By Meridel I. Gatterman, MA, DC, MEd
Risk factors come in a variety of distinctions, from those for cardiovascular disease and some forms of cancer to those less than life-threatening but nonetheless undesirable conditions affecting the quality of a person's life. A risk factor causes a person to be particularly vulnerable to an unwanted, unpleasant or unhealthful event. Risk factors predispose individuals to developing specific conditions. It has been suggested spinal subluxation could be considered such a risk factor. 
Subluxation As a Risk Factor
The following questions should be examined if the concept of subluxation as a risk factor is considered:
Is subluxation of one region of the spine a risk factor for different signs and symptoms as opposed to a subluxation in another spinal area?
If so, does a subluxation in one area create a different syndrome than when it occurs in a different region?
Does clinical observation suggest there are different subluxation syndromes associated with different spinal areas? 
Does a subluxation in the upper cervical region cause a different syndrome than a subluxation in the lower cervical region, and does a subluxation of the sacroiliac joint cause a different syndrome than one at a costovertebral joint? Does a patient's symptomatic complaints and observable signs lead you to suspect a subluxation of one spinal region as opposed to another?
A subluxation syndrome has been defined as an aggregate of signs and symptoms that relate to pathophysiology or dysfunction of spinal and pelvic motion segments or to peripheral joints.  While the signs and symptoms characteristic of subluxation syndromes are not always due to a subluxation, when they are, the condition commonly is responsive to adjustive and manipulative procedures. It is important the examination of patients be inclusive of the clinical indicators that identify subluxations. The components of the PARTS exam, developed by Bergmann  and included in the Medicare Benefit Policy Manual that covers medical and other health services,  commonly is used to identify subluxations.
Subluxation of the Upper Cervical Vertebrae
Headaches from subluxations in the upper cervical vertebrae are responsive to adjustive and manipulative procedures.  Cervicogenic headache is the term most frequently used to describe the syndrome characterized by neck and suboccipital pain that might project to the forehead, temples, vertex and ears.  The pain might increase with specific posture and movement. When examination findings reveal cervical motion segment misalignment, restricted segmental motion, muscle hypertonicity, and/or tenderness, it is suggestive of vertebrogenic pain. 
Cervicogenic headaches can be caused by vertebral subluxation (vertebrogenic headache)  and muscle hypertonicity (muscle tension headache).  Studies suggest both cervicogenic and tension-type headaches are appropriately treated with manipulative therapy. [9-11] It also has been demonstrated that migraine (vascular) headaches respond to manipulation of the upper cervical vertebrae. [12-14] These results suggest subluxation might play a reflex role in the mechanism of migraine that warrants further investigation. If subluxation is a risk factor for migraine headaches, manipulation might serve as a prophylaxis in the prevention of this debilitating condition. 
Subluxation of the Lower Cervical Vertebrae and the First Rib
Subluxations of the lower cervical vertebrae and the first rib generally affect the ipsilateral upper extremity.  Symptoms are characteristic of thoracic outlet syndromes and might include numbness, tingling and vascular changes. A careful differential diagnosis that identifies subluxation of this region is necessary since there are a number of sites at which dysfunction can cause these symptoms. [16-18] Victims of whiplash injuries might develop symptoms in the upper extremities from subluxation of the lower cervical spine and first rib that can be considered risk factors for thoracic-outlet-type problems. 
Subluxation of the Thoracic and Costovertebral Motion Segments
Among the least-recognized subluxation syndromes are those caused by subluxation of the thoracic and costovertebral motion segments. Failure to diagnose these conditions causes untold anxiety and suffering because the main symptom is chest pain, which can be mistaken for a sign of a heart attack.  The sharp pain that accompanies thoracic and rib subluxations is aggravated by movement, respiration, coughing or sneezing.  Examination reveals palpable muscle spasm, motion-segment misalignment, restricted motion, and/or localized tenderness and loss of joint play at the costovertebral joint, with failure of the rib cage to open and close at the rib angle that corresponds to the subluxated rib.  Needless fear and expense can be prevented if subluxation of the thoracic and costovertebral motion segments is recognized as a possible risk factor for chest pain.
Subluxation of the Zygapophyseal Joints
A more precise diagnosis of low back pain involves recognition of subluxation of the zygapophyseal (posterior) joints of the spinal motion segment.  Subluxation of the spinal facet joints can occur in all regions of the spine, causing pain, and is common in the lumbar region. In this region of the spine, provocation of pain on axial compression on extension and rotation, with pain relieved on distraction, is indicative of spinal facet joint involvement. Subluxations of the posterior joints are recognizable through palpable muscle spasm, motion segment misalignment, restricted motion and/or tenderness. Adjustment and manipulation of subluxation of the posterior facet joints has been demonstrated to be effective in the relief of low back pain.  It is suggested that the more than 10 studies which have demonstrated the benefit of manipulation in the treatment of low back pain are describing the removal of subluxation of the posterior (zygapophyseal) joints.
Sacroiliac Joint Subluxation
Sacroiliac subluxation has been recognized as a cause of low back pain. [20-21] The pain is described as dull, radiating into the ipsilateral buttock, and made worse by sitting.  It can refer into the medial thigh and lateral leg. Examination should differentiate between radiating and radicular pain and rule out myofascial pain from direct pressure on the sciatic nerve by the piriformis muscle. Palpation reveals tenderness and loss of play over the joint at the posterior superior iliac spine. Manipulation brings prompt relief.
Subluxation syndromes are not widely recognized. The extent to which subluxations are risk factors for various conditions has not been sufficiently studied. Somatovisceral syndromes caused by subluxation have not been addressed in this column, and the potential for subluxations to be risk factors for these conditions is even less recognized. If pattern recognition of the signs and symptoms that characterize subluxation syndromes were part of the first phase of the diagnostic workup of many patients, much needless suffering could be prevented. Many chiropractic practitioners have observed the signs and symptoms that characterize these syndromes and have treated them effectively. The question is, do we recognize subluxation as a risk factor predisposing the patient to these conditions? If subluxation syndromes were more widely recognized, the benefit to patients and society from more effective health care and decreased costs could be significant.
Is It Time to Adjust Our Thinking About Subluxation?
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