Fracture Repair in Cats
Dr. Nicholas Trout
The type of fracture, its location, the age of the animal, the presence of other injuries/fractures and the financial means of the owner are all major considerations in the choice of fracture repair undertaken. For any given fracture there are often many different treatment options. The Robert Jones bandage is the most common form of temporary fixation of a fractured limb prior to definitive stabilization.
Some types of repair may require special equipment and experience and your veterinarian may recommend referral to a board certified surgeon.
Because there are many ways to fix the same fracture. Each option will be discussed and considered for its advantages and disadvantages in the context of your cat and his or her particular injury/injuries.
Casts and splints are usually the easiest and least expensive ways to provide stabilization of a fracture below the elbow and below the stifle. Plaster of Paris used to be used for casting but it has been replaced by fiberglass materials that can easily and quickly be molded and conformed to the shape of the leg and then set to provide rigid external fixation. Plastic, fiberglass, and metal splints in a variety of shapes and sizes, can be used to provide support to a portion of the limb, usually the back or the sides, as opposed to a cast that encompasses the entire circumference of the affected portion of the limb.
The rigidity of the cast prevents bending of the limb, but the joint above and below the fracture must be stabilized to prevent rotation of the fracture fragments. This limits the use of casts and splints to the lower extremities.
Casts and splints may not be appropriate for open fractures, in which the bone has pierced the skin or where there is a lot of soft tissue trauma associated with the broken bone. Casts prevent management and monitoring of the injured area.
External fixation can provide stable fracture fixation at less cost than plates and screws. It can be particularly useful for the management of open fractures or fractures where wounds need to be managed while the fracture is stabilized.
External fixators in many cases can offer the surgeon the ability to stabilize a fracture, without interfering with the natural healing process already under way. Closed reduction involves manual repositioning of the broken bones, placement of pins through the skin and into these bones and then rigid fixation of the pins to metal bars, graphite bars, circular rings, or cement polymers.
External fixators can be simple or complex creating uniplanar, biplanar, and circular support frames around the fracture. The fixators may appear cumbersome and uncomfortable but cats tolerate them extremely well.
The connection of the pins through the bone to the outer construct may involve clamps that will be checked periodically for tightness.
External fixators may not be suitable for certain fractures where they may interfere with muscles and impede movement of a limb. Generally they are considered less appropriate for fractures of the femur and the humerus.
Internal fixation, by definition, necessitates internal reduction of the fracture, by incising the skin and dissecting through soft tissue planes to get the fragments exposed and back into alignment.
Internal fixation is often appropriate for more complicated fractures such as those that involve a joint surface, or those that have shattered the normal contour of the bone, as in a comminuted fracture.
Stainless steel pins and wire are the simplest implants for internal fixation. Wires (referred to as cerclage wires), can be placed around the circumference of a bone to squeeze together fracture fragments in order to reconstruct the cylinder of bone that used to exist. They can also be used in combination with small pins to skewer bone back into place, particularly where the fractured bone may be pulled away or distracted by a muscular attachment, a so-called tension band wire technique.
Larger pins can be placed down the central canal of a long bone, an intramedullary pin, to enable the fracture fragments to be brought back together.
The pin can provide good resistance against bending of the healing bone but poor resistance to rotation around its long axis. Cerclage wires may help resist this rotational instability but certain fractures may benefit from adjunctive external fixation or the use of plates and screws instead of pins and wires.
Plates and screws offer the most rigid form of fracture fixation and, therefore, early return to limb function. There are numerous different sizes and shapes of plates and screws for different sized animals and fracture configurations. Plates and screws tend to be the most expensive form of internal fixation.
When fractures involve a joint surface, screws can be used to put the bone fragments into apposition and to actually compress them together, thereby minimizing any gap or step at the fracture site. This will restore the fractured bone as close to normal as possible, allowing optimum function of the joint and minimizing the chances for arthritis.
Metal plates can be used to span the bone across a fracture site. The plate can be used to hold the fragments in place or to actually squeeze and compress the ends of the bone together to enhance and speed up the healing process. Many of the plates are designed in such a way that when a screw is placed through its appropriate hole in the plate and screwed into the bone, it will compress the ends of the fracture fragments together – a dynamic compression plate. Ideally, a surgeon will attempt to get at least three screws above and below the fracture site.
Plates and screws can be used in conjunction with pins and wires and external fixators, depending on the configuration of the fracture that is being repaired.
Interlocking intramedullary pins are popular in human orthopedics, and are becoming more common in veterinary surgery. This technique combines placement of a pin down the medullary (central) cavity of a bone and screwing this pin into the bone at several locations along its length. It is mainly used for the treatment of humeral and femur fractures.
Spinal fractures and combinations of fracture and dislocation, where spinal cord is damaged, are the only fractures that constitute a surgical emergency. Fixation of these fractures can be achieved using any of the techniques previously described, including the use of pins fixed in position using a sterile cement compound.