Case of the week Details

• Figure A demonstrates fracture of coronoid process of ulna with fragment lying antero-superiorly. Posterior dislocation of ulna is also noted.
• Figure B demonstrates  mildly displaced fracture of radial head with posterior dislocation of radius at radiocapetallar joint.
• Figure C ; Volume rendered images clearly demonstrate both radial head and ulnar coronoid process fractures with posterior dislocation at elbow joint.

DIAGNOSIS:

• Complex fracture dislocation at elbow as described above in keeping with Terrible triad of elbow.

Discussion:

• The terrible triad of the elbow is a severe elbow fracture-dislocation pattern and is so-called because it has poor medium-to-long term outcome.
• If inadequately treated; it can result in chronic instability and severe arthritis.
• It occurs predominantly in adults; unlikely to be seen in children.
• Mechanism of injury: Most commonly, a fall onto an outstretched hand, arm in semi-flexion and supination.
• The fall is usually associated with a valgus posterolateral force which disrupts the capsuloligamentous structures sequentially from lateral to medial.

   

  
  • Computer-generated lateral three-dimensional (3D) view of the elbow demonstrates the normal anatomic configuration of the lateral collateral ligament complex, which includes the LUCL (red), RCL (blue), and annular ligament (yellow).
  • Computer-generated medial oblique 3D view shows the normal configuration of the anterior (red), posterior (blue), and transverse (yellow) MCL bundles.

Imaging features

• The terrible triad of the elbow is the association of:
  1. posterior elbow dislocation
  2. coronoid process fracture
  3. radial head fracture
• The posterior elbow dislocation usually involves the ulnohumeral joint.
• The coronoid fracture usually involve the tip or are type I fractures (O’Driscoll Classification).

Points to add in report

• Radial head fracture, coronoid process fracture (however small) with particular attention to anteromedial facet of ulna.
• Radiocapitellar and ulnotrochlear articulation.
• LUCL and MCL tears if possible.
• Status of nerves if assessable.
• Remember that volume rendering and MPR help in accurate estimation of severity of injury.

REFERENCES:

1. Mathew PK, Athwal GS, King GJ. Terrible triad injury of the elbow: current concepts. J Am Acad Orthop Surg. 2009;17 (3): 137-51. J Am Acad Orthop Surg (full text) – Pubmed citation.
2. Traumatic Elbow Injuries: What the Orthopedic Surgeon Wants to Know Scott E. Sheehan, George S. Dyer, Aaron D. Sodickson, Ketankumar I. Patel, and Bharti Khurana. RadioGraphics 2013 33:3, 869-888

Dr. Ashwini C. MD. FRCR.
Consultant Radiologist
Manipal Hospitals Radiology Group.

Dr. Sushant Mittal. MD
Cross-sectional fellow
Manipal Hospitals Radiology Group.