Project

«FCT – PTDC/CVT/113480/2009»

Equine Biomechanics: Kinematic and dynamometric analysis of the normal equine locomotion and comparison of the effect of different conformations and orthopedic treatments.

FOCUS OF THE PROJECT

The object of study of Biomechanics of Movement is the motor performance of living beings and has its conceptual foundation in the integrated knowledge of Morphology, Mechanics and Cybernetics.This integration results as an autonomic knowledge in relation to the mechanical and biological sources of the living systems.

The integrated development in the Biomechanics of those three sciences creates a self-knowledge, conceptual and operational. Simplifying one could describe Biomechanics of Movement as the study of output displacements (the kinematic of motion study) and output forces (the recorded kinetic study) of a biological system. The suitable combination of recorded kinematic and kinetic data provides access to the internal dynamics of the system.

Equine biomechanics adapts this study to the mechanical output in horses free from pathologies and can be used as an assessment tool to compare different conformations or treatments.

Biomechanical assessments can be helpful to objectively assess a horse’s potential aptitudes, identify the areas that need focusing in the study of different treatments of specific orthopaedic pathologies and in the training of both horse and rider. This is where we pretend to focus and will have a great economical impact in the global horse industry.

Some of the simple elements that are useful to study using biomechanical models are related with balance, symmetry, efficiency, power and coordination. The factors that can be analyzed are: the symmetry of gait and inter-limb coordination; the center of gravity position, its displacement and velocity; the stride length, its frequency and speed; the joint angles associated to joint stability; the power generation in the joints, the angular momentum on the ground, the rider posture and the rider influence.

Using the data obtained through the biomechanical analysis it is now possible of developing studies about the motor pattern behavior and its components, such as the coefficient of variation of data kinematics (linear and angular, displacements, velocities and accelerations), data kinetics (ground reaction forces) and data dynamics (joints moments, joint power) of the performance.

We will try to develop a new, more complete method for characterization of the equine locomotion, based in a high speed video 3D kinematical analysis coupled with the measure of the ground reaction forces and with the calculation of the centers of pressure patterns. This method contributes to our first objective: to study and compare different equine gaits (trot, passage and piaffé), different reining systems, to study the effect of the rider in those variables and to evaluate the result of different riding techniques (standing and sitting trot). The second objective of this project to research consists in the assessment of the real effect of the same horse shoe in different materials (steel and aluminum). The third objective consists in the comparison of the effects of a normal shoe and a full rolling motion shoe, as well as the effect of intra-articular treatment with corticosteroids and different horse shoes (full rolling motion shoe and a elevated heels shoe) for two different equine degenerative joint disease (fetlock and tarso-metatarsical).

It will be interesting to apply the actual possibilities of biomechanical analysis to equine locomotion if one develops a specific tool for the equine biomechanical model. This model will be a powerful analytical tool with more possibilities than the human observational capacity – including highly trained specialists – as a consequence of the number of data per second obtained, and the access to data impossible to obtain from direct observation, as for instance the articular angular momentum.

The results yield by this project will be original, as the coupling of a series of VICON high speed cameras with an AMTI force plate and a Footscan, in the best of our knowledge, has never been done in the horse.

The results of these researches will have different impacts in the horse industry. Firstly they will help veterinarians to have a better understanding of equine locomotion and consequently of the different treatments for specific equine orthopaedic conditions, which will help veterinarians in choosing the most adapted treatments concerning the studied pathologies and will have a positive effect in economics in the equine world. Secondly the results yield from these researches will help professionals of the equine world to have a better understanding of the equine movement and of the reasons justifying some different shooing and trimming techniques. Thirdly the knowledge originated by these researches will help horse trainers to better choose training strategies, as for instance riding techniques and daily demanded exercises. The combined action of all the previously mentioned advantages will help equine professionals to better manage resources in horse treatment, shoeing and trimming and in useful management plans and it would improve equine well being.

TECHNICAL DESCRIPTION

Critical literature review:

The kinematics of the different interlimb movements is a topic of relevance in anatomy, semiology, diagnosis and treatment. Equine surgeons and scientists are especially interested in this field of research because horses have a high incidence of locomotor diseases, which are the most important cause of consultation in equine medicine. This fact is confirmed by the high number of references in medical literature concerning this subject, which is significantly superior to the truncated 30 references retained to this literature review.

