Osteochondral allografts in the treatment of articular cartilage injuries of the knee

Mechanical Properties of Fresh, Frozen and Vitrified Articular Cartilage

Osteochondral allograft transplantations are typically used to treat focal articular cartilage injuries where the damaged cartilage is replaced with fresh cadaveric donor grafts. Despite the notable success rate of this procedure, it is limited by fresh donor tissue availability which can only be stored for approximately 28 days after harvest. Vitrification, a form of cryopreservation, can extend the storage time of cartilage. Although it has shown to preserve chondrocyte viability, its effect on the mechanical properties of the tissue has not been thoroughly investigated. Therefore, in this study, the mechanical properties of fresh, frozen, and vitrified articular cartilage were evaluated through unconfined compression testing. Results showed that the peak modulus, equilibrium modulus, and relaxation time constants of the vitrified and control samples (tested one day after harvest) were similar and higher than the fresh (tested 21 days after harvest) and frozen samples. This demonstrated that vitrification does not adversely affect the mechanical properties of cartilage and can be used as an alternative to fresh allografts which are limited by storage time. The fresh samples also had inferior mechanical properties compared to the control samples suggesting that vitrified allografts could potentially improve clinical outcomes in addition to increasing donor tissue availability.

Quality and Variability of Physical Therapy Protocols Varies Widely for Osteochondral Allograft Transplantation of the Femoral Condyles

OBJECTIVE

To assess the quality and variability of osteochondral allograft (OCA) transplantation rehabilitation protocols associated with academic orthopedic programs in the United States.

DESIGN

A systematic review was performed to collect all publicly available online rehabilitation protocols for femoral condyle OCA transplant from US academic orthopedic programs participating in the Electronic Residency Application Service. These protocols were evaluated for inclusion of different rehabilitation components as well as timing of suggested initiation of these activities.

RESULTS

A total of 22 protocols were included. Although 91% of protocols recommended bracing, wide variation exists in total time of utilization. Median time for full weight bearing (FWB) was 7 weeks (range 4-8). On average, each protocol mentioned 9 (range 2-18) different strengthening exercises. The median time suggested to return to high-impact activities was 9 months (range 8-12). Only 3 protocols (14%) offered criteria of advancement for each phase as well as criteria for discharge.

CONCLUSION

Very few of the academic orthopedic programs have published online rehabilitation protocols following OCA transplantation. Although there is wide variation between the protocols, it allowed the identification of trends or patterns that are more common. However, there is need for more standardized evidence-based rehabilitation protocols which are easy to understand and follow by patients.

Topographic Analysis of Lateral Versus Medial Femoral Condyle Donor Sites for Oblong Medial Femoral Condyle Lesions

PURPOSE

To analyze the topographic matching of oblong osteochondral allografts to treat large oval medial femoral condyle (MFC) lesions using computer simulation models. The secondary objective was to determine whether lateral femoral condyle (LFC) grafts would have a similar surface matching when compared with MFC grafts in this setting.

METHODS

Human femoral hemicondyles (10 MFCs, 7 LFCs) underwent 3-dimensional computed tomography. Models were created from computed tomography images and exported into point-cloud models. Donor-recipient matches with large condylar width mismatch were excluded. The remaining specimen were divided into 3 donor-recipient groups with 2 defect sizes (17 × 30 mm and 20 × 30 mm): 20 MFC donor (MFCd)-MFC recipient (MFCr), 27 ipsilateral LFC donor (LFCd)-MFCr, and 26 contralateral LFCd-MFCr. Grafts were optimally virtually aligned with the MFCr defect. Mismatch of the articular cartilage and subchondral bone surfaces between the graft and the defect and articular step-off were calculated.

RESULTS

MFCd grafts resulted in articular cartilage surface mismatch and peripheral step of less than 0.5 mm for both defect sizes. The subchondral bone surface mismatch was significantly greater than the articular cartilage surface mismatch (P < .01) in both defect sizes). Conversely, the ipsilateral and contralateral LFCd grafts resulted in significantly greater articular cartilage surface mismatch and step-off for both defect sizes when compared to MFCd grafts (P < .01).

CONCLUSIONS

Oblong MFC allografts provide acceptable topographic matching for large oval MFC lesions when condylar width differences are minimized. However, concern exists in using oblong LFC allografts for MFC defects, as this can result in increased peripheral step-off and surface mismatch.

CLINICAL RELEVANCE

These data reinforce the ability to use oblong MFC osteochondral allograft for treating oval cartilage lesions of the MFC when condylar width is considered. Although other studies have demonstrated LFCs can be used to treat circular defects on the MFC, this may not be true for oblong grafts.

Rehabilitation and Postoperative Management Practices After Osteochondral Allograft Transplants to the Distal Femur: A Report From the Metrics of Osteochondral Allografts (MOCA) Study Group 2016 Survey

Context:

We present the current spectrum of postoperative management practices for patients receiving distal femur osteochondral allograft (OCA) transplants.

