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P Pourcelot

Publications and source records attributed to P Pourcelot.

At least 19 recordsLinked to original sources
PubMed2004

Correlations between mean echogenicity and material properties of normal and diseased equine superficial digital flexor tendons: an in vitro segmental approach.

The objective of this study was to test the hypothesis that tendon echogenicity is associated with the material properties of the corresponding tendon site, especially in case of lesions, due to local changes in tendon matrix composition. Four normal and nine spontaneously injured equine superficial digital flexor tendons (SDFT) were isolated then ultrasonographically examined under tension, in a special device placed in a water bath. Ultrasonographic transversal images (7.5MHz linear transducer) of five segments along each tendon were digitized, and analyzed in order to measure the mean cross-sectional area (MCSA) and mean echogenicity (ME) of each segment. The tendons were then tested in traction until rupture in a testing machine. For each segment, stress and strain were determined throughout the test, and the elastic modulus (EM) was evaluated. The tendon lesions were also documented by histology. No correlation was found between ME and the material properties of normal tendon segments. At the rupture sites of the nine diseased tendons, ME was positively correlated with maximal stress and EM, whereas no correlation was demonstrated with maximal strain. Besides, a positive correlation was demonstrated between ME and both MCSA and EM, when the three metacarpal segments of the diseased tendons were considered. Although ME gives only rough information about tendon matrix structure, it does show, under these in vitro conditions, significant correlations with material properties of pathological tendon segments, which may improve the functional significance and therefore the prognostic value of the ultrasonographic examination of tendon lesions.

Animals↗
PubMed2004

Influence of individual competition level on back kinematics of horses jumping a vertical fence.

REASONS FOR PERFORMING STUDY: The costs and investments required for the purchase and training of showjumpers justify the need to find selection means for jumping horses. Use of objective kinematic criteria correlated to jumping ability could be helpful for this assessment. OBJECTIVES: To compare back kinematics between 2 groups of horses of different competition levels (Group 1, competing at high level; Group 2 competing at low level) while free jumping over a 1 m vertical fence. METHODS: Three-dimensional recordings were performed using 2 panning cameras. Kinematic parameters of the withers and tuber sacrale (vertical displacement, vertical and horizontal velocities), backline inclination and flexion-extension motion of the 3 main dorsal segments (thoracic, thoracolumbar and lumbosacral) were analysed. RESULTS: Group 2 horses had a lower displacement of their withers and tuber sacrale from the end of the last approach stride until the first departure stride (P<0.05). As a result, they increased the flexion of their thoracolumbar and lumbosacral junctions during the hindlimb swing phase before take-off (P<0.05). However, withers and tuber sacrale velocities were slightly modified. Group 1 horses pitched their backline less forward during the forelimb stance phase before take-off and straightened it more after landing (P<0.05), probably indicating a more efficient strutting action of their forelimbs. CONCLUSIONS AND POTENTIAL RELEVANCE: Because significant differences in back motion were found between good and poor jumpers when jumping a 1 m high fence, criteria based on certain back kinematics can be developed that may help in the selection of talented showjumpers.

Animals↗
PubMed2002

Effects of trotting speed on muscle activity and kinematics in saddlehorses.

A thorough knowledge of the horse's back and limb movements at different speeds is important in the design of training programmes and the prevention of speed-related injuries. The objective of this study was to investigate changes in muscle activity and kinematics of the trot with increased speed. To evaluate these effects, 4 Saddlehorses were recorded while trotting on a horizontal treadmill at speeds ranging from 3.5-6.0 m/s. The 3-D trajectories of skin markers on the left side of the horse and the dorsal midline of the trunk were established. Electrical activity was obtained simultaneously from 6 muscles using surface electrodes. Ten consecutive strides were analysed for each horse at each of the 5 velocity steps. The increase in speed resulted in a decrease in stride and stance phase duration, increased muscle activity and range of motion of the limbs, but a decrease in back movements. During the stance phase, the limbs appeared more loaded, which resulted in more flexion of the joints and higher excentric muscle activity. During the swing phase, the higher concentric activity of the muscles was responsible for an increased shortening of the limbs. Understanding the effects of speed on equine locomotion is a prerequisite for the development of training programmes.

Animals↗
PubMed2001

Effects of heel and toe elevation upon the digital joint angles in the standing horse.

