCA transplantation have yet to be fully characterized. The purpose of this systematic review was to synthesize the clinically relevant peer-reviewed evidence targeting the biomechanics of OCAs and the impact on graft integration and functional survival toward developing and implementing strategies for improving patient outcomes. The Cochrane Central Register of Controlled Trials, the Cochrane Database of Systematic Reviews, MEDLINE, PubMed, Cumulative Index to Nursing and Allied Health (CINAHL), Google Scholar, and EMBASE were searched to identify articles for systematic review. This review of relevant peer-reviewed literature provided evidence that the biomechanics related to OCA transplantation in the knee have direct and indirect effects on functional graft survival and patient outcomes. The evidence suggests that biomechanical variables can be optimized further to enhance benefits and mitigate detrimental effects. Each of these modifiable variables should be considered regarding indications, patient selection criteria, graft preservation methodology, graft preparation, transplantation, fixation techniques, and prescribed postoperative restriction and rehabilitation protocols. Criteria, methods, techniques, and protocols should target OCA quality (chondrocyte viability, extracellular matrix integrity, material properties), favorable patient and joint characteristics, rigid fixation with protected loading, and innovative ways to foster rapid and complete OCA cartilage and bone integration to optimize outcomes for OCA transplant patients.

Novel Allograft in the Load-Bearing Portion of the Femoral Head

Background: An osteochondral defect in the hip can be a painful and limiting pathologic process. The damaged joint may progress into premature osteoarthritis, further limiting a patient's functionality. Case Report: A 24-year-old male presented to the clinic with left hip pain. The patient had been involved in a motor vehicle accident 3 years prior to presentation to our clinic. His injury from the high-speed accident required intramedullary rod fixation for a right-sided (contralateral) subtrochanteric femur fracture. The patient complained of left groin pain when in a sitting position, with activities of daily living, and with exercise. He failed conservative management consisting of nonsteroidal anti-inflammatory drugs and physical therapy. Imaging on presentation demonstrated an osteochondral defect in the weight-bearing portion of the left femoral head consistent with an International Cartilage Repair Society grade 4b lesion, a cam lesion was noted on assessment of bone morphology, and magnetic resonance imaging revealed degenerative labral pathology. The patient was treated with surgical hip dislocation through a modified Hardinge approach, femoral head osteochondral allograft transplantation using a Missouri Osteochondral Preservation System (MOPS) graft, acetabuloplasty, femoral neck osteoplasty, and open labral repair. Conclusion: Femoral head osteochondral MOPS allograft transplantation is a viable technique for joint preservation in young patients with posttraumatic osteochondral defects of the femoral head.

Engaging Patients and Caregivers to Develop a Patient-Centered Agenda for Comparative Effectiveness Research Focused on the Treatment of Complex Knee Problems

Complex articular cartilage loss in the knee is being diagnosed more frequently and earlier in life, and patients are faced with major decisions regarding invasive surgical interventions at increasingly younger ages. There is a critical unmet need to provide patient-centered comparative effectiveness research for the hundreds of thousands of patients faced with these treatment decisions each year. Toward filling the need, we developed the Patient AdvisoR Team iN Orthopaedic ReSearch (PARTNORS) program. We recruited a diverse group of patients and caregivers with lived experiences in dealing with complex knee problems to define patient-centered research priorities for comparative biological and artificial knee surgery research for middle-aged adults. Adapting the Stakeholder Engagement in Question Development and Prioritization Method, PARTNORS defined a 20-question list of patient-centered research questions of factors influencing a patients' choice between biological and artificial knee surgeries. The highest prioritized research question related to functional level postsurgery as it relates to daily activities and recreational activities. The second highest prioritized research questions related to insurance coverage and financial costs. Other prioritized research areas included caregiving needs, implant longevity, recovery and rehabilitation time, patient satisfaction and success rates, individual characteristics, and risks. By engaging a group of patients and caregivers and including them as members of a multidisciplinary research team, comparative effectiveness research that includes patient-centered factors that go beyond typical clinical success indicators for knee surgery can be designed to allow physicians and patients to work together toward evidence-based shared decisions. This shared decision-making process helps to align patients' and health care team's goals and expectations to improve outcomes.

Knee Cartilage Lesion Management-Current Trends in Clinical Practice

Many patients, particularly those aged above 40, experience knee joint pain, which hampers both sports activities and daily living. Treating isolated chondral and osteochondral defects in the knee poses a significant clinical challenge, particularly in younger patients who are not typically recommended partial or total knee arthroplasty as alternatives. Several surgical approaches have been developed to address focal cartilage defects. The treatment strategies are characterized as palliation (e.g., chondroplasty and debridement), repair (e.g., drilling and microfracture), or restoration (e.g., autologous chondrocyte implantation, osteochondral autograft, and osteochondral allograft). This review offers an overview of the commonly employed clinical methods for treating articular cartilage defects, with a specific focus on the clinical trials conducted in the last decade. Our study reveals that, currently, no single technology fully meets the essential requirements for effective cartilage healing while remaining easily applicable during surgical procedures. Nevertheless, numerous methods are available, and the choice of treatment should consider factors such as the location and size of the cartilage lesion, patient preferences, and whether it is chondral or osteochondral in nature. Promising directions for the future include tissue engineering, stem cell therapies, and the development of pre-formed scaffolds from hyaline cartilage, offering hope for improved outcomes.

Current and Novel Therapeutics for Articular Cartilage Repair and Regeneration

Articular cartilage repair is a sophisticated process that has is being recently investigated. There are several different approaches that are currently reported to promote cartilage repair, like cell-based therapies, biologics, and physical therapy. Cell-based therapies involve the using stem cells or chondrocytes, which make up cartilage, to promote the growth of new cartilage. Biologics, like growth factors, are also being applied to enhance cartilage repair. Physical therapy, like exercise and weight-bearing activities, can also be used to promote cartilage repair by inducing new cartilage growth and improving joint function. Additionally, surgical options like osteochondral autograft, autologous chondrocyte implantation, microfracture, and others are also reported for cartilage regeneration. In the current literature review, we aim to provide an up-to-date discussion about these approaches and discuss the current research status.

Editorial Commentary: Shell Grafts Are Viable in "Select" Cases, and Improved Preservation Techniques May Help Us Improve Our Outcomes

Patellofemoral joint chondral lesions can be challenging to treat with osteochondral allograft plugs because of the complex morphology and biomechanics of the patellofemoral joint Shell allografts replace the entirety of the damaged articular surface with a single osteochondral allograft piece (e.g., the entire trochlea or patella articular surface). Although technically demanding, shell grafts would allow for the treatment of bigger defects, correction of dysplasia, and for the treatment of uncontained lesions. However, shell allografts have historically shown inferior results than focal cylindrical grafts (bone plugs), with failure rates up to 38% based in the published literature. Although evidence exists demonstrating the efficacy of shell grafts in select cases, additional studies from multiple sources are required to support their continued use as well as determine the optimal graft-preservation techniques.

