Hoof Capsule Research Articles

Quantitative morphology of the equine laminar junction in relation to capsule shape in the forehoof of Standardbreds and Thoroughbreds

Differences in hoof morphology have largely been underappreciated in the literature until recently, and it is these that hold the key to interpreting functional adaptation in the hoof. Primary laminar morphology correlates with hoof capsule shape; and breeds with different hoof shapes and loadings show different patterns of correlation. Seventeen measurements of capsule shape and 3 of primary epidermal laminae (PEL) morphology (spacing, orientation and curvature) were made on right and left front hooves from 27 Standardbred and 25 Thoroughbred horses, and tested for breed differences. Three laminar variables (spacing, orientation and curvature) were measured on each hoof for samples of 25 PEL in 5 circumferential and 4 proximodistal locations. Pairwise correlations of capsular and laminar measurements were compared within breeds. Significant correlations were mapped onto the 20 sampling sites. Capsule shape differed significantly between breeds in 7 measurements and in a multivariate test. Between breeds, PEL differed in orientation and spacing primarily at the medial quarters and heels, and in curvature at both quarters (P<0.05). Significant correlations between several pairs of capsule and laminar variables were found at sample locations that differed markedly between breeds. Laminar morphology, hoof capsule shape and correlations between them differ between Standardbreds and Thoroughbreds. These results support the concept that remodelling of PEL is, at least in part, stimulated and directed by varying stress or strain levels in the laminar junction. Understanding the biological responses of hoof tissues to stress should add to the ability to prevent lameness involving the hoof and maintain its health.

Radiological interpretation of the navicular bone

SummaryAcquisition of a sufficient number of high quality radiographic views is an essential prerequisite to accurate radiological interpretation of the navicular bone. This requires appropriate preparation of the foot, careful attention to limb position and to both centring and direction of the x‐ray beam, according to hoof capsule conformation. Artefacts are easily created. Potentially significant radiological abnormalities include: entheseiophytes at the proximomedial and proximolateral aspect of the bone; proximal or distal extension of the flexor border of the bone, distal border fragments, 8 or more large and variably shaped distal border radiolucent zones; discrete radiolucent areas in the spongiosa with or without detectable communication with the flexor cortex; new bone at the sagittal ridge; increased thickness of the flexor cortex; sclerosis of the spongiosa; and a bipartite bone.

Evidence-Based Treatment for Laminitis—What Works?

Acute or recurrent laminitis often results in marked structural or mechanical disruption of the hoof with rotation or sinkage of the coffin bone within the hoof capsule in affected horses or those predisposed to developing this complex and devastating disease. A complete knowledge and understanding of laminitis and its complex pathophysiologic cascade remains elusive despite the substantial time and effort that many scientists and clinicians have dedicated over the last few decades. As a result, preventive and therapeutic management strategies remain empirical and anecdotal, with little emphasis on evidence-based medicine. Evidence-based medicine involves integrating individual clinical expertise with external clinical evidence from systematic research to make the best possible decisions regarding patient management. Numerous and overlapping theories have been postulated for the pathophysiology of laminitis. Although beyond the scope of this discussion, the current most commonly discussed theories include vascular or ischemic, inflammatory, metabolic, enzymatic, and biomechanical. In reality, many of these pathways or others yet to be identified are likely involved in the complex cascade of acute laminitis. Substantial focused and relevant research is needed to advance our knowledge and understanding of this complex disease and to develop more effective preventive and therapeutic strategies based on sound scientific and clinical evidence.

