Anatomy and-fractures-of-the-mandible

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  • CLASSICAL INDICATIONS FOR CLOSED REDUCTION: GROSSLY COMMINUTED FX - HEAL BETTER IF PERIOSTEUM INTACT BUT MAY NEED EXT. FIX OR RECON. BAR FX WITH SIGNIFICANT LOSS OF SOFT TISSUE EDENTULOUS MANDIBLES - CLOSED REDUCTION WITH A GUNNING SPLINT FX IN KIDS- OPEN REDUCTION CAN DAMAGE DEVELOPING TEETH CONDYLAR FX - EARLY JAW MOBILIZATION IS REQUIRED TO AVOID ANKYLOSIS OF THE TMJ. KIDS - WEEKLY, ADULTS BIWEEKLY
  • CANDY CANE WIRES WEAR FACETS REMEMBER, MMF CONTRAINDICATED IN EPILEPTICS, ALCHOLICS, PSHYCHIATRIC ANDFRAIL PTS WHO CANNOT TOLERATED. ALSO DIABETICS
  • IVY LOOPS - NOT AS STRONG AS THE ARCH BAR, USEFUL IN SELECTIVELY BRINGIN OCCLUSAL PAIRS OF TEETH TOGHETHER. APPLICATION IN KIDS WITH M IXED DENTITION, IN PARTIALLY EDENTULOUS PTS WHO WILL HAVE ADDITIONAL FORMS OF FIXATION, AND PTS WHO NEED TEMPORARY OCCLUSION WHILE OTHER METHODS ARE BEING APPLIED (PLATES OR EXT-FIX) TO MAKE; 26 GUAGE WIRE IS CUT TO 16 CM. SMALL LOOP IS FORMED HEMOSTAT. THE ENDS ARE INSERTED BETWEEN TWO SUITABLE TEETH. THE MESIAL END IS PASSE D THROUGH THE LOOP AND THEN TIGHTENED 28 GUAGE WIRES GO THROUGH THE EYE LITS FOR FIXATION
  • CLASSICAL INDICATION FOR OPEN REDUCTION MALOCCLUSION DESPITE MMF DISPLACED UNFAVORABLE FX THROUGH THE ANGLE DISPLACED, UNFAVORABLE FX OF THE BODY OR THE PARASYMPHYSIS MULTIPLE FX OF THE FACIAL BONES - MANDIBLE IS FIXED FIRST PROVIDING A STABLE BASE FOR RESTORATION - BOTTOM UP MALUNION - OSTEOTOMIES AND ORIF ----- NON RIGID FIXATION MORE FORGIVING, EASIER TO PLACE. STILL REQUIRES MMT, USEFUL IN ANGLE AND PARASYMPHYSEAL FX. CAN GO EXTRAORAL OR TRANSORAL(FOR A HIGH WIRE)
  • USUALLY NECESSARY IN COMMUNUTED FX. THOSE WHO CANNOT TOLERATE MMF OR GSW
  • Anatomy and-fractures-of-the-mandible

    1. 1. ANATOMY ANDFRACTURES OF THE MANDIBLE
    2. 2. ANATOMY Mandible interfaces with skull base via the TMJ and is held in position by the muscles of mastication
    3. 3. Anatomic units of the mandible
    4. 4. Muscles of the mandible – Posterior group Origin Insertion Innervation ActionMasseter Inferior 2/3 zygomatic bone & medial Lateral ramus and angle of mandible Masseteric branch of anterior division of Elevate and protrude mandible surface of zygomatic mandibular nerve (V) archTemporalis Limits of temporal fossa Medial surface coronoid process, Two deep temporal branches of Elevates mandible, posterior fibres are anterior surface of mandibular nerve the only muscle ramus down to (V), sometimes fibres to retract the occlusal plane reinforced by middle mandible temporal nerveMedial Pterygoid fossa, mainly medial Medial surface of ramus and angle of Branch from main trunk of mandibular Pulls angle of mandible superiorly,pterygoid surface of lateral mandible nerve anteriorly and pterygoid process mediallyLateral Upper head from infratemporal surface Upper head inserts into TMJ capsule, Branch of anterior division of Lateral movement, protrusion, importantpterygoid of skull, lower head lower head into mandibular nerve in active opening of from lateral pterygoid anterior surface of the mouth plate condylar neck
    5. 5. Muscles of the mandible – Anterior group Origin Insertion Innervation ActionGenioglossus Superior part of mental spine of Hypoglossal nerve (XII) Depresses tongue, posterior part mandible protrudes tongueGeniohyoid Inferior part of mental spine of mandible Body of hyoid bone C1 through hypoglossal nerve Pulls hyoid bone anterosuperiorly, (XII) shortens floor of mouth and widens pharynxMylohyoid Mylohyoid line of mandible Raphe and body of hyoid bone Mylohyoid nerve, a branch of inferior Elevates hyoid bone, floor of mouth and alveolar nerve (V3) tongue during swallowing and speakingDigastric Anterior: Digastric fossa of mandible Intermediate tendon to body and superior Anterior: Mylohyoid nerve (V3) Depresses mandible, raises hyoid bone Posterior: Mastoid (greater) horn of Posterior: Facial and steadies it during notch of temporal hyoid bone nerve (VII) swallowing and bone speaking
    6. 6. Muscles of Mastication OUTER SURFACE
    7. 7. Muscles of Mastication INNER SURFACE