The recent progress of real time high speed image acquisition coupled with the emerging possibilities of digital computation led to a significant increase of possibilities in the study of normal locomotion, sports biomechanics and trauma.

Equine gait analysis is a subject of rapidly increasing interest in veterinary medicine, over the last years, and to which the international scientific community is looking attentively. Most of the articles cited in the bibliography were very recently published in high impact factor veterinary medicine international journals.

In the horse three-dimensional (3D) motion analysis has been done in order to achieve a better understanding of the kinematics of some joints, as the distal forelimb1, the metacarpophalangeal2 and the carpus3, the tarsus (normal and with synovitis)4. It has also been used for determination of the stance phase using high speed video data5 and for the assessment of the effects of a sharp turn at the walk6. The kinematics of the equine pelvis in response to sacroiliac joint loading was also studied using this technique7, as well as the basic kinematics of the saddle and rider8 and the effect of different head and neck positions on the caudal back and hindlimb kinematics9.

Moreover, some clinical studies focused on the effects on the distal forelimb of the simultaneous or individual elevation of the heels or toes at the walk or trot10, as well its consequences on calculated tendon strains10. The clinical effects of one specific orthopaedic horse shoe – egg-bar – on a sand track were also analysed11.

Some 3D motion analysis studies were also done in vitro. They concerned the qualification of articular rotations in the digital joints of the horse12, the assessment of the interphalangeal articular impact of asymmetric bearing13, the study of the normal three-dimensional behavior of the metacarpophalangeal joint and the effect of uneven foot bearing14 and tendon loads measurements in ponies15.

Similarly as with all other animals, when a horse puts his hoof in the ground the action of the gravity coupled with muscular tension exerts a force against the ground with, in consequence, exerts a reaction force on the horse’s hoof that is equal in magnitude but acts in opposite direction. This is the Ground Reaction Force (GRF). GRF can be measured using a force plate and the results originated are an objective analysis of locomotion impossible to achieve by visual observation.

The study of the GRF in equine research is well established and has been used to analyse special equine gaits (as the passage)16, riding techniques17, as well as the influence of draw reins18 and of the head and neck position in equine locomotion19.

In what equine clinical studies are concerned, GRF were used to objectively assess the musculoskeletal analgesic effect of anti-inflammatory drugs20 and to compare different horse shoeing techniques (egg-bar, flat shoe and application of a heel or toe-wedge)21. This technology was also used to study superficial digital flexor tendinitis22 and tendon and ligaments loads and strains21.

Recently in equine research effort has been made to couple the force plate with devices capable of collecting data from the four feet simultaneously over successive strides, with a regular gait, at controlled velocities. One of those devices was a treadmill, but ground composition influence cannot be evaluated23 and it differs from overground locomotion in biomechanical24 and energetic25 variables. A comparative analysis of treadmill and overground locomotion revealed significant differences23. Consequently treadmill exercise doesn’t seem to be the ideal method for analyzing equine locomotion. It has also been studied the insertion of an measure instrument between the hoof and the shoe26, but it could not allow a complete description of contact (vertical, horizontal forward-backward, horizontal transverse forces)27. More recently was developed a Dynamometric Horse Shoe, which could be embedded and could provide information on 3D GRF magnitude and repartition over hoof wall27, as well as information concerning tendon and ligament strains. This shoe has recently been used in a preliminary study to assess the effects of different tracks on locomotion28.

Another technique has been used to study equine locomotion – the measurement of the distribution of the vertical forces under the equine foot. Most of those studies focused on hoof balance and imbalance or special shoes29, but also in the effect of trimming and shoeing30.

The technology of calculation of the center of pressure allows to study temporal fluctuations of plantar pressures and to eventually perform an early detection of some anomalies responsible for sport specific pathologies or pathologies encountered in predisposed horses. This task is made easier if 3D motion analysis, GFR and center of pressure calculation are coupled and analyzed together. At our knowledge no previous study characterized equine biomechanics by means of the combination of high speed video 3D kinematical analysis, coupled with the measure of the ground reaction forces and with the calculation of the center of pressure. Moreover a correlation of locomotion and conformation, as well of biomechanics and some gait patterns, riding techniques, degradation of horse shoes, intra-articular treatments and specific types of horse shoes has never been done.