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CB - Soft Tissue - Digestive System > 89 - Mandibulectomy and Maxillectomy > Flashcards

89 - Mandibulectomy and Maxillectomy Flashcards

1
Q

What are the major muscles of mastication?

Where do they originate/insert?

A

Masseter
- Originates on zygmatic arch
- Inserts on lateral caudal body and ventral ramus

Temporalis
- Originates from temporal region of scull
- Inserts onto dorsal portion of the ramus

Pyerygoideus
- Extends from pterygoid, palatine and sphenood bones
- Inserts on anglular process of the ramus

Digastricus
- Originates from occipital region
- Inserts on ventral border of the mandible

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2
Q

Blood supply to the mandible?

A

INFERIOR ALVEOLAR ARTERY

(Maxillary artery branch)

Enters mandibular foramen (medial surface near angle), courses rostrally within the medullary cavity

Exits mental foramen immediately caudal to the canine tooth

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3
Q

Which nerve supplies sensory innervation to the mandible and mandibular dentition?

A

MANDIBULAR NERVE

(Largest branch of the trigeminal nerve (CNV))

Follows course of artery, becomes inferior alveolar nerve and mental nerve as passes through mandibular and mental foramena

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4
Q

Which other anatomic structure needs to be considered during mandibulectomy?

A

Mandibular and sublingual salivary ducts
Run medial to the mandible

Ligation as needed but transection does not cause complications

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5
Q

Blood supply to the maxilla?

A

MAJOR PALATINE ARTERY
- Descending palatine branch
- Passes through caudal pallatine foramen and branches within palatine canal
- Passes through major palatine foramen
- Travels rostrally, ventral to the hard pallate between midline and maxillary teeth

INFRAORBITAL ARTERY
- Passes through maxillary foramen
- Exits laterally through infraorbital foramen rostral to carnassial

(Both branches of the maxillary artery)

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6
Q

Review this

A

TOBIAS BRUSHES OVER THREE BRANCHES OF THE MAXILLARY A HERE

The minor palatine comes directly first
Then descending palatine a branch travels through caudal and major palatine foramen to become major palatine a.
More rostrally, descending palatine gives rise to sphenopalatine a which gives off caudal, lateral and septal nasal a.
Then intraorbital branch comes off MA more rostrally, travels through maxillary foramen into maxillary canal where gives of alveolar branches, before emerging from infraorbital foramen and branching into lateral and rostral dorsal nasal as.

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7
Q

Which other bones of the skull may be excised during maxillectomy?

A

Incisive bone
* (Premaxilla)
* Contains incisor teeth

Nasal bone
- Long, slender, dorsal midline

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8
Q

Innervation to the maxilla

A

Maxillary nerve
(Branch of trigeminal)

Gives off infraorbital nerve which runs through the infraorbital canal and supplies maxillary dentition

Infraorbital n. must be transected during maxillectomy

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9
Q

Other than the neurovascular supply, which anatomical structures are transected during maxillectomy?

A

Parotid duct
(Papilla at Level of carnassial)

Zygomatic
(Papilla 1cm caudal to parotid)

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10
Q

What are the most common oral tumours in dogs?
(5)

A
  1. Malignant Melanoma
  2. Squamous Cell Carcinoma
  3. Fibrosarcoma
  4. Osteosarcoma
  5. Acanthomatous Ameloblastoma

(Peripheral nerve sheath tumour from infraorbital nerve and Multilobular osteosarcoma MLO are also DDx)

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11
Q

What is the % met rate of
Malignant Melanoma
SCC
Fibrosarcoma?

A

MM ~80%

SCC ~ 80%

FSA ~ 35%

Some studies report lower for SCC

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12
Q

Clinical features of malignant melanoma?

A

Older, small breed dogs

Breeds = Cockers, Mini poodles, Chow chows, Golden retrievers

Appearence = Darkly pigmented or amelanotic

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13
Q

Clinical features of SCC

A

Older, large breed dogs

Appearance = Flat, ulcerative, minimal external mass production

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14
Q

Clinical features of FSA?

