ulnardeviation

Ulnardeviation, also called ulna deviation or ulnar drift, refers to movement or a deformity of the hand in which the fingers drift toward the ulnar (little finger) side. The term can describe normal wrist motion toward the ulnar side or, more commonly in clinical contexts, a pathological drift of the fingers at the metacarpophalangeal (MCP) joints.

In normal anatomy, the wrist and fingers can exhibit a range of motion including some degree of ulnar deviation when moving the hand toward the little finger side. The amount of deviation varies among individuals and is balanced by radial deviation in other movements.

Pathologic ulnar deviation is most notably associated with inflammatory joint diseases, particularly rheumatoid arthritis. In longstanding RA, destruction of MCP joints and disruption of supporting ligaments and tendons cause the fingers to drift toward the ulnar side. Extensor tendons may slip toward the ulnar direction, and, together with joint subluxation and lax collateral ligaments, produce a characteristic ulnar drift of the digits. Ulnar deviation can also occur after trauma or in other inflammatory or connective tissue conditions, though RA remains the classic example.

Diagnosis is typically clinical, based on observation of finger alignment, joint swelling, and activity-related changes. Imaging may be used to assess joint damage. Management focuses on treating the underlying disease (e.g., disease-modifying antirheumatic drugs or biologics for RA), along with hand therapy and splinting to limit drift and preserve function. In some cases, surgical options may be considered to correct deformity or restore function.

Prognosis depends on the underlying cause and treatment response; with early disease control, progression of deformity can be slowed, though ulnar drift may persist in established cases.