Subchondral bone sequestrum formation in the proximal intra-articular and osteochondral region of the third metatarsal bone of an Appaloosa mare treated for septic arthritis.

The study discusses the formation of subchondral bone sequestrum, a situation uncommon but possible, in the joint of a horse’s foot resulting from a wound infection. The researchers highlight the benefits of arthroscopic lavage and advanced imaging for early detection and treatment.

Overview of the Study

• This research involves a 12-year-old Appaloosa mare owned by a participant client. The incident started with a wound on the lateral aspect of the mare’s fourth metatarsal bone (MT4). This wound had a direct connection with the distal tarsal joints.
• Radiographic examination highlighted a displaced, multi-piece (comminuted) fracture in the MT4.

Treatment and Results

• To treat this condition, strong debridement of the wound and the MT4 was carried out on the horse. The horse also underwent needle joint lavage, a form of joint cleansing, on two separate occasions.
• Moreover, antibiotic therapies, including systemic, regional, and intra-articular (IA), were implemented. A bone graft from the raised prominence on the pelvis (tuber coxae) was also performed.
• The horse showed signs of recovery. Both its comfort and the wound’s healing process saw noticeable improvement. However, five weeks after being discharged, the horse returned with a severe level of lameness where it could not bear any weight. Subsequent radiographs revealed a severe inflammation, specifically osteomyelitis, of the horse’s tarsometatarsal and distal intertarsal joints.
• A postmortem limb examination led to the discovery of a sequestrum, a piece of dead bone separated from healthy bone typically due to disease, in the proximal articular surface of the third metatarsal bone.

Conclusions and Recommendations

• The authors of the study emphasize the significance of undergoing arthroscopic lavage. This technique is useful in visualizing the cartilage surface, which further aids in understanding the severity and extent of the injury.
• Furthermore, they urge for the usage of advanced imaging techniques as these could detect changes within the bone structure earlier compared to traditional radiographs.
• To the researchers’ knowledge, there have been no other reports of intra-articular subchondral bone sequestra in the tarsometatarsal joint in horses. Hence, this study serves as an important reference for this specific case, potentially serving as a prelude for upcoming research and treatment methods.