Metaphyseal nonunion: a diagnostic dilemma

Abstract

Twenty-eight patients with metaphyseal nonunion were evaluated retrospectively. Initially, all patients were thought to have healing of their fractures. Mild pain and/or instability with weightbearing or discomfort localized around the hardware were common symptoms of this nonunion; however, substantial pain was not a predominant feature. In the majority of cases, routine roentgenograms were not helpful in establishing the diagnosis. Overlapping hardware made visualization difficult; furthermore, the presence of a callus gave a false impression of fracture healing. Tomograms were done in 13 patients, but were not helpful in four patients. Stress views and examination under fluoroscopy were reliable means of making this diagnosis, particularly around the knee region. It was done, however, only in a few patients. Subtle changes in the position of hardware or the position of the fragments are also an indication of failure of union. The average time from the initial injury to the diagnosis of nonunion was 36 weeks. Five patients whose pain was attributed to the hardware were found to have a nonunion intraoperatively at time of attempted hardware removal. In one patient, the nonunion was diagnosed during a quadricepsplasty. In two patients, the diagnosis was missed a second time following revision of fixation and bone grafting. Diagnosis of metaphyseal nonunion requires a high index of suspicion, because it occurs among all age groups. It is not as rare as previously described and poses many difficulties. The authors recommend the use of additional studies, including tomograms or stress views, oblique to establish difficult diagrams.