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Reliability of Rod Lengthening, Thoracic, and Spino-Pelvic Measurements on Biplanar Stereoradiography in Patients Treated With Magnetically Controlled Growing Rods

Obid, Peter, MD∗,†; Yiu, Karen Kar Lum, MSc; Cheung, Kenneth MC, MBBS, MD, FRCSEd, FHKCOS, FHKAM; Kwan, Kenny, FHKCOS, FHKAM, FRCSEd; Ruf, Michael, MD; Cheung, Jason Pui Yin, MBBS, MMedSc, MS, FHKCOS, FHKAM, FRCSEd

doi: 10.1097/BRS.0000000000002671

Study Design. Cross-sectional study.

Objective. To assess the inter- and intraobserver reliability of thoracic, spino-pelvic, and rod lengthening measurements made on biplanar spinal stereoradiography (EOS imaging) in children treated with magnetically controlled growing rod (MCGR).

Summary of Background Data. MCGR treatment aims to gain spine length while gradually correcting the spinal deformity. Monitoring thoracic and spino-pelvic parameters is crucial for successful management. EOS imaging is widely used for diagnosis and monitoring of children with Early Onset Scoliosis. However, there is a paucity of literature on the reliability of thoracic and spino-pelvic parameters on EOS imaging in children treated with MCGR.

Methods. Three independent reviewers independently read a random assortment of 20 whole spine posteroanterior and lateral radiographs from patients treated with MCGR. The measurements were repeated 4 weeks after the initial read. The following radiological parameters were measured: Cobb angle of the main and compensatory curves, coronal balance, coronal T1-S1 and T1-T12 length, chest width and depth at T6, pelvic inlet width, MCGR distracted lengths, global kyphosis, proximal and distal junctional angle, lordosis, sagittal balance, pelvic incidence, pelvic tilt and sacral slope. Statistical analysis was performed with paired t test and Cronbach alpha for inter- and intraobserver reliability.

Results. All measurements had good or excellent intra- and interobserver reliability (α>0.8; P < 0.05), except measurements of the proximal junctional angle which showed only poor intra- and interobserver reliability for patients with an upper instrumented vertebra cranial to T4.

Conclusion. EOS imaging is reliable for diagnosis and monitoring of children with Early Onset Scoliosis treated with MCGR. EOS imaging is particularly excellent for assessment of MCGR lengthening. Diagnosis and interpretation of early proximal junctional kyphosis within the cervicothoracic junction should be made with caution.

Level of Evidence: 3

Department of Orthopaedics and Traumatology, The University of Hong Kong, Pokfulam, Hong Kong SAR, China

Spine Center, SRH Klinikum Karlsbad-Langensteinbach, Karlsbad, Germany.

Address correspondence and reprint requests to Jason Pui Yin Cheung, MBBS, MMedSc, MS, FHKCOS, FHKAM, FRCSEd, Clinical Assistant Professor, Department of Orthopaedics and Traumatology, 5/F Professorial Block, Queen Mary Hospital, The University of Hong Kong Medical Centre, Pokfulam, Hong Kong SAR, China; E-mail:

Received 17 January, 2018

Revised 15 March, 2018

Accepted 22 March, 2018

The device(s)/drug(s) is/are FDA-approved or approved by corresponding national agency for this indication.

No funds were received in support of this work.

No relevant financial activities outside the submitted work.

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