Every biological entity is made up of systems upon systems, existing in symbiosis for the collective good. Even our own evolutionary story is one of endosymbiosis. Bacteria interacting with other organisms to create more powerful systems, held together by “some kind” of connective tissue.
Bio-tensegrity helps us to understand why the whole is greater than the sum of its parts as synergy begets efficiency over millennia of self-organisation. Until now we have tried to understand pathological causation by breaking down systems into their simple mechanics, perhaps losing sight of the complexities of the integration of each sum and its relationship with an even wider system. When we begin to look at the entire system, yes it becomes complexed, but long-term system wide soundness is achievable with integrative system wide repair, perpetuation is ended with creating system wide neuro-musculoskeletel harmony.
These concepts are the basis of studies into kinetic chains and myofascial trains, Levin et al (2017) described closed kinetic chains as modular units, within wider system units, responsible for organism wide locomotion. Every part of an organism is intertwined with every other, right down to a microscopic level. The complexities of the relationships between the units mean the organism can react to external stimulus much quicker than the capabilities of the nervous system allow. It also means that physiological dysfunction within any part of any unit has direct effect on that unit, the wider system units and the entire organism.
kinetic chains and myofascial lines are a way of understanding equine locomotive pathogenesis in a deeper and more integral way. Considering the position and orientation of every anatomical point, along each myofascial line associated with the presenting pathology, potentially leads to primary, secondary and complimentary issues being addressed in unison, resulting in more complete treatment.
These may not seem like considerations for farriery intervention, but the hoof is simply one part of an extensive biomechanical system that is far too often compartmentalised. Recognising hoof morphology as a result of entire system wide state and orientation doesn’t detract from established interventions, rather it can add understanding to their efficacy and point toward extra professional intervention that will compliment, ultimately resulting in more complete resolution of symptoms. There is a need for the farriery industry to have a more integral view of its role, you can not change the orientation of the hoof without affecting its myofascial connections, its neural, vascular and epithelial relationship with the wider system. Conversely, not changing a dysfunctional hoof will predispose that same system to pathology.
The fibrous myofascial web that encompasses the entire body can be seen in this image as the myofascial lines extending all the way into the hooves.
Farriery, for the main, is concerned with locomotion, so myofascial trains and kinetic/muscle chains are important factors in modern and integrative farriery. These systems transfer pulling forces along musculoskeletal meridians too and from the hoof. The simplistic muscle-bone understanding of movement fails to explain the far more complexed reactions of the entire body to movement. Wolf's law expresses this as bones remodel to cope with the forces placed upon them, so how much more is the hoof going to respond to these same influences. It is this capability of the body to respond that means simple mechanics never quite answer the questions of pathogenesis.
The horses body can be considered as a tensegrity structure, a balance between compressive and tensile forces, where all of the points of the structure respond to any localised stress and the weakest point is where pathology will present, even if it is at the opposite end to the primary stress. This concept helps to explain perpetuation of pathologies and the common pathological chain of events after treatment of assumed primary pathology. If the treated anatomical point was the weakest point of the tensegrity structure but the primary stress is not relieved then the next weakest point may succumb. The myofascial lines are routes of strain throughout the horses body, the hooves being the point of contact with the ground are points at which stress is constantly applied to the tensegrity structure. Any other point at which stress can be applied to the horses entirety, for instance tack, rider, riding style etc can and will also affect the integrity of the whole and the weakest section may fail. We know that the hoof is a deformable yet integral part of this tensegrity structure which is why it is a useful tool in assessing the strains on the wider system by noting its morphology. Early signs of morphological changes to the hoof could be a sign of pathological changes within the wider system.
Even within the hoof we can see tensegrity principles having an effect on farriery related parameters.
The compressive forces of the GRF are transferred to tensile forces via the laminal attachment and the very makeup of the hoof on a cellular level is evolved to endure compressive and tensile forces and use them to dampen the forces of locomotion. The pedal bone is suspended in a network of tension while under constant compression.
Something important to remember when considering the role of fascial tissue and its transference of pull, is that it is plastic and not elastic in nature although it will suffer creep with strain over time. Stretched quickly it will tear, but it is this mechanical nature that provides its benefits. We can see within the equine digit how it plays a role in keeping structures in place and how tensegrity is used to support the fetlock for example.