Evaluation of Equine Laminar Vein Function: Harvesting, dissection and the use of functional methods to distinguish between veins and arteries

Introduction Pharmacological evaluation of the unique equine laminar microvasculature is crucial to understanding its role in health and in diseases such as laminitis. However, separating the distinctive characteristics of arterial versus venous components of this complex vascular network has previously proved to be extremely difficult. Encased in a hard hoof capsule, isolation of individual blood vessels presents a considerable challenge. Exacerbating this difficulty, the laminar venous network is adapted to sustain high intravascular pressures and consequently has thickened walls, making the normally straightforward visual distinction between arteries and veins problematic. Here we describe a novel harvesting and dissection method coupled with a functional analysis procedure that facilitates distinction of arteries and veins. Methods Laminar tissue was recovered from the hoof of euthanized, clinically normal horses by dissection at the coronary band and stored in cold Krebs–Henseleit physiological salt solution prior to further dissection in the laboratory to remove 2 mm segments of vessels 100–500 µm in diameter. Active length tension measurements were made to evaluate optimal conditions for experimentation, and based on the differences in contractility and appearance, an experimental protocol was set up to allow a) initial distinction between arteries and veins and b) in vitro pharmacological evaluation. Results Active length tension studies clearly revealed the presence of two populations of vessels distinguished by either a large or a lower maximal contraction that subsequent histological evaluation confirmed to be arteries and veins respectively. Functional distinction using relative contractility to 60 mM potassium salt solution then demonstrated equine laminar veins to have increased sensitivity to the agonist endothelin 1 (ET-1) compared to arteries. Discussion In vitro evaluation of laminar vessels is possible despite anatomical obstacles. Furthermore, a clear distinction can be made between laminar veins and arteries using functional characteristics providing vessels of a similar size range are selected. Utilising these novel procedures, investigators can unambiguously analyse the pharmacological characteristics of equine laminar veins and arteries to decipher the physiological mechanisms responsible for the control of laminar blood flow.

Der Einfluss der Sohlendicke auf die Thermoisolation der Hornkapsel beim Equiden

Lameness that appears after hot-shoeing is an issue the farrier is often blamed for. The aim of this study was to investigate the thickness of the sole at which it is possible to measure a change in temperature within the hoof capsule. In addition it was aimed to measure what change in temperature causes damage to the corium of the sole. The front limbs of 20 horses, aged between 2 and 17 years old and of differing breed and size, were cut off at the carpal joint immediately after euthanasia. The experiment involved a simulation of routine conditions during hot-shoeing such as fitting the shoe on the hoof by branding. Branding was continued until a significant change in temperature was observed. The temperature described as “critical” in histological studies so far (51 degrees C with a branding time of 3 minutes) was achieved with a with a sole diameter of x - < 5.4 mm (s = ± 1, 5 mm). Damage to the tissue (extravasation, change in structure such as deformation of the cells and their nuclei) was found during histological examination of these samples which were taken from the sole with a diameter of 4 mm or less. The k- parameter of the horn analysed by the flash-method was 0,2 W / K*m, which means Horn has a very poor thermal conductivity. The well-known, highly effective thermo-isolating characteristic of the horn capsule was confirmed. Only when a sole has a thickness of x - < 5.4 irreversible thermal damage can occur when performing an excessively hot and long-lasting branding. In this way the results can help to answer questions in the area of forensic medicine. Therefore it is of great importance to perform adequate x-rays (perpendicular course of beam; labelling of the sole) in order to document the (actual) thickness of the sole after branding and the following occurrence of lameness. By measuring the thickness of the sole it can be told whether there is a possibility that damages on the corium may have been caused by hot-shoeing, at all, and thereby also tell the probability of this to occur.

