Study design: Reliability study.
Objectives:To assess between-acquisition reliability of new multi-levels trunk cross-sections measurements, in order to define what is a real change when comparing two trunk surface acquisitions of a same patient, before and after surgery or throughout the clinical monitoring.Summary of background data: Several cross-sectional surface measurements have been proposed in the literature for non-invasive assessment of trunk deformity in patients with adolescent idiopathic scoliosis (AIS). However, only the maximum values along the trunk are evaluated and used for monitoring progression and assessing treatment outcome.
Methods:Back surface rotation (BSR), trunk rotation (TR) and coronal and sagittal trunk deviation are computed on 300 cross-sections of the trunk. Each set of 300 measures is represented as a single functional data using a set of basis functions. To evaluate betweenacquisition variability at all trunk levels, a test-retest reliability study is conducted on 35 AIS patients. A functional correlation analysis is also carried out to evaluate any redundancy between the measurements.Results: Each set of 300 measures was successfully described using only 10 basis functions.The test-retest reliability of the functional measurements is good to very good all over the trunk, except above the shoulders levels. The typical errors of measurement are between 1.20 and 2.2 for the rotational measures and between 2 to 6 mm for deviation measures. There is a very strong correlation between BSR and TR all over the trunk, a moderate correlation between coronal trunk deviation and both BSR and TR and no correlation between sagittal trunk deviation and any other measurement.
Conclusions:This novel representation of trunk surface measurements allows for a global assessment of trunk surface deformity. Multilevel trunk measurements provide a broader perspective of the trunk deformity and allow a reliable multi-level monitoring during clinical follow-up of patients with AIS and a reliable assessment of the esthetic outcome after surgery.
KEY WORDS:Scoliosis, multi-level trunk surface measurement, functional data analysis, reliability, correlation.
KEY POINTS:1) Trunk cross-sections measurements are reliable all along the trunk, except at the shoulders level.2) The maximum value of a measurement along the trunk overlooks the extent of the hump above and below the apex of the curve.
MINI ABSTRACT / PRÉCIS:This study assesses the reliability of multi-levels trunk cross-sections measurements and defines the difference needed between trunk surface acquisitions to detect a real progression and/or surgical correction of trunk surface deformity at all trunk levels.