Peripheral nerve entrapment at the wrist in pyrophosphate arthropathy.

Of 200 consecutive patients with confirmed pyrophosphate arthropathy, clinically significant median nerve entrapment was found in 14 (14%) of those with wrist involvement. Three of these had electromyographically confirmed combined median and ulnar nerve entrapment at the wrist (bilateral in 2). Chondrocalcinosis, but not changes of arthropathy, was closely associated with the presence of entrapment (p less than 0.001), implying that soft tissue factors are important in causation. Treated hypothyroidism was more common in those with nerve entrapment (p less than 0.01), suggesting a possible interaction of multiple factors in the pathogenesis of nerve entrapment.