The Fluoroscopic Technique for Monitoring Distraction of a Non-Invasive Lengthening Device in Early Onset Scoliosis

Prospective non-randomised.

To evaluate radiation exposure using fluoroscopy compared to x-rays in the monitoring of a growing rod system.

The integrity of implants in the treatment of early onset scoliosis (EOS) is usually monitored with repeated plain x-rays. The cumulative dosage of ionizing radiation may be high. Children are highly sensitive to the carcinogenic effects of radiation and have a longer life span in which to reflect this risk. Fluoroscopy is commonly used to obtain focused images in other areas of orthopaedics. It has the advantage of less radiation intensity due to flash exposure. We have used fluoroscopy to monitor the lengthening of a non-invasive growing rod system in the treatment of EOS. We report on the results.

The technique was initially refined in vitro by performing an audit in which 10 radiographers screened a phantom spine (Plastic dummy) with an implanted non - invasive growing rod device. Pulse rate setting was 3. Average exposure time was 0.01 seconds. Average radiation dose was 0.04 μGym2. A plain x-ray of the same phantom spine yielded a radiation dose of 0.5 μGym2.

Radiation exposure using fluoroscopy was compared to that received using plain radiographs in ten consecutive patients treated for EOS. There were 8 males and 2 females. Average age 5.2 years.

Mean radiation exposure using fluoroscopy was 0.0046 mSv compared to an average radiation exposure of 0.115 mSv using standard x-rays (p<0.003). Mean cancer induction risk was calculated to potentially reduce from 1:225,000 to 1:4.9 million.

We would recommend fluoroscopy as a useful technique to monitor the lengthening of a non-invasive growing rod system due to the significantly smaller radiation exposure.