Mandible Fractures Flashcards
What are the elevators of the mandible?
Temporalis
Medial Pterygoids
Lateral Pterygoids
Masseter
What are the depressors of the mandible?
Supra hyoid group of muscles: Stylohyoid Mylohyoid Geniohyoid Digastric
What are the origin, insertion, function and innervation of temporalis?
O: temporal fossa
I: Coronoid, Anterior surface of rams
F: elevator
N: V3 mandibular branch
What are the origins, insertions and innervation of medial Pterygoid?
O: medial aspect of lateral pterygoid plate
I: lingual aspect of angle and ramus
Fx: powerful elevator, synergistic w masseter
N: V3 medial pterygoid br.
What are the origin, insertion, function and innervation of Masseter?
O: Z arch (superficial head ant 1/2, deep head post 2/3)
I: buccal aspect of body and rams
Fx: powerful elevator, synergistic with medial pterygoid
N: V3
What are the origin, insertion, function and innervation of lateral pterygoid?
O: Lateral aspect of lateral pterygoid plate
I: TMJ joint capsule
Fx: Protrusion, translation, side to side motion
N: V3 lateral pterygoid br.
What are the origin, insertion, function and innervation of mylohoid?
O: mylohoid line along mandible
I: hyoid
Fx: elevates hyoid
N: ION (mylohyoid br)
What are the origin, insertion, function and innervation of geniohyoid?
O: inferior mental line
I: Hyoid
Fx: elevate tongue
N: hypoglossus (CN12)
What are the origin, insertion, function and innervation of stylohyoid?
O: styloid
I: Hyoid
Fx: displaces hyoid posteriorly
N: Facial (CN7)
What are the origin, insertion, function and innervation of digastric?
O: Mastoid process (post belly), Digastric fossa of mandible (anterior belly)
I: hyoid intermediate tendon
F: hyoid elevation
N: Ant belly, V3, Post belly CN7
Describe the functions and course of the Inferior Alveolar nerve
Sensory Branch of V3 to lower teeth, lower lip, chin, vestibular gingiva
Motor branch to mylohyoid
Enters mandibular ION canal at lingual cortex, inferior to molar root and exits at mental foramen, located inferior to 2nd premolar
Describe your landmarks for the marginal mandibular nerve
80%: lies posterior to facial artery, at the level of the inferior mandibular border. Anterior to master, approx. 3cm from angle
20%: lies anterior to facial artery and will 100% be above mandible border.
It is never >1,5cm below the mandible border
How do you classify mandible fractures?
By:
1- Location
2- Open vs closed
3- Displacement
4- Dentition (class 1 - teeth both sides, class 2- teeth on one side, class 3 - no teeth on either side)
5- Favourability
6- isolated / segmental / comminuted (JP added this)
What is the blood supply to the mandible
Inferior alveolar artery (travels with IAN in mandibular canal)
Muscle attachments
What mandible fractures are favourable?
Ramus
Some angle
What mandible fractures are unfavourable?
Parasymphyseal/symphysis
Some angle
High condylar (medially displaced by lateral pterygoid)
What physical finding do you anticipate with a condylar fracture?
Contralateral open posterior bite and translation to ipsilateral side with mouth opening
What physical finding do you anticipate with a bilateral candela fracture?
Anterior open bite
What specific imaging do you order for mandible fracture assessment? (3 answers)
1- Panorex (PA, lateral, RLO, LLO, Townes, submentovertex)
2- Panorex - 80% sensitive
3- CT (2.5mm cuts) - 100% sensitive
What is non-operative management for a mandible F#
Soft diet
Close follow-up (weekly)
What type of mandible fracture can be considered for non-operative management?
- minimal displacement
- no malocclusion
- normal ROM (no translation)
- patient : elderly, paediatric w greenstick/incomplete
- Location: condyle, ramus favorable, coronoid
What is centric occlusion?
Occlusion with maximal intercuspation of teeth
What is centric relation?
