OMFS - Mandibular Trauma

Question 1

What are the indications for external fixation (Ex-Fix)?

Answer 1

1. Extensive comminution with soft tissue loss (eg, severe gunshot wound)
   
   • Ex-fix may help preserve the vitality of small bony segments and allow soft tissue to heal prior to definitive tx
2. Infected fxs when extensive cellulitis and/or osteomyelitis, in combo with abscess drainage and bony debridement
   
   • Ex-fix helps circumvent:
     
     • Extensive extraoral incisions
     • Challenging neck dissections
     • Placement of internal hardware in grossly infected sites
3. Proximal segment control and space maintenance after severe trauma or resection

Not listed in Secrets, but also some other reasons to use ex-fix:

• Anticoagulated pts
• Worried about pt compliance

Question 2

What are the three main indications for using a load-bearing plate?

Answer 2

1. Comminution
2. Very little bony interface due to atrophy (eg, atrophic mandibles)
3. Avulsed or missing segments

Question 3

What are the four aboslute indications for ORIF of condylar fxs in adults? What are the three relative indications?

Answer 3

Absolute Indications

1. Inability to obtain adequate occlusion using closed reduction techniques
2. Displacement of condyle into middle cranial fossa
3. Severe angulation of condyle, lateral extracapsular displacement of condyle, or condyle resting outside of the glenoid fossa
4. Foreign body in joint capsule (eg, gunshot pellets)

Relative Indications

1. B/l condylar fxs with concomitant comminuted midface fxs
2. B/l fxs in edentulous pt when splints are unavailable or impossible because of severe ridge atrophy
3. Displaced condyle fx in medically compromised pt (eg, seizure disorder, psychiatric problems, alcoholism) with evidence of open bite or retrusion

Question 4

What are the indications to remove teeth in the fracture line?

Answer 4

1. Presence of obvious pathology (eg, caries, perio disease)
2. Gross mobility of involved tooth
3. Teeth that prevent adequate reduction of fxs
4. Fx root
5. Root surfaces or apices exposed in fx site

Question 5

What are the S/S assx with mand fxs?

Answer 5

1. Pain and tenderness at fx site
2. Changes in occlusion
3. Ecchymosis of FOM or skin
4. Crepitation on manual palpation
5. Soft tissue swelling and/or bleeding
6. Sensory disturbances (eg, numbness of lower lip)
7. Changes or deviation of mand on opening
8. Trismus
9. Flexion or segmental mobility of mand
10. Gingival tears and palpable fx line intraorally or at inf border

Question 6

What is considered compound? Why does it matter?

Answer 6

• When there’s external wound involving the skin, mucosa, or PDL (contaminated wound)
• These are at greater risk for infx

Question 7

What radiographs are included in a mand series, and what fxs are they helpful for identifying?

Answer 7

• R + L lateral oblique views
  
  • Body fxs
  • Ramus fxs
• PA ceph
  
  • Symphyseal region
  • Buccolingual displacement of body or angle
• Reverse Towne’s view
  
  • Mandibular condyles
• Panoramic
  
  • Gold standard for mand fx screening
  • If not avail, an additional view perpendicular to the lateral cortex may work
• CT Face is becoming the new hospital gold standard

Note

• Pan with PA ceph probably sufficient for dx

Question 8

Which mand fxs are likely to be missed on panoramic, and why?

Answer 8

• Symph/parasymph region
  
  • This is because there is some overlap and blurring in this area
• Condyles difficult to detect as well (overlap from other cranial and facial structures)
  
  • When detected, still hard to determine the degree of displacement
• Combo of these is most helpful (other than CT Face):
  
  • Pan
  • Towne’s

Question 9

What is the incidence of fxs in different areas of the adult mandible?

Answer 9

From Peterson textbook

Question 10

What is a horizontally favorable fx? What about a vertically favorable fx?

Answer 10

• Favorability determined by forces exerted by masticatory muscles on fx segments
• Favorable = not displaced by masticatory muscle pull
  
  • Determined by cephalad/caudal stability as seen on CT or oblique radiographs
• Unfavorable = line of fx permits displacement

Muscles of mastication

• Temporalis
• Masseter
• Medial pterygoid
• Lateral pterygoid

Question 11

How does muscle pull affect displacement of mand fxs?

