Mandibulectomy and maxillectomy Flashcards
According to Goldschmidt 2020 in Vet Surg, what biometric skull measurements were associated with increased tension and decreased nasal aperture following nasal planectomy reconstruction?
Wider facial features and thicker lips, as well as philtrum design and placement
Specifically: width of the nasal planum (>3 cm), width of the caudal maxilla
(>6.2 cm), lip thickness (>0.5 cm), width of the labial flap (>2.9 cm), length of the incision created to make the cosmetic “philtrum” (longer incisions >2.8 cm), and philtrum placement (more dorsal placement).
In a study by Sharma 2021 in Vet Surg, what was the prognosis for juvenile dogs undergoing mandibulectomy or maxillectomy for oral squamous cell carcinoma?
Excellent - these patients can be treated effectively with surgery alone. All dogs were alive at follow up (median follow-up 1556 days).
In a study by Carroll 2020 in JAVMA, what size of oral melanoma was able to accurately predict the presence of lymphatic invasion on histologic grading?
> 24.5mm (100 specificity). Less than 6.5mm able to rule out lymphatic invasion (100 sensitivity).
In a study by Cray 2021 in JAVMA, what was the overall complication rate for dogs undergoing maxillectomy or mandibulectomy? What factors were associated with an increased risk of dehiscence or oral fistula formation?
The overall complication rate was 37% (longer surgical time was associated with an increased risk for complications).
Maxillectomies and preoperative chemotherapy or radiation had an increased risk for dehiscence or oral fistula formation.
Do peripheral odontogenic fibromas invade the bone?
No, can appear macroscopically invasive but there is no underlying bone involvement.
In a study by Lee 2021 in VRU, what were 5 features of oral tumour malignancy based on CT?
Large size, heterogenous contrast uptake, bone lysis, tooth loss, ipsilateral lymphadenopathy. However, benign tumours could also cause these changes (particularly acanthomatous ameloblastoma and therefore biopsy is still required to definitively differentiate).
In a study by Menghini 2023 in VRU, CT 3D volumetric analysis was used to identify nodal metastasis in cases of canine oral melanoma, what was the positive predictive value of mandibular lymphocenter volume?
57%
In a study by Shilo-Benjamini 2022 in JFMS, which of the maxillary block techniques shown was associated with best spread of infusate and potential maxillary anesthesia?
The infraorbital canal and maxillary foramen techniques both resulted in adequate distribution of infusate.
These techniques were suggested over traditional maxillary block techniques to avoid penetration of the globe.
In a study by Zaccone 2022 in JVIM, what were 4 risk factors identified for development of oral squamous cell carcinoma in cats?
Rural environment, outdoor access, environmental tobacco smoke, and petfood containing chemical additives.
What is the MST for canine oral melanoma based on stage?
Stage 1: 424 to 874 days (tumor < 2 cm, negative lymph nodes)
Stage 2: 246 to 818 days (tumor 2 to 4 cm, negative lymph nodes)
Stage 3: 173 to 495 days (tumor >4 cm or positive lymph nodes).
What are the major muscles of mastication?
Digastricus, masseter, pterygoideus, temporalis.
What is the major arterial supply to the mandible?
Inferior alveolar artery, a branch of the maxillary artery.
What is the major nervous innervation to the mandible?
The mandibular nerve, a branch of the trigeminal nerve. After entering the mandibular canal it becomes the inferior alveolar nerve, becoming the mental nerves as it exists the mental foramina rostrally.
What is the major arterial supply to the maxilla?
Major palatine artery and infraorbital, both branches of the maxillary artery. The infraorbital artery exits the mandible laterally through the infraorbital foramen at the level of the carnassial tooth.
What is the major nervous innervation to the maxilla?
The maxillary nerve becomes the infraorbital nerve that enters the infraorbital canal.
What are the most common oral tumours of dogs, in descending frequency?
What is the metastatic rate (either regional or distant) for these tumours?
Malignant melanoma (metastatic rate 81%), SCC (20%), fibrosarcoma (35%), osteosarcoma, acanthomatous ameloblastoma.
Is survival time of oral osteosarcoma typically better or worse than for appendicular osteosarcoma?
Better
What is the normal signalment for common oral tumours of the dog?
Melanoma: older, small breed dogs.
SCC: older, large breed dogs.
Fibrosarcoma: middle to older large breed dogs, particularly Golden retrievers and labradors.
Osteosarcoma: medium and large breed dogs.
What is the most common location for oral fibrosarcoma in the dog?
Gingiva near the maxillary carnassial tooth.
Where do acanthomatous ameloblastomas typically occur?
Rostral portion of the mouth. Locally aggressive and should be treated by maxillectomy/mandibulectomy.
What are peripheral odontogenic fibromas (POF)?
