Long Bone Fracture Repair
Conventional Bone Plating
When using conventional bone plates to heal a long bone fracture in the horse, the fracture is stabilized as outlined below. When you tighten a bone screw (force =F1), it compresses the bone plate against the bone (force = F2) creating friction (force = F3) between the bone plate and the bone. Recognizing that the horse bears weight immediately after surgery, in order for the fracture to heal, the force of friction (F3) between the bone plate and the bone must be greater than the force of weight bearing (force = F4) or the fracture repair will become unstable and fail.
Locking Compression Plating
Locking compression plating (LCP) is a fundamental change in the way the forces are managed to stablilze the fracture. With the LCP system, the threaded head of the LCP screw (Figure 1) “locks” into the threaded hole of the LCP plate (Figure 2) at a 90 degree angle to the bone plate (see radiographs below). By locking the head of the bone screw to the bone plate, the fractured bone is stabilized by the bone plate over the entire length of the bone. This provides significant stability to the fractured bone even if the friction between the bone plate and bone is poor.
Another major mechanical advantage of the LCP system is the internal diameter of the bone screw. The internal diameter of the largest LCP screws is 4.3 mm but the internal diameter of the largest conventional bone screw is 4.0 mm. The larger core diameter of the LCP screw makes the mechanical properties of this system superior in bending to the conventional bone screw.
The combination hole in the LCP plate (Figure 2 & 3) allows the placement of a LCP (threaded head) screw on one side of the hole (black arrow) or the placement of a conventional (non-threaded head) bone screw on the opposite side of the hole (red arrow).
Figure 1: Note the threads on the head of the LCP screw verses the smooth shoulder on the head of the conventional screw.
Figure 2: Note the combination hole in the LCP bone plate. The black arrow identifies the presence of threads in the left side of the hole for placement of an LCP screw. The red arrow identifies the absence of threads in the right side of the hole providing the option to place a conventional bone screw.
Figure 3: Note the LCP screw to the left of the hole in the upper bone plate and the conventional screw to the right of the hole in the lower bone plate.
Examples of Cases Treated with the LCP System
Pastern Joint Fusion
FETLOCK JOINT FUSION
CARPAL JOINT FUSION
CANNON BONE FRACTURE: Adult
CANNON BONE FRACTURE: Foal
OLECRANON (ULNAR) FRACTURE- Yearling
ANDERSON SLING FOR THE RECOVERY OF LONG BONE FRACTURE REPAIR
The Anderson sling recovery system was originally developed as an air rescue device (www.andersonslong.com). In a hospital setting, it is used to help horses recover from general anesthesia to facilitate a smooth recovery, and for down horses for rehabilitation and long term care.
For horses that are recovering from a recent long bone fracture repair, it is an effective and safe way to smoothly transition horses from a prolonged recumbent to a standing position. Recognizing that the surgical repair is not as stable as a normal limb, it improves the prognosis for long bone fracture repair if the explosive nature of equine recovery from general anesthesia can be avoided.
In the photographs below, the horse had a long bone fracture repair of the left front cannon bone and has been assisted to the standing position using the Anderson sling but has yet to recovery from general anesthesia.
Figure 1: The red arrow identifies the endotracheal tube that remains in place following general anesthesia. The endotracheal tube will remain until the horse can successfully swallow and maintain a patent airway without assistance.