• Yoshihiko Satake, Yuji Tomori, Takuya Sawaizumi, Mitsuhiko Nanno, Norie Kodera, and Shinro Takai.
• Department of Orthopaedic Surgery, Nippon Medical School.
• J Nippon Med Sch. 2018 Jan 1; 85 (1): 60-65.

AbstractMedial epicondyle fractures of the humerus account for 11%-20% of all elbow injuries in children. Although intra-articular incarceration of the medial epicondyle occurs in 5%-18% of medial epicondyle fractures associated with an elbow dislocation, the mechanism of intrusion of the fracture fragment is unknown. We report a case of an irreducible elbow fracture and dislocation due to incarceration of the medial epicondyle fragment of the humerus, classified as a Watson-Jones type 3 fracture of the medial epicondyle, and present the mechanism of the intra-articular incarceration of the medial epicondyle fragment. The patient was a 9-year-old boy who injured his right elbow in a fall, and was diagnosed with a Watson-Jones type 3 fracture of the medial epicondyle. As we could not achieve a good reduction under fluoroscopic imaging, surgery was immediately performed using a medial approach. We discovered that the incarcerated fracture fragment was attached to the flexor-pronator muscles, the medical collateral ligament (MCL), and the anterior articular capsule. The medial epicondyle was fixed with Kirschner-wires augmented with tension band wiring. After fixation, there was no remaining instability. After 4 months the patient's fracture had proceeded to union and the internal fixation was removed. After 30 months he was asymptomatic and able to perform all of his daily life activities without any limitation. Our case, a Watson-Jones type 3 medial epicondyle fracture, is suggestive of the mechanism of incarceration of the medial epicondyle fragment into the elbow joint. Our findings support the idea that the attachment of both the MCL and the articular capsule can result in the entrapment of a fracture fragment in the elbow joint.

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