Occlusion with condyle seeded in glenoid fossa (in the most posterosuperior position)
What are methods of fixation for operative management of a mandible f#
1- splints 2- Circumdental wiring and arch bars 3- MMF 4- Rigid internal fixation (Rigid stability AO/ASIF) 5- Non-rigid Fixation (champy) 6- External fixation
Indications for ORIF of mandible F#
Mandible F#, malocclusion AND you are
Desire to avoid MMF/uncooperative/head injured
1- Unable to hold fixation with teeth
- Class 2 or Class 3 (or edentulous)
- Edentulous mandible* OA/JF
2- Unable to obtain anatomic reduction
- Comminuted
- Bone Loss, Bone Discontinuity * OA/JF
- Osteomyelitis
3- Unable to maintain reduction with a closed approach
- Favorable or unfavourable Class 1 where stability is desired
- Combination of Maxillary and mandibular F#
- Displaced or likely to rotate ***
What is functional stability versus rigid stability in mandible fracture fixation
Rigid stability - stability achieved w fixation plates that allow no movement across F# site
Functional stability - movement possible across f# gap but balanced by external forces within limits of what allow f# to heal
Load sharing: functional stability achieved w plate in conjunction with stabilizing forces by anatomic abutment of non-communized fracture segments
Load bearing - functional stability achieved by fixation system only
What are contraindications to MMF?
1- seizure disorder
2- Neurologic/psych disorder
3- Pulmonary compromise
4- Eating disorder
What are indications for Closed reduction and MMF ?
1- non displaced F# 2- grossly communited F# 3- edentulous patients (using splint) 4- Pediatric F# (at mixed dentition) 5- Isolated condylar Fracture 6- Coronoid fracture
Indications//situations for External fixator for mandible f#
OLD school answers below (in reality today, OA/JF, no use for ex fix, just tx infected bone with locking recon plate)
- Pathologic F#
- Traumatic bone loss
- Lack of soft tissue coverage
- Infected/contaminated wound/OM
- to maintain spatial relationships for cancer resection
- edentulous mandible if atrophic mandible but sufficient to hold two screws
What are advantages of internal fixation with plating
- avoid MMF
- ## rigid internal fixation (reliable fracture healing)
What are the disadvantages of plating?
- risk of injury to IAN, mental n, mar mandibular n
- risk of injury to tooth roots/buds
- periosteal stripping (blood supply)
- stress shielding (force transmitted to plate)
- risk of OM
What are indications for internal fixation with plating for mandible f#
- class 2 and class 3 fractures
- displaced f#
- condylar f# dislocation >12yo
- condylar # dislocation and another fracture
- MMF contraindicated
- edentulous patient
What are contraindications to internal fixation with plating?
- osteomyelitis
- metabolic bone disorder (renal osteodystophy, hyperparathyroidism)
- medically unfit for surgery
What are indications for Closed reduction
- medically unfit patient, unable to undergo fixation or open reduction
- condylar fractures
What is the role of compression plating in mandible fractures?
- to increase fracture compression and contact
What other methods of fixation must you use in combination with compression for mandible f#?
Tension band or arch bars to prevent lingual cortex distraction
What is the role of locking plate?
More forgiving if plate not bent perfectly
Acts as internal exfix
What is the theory of nonrigid fixation (champy/load sharing/functional stability)
- Only tensile forces are terrible
- Miniplates (monocortical) can be placed along lines of osteosynthesis
Where do you place miniplates for non rigid fixation?
1- Posterior to first PREmolar, miniplates are effective in the midbody position
2- Anterior to first PREmolar, two plates are used 4-5mm apart
When is nonrigid fixation not possible as a management strategy?
comminution
Bone loss
What is the theory of rigid fixation?
no micromovement at fracture site allows for 1’ bone healing
What are the AO principles?
- anatomic reduction
- functionally stable fixation
- atramatic operative technique
- ealy active pain free mobility
What are options for fixation according to Ao principle
1- Tension band (miniplate) + larger bicortical inferior plate (>=2.3mm) to neutralize compression and torsion forces
2- Large recon plate (2.3-3-0mm) to neutralize tensile, compressive,torsional forces
Describe the transoral approach (LBS)
1- incise through mucoa w 1cm cuff
2- avoid injury to mental nerve (anterior to 2nd PREmolar)
Describe transbuccal approach
external incision for trocar placement
Describe submental approach
external scar to expose and visualize the lingual cortex
Describe landmarks and position of structres to avoid in a submandibular approach (Risdon)
- 2cm below inferior border of mandible (to avoid marg mand br - located at border or up to 1.5cm below, lying over facial vessels)
- identify entire plane of platysma, dissect under and carefully cut through platysma to reveal deep cervical fascia
- facial vessels run anterior to masseter border
- the premasseteric notch identifies where the CN7 branch may be inferior to border
Describe retromandibular approach
- below earlob at posterior border of ramu, incision through skin subcut, then incise through platysma protecting potnetial facial n br below
- incise though perygomasseteric sling
- release masseter sling
Specific f#: Alveolar f#
arch bar, tooth splint, circumdental wires, dentures wired to jaw
Indications for tooth extraction
- Root apex exposed or fractured
- teeth preventing reduction
- grossly mobile teeth with evidence of periapical injury or disease
Management specific F#: symphysis
CR and Fixation with MMF if stable - rare
Usually ORIF b/c unstable or assocaited w condylar F#
ORIF with compression/lag screws
ORIF w compression plate at inferior border + tension or arch bar
ORIF with two miniplates
Management specific F#: body
CR and fixation - MMF - rare!!