The Influence of the sole - thickness of the Equine hoof capsule on its thermoisolation - capacity

The Influence of the sole - thickness of the Equine hoof capsule on its thermoisolation - capacity

In Vitro Assessment of the Equine Hoof Wall Strains in Flat Weight Bearing and After Heel Elevation

Abstract Horseshoeing is a common practice, but effects on the hoof wall are poorly understood. Strain gauges were used to document and compare hoof behavior in vitro during flat weight bearing and after artificial heel elevation. Ten front limbs of Thoroughbred race horses, shod with conventional flat shoes, were used. Eight strain gauges were symmetrically distributed around the toe, quarters, and heels. Each limb was mounted to a testing machine (Kratos K5002; Kratos Dynamometros, Ltda., Cotia-SP-Brazil) and subjected to a load equivalent to 30% of the donor's body weight. Strains (μɛ) were acquired by means of a computerized system and the results compared using Friedman and Wilcoxon statistical tests. There was greater strain variation when the heels were elevated. Compression predominated during flat weight bearing, with a tendency to horizontal traction after heel elevation. The changes in strain caused by heel elevation were not always symmetrical. Elevation of the heels tensed the toe and the medial quarter horizontally, increased load at the posterior portion of the hoof capsule, and hindered its expansion.

Clinical aspects of the equine proximal interphalangeal (pastern) joint

The proximal interphalangeal (pastern) joint is the diarthrodial articulation of the proximal and middle phalanges (referred to as P1 and P2 respectively) and is a low motion, high load joint.The middle phalanx is a compact bone, enclosed distally within the hoof capsule and coronary band. Numerous soft tissue structures cross the joint, including the common digital extensor tendon dorsally and the deep digital flexor tendon on the palmar aspect. The superficial digital flexor, along with the straight distal sesamoidean ligament, inserts on the distal palmar aspect of P1 and the proximal palmar aspect of P2. Sagittal support for the joint is provided by medial and lateral collateral ligaments which attach to collateral tubercles proximally and distally. Together, these soft tissue structures prevent over extension of the distal limb, and provide stability.

Flexural properties of the equine hoof wall

The equine hoof wall is a hard keratinous structure which transmits forces generated when the hoof contacts the ground to the skeleton of the horse. During locomotion, the hoof capsule is known to yield under impact resulting in an inward curvature of the dorsal wall and expansion of the heels. However, whilst researchers have studied the tensile and compressive properties of the hoof wall, there is a lack of data on the flexural properties in different locations around the hoof capsule. In this study the flexural properties and hydration status of the hoof wall was investigated, in two orthogonal directions, in different locations around the hoof capsule. The hoof was divided into three regions: the dorsal-most aspect (toe); the medial and lateral regions (quarters) and the heels caudally. Beams were cut both perpendicular and parallel to the axis of the tubules, termed transverse and longitudinal beams respectively. Differences in the mechanical properties were then investigated using three-point bending tests. There were considerable differences in the mechanical properties around the hoof capsule; transverse beams from the toe were 81% stiffer and 28% stronger than those from the heels. This corresponded with differences in the hydration of the hoof wall; beams from the toe had a lower water content (24.1±0.25%) than those from the heels (28.3±0.37%). Differences in the flexural properties are thought to be largely a result of variation in the water content. Mechanical data are further discussed in relation to variation in the structure and loading of the hoof wall.

Density and morphologic features of primary epidermal laminae in the feet of three-year-old racing Quarter Horses

To quantify the density of primary epidermal laminae (PELs) around the solar circumference and evaluate the relationship between regional PEL density and hoof capsule morphology in horses. Forefeet from nine 3-year-old Quarter Horse cadavers. Data pertaining to gross features of hoof morphology and PEL variables, including number, density, and distribution patterns around the perimeter of the hoof wall and number of bar PELs, were collected. Tissues of the laminar junction were examined histologically. No significant differences were found between left and right forefeet with respect to gross hoof morphologic measurements. Mean +/- SD number of PELs, including those at the bars of the hoof, was 551 +/- 30. Primary epidermal laminar density in the toe was significantly higher, compared with that in the quarter and heel regions, and was higher on the lateral aspect of the foot, compared with the medial aspect. Feet were significantly wider on the lateral aspect of the foot, compared with the medial aspect, as measured across the widest point of the solar surface. Histologic examination revealed atypical laminar morphology at the toe. Variations were detected in PEL density and morphology around the solar circumference of hooves from 3-year-old racing Quarter Horses. A better understanding of relationships between laminar density, laminar morphology, and gross morphology of the hoof capsule in different populations of horses may aid practitioners in diagnosis and treatment of disease involving the hoof wall in horses.

