23-year-old male self presents to emergency following a fall whilst intoxicated with alcohol. He sustained injuries to his head and face

Examination reveals bilateral temporomandibular joint (TMJ) tenderness with tenderness and abrasion over the mentum. The patient is unable to open him mouth >1 finger breadth

CT Case 021 image 1 2
CT Case 021 image 3 4

Describe and interpret the CT images


here is an undisplaced fracture of the mandibular body at the symphysis menti (the midline).

There are bilateral comminuted fractures of the mandibular condylar head and neck with multiple displaced bony fragments.

There is bilateral anterior TMJ dislocation.

CT Case 021 1 2 label
CT Case 021 3 4 Label


This fracture pattern is known as a ‘guardsman fracture’ or ‘parade ground fracture’.

It is caused by a fall on to the midpoint of the chin. It results in a fracture of the symphysis or parasymphysis of the mandible at the point of contact with the ground, force is then transmitted to the mandibular condyles causing fracture and dislocation.

This fracture is typically seen in epileptics, elderly patients and occasionally in soldiers (from a fall forwards due to syncope after prolonged standing on guard).

This patient was managed with reduction in theatre with an ORIF.

Relative frequency of sites of mandibular fractures
Relative frequency of sites of mandibular fractures. MaxFacts




Emergency Medicine Education Fellow at Liverpool Hospital NSW. MBBS (Hons) Monash University. Interests in indigenous health and medical education. When not in the emergency department, can most likely be found running up some mountain training for the next ultramarathon.

Dr Leon Lam FRANZCR MBBS BSci(Med). Clinical Radiologist and Senior Staff Specialist at Liverpool Hospital, Sydney

Sydney-based Emergency Physician (MBBS, FACEM) working at Liverpool Hospital. Passionate about education, trainees and travel. Special interests include radiology, orthopaedics and trauma. Creator of the Sydney Emergency XRay interpretation day (SEXI).

Provisional fellow in emergency radiology, Liverpool hospital, Sydney. Other areas of interest include paediatric and cardiac imaging.

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