Distortions of the Hand / Claw Hand

Snapshot

• A 32-year-old woman presents to the emergency room with severe right arm pain after being involved in a motor vehicle collision. She has a comminuted open fracture of the right distal radius and ulna. She is taken to the operating room where lesions to the distal ulnar artery and nerve are noted. She undergoes multiple surgical procedures over the following several months until her radius and ulna appear well healed. However, she has residual hand weakness and is unable to completely open her hand after making a fist. On exam, her 4th and 5th metacarpophalangeal joints are hyperextended while her 4th and 5th interphalangeal joints are flexed. 

Introduction

• Lesions to different nerves of the upper extremity will lead to specific hand distortions
  • ulnar claw hand
  • hand of benediction
  • Klumpke total claw hand
• Relevant anatomy
  • muscles
    • lumbricals
      • innervation
        • 2nd/3rd digit lumbricals innervated by median nerve
        • 4th/5th digit lumbricals innervated by ulnar nerve
      • actions
        • metacarpophalangeal (MCP) joint flexion
        • proximal interphalangeal (PIP) and distal interphalangeal (DIP) joint extension
    • extensor digitorum communis (EDC) 
      • innervation
        • posterior interosseous nerve (branch of the radial nerve)
      • actions
        • finger extension
    • flexor digitorum superficialis (FDS)
      • innervation
        • anterior interosseous nerve
      • actions
        • PIP flexion
    • flexor digitorum profundus (FDP)
      • innervation
        • 2nd/3rd digits innervated by anterior interosseous nerve (branch of the median nerve)
        • 4th/5th digits innervated by ulnar nerve
      • actions
        • DIP flexion
    • dorsal and palmar interossei
      • innervation
        • ulnar nerve
      • actions
        • dorsal interossei abduct the fingers
        • palmar interossei adduct the fingers
    • thenar eminence musculature
      • muscles
        • flexor pollicis brevis
        • abductor pollicis brevis
        • opponens pollicis
      • innervation
        • recurrent branch of median nerve
        • flexor pollicis brevis also receives its innervation from the ulnar nerve
      • actions
• thumb flexion, abduction, and opposition

Ulnar Claw Hand

• Physical exam  
  • 4th and 5th MCP joints are extended
  • 4th and 5th PIP and DIP joints are flexed
  • weakness in finger abduction and adduction
  • patient is able to make a fist but is not able to completely open their 4th and 5th digits
• Pathoanatomy
  • nerve involved
    • distal ulnar nerve (at the wrist)
  • muscles involved
    • weakened 4th and 5th lumbricals
• weakened dorsal and palmar interossei

Hand of Benediction

• Physical exam 
  • 2nd and 3rd MCP, PIP, and DIP joints are extended
  • weakness in thumb abduction and opposition
  • patient cannot make a fist due to inability to flex 2nd and 3rd digits
• Pathoanatomy
  • nerve involved
    • median nerve at the forearm or elbow
  • muscles involved
    • weakened 2nd and 3rd lumbricals
    • weakened FDP to 2nd and 3rd digits
• weakened thenar musculature

Klumpke Total Claw Hand

• Physical exam 
  • MCP joints are hyperextended
  • PIP and DIP joints are flexed
  • wrist is hyperextended
  • weakness in thumb abduction and opposition
  • forearm is supinated
• Pathoanatomy
  • nerve involved
    • lower trunk of the brachial plexus (C8/T1)
  • muscles involved
    • all intrinsic muscles of the hand
      • lumbricals
      • dorsal and palmar interossei
      • thenar eminence
    • wrist flexors
    • forearm pronators