Spine J. 2014 Jan 30. pii: S1529-9430(14)00116-8. doi: 10.1016/j.spinee.2014.01.039. [Epub ahead of print]

Stokes OM, O’Donovan EJ, Samartzis D, Bow CH, Luk KD, Cheung KM.



Magnetically-controlled growing rod (MCGR) technology has been reported for the treatment of early- onset scoliosis (EOS). Such technology allows for regular and frequent outpatient rod distractions without the need for additional surgery. However, pre- and post-distraction spine radiographs are required to verify the amount of lengthening. This increased exposure to ionizing radiation in the developing child significantly increases their risk profile for radiation-induced cancer and non-cancerous morbidity.


This study addressed the first and novel application and reliability of the use of ultrasonography, which has no ionizing radiation exposure, as an alternative to plain radiographs in the visualizing and confirming of rod distractions.


A prospective study.


Six EOS patients who underwent surgical treatment with MCGRs were prospectively recruited.


Imaging measurements based on ultrasound and plain radiographs.


All patients were imaged via ultrasound, ease of rod identification was established and the reliability and reproducibility of optimal reference point selection assessed blindly by three individuals. The clinical algorithm, using ultrasound was subsequently implemented. Plain radiographs served as controls.


Assessment of the rod’s neck distance on ultrasound demonstrated a high degree of inter-rater reliability (a=0.99; p<0.001). Intra-rater reliability remained high on repeat measurements at different time intervals (a=1.00; p<0.001). Satisfactory inter-rater reliability was noted when measuring the rod's neck (a=0.73; p=0.010) and high reliability was noted in assessing the housing of the rod (a=0.85; p=0.01) on plain radiographs. Under blinded conditions 2mm rod distraction measured on radiographs corresponded to 1.7mm distraction on ultrasound (SD: 0.24mm; p<0.001). Subsequently the clinical algorithm using ultrasound, instead of radiographs, has been successfully implemented.


This is the first study to report the use of a novel technique using non-invasive, non-ionizing ultrasound to reliably document rod distractions in EOS patients. A high-level of inter- and intra-rater reliability was noted. More importantly, the use of ultrasonography may result in fewer whole spine radiographs from being taken in patients who have had MCGRs implanted for EOS; thereby decreasing their exposure to ionizing radiation and the potential risk of future radiation-induced diseases.

PMID: 24486476 [PubMed – as supplied by publisher]


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