Christophe Degueurce

Three-dimensional kinematics of the distal forelimb in horses trotting on a treadmill and effects of elevation of heel and toe

REASONS FOR PERFORMING STUDY Comprehensive understanding of the 3-dimensional (3D) kinematics of the distal forelimb and precise knowledge of alterations induced by dorsopalmar foot imbalance remains incomplete because in vivo studies performed with skin markers do not measure the actual movements of the 3 digital joints. OBJECTIVE To quantify the effects of 6 degree heel or toe wedges on the 3D movements of the 4 distal segments of the forelimb in horses trotting on a treadmill. METHODS Three healthy horses were equipped with ultrasonic markers fixed surgically to the 4 distal segments of the left forelimb. The 3D movements of these segments were recorded while horses were trotting on a treadmill. Rotations of the digital joints were calculated by use of a joint coordinate system. Data obtained with 6 degree heel or toe wedges were compared to those obtained with flat standard shoes. RESULTS Use of heel wedges significantly increased maximal flexion and decreased maximal extension of the proximal (PIPJ) and distal (DIPJ) interphalangeal joints. Inverse effects (except for PIPJ maximal extension) were observed with the toe wedges. In both cases, neither flexion-extension of the metacarpophalangeal joint nor extrasagittal motions of the digital joints were statistically different between conditions. CONCLUSIONS At a slow trot on a treadmill, heel and toe wedges affect the sagittal plane kinematics of the interphalangeal joints. POTENTIAL RELEVANCE Better understanding of the actual effects of toe and heel wedges on the 3D kinematics of the 3 digital joints may help to improve clinical use of sagittal alteration of hoof balance in the treatment of distal forelimb injuries.

Three-dimensional kinematics of the equine distal forelimb: effects of a sharp turn at the walk

REASONS FOR PERFORMING STUDY Sharp turns are suspected to increase expression of several distal forelimb lamenesses even at the walk but the biomechanical consequences of such a movement remain unknown. OBJECTIVE To quantify the effects of a sharp turn at the walk on the 3-dimensional movements of the distal segments of the forelimb. METHODS Kinematics of the distal segments were measured in 4 healthy horses invasively with an ultrasonic system. Three-dimensional rotations of the digital joints were calculated by use of a joint coordinate system. Data obtained for a turn at the walk were compared to those obtained in a straight line. RESULTS During the stance phase in a turn, the inside forelimb underwent an adduction that induced lateromotion and medial rotation in the distal interphalangeal joint and medial rotation in the proximal interphalangeal joint. These movements were maximal at heel-off and decreased during breakover as the hoof underwent a sudden lateral rotation. CONCLUSIONS Walking in a sharp turn affects the kinematics of the digital joints outside the sagittal plane. POTENTIAL RELEVANCE This knowledge offers the opportunity to derive hypotheses on biomechanical factors that could contribute to the pathogenesis of digital injuries and on consequences for rational shoeing.

Fourier analysis of trunk displacements: a method to identify the lame limb in trotting horses

The aim of this paper is to present a method allowing the identification of the lame limb in trotting horses. Using a 3-D kinematic analysis system, 13 sound and 25 lame horses fitted with 4 skin markers placed on the dorsal midline of their trunk were recorded while trotting on a track in the conditions of the routine lameness examination. The vertical displacements of the trunk markers underwent Fourier analysis. Results indicated that these displacements could be represented using only the first and second harmonics. From these two harmonics, indices were then developed. The sensitivity of these indices to the different types of experimental errors was also studied. Results showed that the values of the indices of the lame horses were relatively unaffected by the experimental errors. In lame horses, these indices allowed the quantification of the degree of the lameness, the identification of lame limb with a reliability > 95% and the characterisation of the type of trunk movements. These indices could be easily implemented in a computer program to provide objective information to the clinician or to be used as a first step in the development of an expert system. Moreover, these clinical tools may also be extended to other quadrupedal or bipedal locomotions.

A method to synchronise cameras using the direct linear transformation technique

The aim of this paper is to present a method which enables the recordings of cameras that are not equipped with a synchronisation system to be synchronised a posteriori. Using the Direct Linear Transformation technique, this method estimates the phase difference between two cameras by minimising the reconstruction errors of a moving point. Once the phase difference value is known, one of the recordings is chosen as a reference and the second one is synchronised to the first by cubic spline interpolation.

In vitro assessment of movements of the sacroiliac joint in the horse.

REASONS FOR PERFORMING STUDY Sacroiliac joint (SIJ) disease is associated with poor hindlimb action, lameness and poor performance in horses. However, little is known about the biomechanics of this low-motion joint. OBJECTIVES To determine in vitro the capacities of movement of the SIJ in the sagittal plane, and to test the effect of a sacrosciatic and sacrotuberal desmotomy on its stabilisation. METHODS Six anatomical specimens underwent cycles of flexion-extension of the lumbosacral joint (LSJ) before and after desmotomy. Kinematic triads were linked rigidly to the sacrum, spinous process of vertebra L5 and iliac wing. Angles were measured using a joint coordinate system based on anatomical frames. RESULTS The LSJ underwent regular movements of flexion and extension (overall mean +/- s.d. range 23.4 +/- 1.6 degrees). The only recorded movement of the SIJ was a nutation during LSJ flexion (overall mean +/- s.d. 0.8 +/- 0.5 degrees). Desmotomy induced an increase of that nutation (overall mean +/- s.d. 1.7 +/- 0.2 degrees). CONCLUSIONS AND POTENTIAL RELEVANCE Movements of the SIJ were small and coupled only with the flexion of the LSJ. The ligaments surrounding the SIJ have a strong effect on the stabilisation of this joint. Due to the limited amount of movement, its biomechanical study in vivo seems to be difficult. Further in vitro studies would be useful to determine the role of each ligament, to better understand the clinical consequences of the tears frequently observed during necropsy.

