Reducing radiation exposure in early-onset scoliosis surgery patients: novel use of ultrasonography to measure lengthening in magnetically-controlled growing rods.
BACKGROUND
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 postdistraction spine radiographs are required to verify the amount of lengthening. This increased exposure to ionizing radiation in developing children significantly increases their risk profile for radiation-induced cancer and noncancerous morbidity.


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


METHODS
A prospective study.


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


METHODS
Imaging measurements based on ultrasound and plain radiographs.


METHODS
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.


RESULTS
Assessment of the rod's neck distance on ultrasound demonstrated a high degree of interrater reliability (a=0.99; p<.001). Intrarater reliability remained high on repeat measurements at different time intervals (a=1.00; p<.001). Satisfactory interrater reliability was noted when measuring the rod's neck (a=0.73; p=.010) and high reliability was noted in assessing the housing of the rod (a=0.85; p=.01) on plain radiographs. Under blinded conditions, 2 mm rod distraction measured on radiographs corresponded to 1.7 mm distraction on the ultrasound (standard deviation: 0.24 mm; p<.001). Subsequently, the clinical algorithm using ultrasound, instead of radiographs, has been successfully implemented.


CONCLUSIONS
This is the first study to report the use of a novel technique using noninvasive, nonionizing ultrasound to reliably document rod distractions in EOS patients. A high level of inter- and intrarater reliabilities were 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.
Division of Spine Surgery, Department of Orthopaedics and Traumatology, Duchess of Kent Children's Hospital, University of Hong Kong, 12 Sandy Bay Rd, Pokfulam, Hong Kong, SAR China.
Oliver M
OM
Stokes
Division of Spine Surgery, Department of Orthopaedics and Traumatology, Duchess of Kent Children's Hospital, University of Hong Kong, 12 Sandy Bay Rd, Pokfulam, Hong Kong, SAR China.
Elizabeth J
EJ
O'Donovan
Division of Spine Surgery, Department of Orthopaedics and Traumatology, Duchess of Kent Children's Hospital, University of Hong Kong, 12 Sandy Bay Rd, Pokfulam, Hong Kong, SAR China.
Dino
D
Samartzis
Division of Spine Surgery, Department of Orthopaedics and Traumatology, Duchess of Kent Children's Hospital, University of Hong Kong, 12 Sandy Bay Rd, Pokfulam, Hong Kong, SAR China.
Cora H
CH
Bow
Division of Spine Surgery, Department of Orthopaedics and Traumatology, Duchess of Kent Children's Hospital, University of Hong Kong, 12 Sandy Bay Rd, Pokfulam, Hong Kong, SAR China.
Keith D K
KD
Luk
Division of Spine Surgery, Department of Orthopaedics and Traumatology, Duchess of Kent Children's Hospital, University of Hong Kong, 12 Sandy Bay Rd, Pokfulam, Hong Kong, SAR China. Electronic address: cheungmc@hku.hk.
Kenneth M C
KM
Cheung
D000293:Adolescent; D000465:Algorithms; D002648:Child; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D008280:Magnetics; D008297:Male; D009381:Neoplasms, Radiation-Induced / Q000517:prevention & control*; D015588:Observer Variation; D011446:Prospective Studies; D019736:Prostheses and Implants; D011829:Radiation Dosage; D011859:Radiography / Q000379:methods; D015203:Reproducibility of Results; D012307:Risk Factors; D012600:Scoliosis / Q000000981:diagnostic imaging* / Q000601:surgery*; D013131:Spine / Q000000981:diagnostic imaging* / Q000601:surgery*; D014463:Ultrasonography / Q000379:methods
Early-onset; Growing rod; Level II diagnostic study; Magnetic; Radiation; Scoliosis; Ultrasound