INTRAARTERIAL CONTRAST‐ENHANCED COMPUTED TOMOGRAPHY OF THE EQUINE DISTAL EXTREMITY

A technique for regional delivery of contrast medium to the foot of the horse to increase the diagnostic utility of computed tomography (CT) for the characterization of soft tissue structures within the hoof capsule was developed. An intraarterial catheter was placed under ultrasound guidance into the medial palmar artery at the level of the carpus to facilitate a steady-state infusion of iodinated contrast medium. Two 5 mm collimated contiguous acquisition CT scans were performed in 10 horses without lameness or radiographic evidence of distal sesamoid bone degeneration. CT examination was performed before and during regional arterial infusion of iodinated contrast medium administered at a rate of 2 ml/s. Cross-sectional area and mean pre- and post-contrast attenuation of the deep digital flexor tendon and the collateral ligaments of the distal interphalangeal joint were quantified from CT images. Soft tissue anatomy of the foot was also qualitatively characterized from pre- and postcontrast images. Catheterization was successful and without complication in all horses. The evaluated tendons and ligaments were clearly visible and had a small (8-20 Hounsfield Unit) but significant (P < 0.05, paired t-test) increase in attenuation during the steady-state infusion of contrast medium. This study should enhance the diagnostic potential of CT by providing baseline quantitative data for comparison with horses affected with soft tissue injuries in the distal extremity causing lameness that is alleviated with a palmar digital nerve block.

Changes in shape of the Standardbred distal phalanx and hoof capsule in response to exercise

AbstractThe aims of this study were to determine whether the equine distal phalanx changes in shape in response to exercise and to relate any osseous changes to those in the hoof capsule. Eighteen mature Standardbred horses were randomly divided into exercise and control groups. Exercised horses were jogged on a straight track at individual mean speeds between 4 and 8 m s− 1for 10–45 min, 4 days per week for 16 weeks. Both groups were similarly shod and pastured on the same field. Before and after the training period, each horse had digital photographs and magnetic resonance images (MRI) made of the right forehoof. Five linear measurements of the distal phalanx were recorded from the MRI and 24 measurements of the hoof capsule were made on the digital photographs. Small but significant changes in bone width (P = 0.039) were found in the controls and in two sagittal measurements of bone length (P = 0.039, 0.001, respectively) for the exercise group. These changes were slight and did not correlate with changes in shape of the hoof capsule, suggesting that the bone acts as a stable platform for supporting the capsule and withstanding loads.

Gastrointestinal Derived Factors Are Potential Triggers for the Development of Acute Equine Laminitis

Equine laminitis is the painful and debilitating condition resulting from cellular damage and inflammation of the tissues comprising the bonds supporting the pedal bone within the hoof capsule. One of the reasons why this condition is so complicated and enigmatic is its association with gastrointestinal disturbances, particularly a diet of lush grass at certain times of the year. Determining the link between disturbances to the hindgut flora and pathophysiology in the foot is one of the keys to preventing this condition. Therefore, one of the biggest challenges in equine laminitis research is to determine those events that precede the onset of the classical clinical signs of lameness, bounding digital pulses, and warm feet. A main theory for the pathogenesis of acute laminitis involves the development of vasoconstriction within the foot, which leads to ischemic and/or inflammatory tissue damage. Serotonin is an important constrictor mediator controlling digital blood flow. Certain equine hindgut bacteria produce amino acid decarboxylase enzymes that convert free amino acids into monoamines. Therefore, amines formed and released from the gastrointestinal tract are hypothesized to act as the link between the ingestion of lush grass and the digital ischemia thought to precede laminitis. Equine cecal contents contain a range of amines that are present in micromolar concentrations. Tryptamine is the most potent cecum-derived amine, causing vasoconstriction in vitro and in vivo through direct activation of serotonin receptors and displacing serotonin from platelets. Monoamines found in the cecum of the horse could potentially induce hemodynamic disturbances in the digit that result in laminar ischaemia, and so trigger laminitis.