Usually ORIF
ORIF w compression or non compression plate inferior border + arch bar or tension band or two miniplates
Management specific F#: angle F#
CR and fixation with MMF is associated fractures (condyle/midface)
USually ORIF with tooth etraction of 3rdmolar if diseased or preventing reduction
Traditional AO - compression plate at inferior border, 2 bicortical screws per side + tension band/arch bar superiorly
Miniplate- single 2.0mm miniplate on external oblique line -
Management specific F#- ramus F#
Undisplaced, maintianed V height w molars in place and reliable - soft diet 6wks and close observ
Undisplaced, missing molars so no V height maintenance, MMF 4-6 wks w elastics
Displaced, attempt CR and MMF
If failed CR, ORIF w two miniplate and retomandibular approach
Management of condylar f#
Non- surgical (soft diet 6wks):
- high neck or head (intracapsular) w no dislocation/malocclusion
- condylar neck
What are absolute and relative indications for ORIF of a condylar F#?
Absolute
- displacement into middle fossa
- foreign body within joint
- lateral extracapsular dislocation of condylar head
- inability to get adequate occlusion with closed methods
Relative
- bilat subcondular F#, disaplced + midface
- subcondylar f# with panface that needs re-established V height
- shorted ascending ramus
Classificaiton of edentulous mandible
according to amount of bone in the body of mandible
Mild atrophy - >20mm
moderate atrophy 10-20mm
Severe atrophy
Management minimally displaced edentulous mandible
- stable - conservative management
- unstable - MMF w circummandibular wire
Management displaced/comminuted edetulous manidble
- external approach
- recon plate (load bearing)
- minimal periosteal stripping
- primary bone grafting
PEdiatric fracture - indication for nonsurgical amangemetn
- high neck/head (intracapsular) condylar f#
- coronoid f#
- BODY,angle F# with minimal displacement
Pediatric fracture - options for fixation
- interdental wiring (minimally displaced) - NOT if
Describe ORIF principles in pediatric mandible fractures
- minimal periosteal stripping
- 1 miniplate 1-1.5mm inferior border only with monocortical screw
- resorbable plate if
What are complications of mandible fractures?
- malocclusion
- delayed union, non-union
- infection
- exposed hardware
What are cuases of malocclusion following mandible f# treatment
- failure to get centric relation b/c mandible is forced into occlusion wihtout seeding condyles
- failure to get centric occlusion w MMF before ORIF
- other f# missed
- arch bar prior to exposure may shorten mandible segments
- compression causing distraction of superior lingual cortex
- poor plate contouring
What is treatment of malocclusion
- elastics if arch bar in place
- orthodontics
- repeat OR
What is definiton of delayed union?
- not clinically stable by 6wks
Wha is definition of non-union
not clinically stable at 10wks
Causes of non-union/delayed union
- unstable fixation
- early MMF release
- hardware failure
- infection
- damaged teeth
Treatemnt of non-union/delayed union
If unstable, ORIF w rigid fixation, graft if gap after reduction >2cm
Causes o finfection
DIrectly realted to stability - RIGID fixation decreases fixation
Treatment of infection
aspirate for culture antibiotics debridement of necrotic sequestrae rigid fixation +/- BG if gap drainge of collection
Causes of exposed hardware
minor exposure no infection - leave until f# heals then remove
major exposure or infection - remove hardware and achieve rigid fixation.
What defines an angle fracture?
1st molar to angle
What defines a body fracture?
1st premolar to 1st molar
What defines a symphysis fracture?
between the canines
What defines a ramus fracture?
below sigmoid notch
What forces act on the mandible fracture?
tensile forces along alveolar ridge
compression and torsion forces along inferior border
What are landmarks for ION block?
5 mm below orbital rim, in line with medial limbus. If injecting intraoral, aim toward lateral canthus
What are landmarks for greater palatine block?
midway between midline and teeth, in line with 2nd molar
What are landmarks for Nasopalatine block?
midline, 5mm behind incisors
What are landmarks for Inferior Alveolar Nerve block?
1cm above occlusal plane and 1cm posterior to medial ramus
What muscle does IAN innervate?
mylohyoid