Three-dimensional kinematic technique for evaluation of horse locomotion in outdoor conditions

THE KINEMATICS of equine locomotion has been studied for quite some time. Muybridge and Marcy were the first to use the newly available photographic technology to document the gait of horses (MUYBRIDGE, 1887 and MAREY, 1894). Owing to the significance of lameness in horses and its economic significance for the horse industry, kinematics has been studied using increasingly sophisticated techniques adapted from human biomedical research (LEACH and DAGG, 1983; LEACH, 1987; CLAYTON, 1991). Horses present some particularities which make the study of their locomotion similar to that of the human athlete. Owing to their size and the amplitude of their movements, a broad field of view is required. Consequently, the captors have to be situated far from the horse subject, thus limiting the use of many human gait analysis systems. There are few kinematic analysis systems currently used for horse locomotion evaluation. They are divided into cinematographic, opto-electronic and video systems. Cinematography has been used in several studies. The locomotion of Standardbreds running at high-speed (12 m s l ) has been studied (FREDEKICSON and DREVEMO, 1972; DREVEMO et aL, 1987). The locomotion of race horses has been analysed using 16 mm high-speed cameras (LEACH et al., 1984; CLAYTON, 1989; HOLMSTROM et aL, 1994). The technique has also been applied to lameness evaluation (CLAYTON, 1986; GmTLER, 1988; KOBLUK, 1989). The advantages of this method are the high resolution and the frame rates (between 100 and 500 Hz) of the cinematographic cameras. However, this method requires film processing, thus increasing the cost and time of analysis. Moreover, cinematography appears to be quite expensive and the above studies were made with a single camera. The 3-I3 reconstruction and the simultaneous comparison between both sides of the horse were impossible.

Analyse des contraintes méthodologiques liées à l’utilisation d’un système d’analyse cinématique tridimensionnelle fondé sur le principe de la triangulation ultrasonore

Resume Le systeme d’analyse cinematique ZEBRIS CMS-HS calcule, en temps reel, les coordonnees tridimensionnelles de marqueurs cinematiques en utilisant le principe de la triangulation ultrasonore. Cependant, la propagation des ondes ultrasonores peut etre alteree par des facteurs exterieurs tels que les reflexions du signal, le vent, les variations de temperature. Pour chacune de ces conditions, les coordonnees 3D d’un systeme de six marqueurs immobiles ont ete mesurees, permettant le calcul d’angles et de distances theoriquement invariables. La precision du systeme a ete evaluee par la dispersion des valeurs autours de la moyenne calculee pour chaque serie de mesures. Dans les conditions standard du laboratoire, la precision des mesures etait de ± 0,14 mm sur les distances et ± 0,16° sur les angles. Des phenomenes de reflexion des ultrasons peuvent provoquer l’apparition d’erreurs systematiques de l’ordre de 0,2° et alterent la repetabilite des mesures. Le vent diminue la precision des mesures proportionnellement a sa vitesse. La temperature ambiante influe sur l’exactitude des mesures. En consequence, celle-ci doit etre correctement parametree. La precision des mesures diminue en eloignant ou en decalant les emetteurs par rapport aux microphones lorsque la distance excede 1,5 m. Cette etude permet d’evaluer les causes d’imprecision de mesure pour le systeme et de definir les limites d’utilisation de celui-ci.

The celebrated écorchés of Honoré Fragonard, part 1: The classical techniques of preparation of dry anatomical specimens in the 18th century.

The écorchés that Honoré Fragonard created between 1766 and 1771 have miraculously survived the ravages of time due to a technique of preparation which Fragonard never revealed. The present paper and a subsequent article aim to explain the classical methods used by anatomists of the 18th century (Part 1) and to throw light on the details of Fragonards method (Part 2). Anatomists of the 18th century who wished to preserve their dissections used a method of mummification, which has now fallen into disuse: drying after immersion in alcohol. This article explains the stages of the classical method utilized by French anatomists of the Age of Enlightenment. The cadaver was selected with care before the vascular system was injected with a colored mixture of wax, animal fat, and plant resins. The body was then dehydrated by immersion in a bath of alcohol, after which it was removed and positioned by means of a wooden framework, which held the body in the desired pose while the alcohol evaporated. The vessels were painted, and finally the body was varnished. Clin. Anat. 23:249–257, 2010.

Le patrimoine équestre des écoles nationales vétérinaires françaises

Trois des quatre ecoles nationales veterinaires francaises sont tres anciennes, et ont fonde historiquement leur developpement sur les soins aux chevaux. Elles ont ainsi accumule un patrimoine lie au cheval, pedagogique, scientifique, technique, et meme artistique tout a fait exceptionnel, dont un premier inventaire est dresse ici. La situation est heterogene avec une disparite des conditions de conservation, de traitement et de valorisation des collections. Ces patrimoines complementaires gagneraient a beneficier d’une gestion commune sur la base des normes des Musees de France.

Le cheval, un animal contraint

Les cavaliers utilisent un animal assez eloigne morphologiquement de son ancetre sauvage mais qui a garde de son evolution les adaptations qui avaient fait son succes dans sa niche ecologique. Sa proximite avec nous a favorise le developpement d’un fort anthropomorphisme vis-a-vis de cette espece. L’objectif de cette presentation est de montrer quels sont les atouts et les limites dont la Nature a pourvu cet animal, et de montrer comment l’art equestre tire avantage de ces particularites d’espece.