Review Question - QID 218560

The posterior interosseous nerve (PIN) was injured either from the initial injury or by the k-wire placed intra-operatively. As a branch of the radial nerve, the PIN wraps around the radial neck, and its injury results in the loss of function of the extensor pollicis longus muscle (as well as partial loss of wrist and loss of other digits extension).

Closed radial head and neck fractures sustained in the pediatric population often require treatment with closed reduction. There are various classifications of these injuries, however, all agree that pediatric radial head/neck fractures with <30 degrees of angulation (or less than 30 degrees of angulation after closed reduction) may be treated non-operatively. If closed reduction attempts are unsuccessful, patients require operative management with closed versus open reduction and percutaneous pinning. During the approach, the patient’s arm should be held in pronation in order to move the PIN away from the site of insertion of the k-wire.

Nicholson and Skaggs provided a comprehensive review of proximal radius fractures in the pediatric population. They reviewed the mechanism of injury and anatomic considerations, classification systems, and treatment protocols for these types of fractures. They emphasize that radial neck fractures should be considered sentinel injuries because concomitant injuries occur in 30-50% of patients. The most commonly encountered concomitant injuries include elbow dislocations, medial epicondyle fractures, and olecranon fractures.

Watkins and colleagues described a case series of 8 pediatric patients with displaced radial neck fractures treated using a minimally invasive technique. They describe utilizing blunt curved forceps to perform the percutaneous reduction of the radial neck followed by the advancement of a flexible intramedullary nail retrograde into the radial head in order to maintain the reduction. While the authors report a need for subsequent hardware removal, they concluded this method to be an effective operative technique for treating displaced radial neck fractures.

Figure A shows a right-sided radial neck fracture with > 30 degrees of angulation. Figure B shows intra-operative fluoroscopic imaging after percutaneous reduction and pinning of the radial neck. Figure C shows an unlabeled brachial plexus anatomy diagram. Illustration A shows the labeled branches of the brachial plexus anatomy diagram.

Incorrect Answers:
Answer 1: The brachial plexus branch labeled “A” is the musculocutaneous nerve that provides motor function to the biceps and partial motor function to the brachialis muscle (which has additional motor innervation by the radial nerve).
Answer 2: The brachial plexus branch labeled “B” is the axillary nerve that provides motor function to the deltoid and teres minor muscles.
Answer 4: The brachial plexus branch labeled “D” is the median nerve that provides motor function to all wrist flexion muscles (with exception of flexor carpi ulnaris and the ulnar ½ of the flexor digitorum profundus muscles). It also provides motor innervation to a large portion of the thenar musculature including the opponens pollicis, abductor pollicis brevis, and the flexor pollicis brevis.
Answer 5: The brachial plexus branch labeled “E” is the ulnar nerve that provides motor function to some forearm flexion muscles (flexor carpi ulnar and the ulnar ½ of the flexor digitorum profundus muscles) and the hand hypothenar and intrinsic musculature.