    8. 8. Muscles of Mastication 4 muscles of mastication  Masseter  Temporalis  Medial pterygoid  Lateral pterygoid Supplied by V3, testament to same embryologic origin as the mandible from the 1st branchial arch
    9. 9. Masseter Divided into 3 heads  Superficial:  largest head  Arises anterior 2/3rds of the lower border of the zygomatic arch  Wide insertion to angle, forwards along lower border and upwards to lower part of ramus  Intermediate:  Middle 1/3 of the arch  Deep:  Deep surface of the arch  Action: elevator and drawing forward the angle
    10. 10. Masseter Intermediate and deep fuse and pass vertically downwards to fuse with ramus Nerve and artery divide muscle incompletely into 3 parts Masseteric nerve (Br of anterior division of V3) runs between deep and intermediate Br of superficial temporal and transverse facial runs between superficial and intermediate
    11. 11. Temporalis Arises temporal fossa between inferior temporal line and infratemporal crest Inserts at posterior border of the coronoid process and ascending ramus Upper and anterior fibres elevate the mandible Posterior fibres (horizontal) retract the mandible (only muscles that do so)
    12. 12. Medial pterygoid 2 heads:  Deep:  Larger  Medial surface of the lateral pterygoid plate and the fossa between 2 plates  Superficial :  Tuberosity of the maxilla and pyramidal process of palatine bones  Insert lower and posterior part of angle (with masseter)  Action: upwards and forwards and medially
    13. 13. Lateral pterygoid 2 heads:  Superior:  Infratemporal fossa  Inferior:  Lateral surface of the lateral pterygoid  Fuse into a short thick tendon that inserts into pterygoid fovea  the upper fibres passing into articular disc and anterior part of the capsule Action: side-to-side plus only muscle to open jaw
    14. 14. Temporomandibular Joint Articulation  Synovial joint between the condyle of the mandible and the mandibular fossa in the squamous part of the temporal bone  Both bone surfaces covered with layer of fibrocartilage identical to the disc  No hyaline cartilage, therefore an atypical joint
    15. 15. Temporomandibular Joint Unique feature of the TMJs is the articular disc. Composed of fibrocartilaganeous tissue Divides each joint into 2:  Inferior compartment  Superior compartment
    16. 16. Temporomandibular Joint Inferior compartment  Allows for pure rotation of the condylar head,  corresponds to the first 20 mm or so of the opening of the mouth. (opening and closing movements) Superior compartment  involved in translational movements  sliding the lower jaw forward or side to side
    17. 17. Temporomandibular Joint
    18. 18.  Temporomandibular Joint Atypical synovial joint separated into upper and lower cavities by a fibrocartilaginous disc  No hyaline cartilage Capsule attached high on neck of mandible around articular margin, then to transverse prominence or articular tubercle and as far posteriorly as squamotympanic fissure Fibrocartilage attached around periphery to capsule  Anteriorly near head of mandible, so mobile  Posteriorly near temporal bone, so more fixed  Thinner in middle than periphery, crinkled fibres to allow movement and contouring Lateral TM ligament is a stout fibrous band passing from zygomatic arch to posterior border of neck and ramus, blending with capsule  Tightens with movements away from rest Sphenomandibular ligament runs between sphenoid spine and lingula of mandible  Remains constant tension through range of motion as the lingula is the axis of rotation of the mandible Sensation supplied by auriculotemporal nerve with some supply from nerve to masseter (Hiltons law)
    19. 19. TMJ Ligaments 3 ligaments associated with the TMJ:  1) Temporomandibular ligament (Major)  is really the thickened lateral portion of the capsule, and it has two parts:  an outer oblique portion (OOP) and an inner horizontal portion (IHP)  Lower border of zygomatic arch to posterior border of the neck and ramus
