Static Palpation of Muscle Imbalance as Compared to Radiographic Evaluation of C1

Paravertebral hypertonicity has been documented in Chiropractic, Orthopedic and Osteopathic literature.1 Muscular tension has been noted upon physical examination of the spine to be associated with spinal misalignment, dysfunction and instability.   These observations have often been anecdotal and incidental to other more objectifiable findings.   It is most often assumed that the hypertonicity, even when found on only one vertebral level, represents spasm.  The inference is that continued muscular activity while the subject is at rest must be a pathological or a "facilitated state."2  That this activity is segmental in nature has only rarely raised suspicion as to the nature of such a localized spasm.   It has gone almost without question that the "spasm" is causally related to the subluxation.   Further, even when authors have suggested the reverse (i.e., that the muscle is an effect of the subluxation), they still often argued that this muscle activity is counter-productive.   It is my contention that resting segmental muscular activity is homeostatic in nature.   The muscles of the spine represent the active stabilization for the functional spinal unit.3,4  A disturbance in the three-joint complex stimulates proprioceptive neural sensory impulses that apprise the spinal cord and subcortical brain.5  The central nervous system could then stimulate guarding muscular action, seeking to reestablish functional balance.  This phenomenon may take place often and be involved whenever there is a difference between the actual and intended movement or position of a functional spinal unit.6,7  In this way resting activity of the muscles would be physiologic and protective in nature.  The mechanism which is thought to underlie such behavior is the stretch reflex.8  The muscles may be serving to return the misaligned segment to its "normal" position.   Such subtle muscle activity would also serve to alert the examining Doctor of Chiropractic as to the existence of the dysfunctional segment.   Presupposing the predictive value of this hypothesis and the accuracy of the palpator’s assessment, this method would also have value in determining the proper line of force application for the adjustment.   The purpose of this study was to understand paravertebral muscular activity and its ability to accurately predict misalignment patterns.

Palpation was limited to the small paravertebral muscles of the two upper cervical vertebrae (see Table 1 ).  Examination was done with the subject supine, with the head in a neutral position, in which the muscles were assumed to be at rest.
 
 

Resting muscles tension was discriminated from normal muscle tone during static palpation.  This assessment was then interpreted according to the untested predictive value of this tension to discern abnormal joint position (e.g., articular dysrelationships).  The anatomical relationship of the muscles to the vertebral motion segments and the theoretical muscular response to the suspected subluxation were assumed from the author's personal publication.  Therefore, palpatory conclusions were derived consistent with the typical muscle pattern activity models described by the author.8 This analysis resulted in a descriptive designation of the direction of malposition for the involved segment, commonly called "listings." The listing abbreviations used by the examining doctor were simplified into four categories and are described in Table 2.

The findings were then recorded before the examiner had any knowledge of the previous radiographic findings.  Radiographic interpretation resulted in listing the involved level of the spine according to the Grostic upper cervical method.

The Palmer listing system describes the anterior and superior (in reference to the relative position of the anterior tubercle of the atlas vertebra) malposition of C-1; thus, "A" is the first letter and "S" (is often) the second to designate a C-1 listing.  "L" or "R" is used for describing the X-axis translation of left or right.  "A" or "P" may be appended as the last letter to define possible C- 1, Y-axis rotation.  These are comparative "movements" of malposition relative to the opposing side of the same segment.

This study was limited not only to the upper cervical spine but was also focused on translation in the transverse plane.  Therefore, palpatory examination was restricted to those muscles thought to demonstrate C-1 translation of left or right and did not take into consideration the muscles that might be used to evaluate the atlas for rotation about the Y axis.  Grostic listings included rotational findings as these findings were obtained prior to and not exclusively for the purposes of this comparison.

