Ch 67 Mandibular and Maxillofacial fractures Flashcards
Mandibular and Maxillofacial Fractures
- Because of the difficulty with evaluation of mandibular and maxillofacial trauma using conventional radiography, computed tomography (CT) evaluation is the preferred method of evaluation.
- Mandibular and maxillofacial trauma is most successfully managed by early definitive fracture fixation as soon as the patient has been stabilized.
- Direct bone healing will occur only with anatomic reduction and absolutely rigid fixation = goals of maxillofacial fracture repair. The result is quicker return of function with no adverse consequences associated with a large callus.
anatomy
anatomy superficial of head
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 fractured or loose and cannot be stabilised
- Endodontics and/or restorations or extractions may need to be performed if any future problems with the teeth are identified.
soft tissues
- oral fractures are contaminated > peri-op antibiotic recommended
- empiric choice (a broad-spectrum antibiotic, e.g., a first-generation cephalosporin)
- continued postoperative antibiotic use has been questioned
- infection generally is not a problem owing to the excellent vascular supply of the head.
What predisposes a fracture to infection?
Bone fragment motion and subsequent implant loosening interfere with revascularisation and healing and predispose to infection
Periodontal Disease
removal/debridement of the alveolar socket further weakens this diseased bone; therefore subsequent fractures are not uncommon.
- In simple fractures the recommended therapy involves complete dental prophylaxis and appropriate extractions.
- Any attempt of a bony repair in the face of severe periodontal disease must be performed judiciously > complex fractures and severe dental dz/osteolysis commonly resulting in nonunion and fixation failure
- functional mandible, and successful outcomes may include fibrous
Mandible biomechanics
- Bending forces are the primary forces acting on the mandible
- all muscular insertions are located on the caudal part > level of the ramus;
- The rostral mandibular fragment thus displaces in a caudoventral direction
- tensile stresses exist oral and compressive stresses exist at the aboral surface
- ramus, shear forces are maximal
- implant ideally placed on the tension surface = alveolar border of the bone
Maxillofacial Skeleton
- Support of the facial region is provided by a series of anatomic buttresses that distribute the masticatory forces to the head
- incisive bones and nasal bones are not part of the buttresses > therefore may not need to be stabilized
- If the medial buttresses are compromised, malocclusion is likely
- if the lateral buttresses are compromised, the orbit is likely to be affected
- buttresses in three dimensions the basic truss is a tetrahedron
- lateral buttress in the dog and cat may be the most clinically important
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?
Body: ventral approach
What are the recommended approached to the ramus and TMJ?
TMJ: Lateral approach (Ramus dorsal to the TMJ does not require repair)
approach to maxilla
first repair the side with the simplest fractures
- directly over the fracture in nasal, maxillary, or frontal areas
- Dorsal midline > avoiding neurovascular structures along the nose and most easily exposing the maxillary buttresses.
- attention first on the lateral, and then on the medial, maxillary buttresses
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
Intraosseous Wire
- rely on the static forces generated by the tension of the wire and by the frictional forces between corresponding bone fragments
- No stability is imparted in rotation or bending
- most successful if all bone fragments can be anatomically repositioned, thereby enabling the bone and implants to share any applied loads
- effective fixation, intraosseous wires must be placed along the lines of tensile stress
mandible
- a second area of fixation must be considered along the ventral bone margin to effectively neutralize shear and rotation
midfacial
- simple fractures that do not involve buttress support, however, may be treated by wire fixation
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 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
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 (applying a larger stabilization plate opposite the tension band miniplate)
Name the following instruments
A-C: Martin bending pliers
D-F: Synthes miniplate benders
G - ALPS plate benders
What implant is this?
uniLOCK, DePuy Synthes
- locking reconstruction plate which can be a good option as a larger ventral stabilisation plate
A number of successful reports have described the use of rhBMP-2 in the canine mandible to span very large gaps (5 to 7 cm)
In the ramus, what are the locations for the tension plate and the stabilisation plate?
Tension: Coronoid crest
Stabilisation: Condylar crest
Maxillofacial repair
- fractures may still result in occlusal malalignment if a fracture line traverses the dental arcade
- dental arcade: Miniplate adjacent to the alveolar border but below the infraorbital foramen and nasal cartilages
- nasal and frontal: (not associated with structural support) repaired to address cosmetic defects > neutralization or buttress devices to span these fractured areas
- facial frame: repaired with consideration for the appropriate buttresses > follow the orientation of the medial or lateral buttresses
conservative options for fractures (4)
Mandibular fracture repair techniques in cats: a dentist’s perspective
Freeman 2023
- composite maxillomandibular fixation (MMF)
- bignathic encircling and retaining devices (BEARDs)
- modified labial buttons
- muzzle coaptation (Figure 12)
rely on the immobilisation of the mandibles relative to the maxilla (or vice versa)
rigid fixation unlikely > rate of longer term complications will therefore be higher (malocclusion, malunion or non-union, delayed to normal eating, increased risk of aspiration)
Use of a novel three-dimensional
anatomical plating system for
treatment of caudal mandibular
fractures in cats: 13 cases (2019–2023)
McFadzean 2024
Ramus Anatomical Plate system
All cases achieved adequate anatomical
reduction, resulting in a functional and atraumatic occlusion postoperatively. No intraoperative complications were reported
The most common postoperative complication was swelling at the surgical site.
intraoral plate exposure in one cat, which required plate removal 10 months postoperatively
cadaver study - TMJ replacement
caudal miniplate bimechanical study
Both the locking and the Non-locking were
inferior to intact mandibles. Type of construct used did not affect the construct stiffness significantly
malleable L-miniplate
Traumatic split palate
- communication between the oral
and nasal cavities, allowing passage of water
and food into the nasal cavity - Large defects and unstable fragments are
better treated surgically - interfragmentary pin, with or without a figureof-
eight wire, depending on the apposition of
the fragments, is the treatment of choice
mucosal defect can be repaired with
absorbable suture; two-layer closure
feline skull injuries
Titanium mesh osteosynthesis for the treatment of severely comminuted maxillofacial fractures in four dogs
R. Vallefuoco 2021
Major goals in maxillofacial fracture:
- restore the dental occlusion,
- stabilise the major skeletal supports,
- restore the contour of the face
- achieve proper function and appearance of the face
all recovered uneventfully from the surgery and no complications were recorded
Titanium implants have lower suscepti bility to infection (0.6 to 4.5%)
delayed (>48 hours after trauma) treatment is pre
ferred to optimise patient care and favourable outcome
