BRAXTON CHAN

Age 17 | Cranbrook, BC

Edited by Nicole Yoannou

VIEW PDF

INTRODUCTION

Osteochondral defects (OCD) refer to a focal area of damage over the surface of an articular joint resulting in the loss of cartilage and bone. OCD is the result of acute trauma or an underlying bone disorder. This creates a painful joint.

Fibrocartilage is a dynamic tissue found at the insertions of ligaments and tendons. It contains cartilage ground substance and chondrocytes. Fibrocartilage is unique as it has a high propensity to reattach to its insertion site if it is surgically repaired. The anterior cruciate ligament in the knee joint and the labrum in the hip joint are good fibrocartilage sources.

I previously published the result of a novel treatment for osteochondral defects using human fibrocartilage transplantation (Chan, 2020). In that study, the fibrocartilage transplant was shown to adhere to the OCD. The transplant tissue remained viable, and its capacity to osteoappose with the trabecular bone of the OCD was evident at seven weeks post-transplantation. Material testing supported the ability of the transplant to absorb the stresses required for weight-bearing.

By providing a biological substitute for the articular cartilage loss in OCD, the fibrocartilage transplant can postpone the need for multiple artificial joint replacements. This is particularly important as OCD tends to occur in younger patients with the highest incidence between 11 and 15 years. The overall age- and gender-adjusted annual incidence of knee OCD lesions has been reported as 6.09 per 100,000 person-years. This can lead to a lifetime of joint pain and dysfunction (Pareek et al, 2017). Unfortunately, joint replacements in younger patients often require multiple revisions with less predictable outcomes.

To determine the viability of human fibrocartilage transplantation for OCD, long-term evidence is needed to confirm transplant tissue viability, functional capacity and tissue integration. In this present study, histological and biomechanical studies were undertaken after one year following the transplantation procedure to determine the long-term outcome of this treatment.

METHODS & MATERIALS

Study Design
Human knee and hip joints with osteochondral defects were transplanted with fibrocartilage tissue one year ago. Histological and biomechanical studies were used to examine the fibrocartilage tissue transplanted into the osteochondral defects.

Procedure
For this research project, consent was acquired from 11 patients undergoing total joint replacements (hips or knees) to donate their old natural joints. A segment of the joints were selectively harvested that contained an area of intact articular cartilage surface. A curette was used to create an osteochondral defect by removing all the cartilage and underlying superficial bone layer (Figure 1). During the harvesting of the hip or knee joints at the time of surgery, the labrum or anterior cruciate ligament (ACL) was also excised.

The excised labrum or anterior cruciate ligament was shaped using a surgical blade to match the size of the osteochondral defect. This tissue was then positioned into the OCD and secured onto the underlying bone using a biodegradable 2.0mm suture anchor with ultrabraid sutures (Smith and Nephew) (Figure 1).

The joint was kept moist throughout the procedure by irrigation with an isotonic phosphate-buffered saline (PBS) solution. This solution was used to maintain tissue viability. All joints were stored for one year at a temperature of 4˚C to 6˚C in the biopreservative X-VIVO-10 (Lonza) as recommended by Lonza. This is a commercially available product used for tissue preservation in clinical tissue banks. After one year, the joint samples underwent Materials Testing and Histological Analysis.

Beslands HF-500N Digital Force Gauge Push and Pull Dynamometer was used to perform compression load testing. The joint samples were load tested in a hydrated environment (with PBS) at room temperature. The fibrocartilage transplant was oriented perpendicular to the force gauge indenter. This allows for an axial compression measurement while limiting shear loading. Force measurements were performed on the fibrocartilage transplant and on the adjacent intact articular cartilage. Repeat measurements were performed allowing the tissue to relax in between measurements.

The joints were then preserved in 10% buffered formalin solution. When ready for histological examination, the samples were decalcified, dehydrated and embedded in paraffin. The specimens were cut longitudinally and 5 micron sections mounted for staining with hematoxylin and eosin (Cardiff et al., 2014).

RESULTS

Gross pathological examination shows that the fibrocartilage transplant is well-adhered into the osteochondral defect after one year (Figure 2). Cross-sectional observation of the gross specimen demonstrates a seamless apposition of the two surfaces. This is even more apparent compared to the gross pathological examination of the specimens at seven weeks post-transplantation.

The peak compression force of the fibrocartilage transplant was shown to be similar to the adjacent intact articular cartilage (two-way ANOVA, SS=687.45, df=30, MS=22.92, F=0.018, p=0.895) (Figure 3). As the p-value is greater that 0.05, this statistically confirms no difference in the peak compression force measurements. Therefore, both the fibrocartilage transplant and the normal articular cartilage show comparable findings.

Histological examination shows the progression of the osteoapposition of the fibrocartilage transplant tissue into the osteochondral defect from 7 weeks to 52 weeks post-transplantation. In the early phase, a fibrovascular interface forms. This interface then disappears over time, allowing for further contact of the fibrocartilage transplant onto the osteochondral defect. At 52 weeks, the integration of the fibrocartilage into the OCD is remarkable, with the two surfaces interlocking with each other (Figure 4).

DISCUSSION

The process of tissue integration onto bone is fundamentally dependent on vascular supply, protein synthesis and mineralization. In the initial phase of transplantation, there is the formation of coagulate that loosely bonds the recipient and donor tissue. The fibroblasts, chondroblasts and osteoblasts then create a new fibrovascular tissue that replaces the initial coagulate. This was seen histologically at seven weeks following the fibrocartilage transplantation.

As transplant integration occurs, the fibrovascular tissue will ultimately become calcified to develop into fibro-osseous tissue. This appositional new bone formation is dependent on the vascularization of the tissue. If the fibrovascular tissue remains, it will prevent the reparative phase of fibre-osseous union.

This study provides long-term biomechanical and histological evidence that human fibrocartilage transplants are a viable solution for Osteochondral defects in articular joints. In this study, the histological findings clearly show the interlocking of the transplanted tissue into the OCD. This definitively demonstrates the progression of the fibrocartilage transplant integrating into the osteochondral defect after 52 weeks. This provides strong evidence that this novel surgical technique can provide a long-term mechanical and biological solution for treating osteochondral defects.

Clinical trials will need to be undertaken to determine whether this novel transplantation technique can treat patients with known osteochondral defects. These patients are suffering from significant pain and have failed all other available treatment modalities. The surgical procedure to transplant the fibrocartilage can be performed arthroscopically. This means the surgery is minimally invasive and can be performed as an outpatient procedure. The fibrocartilage transplant can be readily harvested with ease from the ipsilateral affected limb. It would not compromise the patient's function or require allograft precautions. Importantly, tissue rejection, as seen with allograft transplantation, would not occur with autograft transplantation.

REFERENCES

Cardiff, R.D., Miller, C.H., Munn, R.J. (2014). Hematoxylin and Eosin Staining of Tissue and Cell Sections. Cold Spring Harbor Protocols, doi:10.1101/pdb.prot073411.

Chan, B.H.F. (2020). Human Fibrocartilage Transplantation for Osteochondral Defects. The Canadian Science Fair Journal, 3(3).

Pareek, A., Sanders, T.L., Wu, I.T., Larson, D.R., Krych, A.J. (2017). Incidence of Symptomatic Osteochondritis Dissecans Lesions of the Knee: A Population-Based Study in Olmsted County. Osteoarthritis Cartilage, 25(10): 1663-1671.

ACKNOWLEDGEMENTS

I would like to thank Smith and Nephew Canada for their suture anchors.

Long-term results of a Novel Surgical Procedure for Osteochondral Defects