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In vitro analysis of the segmental flexibility of the thoracic spine.

ABSTRACT: Basic knowledge about the thoracic spinal flexibility is limited and to the authors' knowledge, no in vitro studies have examined the flexibility of every thoracic spinal segment under standardized experimental conditions using pure moments. In our in vitro study, 68 human thoracic functional spinal units including the costovertebral joints (at least n = 6 functional spinal units per segment from T1-T2 to T11-T12) were loaded with pure moments of ±7.5 Nm in flexion/extension, lateral bending, and axial rotation in a custom-built spine tester to analyze range of motion (ROM) and neutral zone (NZ). ROM and NZ showed symmetric motion behavior in all loading planes. In each loading direction, the segment T1-T2 exhibited the highest ROM. In flexion/extension, the whole thoracic region, with exception of T1-T2 (14°), had an average ROM between 6° and 8°. In lateral bending, the upper thoracic region (T1-T7) was, with an average ROM between 10° and 12°, more flexible than the lower thoracic region (T7-T12) with an average ROM between 8° and 9°. In axial rotation, the thoracic region offered the highest overall flexibility with an average ROM between 10° and 12° in the upper and middle thoracic spine (T1-T10) and between 7° and 8° in the lower thoracic spine (T10-T12), while a trend of continuous decrease of ROM could be observed in the lower thoracic region (T7-T12). Comparing these ROM values with those in literature, they agree that ROM is lowest in flexion/extension and highest in axial rotation, as well as decreasing in the lower segments in axial rotation. Differences were found in flexion/extension and lateral bending in the lower segments, where, in contrast to the literature, no increase of the ROM from superior to inferior segments was found. The data of this in vitro study could be used for the validation of numerical models and the design of further in vitro studies of the thoracic spine without the rib cage, the verification of animal models, as well as the interpretation of already published human in vitro data.

SUBMITTER: Wilke HJ

PROVIDER: S-EPMC5433776 | biostudies-literature | 2017

REPOSITORIES: biostudies-literature

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In vitro analysis of the segmental flexibility of the thoracic spine.

Wilke Hans-Joachim HJ Herkommer Andrea A Werner Karin K Liebsch Christian C

PloS one 20170516 5

Basic knowledge about the thoracic spinal flexibility is limited and to the authors' knowledge, no in vitro studies have examined the flexibility of every thoracic spinal segment under standardized experimental conditions using pure moments. In our in vitro study, 68 human thoracic functional spinal units including the costovertebral joints (at least n = 6 functional spinal units per segment from T1-T2 to T11-T12) were loaded with pure moments of ±7.5 Nm in flexion/extension, lateral bending, an ...[more]

PMID: 28520819

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Project description:The hydrostatic pressure of the nucleus pulposus represents an important parameter in the characterization of spinal biomechanics, affecting the segmental stability as well as the stress distribution across the anulus fibrosus and the endplates. For the development of experimental setups and the validation of numerical models of the spine, intradiscal pressure (IDP) values under defined boundary conditions are therefore essential. Due to the lack of data regarding the thoracic spine, the purpose of this in vitro study was to quantify the IDP of human thoracic spinal motion segments under pure moment loading. Thirty fresh-frozen functional spinal units from 19 donors, aged between 43 and 75 years, including all segmental levels from T1-T2 to T11-T12, were loaded up to 7.5 Nm in flexion/extension, lateral bending, and axial rotation. During loading, the IDP was measured using a flexible sensor tube, which was inserted into the nucleus pulposus under x-ray control. Pressure values were evaluated from third full loading cycles at 0.0, 2.5, 5.0, and 7.5 Nm in each motion direction. Highest IDP increase was found in flexion, being significantly (p < 0.05) increased compared to extension IDP. Median pressure values were lowest in lateral bending while exhibiting a large variation range. Flexion IDP was significantly increased in the upper compared to the mid- and lower thoracic spine, whereas extension IDP was significantly higher in the lower compared to the upper thoracic spine, both showing significant (p < 0.01) linear correlation with the segmental level at 7.5 Nm (flexion: r = -0.629, extension: r = 0.500). No significant effects of sex or age were detected, however trends toward higher IDP in specimens from female donors and decreasing IDP with increasing age, potentially caused by fibrotic degenerative changes in the nucleus pulposus tissue. Sagittal and transversal cuttings after testing revealed possible relationships between nucleus pulposus quality and pressure moment characteristics, overall leading to low or negative intrinsic IDP and non-linear pressure-moment behavior in case of fibrotic tissue alterations. In conclusion, this study provides insights into thoracic spinal IDP and offers a large dataset for the validation of numerical models of the thoracic spine.

Project description:BackgroundThe thoracic spine (TS) has been neglected in the study of the spine despite its essential role in the stability and posture of the entire spinal complex. Therefore, there is an inevitable need to investigate the reproducibility of different thoracic spinal posture measures used in subjects with TS pain.MethodsThirty-two subjects (16 females and 16 males, mean age 39 years) were evaluated by two physiotherapists on the same day to gauge inter-rater reliability and on two consecutive days to gauge intra-rater reliability. TS posture was assessed by observation, and thoracic spine mobility was measured by manual assessment of segmental flexion and extension mobility in a seated position. Additionally, posterior-to-anterior accessory mobility in a prone position was assessed manually. Moreover, cervicothoracic flexion in a seated position, thoracic posture, and thoracic flexion and extension mobility in a standing position were assessed with a tape measure, and flexion and extension mobility in a seated position and TS posture in seated and standing positions were measured with an inclinometer. The intraclass correlation coefficient (ICC), standard error of measurement (SEM), mean difference (MD), Bland-Altman (B&A) plot features and coefficient of repeatability (CR) were calculated.ResultsThe mean and standard deviation (SD) of the duration of TS pain was 22 (SD 45) months, with the intensity of pain being rated at 27 (SD 21) mm on a visual analogue scale (VAS). Intra-rater reliability was very strong (ICC ≥ 0.80) for the evaluation of seated and standing upper TS posture, standing whole TS posture and seated lower TS posture with an inclinometer. Moreover, TS posture evaluation with a measuring tape, posture inspection in a seated position, and manual assessment of segmental extension were found to have very strong intra-rater reliability. Inter-rater reliability was very strong for inclinometer measurements of standing and seated upper TS posture as well as standing whole TS posture.ConclusionIntra-rater reliability was higher than inter-rater reliability in most of the evaluated measurements. Overall, posture measurements with an inclinometer were more reliable than mobility measurements with the same instrument. The manual assessments can be used reliably when same evaluator performs the examination.Trial registrationClinical Trials, NCT01884818. Registered 24 June 2013, https://clinicaltrials.gov/ct2/show/NCT01884818?cond=thoracic+spine&cntry=FI&rank=1.

Project description: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.

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In vitro analysis of the segmental flexibility of the thoracic spine.

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In vitro analysis of the segmental flexibility of the thoracic spine.

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