PubMed Health⌕ Search

Biomedical subjects

D H Leach

Publications and source records attributed to D H Leach.

35 records · Page 2Linked to original sources
PubMed1984

Relationship between intervertebral joint morphology and mobility in the equine thoracolumbar spine.

The anatomical features of 21 equine thoracolumbar spines, obtained from horses with clinically normal backs, were examined and the results compared with recent data on the mobility of the joint complexes of the horse's spine. The thoracolumbar spine can be divided into four regions based upon the morphology of the joint complexes: the first thoracic intervertebral joint (T1-2), the cranial and mid thoracic region (T2-T16), the caudal thoracic and lumbar region (T16-L6) and the lumbosacral joint. The mobility of the intervertebral joints in each of these regions can be related to their morphology, particularly the shape, size and orientation of the articular facets and the presence and frequent fusion of the lateral joints of the lumbar spine. The shape and thickness of the intervertebral discs also appear to be of importance.

Animals↗
PubMed1984

Standardised terminology for the description and analysis of equine locomotion.

Terminology for the analysis of equine locomotion is reviewed and the most appropriate terms selected for use by research workers in this field. Each cycle of limb movement comprises a stance phase, when the hoof is in contact with the ground, alternating with a swing phase. The stance phase is subdivided at the mid-stance position into an initial decelerative phase followed by a propulsive phase. When the stance phases of different limbs occur concurrently, the term overlap refers to the duration of simultaneous ground contact. Single support is the term used to describe the phase when the limb is in its stance phase unaided by any other limb. A gait consists of a limb coordination pattern repeated at each stride. The start and finish of the stride must be designated as a prerequisite to the determination of stride length, stride duration and stride frequency. In asymmetrical gaits, such as the gallop, the stride as a whole will have a stride stance phase, when one or more limbs are in contact with the ground, and a suspension phase. In symmetrical gaits, such as the trot and pace, the stride consists of left and right stance phases and suspension phases. Advanced placement and advanced lift off measure the time between ground placement and lift off respectively of consecutive limbs. The line of motion indicates the progressive movement of the centre of gravity in the X-Y plane. Measurements in th Y-Z plane, such as line gait and overcrossing, describe the ground placement of the hooves relative to the line of motion. Diagonal width is the distance between diagonal limb pairs in this plane.

Animals↗
PubMed1984

Degradation of annular gap junctions of the equine hoof wall.

Annular gap junctions interiorized within cells of the stratum spinosum of the coronary border of the equine hoof were degraded by two methods. Some were autophagocytized and some appeared to fuse with lysosomes to form heterophagosomes. Structural changes of partially degraded annular gap junctions included increased density of the enclosed cytoplasm, formation of filamentous or membrane-like material within the annular gap junction, and disruption of the circular or oval profile of the gap junction. The annular gap junctions are apparently incorporated into the fully keratinized cells of the stratum corneum.

Animals↗
PubMed1984

The effect of racetrack design on gait symmetry of the pacer.

A survey of a western Canadian racetrack determined the superelevation and transition curves to be less than the cited design standards. High-speed cinematography was used to film seven Standardbred pacers as they proceeded around one curve of the track at racing speed and for each horse 19 temporal stride parameters were obtained from these films using a film analyzer system. Average velocities were calculated and the mean stride length was found to vary from 5.08 m to 5.77 m. In all frames analyzed the hind foot was observed to contact the track surface prior to the ipsilateral forefoot and all horses displayed significant (p less than 0.05) contralateral asymmetry of some temporal stride parameters. Fifteen temporal stride parameters were significantly different (p less than 0.05) when compared between horses but only three temporal stride parameters were significantly different (p less than 0.05) when their values were compared between segments of the curved portions of the track. It is suggested that temporal gait asymmetry should not be used to judge the standards of racetrack design.

Animals↗
PubMed1984

Stride characteristics of horses competing in Grand Prix jumping.

An investigation was made of the stride characteristics of horses jumping 2 obstacles during a Grand Prix competition. One obstacle was a picket fence and rail 1.3 m high (fence 2), and the other was a coop and rail 1.52 m high (fence 11). Thirteen distance and 22 timing measurements of 17 horses were extracted from high-speed films, using computer-aided analysis. These data were used to compare takeoff and landing of the lead and nonlead legs, the thoracic limbs and pelvic limbs, and fence 2 and fence 11. Paired t-tests were used to compare means and a stepwise regression analysis was done for each fence, using the total horizontal distance jumped as the dependent variable. Stride timing and distance measurements did not differ (P less than 0.05) between the 2 fences . Each horse approached the fences in a moderately fast canter and, at takeoff , placed the nonlead thoracic limb earlier and farther from the fence than the lead thoracic limb (P less than 0.05). The nonlead leg stance phase lasted longer than the lead leg stance phase (P less than 0.05). The lead and nonlead pelvic limbs acted more in unison than the thoracic limbs and did not differ in their time of placement, stance phase duration, or position from the fence (P less than 0.05). The overlap of the stance phases of the pelvic limbs was greater than that of the thoracic limbs (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

Electron microscopic study of the veins of the dermal lamellae of the equine hoof wall.