Evidence Acquisition:

The Joint Restoration Foundation database was examined in cooperation with the Metrics of Osteochondral Allografts study group to identify 121 surgeons who had performed at least 1 OCA transplant in the past year; 63% of surgeons responded.

Study Design:

Clinical survey.

Level of Evidence:

Level 3.

Results:

Postoperative weightbearing restrictions ranged from immediate nonweightbearing with full weightbearing by 12 weeks to immediate weightbearing as tolerated. Most surgeons who performed fewer (<10) OCA transplants per year followed the most restrictive protocol, while surgeons who performed more (>20) OCA transplants per year followed the least restrictive protocol. One-third of surgeons with the most restrictive protocol were more likely to change their protocol to be less restrictive over time, while none of those with the least restrictive protocol changed their protocol over time. Fifty-five percent of surgeons permitted return to full activity at 26 weeks, while 27% of surgeons lifted restrictions at 16 weeks.

Conclusion:

Characterization of the spectrum of postoperative management practices after OCA transplantation provides a foundation for future investigations regarding patient outcomes and associated cost to establish best practice guidelines. Fundamentally, surgeons with more experience with this procedure tended to be more aggressive with their postoperative rehabilitation guidelines. Most commonly, rehabilitation provided for some degree of limited weightbearing; however, the spectrum also included immediate full weightbearing practices.

Large osteochondral lesions of the femoral condyles: Treatment with fresh frozen and irradiated allograft using the Mega OATS technique

BACKGROUND

The purpose of this study was to review the clinical results of irradiated fresh frozen osteochondral allografts for large osteochondral defects of the knee using the Mega-OATS technique.

METHODS

Nine patients with a mean age of 32.1±6.6 (18 to 44) underwent Mega-OATS transplantation with irradiated (2.5Mrad), fresh frozen distal femur allograft. Three patients also underwent ACL-reconstruction; one patient a high tibial osteotomy. The underlying indication was osteochondrosis dissecans in four and trauma in five patients. The defect size was 25×25mm in three patients and 30×30 in six patients and the depth ranged from eight to 14mm. All OCD lesions were located on the medial femoral condyle; two of the traumatic lesions were located on the lateral femoral condyle. Clinical outcome was assessed using the Lysholm and IKDC scores. Radiographic incorporation was evaluated using serial radiographs and MR imaging at one year post surgery. All patients were reviewed at three, six, 12, and 24months following surgery.

RESULTS

The Lysholm (IKDC) score improved significantly (p=0.02 resp. p=0.007) within and between patients during the follow-up period from 40.9 (37) to 90.9 (87.1) at 2years. Radiographic union was observed in all patients at three months; on MR imaging at one year osseous integration was observed in eight patients. Graft subsidence with loss of the overlying cartilage was observed in one and subchondral cystic changes at the implantation side were seen in another patient.

CONCLUSION

The results of this case series suggest that irradiated osteochondral allograft provides significant medium-term clinical improvement in patients treated for large osteochondral lesions of the femoral condyles.

LEVEL OF EVIDENCE

IV, case series.

Updates in biological therapies for knee injuries: full thickness cartilage defect

Full thickness cartilage defect might occur at different ages, but a focal defect is a major concern in the knee of young athletes. It causes impairment and does not heal by itself. Several techniques were described to treat symptomatic full thickness cartilage defect. Recently, several advances were described on the known techniques of microfracture, osteochondral allograft, cell therapy, and others. This article brings an update of current literature on these well-described techniques for full thickness cartilage defect.

Use of large osteochondral allografts in reconstruction of traumatic uncontained distal femoral defects

Large osteoarticular injuries with subchondral bone loss involving the knee in young active patients often result in significant morbidity and loss of normal joint function. A review of the current literature reveals that multiple surgical management options are currently employed, however there is no consensus on standard of care. Osteochondral allografting provides an attractive alternative treatment option for the repair of large articular defects of the knee.

METHODS

In this article we present the case of a young male who suffered traumatic intraarticular bone loss secondary to a grade IIIA distal femoral fracture and subsequently underwent reconstruction of his medial femoral condyle using a fresh-frozen osteochondral allograft.

RESULTS

We present the radiographic and functional outcome of this patient at two years post-operative. The range of motion of the knee was 0-130° and the patient's post-operative functional outcome was evaluated using the Knee injury and Osteoarthritis Outcome Score (KOOS), which was 76%.

CONCLUSIONS

While further research is required, the results of our case study concur with the current body of literature supporting the use of fresh-frozen osteochondral allograft as a reconstructive option for treating large traumatic intraarticular lesions involving the distal femur.

