[Injuries of the dens axis in childhood. Biomechanical analysis and surgical and conservative treatment of 2 cases].

Odontoid "fractures" in children are in fact typical lesions of the cartilaginous plate ("synchondrosis") separating the odontoid process from the body of the axis, 54 cases of which have been described in the literature so far. In our review we report about two 2-year-old children who were back-seat passengers restrained by four-point children's seat belts, in a car involved in a head-on motor vehicle accident. According to the accident research unit of our institution, trauma sustained in such circumstances is adequate for the causation of odontoid lesions in healthy children. Head-on collisions at a speed absorption of at least 40 km/h is described as a typical mechanism of such injury. Both children were immediately symptomatic, and the diagnosis was easily made from the X-rays. Neither child had neurologic deficits, which is in keeping with the literature, where neurologic injuries were found to have been reported exclusively in conjunction with head injuries. After closed reduction, conservative treatment was initiated in one child, in whom the extent of the anterior dislocation was smaller than the diameter of the odontoid shaft. In cases of major dislocation and more pronounced instability we recommend primarily open reduction and osteosynthesis with adequate implants. Our second case was treated with a halo fixator and a plaster vest for 12 weeks, but despite anatomic reduction there was no healing of the odontoid process. After temporary posterior fusion of C1/C2 we reamed the synchondrosis from an anterior approach and performed autogenous bone grafting. The posterior cerclage wire was removed after 5 months.(ABSTRACT TRUNCATED AT 250 WORDS)