Answer 11

• Those involved
• Muscles attached to ramus = exert superomedial displacement of proximal segment
  
  • Medial pterygoid
  • Temporalis
  • Masseter
• Muscles attached anteriorly = exert posteroinferior forces on distal segment
  
  • Digastric
  • Geniohyoid
  • Genioglossus
  • Mylohyoid
• Lateral pterygoid = displaces condyle anteriorly and medially because of insertion on pterygoid fovea

Question 12

What factors contribute to condylar displacement in pts with condylar fx?

Answer 12

• Lateral pterygoid
• Subcondylar fxs → anteromedial displacement of condyle due to lateral pterygoid
• Pt deviates to side of fx upon opening due to unopposed action of contralateral lateral pterygoid
• In higher condylar or intracapsular fxs above the insertion of the lateral pterygoid → small fragment can be seen displaced in a purely horizontal or vertical direction

Question 13

How do pediatric mandible fxs differ from adult mand fxs?

Answer 13

• Less common than in adults
• More commonly a greenstick fx (especially in condylar region)
  
  • Also more high and intracapsular condylar fxs
• Ossification ability of kids allows faster healing
  
  • As a result, many childhood mand fxs can be treated with:
    
    • Immobilization
    • Shorter period of time required for healing and soft diet
• ORIF reserved for severely displaced fxs
• Resorbable plates and screws usually used
• Must avoid damage to developing tooth buds (not a prob in adults)

Question 14

Risk factors that predispose mand fxs to infx?

Answer 14

1. Movement at fx site postoperatively = most common cause of postop infx
   
   • Loose, mobile hardware (eg, loose screw in otherwise stable plate)
   • May cause infx and drainage intraorally or extraorally (or both) until the source of infx is removed
2. Fxs through tooth-bearing areas (these should be regarded as contaminated)
   
   • Often seen in pts who sustain facial trauma and fail to seek tx
   • Contaminates fx with oral flora
3. Mucosal tears and fxs extending through PDL (also contaminates fx with oral flora)
4. Pts with polysubstance abuse (high risk for wound healing complications and osteomyelitis)
5. Pts with malnutrition (high risk for wound healing complications and osteomyelitis)
6. Bony sequestra
7. Devitalized teeth
8. Hematoma
9. Poor oral hygiene

Question 15

What percentage of mand fxs are multiple?

Answer 15

• > 50 % have multiple (due to arch form of mandible)
• Always try to find the other fx when you only see one on imaging

Question 16

What percentage of mand fx pts are assx with concomitant C-spine injury?

Answer 16

• ~43% of mand fx pts have other systemic injuries
  
  • C-spine found in 11%
  • Imperative to rule out C-spine fxs, especially in pts who are:
    
    • Intoxicated
    • Unconscious
    • Involved in MVCs

Question 17

Eight common complications assx with mand fx mngx?

Answer 17

1. Wound dehiscence = most common complication
2. Infx = most problematic → important cause of nonunion
3. Delayed union or malunion (usually due to infx or inadequate fixation)
4. Malocclusion
5. Facial or TGN injury
6. Damage to teeth or their roots
7. Hematoma
8. Osteomyelitis

Question 18

What potential fatal outcome can result from b/l mandibular parasymph fxs?

Answer 18

• Free-floating anterior mand segment → unstable anterior segment with tongue gets pulled back and down by suprahyoid musculature → airway embarrassment
  
  • “Gag bite”
  • Can lead to death
  • Genioglossus muscle attached to genial tubercles on lingual surface of mand
  • Suprahyoid muscles:
    
    • Digastric
    • Geniohyoid
    • Stylohyoid
    • Mylohyoid
• Serious consideration must be made to securing airway in early phase of mngx
• Urgent tx may be needed to place interdental wire stabilization or suture through tongue to allow extension

Question 19

What are the four main risk factors for developing TMJ ankylosis following trauma?