The tendons, ligaments and annular ligaments of the digit hold up the fetlock like a suspension bridge. This image helps to show how any change in orientation will affect every structure within the digit. Lower the heels and the Deep Digital Flexor tendon (DDFT) will be under more tension, for example.
The role of the DDFT as a tensegrity structure has been recently quantified by Osborn et al (2019) which highlighted the importance of phalangeal orientation on its integrity and predisposition to exceeding its elastic limit. But that tendon is an extension of a muscle further up the limb, connected to a bone within a much wider system, so that change in orientation does not affect only the structures within the digit. The links between anatomical position and orientation of the hoof (or otherwise) and pathology, spread throughout the entire musculoskeletal system, with the formation of kinetic chains and the myofascial lines, through both direct myofascial tissue and through mechanical connections via bone junctions. The Myofascial lines are a comprehendible way of understanding the tensegrity nature of the organism as a whole, while kinetic/muscle chains are a mechanical way of understanding units within that organism. For the sake of concision we will concentrate on the hind of the horse as it has a closer working relationship with the trunk of the horse considering its direct skeletal link.
This image shows the complexed muscle system of the hind limb, no 12 being the deep digital flexor muscle with a tendon extending into the distal phalanx as mentioned earlier. Many of the muscles work as antagonistic pairs and their complexed relationships play a large role in joint stabilisation and the effective use of the stay apparatus (Schuurman et al 2003), correct orientation of the system means the most efficient relationships between the structures in their response to gravity. This is expanded on by Gellman et al (2019) which discussed the inefficiencies of incorrect orientation and the benefits of minimized energy consumption in correct orientation, relating to both the use of the stay apparatus and the initiation of locomotion. We can look at this image in a different way.
Looking at the stay apparatus of the horse as a series of levers and pulleys can help to understand both how it works as a tensegrity unit and how the position and orientation of the hoof as the point of stress on that tensegrity structure, can affect the whole system. Imagine the distal phalanx moves in the directions of the red arrows in the hind limb and then imagine the effect that will have on the all the cables up the limb. The hoof conformation that would follow those arrows is negative plantar angles (NPA).
Understanding this tensegrity principle and then adding the concept of myofascial meridian pulls, creates a hypothesis of posture being the connecting factor between NPA and the pathologies proven to be linked. What adds to the complexity is whether the posture is present to relieve higher pathologies or in response to the hoof orientation, considering that the stresses in tensegrity structures can transfer abstractly, the primary dysfunction could, in reality, be anywhere.
The list of pathologies associated with NPA follow the superficial dorsal myofascial line and NPA has been noted as presenting with a camped under posture (Mannsman et al 2010), a posture which can be directly affected by farriery intervention. Investigating this line and the effects of posture on its integrity could therefore aid in unravelling the causal tensegrity conundrum.
The “full body” lines could all potentially be affected by hoof orientation and therefore farriery intervention via myofascial tension.
So to ask the question again, what does bio-tensegrity have to do with farriery (And vice-versa)? Well everything! Especially considering that the hooves are the beginning and end of a full body closed kinetic chain. Farriery can directly affect orientation of the structures of the digit, which in turn can directly affect posture of the limb and so on, until suddenly the integrity of the whole horse is affected. Looking at the horse not as the conventional series of levers and pullies, but as an infinitely interconnected network, brings even more focus onto creating optimum orientation of its base, but also brings a new insight into just how abstract the possible influences on the hoof could be.
References
Myers. T, Anatomy trains: Myofascial Meridians for Manual Therapists
Schuurman SO, Kersten W, Weijs WA. The equine hind limb is actively stabilized during standing. J Anat. 2003;202(4):355–362. doi:10.1046/j.1469-7580.2003.00166.x
Gellman. K, Shoemaker. J, Rees. E, The importance of neutral standing posture in horses (Equus caballus), Personal Correspondance
Levin. S, Solorzano. S, Scarr. G, 2017, The Significance of Closed Kinetic Chains to Biological Movement and Dynamic Stability, Journal of body Work and Movement Therapies
Osborn. M, Blas-Machado. U, Kirejczyk. S, Uhl. E, 2019, Using Biotensegrity to Explain the Mechanically-Induced Lesions in Navicular Disease, FASEB