anatomy
blood supply of small breeds
unless fractured ends are stable and not displaced a lot, a POP or padded plastic splint can be used. otherwise plating ensures perfect alignment
1. CLOSED REDUCTION AND EXTERNAL FIXATION
The closed reduction of closed fractures and immobilization in casts or splints is very useful in treating fractures of the radius and ulna. Most fractures are done this way. Form-fitting splint is important to provide stability. Anaesthesia is important to prevent pain during manipulation. In small breed, non-union is common as blood supply is poor. Leg is clipped. Aseptic technique practised in case closed fracture becomes open fracture during manipulation.
The best fixation can be achieved with casting materials that are molded to the particular animal. The use of ready-made splints may work in certain animals, but the incidence of delayed union or nonunion can be greatly reduced by a properly fitting splint or cast. The type of cast usually used for front legs is a
total encircling plaster cast or a double half cast of
plaster.
2. OPEN REDUCTION AND EXTERNAL FIXATION
Occasionally closed reduction of closed fractures is not possible because of delay in attempting the reduction or because of interposed soft tissue. Sometimes open reduction of closed fractures may be performed without internal fixation, especially in fractures that are
relatively transverse. See X-ray of the distal 1/3 radial and ulnar fracture of left foot in this case
The animal is positioned with his injured leg down, and the foot is elevated and held by a stirrup to an IV stand or ring. The leg is completely clipped and surgically prepared. The foot is draped, as is the rest of the body, and aseptic technique is used while making a small incision over the fracture site. The fracture fragments are levered back into position with a small bone elevator.
Following perfect anatomical reduction of the fracture, the skin wound in closed and an
encircling or double half cast (if there is tissue swelling) is applied to the fracture.
Healing in these animals occurs satisfactorily as it would in an animal with a good reduction of a closed fracture by closed means (plate and screws). The technique is simple and often the time involved is less than that required for closed manipulation.
The total encircling cast is best for the large breed dogs because it is the strongest cast that can be applied. The dog's fracture should have a good reduction, and the foot position should be such that the carpus is in slight flexion and slight medial deviation with no external rotation. When applying the cast it is important that the animal's injured leg be in the down position, thereby preventing placement of the leg in a valgus position at the time of casting and, thus, during the time of healing. The double half cast, although not as strong as the total encircling cast, can be used when swelling is present or the soft tissues are such that frequent examination may be necessary. This cast is already split in half and can have one section removed to examine the leg while maintaining stability of the fracture reduction. As the swelling subsides the cast may be adjusted so that it is firmly in place to control fracture movement.
3. OPEN REDUCTION AND INTERNAL FIXATION
Open reduction and internal fixation of closed fractures is usually performed when the leg is inherently unstable, as with comminuted fractures or long oblique fractures, or when closed reduction is not possible or a simple open reduction is unstable
The internal fixation device that seems to have the highest degree of success, especially in small breed dogs, is the plate and screws. The plate is applied to the cranial surface of the radius, and no attempt is made to stabilize the ulna. If the radius heals and the ulna is in contact, the ulna will heal. Occasionally in small breed dogs atrophy of the ulna may occur, and the distal ulna may disappear entirely. This does not seem to adversely affect function or fracture healing of the radius. Most complications of radial and ulnar fractures appear to occur when intramedullary pins are used, especially in small breed dogs. These pins seem to interact in an area of poor vascularity in such a way that the stability achieved is not complete and a fibrous nonunion will ensue. The literature does report success using these techniques, but based on personal experience we do not recommend the use of radial intramedullary pins for fractures of the distal radius and ulna in small breed dogs.
Occasionally in large breed dogs an intramedullary pin is used in the ulna to reduce fractures of the distal radius and ulna, which are then stabilized through the use of a cast or splint In this way the radius will be given a chance to heal and the ulnar pin may be removed at a later date following fracture healing of the radius. The use of an ulnar pin and a radial plate is very successful in large dogs.
4. Radial intramedullary pins have been used with good results in giant breed dogs, but the problem with this technique is related to the position of the end of the pin. Any pin that is large enough to control motion within the cortices must exit through a joint. The exit of the pin will, in fact, help destroy the antebrachial joint and will usually leave the joint somewhat compromised even following pin removal. Therefore, intramedullary pinning of the radius is
not performed in our clinic. Small cross pins, combinations of cross pins, and figure-of-eight wires have been used successfully in fractures of the radius and ulna.
Also use of intramedullary pins that are inserted at the fracture site and toggled into position by a technique similar to that of the Leighton shuttle pin has been reported in the veterinary literatures The disadvantage of this technique is difficulty in removing an intramedullary pin that has not exited the medullary cavity if such removal should become necessary.
Occasionally small breed dogs in whom plates and screws have been inserted will experience some discomfort, especially in cold weather, even after the fracture has healed. This appears to be related to heat transfer associated with the environment and the "massive" metal device. Removal of this device will usually eliminate the problem.
It must be remembered that bony remodeling occurs when an implant is removed, and the bone will not regain its strength for some time after removal. While the implant is in place, the bone adjacent to the fracture site will never regain its normal strength, and the return of strength following implant removal is related to bone remodeling. In the dog the bone will probably require 8 weeks to remodel properly such that full weight-bearing effort can be exerted on it without refractured
Most radial and ulnar plates in our clinic are not removed. It is not uncommon to have a fracture occur if adequate immobilization is not accomplished after plate removal.
External skeletal fixation is a popular method of treating fractures of the radius and ulna.(9) The technique lends itself to such fractures because of the ease of bone palpation and pin insertion. External skeletal fixation works best when little or no muscle is traversed by the pins as can occur in radial and ulnar fractures.
REFERENCE
http://cal.vet.upenn.edu/projects/saortho/chapter_24/24mast.htm