The venous organisation of the dermal lamellae of the equine hoof wall of 18 pairs of forelimb hooves from clinically healthy horses was studied using plastic vascular corrosion casts, and scanning electron microscopic and histological techniques. A consistent pattern of venous organisation was observed in the dermal lamella of the toe, quarter and heel regions. The lamellar corium had an extensive interconnecting capillary network which drained into axially located veins of the primary dermal lamella. Many of the capillaries had a proximodistal orientation and most of those located at the interior third of the dermal lamella exhibited focal capillary enlargements. It was suggested that these enlargements may function to influence blood flow in normal conditions and in laminitis.

Animals↗
PubMed1983

A review of research on equine locomotion and biomechanics.

A review of the literature about equine locomotion and biomechanics is presented to summarise available knowledge and provide perspective to current and proposed research programmes. It is evident that much past research has failed to provide sufficient information on basic principles of these two disciplines and that information is now required before progress can be made on more applied research topics. However, useful contributions have been made in gait typology, analysis of racetrack surface and design and limb kinetics, kinematics and coordination.

Animals↗
PubMed1983

Guidelines for the future of equine locomotion research.

This paper describes the major areas that require investigation in equine locomotion and outlines a plan for such research in both the Thoroughbred and Standardbred. Fifteen topics for future investigation have been selected and given an order of priority. These topics deal with characteristics of normal locomotion, factors which influence locomotion, the epidemiology and economics of lameness and the clinical identification of lameness.

Animals↗
PubMed1983

Kinematics of the equine thoracolumbar spine.

At least three types of movement take place in the joint complexes of the equine thoracolumbar spine: dorsoventral flexion and extension, axial rotation and lateral bending. Using the standard right-handed Cartesian coordinate system, these movements may be defined as rotation about the x, y and z axes respectively. Except in cases of intervertebral fusion, all three types of movement occur in each joint complex of the equine back. The greatest amount of dorsoventral movement takes place at the lumbosacral and the first thoracic intervertebral joints. The greatest amount of axial rotation and lateral bending was measured in the mid-thoracolumbar spine at the level of the 11th or 12th thoracic intervertebral joints. The caudal thoracic and the lumbar spine is the least mobile region of the equine back. In the mid-thoracic spine, lateral bending was always accompanied by a "coupled" axial rotation. The presence of the rib cage stabilised the cranial thoracic vertebrae against axial rotation.

Animals↗
PubMed1983

Ultrastructure of the equine hoof wall secondary epidermal lamellae.

The ultrastructure of cells of the secondary epidermal lamellae from the hoof wall of 8 adult horses was described. Stages of progressive keratinization were not observed in this cell population. The morphologic features of cells of the secondary epidermal lamellae indicated that these lamellae were composed of nonmobile populations of cells and that primary epidermal lamellae moved past the secondary lamellae by breaking of the desmosomes connecting these 2 cell populations. Seemingly, debris present in the intercellular space between primary and secondary lamellae was a by-product of this remodeling.

Animals↗
PubMed1983

Mechanical properties of equine hoof wall tissue.

The mechanical properties of pigmented equine hoof wall tissue were determined for samples taken from the inner and outer portions of the stratum medium of the toe. Two properties, the modulus of elasticity and proportional limit, which are measures of the rigidity and yield point, respectively, of the tissue, were studied for samples compressed in 3 orthogonal directions. All samples tested were anisotropic. Inner wall samples were less rigid and had a lower yield point than outer wall samples.

Animals↗
PubMed1983

Extrinsic and intrinsic veins of the equine hoof wall.

