Final answer:
SLAC wrist is caused by Scapholunate Advanced Collapse, often due to untreated injuries to the scapholunate ligament, leading to degeneration of the wrist joint and resulting in pain and reduced range of motion.
Step-by-step explanation:
The deformity known as SLAC wrist is caused by Scapholunate Advanced Collapse, which is the most common form of progressive arthritic deterioration of the wrist. This condition typically occurs due to untreated scapholunate ligament injuries, which can lead to abnormal motion and wear between the bones of the wrist. Over time, this results in the degeneration of the wrist joint, specifically affecting the scaphoid, lunate, and the radius bones, leading to pain, reduced range of motion, and functional impairment.