Variability in the Processing of Fresh Osteochondral Allografts

The indications for fresh osteochondral allograft continue to increase. As a result, variations in graft processing and preservation methods have emerged. An understanding of these techniques is important when evaluating the optimal protocol for processing fresh osteochondral allografts prior to surgical implantation. The aim of this study is to review the literature and understand various tissue processing protocols of four leading tissue banks in the United States. Donor procurement, serological and microbiological testing, and storage procedures were compared among companies of interest. Similarities between the major tissue banks include donor screening, aseptic processing, and testing for microorganisms. Variability exists between these companies with relation to choice of storage media, antibiotic usage, storage temperature, and graft expiration dates. Potential exists for increased chondrocyte viability and lengthened time-to-expiration of the graft through a protocol of delicate tissue handling, proper choice of storage medium, adding hormones and growth factors like insulin growth factor-1 (IGF-1) to serum-free nutrient media, and storing these grafts closer to physiologic temperatures.

Progress and prospect of technical and regulatory challenges on tissue-engineered cartilage as therapeutic combination product

Hyaline cartilage plays a critical role in maintaining joint function and pain. However, the lack of blood supply, nerves, and lymphatic vessels greatly limited the self-repair and regeneration of damaged cartilage, giving rise to various tricky issues in medicine. In the past 30 years, numerous treatment techniques and commercial products have been developed and practiced in the clinic for promoting defected cartilage repair and regeneration. Here, the current therapies and their relevant advantages and disadvantages will be summarized, particularly the tissue engineering strategies. Furthermore, the fabrication of tissue-engineered cartilage under research or in the clinic was discussed based on the traid of tissue engineering, that is the materials, seed cells, and bioactive factors. Finally, the commercialized cartilage repair products were listed and the regulatory issues and challenges of tissue-engineered cartilage repair products and clinical application would be reviewed.

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Tissue engineered cartilage, a promising strategy for articular cartilage repair.

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Nearly 20 engineered cartilage repair products in clinic based on clinical techniques.

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Combination product, the classification of tissue-engineered cartilage.

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Key regulatory compliance issues for combination products.

Osteochondral Allograft Transplant for Combined Medial and Lateral Patellar Cartilage Lesions: The Osteochondral Wide Lesion (OWL) Technique

Symptomatic articular cartilage injuries are often seen in young active patients and athletes. Magnetic resonance imaging screening examinations have frequently identified such lesions in athletic patients. Patellofemoral chondral defects were previously identified as the most common knee cartilage lesion in high-level athletes. Chondral defects measuring 2 cm² or greater and complex cartilage defects involving bone loss are ideally replaced with fresh osteochondral allograft. We describe a technique indicated for patients with symptomatic and recurrent anterior knee pain associated with osteochondral patellar defects including the lateral and medial patellar facets. Patients who have undergone previous interventions, including membrane techniques, microfracture, or autologous chondral transplantation, without clinical benefit are also eligible to undergo osteochondral allograft transplantation for combined medial and lateral patellar cartilage lesions, that is, the osteochondral wide lesion (OWL) technique.

A Comparative Study Using Fluorescent Confocal Microscopy and Flow Cytometry to Evaluate Chondrocyte Viability in Human Osteochondral Allografts

The preservation conditions of fresh osteochondral allografts for clinical applications are critical due their objective: to transplant mature hyaline cartilage containing viable chondrocytes, maintaining their metabolic activity and also preserving the structural and functional characteristics of the extracellular matrix. The aim of the present study was to compare fluorescence confocal microscopy and flow cytometry techniques to evaluate the viability of the chondrocytes present in the osteochondral tissue, in order to determine their effectiveness and thus ensure reproducibility and robustness of the analysis. To this end, osteochondral allografts from human cadaveric donors were preserved at 4 °C for 3 weeks in a preservation medium supplemented with antibiotic and antifungal agents. Cell viability of chondrocytes was determined by monitoring the cartilage for 3 weeks of preservation by confocal fluorescence microscopy and flow cytometry, obtaining cell viabilities of 83.7 ± 2.6% and 55.8 ± 7.8% for week three, respectively. The confocal fluorescence microscopy approach is more advantageous and accurate, as it correlates better with actual cell viability values for monitoring osteochondral graft preservation, detecting only the cells that died a natural death associated with the preservation method.

It's the Biology Orthopods! Heralding a Reconstructive Revolution Through Musculoskeletal Tissue Banks (MSTB) in India

BACKGROUND

A tissue bank is an establishment that aids in retrieval, processing, storage, and distribution  of human tissue for transplantation. For many years, such banks have been dispensing tissue to orthopaedic surgeons, performing reconstructive surgeries.

METHODOLOGY

The retrieval, preparation, and delivery of musculoskeletal tissue used for transplantation is an intricate process  involving varying practices among different musculoskeletal tissue banks.

RESULTS

Musculoskeletal allografts are used in various orthopaedic surgeries ranging from primary bone defects, trauma, and carcinoma to congenital disabilities. Every decade brings in paradigm shifts and new hope for treating challenging cases with the aid of newer devices and materials.

CONCLUSION

This review article outlines various technical, regulatory and quality enhancement steps involved in tissue banking. Also, it discusses the road ahead and the research avenues for developing novel allograft products with the synergy of tissue banks and clinicians.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s43465-022-00661-0.

Assessment of Outcomes After Multisurface Osteochondral Allograft Transplantations in the Knee

Background

Treatment of multisurface articular cartilage lesions of the knee is a challenging problem.

Hypothesis

Large multisurface cartilage defects in the knee can be successfully managed with transplantation of high chondrocyte viability osteochondral allografts (OCAs) to result in statistically significant improvements in patient-reported outcome measures of pain and function.

Study Design

Cohort study; Level of evidence, 3.

Methods

Patients were prospectively enrolled into a registry to follow outcomes after OCA transplantation. The study included patients who received OCA transplantation for multisurface unipolar defects in 1 knee and had minimum 2-year follow-up data, including patient-reported outcome measures, failures, reoperations, and complications. The OCA transplants had been stored using 2 methods: standard preservation (SP) or Missouri Osteochondral Preservation System (MOPS). Preoperative data were compared with outcomes at 1 year and final follow-up, and risk factors for revision surgery or failure (total knee arthroplasty) were analyzed.

Results

The sample included 25 patients with a mean age of 37.2 years (range, 13-51 years), body mass index of 27.7 (range, 18-38), and follow-up of 45.1 months (median, 49 months; range, 24-68 months). OCAs stored using SP were transplanted into 6 patients, and those stored using MOPS were transplanted into 19 patients. The initial success rate was significantly higher for MOPS OCAs (94.7%) than SP OCAs (33.3%). There were statistically significant improvements in all patient-reported outcomes at 1 year and final follow-up in the MOPS cohort (P < .0001 for all). Revision surgery/failure was significantly associated with patients who were nonadherent to the prescribed postoperative restrictions and rehabilitation protocols (P = .038; odds ratio = 13.5) and with OCAs that had a viable chondrocyte density <70% of the established reference range mean at transplantation (P = .0037; odds ratio = 76).

Conclusion

OCA transplantation for treatment of large multisurface cartilage defects in the knee resulted in a 94.7% initial success rate when grafts with high viable chondrocyte density (≥70%) were used and when patients strictly adhered to prescribed postoperative rehabilitation protocols. Successful outcomes were associated with statistically significant improvements in patient-reported outcome measures of pain and function.

