Quantifying lung and diaphragm morphology using radiographs in normative pediatric subjects, and predicting CT-derived lung volume

In vitro coupled motions of the whole human thoracic and lumbar spine with rib cage

Study design

In vitro biomechanical study investigating the coupled motions of the whole normative human thoracic spine (TS) and lumbar spine (LS) with rib cage.

Objective

To quantify the region-specific coupled motion patterns and magnitudes of the TS, thoracolumbar junction (TLJ), and LS simultaneously.

Background

Studying spinal coupled motions is important in understanding the development of complex spinal deformities and providing data for validating computational models. However, coupled motion patterns reported in vitro are controversial, and no quantitative data on region-specific coupled motions of the whole human TS and LS are available.

Methods

Pure, unconstrained bending moments of 8 Nm were applied to seven fresh-frozen human cadaveric TS and LS specimens (mean age: 70.3 ± 11.3 years) with rib cages to elicit flexion-extension (FE), lateral bending (LB), and axial rotation (AR). During each primary motion, region-specific rotational range of motion (ROM) data were captured.

Results

No statistically significant, consistent coupled motion patterns were observed during primary FE. During primary LB, there was significant (p < 0.05) ipsilateral AR in the TS and a general pattern of contralateral coupled AR in the TLJ and LS. There was also a tendency for the TS to extend and the LS to flex. During primary AR, significant coupled LB was ipsilateral in the TS and contralateral in both the TLJ and LS. Significant coupled flexion in the LS was also observed. Coupled LB and AR ROMs were not significantly different between the TS and LS or from one another.

Conclusions

The findings support evidence of consistent coupled motion patterns of the TS and LS during LB and AR. These novel data may serve as reference for computational model validations and future in vitro studies investigating spinal deformities and implants.

Patient-specific finite element modeling of scoliotic curve progression using region-specific stress-modulated vertebral growth

PURPOSE

This study describes the creation of patient-specific (PS) osteo-ligamentous finite element (FE) models of the spine, ribcage, and pelvis, simulation of up to three years of region-specific, stress-modulated growth, and validation of simulated curve progression with patient clinical angle measurements.

RESEARCH QUESTION

Does the inclusion of region-specific, stress-modulated vertebral growth, in addition to scaling based on age, weight, skeletal maturity, and spine flexibility allow for clinically accurate scoliotic curve progression prediction in patient-specific FE models of the spine, ribcage, and pelvis?

METHODS

Frontal, lateral, and lateral bending X-Rays of five AIS patients were obtained for approximately three-year timespans. PS-FE models were generated by morphing a normative template FE model with landmark points obtained from patient X-rays at the initial X-ray timepoint. Vertebral growth behavior and response to stress, as well as model material properties were made patient-specific based on several prognostic factors. Spine curvature angles from the PS-FE models were compared to the corresponding X-ray measurements.

RESULTS

Average FE model errors were 6.3 ± 4.6°, 12.2 ± 6.6°, 8.9 ± 7.7°, and 5.3 ± 3.4° for thoracic Cobb, lumbar Cobb, kyphosis, and lordosis angles, respectively. Average error in prediction of vertebral wedging at the apex and adjacent levels was 3.2 ± 2.2°. Vertebral column stress ranged from 0.11 MPa in tension to 0.79 MPa in compression.

CONCLUSION

Integration of region-specific stress-modulated growth, as well as adjustment of growth and material properties based on patient-specific data yielded clinically useful prediction accuracy while maintaining physiological stress magnitudes. This framework can be further developed for PS surgical simulation.