Proximal injury: supracondylar fracture of humerus
Distal injury
Carpal tunnel compression
Wrist laceration (suicide attempt)
Pronator teres syndrome: compression of the median nerve between the humeral and ulnar heads of the pronator teres
Motor deficits
The key is whether flexor digitorum profundus is damaged.
Nerves controlling flexor digitorum profundus branches out below the elbow. So it's spared in distal lesion, but included in proximal lesion. So the claw hand is more prominent in distal lesion.
Anterior Interosseous Nerve -> flexor digitorum profundus -> flexion of index and middle finger
Flexor digitorum profundus
has dual innervation: the medial part is supplied by ulnar nerve
Controls wrist, MCP, and DIP joints: flexion
Flexor digitorum superficialis
Controls wrist, MCP, and PIP joints: flexion
Lumbricals and interossei
Ape hand: inability to oppose and abduct the thumb due to injury of the proximal or distal median nerves impairing the thenar muscles' functions
Carpal tunnel syndrome
Results from a lesion that reduces the size of the carpal tunnel (fluid retention, infection, dislocation of lunate bone)
Median nerve – most sensitive structure in the carpal tunnel and is the most affected
Risk factors
Manual work: increased risk in workers using vibrating tools or prolonged, forceful, and repetitive flexion/extension of the wrist