A

Middle aged/older large breeds

Breeds = Labs and Goldens

Appearance = Proliferative, arises near maxillary carnassial, may involve hard pallate

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15
Q

Clinical features of OSA?

A

Medium to large breeds
Maxilla or mandible

Similar in terms of mets to appendicular OSA
(Mets to lungs ~15%)

Improved survival following excision compared to amputation for appendicular

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16
Q

Name two types of tumour arising from the periodontal ligament or odontogenic tissue in dogs

A
  1. Canine Acanthomatous Ameloblastoma (CAA)
  2. Peripheral odontogenic fibroma (POF)

(Focal fibrous hyperplasia)

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17
Q

Clinical features of CAA?

A

Typically rostral portion of the mouth

Non-malignant but locally invasive and may spread to adjacent teeth

Similar appearance to SCC

Arises from odontogenic tissue

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18
Q

Clinical features of POF

A

Fibromatous and ossifying epulides
(Fibroblastic connective tissue with focci of osteoid, dentinoid or cementum like matrix)

Slow growing and firm

Occur in pre-maxillary region

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19
Q

What increases the chances of a cure with POF?

A

Extraction of involved dentition

Removal of a small margin of alveolar bone

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20
Q

DDx for POF and CAA?

A

Focal fibrous hyperplasia (FHH)

Benign gingivial proliferation caused by irritation from dental plaque and calculus

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21
Q

What is the most common form of oral tumour in cats?

A

Squamous cell carcinoma

(FSA and OSA also reported)

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22
Q

Clinical features of feline SCC
(Behaviour, location, other structures involved)

A

Locally invasive
Intramedullary involvement is beyond limits of the mass

Location = Caudal to the canines

Other structures = Periocular region and tongue

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23
Q

Risk factors for oral SCC in cats

A

Tinned food

Flea collars

Tobacco smoke

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24
Q

What % of feline SSC have mets?

Where to?

A

20-30%
Regional LN mets

Distant mets rare

No clear benefit to adjuvant treatment

25
Q

How do oral FSA and OSA behave in cats?

A

Locally invasive

Low rate of distant mets

Excellent long term survival with Sx

26
Q

Why should biopsies be performed in cats with oral masses pre op?

A

Difficult to DDx SCC from
- Eosinophilic granuloma
- Odontogenic tumours

Alters approach and prognosis

27
Q

What staging is recommended pre op in cats?

A

Biopsy

Regional LN aspirates

CT/MRI of lesion for surgical planning

28
Q

Surgical considerations for cats?

A

SCC often non-resectible of maxilla due to invasion

Less well tolerated and may not regain prehension if >50% mandible removed

Feeding tube in all cases and may need for several weeks

If invade tongue caudally may be non-resectable if ligationof both lingual arteries required as leads to ischemic necrosis

29
Q

What staging is recommended for dogs?

A

Thoracic imaging
- Mets = Poor Px, Sx contraindicated

Head CT/MRI for surgical planning

Biopsy debatable
- Rarely impacts surgical plan
- But does change prognosis for survival
- Biopsy when decision to treat based on prognosis or if complete excision likely to be challenging

30
Q

What is the diagnostic accuracy of FNA in oral tumours?

A

FNA = 95% accurate in one study

31
Q

3 Considerations for Biopsy

A

Deep wedge/aspirates

Avoid necrotic regions

Biopsy via area that will be excised at Sx

32
Q

Which LNs drain the head?

A

Mandibular
Parotid
Medial retropharnygeal

LN SIZE poorly indicative of LN mets (Biopsy recommended)
(70% sens and 50% spec fo MM in dogs)

33
Q

Review LN anatomy for single approach

A

LN mets to one or more nodes in 35%
50% of these to mandibular LN
Single approach to excise parotid, mandibular and retropharyngeal recommended at time of Biopsy or Surgery

34
Q

Based on diagnostic imaging,
Which 3 signs would be concerning regarding complete resectability

A
  1. Caudal maxillary or mandibular lesions
  2. Lesions approaching or extending beyond midline
  3. Lesions encroaching on the nasal cavity or pharynx
35
Q

How should margins be determined for Mandibulectomy/Maxillectomy?

