Artrodese parcial tarsometatársica com uso de fixador esquéletico externo circular em cão / Tarsometatarsal Partial Arthrodesis with Use of Circular Skeletal Fixator on a Dog

ABSTRACT

Background: Trauma to the canine foot may result in injury to soft tissue or bone or both. Foot injury often results in fractures and joint instability because of disruption to carpal or tarsal ligaments. Several fixation methods have been described for stabilizing tarsometatarsal arthrodesis. The aim of this paper is to report the case of a unilateral tarsometatarsal arthrodesis with use of circular skeletal fixator on the left pelvic limb of a dog. Case A 5-year-old intact male dog weighting 25 kg was referred to the veterinary hospital with a left tarsal degloving injury. The previous history revealed that the dog had been bitten by another dog seven days prior to the referral. On physical exam it had swelling and severe pain on the left foot, crepitus of the intertarsal/tarsometatarsal region, instability, bone exposure and myiasis larvae on the wound. The dog was non-weight-bearing on the affected limb. No other abnormalities were found. Radiographs revealed it to be an open fracture of the left tarsal distal line with tarsometatarsal luxation. Adherent dressings were changed for seven days to minimize the contamination before surgery. The dog was treated by open reduction and internal fixation using a circular skeletal fixator. After general anesthesia was induced, a lateral approach to the tarsometatarsal joint was made. The tarsometatarsal joint then was exposed. Articular cartilage was removed with a pneumatic burr. Manual reduction was performed. There were placed two rings proximal to the fracture and one distal with Kirschner wires were angled 45° between them through the bone. One of them was a semi-ring in the shape of a horseshoe. The 1,5 mm Kirschner wires were tensioned by a dynamometer loaded at 30 kg. For wound closure a free skin graft from the thorax was used. Articular anchylosis was reached in three months but the implant removal was posterior to that time due to the owner's choice. Discussion: Traumatic injury is the most important cause for fracture and instability of the tarsometatarsal joint and was the cause of injury for this case. Partial arthrodesis is considered the treatment of choice for tarsal instabilities with ligament disruption. Implant problems following union can complicate arthrodeses stabilized with internal fixation, and they may require a second surgery for implant removal. In this case the size of the rings conformed well to the proximal tarsus, and allowed sufficient space for wire placement in the metatarsal bones and did not interfere with ambulation. The dog recovered good limb function soon after the surgery and articular anchylosis was reached within three months as expected. In a study three of ten dogs undergoing tarsometatarsal arthrodesis due to continued lameness after bony union, using a laterally applied plate required a second surgery for implant removal. Implant failure is a common complication of tarsocrural and tarsometatarsal arthrodeses stabilized with bone screws, Steinmann pins or plate fi xation. Tarsometatarsal partial arthrodesis with use of circular skeletal fixator is a proper option for contaminated wounds without enough skin for closure. The limiting factor is the surgeon experience for this choice of fixation, material availability and the owner's commitment with the treatment.