Classic history and presentation: Intrinsic plus hand is a posture characterized by metacarpophalangeal (MCP) flexion with proximal interphalangeal (PIP) and distal interphalangeal (DIP) extension. This is caused by an imbalance between spastic intrinsic and weak extrinsic muscles of the hand. In early cases, patients complain of difficulty with gripping large objects. Later, the patient may develop contractures and lose the ability to extend their fingers at the MCP joint or flex at the IP joints.

Prevalence: Intrinsic plus hand is not more prevalent in any particular age group, nor is it more common in patients of any particular sex.

Risk factors:

• Rheumatoid arthritis
• MCP joint dislocations with ulnar deviation of the digits
• Trauma
• Stroke
• Parkinson disease
• Cerebral palsy
• Traumatic brain injury

Pathophysiology:

• Spastic intrinsic muscles lead to MCP joint flexion and IP joint extension.
• Flexor digitorum superficialis (FDS) and flexor digitorum profundus (FDP) weakness fail to provide the balancing flexion force to PIP and DIP joints.
• Extensor digitorum communis (EDC) weakness fails to provide the balancing extension force to the MCP joint.