Ch 67 - Mandibular and Maxillofacial Fractures Flashcards

1
Q

How does the mandible differ from other bones in regards to bone healing?

A

It does not have a medullary cavity and has no haematopoietic cells

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2
Q

How do the maxillofacial bones differ from other bones in regards to bone healing?

A

Very thin bone, therefore has an increased surface area of bone compared to the volume it occupies giving a relatively greater vascularity and rapid healing

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3
Q

Is removal of teeth for fracture repair recommended?

A

No
- Shown to have an increased frequency of complications
- Not advised unless teeth are fractures or loose and cannot be stabilised

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4
Q

What predisposes a fracture to infection?

A
  • Bone fragment motion and subsequent implant loosening interfere with revascularisation and healing and predispose to infection
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5
Q

What are the three primary buttresses of the maxillofacial skeleton?

A

Rostral/medial
- nasomaxillary

Lateral
- Zygomaticomaxillary

Caudal
- lacrimal
- palatine
- pterygoid

Facial frame can be reconstructed utilising 2 of 3 buttresses. Caudal buttress is inaccessible

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6
Q

What are the two main goals of maxillaryfacial fracture repair?

A
  • Proper dental occlusion
  • Rigid skeletal fixation
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7
Q

List 2 options of endotracheal intubation when occlusion needs to be assessed intraoperatively

A
  • Pharyngostomy
  • Transmyelohyoid orotracheal intubation
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8
Q

What are the recommended approached to the mandibular body and to the TMJ?

A
  • Body: ventral approach
  • TMJ: Lateral approach (Ramus dorsal to the TMJ does not require repair)
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9
Q

What is the recommended approach for a maxilofacial fracture?

A
  • Dorsal midline for nasal (best way to avoid neurovascular structures and for exposing buttresses)
  • Gingival incision parallel to dental arcade
  • Incision directly over fracture if necessary
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10
Q

What are the basic priniciples of mandibular and maxillofacial fractures?

A
  • Mandibular reconstruction first (from caudal to rostral)
  • Followed by lateral and then medial maxillofacial buttresses
  • Anatomic reconstruction used for simple fractures
  • Occlusion used for comminuted fractures or fracture gaps
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11
Q

How many wires must be placed for effective intraosseous wiring?

A

At least 2!
- One along tension side
- Second stabilisation wire to neutralise shear and rotation forces

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12
Q

List some general guidelines from intraosseous wire placement

A
  • 18 - 20g wire (1.0 - 1.25mm)
  • Cross perpendicular to fracture line
  • Hand drilling (easier to avoid teeth)
  • Holes 5-10mm from fracture
  • Orienting drill holes towards the fracture line (facilitates positioning and tightening)
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13
Q

What form of wire tightening is best suited to maxillofacial fractures?

A

Twist method, maintian at least three twists

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14
Q

List some methods to prevent over-riding of fragments when using intraosseous wiring in the mxillofacial skeleton

A
  • Skewer pin
  • K-wire on outer surface of bone as an internal splint
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15
Q

List some methods of attempting to minimise the risk of premature pin loosening in mandibular ESF application

A
  • Fixation pins through both mandibles to engage 4 cortices (only possible in rostral 2/3)
  • Type 2 ESF (rostral 2/3)
  • Single arched connecting bar lateral to both mandibles and rostral to jaw
  • Multiple fixation pins (at least 2-3 per major fragment)
  • Positive-profile threaded pins
  • Acrylic connecting bar
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16
Q

What kind of bone healing occurs with an ESF?

A

Indirect bone healing
- Only supplies semi-rigid fixation
- Callous formation
- May interfere with occlusion

17
Q

What thread pitch is needed for adequate bone purchase for standard screws and for compression screws

A
  • Standard: Pitch equal to bone thickeness
  • Compression: Bone thickeness needs to be 2x pitch

Bone thickness of the canine and feline maxillofacial skeletal typically over 1 - 2 mm
Miniplate pitch is generally over 0.5mm and less than 1mm

18
Q

How many plates are required for mandibular fracture fixation?
What is the general recommendation regarding these plates?

A

At least 2 plates!
- Mini plate on the tension (alveolar) side. Usually using non-lockign screws to allow angulation of screws to avoid tooth roots
- A second plate on ventral aspect. Can be miniplate or standard plate, locking if available

19
Q

What are some mini-plate options?

A

Martin miniplate
- Low-profile, titanium plate
- Speciality plate bender to avoid hole deformation

Synthes maxillofacial system
- Titanium, varying thicknesses and sizes
- 2.0mm system usually used

Advanced Locking Plate System (ALPS, Kyon)
- Titanium
- Can accept both locking and standard screws
- Point contact

20
Q

What plate options are available for the Synthes 2.0mm Maxillofacial System?

A
  • Mini: 1mm thick x 4.5mm wide
  • Intermediate: 1.3mm thick x 5.0mm wide
  • Large: 1.5mm thick x 6.5mm wide
  • Extra large: 2mm thick x 6.5mm wide
21
Q

Name the following instruments

A
  • A-C: Martin bending pliers
  • D-F: Synthes miniplate benders
  • G - ALPS plate benders
22
Q

What is the difference reagarding the drill hole for miniplates as apposed to standard plates?

What drill speed is recommended for a miniplate?

A
  • Miniplate: Drill hole equal to screw core diameter for secure fit
  • Standard: Drill hole typically 0.1mm larger than screw hole diameter

Drill speed should be kept lower than 1000rpm and must remain monoaxial

23
Q

What options can be used where there are large mandibular defects?

A
  • Cortical allograft from ulna or rib (no larger than 40mm)
  • Stabilisation plate should have locking screws
  • Osteoinductive material (demineralised bone matrix)
  • rhBMP-2
24
Q

What implant is this?

A

uniLOCK, DePuy Synthes
- locking reconstruction plate which can be a good option as a larger ventral stabilisation plate

25
Q

In the ramus, what are the locations for the tension plate and the stabilisation plate?

A
  • Tension: Coronoid crest
  • Stabilisation: Condylar crest
26
Q

What are the fixation options for a condylar process fracture?

A
  • Interfragmentary compression screw
  • Fragment excision or condylectomy
  • Conservative management
27
Q

Fracture of what bone can have associated trauma to the eye and orbit?
Where do the lateral palpebral ligament and orbicularis oculi muscle attach?

A

The zygomatic bone
Attach to the zygomatic process (dorsal attachment of the orbital ligament)

28
Q

What procedure can be performed to cover exposed implants?

A

Single-pedicle buccal mucosal advancement flap

29
Q

How many wires must be placed for effective intraosseous wiring?

A

At least 2!
- One along tension side
- Second stabilisation wire to neutralise shear and rotation forces