Fractures of the interdental space and horizontal ramus are almost always open. Wound debridement and flushing is extremely important. Nevertheless, infections of soft tissues as well as the bone are common. Therefore, ventral drainage is important.
Additional fixation techniques
In some cases, the fracture can not be stabilized with the wires alone. Therefore, additional fixation techniques become necessary, such as plates, U-bars and others.
In the horse 1.2 m (18 gauge) orthopedic stainless steel wire is most commonly used for cerclage. For rostral fractures that result in loosening of the incisors, an interdental continuous wire-loop splint described by Obwegeser (1952) can be used. It allows the application of uniform tension between all the teeth that are engaged in the splint. One end of the wire is guided back and forth between all incisors to form small loops in front of the incisor teeth starting on one side of the arcade. The other end of the wire is then threaded through the loops, followed by tightening of the wire ends. The wire should always be tight and care must be taken that it is not weakened by repeated bending or kinks during insertion.
Pearl: For insertion of the wire, a sharp end can be created by cutting the wire at an angle. This facilitates penetration of the gingiva. Alternatively a 2 mm (14 gauge) hypodermic needle can be used to penetrate the tissue between two adjacent teeth and to allow passage of the wire, or small holes (2.0 or 2.5mm diameter) may be prepared using a Steinman pin or a small drill bit. This is usually required for passing a wire between the incisors and almost always for placing the wire between cheek teeth.
Tightening the loops
After tightening the two wire ends, each wire loop previously created in front of the incisor teeth is tightened in a uniform fashion using pliers or needle drivers. This must be completed in an even fashion, alternating between multiple loops, and under careful monitoring of the fracture site to avoid displacement after reduction.
After the wires are tightened, the twisted ends are shortened and bent flat so that they do not irritate or injure the gingiva. If they are sharp, they should be protected.
Anchoring of the wire
The wires are anchored around the cheek teeth. Depending on the extension of the fracture line, the wire passes between the corresponding cheek teeth to engage the entire fracture line.
To achieve this, the skin is clipped, surgically prepared and a short arthroscopy sleeve with a trocar or obturator is advanced into the mouth via a stab incision. This technique minimizes hemorrhage, which can be a problem when the tissue is cut with a scalpel. A drill bit is then introduced through a protective drill guide and a hole is prepared between the two cheek teeth.
Twisting the wire
Once the wire loops are tightened, additional tension and stability can be achieved by twisting the two parallel wires in the interdental space around each other.
4. Reduction and Fixation
There are many other ways to place the wire loops for optimal accommodation of the fracture. Simple loops must overlap to ensure that teeth are not pulled apart, and figure-8 loops (left) can be used to increase stability.
In selected cases, where stability and compression cannot be achieved with intraoral wiring alone, additional cerclage wire loops is placed around the mandibular bone. A skin incision is made over the ventral surface of the mandibula and the wire is passed on the abaxial side of the bone to the dorsal aspect and then guided back on the axial side of the bone. The ends are tightened.
At the end of the surgery, the teeth of the upper jaw are shortened to reduce pressure during eating.
During the post-surgical period, the horse is confined to stall rest for one week and fed with soft fiber feed stuff; firm feed such as hay cubes, apples or carrots should not be fed. Antibiotics and anti-inflammatory drugs are given for 3 to 5 days or longer, if required, especially in open fractures. Intraoral cerclage and tension wires are cleaned once daily until their removal. Wound opening is cleaned and flushed daily with antiseptic solutions. After 8-12 weeks the wire can be removed under sedation and local anesthesia.