Abstract
Introduction
Growing rods are used in the treatment of early-onset scoliosis. The aim of this technique is to achieve deformity correction while maintaining spinal growth. Gradual stiffening or spontaneous fusion of the spine can interfere with the ability to lengthen. Furthermore, diminished acquired length with serial distraction is common and needs to be evaluated and quantified. The purpose of this prospective study was to measure the forces and amount of distraction over time in patients with early-onset scoliosis treated with growing rods.
Methods
Distraction forces were measured prospectively during 60 consecutive lengthening procedures in 26 patients. All patients had single submuscular rod constructs with side-to-side connectors. For every measurement, output from a transducer on a dedicated pair of distraction calipers was recorded at zero load status, and the force was then recorded at every 1 mm lengthening; length was obtained at each event and was recorded in millimeters.
Results
The force required to distract the spine doubled at the fifth lengthening procedure (mean 368 N [SD 54]), and the distraction force was significantly higher at the fifth lengthening than at previous lengthening (p<0·01). Mean length achieved at each distraction decreased over time, such that by the fifth lengthening, 8mm or less was consistently achieved.
Conclusions
Distraction forces increase significantly after repeated lengthening of growing rod constructs, and the length obtained at each procedure decreases.
