Parallel pins may be inappropriate in some situations as discussed below.įractures of the humeral head are usually Salter-Harris type I and II. Mechanically, the forces applied to parallel pins are distributed equally between the pins, while with divergent pins, uneven distribution of loads between the implants renders the technique weaker and predisposes the repair to failure.
Parallel pins allow for continued physeal growth, while divergent pins may create a locking effect on the physis, resulting in premature closure. Pins placed parallel to each other offer biological and mechanical advantages in comparison to divergent pins. The most commonly used implants for physeal fractures are pins. They should not be in place longer than 4 weeks. In the rare case in which the fracture configuration requires bridging of the physis with of one of these implants, early removal as soon as two weeks after surgery should be considered depending on the degree of healing. Implants that prevent further physeal growth, such as bone plates, lag screws, and external skeletal fixators, should be avoided in the growing animal. It is often presumed that regardless of the implant the physis may close as a result of the inciting or surgical trauma.įixation techniques for physeal fractures should minimally impact blood supply, result in accurate and stable reduction, be easily removable, and not significantly further damage the physis. Physeal fractures occur in immature animals with open physes, usually secondary to trauma, though this may be minimal depending on the affected location. Included will be common fractures and their surgical fixation, the evidence on healing times, and when and if to remove implants. This lecture will focus on the immature dog and fractures specific to them. Books & VINcyclopedia of Diseases (Formerly Associate).VINcyclopedia of Diseases (Formerly Associate).
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