Five sound mature horses, age 8-14 years, with toe angles 45.5-55.0 degrees were placed on a specially designed platform with only the left forelimb weightbearing, which allowed the successive production of 7 different conditions of foot orientation: neutral position (N), 5, 10, 15 degrees heel (H5, H10, H15) and toe (T5, T10, T15) elevation, performed according to 2 different sequences. For each condition, 2 lateromedial radiographs were taken to evaluate the metacarpophalangeal joint (MPJ) and both interphalangeal joint (PIPJ and DIPJ) angles, respectively. In addition, two-dimensional (2-D) kinematic recordings, using reflective skin markers placed laterally on the left forelimb joints, were performed. The value of each joint angle (JA) and its angular variation to N (AV) were considered for statistical analysis. For all JA and their AV determined radiographically, the condition effect was significant and the sequence did not influence the differences between conditions. The relationships between the JA and the conditions (in the sequence: T15, T10, T5, N, H5, H10, H15) were overall linear for the 3 joints. The maximal range T15-H15 was mean +/- s.d. 6.9 +/- 2.0 degrees for MPJ (dorsal angle decrease), 7.3 +/- 1.0 degrees and 29.5 +/- 1.8 degrees for PIPJ and DIPJ (palmar angle decrease), respectively. Contrary to JA and in spite of large variations in hoof conformation, AV did not show any significant horse effect. Wide differences were observed between the digital JA measured radiographically and from kinematics, which could be related to cutaneous displacement. Heel elevation induced elbow flexion, whereas a slight extension was observed with toe elevation. These movements, even slight (mean elbow angle amplitude: 3.6 +/- 1.3 degrees), may have consequences upon flexor tendon tension.

Analysis of Variance↗
PubMed2001

Three-dimensional kinematics of the proximal interphalangeal joint: effects of raising the heels or the toe.

The proximal interphalangeal joint (PIPJ) has always been considered as a low-motion joint with an almost constant angle during loading of the limb. Until very recently, its motion was not taken into account in kinematic studies in vivo. Recent in vivo studies yielded surprisingly high ranges of motion in this joint. The aim of this study was to measure, in terms of the 3 possible rotations (flexion/extension, collateromotion and axial rotation), the movements of the PIPJ in vitro during limb loading in a neutral position (500-6000 N) and after the addition of heel and toe wedges (6 degrees and 12 degrees). The joint coordinate system, as it was recently described for use in the horse, was used to compute the 3 components of rotation. With the hoof in neutral position, low-amplitude flexion movements (7.9 degrees) were observed. They were not associated with collateromotion or axial rotation. The flexion of the joint increased exponentially with load suggesting that, during the midstance phase, heavy loads are necessary to evoke substantial flexion. Raising the heels induced an early flexion of the joint with an increase of its total amplitude. Raising the toe produced an extension at 500 N, beyond which the amount of flexion was reduced. These results show that PIPJ flexion/extension during in vitro loading remains substantially smaller than suggested by in vivo studies based on skin markers. Raising the toe or heel directly affects the behaviour of this joint, but does not induce motion outside the sagittal plane. Hoof wedges are commonly used in clinical practice for purposes other than affecting PIPJ motion. In these cases, their biomechanical effects on this joint should be taken into account.

Animals↗
PubMed2001

Normal three-dimensional behaviour of the metacarpophalangeal joint and the effect of uneven foot bearing.

The purpose of this study was to quantify small amplitude rotational movements in the metacarpophalangeal joint (MPJ) of the horse and to measure the influence of asymmetric placement of the foot on these articular angles. Trihedrons, supporting kinematic markers defining a local frame, were screwed into the third metacarpal bone and the proximal phalanx of 4 isolated forelimbs. The limbs were loaded in a press, and the lateral or medial aspects of the foot were raised alternately by a 12 degrees wedge. The use of the joint coordinate system permitted the simultaneous and continuous computing of the 3 angles of rotation of the joint. During neutral loading, the extension of the MPJ (38.4 +/- 8.7 degrees) was associated with lateral axial rotation of the proximal phalanx (1.8 +/- 0.9 degrees). Addition of a lateral wedge induced medial rotation (-0.9 +/- 0.2 degree) and abduction (2.1 +/- 0.4 degrees) of the proximal phalanx. The opposite phenomenon was observed with a medial wedge. These quantitative results confirmed the combination of axial rotation and widening of the articular space on the opposite side to the raised part of the foot that had earlier been observed in semi-quantitative studies. Despite the high congruence of this joint, this study demonstrated the significant influence of uneven bearing of the foot on the three-dimensional (3-D) behaviour of the MPJ. Even though the amplitude of these movements remained small, their biomechanical effects should be considered to improve our understanding of MPJ injuries and to rationalise exercise management and corrective shoeing in the lame horse.

