Ch 67 - Mandibular and Maxillofacial Fractures Flashcards
How does the mandible differ from other bones in regards to bone healing?
It does not have a medullary cavity and has no haematopoietic cells
How do the maxillofacial bones differ from other bones in regards to bone healing?
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
Is removal of teeth for fracture repair recommended?
No
- Shown to have an increased frequency of complications
- Not advised unless teeth are fractures or loose and cannot be stabilised
What predisposes a fracture to infection?
- Bone fragment motion and subsequent implant loosening interfere with revascularisation and healing and predispose to infection
What are the three primary buttresses of the maxillofacial skeleton?
Rostral/medial
- nasomaxillary
Lateral
- Zygomaticomaxillary
Caudal
- lacrimal
- palatine
- pterygoid
Facial frame can be reconstructed utilising 2 of 3 buttresses. Caudal buttress is inaccessible
What are the two main goals of maxillaryfacial fracture repair?
- Proper dental occlusion
- Rigid skeletal fixation
List 2 options of endotracheal intubation when occlusion needs to be assessed intraoperatively
- Pharyngostomy
- Transmyelohyoid orotracheal intubation
What are the recommended approached to the mandibular body and to the TMJ?
- Body: ventral approach
- TMJ: Lateral approach (Ramus dorsal to the TMJ does not require repair)
What is the recommended approach for a maxilofacial fracture?
- 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
What are the basic priniciples of mandibular and maxillofacial fractures?
- 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
How many wires must be placed for effective intraosseous wiring?
At least 2!
- One along tension side
- Second stabilisation wire to neutralise shear and rotation forces
List some general guidelines from intraosseous wire placement
- 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)
What form of wire tightening is best suited to maxillofacial fractures?
Twist method, maintian at least three twists
List some methods to prevent over-riding of fragments when using intraosseous wiring in the mxillofacial skeleton
- Skewer pin
- K-wire on outer surface of bone as an internal splint
List some methods of attempting to minimise the risk of premature pin loosening in mandibular ESF application
- 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
What kind of bone healing occurs with an ESF?
Indirect bone healing
- Only supplies semi-rigid fixation
- Callous formation
- May interfere with occlusion
What thread pitch is needed for adequate bone purchase for standard screws and for compression screws
- 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
How many plates are required for mandibular fracture fixation?
What is the general recommendation regarding these plates?
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
What are some mini-plate options?
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
What plate options are available for the Synthes 2.0mm Maxillofacial System?
- 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
Name the following instruments
- A-C: Martin bending pliers
- D-F: Synthes miniplate benders
- G - ALPS plate benders
What is the difference reagarding the drill hole for miniplates as apposed to standard plates?
What drill speed is recommended for a miniplate?
- 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
What options can be used where there are large mandibular defects?
- Cortical allograft from ulna or rib (no larger than 40mm)
- Stabilisation plate should have locking screws
- Osteoinductive material (demineralised bone matrix)
- rhBMP-2
What implant is this?
uniLOCK, DePuy Synthes
- locking reconstruction plate which can be a good option as a larger ventral stabilisation plate
