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Importance of the intersegmental trunk
muscles for the stability of the lumbar spine. A biomechanical study in
vitro. Spine
1998 Sep 15;23(18):1937-45
Quint U, Wilke
HJ, Shirazi-Adl A, Parnianpour M; Loer F, Claes LE
Orthopaedic
Clinic University of Essen, Germany. tok030@sp2.power.uni- essen.de
ABSTRACT:
STUDY DESIGN: A
biomechanical study was performed to determine the consequences of a
simulation of muscle forces on the loads imposed on the functional
spinal units.
OBJECTIVES: No biomechanical study has investigated the
effect of incorporation of agonist and antagonist muscle forces on the
loading of functional spinal units.
SUMMARY OF BACKGROUND DATA: Spinal
disorders and low back pain are increasingly becoming a worldwide
problem. Traditional conservative therapies are intended to strengthen
the muscles of the trunk using a judicious regimen of physical
exercises.
METHODS: Eighteen whole, fresh-frozen human cadaveric lumbar
spine specimens (L2-S2; average age, 53.4 years) were tested in a spine
tester using pure flexion-extension, lateral bending, and axial
moments. The effects of coactivation of psoas and multifidus muscles on
L4-L5 mobility were simulated in vitro by applying two pairs of
corresponding force vectors to L4. The segmental stability was defined
by the correlation of an applied moment to the resultant deformation as
shown in load-displacement curves, and the range of motion was defined
as the angular deformation at maximum load.
RESULTS: The coactivation
of muscles was accompanied by a 20% decrease in the range of motion
(i.e., a significant increase in stability) during lateral bending and
axial moments. Application of flexion- extension moments and muscle
coactivation resulted in a 13% increase in the sagittal range of
motion.
CONCLUSIONS: The action of the intersegmental agonist and
antagonist muscles biomechanically increases the overall stiffness
(stability) of the intervertebral joints in axial torque and lateral
bending, whereas it may destabilize the segment in flexion.
PMID: 9779525 UI: 98452561

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