Ulnar fracture with late radial head dislocation: delayed Monteggia fracture.

Monteggia fractures are rare but commonly discussed lesions, with increasing complications due to late diagnosis. This article describes a case of a Monteggia fracture with delayed dislocation of the radial head. Previous radiographs of a 2-year 8-month-old boy show complete fracture of the distal ulna, with no radial head dislocation. The radial head remained well positioned after 4 weeks. Seven years later, he sustained another arm injury. He was diagnosed with a hematoma but was later believed to have nursemaid's elbow. He presented to our institution 5 weeks after the injury, and the radial head was found to be chronically dislocated, indicating a displacement occurring sometime during the past 7 years. After failing conservative treatment, the patient underwent surgical repair. The annular ligament was reconstructed using a harvested triceps fascia band, and an ulnar osteotomy was performed. A review of the literature found few reports of delayed Monteggia fractures, which accounted the delayed dislocations to ulnar angulation. However, our patient showed minimal ulnar angular deformity. We propose that the initial fracture disrupted the annular ligament and the radial head spontaneously relocated prior to being seen, which put the radial head at risk for later dislocation. We present an alternative hypothesis of dislocation after fracture healing and report the longest known period of delay between fracture and dislocation.