Bilateral Rupture of the Peroneus Tertius Muscle in Bovine

Abstract

Background: The peroneus tertius muscle is responsible for tarsal flexion and coordinate extension of the stifle joint. The most common causes of rupture are excessive effort when trying to rise on a slippery surface, mounting, or being mounted. Rupture of the peroneus tertius muscle is characterized by an inability to flex the hock. Most cases are not curable, presenting an unfavorable to poor prognosis, and the animal has to be euthanized. This study aimed to report the clinical picture and treatment of a bilateral rupture of the peroneus tertius muscle in a cow from the municipality of Castanhal, state of Pará (Amazonian biome).

Case: We report the clinical picture and treatment of a bilateral rupture of the peroneus tertius muscle in a 4-year-old cow, mixed breed, weighing approximately 400 kg, calved 3 months ago, belonging to a batch of 40 cattle kept on extensive breeding system in a pasture of Urochloa (Brachiaria) brizantha. The clinical signs appeared after the cow was mounted by a 1,100 kg bull and consisted of lameness, falling into sternal decubitus with hind limbs extended backward, hyperextension of the hocks with flexed stifle, with the tibia and metatarsus in a straight line, which lead to a 90-degree position of the femur and knee. Abrasions in the dorsal region of the fetlocks reinforce evidence of dragging hooves. Diagnosis of bilateral rupture of the peroneus tertius muscle was performed by a clinical examination and semiological test. Non-steroidal anti-inflammatory drugs (flunixin meglumine, 2,2 mg/kg, every 24 h for 4 days) were prescribed for treatment, in addition to resting in a paddock with good availability of pasture, water, and mineral salt. After 3 months, we observed an improvement of the clinical signs, and after 6 months, an almost complete recovery. Only a slight difficulty in flexing the hock when moving remained.

Discussion: In the present report, bull mounting was the probable cause of the hyperextension of both hocks and the bilateral rupture of the peroneus tertius muscle. According to the handler, these clinical signs were only evidenced after the animal was mounted. As stated in the literature, accidents such as falls, slips, mounting or being mounted, as well as excessive traction and over-elevation of the limb are considered predisposing factors for the onset of the disease. Rupture of the peroneus tertius muscle is unusual in production animals; therefore, the low occurrence of reports on this kind of rupture in the literature makes this case even more unique. The bilateral injury differs from cases described in the literature, in which the reported injuries were always unilateral. Our findings reinforce the hypothesis that the act of mounting was the triggering factor for the bilateral rupture of the animal peroneus tertius muscle. The breeding system also differs from the cases diagnosed by the same authors, since they describe the disease in bovines kept on intensive or semi-intensive breeding. In the present case, the cattle were kept on an extensive breeding system. The extension and flexion tests used in the clinical examination allowed for the diagnosis of rupture of the peroneus tertius muscle in both limbs, similarly to what has been reported by other authors. Anamnesis, clinical findings, and exclusion of different diagnoses were decisive for establishing the diagnosis. The treatment chosen was efficient, even though the case was severe, as the injury occurred in both hind limbs.

Keywords: cattle disease, muscle injury, lameness, rupture.

Título: Ruptura bilateral do músculo fibular terceiro em bovino

Descritores: doença do gado, lesão muscular, claudicação, ruptura.