[Instability and kyphosis following cervical laminectomy and occipital craniectomy in children (author's transl)].

The authors analyse the various factors of spinal instability and their respective importance in a series of 113 patients in which, either the occipital cerebellar pits or the cervical spine had been approached surgically. The essential cause was mechanical failure consecutive and related to the number of levels of laminectomies performed, even when the articular processes and their capsule were left intact. While craniectomy and ablation of the posterior arch of the Atlas was rarely, if ever, responsible for instability, the frequency rises to 25% once the Axis, the spinous processes and laminae have been removed. Instability was present in 80% of the cases in which three or more levels are involved. Moreover, cervical laminectomy was nearly always followed by instability, above all when the cervico-dorsal transitional zone was involved and even when only a small number of vertebral levels had been operated on. Location of the instability was always at the limit between the lowest level of laminectomy and the lover lying intact vertebra. Diagnosis has gone unrecognized until presently: the severity of the possible complications have led the authors to propose preventive surgical management. It this serie, an anterior vertebral bone graft was prefered. Consciousness of the risks involved should lead to better prevention, be it at the moment of neurosurgical surgery or in the follow-up period. However, preventive treatment creates several problems, which may only be solved by a currently undertaken prospective study.