Animals↗
PubMed2001

Kinematic analysis of the symmetry of limb movements in lame trotting horses.

This study was undertaken to describe the symmetry of movements of fore- and hindlimbs in horses suffering from various spontaneous lamenesses. Two groups of horses were studied: 13 clinically sound horses and 24 lame horses. Using a 3-dimensional (3-D) kinematic analysis system, movements of both sides of each horse were recorded simultaneously while trotting on a track. The differences in motion between left and right homologous joints of each horse were quantified using symmetry indices based on an intercorrelation method. Symmetry indices obtained for each lame horse were then compared with those of sound horses. This comparison showed that the most sensitive lameness indicators were the symmetry indices of the vertical displacement of the proximal markers of the limbs. Symmetry indices of each lame horse were also compared with those of the other lame horses, using correlation coefficients to determine whether or not various lamenesses generate similar alterations of the locomotion symmetry. Values of these coefficients allowed 2 types of lameness to be distinguished. In 21 lame horses, the largest alterations in the symmetry of vertical movements were observed for the proximal markers of the limbs, which may reflect the supporting component of these lamenesses. In contrast, the asymmetries in vertical movements were more pronounced for the distal markers in 3 horses (one stringhalt and 2 carpal injuries), which may reflect the swinging component of these lamenesses. This cross-correlation method can be implemented easily in a computer programme and may represent a first step in the development of an expert system.

Animals↗
PubMed2001

Effects of treadmill speed on the mechanics of the back in the trotting saddlehorse.

Speed related changes in trunk mechanics have not yet been investigated, although high-speed training is currently used in the horse. To evaluate the effects of speed on back kinematics and trunk muscles activity, 4 saddle horses were recorded while trotting on a horizontal treadmill at speeds ranging from 3.5 to 6 m/s. The 3-dimensional (3-D) trajectories of skin markers on the left side of the horse and the dorsal midline of the trunk were established. Electrical activity was simultaneously obtained from the longissimus dorsi (LD) and rectus abdominis (RA) muscles using surface electrodes. Ten consecutive strides were analysed for each horse at each of the 5 velocity steps. Electromyographic and kinematic data were time-standardised to the duration of the stride cycle and compared using an analysis of variance. The back extended during the first part of each diagonal stance phase when the RA was active and the back flexed during the second part of each diagonal stance phase when the LD was active. The onset and end of muscle activity came earlier in the stride cycle and muscle activity intensity increased when speed increased. The amplitude of vertical movement of the trunk and the maximal angles of flexion decreased with increasing speed, whereas the extension angles remained unchanged. This resulted in a decreased range of back flexion-extension. This study confirms that the primary role of trunk muscles is to control the stiffness of the back rather than to induce movements. Understanding the effects of speed on the back of healthy horses is a prerequisite for the prevention and treatment of back pathology.

Animals↗
PubMed2000

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.

Animals↗
PubMed1999

Kinematics of the equine back: flexion-extension movements in sound trotting horses.

This study was undertaken to evaluate the flexion-extension movements of the back in a group of sound trotting horses. Using a 3-D kinematic analysis system, 13 clinically sound horses fitted with 5 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. These markers were used to calculate 3 back angles (thoracic, thoracolumbar and lumbosacral angle). These back angles were then filtered using Fourier series. To evaluate the repeatability of flexion-extension movements, the intra- and inter-individual variabilities were studied. The angle-time diagrams showed that the equine back extended during the first part of each diagonal stance phase and flexed during the second part of each diagonal stance phase. The ranges of motion were less than 4 degrees for the 3 back angles. The intra- and inter-individual variability values of maximal extension and maximal flexion time points were similar and extremely low. This demonstrates the high repeatability of the temporal pattern of flexion-extension movements of the back. Intra- and inter-individual variabilities of the range of motion showed that the back mobility varies more in-between horses than between trials of the same horse. Compared with electromyographic activities of back muscles reported in the literature, flexion-extension movements described in this study tend to show that, at a slow trot, trunk muscles act mainly to limit flexion-extension movements of the back rather than to induce movements.

