Abstract
Aim:
The Magnetic Expansion Control Rod Device (Magec) allows controlled distraction of the immature spine for the treatment of early onset scoliosis. There disparity between the reported distraction on the external adjustment device (EAD) and true distraction achieved has not been commented on to date. This study aims to determine the disparity between ‘true’ (T) and ‘apparent’ (A) distraction. Our secondary aim was to assess truncal growth and development.
Methods:
Thirteen patients underwent an average of 4.4 (3–6) three monthly distractions. The amount of true distraction was determined by measuring the expansion gap on radiographs using the width of the rod as a conversion factor to allow for magnification. The total distraction to date was compared to the amount reported on the EAD. Sitting and standing heights were recorded at each distraction.
Results:
The average number of distractions was 4.4 (range 3–6). The average ‘true’ distraction was 9.1mm compared to 17.2mm ‘apparent’ distraction representing a TA ratio of 1:1.9. The average difference between the total distraction to date measured on the ERC and that measured radiographically was 8.3mm. Sitting and standing heights increased in all patients by an average of 4.3 cm and 7.8 cm per year.
Discussion:
The TA ratio of 1:1.9 suggests that for every unit of distraction registered on the EAD approximately 50% of true distraction occurs in vivo. Despite the difference in true versus apparent distraction, an increase in sitting and standing heights was observed in all patients sufficient to maintain growth and development.
Conflict Of Interest Statement: No conflict of interest.
