What is Loss of Motion Segment Integrity?

Hypermobile Subluxations, Instability and Loss of Motion Segment Integrity

Dean L. Smith, D.C., M.Sc.,(1) and Harold G. McCoy, DC, DACS, DABFE(2)

1 Department of Psychology, Miami University, Oxford Ohio 45056.
2 President - Myo-Logic Diagnostics Inc., Kirkland WA 98033

When applied to the spine, kinesiopathology, refers to segmental spinal dysfunction that can either present as hypermobility, hypomobility, or aberrant paths/rhythms of vertebral units. This is believed to alter normal joint biomechanics.1-3 As a result of the chiropractic adjustment, however, the hypomobile vertebral motion segments are often corrected. Thus, this component of the vertebral subluxation is easily demonstrable, and is often the component most readily identified with spinal dysfunction.4 But what about the hypermobile subluxation? The hypermobile subluxation and its extreme forms, instability and loss of motion segment integrity (LMSI) are the focus of this article.

Chiropractors focus on restoring motion to the "fixated" or hypomobile vertebral segments. We do this for a number of reasons. Firstly, we were taught in chiropractic college to adjust "only what you find". Secondly, it does not make sense to add motion to a segment that is moving excessively already, unless a particular range or plane of motion is restricted. Finally, as mentioned previously, this component of subluxation is easily demonstrable.

Less often talked about in chiropractic practice is excessive segmental kinematics. It is important to characterize the differences and similarities between hypermobility, instability and loss of motion segment integrity because they may have different etiologies and clinical implications. The reader is encouraged to keep in mind that spinal instability has long been a highly controversial concept5, especially those cases involving degenerative spinal disorders. The term spinal instability is open to more than one interpretation.6 Confusion appears to exist between mechanical instability, risk of instability and clinical instability.5 Definitions of each are provided below.

Segmental Hypermobility - The mobility of a given motion unit which is excessive but not so extreme as to be life-threatening or require surgery.7 (as applied to the cervical spine) Authors seem less clear about the distinction between hypermobility and instability in the lumbar spine.8-10 Grieve11 states that "hypermobility" represents "a little too much motion," and need not be painful, be clinically significant, or lead to instability.

Spinal Instability - Loss of the ability of the spine under physiologic loads to maintain relationships between vertebrae in such a way that there is neither damage nor subsequent irritation to the spinal cord or nerve roots, and in addition, there is no development of incapacitating deformities or pain due to structural changes.12 (as applied to the cervical spine) Instability occurs in a degenerating lumbar segment that is functionally incompetent because of insufficient soft tissue control.11

Loss of Motion Segment Integrity - Abnormal back-and-forth motion (translation) or abnormal angular motion of a motion segment with respect to an adjacent motion segment. The loss of integrity is defined as an antero-posterior motion or slipping of one vertebra over another greater than 3.5mm for a cervical vertebra or greater than 5mm for a vertebra in the thoracic or lumbar spine; or a difference in the angular motion of two adjacent motion segments greater than 11° in response to spine flexion and extension. Loss of integrity of the lumbosacral joint is defined as an angular motion between L-5 and S-1 that is 15° greater than the motion at the L-4, L-5 level.13

It is clear to see that all three of these definitions vary in terms of the stringency of criteria. There are also distinctions made between cervical and lumbar hypermobility and instability. The possibility of serious neurological sequelae following lumbar instability is not as great as for cervical instability, perhaps because the possibility for acute traumatic ligament injury is far more common in the cervical spine. Least stringent is hypermobility as you might expect. Peterson8, cites a few authors who claim that hypermobility may be a precursor to instability if not managed appropriately. Although a universally accepted definition of spinal instability and its clinical implications has yet to be agreed on, LMSI does have relatively clear-cut criteria for its presence. LMSI provides a quantitative basis for its establishment, independent of symptomatology and is recognized by the American Medical Association. As a result, LMSI provides a "definitive" way to assess increased vertebral motion.

In general, spinal instability could be inferred if there exists an alteration in at least one of the elements responsible for spinal stability, assuming no augmentation of the other elements. According to Panjabi 14, the spinal stabilizing system consists of three interrelating sub-systems. These are the passive subsystem (e.g. ligaments), control (neural) subsystem and the active (muscular) subsystem. Facilitation of one element may compensate functionally for a reduction in ability of another. For example, appropriate exercise can enable the active subsystem to take more of the total load placed on the spine, allowing the passive subsystem to repair itself 15 (in the presence of injury). However, without appropriate integrity, regulation and co-ordination of these subsystems, spinal stability will be compromised. For further information on stability in relation to clinical practice, McGill16 provides a recent review of stability "from biomechanical concept to chiropractic practice."