Animals↗
PubMed1998

Asymmetry in placement of bilateral skin markers on horses and effects of asymmetric skin marker placement on kinematic variables.

OBJECTIVE: To evaluate asymmetry in placement of bilateral skin markers on horses and to determine effect of asymmetric skin marker placement on kinematic variables for trotting horses. ANIMALS: 10 horses for evaluation of asymmetry in marker placement; 1 horse for evaluation of effects on kinematic variables. PROCEDURE: Asymmetry in marker placement was assessed by attaching markers to horses and comparing radiographs of left and right limbs. An experimental model was developed to determine effects on kinematic variables; accuracy of the model was validated experimentally. Using kinematic data from a clinically normal trotting horse as reference data, effects of asymmetric marker placement on vertical displacement-time and joint angle-time diagrams were determined by use of the model. RESULTS: Asymmetry of placement was < 1 cm for markers on the distal portions of the limbs and < 2 cm for markers on the proximal portions. Asymmetric marker placement did not alter general shapes of the vertical displacement-time and joint angle-time curves. In most instances, largest differences in vertical displacement attributable to asymmetric marker placement were equal to or less than magnitude of the asymmetry of placement. Alterations in joint angle-time curves were mainly a result of shifting of the curves on the Y axis. Joint range of motion was only slightly changed by asymmetric marker placement, but maximum flexion and extension angles were greatly altered. CONCLUSIONS AND CLINICAL RELEVANCE: Some kinematic variables can be greatly altered by small differences in skin marker placement. Such effects should be taken into account when evaluating kinematic data for sound and lame horses.

Animals↗
PubMed1998

Mechanical correlations derived from segmental histologic study of the equine superficial digital flexor tendon, from foal to adult.

OBJECTIVE: To assess histologic variations of the equine superficial digital flexor tendon (SDFT) according to site and to horse age and activity, and to correlate these data with reported segmental mechanical results. SAMPLE POPULATION: Superficial digital flexor tendons isolated from 42 horses 0.5 hour to 23 years old. PROCEDURE: 7 segments of each SDFT were delimited and submitted for conventional histologic examination. Each segment was examined and graded for fiber undulation, cellularity, number and size of interfascicular connective spaces (ICS), presence or absence of focal and diffuse chondroid metaplasia, and differentiation of the dorsal (DB) and palmar (PB) borders of the tendon. RESULTS: Fiber undulation and cellularity significantly decreased with age. The proximal and middle metacarpal segment fibers were significantly less undulated and their ICS were smaller than those of the other segments, especially in old horses. Focal chondroid metaplasia developed from 5 years onward, mainly in the sesamoidean segments. Diffuse chondroid metaplasia was characteristic of the digital region in horses > 6 years old. The DB of the metacarpodigital region tended to differentiate into fibrocartilage in association with age. The PB was generally differentiated as nonfascicular dense connective tissue. Activity induced a decrease in the number and size of the ICS. CONCLUSIONS: The lesser undulation of the proximal and middle metacarpal segments fibers can be correlated to their mechanical behavior (stress-strain curve) and relative weakness within the SDFT. Focal chondroid metaplasia and fibrocartilage on the DB are normal features, related to the compression stresses undergone by the sesamoidean region of the tendon.

Aging↗
PubMed1997

Mechanical properties of pathological equine superficial digital flexor tendons.

The objective of this study was to mechanically characterise superficial digital flexor tendon (SDFT) lesions. Eight pathological SDFTs, isolated from 6 adult horses, were tested in traction until rupture (at 1 mm/s). The stresses and strains simultaneously undergone by each of the 7 segments of a tendon were determined throughout the test, and the modulus of elasticity of each segment was evaluated from the segmental stress-strain curve thus obtained. These mechanical data were compared to those obtained on 10 normal SDFTs. After the test, the tendinous segments were submitted to a histological examination in order to characterise the tissues. Three lesional categories (I to III, of increasing maturity), as well as the normal tendinous tissue, were defined and assessed quantitatively according to their extent in the histological sections. The most recent and severe lesions (categories I and II) were correlated with a large degree of hypertrophy (often above 200%) of the corresponding segments, with a resulting decrease in the stress at tendon rupture, and a slight decrease in the strain at tendon rupture in spite of a low modulus of elasticity (low stiffness). In contrast, the adjacent areas, less or not injured, underwent compensatory strains. This relative overstraining was especially critical with category III tissue, often present in the transitional areas between sound and severely injured segments. Here the modulus of elasticity was low whereas the hypertrophy was only slight. Therefore, the corresponding segments seemed to be the most fragile sites, and those most predisposed to recurring injury, in an injured SDFT.

