Review Question - QID 211573

The patient has sustained a coronal shear capitellum fracture which requires open reduction and internal fixation (ORIF) through a lateral Kaplan approach, which can potentially cause a posterior interosseous nerve (PIN) palsy leading to inability to extend the thumb.

Capitellum fractures are classified with the Bryan and Morrey classification with coronal shear fractures falling under type IV injuries. The fragment contains the anterior aspect of the capitellum and a portion of the lateral trochlea. Good outcomes can be expected with an anatomic ORIF. Surgical exposure is typically through a lateral approach, such as the Kaplan interval between the extensor digitorum communis (EDC) and extensor carpi radialis brevis (ECRB). The PIN is at risk during the exposure, especially with forearm supination. For this reason, the arm is pronated throughout the exposure to decrease the risk of injury to the PIN.

McKee et al. performed a retrospective study of six patients treated for coronal shear fracture of the distal humerus. They reported each patient presented with a radiographic double-arc sign and each was managed with ORIF resulting in radiographic union at ~6 weeks. At the final follow-up, all patients had good to excellent functional outcomes with respect to the Broberg and Morrey classification.

Stamatis and Paxinos performed a retrospective study of five patients with type IV coronal shear fracture of the distal humerus treated with ORIF. The authors reported the latest follow-up to be 50 months with all fractures healing at 6-9 weeks follow-up with no signs of elbow instability. The authors concluded prompt recognition of this fracture is paramount to treatment success with good outcomes following anatomic ORIF.

Durakbasa et al. performed a retrospective study of 15 patients treated for coronal plane fracture of the distal humerus. They reported all patients were treated with ORIF with avascular necrosis, degenerative arthritis, and joint step-off occurring in 27%, 40%, and 40% of patients, respectively. They concluded type 1 and 2 fractures have excellent outcomes whereas type 3 fractures are at higher risk of developing complications including avascular necrosis, degenerative arthritis, and heterotopic ossification.

Cheung and Steinmann reviewed the surgical approaches to the elbow. They cautioned of placing the incision too anteriorly and distal extension of the Kaplan approach can increase the risk of injury to the PIN. The authors also recommended pronating the forearm to increase the distance from the PIN and the approach incision.

Figure A is the lateral radiograph of the right elbow with a "double-arc" sign consistent with a Bryan and Morrey Type IV capitellum fracture. Illustration A shows a schematic of the Bryan and Morrey capitellum fracture classification.

Incorrect Answers:
Answer 1: An ulnar nerve palsy is typically a complication from a medial approach to the elbow leading to loss of sensation in the ring and small fingers as well as intrinsic muscle weakness of the hand.
Answer 2: An anterior interosseous nerve (AIN) palsy would cause an inability to flex the thumb and index finger IP joints due to the loss of innervation to the FDS and FDP muscles. The AIN is not at risk with a lateral approach to the elbow.
Answer 4: A brachial artery injury can occur with an anterior approach to the antecubital fossa.
Answer 5: A laceration of the extensor indicis proprius tendon would occur with a distal approach to the forearm.