Imaging features of hemimetameric shift in children: proposal of a new classification.

PURPOSE: To analyze the imaging findings of hemimetameric shift (HMMS) in children and propose a new classification system. METHODS: The clinical data and imaging studies of 85 HMMS patients aged 2 to 14 years were retrospectively reviewed. HMMS was classified as follows: type 1, two hemivertebrae (HV); type 2, three HV; type 3, four or more HV; and type 4, two or more HV and multiple spinal and/or costal anomalies. Inter- and intraobserver reliability of the classification system were evaluated using Fleiss' kappa coefficient. Imaging features of HMMS were analyzed using whole-spine standing radiographs, computed tomography and magnetic resonance imaging. RESULTS: HMMS was classified as type 1 in 54 patients, type 2 in 16, type 3 in eight, and type 4 in seven. The overall kappa value for the reliability study was 0.796, indicating that the classification system is simple and consistent. The cranial and caudal compensatory curves, coronal balance, thoracic kyphosis, and lumbar lordosis did not significantly differ between type 1 patients and patients with types 2-4 HMMS. Thoracolumbar kyphosis was significantly greater in patients with types 2-4. Discordant HMMS was found in 27 patients (31.8%). Its prevalence was significantly higher in patients with types 3 and 4 HMMS. Associated abnormalities were identified in 28 patients (32.9%). Their prevalence was significantly higher in patients with types 2-4 HMMS. CONCLUSIONS: Our proposed classification system is reliable and provides clear descriptions for various types of HMMS. Treatment of HMMS should be individualized because the clinical features vary among the different types.