Quick look at mandible dislocation: anatomy, causes, old and new ways to reduce.

1. Jaw
Dislocation
Joe Lex, MD, FACEP, MAAEM
Clinical Professor of Emergency Medicine
Department of Emergency Medicine
Temple University School of Medicine
Philadelphia, PA USA
joe@joelex.net @JoeLex5

2. Odds & Ends
• Mandere (L): to chew
• Late Latin: mandibula
• Middle French: mandible (late 14th C.)
• NOT just a “hinge joint”
–Hinge joints allow movement in only one
plane: ankle, elbow, and knee

5. Distal bone capable
of motion around
indefinite number of
axes

6. Movement in two
planes: flexion,
extension, adduction,
abduction,
circumduction

7. Like condyloid joint but no
axial rotation; movement
only in sagittal and frontal
planes

8. Motion in only one
plane

9. Rotation only:
pronation, supination

11. “ginglymoarthrodial”
both ginglymus
(hinging joint) and
arthrodial
(sliding joint)

14. Mandibular condyle articulates with
temporal bone in mandibular fossa

15. Mandibular fossa: concave depression
in squamous portion of temporal bone

16. Bones separated by articular disc 
divides TMJ into 2 distinct compartments

17. Some Anatomy
• Inferior compartment allows rotation of
condylar head around an instantaneous
axis of rotation
• First ~20mm of mouth opening
• Then mouth can no longer open without
superior compartment of TMJ active

18. Some Anatomy
• After 20 mm, not only is the condylar
head rotating within the lower
compartment, but the entire apparatus
translates
• Feel translation by putting your fist
against your chin, then try to open your
mouth more than 20 mm

19. Some Anatomy
• Resting position of TMJ is not with teeth
biting together
• Muscular balance and proprioceptive
feedback allow a physiologic rest
• There’s an interocclusal clearance or
freeway space of 2 to 4 mm

20. Some Anatomy
• Normal full jaw opening: 40-50 mm
• Only mandible moves during jaw
movement
• Normal mandible movements during
chewing are called excursions

21. Some Anatomy
• Two lateral excursions: left and right
• Forward excursion: protrusion
• Reversal of protrusion: retrusion

22. B I T E M
Buccinator
Internal (medial) Pterygoid
Temporalis
External (lateral) Pterygoid
Masseter

26. Usually after yawning or chewing

27. Punch in the chin

28. Punch in the chin with open mouth

29. Usually only with jaw fractures

30. Bilateral or unilateral after yawning

32. Punch in the chin

34. Punch in the chin with open mouth

35. Usually only with jaw fractures

37. Reduction

38. Traditional
• Most common: intraoral route
• You: gloved with thick gauze taped
securely on both thumbs
• Place thumbs on lower molars or on
ridge of the mandible intraorally,
posterior to molars, with your fingers
wrapped externally around mandible

39. Traditional
• With patient positioned so mandible is
below level of your elbows, apply firm,
slow, and steady pressure in a downward
and posterior direction
• If bilateral reduction is not possible, you
can reduce one side at a time

42. Traditional
• You may need procedural sedation
• You may need intravenous analgesia
• You may get bitten

43. A New Concept
The “Syringe” Technique: A Hands-Free
Approach for the Reduction of Acute
Nontraumatic Temporomandibular
Dislocations in the Emergency Department
Julie Gorchynski, Eddie Karabidian, Michael Sanchez
The Journal of Emergency Medicine, Volume 47, Issue
6, December 2014, Pages 676–681

44. Wow – really??
• 31 patients with acute nontraumatic TMJ
dislocation
• 30 had successful reduction
• 24 were reduced in less than 1 minute
• No recurrent dislocations at 3 day follow-
up

45. Equipment

47. Technique
• Patient in sitting position
• Place syringe between posterior upper
and lower molars or gums
• Have patient gently bite down and roll
syringe back and forth

48. Technique
• Syringe size depends on distance
between upper and lower molars / gums
and patient’s ability to open mouth
• Syringe acts as rolling fulcrum
• As molars / gums roll over syringe 
mandible glides posteriorly

49. Technique
• Anterior displaced condyle moves
posteriorly
• Masseter, pterygoid, and temporalis
muscles work in concordance
• Condyle slips gently back into its normal
anatomical position

53. Advantages
• No procedural sedation
• No intravenous analgesia
• Technique is simple and fast
• Technique is comfortable to patient
• Significantly reduced time in ED
• Lower cost: no procedural analgesia,
critical care monitoring or nursing care

54. …and best of all
NO BITTEN THUMB!!