Typically, plates must be placed in a less than ideal location, in terms of biomechanics.
Fig. F4L: Intraoral splinting with dental acrylic (cold curing type) formed around a tension band wire between the incisors and first cheek tooth. Several additional wires are used to unite the splint with the mandible.
Fig. X4H: A rostral mandible fracture was repaired with special plate (PC-Fix) and short screws. The repair was supported with a tension band wire between the incisor and premolar teeth.
Only one report exists of plates being applied to the teeth [12]. With a specially hardened drill bit holes are prepared in the teeth, and short screws are employed to attach the plate. About four to five screws are necessary (Fig. F4O).
Fig. F4M: A 6-hole 4.5 mm narrow DCP is applied to the horizontal ramus of the mandible. The screws are inserted between the tooth roots.
Fig. F4N: Surgical approach for plate application to the vertical ramus of the mandible via a subperiosteal elevation of the masseter muscle.
Fig. F4O: A narrow DCP is applied to the incisor and premolar teeth with short screws. The location of the plate effectively counteracts the developing forces.
Avoid insertion of a screw through a root canal whenever possible. The benefit of this technique is that the plate is applied in a more rostral position of the mandible and closer to the tension side of the bone. After the fracture has healed, remove the screws and fill the holes in the teeth with dental acrylic.
4.1.5.2 Extraoral fixation techniques
Among these techniques external fixators are distinguished from the pinless external fixator.
External fixator
Use a type II external fixator for mandibular fractures.
An external fixator type I consists of one longitudinal bar and four to five Schanz screws or intramedullary screws, being inserted into one ramus of the mandible or maxilla [2, 4] (Fig. S4G). A type II configuration consists of Steinmann pins through and through, involving both rami of the mandible or maxilla and bilateral longitudinal fixation bars. In external fixators mainly Steinmann pins and occasionally Schanz screws are inserted on either side of the fracture and connected to clamps and tubes, cerclage wires, and dental acrylic [2, 4]. Plastic tubes filled with acrylic represent another option (Fig. F4P). With the external fixator, interfragmentary compression of the fracture can be achieved. The integrity of the tooth roots should be preserved. Place the Steinmann pins in such a way as to prevent excessive trauma to the tongue. In the rostral aspect of the mandible, use Steinmann pins with positive threads [2]. Prevent untimely removal of the fixation device by the animal by housing it in a hazard-free environment. If applied properly, good stability may be achieved across the fracture site. It may be necessary to use an alternative feeding technique, such as liquid diet or nasogastric tube feeding. Esophagostomy is also an option, but it is associated with a high complication rate.
Fig. F4P: Type II external fixator across both rami of the mandible. A tension band wire is applied around the pins and tightened to achieve interfragmentary compression of the fracture. The previously open soft tubes are closed with parm bands and the lumen filled with epoxy material, such as PMMA, hoof acrylic, etc.
Fig. S4G: A type I external fixator is applied to a mandible fracture in a 2-year-old Quarter Horse stallion.
Pinless external fixator
The pinless external fixator presents an alternative technique [13]. Several sizes of titanium clamps are currently available. An asymmetric clamp (Fig. S4H) complements the large and small symmetric clamps. The symmetric clamps are applied across the rostral mandible in the region of the diastema, while the asymmetric clamps are applied to a ramus on both sides of the fracture. A minimum of four clamps should be applied and connected to the longitudinal rod (Fig. F4Q). Application involves only minimal trauma, since only small incisions are needed and no transosseous pins are inserted. The clamping force of the fixators persists over a long period, making the devices an attractive alternative. The device can be reused several times. Results so far are excellent, especially in bovine patients [13]. The fact that these animals ruminate should be taken into account. The associated masticatory action causes frequent and powerful cyclic loading. This fixation device must also be protected against inadvertent removal. Good stability can be achieved, leading to good healing. Sequestra may form and require subsequent removal.
Use at least four clamps—two on either side of the fracture.
Fig. S4H: Configuration of the three clamp types of the pinless external fixator. The large and small symmetric clamps are complemented by the asymmetric small clamp. The latter fits ideally around the ramus with the straight arm placed medial of the ramus.
Fig. F4Q: Pinless external fixator applied to a mandible fracture. a) Asymmetric clamp attached to the ramus; b) small adjustable connecting bar; c) single external fixator clamp; d) tubular connecting rod that fits into the clamp (c).
4.1.6 Postoperative management
Monitor the animal and the fixation at least daily during the first 3 postoperative weeks. Delegate the care to the owners as soon as possible, but make them aware of the “danger signs”. Clean the mouth daily with water from a hose and take follow-up radiographs at 6 and 12 weeks. Depending on the fixation technique, it may be advisable to maintain the animal in a box stall until the implants can be removed.
4.1.7 Complications
Infection is the major complication encountered. This becomes especially problematic if instability is present. This instability is occasioned by use, or by trauma to the device. Bone sequestra are not infrequent because these are open fractures. Some teeth may have to be removed in a second operation. Breakdown of the fixation may be an additional complication.
Infection is especially problematic in the presence of instability.
4.1.8 Prognosis
The prognosis is, in most cases, favorable