(this paper was originally published in The Upper Cervical Monograph, May 2001)
Some Implications Regarding Tensegrity and
the Upper Cervical Adjustment
Michael D. Thomas
Origin of chiropractic embedded in the concept of tone and renitency.
D.D. Palmer conceived of the dynamics within a human organism as an interplay of two forces. He termed the two opposing forces â€œtoneâ€ and â€œrenitencyâ€. He believed that this tone or tension was opposed (and balanced) by resistance to tension or renitency. Abnormal increase in tone created localized areas of increased tissue temperature. These areas of increased heat could be palpated by the fingers. This soon led to the â€œfollowingâ€ (by palpation) of the hyperthermic tissue back to the spine. This localized hyperthermia became the initial diagnostic indicator for dys-function. Palmer hypothesized that abnormal alteration in structure (subluxation) created abnormal alteration in function (dis-ease). Correction of the abnormality in structure (the adjustment) allowed normalization of function to recur.
This train of thought requires the conviction that the self-organizing ability of the organism is adequate to maintain optimal health if interference to itâ€™s function can be removed. This is very different from trying to â€œcontrolâ€ the altered physiology through â€œtherapeuticâ€ means. Attempting to â€œdriveâ€ the organism (even in a minor way) is very different from â€œremoval of interferenceâ€.
The empirical nature of orthogonal upper cervical work.
Upper cervical chiropractic began as an empirical exercise. In the Grostic model, it has long been recognized that orthogonal arrangement of the upper cervical alignment is critical to overall biomechanical stability and optimization of function. It is apparent to many of us that correction of the atlas subluxation complex is the â€œspecificâ€ that chiropractic has sought.
The Grostic work was an extrapolation of this idea, forged into a practical protocol. Once the measurement system allowed more accurate analysis, (using measurement of the angular rotation of the structures in relation to each other, rather than linear measurement) it was understood that it would be necessary to work out a systematic protocol that could optimize maximal, proportional correction of each individual misalignment pattern. This process was largely empirical. There is an apocryphal story that at the very beginning, each misalignment was addressed as a H2A2 on the side of laterality. This is how empirical reasoning begins. Do something, see what happens. Change what you do, see how that changes the result. Soon, in the Grostic work, the four elements were identified for the misalignment pattern in the frontal plane. The proper algorithms to address the rotational patterns of the upper cervical spine in the transverse plane, were also soon investigated.
Much later, (in the NUCCA work) Gregory began to formulate a biomechanics of the upper cervical spine based on lever systems that he hypothesized to be operational in the area of C0-C1-C2. This biomechanical analysis resulted in an ability to reason out an optimal vector to more fully maximize proportional correction and to trouble-shoot problems when the spine did not reduce as expected. This system of biomechanical analysis has, for the first time, allowed the teaching of a practical protocol to large numbers of students who are then able to reproduce the corrective results in their patients.
The impact of this protocol cannot be over-estimated. Earlier versions of upper cervical chiropractic were often unable to be taught to large numbers of students because the variables were simply not yet understood in the depth necessary to allow consistent correction of complex subluxation patterns. Without firm grounding in an objective biomechanics, few individuals had the intuitive or intellectual abilities to codify the manifold complexities of the many variations of subluxation patterns and consistently correct them.
It will not be the attempt of this paper to overturn or even to question the value of this rational approach to the upper cervical spine. Indeed, I am grateful many times each day for the ability to adjust my patients from this perspective and to marvel at the results in their lives. Removal of the interference identified by this approach has amplified, and sometimes saved, the lives of millions of people over the last fifty years or so.
Newtonâ€™s understanding of physics revolutionized mankindâ€™s ability to understand the physical forces of our world. In the last century, a new understanding of the quantum nature of the physical world has again revolutionized our perspective. However, we continue to use the equations of Newton in our various works because they are practical approximations that work very successfully at this level of magnitude. Attempting to use quantum mechanics to describe these same problems is possible and could result in correct answers, but the complexity of accounting for each quanta at this level of magnitude is virtually untenable even using the largest computers yet imagined. At the same time, this new perspective has revealed an understanding of reality that has fundamentally altered the way we look at our world. Our sense of possibility has quite literally taken a â€œquantum-leapâ€!
