A site for medical students - Practical,Theory,Osce Notes

Features of Posterior interosseous nerve injury

  • A lesion of the PIN causes weakness of finger extension (finger drop) without wrist drop.
  • The wrist deviates radially on extension due to weakness of the PIN innervated extensor carpi ulnaris  muscle with preservation of the main trunk innervated extensor carpi radialis longus muscle.
  • Some of the fingers may be affected more than others most often the ring and small fingers are selectively dropped, producing an abnormal posture which will  superficially resembles an  ulnar griffe (pseudoulnar claw hand).
  • Sometimes, cervical radiculomyelopathy will also selectively drop the ring and small fingers (Ono's hand, myelopathy hand, pseudopseudoulnar claw hand).
  • A PIN lesion is not associated with sensory changes.
  • Neuropathy of the superficial radial nerve will cause pain and alterations of sensation in its
  • distribution; it may be injured by tight bands around the wrist