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

Fresh Versus Frozen Meniscal Allograft Transplant: Revisit or Redundant? A Systematic Review

BACKGROUND

Fresh-frozen allografts are the current standard in meniscal allograft transplant (MAT) surgery, due to their availability, ease of preservation, and affordability. However, fresh-frozen grafts are associated with several clinical challenges such as graft shrinkage and extrusion, among many others.

PURPOSE

To present the current knowledge on the use of fresh meniscal allografts, presenting whether benefits associated with fresh grafts provide sufficient evidence to support their use in clinical practice.

STUDY DESIGN

Systematic review; Level of evidence, 5.

METHODS

A comprehensive search was conducted with keywords listed below. After an initial screening on title and abstract, full-text articles were assessed with the inclusion criteria.

RESULTS

A total of 78 studies matched the inclusion criteria. Literature and preclinical studies indicated that fresh meniscal allografts are beneficial for maintaining mechanical properties, graft ultrastructure, and matrix metabolism due to the presence of viable cells. Therefore, fresh allografts may address common complications associated with fresh-frozen MAT. To overcome challenges associated with both fresh-frozen and fresh allografts, a group has studied treating fresh-frozen allografts with a cell-based injection therapy.

CONCLUSION

Fresh meniscal allografts pose several challenges including limited availability, demanding preservation procedures, and high costs. Although the role of viable cells within meniscal allografts remains controversial, these cells may be vital for maintaining tissue properties.

Elevated Lipid Metabolites in Stored Clinical OCA Media Correlate With Chondrocyte Death

BACKGROUND

A major limitation of osteochondral allografts (OCA) is the deterioration of cartilage health associated with cell death during prolonged storage. However, little is known about the mechanisms that contribute to chondrocyte death during storage.

PURPOSE/HYPOTHESIS

This study aimed to determine whether bioactive lipid metabolites accumulate in the storage media of OCA and whether they are associated with a loss of chondrocyte viability during prolonged storage. It was hypothesized that free fatty acids (FFAs) would accumulate over time in the storage media of OCA and adversely affect cartilage health during storage.

STUDY DESIGN

Controlled laboratory study.

METHODS

A group of 21 (n = 6-8 OCA/treatment group) fresh human hemicondylar OCA tissues and media were analyzed after 7, 28, and 68 days of prolonged cold (4°C) storage. Targeted mass spectrometry analysis was used to quantify bioactive FFAs, as well as primary (lipid hydroperoxide [ROOH]) and secondary (malondialdehyde) lipid oxidation products. Chondrocyte viability was measured using a fluorescence-based live/dead assay and confocal microscopy.

RESULTS

The concentration of all targeted fatty acid metabolites in storage media was significantly increased with increased cold storage time (P < .05). ROOH was significantly higher on day 28 of cold storage. No difference in secondary ROOH products in storage media was observed. Chondrocyte viability significantly declined in both the en face and the vertical cross-sectional analysis with increased cold storage time and inversely correlated with fatty acid metabolites (P < .05).

CONCLUSION

It is well established that elevated levels of certain FFAs and lipid oxidation products can alter cell function and cause cell death via lipotoxicity and other mechanisms. This work is the first to identify elevated levels of FFA metabolites and primary oxidation lipid products in the storage media from clinical OCA. The concentrations of FFA metabolites were measured at levels (>100 µM) known to induce cell death and were directly correlated with chondrocyte viability.

CLINICAL RELEVANCE

These findings provide important targets for understanding why cartilage health declines during cold storage, which can be used to optimize media formulations and improve graft health.