It is the hope of this author that an examination of some concepts which are currently surfacing in various investigations around the world may be of use to the evolution of upper cervical chiropractic in the future.
â€œTensegrityâ€ was coined from the words â€œtensional integrityâ€ by Buckminster Fuller to denote a structure that retains its integrity under tension. The concept was first formulated by Kenneth Snelson, an American sculptor and one-time student of Fuller. Tension may also be considered as â€œpullingâ€, and compression as â€œpushingâ€. This concept has obvious parallels with tone and renitency. A structure that uses tension as well as compression to support itself may be considered to use the property of tensegrity. This structural property can be seen throughout the physical universe, from atoms to galaxies, from snowflakes and radiolaria to human beings.
Traditionally, human-made structures have relied on the compressive forces of gravity. Indeed, if your home were suddenly removed to the vacuum of space, it would break apart because it relies on the compression of mass following the force of gravity to maintain its stability. Organic forms are mobile. If they relied only on compressive forces to maintain their stability, they could never shift their orientation with respect to gravity. If they did, they would completely lose their stability. Instead, organisms rely upon both tension and compression to maintain stability.
Until very recently, all mathematical models describing the spine have been based upon axial-loaded compression based mechanics. However these models all break down when the spine is observed to move away from the vertical axis. The same compressive forces that maintain stability in the vertical position will cause the spine to be, as Levin noted:
â€œâ€¦pulled apartâ€¦if tilted out of plumb. The mechanical laws of leverage that operate in the compressional system would create forces that far outstrip any strength of biologic materials. We could not use such a system to walk on our two legs, crawl on all fours, walk on our hands or stand on our heads without the addition of tensional forces to hold us together. Such a system is only as strong as its weakest link. The laws of leverage act differently when applied within the tensegrity system so that forces generated are dissipated and may actually strengthen the structure much as prestressed concrete or a wire under tension. External forces applied to the system are dissipated throughout it so that the â€œweak linkâ€ is protected. The forces generated at heelstrike as a 200 pound linebacker runs down the field, for example, could not be absorbed solely by the os calcis but have to be distributed-shock absorber-like- throughout the body.â€(1)
The components of tensegrity structures are all â€œpre-stressedâ€. As tension increases and is distributed throughout, the structure is balanced by an equal increase in compression. Stability is maintained through what Fuller called â€œcontinuous tension and local compressionâ€.
â€œTensional forces naturally transmit themselves over the shortest distance between two points, so the members of a tensegrity structure are precisely positioned to best withstand stress.â€(2)
This may recall Wolffâ€™s Law to the readerâ€™s mind. It has long been known that bones change shape according to the forces placed upon them. The very trabecular patterns forming the matrix of the bone structure shift over time, in response to alteration in load bearing as it is applied to the bone. It is now beginning to appear that this property is present in all the tissues of the organism.
Of at least equal importance, Ingber also relates that :
â€œ â€¦tensegrity structures function as coupled harmonic oscillators. DNA, nuclei, cytoskeletal filaments, membrane ion channels and entire living cells exhibit characteristic resonant frequencies of vibration. Very simply, transmission of tension through a tensegrity array provides a means to distribute forces to all interconnected elements and, at the same time, to couple, or â€œtune,â€ the whole system mechanically as one.â€(3)
Levin presented a couple of examples of tensegrity at work in the human structure.
