Challenging the Conventional Standard for Thoracic Spine Range of Motion: A Systematic Review
Background: Segmental motion is a fundamental characteristic of the thoracic spine; however, studies of segmental ranges of motion have not been summarized or analyzed. The purpose of the present study was to present a summary of the literature on intact cadaveric thoracic spine segmental range of motion in each anatomical plane. Methods: A systematic MEDLINE search was performed with use of the terms "thoracic spine," "motion," and "cadaver." Reports that included data on the range of motion of intact thoracic human cadaveric spines were included. Independent variables included experimental details (e.g. specimen age) type of loading (e.g. pure moments) and applied moment. Dependent variables included the ranges of motion in flexion extension, lateral bending, and axial rotation. Results: Thirty three unique articles were identified and included. Twenty three applied pure moments to thoracic spine specimens, with applied moments ranging from 1.5 to 8 Nm. Estimated segmental range of motion pooled means ranged from 1.9deg to 3.8deg in flexion extension, from 2.1deg to 4.4deg in lateral bending, and from 2.4deg to 5.2deg in axial rotation. The sums of the range of motion pooled means (T1 to T12) were 28deg in flexion extension, 36deg in lateral bending, and 45deg in axial rotation. Conclusions: The pooled ranges of motion were similar to reported in vivo motions but were considerably smaller in magnitude than the frequently referenced values reported prior to the widespread use of biomechanical testing standards. Improved reporting of biomechanical testing methods, as well as specimen health, may be beneficial for improving on these estimations of segmental cadaveric thoracic spine range of motion.
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