The dynamics of hoof growth of the primitive Konik horses (Equus caballus gmelini Ant.) in an annual cycle

The annual growth rate of the horny wall of the hoof was investigated in 38 horses—31 mares and seven stallions. Experimental subjects were Konik horses kept in a conservative breeding herd. The horses hooves of both limbs: the right fore limb and the right hind limb were measured and next growth rate of the horny wall was analysed at five points of the hoof capsule. On the basis of Principal Component Analysis it was found that the subjects needed to be considered in three groups: three-year old mares, older mares and stallions. Next the growth increments were averaged in each investigated group and compared. The dynamics of hoof horn growth turned out to be the highest in the group of young mares, followed by the group of stallions and the group of adult mares. In the winter months the lowest growth increment of the hoof horn was observed in all the analysed groups. In the period of the elongating solar day, i.e. from May to July, the growth was rapid and reached the highest values. Starting from August the growth of the hoof horn decreased.

Laminitis and grass carbohydrate levels

The term laminitis literally means ‘inflammation of the laminae’ and is a potentially crippling disease of the equine foot. The laminae are interlocking projections which connect the hoof wall to the pedal bone within the foot, effectively suspending the weight of the animal within the hoof capsule. During a laminitic attack, the laminae become damaged to varying degrees, and their ability to connect the pedal bone to the hoof wall may be compromised; the degree to which this occurs depending upon the severity of the attack. In severe cases, the bond between hoof wall and pedal bone may be so weakened, that the pedal bone rotates downwards and may penetrate the sole of the foot. Some animals respond well to treatment, other less so and a proportion require euthanasia. Once horses have had a laminitic attack, even if successfully treated, they are likely to suffer from reoccurrence of the disease.

Pathogenesis and treatment of spontaneous quarter cracks - quantifying vertical mobility of the hoof capsule at the heels

Summary Spontaneous quarter cracks (Q.C) are defined as cracks, parallel to the horn tubules, originating at the coronary band, in the region of the quarters-heels of the hoof, due to internal trauma as opposed to external trauma (wire cuts e.g.). They consist in a fracture of the hoof wall, from the inside out, proximal to distal, and occur when the ipsilateral ungular cartilage (U.C.), expanding outwards in the loaded limb meets an excessively upwardly shunted hoof wall in the quarter-heel region (Sheared heel) as shown with resected hooves under load. Palpation and measurement of the free margin of the ipislateral, U.C. above the proximal border of the hoof capsule (H.C.) is clinically important in the evaluation and treatment of spontaneous Q.C. Feet with spontaneous Q.C. have a free U.C. margin of less than 15mm depending on the hoof’s size. Increasing the free margin of the U.C. is fundamental in the treatment of spontaneous Q.C. as the lesion originates from the inside out and no amount of crack debridement and fixation by itself will allow for free lateral expansion of the ipsilateral U.C. without it traumatising the coronary band. Lowering of an upwardly shunted heel/quarter can be achieved by special trimming and shoeing methods and /or by a full-wall depth sub-coronary grooving. The first allows for an average of ±7mm of instant hoof wall lowering at the affected heel relative to the ipsilateral U.C. and distal phalanx (D.P.). Finally the author studied the opposite effect; the amount of instant upward displacement of the hoof wall at the heels, relative to the distal phalanx, on the loaded foot with a 20mm heel raise. This was done in vivo by radiological means under standardised trimming and exposure conditions. Average, instant vertical displacement on 18 limbs amounted to 4,3 mm. These results call into question the effectiveness of some raised heel shoeing techniques which aim to change the phalangeal alignment between the D.P. and the proximal phalanges.

