Date of Award

Summer 2009

Document Type

Thesis - Restricted

Degree Name

Master of Science (MS)


Biomedical Engineering

First Advisor

Stemper, Brian D.

Second Advisor

Pintar, Frank A.

Third Advisor

Baisden, Jamie L.


Lumbar instability is a major cause of low back pain. Clinical and mechanical definitions identify abnormal motion as a primary feature of instability. Currently, instability measurement involves the quantification of antero-posterior translation during flexion and extension. Other instability indicators have been proposed, including abnormal three-dimensional coupled motions and increased ratios of neutral zone to range of motion. Although normal motion may be segment level and gender dependent, the effects of these factors on normal, three-dimensional kinematics has not been sufficiently quantified in literature. The purpose of the current study was to quantify and qualify the effects of segment level and gender on the three-dimensional kinematics of young, nondegenerated lumbar spines. Motion parameters identified include neutral zone, elastic zone, and range of motion of primary and coupled motions. Post mortem human lumbar spine segments were subjected to pure moment loading in flexion, extension, lateral bending, and axial rotation. Specimens had a mean age of 37 years and were deemed mildly or non-degenerated after radiographic examination. Three-dimensional motion was recorded using stereoradiographic methods. Statistical analysis determined significant segment and gender dependent variations in motion. Segmental variations in the elastic zone and range of motion were significant for all primary and coupled motions except primary axial rotation. Neutral zone did not vary significantly by segment level. Coupled translations followed similar segment dependent trends as the respective primary rotations. Coupled lateral bending was significantly contralateral at cranial segments and significantly ipsilateral at caudal segments. Coupled axial rotation was significantly contralateral at segments Tl2-Ll through L4-L5. Gender was only a significant factor for extension elastic zone and range of motion, with females displaying larger motion than males. The current study has provided a normative database of three-dimensional lumbar kinematics. Antero-posterior translation, as well as the other coupled motions proposed as indicators of instability, varied by segment level. However, the ratio of neutral zone to range of motion did not show a segment dependent trend. Gender did not affect the instability measures. Therefore, the current findings indicate that normal motion is largely segment level dependent and instability measures should be defined accordingly.



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