    20. 20. TMJ Ligaments 2) stylomandibular ligament (minor)  separates the infratemporal region from the parotid region  runs from the styloid process to the angle of the mandible 3) Sphenomandibular ligament (minor)  runs from the spine of sphenoid to the lingula of the mandible
    21. 21. TMJ Ligaments The minor ligaments are important in that they define the limits of movements,  ie the farthest extent of movements of the mandible.  Not connected to joint However, movements of the mandible made past these extents functionally allowed by the muscular attachments BUT will result in painful stimuli
    22. 22. TMJ Ligaments
    23. 23. TMJ Ligaments
    24. 24. Mandibular Forces
    25. 25. Nerve Supply Inferior alveolar nerve branch of the mandibular division of Trigeminal (V) nerve, enters the mandibular foramen and runs forward in the mandibular canal, supplying sensation to the teeth. At the mental foramen the nerve divides into two terminal branches:  Incisive nerve: supplies the anterior teeth  mental nerve: sensation to the lower lip
    26. 26. Evaluation - History Always remember ABCs of life along with secondary and tertiary survey Mechanism of injury  MVA associated with multiple comminuted #  Fist often results in single, non - displaced #  Anterior blow to chin - bilateral condylar #  Angled blow to parasymphysis can lead to contralateral condylar or angle #  Clenched teeth can lead to alveolar process #
    27. 27. Physical Exam - Occlusion occlusion Change in occlusion - determine preinjury Posterior premature dental contact or an anterior open bite is suggestive of bilateral condylar or angle fractures Posterior open bite is common with anterior alveolar process or parasymphyseal fractures Unilateral open bite is suggestive of an ipsilateral angle and parasymphyseal fracture Retrognathic occlusion is seen with condylar or angle fractures Condylar neck # are assoc with open bite on opposite side and deviation of chin towards the side of the fx.
    28. 28. Angle’s classification Class I:  Normal  Mesial buccal cusp of the upper 1st molar occludes with mesial buccal groove of the mandibular molar Class II:  Retrocclusion, mandibular deficiency Class III:  Prognathic occlusion, maxillary deficiency, mandibular excess
    29. 29. Dental classification of occlusion Angle’s classification (1887)  Based on relationship of permanent 1st molars and to a lesser degree the permanent canines to each otherClass Molar Canine relation relationI Mesiobuccal cusp of maxillary 1st molar is in Maxillary permanent canine occludes with distal ½ of line with buccal groove mandibular canine and mesial of mandibular 1st molar half of mandibular 1st premolarII Buccal groove of mandibular 1st molar is Distal surface of mandibular canine is distal to mesial surfaceDiv1 – Overjet distal to mesiobuccal of maxillary canine by at leastDiv2 – Lingual cusp of maxillary 1st width of a premolarinclination molarIII Buccal groove of mandibular 1st molar is Distal surface of mandibular canine is mesial to mesial mesial to mesiobuccal surface of the maxillary canine cusp of maxillary 1st by at least the width of a molar premolar
    30. 30. Malocclusion
    31. 31. Physical Exam Anaesthesia of the lower lip Abnormal mandibular movement  unable to open - coronoid fx  unable to close - # of alveolus, angle or ramus  trismus Lacerations, Haematomas, Ecchymosis Loose teeth swelling
    32. 32. Physical Exam Multiple fractures sites are common:  1 fracture: 50%  2 fractures: 40%  >2 fractures: 10% Dual patterns:  Angle contralateral body  Symphysis and bilateral condyles 15% another facial fracture
    33. 33. General Principles of ABCs treatment Tetanus Nutrition Almost all can be considered open fractures as they communicate with skin or oral cavity Reduction and fixation Post-op monitoring for N/V, use of wire cutters Oral care - H2O2 , irrigations, soft toothbrush
    34. 34. Aims of Management1) Achieve anatomical reduction and stabilisation2) Re-establish pre-traumatic functional occlusion3) Restore facial contour and symmetry4) Balance facial height and projection
    35. 35. Fracture Frequency
