Human lumbar facet joint capsule strains: I. During physiological motions.
BACKGROUND
The lumbar facet joint capsule is innervated with nociceptors and mechanoreceptors, and is thought to play a role in low back pain as well as to function proprioceptively.


OBJECTIVE
In order to examine the facet capsule's potential proprioceptive role, relationships between intracapsular strain and relative spine position were examined.


METHODS
Lumbar facet joint capsule strains were measured in human cadaveric specimens during displacement-controlled motions.


METHODS
Ligamentous lumbar spine specimens (n=7) were potted and actuated without inducing a moment at the point of application. Spines were tested during physiological motions of extension, flexion, left and right lateral bending. Intervertebral angulations (IVA) were measured using biaxial inclinometers mounted on adjacent vertebrae. Joint moments were determined from the applied load at T12 and the respective moment arms. Capsule plane strains were measured by optically tracking the displacements of infrared reflective markers glued to capsule surfaces. Statistical differences (p<.05) in moment, IVA and strain were assessed across facet joint levels using analysis of variance and comparison of linear regressions.


RESULTS
The developed moments and IVAs increased monotonically with increasing displacements; the relationships were highly correlated for all four motion types. Although highly variable among specimens, principal strains also increased monotonically in magnitude with increasing displacements during extension and flexion, but were more complex during lateral bending. At a given joint level, the absolute magnitudes of principal strains and IVA were largest during the same motion type.


CONCLUSIONS
Distinct patterns in principal strains and IVA were identified during physiological motions, lending biomechanical support to the theory that lumbar facet joint capsules could function proprioceptively.
Ianuzzi
Allyson
A
Department of Biomedical Engineering, HSC T18-030, Stony Brook University, Stony Brook, NY 11794-8181, USA.
Little
Jesse S
JS
Chiu
Jonathan B
JB
Baitner
Avi
A
Kawchuk
Greg
G
Khalsa
Partap S
PS
D000328:Adult; D000704:Analysis of Variance; D001696:Biomechanical Phenomena; D002102:Cadaver; D005260:Female; D006801:Humans; D017746:Joint Capsule; D008159:Lumbar Vertebrae / Q000293:injuries; D008297:Male; D008875:Middle Aged; D016059:Range of Motion, Articular / Q000502:physiology*; D012680:Sensitivity and Specificity; D013180:Sprains and Strains; D013314:Stress, Mechanical; D021801:Zygapophyseal Joint / Q000033:anatomy & histology / Q000502:physiology*