Effects of exercise vs experimental osteoarthritis on imaging outcomes

SummaryObjectiveTo identify changes in imaging outcomes in a controlled model of osteoarthritis (OA) vs exercise.MethodSixteen 2-year-old horses were randomly assigned to an exercise control (n=8) or an exercise OA (n=8) group. All horses had middle carpal joints arthroscopically explored and an osteochondral fragment was induced in one middle carpal joint of the OA group. All horses were treadmill exercised for the duration of the study (91 days). Clinical, radiographic, nuclear scintigraphic, computed tomographic and magnetic resonance imaging (MRI) examinations were performed and outcomes of these were compared between groups. Imaging results were correlated to clinical, biomarker and gross pathologic results.ResultsThe OA group had significant increases in clinical outcomes and most imaging parameters. Specifically, the OA group showed significant increases in radiographic lysis and nuclear scintigraphic uptake. There was very little change in subchondral bone density, but a significant change in subchondral bone edema. Radiographic lysis, radial carpal bone edema and nuclear scintigraphy were strongly correlated with clinical changes and radial carpal bone edema was strongly correlated with changes in Type I and Type II collagen found in the synovial fluid.ConclusionsOA induced significant changes in imaging parameters beyond the adaptation seen with exercise. Bone edema detected with MRI was closely correlated with collagen biomarkers detected in the synovial fluid

Qualitative assessment of bone density at the distal articulating surface of the third metacarpal in Thoroughbred racehorses with and without condylar fracture

Reasons for performing study: Changes in subchondral bone density, induced by the repetitive cyclical loading of exercise, may potentiate fatigue damage and the risk of fracture. Objectives: To use computed tomography (CT) to characterise bone density patterns at the articular surface of the third metacarpal bone in racehorses with and without lateral condylar fractures. Study Design: Case control Methods: Computed tomographic images of the distal articulating surface of the third metacarpal bone were obtained from Thoroughbred racehorses subjected to euthanasia in the UK. Third metacarpal bones were divided into 3 groups based on lateral condyle status; fractured (FX, n = 42), nonfractured contralateral condyle (NFX, n = 42) and control condyles from horses subjected to euthanasia for reasons unrelated to the third metacarpal bone (control, n = 94). Colour CT images were generated whereby each colour represented a range of pixel values and thus a relative range of bone density. A density value was calculated qualitatively by estimating the percentage of each colour within a specific region. Subchondral bone density was assessed in 6 regions from dorsal to palmar and 1 mm medial and lateral to the centre of the lateral parasagittal groove in NFX and control condyles and 1 mm medial and lateral to the fracture in FX condyles. Results: Bone density was significantly higher in the FX and NFX condyles compared with control condyles for all 6 regions. A significantly higher bone density was observed in FX condyles relative to NFX condyles in the lateral middle and lateral palmar regions. Fractured condyles had increased heterogeneity in density among the 6 regions of interest compared with control and NFX condyles. Conclusions: Adjacent to the fracture, a focal increase in bone density and increased heterogeneity of density were characteristic of limbs with lateral condylar fractures compared with control and NFX condyles. These differences may represent pathological changes in bone density that increase the risk for lateral condylar fractures in racehorses

Evaluation of autologous chondrocyte transplantation via a collagen membrane in equine articular defects – results at 12 and 18 months

SummaryObjectiveTo evaluate a technique of autologous chondrocyte implantation (ACI) similar to the other techniques using cell-seeded resorbable collagen membranes in large articular defects.MethodsAutologous cartilage was harvested arthroscopically from the lateral trochlear ridge of the femur in fifteen 3-year-old horses. After culture and expansion of chondrocytes the newly created ACI construct (autologous chondrocytes cultured expanded, seeded on a collagen membrane, porcine small intestine submucosa) was implanted into 15mm defects on the medial trochlear ridge of the femur in the opposite femoropatellar joint. Using two defects in each horse, the ACI technique was compared to collagen membrane alone (CMA) and empty cartilage defects (ECDs).ResultsArthroscopic evaluations at 4, 8, 12 and 18 months demonstrated that CMA was significantly worse compared to ACI or ECD treatments, with ACI having the best overall subjective grade. Overall raw histological scores demonstrated a significant improvement with ACI compared to either CMA or ECD treated defects and ACI defects had significantly more immunohistochemical staining for aggrecan than CMA or ECD treated defects (with significantly more type II collagen in ACI and ECD compared to CMA defects) at 12 and 18 months.ConclusionsHistologic and immunohistochemistry results from this long-term randomized study are particularly encouraging and demonstrate superiority with the ACI technique. Although there is no comparable study published with the traditional ACI technique in the horse (or with such a large defect size in another animal model), the use of a solid autologous cell-seeded-constructed implant would appear to offer considerable clinical advantages