What can cause hypermobility, instability and/or LMSI? Abnormally increased intersegmental motion to the point of potentially damaging spinal cord or nerve roots has multiple causes. These can include trauma, degenerative and inflammatory joint conditions, fusion surgery and laminectomies, congenital abnormalities, repeated microtrauma, and compensatory movement due to neighboring hypomobile segments.8

Now we will discuss how subluxation based care can impact hypermobile segments. The potential is present for chiropractic to reduce excessive motion in compensated joints by correcting the underlying hypomobile segments. The clinic run by Dr. Harold McCoy has had numerous cases illustrating this principle. Dr. McCoy selected 70 cases from his clinic in which the criterion for LMSI was met prior to care and did post comparison x-rays when clinical/functional improvement began to level off. These cases all involved cervical trauma and LMSI in translation and/or angular variation. During the application of subluxation based chiropractic care (consistent with the CCP Guidelines17), half of those cases showed significant improvement in the translational and angular numerical measurements. Fifty percent of the translational values greater than 3.5 mm were reduced below the 3.5mm threshold. In addition, 50% of the angular variations greater than 11 degrees were reduced below the 11 degree threshold. Furthermore, Dr. McCoy consults other practitioners who send him their x-rays for a report that identifies specific levels of LMSI and other important objective structural findings. Dr. McCoy notes that of the films that are sent to him, 70% display LMSI.

It is important to note that Dr. McCoy assesses patient progress in a multi-factorial nature, as these assessments determine clinical improvement. Muscular strength, ROM, spirometry, x-ray analysis, and various health and lifestyle surveys are all used as indicators of improvement following chiropractic care.

The importance of these findings cannot be understated. For example, the AMA Guides attribute a 25% whole-person impairment rating to those who meet LMSI criteria in the cervical spine and 20% with LMSI in the lumbar spine. Following chiropractic care as reported by Dr. McCoy, the integrity loss was reduced below threshold criterion in 50% of cases. The potential implications of such findings could indicate but are not limited to: reduced need for surgery due to improved stability, reduced neurological deficits, and less whole body impairment. Reduction of LMSI, along with improved muscular strength, spirometry, ROM, EMG and other tests offers the chiropractor an objective way to document the effectiveness of care and demonstrate benefit to the patient.

Any chiropractic practitioner who has taken care of persons who have met LMSI criteria may have noticed similar results to those described previously. A dramatic improvement in the kinesiological component of subluxation may very well translate into improved neurological status. An improvement in neurological function following chiropractic care may well show up on objective measures such as muscular strength18, spirometry19, cardiovascular function and other visceral indicators,18,20 ROM and so on. The human body is formed in such a way that somatic inputs into the nervous system cannot be made without affecting multiple organ systems.21 The improved function of these systems may be a good indicator of the "return to health" of an individual.

Chiropractors not only have the ability to improve hypomobile subluxations, but as a result of these corrections may in some cases be dramatically influencing the kinematics of hypermobile segments above and below as well. Specifically, hypermobility and its extreme forms, instability and loss of motion segment integrity (LMSI) whether as a result of injury or compensation could be reduced by chiropractic care. The implications of such findings being the possibility of reduced need for surgery due to improved stability, improved neurological status, less whole body impairment, and improved overall health.

References:

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  9. Grieve GP. Lumbar instability. Physiotherapy 1982; 68:2-9.
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  11. American Medical Association. Guides to the evaluation of permanent impairment. 4th ed. Chicago, Ill: AMA, 1993.
  12. Council on Chiropractic Practice. Clinical Practice Guideline: Vertebral Subluxation in Chiropractic Practice, 1998.
  13. Smith DL, Cox RH. Muscular strength and chiropractic: theoretical mechanisms and health implications. JVSR 1999-2000; 3(4): 1-13.
  14. Kessinger R. Changes in pulmonary function associated with upper cervical specific chiropractic care. JVSR 1997; 1(3): 43-49.
  15. Webster SK, Alattar M. Literature review: mechanisms of physiological responses to chiropractic adjustment. CRJ 1999; VI(1): 14-22.
  16. Schmitt WH, Yanuck SF. Expanding the neurological examination using functional neurologic assessment: Part II neurologic basis of applied kinesiology. Intern J Neuroscience 1999; 97: 77-108.
  17. Council on Chiropractic Practice. Clinical Practice Guideline: Vertebral Subluxation in Chiropractic Practice, 1998.
  18. Smith DL, Cox RH. Muscular strength and chiropractic: theoretical mechanisms and health implications. JVSR 1999-2000; 3(4): 1-13.
  19. Kessinger R. Changes in pulmonary function associated with upper cervical specific chiropractic care. JVSR 1997; 1(3): 43-49.
  20. Webster SK, Alattar M. Literature review: mechanisms of physiological responses to chiropractic adjustment. CRJ 1999; VI(1): 14-22.
  21. Schmitt WH, Yanuck SF. Expanding the neurological examination using functional neurologic assessment: Part II neurologic basis of applied kinesiology. Intern J Neuroscience 1999; 97: 77-108.