Reprinted from JOURNAL OF SPINAL DISORDERS & TECHNIQUES
Copyright @ L992 by Lippincott Williams & Wilkins
Printed in U.S.A.
As co-editor of Journal of Spinal Disorders, I am
delighted to ofer to our readership this elegant hy-
pothesis ofered by Panjabi. I encourage all ofyou to
read both the compelling article by Panjabi, and the
articulate commentary by Krag. Such thoughtful dis-
course will do much to enhance our understanding of
spinal stability. In addition, I hope that the areas of
controversy will provide the impetusforfurther investi-
gations. Manuscripts such as these will be published
on a periodic basis to offer the concepts, thoughts, and
ideas of recognized authorities who are involved in
studying spinal disorders.
Dan M. Spengler, M. D.
Low back pain is a well-recognized problem of the
lation and resulting in substantial social loss (2,I I,23,
37). Because the etiology is unknown for most types
of low back pain (38), it is not surprising that many of
the present treatments are relatively ineffective.
Spinal instability is considered to be one of the im-
portant causes oflow back pain but is poorly defined
and not well understood (24). The basic concept of
spinal instability is that abnormally large interverte-
bral motions cause either compression and/or stretch-
ing of the inflamed neural elements or abnormal de-
formations of ligaments, joint capsules, annular
fibers, and end-plates, which are known to have signif-
icant density ofnocioceptors (41). In both situations,
the abnormally large intervertebral motions may pro-
duce pain sensation.
Knutsson (19) was probably the first to propose a
Address correspondence and reprint requests to Dr. M. M. Pan-
jabi, Department ofOrthopaedics and Rehabilitation, Yale Univer-
sity School of Medicine, New Haven, CT 06510, U.S.A.
The Stabilizing System of the Spine. Part I. Function,
Dysfunction, Adaptation, and Enhancement
Manohar M. Panjabi
Department of Orthopaedics and Rehabilitation, Yale University School of Medicine, New Haven, Connecticw U.S.A.
Summary: Presented here is the conceptual basis for the assertion that the spinal
stabilizing system consists ofthree subsystems. The vertebrae, discs, and ligaments
constitute the passive subsystem. All muscles and tendons surrounding the spinal
column that can apply forces to the spinal column constitute the active subsystem.
The nerves and central nervous system comprise the neural subsystem, which
determines the requirements for spinal stability by monitoring the various trans-
ducer signals, and directs the active subsystem to provide the needed stability. A
dysfunction of a component of any one of the subsystems may lead to one or more
of the following three possibilities: (a) an immediate response from other subsys-
tems to successfully compensate, (b) a long-term adaptation response of one or
more subsystems, and (c) an injury to one or more components of any subsystem.
It is conceptualized that the first response results in normal function, the second
results in normal function but with an altered spinal stabilizing system, and the
third leads to overall system dysfunction, producing, for example, low back pain.
In situations where additional loads or complex postures are anticipated, the
neural control unit may alter the muscle recruitment strategy, with the temporary
goal of enhancing the spine stability beyond the normal requirements. Key
Words: Spine stabilizing system-Spinal instability-Lumbar spine-Muscle
function-Low back pain.
SPINE STABILIZING SYSTEM I
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mechanics. Physiological strains in lumbar spinal ligaments.
An in vitro biomechanical study. Spine 7:192-203, 1982
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Volvo Award in Biomechanics. Spine l3:982-992, 1988
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lumbar spinal movements measured by three-dimensional x-
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Spine lO:175-177, 1985
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Department of Orthopaedic Surgery, University of Goteborg,
Tryckeri AB Litotyp, 1966
36. Seligman J, Gertzbein S, Tile M, Kapasouri A: 1984 Volvo
Award in Basic Science. Computer analysis of spinal segment
motion in degenerative disc disease with and without axial
loading. Spine 9:566-57 3, 1984
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industry; a retrospective study. I. Overview and cost analysis.
Spine ll:241-245, 1986
38. White A, Gordon S: Synopsis: workshop on idiopathic low-
back pain. Spine T :l4l-149, 1982
39. White AA, Panjabi MMl' Clinical biomechanics of the spine,
2nd ed, Philadelphia, JB Lippincott, 1990
40. Woody J, Lehman T, Weinstein J, Hayes M, Spratt K: The
diagnosis ofsegmental instability in vivo by centrode length.
Proceedings ofthe International Society for the Study ofthe
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J Spinal Disord Vol.5, No.4, 1992