Format

Send to

Choose Destination
Spine J. 2015 Jun 1;15(6):1302-9. doi: 10.1016/j.spinee.2013.08.020. Epub 2013 Nov 9.

The effect of neighboring segments on the measurement of segmental stiffness in the intact lumbar spine.

Author information

1
Faculty of Human Movement Sciences, VU University Amsterdam, MOVE Research Institute Amsterdam, van der Boechorststraat 9, 1081 BT Amsterdam, The Netherlands.
2
Department of Orthopedic Surgery, VU University Medical Centre, MOVE Research Institute Amsterdam, de Boelelaan 1117, P.O. Box 7057, 1081 HV Amsterdam, The Netherlands.
3
Faculty of Human Movement Sciences, VU University Amsterdam, MOVE Research Institute Amsterdam, van der Boechorststraat 9, 1081 BT Amsterdam, The Netherlands. Electronic address: j.van.dieen@vu.nl.

Abstract

BACKGROUND CONTEXT:

Degeneration, injury, and surgical interventions may alter the mechanical properties of spinal motion segments, but the quantification of these alterations in vivo is problematic. Manual or instrumented loading of single segments in the intact spine as applied intraoperatively may overestimate the mechanical properties of this segment, because the applied load is partly sustained by the adjacent segments.

PURPOSE:

The distribution of stiffness values of individual spinal segments within and across spines was determined so as to use these data as input to a model simulation of segment stiffness tests in intact spines, to assess measurement errors.

STUDY DESIGN:

Biomechanical stiffness measurements on human cadaveric spines and model simulation to assess measurement errors.

METHODS:

Seventeen human cadaveric lumbar spines were loaded with pure moments in flexion/extension, lateral bending, and torsion. An optical system was used to measure the angular rotations of each motion segment and load-displacement curves were used to determine stiffness. With the distribution of measured stiffness data as input, a stochastic mechanical model was constructed to investigate how the stiffness of adjacent segments influences stiffness estimates obtained by loading a single segment in the intact spine.

RESULTS:

The variance in stiffness values was high for all directions, but covaried between segments within a spine. Model simulations indicated that stiffness estimates obtained by loading a single segment in an intact spine are highly correlated with actual stiffness, but overestimate stiffness by a median of 18% with peak errors of close to 400%.

CONCLUSION:

Current measurement devices and manual assessment substantially overestimate segmental stiffness due to the effect of adjacent spinal levels. In addition, the variance in stiffness within spines can occasionally cause large errors, which might lead to erroneous surgical decisions.

KEYWORDS:

Adjacent segment; Biomechanics; Diagnostics; Intraoperative measurement; Spine; Stiffness

PMID:
24215901
DOI:
10.1016/j.spinee.2013.08.020
[Indexed for MEDLINE]
Free full text

Supplemental Content

Full text links

Icon for Elsevier Science
Loading ...
Support Center