Analysis of Variance↗
PubMed1997

Variability of the limb joint patterns of sound horses at trot.

The reproducibility of gait variables for sound horses is essential for the interpretation of their modifications by locomotor disorders. Therefore, the purpose of this study was to evaluate the variability of the limb joint angle patterns in a population of sound horses while they trotted in the conditions of the routine lameness examination (slow trot, just held by hand, on a track, outdoors). The kinematics of 14 French Saddle horses was recorded using a 3-dimensional (3D) kinematic analysis system. Angle-time diagrams were established in the sagittal plane and their intra- and inter-individual variabilities were evaluated for the whole stride. Horses spontaneously repeated tests at constant speed. The intra- and inter-individual variabilities were low. These values were different from one joint to another and they increased distally. The maximum values were reached by the fetlock and coffin joints. Inter-individual compared to intra-individual variability was 0.9 to 1.9 times greater. There was a high correlation between mean angle-time and mean individual diagrams established for the whole population. It was concluded that it is possible to repeat similar tests with horses trotting in the conditions of the lameness examination. In an homogeneous population, each horse adopts a constant angular pattern that is very close to that of other horses. Since mean angle-time diagrams established on a sound population are highly representative of each mean individual angle pattern, they can be considered as reference data for the further analysis of the pathological gait.

Animals↗
PubMed1997

Kinematic analysis of the locomotion symmetry of sound horses at a slow trot.

This study of the locomotion symmetry was undertaken to provide standard symmetry indices of a group of sound horses at the trot. Using a 3D data collection system, the kinematics of the limb joints of 13 clinically nonlame horses were recorded while trotting in the standard conditions of the clinical lameness examination. A kinematic symmetry indice based on an inter-correlation method was defined and applied to the vertical displacement-time and joint angle-time diagrams of the left and right joints of the horses. For each horse, the mean symmetry indice of each joint was calculated using values from 5 trials. For each joint, these means were then averaged. To evaluate the repeatability of the locomotion symmetry, the intra- and inter-individual variabilities of the symmetry indices were studied. The levels of symmetry of the markers of the trunk were generally lower than those of the limbs. Moreover, during the 5 trials these levels of symmetry were strongly variable but their mean values were very similar from one horse to another. In our experimental conditions the trunk presented a higher degree of freedom than the limbs. This high intra-individual variability indicated also that several trials are necessary to quantify the locomotion symmetry of a trotting horse. In the same way, a lower level of symmetry of the hindlimbs, compared to the forelimbs, was proved by their lower values of symmetry indices. As opposed to the supporting role of the forelimbs, the propulsive role of the hindlimbs may explain this feature.

Animals↗
PubMed1996

Segmental variations of in vitro mechanical properties in equine superficial digital flexor tendons.

OBJECTIVE: To determine the local variations of mechanical properties of the equine superficial digital flexor tendon (SDFT). SAMPLE POPULATION: 10 SDFT of adult horses, selected for absence of abnormality. PROCEDURE: Needles (with a dark marker at both ends) pinned perpendicularly through each tendon to delimit 7 segments. Each tendon was tested in traction until rupture; test was filmed, using an 8-mm video camera. For each image, the coordinates of the center of mass of each marker and the corresponding force were registered. The third-degree polynomial that best fits the stress-strain curve thus obtained was calculated by a least squares approximation. The modulus of elasticity (Emax) of each segment was evaluated as the maximum of the derivative of this polynomial. RESULTS: Mean rupture load of the 10 SDFT was 12,356 +/- 1,333 N. The strain at tendon rupture and Emax varied, respectively, from 8.1 +/- 1.3% and 1,002 +/- 161 MPa (sesamoidean region) to 12.5 +/- 1.7% and 1,189 +/- 63 MPa (metacarpal region). The values of the strain corresponding to Emax were remarkably similar along the SDFT (approx 5%). CONCLUSIONS: Emax appeared early homogeneous along an SDFT, although being slightly higher in the metacarpal region. The 5% strain corresponding to Emax could be the limit strain beyond which microlesions of the tendinous fibers begin to appear, this threshold being first reached during the traction test by the metacarpal segments.

Animals↗