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A 9-year-old boy with elbow injury
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A 9-year-old boy fell from his bicycle onto his outstretched right hand. He had immediate pain and deformity at his elbow. He was seen at an outside hospital where, under conscious sedation, closed reduction for a right elbow dislocation was performed. Post-reduction anterior posterior and lateral elbow radiographs are shown in Figure 1. The patient was referred to our emergency department for further evaluation and management. He had mild weakness in the ulnar nerve distribution.
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Images: Parikh SN
Incarcerated medial epicondyle fracture fragment
Elbow injury is the most common injury encountered in the pediatric trauma unit. Medial epicondyle fractures represent up to 20% of all pediatric elbow fractures, and elbow dislocation constitutes 3% to 6% of all elbow injuries. In skeletally immature patients nearing adolescence, elbow dislocations are often associated with medial epicondyle avulsion fracture. In 15% to 25% of cases, the medial epicondyle gets incarcerated in the ulnohumeral joint. Overall, 75% of medial epicondyle fractures occur in boys most commonly between 9 years and 14 years of age. Incarcerated medial epicondyle fracture, being a less common injury, could be missed with catastrophic results. A missed incarcerated medial epicondyle fracture can result in late complications like pain, elbow instability, ulnar neuropathy, joint destruction, arthritis and loss of range of motion (ROM).
Diagnosis
To make the diagnosis, understanding of the normal developmental anatomy of the elbow is helpful. Remembering the pneumonic “CRITOE” helps to memorize the sequence of appearance of ossification centers around elbow where ‘C’ stands for capitellum (appearance age 1 year to 2 years), ‘R’ for radial head (appearance age 2 years to 4 years), ‘I’ for internal or medial epicondyle (appearance age 4 years to 6 years), ‘T’ for trochlea (appearance age 8 years to 11 years), ‘O’ for olecranon (appearance age 9 years to 11 years) and ‘E’ for external or lateral epicondyle (appearance age 10 years to 11 years). The medial epicondyle is the last secondary ossification center to fuse to the distal humerus at the age of 15 years and hence, these injuries are seldom seen in adults.
As the entrapped medial epicondyle is positioned just distal to the medial side of the distal humeral metaphysis, it may be misinterpreted as the ossification center for the trochlea. However, with the knowledge of the sequence of appearance of ossification centers, the trochlea starts ossification after the medial epicondyle. Therefore, the trochlea should not be seen unless the medial epicondyle is identified as well. If the medial epicondyle is not seen in its expected location and a single ossicle is seen beneath the medial aspect of the distal humeral metaphysis, the ossicle should be interpreted as an avulsed medial epicondyle that is entrapped in the joint rather than a normal trochlea. Moreover, usually the trochlea initially appears as multiple fragmented ossification centers; in contrast, the medial epicondyle has a smooth and regular appearance.
Medial epicondyle apophysis
The medial epicondyle apophysis is located on the posteromedial aspect of the distal humerus. It serves as an attachment site for ulnar collateral ligament and the flexor-pronator common tendon origin. Due to these attachments, the common direction of displacement for medial epicondyle fracture is anterior. This anterior direction of displacement of the displaced fragment of the medial epicondyle makes it difficult to visualize the fragment on an AP radiograph. The lateral view, which should be ideal to assess anterior displacement, is also limited due to the overlap of the fragment with the intact distal humerus.
If at any time the epicondyle appears at the level of joint, it should be considered to be incarcerated until proven otherwise. A persistent subluxation of the elbow joint or incongruous reduction should raise the suspicion of an incarcerated medial epicondyle fragment. Special radiographic projections, including internal rotation view of the elbow, a newly described axial distal humerus view or CT scan, can help assess the displacement of the fragment. Comparison radiograph of the normal elbow may also help to diagnose the condition (Figure 2).
The presence of an incarcerated medial epicondyle is an absolute indication for operative reduction to restore the normal anatomy of the elbow joint. Internal fixation would allow for early mobilization which would help to prevent elbow stiffness. Various modalities have been reported to try to dislodge the fragment from the joint, such as inflation of the joint with air, various positioning maneuvers or the use of nerve stimulation to stimulate the flexor group of forearm muscles. However, open reduction and internal fixation (ORIF) remains the standard of care for an incarcerated medial epicondyle fracture. Internal fixation options include suture repair, K-wire fixation, screw fixation, excision of medial epicondyle fragment and resuturing of the soft tissue to periosteum. Internal fixation with a screw remains the most acceptable fixation option for these fractures.
Treatment
ORIF of the medial epicondyle fracture with a 4-mm cancellous cannulated screw was performed through a posteromedial approach, with the patient supine and under general anesthesia (Figure 3). The ulnar nerve was identified, but not transposed during surgery. The entrapped fragment was removed from the joint without disruption of the attached soft tissues. The reduction of the fragment to its bed could be facilitated by wrist flexion, elbow flexion and forearm supination. Tentative fixation was achieved using smooth K-wires, which also can be used to joystick the fracture fragment into position. The reduction could be confirmed by fluoroscopy and by the visual and palpable restoration of the smooth metaphyseal curve of the distal humerus along the superior aspect of the fracture fragment. The screw need not be bicortical; fixation in the medial column or in the dense bone above the olecranon fossa is sufficient for compression and rigid fixation. The elbow was checked for ligamentous stability after fixation of the fracture fragment.
Postoperatively, range of motion was started after 10 days once pain subsided and the incision healed. At 3-months follow-up, the ulnar neuropraxia had resolved and full ROM was obtained. The screw is not removed routinely, unless there is symptomatic irritation around the hardware.
- References:
- Dodds SD, et al. J Hand Surg Am. 2014;doi:10.1016/j.jhsa.2014.06.012.
- Gottschalk HP, et al. J Am Acad Orthop Surg. 2012;doi:10.5435/JAAOS-20-04-223.
- For more information:
- Raman K. Shrivastava, MBBS, DOrth, DNB, can be reached at V.Y. Hospital, Raipur, Chhattisgarh, India; email: dr_rksin@yahoo.co.in.
- Shital N. Parikh, MD, can be reached at the Division of Orthopaedic Surgery, Cincinnati Children’s Hospital Medical Center, 3333 Burnet Ave., Cincinnati, OH 45229; email: shital.parikh@cchmc.org.
Disclosures: Shrivastava and Parikh report no relevant financial disclosures.