Basic science and surgical treatment options for articular cartilage injuries of the knee

The complex structure of articular cartilage allows for diverse knee function throughout range of motion and weight bearing. However, disruption to the structural integrity of the articular surface can cause significant morbidity. Due to an inherently poor regenerative capacity, articular cartilage defects present a treatment challenge for physicians and therapists. For many patients, a trial of nonsurgical treatment options is paramount prior to surgical intervention. In instances of failed conservative treatment, patients can undergo an array of palliative, restorative, or reparative surgical procedures to treat these lesions. Palliative methods include debridement and lavage, while restorative techniques include marrow stimulation. For larger lesions involving subchondral bone, reparative procedures such as osteochondral grafting or autologous chondrocyte implantation are considered. Clinical success not only depends on the surgical techniques but also requires strict adherence to rehabilitation guidelines. The purpose of this article is to review the basic science of articular cartilage and to provide an overview of the procedures currently performed at our institution for patients presenting with symptomatic cartilage lesions.

Management of focal chondral lesion in the knee joint

Articular cartilage does not contain vascular, nervous and lymphatic tissue and chondrocytes hardly participate in the healing or repair process of chondral tissue because of being surrounded by plenty of extracellular matrix. Therefore, the injury to articular cartilage frequently requires an operative treatment. The goal of surgical repair of articular cartilage is to regenerate nearly normal chondral tissue and prevent degenerative arthritis caused by the articular cartilage defect. Microfracture is a kind of cartilage repair procedure that makes a fibrin clot containing mesenchymal stem cells in the chondral lesion. Microfracture is a simple procedure but it has a disadvantage that the repaired tissue is fibrocartilage. Autologous chondrocyte implantation has an advantage that it implants fully differentiated chondrocytes to the lesion, which theoretically produces hyaline cartilage. Its disadvantages are that it is a two stage and a costly procedure. Osteochondral autograft transplantation is a one stage procedure and repairs the lesion with hyaline cartilage. But its limitation is the lack of donor site availability. Surgeons who understand the theoretical background, indications, surgical methods, rehabilitation, complications, and clinical course of cartilage repair procedures can achieve the goal of preventing degenerative arthritis.

Coculture of engineered cartilage with primary chondrocytes induces expedited growth

BACKGROUND

Soluble factors released from chondrocytes can both enhance and induce chondrocyte-like behavior in cocultured dedifferentiated cells. The ability to similarly prime and modulate biosynthetic activity of differentiated cells encapsulated in a three-dimensional environment is unknown.

QUESTIONS/PURPOSES

To understand the effect of coculture on engineered cartilage, we posed three hypotheses: (1) coculturing with a monolayer of chondrocytes ("chondrocyte feeder layer") expedites and increases engineered tissue growth; (2) expedited growth arises from paracrine effects; and (3) these effects are dependent on the specific morphology and expression of the two-dimensional feeder cells.

METHODS

In three separate studies, chondrocyte-laden hydrogels were cocultured with chondrocyte feeder layers. Mechanical properties and biochemical content were quantified to evaluate tissue properties. Histology and immunohistochemistry stains were observed to visualize each constituent's distribution and organization.

RESULTS

Coculture with a chondrocyte feeder layer led to stiffer tissue constructs (Young's modulus and dynamic modulus) with greater amounts of glycosaminoglycan and collagen. This was dependent on paracrine signaling between the two populations of cells and was directly modulated by the rounded morphology and expression of the feeder cell monolayer.

CONCLUSIONS

These findings suggest a potential need to prime and modulate tissues before implantation and present novel strategies for enhancing medium formulations using soluble factors released by feeder cells.

CLINICAL RELEVANCE

Determining the soluble factors present in the coculture system can enhance a chondrogenic medium formulation for improved growth of cartilage substitutes. The feeder layer strategy described here may also be used to prime donor cartilage allografts before implantation to increase their success in vivo.

Biological and Biomechanical Evaluations of Osteochondral Allografts Preserved in Cold Storage Solution Containing Epigallocatechin Gallate

The beneficial effects of (-)-epigallocatechin-3- O-gallate (EGCG) on the nonfrozen preservation of mammalian cells and tissues are generally not well understood. A storage solution containing EGCG was employed to test the hypothesis that EGCG is capable of extending the storage duration for the cold preservation of articular cartilages. Human articular cartilages were preserved in a storage solution composed of serum-free RPMI-1640 medium with 1% antibiotic-antimycotic solution and 1 mM EGCG at 4°C for 1, 2, and 4 weeks. The chondrocyte viability (CCK-8 assay), biochemical and immunohistochemical composition [glycosaminoglycans (GAG) and (type II) collagen], and biomechanical property (compressive elastic modulus) were assessed. The chondrocyte viability of the cartilages preserved with EGCG was significantly well maintained for at least 2 weeks with high content of GAG and total collagen. These beneficial effects of EGCG were confirmed by the immunohistochemical observations of well-preserved cartilaginous structures and delayed denaturation of the extracellular matrix in preserved cartilages. There was no significant difference in the compressive elastic modulus (MPa) between the cartilages preserved with and without EGCG. These results suggest that EGCG may play an effective role in preserving osteochondral allografts, which can be exploited in devising strategies for the long-term preservation of other tissues under cold storage conditions.

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

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

Osteochondral allografts: state of the art

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