What is the commonest age group for scaphoid fractures?
Although scaphoid fractures occur essentially at any age, adolescents and young adults are most commonly affected 1. Older patients falling in a similar manner are more likely to sustain a distal radial fracture (usually a Colles fracture).
What is the mechanism and causes of DISI?
It occurs because of a disruption of the dorsal intercarpal ligament. Causes include: wrist trauma +/- fracture and scapholunate ligament dissociation.
What is the pathology underlying SNAC?
In a SNAC wrist, the proximal scaphoid fragment usually remains attached to the lunate (which rotate together during extension), while the distal scaphoid fragment rotates into flexion. This results in abnormal contact in the radioscaphoid compartment, characterized by early styloid osteoarthritis between the distal scaphoid fragment and the radial styloid process.
There is an un-united scaphoid waist fracture, which has formed a pseudoarthrosis. There is an associated dorsal humpback deformity.
The dorsal band of the scapholunate ligament is intact, however there is an old bony avulsion at its scaphoid attachment. The central and volar portions of the scapholunate ligament are intact.
There is dorsal tilt of the lunate.
The lunato-triquetral ligament is intact.
Minor negative ulnar variance noted.
The TFC is grossly intact. Intermediate signal at the superior portion of the disc likely represents sprain.
There is moderate degenerative change at the dorsal aspect of the radio-scaphoid and radio-lunate joints, with chondral loss and subchondral sclerosis and bony spurring.
Scaphoid waist fracture non-union with pseudoarthrosis.
Intact SL ligament.
There are moderate degenerative changes at the radio-carpal joint, particularly dorsally. This would be in keeping with SNAC.