Third tarsal bone osteonecrosis associated with chronic recurrent cellulitis in an adult horse

Abstract

Summary A 17‐year‐old Irish Draught cross gelding with a history of chronic recurrent right hindlimb cellulitis was evaluated due to acute onset of severe lameness affecting this limb. Scintigraphic examination identified marked radiopharmaceutical uptake within the central and third tarsal bones and the lameness improved following tibial and peroneal nerve blocks. Distal intertarsal joint collapse was observed but the radiographic changes were considered insufficient to explain the lameness severity. Magnetic resonance imaging revealed marked bone pathology affecting both the central and third tarsal bones. A subcutaneous abscess developed on the dorsolateral aspect of the limb, but clear evidence of joint infection was not established. Computed tomography showed lytic lesions affecting mainly the third tarsal bone, so the animal was treated surgically for suspected osteomyelitis involving this bone by implantation of gentamicin impregnated polymethylmethacrylate. Shortly following surgery the horse developed gastric rupture and was euthanased. Osteonecrosis of the third tarsal bone was identified, but sepsis was not demonstrated to be the cause. It is hypothesised that osteonecrosis developed as a sequel to chronic osteomyelitis which may have responded to previous antimicrobial treatment. The report also highlights the importance of gastric disorders as a differential for discomfort in animals undergoing treatment for orthopaedic disease.

Focal peritarsal cellulitis with long digital extensor tenosynovitis

“…The variation in LoDETS synovial fluid from inflammatory to septic in nature suggests that pathology within the sheath is most likely secondary to the adjacent cellulitis. Bacterial translocation from cellulitis to adjacent structures, particularly underlying bone, has been previously reported (Markel et al 1986;Pilsworth and Head 2001;O'Brien et al 2019). The extension of infection from cellulitic tissue to bone is assumed to have been the pathogenesis of disease in Case 7.…”

“…The decision to sample the LoDETS in all cases, in the face of cellulitis, was justified by the presence of abnormal ultrasonographic findings, in combination with the severity of clinical signs. In parallel with the reported risk of natural translocation of bacteria to underlying structures (Markel et al 1986;Pilsworth and Head 2001;O'Brien et al 2019), there is a reported risk of iatrogenically introducing infection into a synovial structure when performing synoviocentesis through cellulitic tissue (Smyth et al 2015). To decrease the risk of iatrogenic infection, intrasynovial antibiotics were instilled in all cases after sampling.…”

“…1986; Pilsworth and Head 2001; O'Brien et al . 2019). The extension of infection from cellulitic tissue to bone is assumed to have been the pathogenesis of disease in Case 7.…”

“…1986; Pilsworth and Head 2001; O'Brien et al . 2019), there is a reported risk of iatrogenically introducing infection into a synovial structure when performing synoviocentesis through cellulitic tissue (Smyth et al . 2015).…”