Synoviocyte-Derived Extracellular Matrix and bFGF Speed Human Chondrocyte Proliferation While Maintaining Differentiation Potential

Improving the ability of human chondrocytes to proliferate, while maintaining their differentiation potential, has presented a great challenge in cartilage tissue engineering. In this study, human chondrocytes were cultured under four unique growth conditions at physiologic oxygen tension: tissue culture plastic (TCP) only, synoviocyte matrix (SCM)-coated flasks only, SCM-coated flasks with bFGF media supplement, and TCP with bFGF media supplement. The results indicated that, compared to standard TCP, all test conditions showed significantly increased cell expansion rates and an increase in both glycosaminoglycan (GAG) and collagen content during redifferentiation culture. Specifically, the combined SCM + bFGF growth condition showed an additive effect, with an increase of approximately 36% more cells per passage (5-7 days) when compared to the SCM alone. In conclusion, the results of this study demonstrate that bFGF and SCM can be used as supplements to enhance the growth of human chondrocytes both as individual enhancers and as a combined additive.

Fresh Osteochondral and Chondral Allograft Preservation and Storage Media: A Systematic Review of the Literature

BACKGROUND

Storage procedures and parameters have a significant influence on the health of fresh osteochondral allograft (OCA) cartilage. To date, there is a lack of agreement on the optimal storage conditions for OCAs.

PURPOSE

To systematically review the literature on (1) experimental designs and reporting of key variables of ex vivo (laboratory) studies, (2) the effects of various storage solutions and conditions on cartilage health ex vivo, and (3) in vivo animal studies and human clinical studies evaluating the effect of fresh OCA storage on osteochondral repair and outcomes.

STUDY DESIGN

Systematic review; Level of evidence, 5.

METHODS

A systematic review was performed using the PubMed, Embase, and Cochrane databases. The inclusion criteria were laboratory studies (ex vivo) reporting cartilage health outcomes after prolonged storage (>3 days) of fresh osteochondral or chondral tissue explants and animal studies (in vivo) reporting outcomes of fresh OCA. The inclusion criteria for clinical studies were studies (>5 patients) that analyzed the relationship of storage time or chondrocyte viability at time of implantation to patient outcomes. Frozen, cryopreserved, decellularized, synthetic, or tissue-engineered grafts were excluded.

RESULTS

A total of 55 peer-reviewed articles met the inclusion criteria. Ex vivo studies reported a spectrum of tissue sources and storage solutions and conditions, although the majority of studies lacked complete reporting of key variables, including storage solution formula and environmental conditions. The effect of various conditions (eg, temperature) and storage solutions on cartilage health were inconsistent. Although 60% of animal models suggest that storage time may influence outcomes and 80% indicate inferior outcomes with frozen OCA as compared with fresh OCA, 75% of clinical studies report no correlation between storage time and outcomes.

CONCLUSION

Given the variability in experimental designs and lack of reporting across studies, it is still not possible to determine optimal storage conditions, although animal studies suggest that storage time and chondrocyte viability influence osteochondral repair outcomes. A list of recommendations was developed to encourage reporting of key variables, such as media formulation, environmental factors, and methodologies used. High-quality clinical data are needed to investigate the effects of storage and graft health on outcomes.

Biologic Joint Restoration: A Translational Research Success Story

Treatment options that result in consistently successful outcomes for young and active patients with joint disorders are needed. This article summarizes two decades of rigorous research using a bedside-to-bench- to-bedside translational approach based on the One Health - One Medicine concept that culminated in successful clinical use of biologic joint restoration options for treatment of knee, hip, ankle, and shoulder problems in this growing patient population.

The immune microenvironment in cartilage injury and repair

The ability of articular cartilage to repair itself is limited because it lacks blood vessels, nerves, and lymph tissue. Once damaged, it can lead to joint swelling and pain, accelerating the progression of osteoarthritis. To date, complete regeneration of hyaline cartilage exhibiting mechanical properties remains an elusive goal, despite the many available technologies. The inflammatory milieu created by cartilage damage is critical for chondrocyte death and hypertrophy, extracellular matrix breakdown, ectopic bone formation, and progression of cartilage injury to osteoarthritis. In the inflammatory microenvironment, mesenchymal stem cells (MSCs) undergo aberrant differentiation, and chondrocytes begin to convert or dedifferentiate into cells with a fibroblast phenotype, thereby resulting in fibrocartilage with poor mechanical qualities. All these factors suggest that inflammatory problems may be a major stumbling block to cartilage repair. To produce a milieu conducive to cartilage repair, multi-dimensional management of the joint inflammatory microenvironment in place and time is required. Therefore, this calls for elucidation of the immune microenvironment of cartilage repair after injury. This review provides a brief overview of: (1) the pathogenesis of cartilage injury; (2) immune cells in cartilage injury and repair; (3) effects of inflammatory cytokines on cartilage repair; (4) clinical strategies for treating cartilage defects; and (5) strategies for targeted immunoregulation in cartilage repair. STATEMENT OF SIGNIFICANCE: Immune response is increasingly considered the key factor affecting cartilage repair. It has both negative and positive regulatory effects on the process of regeneration and repair. Proinflammatory factors are secreted in large numbers, and necrotic cartilage is removed. During the repair period, immune cells can secrete anti-inflammatory factors and chondrogenic cytokines, which can inhibit inflammation and promote cartilage repair. However, inflammatory factors persist, which accelerate the degradation of the cartilage matrix. Furthermore, in an inflammatory microenvironment, MSCs undergo abnormal differentiation, and chondrocytes begin to transform or dedifferentiate into fibroblast-like cells, forming fibrocartilage with poor mechanical properties. Consequently, cartilage regeneration requires multi-dimensional regulation of the joint inflammatory microenvironment in space and time to make it conducive to cartilage regeneration.

Outcomes Associated With Osteochondral Allograft Transplantation in Dogs

The purpose of this study was to retrospectively characterize outcomes and complications associated with osteochondral allograft transplantation for treating chondral and osteochondral lesions in a group of client-owned dogs with naturally-occurring disease. Records were reviewed for information on signalment, treated joint, underlying pathology (e.g., osteochondritis dissecans; OCD), and type, size, and number of grafts used. Complications were classified as “trivial” if no treatment was provided, “non-surgical” if non-surgical treatment were needed, “minor surgical” if a minor surgical procedure such as pin removal were needed but the graft survived and function was acceptable, or “major” if the graft failed and revision surgery were needed. Outcomes were classified as unacceptable, acceptable, or full function. Thirty-five joints in 33 dogs were treated including nine stifles with lateral femoral condyle (LFC) OCD and 10 stifles with medial femoral condyle (MFC) OCD treated with osteochondral cylinders or “plugs.” There were 16 “complex” procedures of the shoulder, elbow, hip, stifle, and tarsus using custom-cut grafts. In total there were eight trivial complications, one non-surgical complication, two minor surgical complications, and five major complications for a total of 16/35 cases with complications. Accordingly, there were five cases with unacceptable outcomes, all of whom had major complications while the other 30 cases had successful outcomes. Of the 30 cases with successful outcomes, 15 had full function and 15 had acceptable function. Based on these subjective outcome assessments, it appears osteochondral allograft transplantation is a viable treatment option in dogs with focal or complex cartilage defects. However, no conclusions can be made regarding the inferiority or superiority of allograft transplantation in comparison to other treatment options based upon these data.