Previously called fibromatous and ossifying epulides. Slow growing, firm lesions that occur in the premaxillary region. Cured by tooth extraction and excision of a small margin of surrounding alveolar bone.
What is focal fibrous hyperplasia (FFH)?
A benign reactive lesion of the oral cavity that is thought to result from irritation caused by dental plaque and calculus.
What percentage of oral tumours display bone lysis?
60-80%
What are the optimum modalities for assessing bone margins for oral tumours?
CT or MRI (radiography underestimates the extent to bone destruction).
Which lymph nodes should ideally be assessed as part of staging for oral tumours?
Mandibular, parotid, and medial retropharyngeal.
Lymph node size as determined by palpation is an unreliable indicator of metastatic disease.
What nerve blocks can be used to aid in mandibulectomy and maxillectomy?
Rostral mandibulectomy: mental nerve block at the level of the second premolar tooth.
Caudal mandibulectomy: mandibular nerve block near the mandibular foramen.
Rostral maxillectomy: infraorbital nerve block at the level of the fourth upper premolar tooth.
Caudal maxillectomy: maxillary nerve block below the ventral border of the zygomatic arch.
Ligation of which structure can be used to control excessive hemorrhage during mandibulectomy or maxillectomy?
Temporary or permanent occlusion of the carotid arteries.
What bony margin is required during mandibulectomy for oral neoplasia?
At least 1 cm, ideally avoiding the tooth roots.
Describe the different types of mandibulectomy based on extent of resection?
How can exposure to the dorsal ramus and temporomandibular joint be improved when performing a caudal mandibulectomy?
Removal of the zygomatic arch (can either be wired back in place or not replaced)
What is mandibular rim excision?
Preservation of the ventral mandible for excision of minimally invasive tumours. Results in reductions in post-operative pain.
Describe the different types of maxillectomy based on extent of resection?
What are some methods to control diffuse hemorrhage from the turbinates during maxillectomy?
Electrocautery, direct pressure, gelatin sponges. Topical application of epinephrine can also be useful.
What two axial pattern skin flaps may be useful to close large central or caudal maxillectomies that extend beyond the midline?
Superficial cervical or angularis oris.
During maxillectomy when is bleeding from the major palatine or infraorbital arteries most likely to occur?
During transection of the maxilla caudal to or including the infraorbital canal.
What oral procedure tends to be the most painful?
Rostral mandibulectomy with complete removal of the symphysis (as the mandibular bodies can move independently and create tension on the suture lines).
What complications are common following mandibulectomy/maxillectomy?
Dehiscence, ranula (central or caudal mandibulectomy), oronasal fistula (maxillectomy), mandibular drift, medial displacement of the upper lip margin and trauma from the lower teeth.
How can mandibular drift be addressed?
Use of orthodontic rubber chains, shortening or extraction of the mandibular canine tooth if impinging on the hard palate.
Are dogs able to eat and drink unassisted after mandibulectomy?
Yes. Dogs having greater than 50% removal may require initial assistance. Dogs with complete or near complete mandibulectomy will require hand feeding for life and may need to be given water via a bulb syringe.
What are the typical one year survival rates reported for oral tumours? What is the rate of recurrence? Which tumours are associated with the best prognosis?
70-90%, with recurrence <50%.
SCC and acanthomatous ameloblastoma are associated with the best survival, and excision may be curative. Fibrosarcomas have high recurrence rates due to their frequently caudal location. Malignant melanoma is highly metastatic but may be slowly progressive.
What are prognostic factors for oral tumours?
Tumour type (malignant melanoma and osteosarcoma have worse prognoses), tumour location (caudal tumours more likely to recur), completeness of excision.
When should radiation therapy be considered in the treatment of oral tumours?
Incomplete margins, large tumours, and tumours in the caudal oral cavity.
For tumours with incomplete margins recut is also an option and may be less expensive and time consuming.
What MST for SCC, fibrosarcoma, and melanoma was reported with megavoltage radiation therapy alone?
SCC: 36 months
Fibrosarcoma: 26 months
Melanoma: 8 months
For which oral tumour is chemotherapy often recommended? What is the survival time with adjunctive chemo?
Melanoma, often platinum based drugs.
MST for surgery and chemo was 15-months in one study.
What is the dosing regime for the melanoma vaccine (a human tyrosinase vaccine)?
Every 2 weeks for 4 wks, then boosters every 6 months.
What was the regional metastatic rate for feline oral SCC?
20%. Distant metastasis rare.
Very locally aggressive tumour and difficult to achieve complete resection.
What extent of mandibulectomy is likely to result in unwillingness to eat in cats?
> 50%
What is the local recurrence rate for feline oral tumours?
43%. More likely in feline SCC than fibrosarcoma or osteosarcoma, both of which have reported excellent long-term survival.
