True lateral positioning of the tibia defined by superimposition of the femoral and tibial condyles should be used for accurate TPA determination before tibial plateau leveling osteotomy.
Chronic degeneration of articular cartilage and bone in a rabbit model of post-traumatic osteoarthrosis has been hypothesized to occur due to acute stresses that exceed a threshold for injury. In this study, we impacted the rabbit patellofemoral joint at low and high intensities. High-intensity impacts produced degenerative changes in the joint, such as softening of retropatellar cartilage, as measured by indentation, an increase in histopathology of the cartilage, and an increase in thickness of subchondral bone underlying the cartilage. Low-intensity impacts did not cause these progressive changes. These data suggest that low-intensity impacts produced acute tissue stresses below the injury threshold, while high-intensity impacts produced stresses that exceeded the threshold for disease pathogenesis. This study begins to identify "safe" and "unsafe" ranges of acute tissue stress, using the rabbit patella, which may have future utility in the design of injury prevention devices for the human.
Post-traumatic osteoarthritis (PTOA) develops as a result of traumatic loading that causes tears of the soft tissues in the knee. A modified transection model, where the anterior cruciate ligament (ACL) and both menisci were transected, was used on skeletally mature Flemish Giant rabbits. Gross morphological assessments, elastic moduli, and glycosaminoglycan (GAG) coverage of the menisci were determined to quantify the amount of tissue damage 12 weeks post injury. This study is one of the first to monitor meniscal changes after inducing combined meniscal and ACL transections. A decrease in elastic moduli as well as a decrease in GAG coverage was seen.
Subchondral bone is thought to play a significant role in the initiation and progression of the post-traumatic osteoarthritis. The goal of this study was to document changes in tibial and femoral subchondral bone that occur as a result of two lapine models of anterior cruciate ligament injury, a modified ACL transection model and a closed-joint traumatic compressive impact model. Twelve weeks post-injury bones were scanned via micro-computed tomography. The subchondral bone of injured limbs from both models showed decreases in bone volume and bone mineral density. Surgical transection animals showed significant bone changes primarily in the medial hemijoint of femurs and tibias, while significant changes were noted in both the medial and lateral hemijoints of both bones for traumatic impact animals. It is believed that subchondral bone changes in the medial hemijoint were likely caused by compromised soft tissue structures seen in both models. Subchondral bone changes in the lateral hemijoint of traumatic impact animals are thought to be due to transmission of the compressive impact force through the joint. The joint-wide bone changes shown in the traumatic impact model were similar to clinical findings from studies investigating the progression of osteoarthritis in humans.
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