A
  • Minimum 1cm from tumour
  • Between tooth roots

(More if possible - 1-2 additional teeth )

Incomplete excision associated with poor Px

36
Q

Nomenclature of mandibulectomies

A

A = Rostral hemi

B = Rostral Mandibectomy

C = Central hemi

D = Caudal Hemi

E = Total Hemi

F = 3/4 Mandibulectomy

Rostal = lower incisors +/- canines
Central = premolars +/- molars
Cadual = Removal of the ramus

Remember mandible composed of 2 x hemimandibles
If just taking part of/ all of one = hemimandibulectomy
If taking a portion of both = mandibulectomy
Then named by specific location

37
Q

What is a mandibular rim excision?

Benefit?

A

Minimally invasive technique

Reserved for tumours with no ventral cortical bone involvement

Teeth in the region extracted and rim of alveolar bone is removed

Benefit = Reduced post op pain and preservation of cortical bone

38
Q

Describe the technique for Rostral mandibulectomy/hemimandibulectomy

A

Dorsal recumbency
Margins determined on imaging
Gingival margins 0.5cm beyond bone transection to preserve a cuff for closure
Cut to the bone and elevated
Symphysis transected with osteotome or saw (or preserve for small tumours)
Mandible transected with an saw/burr
Inferior alveolar a. ligated/transected within mandibular canal
Insepct bone margins and resect more if necessary
Restore mucosal integrity withouth tension

39
Q

Name 3 techniques used following mandibulectomy to relieve tension

A
  • Labial mucosa to gingival mucosa
  • Sublingual mucosa to skin
  • Supporting suture
    (caudal to the bone transection site around skin, mandible or teeth with rubber stent can be placed and removed after 7-10 days)
40
Q

Describe the technique for caudal hemimandibulectomy

A

Lateral recumbency
Full thickness incision from lip commisure to caudal ramus (total hemi) or directly over the ramus (caudal hemi)
Expose the zygomatic arch and perform zygomatic ostectomy
Transect the attachments of the masseter, digastricus, temporalis, pterygoideus and TMJ joint capsule
Ligate the inferior alveolar artery medial to the mandible before it enters the mandibular foramen
Transect at the symphysis or body depending on procedure
Allows reflection of the ramus to complete dissection medially
Replace or remove zygomatic segment and close incision

41
Q

How can cosmesis be improved after total hemimandibulectomy

A

Lip commisure advanced cranially to the level of 1st and 2nd premolar by excising the dorsal and ventral lip margins and suture together in three layers

Prevents lagging of the tongue out of the mouth

42
Q

Nomenclature for Maxillectomies

A

Rostral = Incisors (may include nasal planum)

Central = Premolars +/- one or more molar and canine

Caudal = Bone surrounding the molars +/- ventral orbit and rostral zygomatic arch

Rostral often crosses midline (Rostral maxillectomy)

43
Q

Describe the technique for rostral/central maxillectomy

A
  • Dorsal recumbency
  • Sharp incision at margin through labial and gingival mucosa and palate
  • Transect bone using osteotomy or saw (very thin)
  • Most likely area to bleed = CAUDAL TO OR INCLUDING INFRAORBITAL CANAL!! - Transect this region last.
  • Ligate or transect the major palatine a. and infraorbital a.
  • Haemostasis with electrocautery, gelatine sponge, pressure
  • Instill epinephrine (1mg diluted in 10 ml saline) and aspirate after 30-60 second contact time
  • Sutures in the nasal planum cartilage through drill holes in the nasal bones to prevent drooping
44
Q

Describe the technique for caudal maxillectomy

A
  • Oblique lateral recumbency
  • Incision of gingival and labial mucosa and palate
  • From lip commissure to caudal ramus to level of planner resection
  • Caudal border of resection in either the soft or hard palate
  • Ligation of the major palatine artery ligated/cauterised within the nasal cavity after transection
  • Complete all osteotomies with CAUDAL OSTEOTOMY LAST
  • Rapidly remove section by transecting intact turbinates and then locate, ligate, clip the vessel
  • Dorsally based flap of mucosa sutured to the palatine mucosa in single layer, interrupted or continous sutures
  • Preplaced sutures in hard palate may reduce tension
45
Q

How should central/caudal maxillectomy defects crossing midline be closed?