Slatted Floors and Solid Floors: Stress and Strain on the Bovine Hoof Capsule Analyzed in Finite Element Analysis

An established finite element model of a bovine claw was used to compare mechanical stress levels in a loaded model claw on different types of flooring. The following situations were compared: a claw standing on a solid floor, a claw standing on the edge of a short tie stand, and claws standing on slatted floors with slats of 28 and 40mm (wide) running parallel and perpendicular to the claw axis. Finite element analysis allowed visualization of stress peaks seen predominantly in the weight-bearing border of the dorsal abaxial wall and of the bulbar region and in the proximal axial wall. Maximum stress values of 13MPa were found in the model claw loaded on the solid floor and values of 18 to 22MPa were seen in the model claw loaded on the edge of the solid floor. On slatted floors, stresses increased in the situation in which the claw was not supported under the abaxial wall. Comparison between the other slatted floors showed little difference in amounts of mechanical stress. A clear distinction was detected between the solid floor with full claw contact and the slatted floors. From the point of view of the mechanical stress seen in finite element analysis, a large contact area between claw and floor, as seen in the solid surface floor, is preferable. When use of slatted floors is unavoidable, direction of the slats should run perpendicular to the direction of the walkway to prevent even more mechanical impact in certain footing situations.

The effect of hoof trimming on radiographic measurements of the front feet of normal Warmblood horses

The understanding of the normal position of the third phalanx (P3) and the distal sesamoid bone in relation to the size and shape of the hoof capsule in sound horses is helpful in the diagnosis of equine foot lameness. Some measurements on radiographs used to define the position of the pedal bone within the hoof capsule are significantly influenced by hoof trimming and the height of the withers. In this study, the front hooves of 40 Warmblood horses were radiographed twice, eight weeks apart, both before and after their hooves were trimmed by an experienced farrier. Using the software programme Metron PX, 22 parameters on the lateromedial view and 16 parameters on the dorsopalmar view were measured and the effect of hoof trimming and height of the withers were calculated, respectively. Some of the hoof parameters showed mild positive correlation with the height of the withers. In 70% of the horses the left hoof capsule and P3 were significantly larger than the right. Hoof trimming had a remarkable influence on hoof conformation, especially for parameters in the toe region. Of all the measurements that describe the position of the third phalanx (P3) in relation to the hoof capsule, the distances between the distal tip of P3 to the solar surface of the foot, P3 to the tip of the toe and P3 to the point of break-over showed the greatest differences before and after trimming. The database of the present study can be used by farriers and veterinarians as a guideline for routine and corrective shoeing of Warmblood horses.

Evaluation of a standardised radiographic technique of the equine hoof

Radiography of the equine hoof is often used to obtain a diagnosis. Quantitative interpretation, especially for research purposes requires high quality and accuracy of radiographs. The purpose of this study was to describe and evaluate a radiographic technique for the lateromedial (LM) and the dorsopalmar (DP) view of the equine hoof. Ten radiographs for each view from one cadaver limb and from both front feet in a standing horse were taken in order to assess repeatability of the radiographic technique. The method requires easy to use adjustable and portable equipment and strictly defined external radio opaque markers on the hoof capsule. The digitalised radiographs were processed and analysed with the software package Metron PX, measuring 13 parameters in the LM view and 10 parameters in the DP view, respectively. Results show that with few exceptions measurements of these parameters revealed a coefficient of variation that was smaller than 0.05. It was concluded that this easy to use standardised radiographic technique ensures excellent accuracy and repeatability for both the LM and DP view. Hence, this method provides an adequate tool for quantitative assessment of the equine hoof, inter- and intraindividually.

Use of a topical disinfectant as part of a hoof care programme for horses with diseases of the hoof capsule

Twenty-three horses with persistent hoof horn defects were treated topically with a hoof disinfectant as part of a hoof care programme for a year. The active ingredients of the disinfectant...