â€œThe entire support system of the upper extremity is a tension system being supported by the musculature interweaving the spine, thorax and upper extremity into a tension support system. The scapula does not press on the thorax. The clavicle has been traditionally recognized as acting more as a compression strut, as it would in a tensegrity model.â€
â€œThe anatomist Grant, in his classic book, â€œMethods of Anatomyâ€ describes the sacroiliac joint, the major supporting joint between the pelvis and spine and its superimposed structures. He states that the sacrum behaves not as a keystone but as the reverse of a keystone, and tends, therefore to sink for-ward into the pelvis. The spine and its superimposed structures are, of course, supported by the massive ligaments so that the sacrum-and all that is above it- is â€œslungâ€ in the pelvis and not dependant on axial-compressive support.â€ (4)
In another paper, Levin goes into much more detail regarding the biomechanics of the shoulder girdle. In the abstract to this paper, he explains:
â€œThe least successfully modeled joint complex has been the shoulder. In multi-segmental shoulder models rigid beams (the bones) act as a series of columns or levers to transmit forces or loads to the axial skeleton. Forces passing through the almost frictionless joints must, somehow, always be directed perfectly perpendicular to the joints as only loads directed at right angles to the surfaces could transfer across frictionless joints. Loads transmitted to the axial skeleton would have to pass through the moving ribs or the weak jointed clavicle and then through the ribs. A new model of the shoulder girdle, based on the tension icosahedron described by Buckminster Fuller, is proposed that permits the compression loads passing through the arm and shoulder to be transferred to the axial skeleton through its soft tissues. In this model the scapula â€œfloatsâ€ in the tension network of shoulder girdle muscles just as the hub of the wire wheel is suspended in its tension network of spokes. With this construct inefficient beams and levers are eliminated. A more energy efficient, load distributing, integrated, hierarchical system is created.â€(5)
Conceiving of the shoulder as a tensegrity structure helps to explain why compressive loads from the arm can be transferred from the scapula to the spine without any rigid, compressive load bearing structure which links the scapula and the axial skeleton together. Without this connection, there is also no adequate fulcrum.
Levin further explains:
â€œIn a linked system a seamless continuum of compression elements are necessary. Bone must compress bone. The almost frictionless joints would require forces to be always directed at right angles to the joint. The scapula is not anatomically situated to transfer loads through the ribs to the spine. Even if it were, the ribs could not take those loads and act as levers to connect to the spine.
The ribs themselves, by shape, position and connection, are not structurally capable of transferring these loads. The clavicle is in no shape to transfer loads either. It is a crank shaped beam that connects the scapula to the sternum by a small, mobile joint that could not transfer compressive loads of any significant magnitude.â€(6)
The description of the shoulder girdle as a tensegrity structure may sound somewhat familiar to the student of the NUCCA work. Although not defined as such, the adjustment was understood by Gregory as much more than merely an â€œarmâ€ delivered adjustment. The procedure for the delivery of the adjustment requires proper alignment of the adjustorâ€™s entire body. The magnitude and direction of the adjustic force is determined by the proper alignment of forces within the adjustorâ€™s body. The concept of the â€œclosed kinetic chainâ€ effect (as described by Gregory) in the delivery of the adjustive force is certainly paralleled by the property of tensegrity.
It has been shown by several investigators that ligaments are under continuous tension even in a neutral position. The ligamentum flavum, anterior longitudinal ligament and the posterior longitudinal ligament all have been observed to maintain a baseline tone even when the spine is in a neutral position. (7a,b,c)
Clearly, the soft tissue elements are capable of continuously transmitting forces throughout the entire framework of the body. â€œLinkingâ€ of the tensegrity structures (through loading of the patientâ€™s upper cervical joint complex by proper positioning of the adjustorâ€™s body) between the pisiform of the adjustor and the atlas transverse process of the patient, allows distributive transfer of the tension present in the adjustorâ€™s body down a specific vector (specifically defined through the adjustic stance). This force distributively affects the tensegrity structure of the patient. Ideally, it will do so in just the proper way to restore biomechanical integrity.
As Ingber states:
â€œâ€¦the 206 bones that constitute our skeleton are pulled up against the force of gravity and stabilized in a vertical form by the pull of tensile muscles, tendons and ligamentsâ€¦In other words, in the complex tensegrity structure inside every one of us, bones are the compression struts, and muscles, tendons, and ligaments are the tension bearing membersâ€ (8)
If examining the NUCCA work in the light of the property of tensegrity leads to a wider view, the resulting new perspective can potentially improve biomechanical understanding of the upper cervical subluxation complex. At the same time, it is clear that the Newtonian formulation of the involved dynamics have been extremely successful.