A

Mucocutaneous or Axial pattern flaps

e.g.
* Angularis oris buccal APF
* Haired angularis oris skin flap
* Suerficial cervical APF

(Difficult to close with labial mucosal flaps alone)

46
Q

How can the caudal maxillectomy approach be adapted if the zygomatic arch or rostral orbit is affected?

A
  • Comibined intraoral approach with rostral to caudal skin incision over the dorsolateral maxilla
  • Incision through labial mucosa and into the oral cavity ventrally creating a large, bipedicle flap of skin and mucos to expose the lateral maxilla and zyogmatic arch
47
Q

What additional precaution can be taken to control intraoperative haemorrhage during maxillectomy?

A

Permanent or temporary lgation of the carotid artery

48
Q

What is % owner satisfaction following maxillectomy/mandibulectomy?

A

85%

Explain functional and cosmetic results pre op

49
Q

Whichi nerve blocks can be performed?

A

Rostral mandibulectomy = Mental block (Mental foramen)

Other mandibulectomy = Mandibular block (medial side near angle of mandible)

Rostral maxilla = Infraorbital nerve block (dorsal to rostral aspect of carnassial)

Other maxillectomy = Maxillary nerve block (rostral to ramus below ventral zygomatic arch, caudal to the lateral canthus

50
Q

Additional anaesthesia consideration for mandibulectomy/maxillectomy

A

Place throat pack

51
Q

Postoperatie care considerations

A

Opioids
Buster collar
Soft food/water
IVFT until eats
Otube/ Gtube

52
Q

What transient changes can be expected following surgery?

A
  • Sublingual swelling (similar to ranula - tends to resolve in first week)
  • Rise and fall with respiration (tends to resolve in weeks)
  • Mild SC emphysema following maxillectomy (self limiting)
53
Q

Options for counteracting mandibular drift?

A
  • Titanium locking plate
  • Calcium-collagen compression resistant matrix with rhBMP 2
  • Horseshoe titanium plate secured bilaterally
  • Orthodontic rubber chains from canine tooth to ipsilateral 4th premolar to maintain occlusion
  • (Shorten or extract canine)

rhBMP contrainidicated in presence of tumour cells
Staged reconstruciton once margins assessed

54
Q

3 Major complications following mandibulectomy/maxillectomy?

A

Dehiscence
(Rostral for madnibulectomy, mucosal to palate line for maxillectomies)

Oronasal fistula
(Treat if symptompatic - angularis oris flap)

Mandibular drift

Trauma to tooth roots adjacent to osteotomy sites

55
Q

What location gives a worse prognosis?

A

Caudal
= poorer Px than rostral

Later ID, larger at the time of resection, more difficult to resect, invasion of other structure

56
Q

Which tumour type is relatively radiation resistant?

How can this be altered?

A

Malignant melanoma

Use of hypofractions recommended

57
Q

Which chemo drugs tend to be used for oral malignant melanoma?

A

Platinum based drugs
(Systemic or intralesional)
+/- Piroxicam

Considered due to high met rate

Large study reported no survival benefit for adjunctive chemo with surgery

58
Q

Name 2 additional treatments for maligant melanoma

A

Immunotherapy
(Biological response modifiers = Antitumoural effects)
- Corynebacterium parvum
- Liposome encapsulated muramyl tripeptide phosphatidylethanolamine (L-MTP-PE)

Melanoma tumour vaccine
Target tyrosinase which is overactive in melanoma cells
- Oncept, every second week for 4 treatments, then 6 month boosters

CB - Soft Tissue - Digestive System (5 decks)

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