After a traumatic injury several years ago, complicated with multiple fractures in the left arm, this 36-year-old man presented with chronic hand weakness (Fig. 3.1). The posture at rest (A-C) showed thenar and hypothenar atrophy with flexion of the third through fifth fingers, associated with contractures (mechanical restriction of the interphalangeal joints to passive extension, C). Forced flexion is only preserved for the distal phalanges of the first (flexor pollicis longus) as well as second through fifth fingers (flexor digitorum profundus) (D, E). Wrist extension is normal (F), but wrist flexion is compromised as only minimal resistance overcomes the flexion effort (G). There is some ulnar deviation when wrist flexion is attempted. There was hypesthesia to light touch and temperature in the ulnar aspect of the palm but not above the wrist, in the distal forearm.