Distal radioulnar articulation

Structure

The distal radioulnar articulation is formed by the head of ulna, and the ulnar notch of the distal radius.****

Articular disc

The joint features a triangular articular disc that is attached to the inferior margin of the ulnar notch by its base, and to a fossa at the base of the styloid process of the ulna by its apex. The articular disc acts to firmly bind the distal extremities of the two bones together.****

Ligaments

The articulation is reinforced by the palmar radioulnar ligament, and dorsal radioulnar ligament.****

Image:RightHumanPosteriorDistalRadiusUlnaCarpals.jpg|Distal ends of radius and ulna along with the bones of the wrist and hand Image:Gray421.png|Transverse section across distal ends of radius and ulna.

Function

The function of the radioulnar joint is to lift and maneuver weight load from the distal radioulnar joint to be distributed across the forearm's radius and ulna as a load-bearing joint. Supination of the radioulnar joint can move from 0 degrees neutral to approximately 80-90 degrees where pronation of the radioulnar joint can move from 0 degrees neutral to approximately 70-90 degrees. Supination (palms facing up) vs. pronation (palms facing down). Muscles that contribute to function are all supinator (biceps brachii, brachioradialis, and supinator) and pronator muscles (brachioradialis, pronator quadratus, and pronator peres).

Clinical significance

Injuries to the distal radioulnar articulation often result from falls onto an outstretched hand. Injury can occur with concurrent fracture of the distal radius, the ulna, or can be isolated. For the upper limit of the distal radioulnar distance, sources vary between 2 mm and 5 mm. A classification system has been proposed by Estaminet and colleagues.

Estaminet classification

Estaminet classified injuries of the distal radioulnar articulation into four categories with two subclasses: purely ligamentous (subclass A) and those with associated boney injury (subclass B).

• Estaminet I - Attenuation on MRI only
• Estaminet II - Volar distal radioulnar ligament is involved. Unstable in supination. Fixation should be in pronation.
• Estaminet III - Dorsal distal radioulnar ligament is involved. Unstable in pronation. Fixation should be in supination.
• Estaminet IV - Both ligaments are involved. Unstable in both supination and pronation. Fixation is in neutral.

References

References

1. Dyan V. Flores. (18 Nov 2022). "Distal Radioulnar Joint: Normal Anatomy, Imaging of Common Disorders, and Injury Classification". Radiographics.
2. Gray, Henry. (1918). "Gray's Anatomy".
3. Chummy S. Sinnatamby. (2011). "Last's anatomy: regional and applied.". Elsevier.
4. (2013). "Functional anatomy of the distal radioulnar joint in health and disease". The Annals of the Royal College of Surgeons of England.
5. (2012). "Distal radioulnar joint injuries". Indian Journal of Orthopaedics.
6. Jack A Porrino Jr. (15 March 2022). "Distal Radial Fracture Imaging".
7. Richard A. Berger, Arnold-Peter C. Weiss. (2004). "Hand Surgery, Volumes 1-2". Lippincott Williams & Wilkins.
8. Estaminet et al. Estaminet-Klassifikation von distal radioulnar Aussprache-Trauma. 20. Jahresversammlung der europäischen Orthopädischen Forschungsgesellschaft (EORS 2012), am 26–28 September, Amsterdam, Die Niederlande