title: The use of ultrasound in comparison to radiography in magnetically controlled growth rod lengthening measurement: a prospective study.
abstract: OBJECTIVE
  This study investigated whether ultrasound (U/S) is an alternative to radiography when measuring magnetically controlled growth rod (MCGR) length in order to reduce radiation exposure. Distractible spinal growth rods are the gold standard when treating early-onset scoliosis (EOS).
  
  
  METHODS
  This was a prospective series. Patients were already undergoing EOS treatment using MCGRs. Forty-eight data points measured using radiography and U/S were compared. Each U/S data point was measured three times by three observers to assess intra- and inter-observer reliability. The radiation dose of the pre-lengthening and post-lengthening radiographs was recorded.
  
  
  RESULTS
  The average rod lengths were 1.322 cm with U/S and 1.329 cm with radiography. The ICC (radiography vs. U/S) was 0.992 (95 % confidence interval (CI) 0.976, 1.000). The inter- and intra-rater reliability of U/S had an ICC of 0.987 (95 % CI 0.966, 1.000) and 0.983 (95 % CI 0.956, 1.000), respectively. The mean total effective radiation dose of the pre-lengthening and post-lengthening PA spinal radiographs was 0.26 mSv with a mean attributable lifetime cancer risk of one in 39,686 per lengthening.
  
  
  CONCLUSIONS
  U/S highly agrees with radiography when measuring MCGR length. It has a high inter- and intra-observer reliability and does not require radiation exposure. Although U/S allows accurate MCGR measurement and soft tissue assessment, patients will still need occasional radiographs to assess spine bony elements, overall spinal balance and scoliosis correction. Combining radiography and U/S allows patient monitoring and accurate MCGR measurement whilst decreasing patients' radiation exposure.
authors.affiliation: The Royal National Orthopaedic Hospital, Brockley Hill, Stanmore, Middlesex, HA7 4LP, UK, wwyoon@mac.com.
authors.forename: Wai Weng
authors.initials: WW
authors.lastname: Yoon
authors.forename: Angela Christine
authors.initials: AC
authors.lastname: Chang
authors.forename: Philippa
authors.initials: P
authors.lastname: Tyler
authors.forename: Sajid
authors.initials: S
authors.lastname: Butt
authors.forename: Sameer
authors.initials: S
authors.lastname: Raniga
authors.forename: Hilali
authors.initials: H
authors.lastname: Noordeen
mesh_terms: D000293:Adolescent; D002648:Child; D005260:Female; D006801:Humans; D008280:Magnetics; D008297:Male; D009381:Neoplasms, Radiation-Induced / Q000517:prevention & control; D011446:Prospective Studies; D019736:Prostheses and Implants; D011829:Radiation Dosage; D011859:Radiography; D015203:Reproducibility of Results; D012600:Scoliosis / Q000000981:diagnostic imaging* / Q000601:surgery; D013131:Spine / Q000000981:diagnostic imaging*; D014463:Ultrasonography