Remodeling Capacity of Malunited Odontoid Process Fractures in Kyphotic Angulation in Infancy

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A retrospective case study. To confirm the remodeling potential of the kyphotic malunited odontoid fracture in the pediatric spine. Nonsurgical reduction and immobilization is the gold standard for the odontoid fracture in infancy. However, the reduction occasionally results in incomplete repositioning of the odontoid process. The cervical spine is subsequently immobilized until fusion in most cases in the hope of achieving remodeling with the growth of the remaining displacement and kyphotic angulation, although there are no precise data on the acceptable limit of the deformity. Three patients (age at injury = 1 year 2 months to 3 years) with odontoid process fracture in infancy were treated conservatively and the fractures were observed on plain lateral radiographs until at least the age of 20 years. For evaluation of the angulated odontoid process, we used our original measurement method of the odontoid process tilting angle (OPTA). In addition, the OPTAs were also measured in 127 Japanese adult patients (57 male patients and 70 female patients; average age = 43 years) without a history of odontoid fracture, as normal controls. The OPTA in the normal controls was -21.4° ± 23.3°. The OPTAs ranged from 41° to 62° at the initial evaluation, from 12° to 30° at the time of bony union, and from -4° to -14° at the final follow-up at more than 20 years of age, which were all within one standard deviation of the mean in the normal adult controls. Angulated odontoid fractures with the OPTA around 30° at the time of bony union in infants younger than 3 years of age could have the capacity for remodeling to the normal morphology. No surgical reduction might be needed to recommend complete apposition of the odontoid process in the absence of severe or deteriorating neural impairment.