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The Changing Position of the Center of Mass of the Thorax During Growth in Relation to Pre-existent Vertebral Rotation

de Reuver, Steven, BSc; Brink, Rob C., MD; Homans, Jelle F., MD; Kruyt, Moyo C., MD, PhD; van Stralen, Marijn, PhD; Schlösser, Tom P.C., MD, PhD; Castelein, René M., MD, PhD

doi: 10.1097/BRS.0000000000002927
BIOMECHANICS
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Study Design. Cross-sectional.

Objective. The aim of this study was to analyze the thoracic center of mass (COM) position of children at different ages and evaluate its relation with the previously reported pre-existent rotational pattern of the normal spine.

Summary of Background Data. The normal, nonscoliotic thoracic spine is known to have a rotational pattern that changes direction during growth, a transition from left-sided toward right-sided rotation with increasing age. This matches the changing curve convexity seen when idiopathic scoliosis develops at different ages. Furthermore, the direction of pre-existent rotation was shown to be related to organ orientation; in situs inversus the rotation is opposite to situs solitus.

Methods. Computed tomography (CT) scans of the thorax of infantile (0–4 years, n = 40), juvenile (4–10 years, n = 53), and adolescent (10–18 years, n = 62) children without spinal pathology were included from an existing database. The location of the COM inside the thorax was calculated based on Hounsfield-units, representing tissue mass. The COM offset was defined as the shortest distance to the midsagittal plane.

Results. At the infantile age, the COM was 2.5 ± 2.1 mm on the right side, at juvenile age not significantly deviated, and at adolescent age 3.1 ± 2.3 mm on the left side of the midsagittal plane. The mean COM offset correlated linearly with age (r = 0.77, P < 0.001).

Conclusion. The COM shifts from slightly on the right side of the thorax at the infantile age, to neutral at juvenile age, to the left at adolescent age. This corresponds to the earlier demonstrated change in direction of pre-existent rotation in the normal spine with age, as well as with the well-known changing direction, from left to right, of thoracic curve convexity in scoliosis at different ages.

Level of Evidence: N/ A

Semi-automatic computed tomography scan analysis of the thoracic center of mass location in children at different ages. This location shifts from the right side of the midsagittal plane toward the left during growth, which corresponds to known vertebral rotation of the normal spine and curve convexity in idiopathic scoliosis at different ages.

Department of Orthopaedic Surgery, University Medical Center Utrecht, Utrecht, The Netherlands

Imaging Division, University Medical Center Utrecht, Utrecht, The Netherlands.

Address correspondence and reprint requests to René M. Castelein, MD, PhD, Department of Orthopaedic Surgery, G05.228, University Medical Center Utrecht, P.O. Box 85500, 3508 GA Utrecht, The Netherlands; E-mail: r.m.castelein@umcutrecht.nl

Received 20 August, 2018

Revised 8 October, 2018

Accepted 17 October, 2018

The manuscript submitted does not contain information about medical device(s)/drug(s).

No funds were received in support of this work.

Relevant financial activities outside the submitted work: grants.

Copyright © 2018 Wolters Kluwer Health, Inc. All rights reserved.