Excluding disc involvement (of which the atlas has none), facet effusion is also likely to imbalance C-1 function and set the stage for improper loading of the opposing facet and therefore fixation.  Misalignment of the articular structures is an inevitable result of spinal column short segment buckling, due to mechanical derangement of the connective tissues, including deformation of the articular surfaces (e.g., collagen/proteo-glycan gel matrix of the disc or facet cartilage).10,15 The implication is that fixation represents an inability "...for the vertebral motor units to keep in step with surrounding vertebrae..." or "come to rest naturally in any given posture."8 Thus, buckling can take place gradually with successive "cyclic or vibrational loading conditions...," but ultimately, "...the unstable Functional Spinal Unit is characterized by a decrease in stiffness and a resultant increase in motion under load; both the quantity and quality of spinal motions are altered; the buckling motion appears to occur faster than the muscles can respond..."10 Subsequent to any initial failure of the muscles to prevent the misalignment, it seems reasonable to assume a muscular response to a functional spinal unit (i.e., buckled).  It is likely that resting, segmental muscular activity is a response to mechanical stretch and derangement from the vertebral malposition.  The muscular guarding may be an attempt to reestablish facet and therefore vertebral position.  Where a distinctive "rest position"15 has not been recognized by research, it is undeniable that functional efficiency would demand that the vertebrae articulate according to the dictates of neural expectations.  The central nervous system employs reflex mechanisms to maximize the performance of subordinant structures.5 The stretch reflex is the dominate controlling factor of the musculoskeletal system16 and sets precise neural parameters with structural and functional considerations.  Concerning vertebral placement, only the muscle spindle can generate segment specific activity, whereas most of the other stimuli arise from afferent receptors which ultimately communicate polysynaptically with the paravertebral muscles."17,18 Although Kirkaldy-Willis equivocates on the subject of cause and effect, reflex, segmental muscular activity in the resting spine can be thought to guard the affected tissues of the dysfunctional segment.  He notes that "The posterior segmental muscles protect the joint by sustained hypertonic contraction."19
 
 

REFERENCES
1 Denslow, J.  S., Clough G H, "Reflex activity in the spinal extensors," Journal of Neurophysiology, V.  4:1941; 430- 437.
2 Denslow, J.  S., Hassett C C, "The central excitatory state associated with postural abnormalities," Journal of Neurophysiology, V. 5:1942; 393-402.
3 Dupuis, P.R., "Radiologic diagnosis of degenerative lumbar instability," Spine 10, No.  3:1985; 262-276.
4 Donisch, E.  W., Basmajian J V, "Electromyography of deep back muscles in man," American Joumal of Anatomy, 133: 26-36.
5 Cohen, H., Neuroscience for Rehabititation, J B Lippincott Company, Philadelphia 1993.
6 Mains, R. E., Soechting J F, "A model for the neuromuscular response to sudden disturbances," Journal of Dynamic Systems, Measurement, and Control, December: 1971;1.
7 Wright, J.  "Mechanics in relation to derangement of the facet joints of the spine," Archives of Physical Therapy,1944; 201-206.
8 Spano, N., The Innate Biomechanics of the Spine. Self published, l984.
9 Grostic, J.  D., Grostic Procedure Notes.  Self published,1993.
10 Weinstein J.  N., Wiesel S W, The Lumbar Spine, 614- 618, W B Saunders Company, Philadelphia 1990.
11 Panjabi, M.  M., Krag, M.  H., Chung, T.  Q., " Effects of disc injury on mechanical behavior of the human spine," Spine, V.  9, No.  7 1984; 707-713.
12 Jayson, M.  I.  V., The Lumbar Spine and Back Pain, Churchill Livingston, New York,1987; 51, 373.
13 Gertzbein, S.  D., et al, "Centrode patterns and segmental instability in degenerative disc disease," Spine, V.10, No.  3,1985; 257-261.
14 Kirkaldy-Willis, W.  H., "The relationship of structural pathology to the nerve roots," Spine, V.  9, No.1,1984; 49-52.
15 Haldeman,S., Principles and Practice of Chiropractic, Appleton & Lange, Norwalk, CT,1992; 248-251.
16 Grieve, G.  P., Modem Manual Therapy of the Vertebral Column, Churchill Livingstone, New York,1986; 500.
17 Wyke, B., "The Neurological Basis Of Thoracic Spinal Pain," Rheumatol Phys. Med., V.10,1970; 356-367.
18 Schafer, R.C.  Basic Principles of Chiropractic, The American Chiropractic Association, Arlington, VA, 1990; 270.
19 Kirkaldy-Willis, W.H.  Burton C V Managing Low Back Pain, Churchill Livingstone, New York, 1992.

I would like to thank Dr.  John Grostic and Life Chiropractic College, for the use of their research facility and cooperation.  I would also like to thank the students of Life Chiropractic College who participated in the study.

| Index |