Page 632 - WSAVA2018
P. 632

 25-28 September, 2018 | Singapore
P. Maguire1
Prior to any oral surgery or reconstruction familiarization with local nerve blocks is essential. Unlike some other areas of the body, good options exist for local analgesia. Local anaesthetics include:
· 0.5% bupivicine (up to 2mg/kg, onset within 30 minutes - effective for 6-10 hours)
· lidocaine 2% (up to 5mg/kg in dogs and 1mg/ kg in cats, onset within 5 minutes - effective for <2hrs)
The Infraorbital nerve bock is applied at the infraorbital foramen or inside of the infraorbital canal and will block tissues rostral to the infraorbital foramen. The inferior alveolar nerve block is Injected around the mandibular foramen situated on the ventromedial aspect of the mandibular ramus. The area blocked includes the mandibular body, mandibular dentition and adjacent soft tissues. The middle mental nerve block is applied at the middle mental foramen ventral to the mesial root of the second premolar in the dog or halfway between the canine and third premolar in the cat. This will block the rostral mandibular body, the dentition, and adjacent soft tissues. The major palatine nerve block is applied to the palatal mucosa just rostral to the major palatine foramen and will block the palatine shelf of the maxilla. The maxillary nerve block is given just caudal to the last molar tooth as the maxillary nerve enters the maxillary foramen. This will bock the incisive bone, maxilla and palatine bone as well as maxillary dentition.
Lip reconstruction
Many smaller upper lip excisions can be performed in
an inverted “V” shape and reconstructed directly. The upper lip in most dogs has significant mobility to allow both cosmetic and function reconstruction in this manner. Two to three-layer closure can be used depending on patient size. In cases where larger quantities of tissue require excision a direct uni- pedicle advancement flap may still facilitate closure. For more extensive defects or significant defects of the lower lip an angularis oris axial pattern flap or caudal cervical flap may be used to bring additional tissue into the reconstruction.
Soft tissue reconstruction following mandibulectomy
In most cases mandibulectomy is being performed to remove an oral malignancy. Gingival margins can be assessed visually however infiltration into adjacent bone and soft tissues is best conduted on CT. Margins of at least 1cm (more when feasible) should be achieved when performing excisions. Caudal mandibulectomies can
usually be closed by direct intraoral mucosal apposition.
In these instances, there is often no need to excise skin, allowing relatively straight forward if slightly awkward closure. Four tissue surfaces must be considered when excising central or cranial portions of the mandible; the oral sublingual mucosal, gingival, labial mucosa and skin. Excision should be performed to remove the desired bone and soft tissue margins. Additional bone often needs to be resected as transaction should be performed between dentition and still leave enough soft tissue to cover the bone ends (ie the bone excision must extend beyond
the soft tissue excision). Edges of bone that are excised should be rounded off or filled where possible to avoid focal pressure on the overlying mucosa. Priority should be given to complete neoplastic excision and it is not uncommon that the cutaneous tissues of the skin must be sutured directly to the sublingual mucosa.
Although osseous reconstruction has been described with the use of BMP impregnated scaffolds, most
large excisions will be performed without structural replacement. As such mandibular drift should be expected or managed at the time of the original surgery with elastic trainers. Subsequent application of elastic trainers following drift is less likely to be successful.
When preforming a maxillectomy the palatine and infraorbital arteries may need to be transected and ligated. A combination approach, both intraoral and through a lateral skin incision can be used to perform these procedures. Closure is typically accomplished by direct apposition of the labial mucosa to the palatine mucosa. A single pedicle advancement flap can be generated from the labial mucosa to allow improved closure. It is not uncommon to need to drill holes in the palate to allow placement of the sutures as the palatine mucosa can be friable. In situations were the palatine resection passes midline, complete closure with a labial flap can be difficult. A superficial cervical axial pattern flap or angluaris oris flap can be used.
Palatine Defects
Many patients with congenital palatine defects are euthanized at birth by the breeder. Those that are candidates for reconstruction need to reach at least 3-7 months of age before surgery. Premature correction can result in tearing of tissues or damage to the periosteum which can hamper further development. Waiting until adult dentition has erupted will also allow extraction, freeing more soft tissues to allow closure. Waiting too long can result in larger defects and often the pet will require a tube feeding until definitive repair which can place a burden on the owner.
The defects are a result of incomplete fusion of the maxillofacial structures;
· Cleft lip, rostral hard palate
· Midline of hard and soft palate

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