The extrinsic and intrinsic venous drainage of the equine hoof have previously been poorly described. There is also an absence of information about the venous organisation of both primary and secondary dermal lamellae of the hoof wall. The purpose of this study was to describe the normal venous pattern of the horse hoof, especially that associated with the dermal lamellae of the wall. The venous organisation of 46 pairs of hooves from clinically healthy horses was studied using standard plastic vascular corrosion casts and histological sections. A consistent pattern of venous organisation was observed in the toe, quarter and heel regions. Veins in the proximal half of the wall corium form an exteriorly and an interiorly located venous plexus, while in the distal wall corium only an exteriorly located venous plexus is present. The wall corium of the toe and quarters is drained primarily by veins contributing to the coronary venous plexus and to the circumflex vein. In the heel regions this venous drainage network is supplemented by tributaries of the caudal hoof vein, independent superficial vein and anastomotic branches from the circumflex vein to the inner venous plexus. Because of this supplementary venous return the heel region is apparently better drained than other areas of the hoof wall. The wall corium is drained distally by the circumflex vein. The coronary venous plexus is composed of an exteriorly situated short superficial collecting venous plexus and an interiorly situated deep collecting venous plexus. The short superficial collecting veins, which drain the proliferating zone of epidermis of the coronary border, connect directly to the coronary and subcoronary veins. The deep collecting veins drain only the proximal wall corium. Most of the veins that drain the major portions of venous blood from the hoof are situated at the palmar aspect of the digit. These veins drain venous blood from the coronary venous plexus, the inner venous plexus and the superficial tributaries of the heel and bulb areas. The latter two venous systems receive venous blood from the sole and frog regions. Most of the veins of the hoof are valveless, except for tributaries of the coronary and subcoronary veins, and the caudal hoof vein and its tributaries. It is suggested that the weight-bearing force is utilised for effective return of venous blood from the digit.

Animals↗
PubMedDate not supplied

Transfer of deep circumflex iliac flaps to the tarsus by microvascular anastomosis in the horse.

Eighteen deep circumflex iliac flaps were elevated in healthy adult horses. Four flaps survived well when elevated as islands, but five orthotopic flaps and nine heterotopic flaps transferred to the tarsus and face failed. Technical reasons could explain the failure of the orthotopic flaps, but not the heterotopic flaps. Failure of the heterotopic flaps was apparently caused by the no-reflow phenomenon.

Anastomosis, Surgical↗
PubMedDate not supplied

The effect of exercise on the healing of articular cartilage defects in the equine carpus.

Arthroscopic surgery was performed on 12 horses (2-4 years of age) to create a 7 x 14 mm full-thickness cartilage defect in one radial carpal bone and in the contralateral third carpal bone. Six horses remained confined to a small paddock and six horses underwent a program of increasing exercise consisting of walking, trotting, and cantering for 13 weeks. All lesions showed evidence of healing at week 6 that progressed to more complete healing at week 13. There was no difference in the amount of repair tissue covering the defect. Histologically, the lesions healed with a combination of fibrous tissue and fibrocartilage. The repair tissue was significantly thicker in the exercised horses but there was no difference in repair quality. It was concluded that radial carpal and third carpal lesions have an equal ability to heal and that early postoperative exercise is not detrimental to the repair tissue within these carpal cartilage defects.

Animals↗
PubMedDate not supplied

Comparison of corneal epithelial wound healing after photorefractive and lamellar keratectomy.

BACKGROUND: The rate of corneal epithelial wound healing may be determined, in part, by the characteristics of the stromal surface. The excimer laser has the ability to produce a highly uniform ablated surface, which may facilitate reepithelialization after photorefractive keratectomy (PRK). METHODS: The rate of corneal epithelial wound healing after excimer laser PRK was compared with the rate of reepithelialization after manual lamellar keratectomy. Ten rabbits received a 4-mm diameter ablation in one eye (fluence = 160 mJ/cm2) and a shallow, 5-mm diameter, manual lamellar keratectomy in the contralateral eye. At 0, 4, 8, 12, 24, 36, 48, 60, and 72 hours after wounding, sodium fluorescein was instilled, and photographs were taken, converted to video images, and digitized. Wound area was calculated for each time point and converted to wound radius; the slopes of the wound radius, plotted over time, were compared to determine rates of healing. Scanning electron microscopy was performed immediately after wounding to examine surface regularity. RESULTS: By 24 hours after wounding, corneas that had undergone PRK demonstrated a significantly faster rate of epithelial wound healing compared with eyes that underwent lamellar keratectomy (33.4 +/- 1.9 microns/hr vs 27.8 +/- 1.4 microns/hr, respectively, for 12 to 72 hours) (p < 0.0001). Scanning electron microscopy showed greater stromal surface irregularity in the corneas that had undergone lamellar keratectomy, compared with the laser-ablated corneas. CONCLUSIONS: This study demonstrates that the rate of epithelial wound healing is significantly faster after excimer laser PRK than after lamellar keratectomy in the rabbit. Variations in surface regularity and wound edge profile may contribute to differences in wound healing.

Animals↗