Abstract
Introduction
There is an unresolved controversy in the published work about the effect of screws crossing the neuro-central cartilage (NCC) on spinal canal dimension in very young children and in animals. Anterior vertebral body screws with fusion can invade and damage the NCC, especially at the site of screw insertion; however, this finding has never been studied.
Methods
This study is a retrospective, clinical and radiological analysis of seven consecutive children aged 1–2 years treated with anterior vertebral instrumentation and fusion by downsized rod screw systems. The mean age at time of surgery was 2 years 4 months (range 1 year 9 months to 2 years 10 months). The average follow-up period was 3 years 3 months (2 years 6 months to 4 years 5 months). 16 screws inserted anteriorely were evaluated by a follow-up CT scan. Spinal canals were divided with known anatomical landmarks into right and left hemicanals. The relation of the anterior screws to the NCC and the spinal canal dimension were studied. All clinical and radiological complications were recorded.
Results
Only 11 screws were suitable for measurement. There was a difference of 10–20% between the surface areas of the two hemicanals in six levels in which the screw heads were passing through or encroaching on the NCC; the canal was smaller ipsilateral to the affected NCC. The hemicanals were almost symmetrical in five levels in which the screw heads were away from the NCC, except in one in which it was touching the NCC. For the 16 screws evaluated there were no recorded complications apart from one screw breaching the adjacent end plate.
Conclusions
Anterior vertebral body screws with fusion can encroach on the NCC when inserted in very young children, which seems to decrease the ipsilateral canal dimension between 10% and 20%. Apart from this finding, anterior instrumentation is safe when used in very young children aged 1–2 years. Canal asymmetry had no clinical effect in childhood; however, long-term follow-up of these children is needed to measure its clinical significance. Change of screw position with time is a frequent occurrence in the distal pedicle screws with single growing rods. There are two different types identified. With growing rods some degree of distal pedicle screw migration in this paediatric age group may not be regarded as a complication of treatment.
