An unusual wrist injury
A 30 year old man attends the Emergency Department after injuring his right wrist. He was playing rugby and landed awkwardly during a tackle with his hand trapped underneath another player. On arrival he is complaining of significant pain in his right wrist with reduced movement in all directions.
Examination of the wrist reveals reduced movement in flexion and extension and significant pain on pronation and supination.
You notice a hollow where his ulna styloid normally sits on the dorsum of his wrist.
The patient is taken to Resus, where he is sedated with propofol and his wrist is manipulated.
Before immobilisation you pause to review whether manipulation was successful.
His wrist is Cast immobilised in full pronation in a dorsal backslab.
The post manipulation X-ray is shown below.
The patient was discharged home with orthopaedic follow up arranged
What is the diagnosis?
Isolated volar distal radialulnar joint (DRUJ) dislocation
How are these injuries diagnosed?
History and Examination:
The mechanism for isolated volar DRUJ dislocation is most commonly due to hyper- supination of the forearm, particularly with the hand in a fixed position.
The patient presents with wrist pain, swelling and reduced ROM – particularly with pain on pronation.
The tell-tale sign of a hollow where the prominent ulna styloid normally sits (as seen above) is not always obvious due to patient body habitus and swelling.
Postero-anterior (PA) view will show increased overlap of radius and ulna
Lateral View demonstrates the distal ulna in a volar position
Both these findings are seen on the x-ray in this case.
A ‘true’ lateral is one in which the X-ray beam is centred between the two styloid processes (of ulna and radius) meaning the distal radius and ulna are superimposed on each other. Just a variation of 10 degree in either supination or pronation will result in an inaccurate lateral making assessing the DRUJ very difficult.
Other investigations are required when the diagnosis is unclear or there are concerns of associated injuries which may alter initial management. These may include:
CT scan is considered the best investigation for assessing DRUJ integrity and may demonstrate subtle subluxation or occult fractures both of which may not be visible on X-ray.
MRI is useful for assessing associated ligamentous injuries.
Arthroscopy is considered gold standard for assessing triangular fibro cartilage complex (TFCC) tears and allows repair if required.
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