An uncommon peripheral nerve injury after penetrating injury of the forearm: the importance of clinical examination.

A 22 year old woman presented to the accident and emergency department with a self inflicted stab wound to the radial side of the volar aspect of the left forearm caused by a pen knife. Her wounds were sutured on the day of injury. Over the course of next three weeks her wounds healed well but she noticed difficulty in using the hand. She therefore attended her general practitioner who suspected a possible nerve injury and referred the patient back to the A&E department. On follow up examination, she was noticed to have a loss of finger and thumb extension and weakness of thumb abduction. Active extension of the wrist (with radial deviation) was intact. There was no sensory deficit. Posterior interosseous nerve (PIN) palsy was diagnosed and the patient was referred to the regional hand surgery unit where she underwent exploration of the wound. A complete transection of the PIN in the supinator canal was found and repaired with good functional outcome. This case reflects the importance of clinical examination in uncommon peripheral nerve injuries and appropriate referral to a specialist department in case of doubtful penetrating wound that pose a threat to an underlying important structure.