Abstract
BackgroundCurrent surgical treatment for adolescent idiopathic scoliosis (AIS) involves correction in both the coronal and sagittal plane, and thorough assessment of these parameters is essential for evaluation of surgical results. However, various definitions of thoracic kyphosis (TK) have been proposed, and the intra- and inter-rater reproducibility of these measures has not been determined. As such, the purpose of the current study was to determine the intra- and inter-rater reproducibility of several TK measurements used in the assessment of AIS.MethodsTwenty patients (90% females) surgically treated for AIS with alternate-level pedicle screw fixation were included in the study. Three raters independently evaluated pre- and postoperative standing lateral plain radiographs. For each radiograph, several definitions of TK were measured as well as L1–S1 and nonfixed lumbar lordosis. All variables were measured twice 14 days apart, and a mixed effects model was used to determine the repeatability coefficient (RC), which is a measure of the agreement between repeated measurements. Also, the intra- and inter-rater intra-class correlation coefficient (ICC) was determined as a measure of reliability.ResultsPreoperative median Cobb angle was 58° (range 41°–86°), and median surgical curve correction was 68% (range 49–87%). Overall intra-rater RC was highest for T2–T12 and nonfixed TK (11°) and lowest for T4–T12 and T5–T12 (8°). Inter-rater RC was highest for T1–T12, T1-nonfixed, and nonfixed TK (13°) and lowest for T5–T12 (9°). Agreement varied substantially between pre- and postoperative radiographs. Inter-rater ICC was highest for T4–T12 (0.92; 95% CI 0.88–0.95) and T5–T12 (0.92; 95% CI 0.88–0.95) and lowest for T1-nonfixed (0.80; 95% CI 0.72–0.88).ConclusionsConsiderable variation for all TK measurements was noted. Intra- and inter-rater reproducibility was best for T4–T12 and T5–T12. Future studies should consider adopting a relevant minimum difference as a limit for true change in TK.
Highlights
Current surgical treatment for adolescent idiopathic scoliosis (AIS) involves correction in both the coronal and sagittal plane, and thorough assessment of these parameters is essential for evaluation of surgical results
Intra- and inter-rater reproducibility was best for T4–T12 and T5–T12
The Lenke classification [11] is widely used in preoperative planning; classification of the sagittal thoracic modifier has shown poor reliability and the measurement agreement for T2–T12 and T5–T12 kyphosis have been found to be reduced compared to the frontal Cobb angle [12, 13]
Summary
Current surgical treatment for adolescent idiopathic scoliosis (AIS) involves correction in both the coronal and sagittal plane, and thorough assessment of these parameters is essential for evaluation of surgical results. Various definitions of thoracic kyphosis (TK) have been proposed, and the intra- and inter-rater reproducibility of these measures has not been determined. The purpose of the current study was to determine the intra- and inter-rater reproducibility of several TK measurements used in the assessment of AIS. Adolescent idiopathic scoliosis (AIS) is characterized by a lateral deviation of the spine in the coronal plane, vertebral rotation in the transverse plane, and often hypokyphosis in the sagittal plane [1, 2]. A few authors have suggested applying a nonfixed approach where limits of TK are based on the individual sagittal shape of the spine as it has been shown that the cranial and caudal end vertebrae of the nonfixed TK vary among normal adolescents [8, 21,22,23]
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