Kinematics and movement sequencing during flexion of the lumbar spine.
OBJECTIVE
This study investigated the sequence of intervertebral joint movements and range of motion during three tasks involving lumbar flexion.


METHODS
Position sensors were used to measure position and rotation of lumbar vertebrae during unconstrained flexion.


BACKGROUND
In the development of mathematical models, numerous assumptions need to be made. Few studies have attempted to assess the validity of the assumptions regarding kinematics in models of the lumbar spine.


METHODS
Position sensors were attached to the skin overlying the lumbar vertebrae of 14 volunteers. Volunteers performed three flexion tasks; unconstrained flexion from upright standing, with and without a mass of 5 kg held close to the body, and the transition from upright standing to a seated position.


RESULTS
Four definitive movement sequences were identified for those subjects with consistency between replicates; 'top down' motion (where the top of the lumbar spine starts to move first and the bottom moves last), 'bottom up' (where the bottom of the lumbar spine moves first and the top moves last), 'all together' (where all segments commence movement together), and 'middle last' (where the middle segments of the lumbar spine are last to commence movement). Subjects not fitting one of these sequences were categorised into a miscellaneous group. Only two subjects exhibited the same sequence for each of the three tasks, while other subjects exhibited two or three different sequences for the three tasks, or showed a lack of consistency for one of the tasks.


CONCLUSIONS
The results from this study indicate that there is no single movement sequence exhibited by the sample population.


CONCLUSIONS
Incorrect assumptions which are incorporated into mathematical models have the potential to influence model output. Given that output from spinal models is often used to assess ergonomic issues such as safe lifting loads, validation of the assumptions is essential.
Gatton
M L
ML
Centre for Rehabilitation Science and Engineering, School of Mechanical, Manufacturing and Medical Engineering, Queensland University of Technology, Brisbane, Australia. mgatton@qut.edu.au
Pearcy
M J
MJ
D000293:Adolescent; D000328:Adult; D005260:Female; D006801:Humans; D008159:Lumbar Vertebrae / Q000502:physiology*; D008297:Male; D009068:Movement / Q000502:physiology*; D016059:Range of Motion, Articular; D013647:Task Performance and Analysis