The cell as a tensegrity structure
Not so long ago, the cell was â€œseenâ€ as a â€œbag of concentrated solution of enzymes and metabolites mixed up at random, save for a few organelles and intracellular membranes.â€ (9) Much of this view came from the methods used to investigate the cellular components. The standard procedure of the time was to homogenate or grind up the various components of the cell and then separate the different â€œfractionsâ€ according to size or density. If a specific â€œfractionâ€ was being investigated, the other â€œfractionsâ€ were removed. The resulting â€œpureâ€ fraction was then dissolved in deionized water to which ultrapure substrates were added. A long process to â€œcharacterizeâ€ the enzyme activity then began. All of this, as Ho points out, serves to reinforce the notion of the cell being nothing more than a bag of enzymes and metabolites dissolved in solution.(10)
Ho brings us up to date:
â€œAs electron microscopy and other specific staining techniques became available, it gradually dawned on us that the cell is highly structured. Nowadays, the generally accepted picture of a cell is quite sophisticated. It is bound by the cell membrane â€“ a double layer of lipids, which is supported by and attached to the membrane skeleton composed of a basketwork of contractile filamentous proteins lying immediately underneath it. The membrane skeleton in turn connects with the three-dimensional network of various fibrous proteins collectively known as the â€œcytoskeletonâ€, which links up the inside of the cell like a system of telegraph wires terminating onto the membrane of the nucleus. In the nucleus, the chromosomes (organized complexes of DNA and proteins) are anchored directly to the inside of the nuclear membrane. The nuclear membrane and the cell membrane are also in communication via concentric stacks of membranous vesicles, the Golgi apparatus- with special secretory functions, and the endoplasmic reticulum â€“ a system of three-dimensional canals and spaces believed to be involved in intracellular transport and occupying a large proportion of the cell volume. A substantial volume is also taken up by organelles such as the mitochondria, where simple carbohydrates are oxidized to CO2 and H20 with the generation of ATP, and ribosomes on which polypeptide chains are synthesized. Finally, what is left over is the cytosol (or â€˜solubleâ€™ cytoplasm).â€(11)
In addition, it is now believed by many that most of the water found in the cell is bound (or structured) on the manifold surfaces within the cell. (12) This â€œbag of solution chemistryâ€ is now being recognized as a solid state system. The implications of viewing the cell and by fractal reasoning, the organism, as a solid state system are most profound, though beyond the scope of this paper.
Ingber reports on the current understanding of the cytoskeleton (CSK):
â€œIt is now accepted that the CSK of eukaryotic cells exists as a complex interweaving meshwork of three major classes of filamentous biopolymersâ€¦ Most biologists agree that actomyosin interactions within contractile [microfilaments] generate CSK tension and that all three filament systems provide some structural function. However there is no model of CSK organization that can explain how these filament systems associate and integrate so as to form a continuous â€œsolidâ€ network that can change shape and move.â€(13)
Ingber posits that tensegrity offers a globally integrated architectural model that explains the coordination between the â€œpart and the whole that is so characteristic of the CSKâ€.(14) Cells spread and are motile, they undergo transformations in size, shape and function. Organismic function requires fluid and coordinated movement at every level, from tissue to cell to molecule. Again, quoting Ingber:
â€œIf cells do use tensegrity, then we will need to change our frame of reference in studies on CSK remodeling and cell shape to include the concept of a pre-stressed CSK. In other words, we need to transform our image of cell architecture from a rigid static view that is largely based on local molecular binding events into one that is mechanically based, globally integrated and dynamic. Inherent in this form of architecture is a mechanism for mechanical information transferâ€¦integration between all parts, both large and smallâ€¦that is based entirely on provision of tensional continuity. Thus a central tenet of tensegrity is that every structural element with the system is poised to sense and immediately respond to physical stimuli from both inside and outside the cell. It is difficult to think of another type of building system that could explain how stretching a tissue such as skin, results in extension of the ECM [extracellular matrix], cell, CSK and nucleus in a coordinated manner without producing any structural breakage or disconnectionâ€¦.â€(15)
Beyond explaining global integration of movement both intra and inter-cellularly, Ingber has hypothesized how tensegrity can also model coordinated information transfer:
