Anatomy
The mental nerve is a terminal branch of ___. It exits the skull base from ____ and exits the mandible at the mental foramen ____.
V3
Foramen ovale
At the second pre-molar
This fracture subtype has the highest complication rate.
Angle fractures
With multiple fractures, the mandible has a tendency to _____, which if not corrected results in ____.
1. Flare outward
2. Facial widening and significant deformity
*More rigid fixation systems should be used to prevent widening.
Rank these vascularized bone free flaps from best to worst bone quality for mandibular reconstruction: scapula, radius, ilium, fibula
Fibula
Ilium
Scapula
Radius
Free 100 points!
:)
What important anatomical structures should be considered when plating body fractures?
Location of tooth root apices
Inferior alveolar nerve
Inferior alveolar artery
What is the treatment for a coronoid fracture?
MMF for 2 weeks is usually enough
Describe load-sharing versus load-bearing stability.
Load-sharing fixation: bone and hardware together share the functional loads applied across the fracture
Load-bearing fixation: fixation hardware can bear the entire functional load on the site of fracture
What are 2 soft tissue flap options for mandible reconstruction involving posterior defects when TMJ has been resected? What are their pedicles?
ALT free flap - descending branch of the lateral circumflex femoral artery
-Minimal donor morbidity
-Can be harvested at the same time that the tumor is being resected
2. VRAM free flap - deep inferior epigastric artery (DIEA)
Two most common causes of mandibular fractures.
*100 Bonus for sub-type of fx each mechanism causes
Assault - angle fractures
MVCs - body fractures
Name the actions of the muscles of mastication:
1) Lateral pterygoid
2) Medial pterygoid
3) Temporalis
4) Masseter
5) Geniohyoid, genioglossus, mylohyoid, digastric muscles
1) Lateral pterygoid: protracts (lowers) mandible (opens mouth)
2) Medial pterygoid: closes mouth
3) Temporalis: elevates and retracts mandible
4) Masseter: elevates mandible
5) Geniohyoid, genioglossus, mylohyoid, digastric muscles: depresses mandible
Describe the treatment for symphyseal/parasymphyseal fractures.
Miniplate fixation with at least two points of fixation
Describe the 2 methods of fixation involved in the AO/ASIF system for fixation.
1. Tension band and stabilization plate: A small plate is placed at the alveolar border to neutralize tensile forces; a larger plate is placed at the inferior border to neutralize compression and torsional stresses.
2. Reconstruction plate: A large plate is placed at the inferior border when segmental loss or comminution precludes placement of tension band; a single plate neutralizes tensile, compression, and torsional stresses.
Describe the contraindications for nonvascularized bone grafts.
Contraindications
-Defect >6 cm
-Radiation therapy
-Anterior mandibular defects
-Cancer patients
*vascularized bone free flaps are the Tx of choice for irradiated defects or bone defects >6 cm
How long do pediatric patients typically stay in MMF?
Usually 2-3 weeks given the favorable healing potential of children
The mesiobuccal cusp of the maxillary first molar lies distal to the buccal groove of the first mandibular molar. What is the Angle occlusion classification for this individual?
Class III Occlusion
Condylar fractures are frequently treated with closed reduction techniques, when is ORIF necessary?
ORIF is necessary when:
- Cannot reduce fx and it interferes with mandible ROM.
-Condyle is displaced into the middle cranial fossa.
-Bilateral condyle fractures with midface fractures to reestablish posterior vertical height
-foreign body present with the TMJ.
What are the load-sharing fixation options for ORIF of the mandible? (Diagram from REC module)
1. Normal Plates
2. Locking plates
3. Lag screws
What are the disadvantages of Mandibular Reconstruction Plate (MRP) alone for defects created after tumor excision?
MRP fracture will eventually occur if patient survives long enough, thus necessitating a flap reconstruction.
Extrusion rate is high, particularly when used in the anterior mandible or if the patient has postoperative radiotherapy
* Most MRP failures occur within 18 months, with a mean time to failure of 6-8 months.
What hardware can be used to aid with MMF in the pediatric population?
1. Circum-mandibular/aperture wires
2. Lingual splints
What embryologic cells give rise to the mandible?
Cranial neural crest cells
Name 4 indications to remove teeth in the line of fracture.
1. Grossly mobile teeth
2. Severe periodontal disease
3. Fractured roots
4. Exposed apices
Champy system for ORIF: What hardware is used? Draw Champy’s lines of osteosynthesis.
Monocortical miniplates
What are the advantages of the free iliac crest bone flap? What is the blood supply for this flap?
1. Excellent bone height
2. Internal oblique for intraoral cover
3. Bone suitable for endosteal implants
Blood supply: Deep circumflex iliac artery (DCIA)
What is the most common fracture type in children? What is the most important aspect of their treatment?
1. Condylar fractures
2. Early active therapy