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High Correlation Between Achieved and Expected Distraction Using Magnetically Controlled Growth Rods (MCGR) With Rib to Pelvis Fixation in Pediatric Spine Deformity

Lorenz, Heiko M., MD; Braunschweig, Lena, PhD; Badwan, Batoul, MS; Groenefeld, Katharina, DDS; Hecker, Marina M., MS; Tsaknakis, Konstantinos, MD; Grote, Jasmin, MD; Hell, Anna K., MD

Journal of Pediatric Orthopaedics: May/June 2019 - Volume 39 - Issue 5 - p e334–e338
doi: 10.1097/BPO.0000000000001303
Spine
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Purpose: Magnetically controlled implant systems have been established to treat severe progressive spinal deformity in children. The purpose of this study was to evaluate (1) the ratio between achieved and expected distraction length, (2) the complication rate and its risk factors as well as (3) the correlation of the distraction length and the length of the spine.

Methods: A total of 40 patients with an average follow-up of 34 (14 to 57) months were prospectively included in the study. Children underwent lengthening procedures every three months. The ratio between the distraction lengths was determined by comparing the measured distraction length of the rod on radiographs with the distraction length displayed on the external remote controller for the magnetically controlled growing rod (MCGR). Age, weight, height, and complications were repeatedly recorded.

Results: The analysis of 746 procedures showed the actual distraction to be 94.4% of the expected one. No difference between implants on the concave and convex spinal side was observed. The overall complication rate was 4.6% mainly because of failure of the implant or lack of implant extension, which was directly related to an increased BMI. There was also a strong correlation between achieved implant distraction length and gain in spinal length.

Conclusions: Our study demonstrates a high ratio (0.94) between achieved and expected distraction length of magnetically controlled spinal rods. The complication rate was low (4.6%) and correlated to a high BMI. The correlation between the achieved implant distraction length and spinal length indicates the efficiency of the MCGR therapy.

Level of Evidence: Therapeutic Level IV.

Department of Trauma, Orthopaedic and Plastic Surgery, University Medical Center Goettingen, Goettingen, Germany

Informed consent was obtained from all individual participants included in the study.

The authors declare no conflicts of interest.

Reprints: Anna K. Hell, MD, Pediatric Orthopaedics; Department of Trauma, Orthopaedic and Plastic Surgery, University Medical Center Goettingen; 37075 Goettingen, Germany. E-mail: anna.hell@med.uni-goettingen.de.

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