Effect of storage media on chondrocyte viability during cold storage of osteochondral dowels

Osteochondral allograft transplantation is a successfully proven method to repair articular cartilage defects and prevent the degenerative effects of osteoarthritis. The number of osteochondral transplantations that can be performed each year is limited by availability of donor cartilage tissue and storage time constraints. Osteochondral transplantation success has been linked to high chondrocyte viability of the donor cartilage tissue at the time of implantation. Determining optimal storage conditions for donor cartilage is essential for tissue banks to safely provide quality cartilage tissue. In this study, we compared three tissue/cell media (DMEM/F12, RPMI-1640 and X-VIVO 10) for their ability to maintain chondrocyte viability during hypothermic storage for 28 days. Porcine osteochondral dowels were stored in each media for 28 days and cell viability was assessed every 7 days. Over the 28 day storage period, the chondrocyte viability of dowels stored in DMEM/F12, RPMI-1640, and X-VIVO 10 media all declined in a similar fashion. Our results show that all three media were equivalent in their ability to maintain cell viability of the cartilage tissue and provides rationale for the use of lower cost cell media (DMEM/F12 and RPMI-1640) for hypothermic storage of articular cartilage tissue.

Chondrocyte Viability of Particulated Porcine Articular Cartilage Is Maintained in Tissue Storage After Cryoprotectant Exposure, Vitrification, and Tissue Warming

OBJECTIVE

Vitrification of articular cartilage (AC) is a promising technique which may enable long-term tissue banking of AC allografts. We previously developed a 2-step, dual-temperature, multi-cryoprotectant agent (CPA) loading protocol to cryopreserve particulated AC (1 mm3 cubes). Furthermore, we also determined that the inclusion of ascorbic acid (AA) effectively mitigates CPA toxicity in cryopreserved AC. Prior to clinical translation, chondrocytes must remain viable after tissue re-warming and before transplantation. However, the effects of short-term hypothermic storage of particulated AC after vitrification and re-warming are not documented. This study evaluated the chondrocyte viability of post-vitrified particulated AC during a 7-day tissue storage period at 4 °C. We hypothesized that porcine particulated AC could be stored for up to 7 days after successful vitrification without significant loss of cell viability, and these results would be enhanced when cartilage is incubated in storage medium supplemented with clinical grade AA.

DESIGN

Three experimental groups were examined at 5 time points: a fresh control (only incubated in medium), a vitrified - AA group, and a vitrified + AA group (N = 7).

RESULTS

There was a mild decline in cell viability but both treatment groups maintained a viability of greater than 80% viable cells which is acceptable for clinical translation.

CONCLUSION

We determined that particulated AC can be stored for up to 7 days after successful vitrification without a clinically significant decline in chondrocyte viability. This information can be used to guide tissue banks regarding the implementation of AC vitrification to increase cartilage allograft availability.

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.

Cellular Enhancement of Frozen Meniscus Allograft Combining Native Meniscus and Mesenchymal Stromal Cell Injections

OBJECTIVE

This proof-of-concept study investigated an improved cell-based injection therapy combining mesenchymal stem cells (MSCs) and meniscus cells (MCs) to support superior meniscus allograft repopulation and early revival compared to injecting MSCs alone.

DESIGN

In this controlled laboratory study, frozen meniscus allograft samples were injected vertically with a cell suspension containing different ratios of MSCs and MCs or control (lactated ringers) and cultured for 28 days. Samples were analyzed weekly for cell viability, migration, and metabolism using histological and biochemical assays. Tissue medium was analyzed for matrix metalloproteinase (MMP) expression using zymography.

RESULTS

Cellular repopulation of frozen allografts injected with different cell suspensions was validated by immunohistochemistry. Significant higher DNA content was evidenced in grafts treated with suspensions of MCs or MC:MSC (1:4 ratio). Cell metabolic activity was significantly different between all treated groups and control group after 1 week. Allografts injected with MCs showed significantly more cell proliferation than injections with MSCs. MMP2 activity was detected in medium of all grafts cellularized with MCs with or without MSCs. Scanning electron microscopy (SEM) analysis showed resolution of the needle puncture, but not in the control group. Cell labeling of MCs upon injection of mixed MC:MSC suspensions revealed a gradual increase in the cell ratio.

CONCLUSIONS

The findings of this study establish that injection of MCs with or without MSCs enhances the cellularity of meniscus allograft to support early graft revival and remodeling.

