CRANIOFACIAL SURGERY
Dental surgery is discussed in Chapter 13.
3.1 Commissurotomy
Access to the oral cavity in macropods, koalas and wombats is restricted by their long, narrow oral cavities and narrow gape (see Chapter 13).
Although mechanical methods, such as mouth gags, can be used to improve access, surgical exposure may be necessary in some cases.Commissurotomy has been used successfully in an adult wombat and a koala to facilitate access to caudal molars. In the wombat, bilateral mandibular nerve blocks were used (1.25 mg bupivacaine each). With the mouth open, a full-thickness incision was made on both sides of the mouth, extending from the commissure to the third cheek tooth, avoiding the salivary duct papillae and ligating small vessels. Once dental work was completed, the soft tissue was closed in three layers (mucosa, muscle and skin) (Wilson and Gillett 2010).
3.2 Hemimandibulectomy
Hemimandibulectomy was undertaken in a red-necked wallaby with severe refractory osteomyelitis. Surgery was initially successful; however, the surgical site became infected 28 d later and the animal was euthanased (Sued- meyer et al. 1999). Another red-necked wallaby with a necrotic mandibular sequestrum and pathological fracture had a hemimandibulectomy near the caudal molar tooth
and survived for 8 mo (Hulst et al. 2015). Careful consideration must be given to welfare implications and longterm prognosis before performing hemimandibulectomy.
3.3 Mandibular fracture
In koalas, surgical repair of mandibular fractures is performed through a ventral incision from symphysis to ramus, avoiding the mental nerve. Mandibular fractures require good alignment for healing, which is best achieved by application of a bone plate. If the fracture communicates with the oral cavity, prognosis is poor because of infection risk. For mandibular symphysis fractures, cerclage wires are placed around the incisors (not through the skin), together with dental cement in the symphysis fracture site (A Gillett pers. comm.).
A mandibular fracture has been successfully repaired in a harbour seal (Phoca vitulina) with an intraoral dental splint and multiple circumferential cerclage wires on the mandible to stabilise the fracture (Lewer et al. 2007). This technique could be applied to Australian pinnipeds.
3.4 Ear canal ablation and bulla osteotomy
Total ear canal ablation and bulla osteotomy has been performed in koalas. Access to the bulla is via a caudolater- oventral approach to avoid the ramus of the mandible. Once within the bulla, the thin bone separating the two middle ear chambers is punctured to allow effective curettage and flushing (Swaffield et al. 2023). Tympanic bulla osteotomy surgery and external ear canal ablation was performed in a koala with otitis media (Hulst et al. 2015). The technique for ear canal ablation is the same as in the dog, the koala having a shorter canal (Swaffield et al. 2023).
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