â€œTensegrity provides a mechanism to mechanically and harmonically couple interconnected structures at different size scales and in different locations throughout living cells and tissuesâ€¦Thus cell and tissue tone may be tuned by altering the prestress of the system. This may be accomplished by altering the architecture of the system or the level of CSK tensionâ€¦In either case, increasing the stiffness of the network will alter vibration frequencies and associated molecular mechanics of all the constituent support element. This may, in part, explain how the part (molecule, cell) and whole (e.g., cell, tissue, organ, organism) can function as a single mechanically integrated systemâ€¦
This tuning mechanism also may play an important role in mechanical signal amplification, as well as in the adaptation responses that are necessary to tune out certain signalsâ€¦Any one of these changes may feed back to tune the mechanotransduction response, as seen in studies with intact cellsâ€¦
On a larger scale, alterations in CSK stiffness or in the number of load-bearing elements in the system will change how stress dissipates in the network before it reaches the molecular transducer. A cell that is very stiff may be able to sense lower levels of stress more quickly than a more flexible cell. Conversely, the more flexible cell may be able to sense larger strains. This adaptability may contribute to the different sensitivities exhibited by specialized mechanosensory cells; for example, the stiff hair cells of the inner ear sense small vibrations, whereas more flexible spindle cells of muscle recognize changes in length (stretch). A similar mechanism may explain why osteocytes, which contain highly extended (and hence stiffened) processes, preferentially respond to high frequency and low amplitude strainsâ€¦
Finally, because the ECM physically interconnects with the CSK, its mechanical properties may also contribute significantly to the mechanotransduction response. If the ECM is highly flexible, then a rapid deformation may be sensed, whereas a sustained stress will dissipate before it reaches the cellâ€¦The resistance imposed by the relatively inflexible ECM induces global rearrangements in the CSK through a tensegrity mechanism, as measured by a linear stiffening responseâ€¦These changes in CSK mechanics, in turn, may serve to simultaneously modulate multiple signaling mechanisms.â€(16)
D.D. Palmer seems to have gotten it right. Structure does affect function. An interesting example can be found in a study by Wirtz and Dobbs who examined the effects of mechanical distension on alveolar type II cells. They found that a single stretch on one cell resulted in â€œa transient (less than 60 seconds) increase in cytosolic Ca(2+) followed by a sustained (15 to 30 minutes) stimulation of surfactant secretion.â€(17) As the entire frame of an individual distorts secondary to the ASC, there is effect on every tissue and cell. There is increasing evidence that genetic expression too, is altered by changes in the mechanical forces acting on the cell. The effects of the ASC resonate deeply and on many different levels.
The organism as a tensegrity structure
An important property of tensegrity is that it does not vary with respect to macro-level. The property seems to be engaged at the atomic level, the galactic level and all the levels in between. Another way to say this is that tensegrity has a fractal quality. And so, the human organism can be understood as a tensegrity structure. This fractal quality which is present at the level of the atom, the molecule, the cell, the tissue, the organ and the organism, ultimately creates a surprising level of coupled harmonic coherence throughout the organism. When an arm moves, for example, the entire arm moves simultaneously with incredible coordination. Muscle activity is remarkably coordinated and coherent. Studies have shown that muscle contraction occurs in distinct synchronous quantal steps over entire muscle fibers.(18)
The implications for distribution of mechanical force have been briefly touched upon. Other implications regarding energy flow, coherence, and resonant transfer of information must be dealt with elsewhere.
It would appear that Gregory intuitively understood the property of tensegrity before it was formally identified, considering his systematic inclusion of the critical dynamics that are operational throughout the adjustorâ€™s entire body in the delivery of the adjustment. The concept is also present in his discussion of the adjustic force, which he described as utilizing a â€œclosed kinetic chain effectâ€ to conduct the work of the adjustment. It was Gregory that really fleshed out the distributive effects of the ASC throughout the entire structure. With the help of the Anatometer, Gregory and Seemann were able to measure how the misalignment in the upper cervical spine correlates directly with compensation and adaptation throughout the system. Our description of the measurable aspects of the ASC on the body: functional short leg, unleveling and transverse rotation of the pelvis, coupled movement of the axial skeleton away from the vertical axis, twisting and moving into one of the frontal planes, is exactly the distribution of stress which is being described in the tensegrity structure.