Modernizing Storage Conditions for Fresh Osteochondral Allografts by Optimizing Viability at Physiologic Temperatures and Conditions

Objective. Osteochondral allograft (OCA) transplantation has demonstrated good long-term outcomes in treatment of cartilage defects. Viability, a key factor in clinical success, decreases with peri-implantation storage at 4°C during pathogen testing, matching logistics, and transportation. Modern, physiologic storage conditions may improve viability and enhance outcomes. Design. Osteochondral specimens from total knee arthroplasty patients (6 males, 5 females, age 56.4 ± 2.2 years) were stored in media and incubated at normoxia (21% O₂) at 22°C or 37°C, and hypoxia (2% O₂) at 37°C. Histology, live-dead staining, and quantitative polymerase chain reaction (qPCR) was performed 24 hours after harvest and following 7 days of incubation. Tissue architecture, cell viability, and gene expression were analyzed. Results. No significant viability or gene expression deterioration of cartilage was observed 1-week postincubation at 37°C, with or without hypoxia. Baseline viable cell density (VCD) was 94.0% ± 2.7% at day 1. At day 7, VCD was 95.1% (37°C) with normoxic storage and 92.2% (37°C) with hypoxic storage (P ≥ 0.27). Day 7 VCD (22°C) incubation was significantly lower than both the baseline and 37°C storage values (65.6%; P < 0.01). COL1A1, COL1A2, and ACAN qPCR expression was unchanged from baseline (P < 0.05) for all storage conditions at day 7, while CD163 expression, indicative of inflammatory macrophages and monocytes, was significantly lower in the 37°C groups (P < 0.01). Conclusion. Physiologic storage at 37°C demonstrates improved chondrocyte viability and metabolism, and maintained collagen expression compared with storage at 22°C. These novel findings guide development of a method to optimize short-term fresh OCA storage, which may lead to improved clinical results.

Articular cartilage repair & joint preservation: A review of the current status of biological approach

The articular cartilage of the joint is the thin viscoelastic layer of the connective tissue. It has a unique anatomy and physiology, which makes the repair of the articular cartilage damage more difficult and challenging due to its limited healing capacity. Increasing knowledge regarding the importance of articular cartilage for joint preservation has led to increased attention on early identification of cartilage damage as well as degeneration in order to delay osteoarthritis. There are various treatment modalities ranging from preventive management, physical therapy, pharmacological, non-pharmacological and surgical treatments exist in current literature. However most of the studies have limited long term follow up and mainly consists of small case series and case reports. This is an up to date concise review discussing the available management options for articular cartilage damage starting to lifestyle modification to pharmacotherapy, physiotherapy, and osteobiologics till various joint preservation techniques that have been in use currently.

Doxycycline preserves chondrocyte viability and function in human and calf articular cartilage ex vivo

Prolonging chondrocyte survival is essential to ensure fresh osteochondral (OC) grafts for treatment of articular cartilage lesions. Doxycycline has been shown to enhance cartilage growth, disrupt terminal differentiation of chondrocytes, and inhibit cartilage matrix degradation. It is unknown whether doxycycline prolongs chondrocyte survival in OC grafts. We hypothesized that doxycycline protects against chondrocyte death and maintains function of articular cartilage. To test this hypothesis, we employed human and calf articular cartilages, and incubated chondrocytes isolated from cartilage or cartilage plugs with doxycycline (0, 1 or 10 μg/ml) at either 37°C or 4°C. Chondrocyte viability, apoptosis, glycosaminoglycan (GAG), collagen, and mechanical test in cartilage plugs were measured. We found that reduced chondrocyte viability, increased chondrocyte apoptosis, reduced GAG contents, and impaired equilibrium modulus in cartilage plugs were observed in a time-dependent manner at both 37°C and 4°C. Chondrocyte viability was further reduced when the plugs were cultured at 4°C as compared to 37°C. Doxycycline prolonged viability and reduced apoptosis of chondrocytes during culture of cartilage plugs. Functionally, doxycycline protected against reduced production of GAG and collagen II as well as impaired mechanical properties in cartilage plugs during culture. Mechanistically, doxycycline increased mitochondrial respiration in cultured chondrocytes. In conclusion, preservation at 37°C is beneficial for maintaining chondrocyte viability in cartilage plugs compared to 4°C. Incubation of doxycycline protects against chondrocyte apoptosis, reduced extracellular matrix, and impaired mechanical properties in cartilage plugs. The findings provide a potential approach using doxycycline at 37°C to preserve chondrocyte viability in fresh OC grafts for treatment of articular cartilage lesions.

Unicompartmental bipolar osteochondral and meniscal allograft transplantation is effective for treatment of medial compartment gonarthrosis in a canine model

Osteochondral allograft (OCA) transplantation can restore large articular defects in the knee. Bipolar OCA transplantations for partial and whole joint resurfacing often have less favorable results than single-surface transplants. This study was designed to use a large animal model to test the hypothesis that unicompartmental bipolar osteochondral and meniscal allograft transplantation (BioJoint) would be as or more effective for treatment of medial compartment osteoarthritis (OA) compared to standard-of-care nonoperative treatment. OA was induced in one knee of each research hound (n = 8) using a meniscal release model and pretreatment assessments were performed. After 3 months, dogs were randomly assigned to either the control group (n = 4, no surgical intervention, daily nonsteroidal antiinflammatory drugs [NSAIDs]) or the BioJoint group (n = 4). Clinical, radiographic, and arthroscopic assessments were performed longitudinally and histopathology was evaluated at the 6-month endpoint. At study endpoint, functional, pain, and total pressure index measures, as well as radiographic and arthroscopic grading of graft appearance and joint health, demonstrated superior outcomes for BioJoints compared to NSAID controls. Furthermore, histologic assessments showed that osteochondral and meniscal transplants maintain integrity and integrated into host tissues. Clinical significance: The results support the safety and efficacy of unicompartmental bipolar osteochondral and meniscal allograft transplantation in a preclinical model with highly functional outcomes without early OA progression.

Three-dimensional-printed custom guides for bipolar coxofemoral osteochondral allograft in dogs

The objective of this experimental study was to develop and evaluate a three-dimensionally printed custom surgical guide system for performing bipolar coxofemoral osteochondral allograft transplantation in dogs. Five cadaver dogs, weighing 20–38 kg were used in the study. Custom surgical guides were designed and three-dimensionally printed to facilitate accurate execution of a surgical plan for bipolar coxofemoral osteochondral allograft transplantation. Guide-assisted technique was compared to freehand technique in each cadaver. Surgical time was recorded and postoperative computed tomography and three-dimensional segmentation was performed. Femoral version and inclination angles, femoral neck length, and gap present at the femoral and acetabular donor-recipient interface was compared between the virtual surgical plan and postoperative outcome for both techniques. One-tailed paired t-test (P < .05) was used for statistical analysis. When compared to free-hand preparation, mean donor femoral preparation time was 10 minutes longer and mean recipient preparation time was 2 minutes longer when using guides (p = 0.011 and p = 0.001, respectively). No difference in acetabular preparation time was noted between groups. Gap volume at the acetabular and femoral donor-recipient interface was not different between groups. Mean difference between the planned and postoperative version angle was 6.2° lower for the guide group when compared to the freehand group (p = 0.025). Mean femoral neck length was 2 mm closer to the plan when using guides than when performing surgery freehand (p = 0.037). Accuracy for femoral angle of inclination was not different between groups. Custom surgical guides warrants consideration in developing bipolar coxofemoral osteochondral allograft transplantation as an alternative surgical technique for managing hip disorders in dogs.