    36. 36. Classification of Fractures Open vs Closed Displaced vs non-displaced Complete vs greenstick Linear Vs comminuted Relationship to the teeth  Class I: teeth both sides of fracture  Class II: teeth one side of fracture  Class III: edentulous Favourable vs unfavourable
    37. 37. Treatment options No treatment Soft diet Maxillomandibular fixation Open reduction - non-rigid fixation Open reduction - rigid fixation External pin fixation
    38. 38. IMF
    39. 39. IMF
    40. 40. Islet IMF
    41. 41. Open reduction - nonrigid fixation
    42. 42. External Fixation
    43. 43. Principles of fixation Usually one plate with 4 cortices of fixation are required for adequate immobilisation Anterior to mental foramen, 2 levels of fixation are required to overcome torsional forces Unfavourable fractures usually require 2 levels of fixation for stability Fixation along Champy’s line allows better fixation due to the strong buttress structure
    44. 44. Condylar fractures Classification  Condylar  Intra- or extra-capsular  subcondylar Watch for intracranial condylar head Condylar heads tend to dislocate anteromedially towards pterygoid plates due to pull from medial pterygoid Indications for open reduction are angulation > 30°, fracture gap > 5mm, lateral override, bilateral fractures of head/neck  Risks avascular necrosis of condylar head, facial nerve injury, hypertrophic scarring (10%)
    45. 45. Alveolar fractures 3% total fractures, often in combination with other fractures Can often be reduced and fixed with arch bars (can be acrylated) or Essig splints May require monocortical plate fixation Teeth are often insensate and require orthodontic evaluation Gross comminution or loss of blood supply increases the risk of infection and primary debridement of the devitalised segment with soft tissue coverage may be a better long term option Can have compression fractures of alveolus resulting in loosened teeth  Miller Grade 1 - < 1mm looseness  Miller Grade 2 – 1-3mm looseness  Miller Grade 3 - > 3mm looseness and loose superoinferiorly in socket
    46. 46. Teeth in fracture line Important in fracture stability when using IMF Less important in fracture stability when plates used to fix fractures Reasons to extract the tooth  Severe tooth loosening with chronic periodontal disease  Fracture of the root of the tooth  Extensive periodontal injury and broken alveolar walls  Displacement of teeth from their alveolar socket  Interference with bony reduction and reestablishing occlusion Third molars tend to cause the most controversy  Third molars that are erupting normally need not be removed unless they are interfering with fracture reduction  Impacted third molars can be removed as they are rarely a functional part of the occlusion  Removal of third molars unnecessarily leads to increased conversion from closed reduction to open reduction
    47. 47. Edentulous mandible No occlusal plane Lack of mandibular height due to atrophy Changed pattern of fracture – body is more common as atrophy is greatest Changed position of inferior alveolar nerve and artery Changed pattern of blood supply – more circumferential than radial Role of recon plates and bone grafting Role of dentures
    48. 48. Paediatric mandible Often greenstick fractures that heal within 2-3 weeks 65% mandibular fractures in children < 10yo are in condylar region, 40% in 11-15yo Arch bars are common use to avoid damage to secondary teeth, but primary teeth are conically shaped Acrylic splint secured by circumferential wiring is safe and effective Condyle is the major growth centre of the mandible and has some ability to remodel, and poorly tolerates periosteal stripping Crush of condylar head (esp. < 3y) can lead to altered mandibular growth and TMJ ankylosis secondary to haemorrhage
    49. 49. Complications Airway esp with IMF (wire cutters and pre-op education) Infection Delayed and non-union  Inadequate immobilisation, fracture alignment  Inteposition of soft tissue or foreign body  Incorrect technique Inferoir alveolar nerve damage  56%pre-treatment  19% post-treatment Malocclusion TMJ ankylosis esp intracapsular condyle #

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