Answer 19

1. Intracapsular fx of mand condyle
2. Pediatric pt
3. Prolonged immobilization (or MMF)
4. Intraarticular hemorrhage with subsequent fibrosis of the joint

Question 20

What are the five main effects that MMF has on the masticatory system?

Answer 20

1. Osteoporosis of bone from disuse atrophy
2. Weakness of the muscles of mastication and decreased ROM
3. Capsular and pericapsular fibrosis
4. Cartilage thinning
5. TMJ stiffness

These are mostly reversible once MMF has been discontinued

Question 21

What sx techniques are available to tx mand fxs?

Answer 21

Most commonly:

1. Closed reduction and MMF with:
   
   • Ivy loops
   • Arch bars
   • Transalveolar screws
2. Closed reduction and fixation with gunning splints secured to stable osseous structures (circum-mandibular or perialveolar wires)
3. External fixation with pins (Ex-Fix, mostly for comminuted and grossly contaminated fxs)
4. ORIF with one or more of these:
   
   1. Intraoral incisions
   2. Extraoral incisions
   3. Endoscopically
   • With this technique, segments may be secured across the fx site with wires, plates, or lag screws (with/wo concomitant MMF)

Question 22

What are uniphasic and biphasic external fixation systems?

Answer 22

• Uniphasic (eg, modified Roger Anderson device) = involves two or more percutaneous pins on either side of the fx connected by a bar
  
  • Ex-Fix pin systems are also commercially available with pins, connectors, and carbon rods
• Biphasic (eg, Joe Hall Morris device) = use of temporary reduction appliance until a secondary device (usually cold cure acrylic) is placed to connect the pins

Question 23

What are the different tx options for mand angle fxs?

Answer 23

Depends on many factors, such as:

• Age and medical condition of pt
• Severity of fx
• Degree of displacement

In general → superior border plate fixation with minimum four screws placed across the fx line provides adequate stability

• Pt placed in MMF for 1-3 weeks (though not always necessary)
• Plates range from 1.0-2.0 mm
• Monocortical screws
  
  • Vary in length (5-7 mm)

Other options

• Inferior border plate or lag screws across the fx line
• If nondisplaced, MMF for 3-6 wks is a viable option too

If comminuted

• Ex-Fix or Recon plate (and/or MMF)

Question 24

What are the advantages of rigid internal fixation (RIF) in tx of mand fxs over other techniques? What are the disadvantages?

Answer 24

Question 25

When tx mand fxs, what is a tension band?

Answer 25

• During mand function, stress forces are exerted on bone in diff vectors depending on the location
• Superior border is under tension
  
  • Tension band is a mechanical means of resisting this tensile force (essentially, the tension plate stabilizes the destabilizing forces of the mand)
  • Can be accomplished with:
    
    • Superior border plate (if teeth are not in the way, eg, plate over the EOR in an angle fx)
    • Arch bars (if teeth are present on both sides of the fx line)
    • Superior border wire
    • Eccentric dynamic compression plate at inf border
• Inferior border is compressed
• Parasymph has rotational force

Question 26

What are dynamic compression, eccentric dynamic compression, and passive plating in rigid fixation?

Answer 26

• RIF was designed to allow primary bone healing even under functional loading
• In an effort to enhance stability, plates were developed to provide compressive forces across fx lines
• Compression plate at both superior and inferior border would ideally apply compressive forces throughout the fx, but it is usually not possible because of the presence of teeth superiorly, as well as other vital structures

Question 27

How are atrophic mand fxs treated?

Answer 27

• Considerable controversy on this topic
• Many authors, however, agree that most important element to success of tx = adequate and complete stabilization of the fx segments
  
  • Movement accounts for most of the postop nonunions
    
    • Especially when nonrigid or semirigid fixation (like below) is used:
      
      • Wires
      • Miniplates
      • Denture splints
    • These do not provide enough stability → fail with function
• ORIF with rigid fixation using recon plates or titanium mesh with immediate bone graft provides much more predictable results of healing
  
  • Always a concern for devascularization of the bone from open reduction and reflection of the periosteum
• Early and adequate stabilization with resumption of oral intake provides a better chance of primary bone healing
  
  • Especially since these fxs tend to occur in elderly and/or unhealthy pts