Comparison of meniscal allograft transplantation techniques using a preclinical canine model

Meniscal allograft transplantation (MAT) can be a safe, effective treatment for meniscal deficiency resulting in knee dysfunction, leading to osteoarthritis (OA) without proper treatment with 5-year functional success rates (75%-90%). While different grafts and techniques have generally proven safe and effective, complications include shrinkage, extrusion, progression of joint pathology, and failure. The objective of this study was to assess the functional outcomes after MAT using three different clinically-relevant methods in a preclinical canine model. The study was designed to test the hypothesis that fresh meniscal-osteochondral allograft transplantation would be associated with significantly better function and joint health compared with fresh-viable or fresh-frozen meniscus-only allograft transplantations. Three months after meniscal release to induce meniscus-deficient medial compartment disease, research hounds (n = 12) underwent MAT using meniscus allografts harvested from matched dogs. Three MAT conditions (n = 4 each) were compared: frozen meniscus-fresh-frozen meniscal allograft with menisco-capsular suture repair; fresh meniscus-fresh viable meniscal allograft (Missouri Osteochondral Preservation System (MOPS)-preservation for 30 days) with menisco-tibial ligament repair; fresh menisco-tibial-fresh, viable meniscal-tibial-osteochondral allografts (MOPS-preservation for 30 days) with menisco-tibial ligament preservation and autogenous bone marrow aspirate concentrate on OCA bone. Assessment was performed up to 6 months after MAT. Pain, comfortable range of motion, imaging, and arthroscopic scores as well histological and cell viability findings were superior (P < .05) for the fresh menisco-tibial group compared with the two other groups. Novel meniscal preservation and implantation techniques with fresh, MOPS-preserved, viable meniscal-osteochondral allografts with menisco-tibial ligament preservation appears to be safe and effective for restoring knee function and joint health in this preclinical model. This has the potential to significantly improve outcomes after MAT.

Systematic Review of Osteochondral Allograft Transplant Immunology: How We Can Further Optimize Outcomes

Despite the growing success for osteochondral allograft (OCA) transplantation in treating large articular cartilage lesions in multiple joints, associated revision and failure rates are still higher than desired. While immunorejection responses have not been documented, the effects of the host's immune responses on OCA transplantation failures have not been thoroughly characterized. The objective of this study was to systematically review clinically relevant peer-reviewed evidence pertaining to the immunology of OCAs to elucidate theragnostic strategies for improving functional graft survival and outcomes for patients undergoing OCA transplantation. This systematic review of Cochrane Central Register of Controlled Trials, the Cochrane Database of Systematic Reviews, MEDLINE, PubMed, and EMBASE suggests that host immune responses play key roles in incorporation and functional survival of OCA transplants. OCA rejection has not been reported; however, graft integration through creeping substitution is reliant on host immune responses. Prolonged inflammation, diminished osteogenic potential for healing and incorporation, and relative bioburden are mechanisms that may be influenced by the immune system and contribute to undesirable outcomes after OCA transplantation. Based on the safety and efficacy of OCA transplantation and its associated benefits to a large and growing patient population, basic, preclinical, and clinical osteoimmunological studies on OCA transplantation that comprehensively assess and correlate cellular, molecular, histologic, biomechanical, biomarkers, diagnostic imaging, arthroscopic, functional, and patient-reported outcome measures are of high interest and importance.

Initial clinical outcomes comparing frozen versus fresh meniscus allograft transplants

BACKGROUND

To evaluate initial clinical outcomes using fresh meniscal allografts with high cell viability at transplantation time and meniscotibial ligament (MTL) reconstruction (Fresh) in comparison to standard fresh-frozen (Frozen) meniscus allograft transplantation (MAT).

METHODS

Patients treated for medial and/or lateral meniscal deficiency using either Fresh or Frozen MAT with minimum of 1-year follow-up were identified from a prospective registry. Patient demographics, prior surgeries, MAT surgery data, complications, revisions, and failures were documented. Functional outcome scores were collected preoperatively, and 6 months and yearly after surgery and radiographic joint space measurements were performed. Treatment cohorts were compared for statistically significant (P < 0.005) differences using t-Tests and Fisher's exact tests.

RESULTS

Twenty-seven patients (14 Fresh, 13 Frozen) met inclusion criteria and showed comparable characteristics. For Fresh MAT + MTL, 10 medial, two lateral, and two medial + lateral MAT were performed. For Frozen MAT, nine medial, and four lateral MAT were performed. There was significantly more improvement in the Fresh cohort compared to the Frozen cohort for VAS pain (P = 0.014), PROMIS Physical Function (P = 0.036) and Single Assessment Numeric Evaluation (P = 0.033) from preoperatively to 2 years postoperatively. Tegner Activity Scale and PROMIS Mobility score showed no significant differences. The International Knee Documentation Committee score revealed a clinically meaningful change for the Fresh group. Radiographic measurements showed no significant differences between groups. There were two Fresh MAT + MTL revisions and one conversion to TKA in each cohort.

CONCLUSIONS

Fresh MAT + MTL is safe and associated with potential advantages with respect to initial pain relief and function compared to standard frozen MAT.

Fresh Osteochondral Allograft Transplants in the Knee: Bipolar and Beyond

Knee patients who have sustained chondral and osteochondral lesions suffer from debilitating pain, which can ultimately lead to posttraumatic osteoarthritis and whole-joint disease. Older, nonactive patients are traditionally steered toward total knee arthroplasty (TKA), but younger, active patients are not good candidates for TKA based on implant longevity, complications, morbidity, and risk for revision, such that treatment strategies at restoring missing hyaline cartilage and bone are highly desired for this patient population. Over the past four decades, fresh osteochondral allograft (OCA) transplantation has been developed as a treatment method for large (> 2.5 cm²) focal full-thickness articular cartilage lesions. This article documents our own institutional OCA journey since 2016 through enhanced graft preservation techniques (the Missouri Osteochondral Preservation System, or MOPS), technical improvements in surgical techniques, use of bone marrow aspirate concentrate, bioabsorbable pins and nails, and prescribed and monitored patient-specific rehabilitation protocols. Further follow-up with documentation of long-term outcomes will provide insight for continued optimization for future applications for OCA transplantation, potentially including a broader spectrum of patients appropriate for this treatment. Ongoing translational research is necessary to blaze the trail in further optimizing this treatment option for patients.