The rational biomechanical reasoning which has followed the extensive empirical investigations has made the practical delivery of the adjustment possible, even in complex cases where the â€œnumbersâ€ alone are not adequate to maximally and proportionately reduce the ASC. There are many cases that defy simple first or second class lever explanations, as anyone who sits in on Dr. Dentonâ€™s lectures must see. He often discusses the â€œsplittingâ€ of the adjustic force in out-of-pattern misalignments and type fours. This is why the term â€œgreatest resistanceâ€ is often used. There are innumerable potential â€œresistancesâ€ in every aspect of the system. The identified lever arms, and fulcrums represent practical approximations of the distributive and continuous tension and discontinuous compression inherent in the system. It is a very beautiful and useful abstraction of an unimaginable complexity.
It is this authorâ€™s hope that these ideas may lead to further understanding of the biomechanics underlying the physics of the adjustment as well as the biomechanics of the atlas subluxation complex.
1. Levin, Stephen M., â€œContinuous Tension, Discontinuous Compression: A Model of Biomechanical Support of the Bodyâ€. The Bulletin of Structural Integration. 8(1): Spring-Summer 1982.
2. Ingber, Donald E., â€œThe Architecture of Lifeâ€. Scientific American January 1998.
3. Ibid., Ingber 1998.
4. Ibid., Levin 1982.
5. Levin, Stephen M., â€œPutting the Shoulder to the Wheel: A New Biomechanical Model for the Shoulder Girdleâ€. www.biotensegrity.com/shoulder.html
6. Ibid., Levin.
7a. Kazarian, L.E., â€œCreep Characteristics of the Human Spinal Columnâ€. Orthop Clinics of North America, 6, Jan. 1975.
7b. Nachemson, A., Lumbar Intradiscal Pressureâ€. Acta Orthop. Scand., Suppl. 43, 1960.
7c. Tzaczuk, H., â€œTensile Properties of the Human Lumbar Longitudinal Ligamentsâ€. Acta Orthop. Scand. Suppl. 115, 1968.
8. Ibid., Ingber 1998.
9. Ho, Mae-Wan., â€œThe Rainbow and the Worm: the physics of organismsâ€. World Scientific, Singapore. 1993 p.93.
10. Ibid., Ho 1993 p.94.
11. Ibid., Ho 1993 p.94.
12. Clegg, J.S., â€œProperties and Metabolism of the Aqueous Cytoplasm and Its Boundriesâ€. Am J. Physiol. 246 (1984): R133-51.
13. Ingber, Donald E., â€œCellular tensegrity: defining new rules of biological design that govern the cytoskeletonâ€, Journal of Cell Science 104, 613 (1993).
(Ingber also cites Yen, A. and Pardee, A.B., â€œRole of nuclear size in cell growth initiationâ€. Science 204 1315-1317. 1979; Nicolini, C., Belmont, A.S., Martelli, A., â€œCritical nuclear DNA size and distribution associated with S phase initiationâ€, Cell Biophys. 8. 103-117, 1986: and Ingber, D.E., Madri, J.A., Folkman, J., â€œExtracellular matrix regulates endothelial growth factor action through modulation of cell and nuclear expansionâ€. In Vitro Cell Dev. Biol. 23, 387-394, 1987.)
14. Ibid., Ingber 1993 p.613.
15. Ibid., Ingber, 1993 pp. 623-624.
16. Ingber, Donald E., â€œTensegrity: the architectural basis of cellular mechanotransductionâ€. Ann. Rev. Physiol. 59, 593-595. 1997.
17. Wirtz, Hubert R.W., Dobbs, Leland G., â€œCalcium Mobilization and Exocytosis After One Mechanical Stretch of Lung Epithelial Cells.â€ Science 250 Nov 30, 1990 pp.1266-1269.
18. Iwazumi, T., â€œHigh Speed Ultrasensitive Instrumentation for Myofibril Mechanics Measurementsâ€. American Journal of Physiology 252 (1987) 253-62.