Evaluation of experimental impact injury for inducing post-traumatic osteoarthritis in the metacarpophalangeal joints of horses.

OBJECTIVE: To determine whether a single contusive impact injury to the palmar aspect of the metacarpus would progress to post-traumatic osteoarthritis or palmar osteochondral disease in horses. ANIMALS: 12 horses. PROCEDURES: In each horse, an impact injury was created on the palmar aspect of the medial metacarpal condyle of 1 randomly chosen limb with an impactor device under arthroscopic and fluoroscopic guidance. The opposite limb was sham operated as a control. A low to moderate amount of forced exercise was instituted, and horses were evaluated clinically via lameness examinations weekly for 5 months, then biweekly until endpoint, with synovial fluid analysis performed at 0, 1, 2, 3, 4, 6, 8, and 10 months and radiography at baseline and endpoint. Macroscopic examination, micro-CT, and sample collection for cartilage viability and sulfated glycosaminoglycan content, histologic evaluation, immunohistochemical analysis, and fluorochrome analysis were performed following euthanasia at 1 (3 horses), 4 (4), and 8 to 10 (5) months after surgery. RESULTS: There was variability in impact lesion location, depth, and area on macroscopic inspection, but on histologic evaluation, cartilage defects were less variable. Mean sulfated glycosaminoglycan concentration from cartilage at the impact site was significantly lower than that at a similar site in control limbs. Higher concentrations of cartilage oligomeric matrix protein were observed in synovial fluid from impact-injured joints. CONCLUSIONS AND CLINICAL RELEVANCE: The impact injury method caused mild focal osteoarthritic lesions in the metacarpophalangeal joint, but did not progress to palmar osteochondral disease at this site. Repeated injury is probably required for the development of palmar osteochondral disease.

Concentrated bone marrow aspirate improves full-thickness cartilage repair compared with microfracture in the equine model.

BACKGROUND: The purpose of this study was to compare the outcomes of treatment with bone marrow aspirate concentrate, a simple, one-step, autogenous, and arthroscopically applicable method, with the outcomes of microfracture with regard to the repair of full-thickness cartilage defects in an equine model. METHODS: Extensive (15-mm-diameter) full-thickness cartilage defects were created on the lateral trochlear ridge of the femur in twelve horses. Bone marrow was aspirated from the sternum and centrifuged to generate the bone marrow concentrate. The defects were treated with bone marrow concentrate and microfracture or with microfracture alone. Second-look arthroscopy was performed at three months, and the horses were killed at eight months. Repair was assessed with use of macroscopic and histological scoring systems as well as with quantitative magnetic resonance imaging. RESULTS: No adverse reactions due to the microfracture or the bone marrow concentrate were observed. At eight months, macroscopic scores (mean and standard error of the mean, 9.4 + or - 1.2 compared with 4.4 + or - 1.2; p = 0.009) and histological scores (11.1 + or - 1.6 compared with 6.4 + or - 1.2; p = 0.02) indicated improvement in the repair tissue in the bone marrow concentrate group compared with that in the microfracture group. All scoring systems and magnetic resonance imaging data indicated that delivery of the bone marrow concentrate resulted in increased fill of the defects and improved integration of repair tissue into surrounding normal cartilage. In addition, there was greater type-II collagen content and improved orientation of the collagen as well as significantly more glycosaminoglycan in the bone marrow concentrate-treated defects than in the microfracture-treated defects. CONCLUSIONS: Delivery of bone marrow concentrate can result in healing of acute full-thickness cartilage defects that is superior to that after microfracture alone in an equine model. CLINICAL RELEVANCE: Delivery of bone marrow concentrate to cartilage defects has the clinical potential to improve cartilage healing, providing a simple, cost-effective, arthroscopically applicable, and clinically effective approach for cartilage repair.