Clinical Application of the Basic Science of Articular Cartilage Pathology and Treatment

The joint is an organ with each tissue playing critical roles in health and disease. Intact articular cartilage is an exquisite tissue that withstands incredible biologic and biomechanical demands in allowing movement and function, which is why hyaline cartilage must be maintained within a very narrow range of biochemical composition and morphologic architecture to meet demands while maintaining health and integrity. Unfortunately, insult, injury, and/or aging can initiate a cascade of events that result in erosion, degradation, and loss of articular cartilage such that joint pain and dysfunction ensue. Importantly, articular cartilage pathology affects the health of the entire joint and therefore should not be considered or addressed in isolation. Treating articular cartilage lesions is challenging because left alone, the tissue is incapable of regeneration or highly functional and durable repair. Nonoperative treatments can alleviate symptoms associated with cartilage pathology but are not curative or lasting. Current surgical treatments range from stimulation of intrinsic repair to whole-surface and whole-joint restoration. Unfortunately, there is a relative paucity of prospective, randomized controlled, or well-designed cohort-based clinical trials with respect to cartilage repair and restoration surgeries, such that there is a gap in knowledge that must be addressed to determine optimal treatment strategies for this ubiquitous problem in orthopedic health care. This review article discusses the basic science rationale and principles that influence pathology, symptoms, treatment algorithms, and outcomes associated with articular cartilage defects in the knee.

Clinical Application Status of Articular Cartilage Regeneration Techniques: Tissue-Engineered Cartilage Brings New Hope

Hyaline articular cartilage lacks blood vessels, lymphatics, and nerves and is characterised by limited self-repair ability following injury. Traditional techniques of articular cartilage repair and regeneration all have certain limitations. The development of tissue engineering technology has brought hope to the regeneration of articular cartilage. The strategies of tissue-engineered articular cartilage can be divided into three types: “cell-scaffold construct,” cell-free, and scaffold-free. In “cell-scaffold construct” strategies, seed cells can be autologous chondrocytes or stem. Among them, some commercial products with autologous chondrocytes as seed cells, such as BioSeed®-C and CaReS®, have been put on the market and some products are undergoing clinical trials, such as NOVOCART® 3D. The stem cells are mainly pluripotent stem cells and mesenchymal stem cells from different sources. Cell-free strategies that indirectly utilize the repair and regeneration potential of stem cells have also been used in clinical settings, such as TruFit and MaioRegen. Finally, the scaffold-free strategy is also a new development direction, and the short-term repair results of related products, such as NOVOCART® 3D, are encouraging. In this paper, the commonly used techniques of articular cartilage regeneration in surgery are reviewed. By studying different strategies and different seed cells, the clinical application status of tissue-engineered articular cartilage is described in detail.

Prospective Assessment of Outcomes After Primary Unipolar, Multisurface, and Bipolar Osteochondral Allograft Transplantations in the Knee: A Comparison of 2 Preservation Methods

BACKGROUND

Articular cartilage lesions in the knee remain a challenging clinical problem.

HYPOTHESIS

A novel graft preservation method combined with surgical technique and patient management improvements would lead to consistently successful outcomes after osteochondral allograft (OCA) transplantation.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

With institutional review board approval and informed consent, patients were prospectively enrolled into a registry to follow outcomes after OCA transplantation. Patients were included when ≥1-year follow-up data were available, including complications and reoperations, patient-reported outcome measures (PROMs), compliance with rehabilitation, revisions, and failures.

RESULTS

For patients meeting inclusion criteria (N = 194), mean ± SD age was 37.9 ± 12.2 years and mean BMI was 28.9 ± 5; 38% received unipolar transplants (44% multisurface) and 62% received bipolar transplants. OCAs were preserved by standard tissue bank methods (standard preservation [SP]; 29%) or the novel method (Missouri Osteochondral Preservation System [MOPS]; 71%). Initial success rates were 79% for all cases combined, 60% for SP, and 84% for MOPS. MOPS cases were significantly (P = .028) more likely to be associated with successful outcomes when compared with SP cases. PROMs improved significantly (P < .05) for all cohorts through 3 to 4 years of follow-up. Revisions were performed in 19 cases (10%). MOPS grafts were associated with a significantly (P = .0014) lower revision rate (5%) than SP grafts (21%). Failures occurred in 26 patients (13%), with all undergoing total knee arthroplasty. Bipolar cases were significantly (P = .008) more likely to be associated with failure. MOPS grafts were associated with a significantly (P = .048) lower failure rate (11%) than were SP grafts (19%). Noncompliance with the prescribed rehabilitation protocol was significantly (P = .00008) more likely to be associated with failure.

CONCLUSION

Prospective data for 194 cases revealed that OCA transplantation for unipolar, multisurface, and bipolar cartilage restoration can be associated with consistently successful outcomes. The 5% revision rate, 11% failure rate, 82%-94% survival probability estimates, and continually improving PROMs through postoperative 3 to 4 years underscore major advances in outcomes as compared with previous reports. These encouraging results were realized with the use of a novel graft preservation method; autogenous bone marrow concentrate pretreatment of donor bone; advancements in graft cutting, implantation, and stabilization techniques; and procedure-specific rehabilitation protocols.

Protocol for Harvest, Transport and Storage of Human Osteochondral Tissue

Objective  To elaborate a protocol for the harvest, transport, and preservation of human osteochondral tissue for use in tissue banks (TBs).

Methods  Osteochondral fragments measuring 2 cm ³ of 5 corpse donors aged between 15 and 45 years old were analyzed. The samples were stored in cell preservation medium containing: human albumin, Iscove's and vancomycin preserved at 4°C. The concentration of proteoglycans in the extracellular medium was quantified by the use of Safranin-O, while tissue structural analysis was assessed by histological study with hematoxylin-eosin stained slides. The images obtained were analyzed according to the histological scores of Mankin and the score proposed by the OsteoArthritis Research Society International. The samples were analyzed with 0, 15, 30 and 45 days of preservation.

Results  The osteochondral fragments studied showed a progressive decrease in proteoglycan concentration with increased preservation time. After 30 days of preservation, structural changes were identified with discontinuity of the cartilage surface layer. According to the results obtained by the Mankin score, there was a statistically significant difference between 15 and 30 days of tissue preservation.

Conclusion  The protocol described defined knee transport immersed in Lactated Ringer at a controlled temperature of 10° C until its arrival at the TB. After processing, the preservation solution was composed of Iscove's serum-free cell culture medium supplemented with 10% human albumin and 100 μg/ml vancomycin. The tissue was preserved at a temperature of 4°C until the moment of transplantation characterizing the fresh preservation.

Current solutions for the treatment of chronic articular cartilage defects in the knee

Chondral and osteochondral defects in the knee are common and may lead to degenerative joint disease if treated inappropriately.

Conventional treatments such as microfracture often result in fibrocartilage formation and are associated with inferior results. Additionally, microfracture is generally unsuitable for the treatment of defects larger than 2–4 cm².

The osteochondral autograft transfer system (OATS) has been shown to produce superior clinical outcomes to microfracture but is technically difficult and may be associated with donor-site morbidity. Osteochondral allograft use is limited by graft availability and failure of cartilage incorporation is an issue.