Osteochondral Allograft Transplantation in the Shoulder: A Systematic Review of Indications and Outcomes

OBJECTIVE

To collate current literature pertaining to the published reports of indications for, and outcomes of, osteochondral allograft (OCA) transplantations in the shoulder so as to guide surgeons in the management of various etiologies of osteochondral lesions in this joint.

DESIGN

A systematic review of the current literature was performed in February 2022 in the PubMed, Cochrane, and EMBASE databases using specific search terms and predetermined inclusion/exclusion criteria.

RESULTS

One-hundred-twenty-three articles were initially identified, 30 full-text articles were assessed for eligibility, and 17 articles met inclusion criteria. Data were collected for study characteristics, etiology, lesion size/location, intervention/type of graft used, follow-up, and outcomes. In total, 83 shoulders were included (n = 83) in the review with an average follow-up of 45.7 months. Nine specific indications for OCA transplantation in the shoulder included: reverse Hill-Sachs lesions (33), Hill-Sachs lesions (22), pain pump chondrolysis (10), recurrent shoulder instability (7), osteoarthritis/degenerative changes (5), radiofrequency chondrolysis (2), prominent suture anchors (2), glenoid lesion (1), and osteochondritis dissecans (1). Seventeen patients had concomitant surgeries and two patients were lost to follow-up. Of the total 83 shoulders, 68 had favorable outcomes and 13 had unfavorable outcomes as determined by graft incorporation, pain scores, functionality/ROM, patient-reported satisfaction, and/or requirement for revision/arthroplasty. Of the 13 with unfavorable outcomes, a disproportionate number had concomitant surgeries and/or were performed for pain pump chondrolysis (6).

CONCLUSIONS

The use of OCAs appears to be a viable option for a variety of difficult-to-treat shoulder pathologies, particularly those characterized by isolated osteochondral injuries.

Characteristics and Clinical Outcomes After Osteochondral Allograft Transplantation for Treating Articular Cartilage Defects: Systematic Review and Single-Arm Meta-analysis of Studies From 2001 to 2020

Background

Osteochondral allograft transplantation (OCA) treats symptomatic focal cartilage defects with satisfactory clinical results.

Purpose

To comprehensively analyze the characteristics and clinical outcomes of OCA for treating articular cartilage defects.

Study Design

Systematic review; Level of evidence, 4.

Methods

We searched Embase, PubMed, Cochrane Database, and Web of Science for studies published between January 1, 2001, and December 31, 2020, on OCA for treating articular cartilage defects. Publication information, patient data, osteochondral allograft storage details, and clinical outcomes were extracted to conduct a comprehensive summative analysis.

Results

In total, 105 studies involving 5952 patients were included. The annual reported number of patients treated with OCA increased from 69 in 2001 to 1065 in 2020, peaking at 1504 cases in 2018. Most studies (90.1%) were performed in the United States. The mean age at surgery was 34.2 years, and 60.8% of patients were male and had a mean body mass index of 26.7 kg/m2. The mean lesion area was 5.05 cm2, the mean follow-up duration was 54.39 months, the mean graft size was 6.85 cm2, and the number of grafts per patient was 54.7. The failure rate after OCA was 18.8%, and 83.1% of patients reported satisfactory results. Allograft survival rates at 2, 5, 10, 15, 20, and 25 years were 94%, 87.9%, 80%, 73%, 55%, and 59.4%, respectively. OCA was mainly performed on the knee (88.9%). The most common diagnosis in the knee was osteochondritis dissecans (37.9%), and the most common defect location was the medial femoral condyle (52%). The most common concomitant procedures were high tibial osteotomy (28.4%) and meniscal allograft transplantation (24.7%). After OCA failure, 54.7% of patients underwent revision with primary total knee arthroplasty.

Conclusion

The annual reported number of patients who underwent OCA showed a significant upward trend, especially from 2016 to 2020. Patients receiving OCA were predominantly young male adults with a high body mass index. OCA was more established for knee cartilage than an injury at other sites, and its best indication was osteochondritis dissecans. This analysis demonstrated satisfactory long-term postoperative outcomes.