The Use of Micronized Allograft Articular Cartilage (BioCartilage) and Platelet Rich Plasma to Augment Marrow Stimulation in an Equine Model of Articular Cartilage Defects

OBJECTIVES: Microfracture continues to be a dominant treatment strategy for symptomatic articular cartilage defects. Improving the histologic and clinical outcomes with biologic adjuncts offers promise to enhance this widely utilized technique. Specifically, the use of a novel scaffold that is potentially conductive and inductive such as micronized allograft articular cartilage (BioCartilage-BC) combined with platelet rich plasma (PRP) was investigated as an adjunct to microfracture in an equine model of articular cartilage defects. METHODS: Five adult horses were anesthetized and 2 - 10mm diameter full thickness cartilage defects were created in the trochlear ridge in both knees; one proximal (high load) and another distal (low load). In one knee, microfracture (MFx) followed by grafting with BioCartilage(BC). BioCartilage was mixed with PRP and injected into the defect with a touhey needle and sealed with fibrin under CO2 arthroscopy. The opposite limb served as a control and received MFx only. Horses were euthanized at 13 months post-operatively. Outcome was assessed with serial arthroscopy, 3T T2 and T1rho MRI, microCT, and histology. Statistics were performed using a mixed effect model with response variable contrasts. P≤0.05 was considered significant. RESULTS: No complications such as joint inflammation, infection or lameness were encountered. The score for overall repair (12=normal, 0=complete degeneration) in both the proximal and distal defects was significantly better in the BC group compared to MFx (proximal BC 7.4±0.51, MFx 4.8±.1; p=0.041)(distal BC 5.6±0.98, MFx 2.6±1.5; p=0.022). All significant findings on histology (100=normal, o=complete degeneration) were confined to the proximal, high load defects. Graft perimeter integration (BC 96±8.9, MFx 68±19; p=0.02), graft base integration (BC 100+/- 0.0, MFx 70±37;p=0.044), subchondral bone architecture under the graft (BC 66±18, MFx 34±16; p=0.050) and collagen type II BC 82+/-8, MFx 58±11; p=0.051. There were no significant differences between BC and MFx in MRI or uCT analyses. CONCLUSION: Micronized allograft articular cartilage (BioCartilage) and PRP improve cartilage repair compared to marrow stimulation alone in an equine model of articular cartilage defects. This technology offers promise for the use of homologous allograft tissue as a low-cost and safe augmentation procedure for traditional microfracture surgery.