The process of motion analysis.

<p>Optical markers were transferred into a point cloud. Relative motions were determined by manual labeling.</p

Literature comparison.

<p>Comparison of the ROM data evaluated in the present study, represented as mean values with standard deviations of the full ROM in each loading plane, with data extracted from the literature. The data of White and Panjabi [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0177823#pone.0177823.ref026" target="_blank">26</a>] are represented as mean values with value ranges.</p

The process of motion analysis.

<p>Optical markers were transferred into a point cloud. Relative motions were determined by manual labeling.</p

Experimental setup.

<p>A typical thoracic spinal motion segment before load application in the spine tester.</p

Lateral bending.

<p>ROM and NZ at ±7.5 Nm pure moment in lateral bending for all thoracic spinal motion segments (n = 6, except n = 7 for T4-T5 and T7-T8), represented as mean values with standard deviations.</p

The rib cage stabilizes the human thoracic spine: An <i>in vitro</i> study using stepwise reduction of rib cage structures

<div><p>The stabilizing effect of the rib cage on the human thoracic spine is still not sufficiently analyzed. For a better understanding of this effect as well as the calibration and validation of numerical models of the thoracic spine, experimental biomechanics data is required. This study aimed to determine (1) the stabilizing effect of the single rib cage structures on the human thoracic spine as well as the effect of the rib cage on (2) the flexibility of the single motion segments and (3) coupled motion behavior of the thoracic spine. Six human thoracic spine specimens including the entire rib cage were loaded quasi-statically with pure moments of ± 2 Nm in flexion/extension (FE), lateral bending (LB), and axial rotation (AR) using a custom-built spine tester. Motion analysis was performed using an optical motion tracking system during load application to determine range of motion (ROM) and neutral zone (NZ). Specimens were tested (1) in intact condition, (2) after removal of the intercostal muscles, (3) after median sternotomy, after removal of (4) the anterior rib cage up to the rib stumps, (5) the right sixth to eighth rib head, and (6) all rib heads. Significant (p < 0.05) increases of the ROM were found after dissecting the intercostal muscles (LB: + 22.4%, AR: + 22.6%), the anterior part of the rib cage (FE: + 21.1%, LB: + 10.9%, AR: + 72.5%), and all rib heads (AR: + 5.8%) relative to its previous condition. Compared to the intact condition, ROM and NZ increased significantly after removing the anterior part of the rib cage (FE: + 52.2%, + 45.6%; LB: + 42.0%, + 54.0%; AR: + 94.4%, + 187.8%). Median sternotomy (FE: + 11.9%, AR: + 21.9%) and partial costovertebral release (AR: + 11.7%) significantly increased the ROM relative to its previous condition. Removing the entire rib cage increased both monosegmental and coupled motion ROM, but did not alter the qualitative motion behavior. The rib cage has a strong effect on thoracic spine rigidity, especially in axial rotation by a factor of more than two, and should therefore be considered in clinical scenarios, in vitro, and in silico.</p></div

Load-deformation curves.

<p>Characteristic hysteresis curves of representative thoracic spinal motion segments of the upper, middle, and lower thoracic spine in flexion/extension, lateral bending, and axial rotation.</p

Flexion/extension.

<p>ROM and NZ at ±7.5 Nm pure moment in flexion/extension for all thoracic spinal motion segments (n = 6, except n = 7 for T4-T5 and T7-T8), represented as mean values with standard deviations.</p

Comparison of monosegmental ROM with literature data.

<p>Comparison of monosegmental ROM with literature data.</p

The experimental test setup.

<p>Pure moments of 2 Nm were applied in flexion/extension, lateral bending, and axial rotation using a custom-built spine tester [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0178733#pone.0178733.ref018" target="_blank">18</a>]. Motion analysis was performed using an optical motion tracking system with six cameras.</p