Objective—To develop an in vitro model of cartilage injury in full-thickness equine cartilage specimens that can be used to simulate in vivo disease and evaluate treatment efficacy.
Sample—15 full-thickness cartilage explants from the trochlear ridges of the distal aspect of the femur from each of 6 adult horses that had died from reasons unrelated to the musculoskeletal system.
Procedures—To simulate injury, cartilage explants were subjected to single-impact uniaxial compression to 50%, 60%, 70%, or 80% strain at a rate of 100% strain/s. Other explants were left uninjured (control specimens). All specimens underwent a culture process for 28 days and were subsequently evaluated histologically for characteristics of injury and early stages of osteoarthritis, including articular surface damage, chondrocyte cell death, focal cell loss, chondrocyte cluster formation, and loss of the extracellular matrix molecules aggrecan and types I and II collagen.
Results—Compression to all degrees of strain induced some amount of pathological change typical of clinical osteoarthritis in horses; however, only compression to 60% strain induced significant changes morphologically and biochemically in the extracellular matrix.
Conclusions and Clinical Relevance—The threshold strain necessary to model injury in full-thickness cartilage specimens from the trochlear ridges of the distal femur of adult horses was 60% strain at a rate of 100% strain/s. This in vitro model should facilitate study of pathophysiologic changes and therapeutic interventions for osteoarthritis.
Objective—To determine the distribution for limbs and bones in horses with fractures of the proximal sesamoid bones and relationships with findings on palmarodorsal radiographic images.
Sample Population—Proximal sesamoid bones obtained from both forelimbs of cadavers of 328 racing Thoroughbreds.
Procedure—Osteophytes; large vascular channels; and fracture location, orientation, configuration, and margin distinctness were categorized by use of high-detail contact palmarodorsal radiographs. Distributions of findings were determined. Relationships between radiographic findings and fracture characteristics were examined by use of χ2 and logistic regression techniques.
Results—Fractures were detected in 136 (41.5%) horses. Biaxial fractures were evident in 109 (80%) horses with a fracture. Osteophytes and large vascular channels were evident in 266 (81%) and 325 (99%) horses, respectively. Medial bones typically had complete transverse or split transverse simple fractures, indistinct fracture margins, > 1 vascular channel that was > 1 mm in width, and osteophytes in abaxial wing and basilar middle or basilar abaxial locations. Lateral bones typically had an oblique fracture and distinct fracture margins. Odds of proximal sesamoid bone fracture were approximately 2 to 5 times higher in bones without radiographic evidence of osteophytes or large vascular channels, respectively.
Conclusions and Clinical Relevance—Biaxial fractures of proximal sesamoid bones were common in cadavers of racing Thoroughbreds. Differences between medial and lateral bones for characteristics associated with fracture may relate to differences in fracture pathogeneses for these bones. Osteophytes and vascular channels were common findings; however, fractures were less likely to occur in bones with these features.