Ultrasonographic percutaneous anatomy of the atlanto-occipital region and indirect ultrasound-guided cisternal puncture in the dog and the cat.

Cisternal puncture in dogs and cats is commonly carried out. This article describes the percutaneous ultrasound anatomy of the cisternal region in the dog and the cat and an indirect technique for ultrasound-guided cisternal puncture. Ultrasound images obtained ex vivo and in vivo were compared with anatomic sections and used to identify the landmarks for ultrasound-guided cisternal puncture. The ultrasound-guided procedure was established in cadavers and then applied in vivo in seven dogs and two cats. The anatomic landmarks for the ultrasound-guided puncture are the cisterna magna, the spinal cord, the two occipital condyles on transverse images, the external occipital crest and the dorsal arch of the first cervical vertebra on longitudinal images. Using these ultrasound anatomic landmarks, an indirect ultrasound-guided technique for cisternal puncture is applicable in the dog and the cat.

Scintigraphic pattern of uptake of 99mTechnetium by the cervical vertebrae of sound horses.

Lateral scintigraphic images of the necks of 12 show jumping horses, 12 thoroughbreds and 12 French trotters were evaluated. Custom-written automatic analysis software was used to segment the regions of the articular processes and vertebral symphyses from C3 to C7 and to calculate their mean radiopharmaceutical uptakes. The uptakes by the two sides of these sound horses were not significantly different, and the uptakes by the vertebral symphyses and articular processes were also similar in the three groups of horses, considering each vertebral level separately. In the thoroughbred race horses, the mean uptake by the C6/C7 symphyses was significantly higher than by C5/C6, and the mean uptake by the C6/C7 articular processes was significantly higher than by C3/C4 and C4/C5. These differences were not observed in the French trotters and show jumping horses, but they were observed when the data for the three groups of horses were combined.

Magnetic resonance imaging of a brain abscess in a 10-month-old filly.

The purpose of this paper was to correlate the magnetic resonance imaging (MRI) characteristics of a mature brain abscess in a horse with histopathologic alterations of brain tissue. Eight months after the onset of clinical signs, MRI of the brain of a 10-month-old filly was performed. A large space-occupying lesion in the right cerebral hemisphere was identified. This space-occupying lesion was delineated by a thick and well-defined capsule that was isointense to brain parenchyma on the T1-weighted images and with a markedly hypointense on the T2-weighted images. The identification of such a capsule is highly diagnostic of a mature brain abscess. The lesion seen on MR images was confirmed at necropsy where a large abscess of the right hemisphere was observed. Streptococcus zooepidemicus and Pseudomonas aeruginosa were isolated from the abscess. Based on histopathologic examination, the signal characteristics of the capsule on T1-weighted and T2-weighted images were found to be due to the presence of numerous hemosiderin-laden macrophages. These results are in agreement with previous studies on human patients. This report confirms the value of MRI in the diagnosis of equine brain diseases.

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.

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.

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.

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.

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.

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.

Concrete use of the joint coordinate system for the quantification of articular rotations in the digital joints of the horse.

A method is detailed allowing the computation of three-dimensional (3D) joint angles. Each joint of the equine digit is modelled as a sequence of three single axis rotary joints. The Joint Coordinate System was used; it involves a specific sequence of cardanic angles. The decomposition of the angles was chosen so that the three elementary angles coincide with the flexion/extension, passive abduction/adduction and lateral/medial rotations. The algorithms and kinematic procedures were described for the equine front digital joints. This method was tested in vitro on four forelimbs. For each limb, angle values were measured while the member was loaded by a press (from 500 to 6000 N). These tests were repeated while a wedge raised one part of the hoof (toe, heel, lateral and medial sides) in order to induce modifications of the angular patterns of the joints. This method allowed a precise quantitative determination of 3D joint movements. The modifications occurring with the wedges are clearly identified and confirm some previously published semi-quantitative observations. Moreover, this method provides a way to collect objective data on the functional anatomy of joints and could be used to study connective shoeing thoroughly. It may be directly applied to other species and may be used by researchers interested in discreet articular movements, especially occurring in other planes than the sagittal one.

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.

Kinematics of the equine back: a method to study the thoracolumbar flexion-extension movements at the trot.

This study was conducted to evaluate a method for quantifying the flexion-extension movements of the back of horses trotting on a track in the conditions of the clinical lameness examination. Using a 3-D kinematic analysis system, the successive positions of four markers placed at regular intervals between the withers and the tuber sacrale were recorded. To isolate the flexion-extension movements of the back, the positions of these four markers were recomputed in a trunk-related co-ordinate system of the horse. Then, for each frame, the equation of the third-order polynomial that best fitted the position of the four markers was determined. Using these equations, it was then possible to interpolate the vertical displacement of any point situated between the withers and the tuber sacrale. The accuracy of this method was evaluated using three additional markers placed between the four previous ones. The vertical displacements of these three markers were recorded and compared to the interpolated displacements provided by this method. The results showed that the experimental and interpolated values did not present any statistical difference except in the lumbar region. In this region, the general shape of the vertical displacement curve was conserved but magnified by 17%. This study showed that despite the weakness of the range of the flexion-extension movements of the equine back at trot, these movements can be quantified with reliability. This method was then used on a lame horse. The results obtained demonstrated the usefulness of this method to study the flexion-extension movements of horses suffering from various locomotor disorders.

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.

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.

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.

Kinematic symmetry index: a method for quantifying the horse locomotion symmetry using kinematic data.

This study was conducted to evaluate a method for quantifying locomotion symmetry at trot in sound and lame horses. Using a 3D kinematic analysis system, the kinematics of the limb joints of sound and lame horses were recorded. The differences in motion between the left and right homologous joints were then quantified using a symmetry index based on an inter-correlation method. This method was used to calculate the symmetry indices of the vertical displacements and angle-time diagrams of the joints of each horse. In order to evaluate the sensitivity of this method of quantifying the locomotion symmetry, the symmetry indices of horses suffering from the three main types of lameness (forelimb, hind limb and bilateral lamenesses) were compared with those calculated for a reference group of clinically sound horses. The symmetry indices calculated using this method were sensitive enough to distinguish different degrees of lameness. Except for symmetrical bilateral lameness, the indices obtained also allowed us to determine which of the fore or hind limbs were lame. The results of this study make it possible to consider potential applications of this method in research and clinical fields.