MagneticallyControlled Growing Rods for Managing Scoliosis Does the

Magnetically-Controlled Growing Rods for Managing Scoliosis: Does the Law of Diminishing Returns Apply? Jason Pui Yin Cheung, Cora Bow, Dino Samartzis, Kenny Kwan Kenneth Man-Chee Cheung Department of Orthopaedics and Traumatology The University of Hong Kong

Disclosure • • • Jason Cheung Cora Bow Dino Samartzis Kenny Kwan Kenneth Cheung • • • None Research funds from Ellipse

• Traditional growing rods have reduced T 1 -S 1 length gain with each distraction procedure • Progressive stiffness • MCGR can allow smaller and more frequent distractions Aim: To assess whether the “law of diminishing returns” occurs in MCGR

Methods • EOS patients • Minimum 2 year follow-up • Monthly Out-patient Distractions (2 mm) • Spine/achieved length gain

Measured Distraction Length from Housing Unit Spinal Length Measurements T 1 -T 12 T 1 -S 1

RESULTS • Prospective case series of 7 EOS patients treated with MCGR. Demographics Female : Male 4: 3 Mean Age at implantation 10. 2 years (SD ± 3. 8) Mean Follow-up duration 3. 8 years (SD ± 1. 1) Mean number of distraction episode 31 (SD ± 13)

Largest Cobb Correction in Initial Surgery and Well. Maintained Throughout Distractions

Mean Gains in T 1 -S 1 Spinal Length Per 6 Monthly

Mean Gains in Achieved Distraction Length Per 6 Monthly

Conclusions • First study to analyse spinal length and distraction length gains with MCGR in EOS patients • No gradual reduction in gains observed • Clinicians must focus attention on distraction frequencies and its potential effect on spine length and growth