HISTORY

A five-years old male intact Boxer was referred to our VTH with a history of intermittent lameness during the last year and swelling of the tarsus since the last three months. The dog had a diagnosis of leishmaniosis (two years ago) and hypothyroidism (one year ago). He had been treated with allopurinol and levo-thyroxine since then. Serology to E. canis and Lyme was negative. Bone biopsy and synovial fluid analysis revealed bone neoformation with signs of mixed arthritis.

At physical examination, a mild popliteal lymphadenopathy on the left hind limb and cutaneous lesions of the ears and nose were observed. Our diagnostic plan included a CBC, biochemistry, urinalysis, protein/creatinine ratio, T4, TSH, leishmaniosis serology, tarsal and thoracic radiographs, immunohistochemistry of leishmania from the bone biopsy and a bone cytology. Radiographic exploration showed a moderate bone lysis and periosteal reaction of the tarsal bones. Leishmania amastigotes were seen within the macrophages in the bone cytology.

Meglumine antimonate during 30 days was added to the allopurinol treatment. The dog showed a progressive improvement of the clinical signs and started to weigh bear on the affected limb. The radiographic changes of the tarsus were similar to that observed previously, except for an increase of the osteolytic lesions. The increase of bone destruction and the beginning of weight bearing lead on the necessity to perform a partial midtarsal arthrodesis due to the risk of a tarsal pathologic fracture.

DISCUSSION

Although Leishmaniosis is a very frequent disease in the Mediterranean countries and their clinical sings can be very varied, it is unusual that it causes osteomyelitis. Medical therapy based on meglumine antimonate and allopurinol may improve the clinical signs. However, in our clinical case, the severity of the osteolytic lesions could lead to a tarsal pathological fracture and some orthopaedic measures were necessary. Although from the orthopaedic and biomechanical point of view, a complete tarsal-metatarsal arthrodesis could be a better option, a partial midtarsal arthrodesis was selected in order to limit the iatrogenic damage in a already severely affected joint. A simple pin arthrodesis provides good stability with minimal soft tissue and bone damage comparing with a plated arthrodesis. No figure-in-eight wire was applied on the pin to achieve a tension band effect because it could cause an inadequate increase of stress forces against the plantar surface of the joint, where the osteolytic lesions of the calcaneus were present.