Autologous chondrocyte implantation (ACI) has been shown to result in repair with hyaline-like cartilage but involves a two-stage procedure and is relatively expensive.

Rehabilitation after ACI takes 12 months, which is inconvenient and not feasible for athletic patients.

Newer methods to regenerate cartilage include autologous stem cell transplantation, which may be performed as a single-stage procedure, can have a shorter rehabilitation period and is less expensive than ACI. Longer-term studies of these methods are needed.

Cite this article: EFORT Open Rev 2020;5:156-163. DOI: 10.1302/2058-5241.5.190031

Effects of Compliance With Procedure-Specific Postoperative Rehabilitation Protocols on Initial Outcomes After Osteochondral and Meniscal Allograft Transplantation in the Knee

Background:

Osteochondral and meniscal allograft transplantation have been performed in the knee for more than 40 years, with the number of patients treated each year growing as allograft quantity and quality increase. To date, the effects of postoperative management on outcomes after these procedures have received relatively little focus in the peer-reviewed literature.

Hypothesis:

Compliance with the recommended postoperative management protocol will be associated with significantly higher initial success and significantly lower revision and failure rates for patients undergoing osteochondral and/or meniscal allograft transplantation in the knee.

Study Design:

Cohort study; Level of evidence, 3.

Methods:

Patients were prospectively enrolled into a dedicated registry designed to follow outcomes after osteochondral and/or meniscal allograft transplantation. Patients were included when at least 1 year of follow-up data were available, including data on complications and reoperations, patient-reported outcome measures, compliance with rehabilitation, revisions, or failures, based on the electronic medical record and communication logs with patients’ outpatient physical therapists.

Results:

For patients meeting the inclusion criteria (N = 162), compliance with the prescribed procedure-specific postoperative management protocol was associated with significantly higher 1- to 3-year success and significantly lower revision and failure rates. Specifically, patients who were compliant were 6.3 times less likely to need allograft revision or total knee arthroplasty and 7.5 times more likely to have a successful outcome at 1 to 3 years after osteochondral and/or meniscal allograft transplantation. In addition to noncompliance, older patient age and higher body mass index were associated with inferior short-term outcomes in this cohort.

Conclusion:

These data suggest that compliance with procedure-specific postoperative rehabilitation protocols is associated with higher success, lower revision, and lower failure rates for patients undergoing osteochondral and meniscal allograft transplantation. Given these results showing the importance of these modifiable risk factors, our center has devoted resources to preoperative patient assessment and communication to provide education, set appropriate expectations, identify and address modifiable risk factors, impediments, and noncompliance, and monitor and adjust postoperative care as indicated.

Current Trends in the Evaluation of Osteochondral Lesion Treatments: Histology, Histomorphometry, and Biomechanics in Preclinical Models

Osteochondral lesions (OCs) are typically of traumatic origins but are also caused by degenerative conditions, in primis osteoarthritis (OA). On the other side, OC lesions themselves, getting worse over time, can lead to OA, indicating that chondral and OC defects represent a risk factor for the onset of the pathology. Many animal models have been set up for years for the study of OC regeneration, being successfully employed to test different treatment strategies, from biomaterials and cells to physical and biological adjuvant therapies. These studies rely on a plethora of post-explant investigations ranging from histological and histomorphometric analyses to biomechanical ones. The present review aims to analyze the methods employed for the evaluation of OC treatments in each animal model by screening literature data within the last 10 years. According to the selected research criteria performed in two databases, 60 works were included. Data revealed that lapine (50% of studies) and ovine (23% of studies) models are predominant, and knee joints are the most used anatomical locations for creating OC defects. Analyses are mostly conducted on paraffin-embedded samples in order to perform histological/histomorphometric analyses by applying semiquantitative scoring systems and on fresh samples in order to perform biomechanical investigations by indentation tests on articular cartilage. Instead, a great heterogeneity is pointed out in terms of OC defect dimensions and animal's age. The choice of experimental times is generally adequate for the animal models adopted, although few studies adopt very long experimental times. Improvements in data reporting and in standardization of protocols would be desirable for a better comparison of results and for ethical reasons related to appropriate and successful animal experimentation.

Clinical Outcomes of Revision Osteochondral Allograft Transplantation

PURPOSE

To assess the survivorship, clinical outcomes, and radiographic outcomes of patients who have undergone revision osteochondral allograft (OCA) to the knee in a retrospective case series.

METHODS

Nine patients who underwent revision OCA by the senior author between January 2003 and December 2015 with a minimum follow up of 2 years were reviewed retrospectively. Patients completed patient-reported outcome surveys containing the visual analog scale, the International Knee Documentation Committee, the Knee injury and Osteoarthritis Outcome Score, Lysholm score, and the Short-Form 12. Radiographic analysis included anteroposterior view graded via the Kellgren and Lawrence scale. Complications and reoperations were analyzed, with failure defined as conversion to arthroplasty. (Institutional review board 15050301.) RESULTS: One of 10 consecutive patients was lost to follow up, for an overall follow-up rate of 90% (5 males, 4 females); mean follow up, 4.53 ± 3.17 years. The median patient age at the time of revision OCA was 33 years (interquartile range [IQR], 8.6), the median defect size was 4.0 cm² (IQR, 0), and the median time from index OCA to revision OCA was 2.9 years (IQR, 1.9). Five patients (50%) underwent subsequent surgery at a median of 1.92 years (IQR, 7.25), with 1 progressing to arthroplasty at 23 months after revision OCA, for an overall failure rate of 11%. There were no significant differences in any of the patient-reported outcome assessments compared with prerevision OCA (postindex OCA) values at final follow up (P > .05 for all). Similarly, there were no significant differences in Kellgren and Lawrence score before and after surgery (P = .1).

CONCLUSIONS

At a mean 4.5 years following revision OCA, there was an 89% graft survivorship rate in a series of 9 patients, with no statistical changes in the radiographic progression of arthritis.

LEVEL OF EVIDENCE

Level IV, case series.

Effects of Rolling-Sliding Mechanical Stimulation on Cartilage Preserved In Vitro

Introduction

Mechanical stimulation is important for maintaining cartilage function. We used a loading device to exert rolling-sliding mechanical stimulation on cartilage preserved in vitro to investigate cartilage viability and the involved mechanisms.

Methods

Osteochondral grafts from pig knees were randomly classified into loading and control groups. The loading group cartilage was subjected to cycles of mechanical stimulation with specified frequency/time/pressure combinations every 3 days; Then the DMEM was refreshed, and the cartilage was preserved in vitro. The control group cartilage was preserved in DMEM throughout the process and was changed every 3 days. On days 14 and 28, the chondrocyte survival rate, histology, and Young's modulus of the cartilage were measured. Western blots were performed after 2 h of loading to evaluate the protein expression.

Results

The loading group showed a significantly higher chondrocyte survival rate, proteoglycan and type II collagen content, and Young's modulus than did the control group on day 14, but no statistically significant differences were found on day 28. After two hours of the loading, the phosphorylation levels of MEK and ERK1/2 increased, and the expression of caspase-3, cleaved caspase-3 and bax decreased.

