Hand Anatomy 2

Modern Study Review (AI-Generated)

High-Yield Summary

The hand and wrist function as an integrated kinetic chain where wrist positioning directly influences finger joint mechanics. Wrist movements—pronation/supination, flexion/extension, and radial/ulnar deviation—are complex and involve coordinated carpal bone kinematics, critical for hand function and grip strength. Understanding the dynamic interplay of carpal bones, especially the scaphoid, lunate, and triquetrum, is essential for diagnosing and managing wrist instability and ligament injuries.

Key Diagnostic Findings

Current Gold Standard Treatment

• Non-Operative:
• Indicated for stable wrists without ligament disruption or minimal symptoms.
• Immobilization with a wrist splint or cast during acute injuries.
• Early controlled motion to prevent stiffness while protecting ligaments.

• Operative:
• Indicated for symptomatic carpal instability, confirmed ligament tears, or chronic pain and dysfunction.
• Arthroscopic or open repair/reconstruction of scapholunate and lunatotriquetral ligaments.
• In chronic cases, salvage procedures (e.g., proximal row carpectomy, partial wrist fusion) may be necessary.
• Early diagnosis and treatment improve functional outcomes and prevent degenerative arthritis.

Modern Complications & Outcomes

Board Exam Tip: Recognize the importance of the scapholunate angle (>60° indicates dorsal intercalated segment instability [DISI]) and the lunate’s position in diagnosing ligament injuries. Treatment aims to restore the kinetic chain to preserve pain-free function.

Classic Clinical Notes

Hand Anatomy 2

MOVEMENTS OF THE HAND AND WRIST

• No single articulation in the hand is an isolated mechanical entity – a mobile balance is achieved throughout the hand. The wrist influences the position of the MCP, which affects the position of the PIP, which in turn affects the DIP. The dynamic balance between antagonistic muscles forms the active influence on this “kinetic chain”, while the passive factors include the ligaments.

WRIST

• There are three primary movements – rotation, flexion/extension, and radial/ulnar deviation.

Pronation-Supination

• The radius rotates around a moving distal ulna, which rotates in the opposite direction; the axis of rotation is not fixed.

Flexion/Extension

• There is about 80° of flexion and about the same of extension – this represents rotation and gliding of the carpus on the distal radius.
• This motion is distributed between radiocarpal and midcarpal motion.

Radial/Ulnar Deviation

• There is physiological ulnar deviation at rest.
• There is about 40° of ulnar deviation, 15° of radial deviation, also distributed between the radiocarpal and midcarpal joints.

The Concept of “Variable Geometry” of the Proximal Carpal Row

• Radial deviation induces flexion of the scaphoid as the trapezium approaches the radius. Through the dorsal aspect of the scapholunate ligament, this motion is transmitted sequentially to the lunate and triquetrum, which flex approximately 25°.
• As the carpus ulnar deviates, the proximal row extends and supinates. The scaphoid can be observed to extend. The hamate migrates proximally, forcing the triquetrum to displace volarly and extend, bringing the lunate into extension, and hence the scaphoid.
• Thus, from the ulnar side, there is an extension moment on the lunate exerted by the triquetrum. From the radial side, there is a flexion moment on the lunate exerted by the scaphoid.

• If the scapholunate ligament is disrupted, the lunate, influenced by the triquetrum, will eventually adopt a more extended position with a scapholunate angle >60°, and will not flex with radial deviation.
• If the lunatotriquetral ligament is disrupted, the lunate, influenced by the scaphoid, will eventually adopt a more flexed position with a scapholunate angle.

Last Updated on January 24, 2026 by orthonet