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Bone Fractures
ОглавлениеFractures in the bovine often occur due to inappropriate management, such as mishandling, crowding, or improper handling facilities. The duty of the practitioner is to evaluate the fracture and determine whether economical repair or salvage is most appropriate. Fractures of the rear limbs often occur due to trauma from other cattle; the tibia is the most commonly affected of the long bones when this occurs.
Physical examination and palpation with manual manipulation of the limb can be helpful to assess the extent of the injury. Radiographs are necessary to determine if the fracture is comminuted or involves a joint that may not be readily apparent on physical examination. Attention should also be given to soft tissue injuries that may have damaged the vascular supply. Damage to the dermis may result in sloughing tissue and exposure of the fracture. Crushing injuries of the digital vasculature and metacarpus can happen after forced fetal extraction during dystocia. Consideration should be given to sepsis at the fracture site, particularly in older fractures, as hematogenous spread of bacteria in the bovine can occur.
Cattle with fractures of the distal limb, forelimb, or hindlimb heal extremely well. Even comminuted and compound fractures can resolve if proper immobilization and therapy are provided. The most common method of repair in simple fractures is passive fixation with a cast. A half‐limb cast is used for fractures below the carpus or tarsus.
Comminuted or compound fractures of the digits usually require a more rigid immobilization in order to get adequate healing in a reasonable amount of time. Of great value in complete immobilization is the traction/pin cast, which involves incorporation of wires passing through holes drilled in the rear abaxial walls of the hoof. This also serves to allow the assistant to properly position/align the limb for casting. Transfixation or transcortical pins are usually placed at some point in the lower to mid‐third of metacarpal (MCIIII) or metatarsal III (MTIII) to provide for weight transfer to the cast. Predrilling of a slightly smaller hole (0.5 m or less than the pin diameter) will reduce thermal injury to the bone during pin placement. Oftentimes, only one pin is needed to properly provide for weight transfer in younger animals. Threaded transcortical pin systems are preferred in older, heavier cattle, usually requiring placement of two pins at least 1.5 inches apart from each other. During casting, the pins are incorporated into the cast, with the pin ends cut even with the cast and protected by an acrylic compound placed over them, as well as acrylic applied to the bottom of the cast to protect it. The wires placed in the hoof wall are incorporated into the wall of the cast under tension before completion of the procedure. Most of these casts can be removed at four to six weeks post casting.