Conclusion

These results suggest that periodic rolling-sliding mechanical stimulation can increase cartilage vitality in 2 weeks; a possible mechanism is that mechanical stimulation activates the MEK/ERK signalling pathway, thus inhibiting apoptotic protein expression. This loading preservation scheme could be used by cartilage tissue banks to improve cartilage preservation in vitro and enhance the quality of cartilage repair.

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.

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.

Outcomes After Fresh Osteochondral Allograft Transplantation for Medium to Large Chondral Defects of the Knee

Background:

Articular cartilage defects of the knee can significantly impair function among young, high-demand patients. There are several techniques for chondral restoration, including osteochondral allograft transplantation (OCA), that may alleviate pain and re-create the native anatomy. However, clinical outcomes among athletic cohorts are limited.

Purpose:

To evaluate the efficacy and functional outcomes of OCA for medium to large osteochondral defects of the knee in physically active United States military servicemembers.

Study Design:

Case series; Level of evidence, 4.

Methods:

A military health care database was queried to identify all OCA procedures performed between January 2009 and March 2013. Inclusion criteria were army personnel with a minimum of 2 years’ follow-up. Exclusion criteria included incomplete follow-up, inaccurate coding, and nonmilitary status. Variables of interest included sex, age, lesion location, grade and size of the lesion, body mass index, tobacco use, preoperative and postoperative visual analog scale (VAS) scores for pain, and presence of perioperative complications. Overall failure was defined as the inability to return to preoperative functional activities because of persistent knee complaints (clinical failure) or a revision cartilage procedure or arthroplasty (surgical failure).

Results:

A total of 61 patients (52 male; mean age, 31.7 years) were identified, with a mean 46.2-month follow-up. The mean VAS pain score improved from 4.10 ± 2.17 preoperatively to 2.68 ± 2.73 postoperatively (P < .0009), and only 6 (9.8%) required a subsequent revision chondral procedure. Overall, 39 patients (63.9%) were able to return to a level of activity that allowed for the completion of military duties. Risk factors for clinical failure were preoperative body mass index, preoperative pain as measured on the VAS, and moderate to severe postoperative pain on the VAS. The risk factor for surgical failure was the presence of a complication. Risk factors for overall failure were the presence of a complication and moderate to severe postoperative pain on the VAS.

Conclusion:

OCA provided moderate success in retaining active-duty army servicemembers. Approximately two-thirds of patients undergoing OCA were able to return to their preinjury occupational activity, while approximately 57% of patients returned to prior levels without a subsequent revision chondral procedure or arthroplasty.

Allograft Tissue Safety and Technology

Allograft tissues are commonly used by orthopedic surgeons and are processed using a variety of technologies to increase safety and clinical use. For safety, although disease transmission is a tangible risk, this possibility has been dramatically minimized through modern tissue-processing methods. These include steps to prevent processing tissues with unacceptable bioburden through rigorous screening using donor medical and social histories along with microbial testing of recovered tissue and viral testing of donor serum. Potential bioburden is also controlled through aseptic recovery and processing methods and then reduced through disinfection steps that can include antibiotics, detergents, mechanical process, chemical solutions, and terminal sterilization. Processing steps may also include decellularization methods to lower immunogenic potential of some tissues. To enhance fusion potential of bone void fillers, demineralization steps may be used, and the resultant demineralized bone matrices may be combined with a carrier to improve handling. Bone void fillers and osteochondral allografts may also be specially processed to retain a living cellular component. To preserve relevant biological, biochemical, and physical properties of allografts for clinical use and ease of handling, a number of methods may be used which include: (1) refrigeration in media, (2) freeze-drying, (3) cryopreservation, (4) freezing, and (5) media storage at room temperature. As academic and industry research continue to drive advances, the future direction of allograft tissue likely includes injectables, coatings, cellular therapies, and combinations with other materials. The technology approaches outlined here will be further described along with future directions.

Physiologic Medium Maintains the Homeostasis of Immature Bovine Articular Cartilage Explants in Long-Term Culture

The ability to maintain living articular cartilage tissue in long-term culture can serve as a valuable analytical research tool, allowing for direct examination of mechanical or chemical perturbations on tissue behavior. A fundamental challenge for this technique is the recreation of the salient environmental conditions of the synovial joint in culture that are required to maintain native cartilage homeostasis. Interestingly, conventional media formulations used in explanted cartilage tissue culture investigations often consist of levels of metabolic mediators that deviate greatly from their concentrations in synovial fluid. Here, we hypothesize that the utilization of a culture medium consisting of near-physiologic levels of several highly influential metabolic mediators (glucose, amino acids, cortisol, insulin, and ascorbic acid) will maintain the homeostasis of cartilage explants as assessed by their mechanical properties and extracellular matrix contents. Results demonstrate that the aforementioned mediators have a strong effect on the mechanical and biochemical stability of skeletally immature bovine cartilage explants. Most notably, 1) in the absence of cortisol, explants exhibit extensive swelling and tissue softening and 2) in the presence of supraphysiologic levels of anabolic mediators (glucose, amino acids, insulin), explants exhibit increased matrix accumulation and tissue stiffening. In contrast, the administration of physiologic levels of these mediators (as present in native synovial fluid) greatly improves the stability of live cartilage explants over one month of culture. These results may have broad applicability for articular cartilage and other musculoskeletal tissue research, setting the foundation for important culture formulations required for examinations into tissue behavior.

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.

Priming and cryopreservation of microencapsulated marrow stromal cells as a strategy for intervertebral disc regeneration

A challenge in using stromal cells for intervertebral disc (IVD) regeneration is their limited differentiation capacity in vivo without exogenous growth factor (GF) supplementation. Priming of stromal cells prior to transplantation may offer a feasible strategy to overcome this limitation. Furthermore, the ability to cryopreserve cells could help alleviate logistical issues associated with storage and transport. With these critical translational challenges in mind, we aimed to develop a strategy involving priming and subsequent cryopreservation of microencapsulated bone marrow stromal cells (BMSCs). In phase one, we utilised the electrohydrodynamic atomisation process to fabricate BMSC-encapsulated microcapsules that were primed with TGF-β3 for 14 d after which they were cultured for a further 21 d under basal or GF supplemented media conditions. Results showed that priming induced differentiation of BMSC microcapsules such that they synthesised significant amounts of sGAG (61.9 ± 2.0 μg and 55.3 ± 6.1 μg for low and high cell densities) and collagen (24.4 ± 1.9 μg and 55.3 ± 4.6 μg for low and high cell densities) in continued culture without GF supplementation compared to Unprimed microcapsules. Phase two of this work assessed the extracellular matrix forming capacity of Primed BMSC microcapsules over 21 d after cryopreservation. Notably, primed and cryopreserved BMSCs successfully retained the ability to synthesise both sGAG (24.8 ± 2.7 μg and 75.1 ± 11.6 μg for low and high cell densities) and collagen (26.4 ± 7.8 μg and 93.1 ± 10.2 μg for low and high cell densities) post-cryopreservation. These findings demonstrate the significant potential of priming and cryopreservation approaches for IVD repair and could possibly open new horizons for pre-designed, 'off-the-shelf' injectable therapeutics.