Chronic laminitis: current treatment strategies

Laminitis is divided into four different phases: developmental, acute, subacute, and chronic. The focus of this article is on treating the laminitic horse after the cessation of therapy for the acute phase, that is, usually 2 to 4 weeks after the onset of clinical signs.

Ultrasound measurement of sole horn thickness in trimmed claws of dairy cows

OBJECTIVE

To determine whether ultrasound could be used to measure sole horn thickness in dairy cattle after claw trimming with an adaptation of the Dutch method.

DESIGN

Case series.

ANIMALS

24 adult Holstein dairy cows.

PROCEDURE

Cows were restrained in a standing position, and claws were trimmed with an adaptation of the Dutch trimming method. B-mode ultrasonography was then performed. The transducer was placed on the sole just caudal to the apex of the toe and immediately medial and parallel to the abaxial white zone. The inner margin of the sole was identified as a thin hyperechoic line. Soles were considered to be too thin if sole horn thickness, determined by use of ultrasonography, was < 5 mm.

RESULTS

Sole horn, underlying soft tissues, and the distal surface of the third phalanx were imaged in 151 claws. The inner margin of the sole could not be identified in 4 claws, and 37 claws could not be imaged because cows collapsed in the restraining chute. Mean +/- SD sole thickness for all claws was 71 +/- 1.3 mm. Only 1 sole was < 5 mm thick. The lateral front claws were significantly thicker than the medial hind claws.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that ultrasound imaging can be used to determine sole thickness in dairy cattle after routine claw trimming.

Radiographic imaging of the equine foot

Radiographic examination of the equine foot can provide the veterinarian and farrier with a wealth of information. Positioning and selection of exposure factors are of central importance if one is to produce radiographs of maximum diagnostic value.

Hoof capsule distortion: understanding the mechanisms as a basis for rational management

Understanding the basic mechanisms of hoof capsule distortion enables the clinician to unravel the sometimes complex mix of abnormalities, identify early warning signs, and manage existing problems more effectively. Distortion of the hoof capsule can often seem like a complicated puzzle by the time the veterinarian is called to examine the lame horse. Evaluating each of the components of the hoof capsule, both individually and as an integrated unit, allows the clinician to tease apart the tangle of primary and secondary problems and come up with effective options for countering or attenuating the forces responsible for the distortion. Using high-quality radiography and developing an eye for detail regarding the physical and radiographic characteristics of the foot allow the clinician to identify subtle abnormalities, thereby averting a clinical problem or addressing the problem while it is still reversible. With existing problems, developing these skills enhances the clinician's ability to interpret the degree of damage accurately and to devise mechanical solutions that create an environment in which healing and restoration of function are maximized.

A radiographic technique to assess the longitudinal balance in front hooves

The aim of this study was to validate a radiographic technique to measure objectively the longitudinal hoof balance in the horse. Ten left third phalanges (P3) obtained from front hooves and 19 left front hooves were used in order to assess the reliability of the radiographic technique and to identify any effect of rotation or alignment of specimens or distance between the X-ray machine and the radiographic cassette, in measuring P3s structures and balance related parameters. A rotational support was made to hold specimens in order to standardise some of the conditions of X-raying. The main axis of the frog was used as a marker for the sagittal plane of P3. Results showed that single radiographic measurements could have wide limits of agreement with actual measurements of the hoof (gold standard values). In order to limit errors we suggest the use of a combination instead of single parameters to assess balance. Rotation of the hoof is also to be controlled when a measurement of angles is needed. The radiographic technique used in this study can be used to objecticely measure balance parameters considered important in order to assess hoof balance.

A description of the motion of the navicular bone during in vitro vertical loading of the equine forelimb

Motion of the navicular bone might play a role in the development of navicular disease in horses but is difficult to asses. In the present study, 3-dimensional motion of this bone was determined using roentgen stereophotogrammetric analysis. Tantalum pellets were inserted, in vitro, in the bones of 6 forelimbs of mature Shetland ponies and kinematics were measured during vertical loading up to 2 kN. The motions of the navicular bone and coffin joint were limited to flexion/extension, there were no substantial out-of-plane motions. There was only little flexion between the navicular bone and the coffin bone, which was correlated (r = 0.66) with coffin joint flexion. There was substantial flexion between the navicular bone and the short pastern, which was highly correlated with coffin joint flexion (r = 0.97). We conclude that the navicular bone, generally, follows the coffin bone during coffin joint flexion, although there are small but consistent motions between the navicular bone and the coffin bone. These motions might play a role in the development of navicular disease in horses.

Subjective and quantitative scintigraphic assessment of the equine foot and its relationship with foot pain

It was hypothesised that in solar bone images of the front feet of clinically normal horses, or horses with lameness unrelated to the front feet, there would be less than a 10% difference in the ratio of uptake of radiopharmaceutical in either the region of the navicular bone, or the region of insertion of the deep digital flexor tendon (DDFT), compared to the peripheral regions of the distal phalanx. Nuclear scintigraphic examination of the front feet of 15 Grand Prix show jumping horses, all of which were free from detectable lameness, was performed using dorsal, lateral and solar images. The results were compared with the examinations of 53 horses with primary foot pain, 21 with foot pain accompanying another more severe cause of lameness and 49 with lameness or poor performance unrelated to foot pain. None of the horses with foot pain had radiological changes compatible with navicular disease. All the images were evaluated subjectively. The solar views were assessed quantitatively using regions of interest around the navicular bone, the region of insertion of the deep digital flexor tendon and the toe, medial and lateral aspects of the distal phalanx. In 97% of the feet of normal showjumpers, there was <10% variance of uptake of the radiopharmaceutical in the navicular bone, the region of insertion of the DDFT and the peripheral regions of the distal phalanx. There was a significant difference in uptake of radiopharmaceutical in the region of the navicular bone in horses with foot pain compared to normal horses. There was a large incidence of false positive results related to the region of insertion of the DDFT. Lateral pool phase images appeared more sensitive in identifying potentially important DDFT lesions. There was a good correlation between a positive response to intra-articular analgesia of the distal interphalangeal joint and intrathecal analgesia of the navicular bursa and increased uptake of radiopharmaceutical in the region of the navicular bone in the horses with primary foot pain. It is concluded that quantitative scintigraphic assessment of bone phase images of the foot, in combination with local analgesic techniques, can be helpful in the identification of the potential source of pain causing lameness related to the foot, but false positive results can occur, especially in horses with low heel conformation.

Doppler sonographic measurements of arterial blood flow and their repeatability in the equine foot during weight bearing and non-weight bearing

In six normal adult horses, pulsed-wave Doppler sonographic inspections were made of the left and right lateral palmar proper digital artery (LPPDA) of each thoracic limb. Using a two-period, crossover design with repeated measures, each LPPDA was inspected on four occasions throughout the day over a 7 hour period and, on each occasion, with the limb weight bearing and non-weight bearing. In comparison with the observations made during weight bearing, there were significant increases (P<0.001) in blood-flow velocities when the limb was non-weight bearing. There was no relationship between blood velocities and the time of day, the order in which the inspections were made, resting heart rate, age of the horse, or hoof angle. In both weight bearing and nonweight bearing, the Doppler waveform demonstrated a systolic peak followed by at least two diastolic peaks and an end diastolic plateau. Horses that moved least during sonographic inspections had the lowest co-efficients variation.

Morphology of the laminar junction in relation to the shape of the hoof capsule and distal phalanx in adult horses (Equus caballus)

The purpose was to investigate whether differences in equine hoof shape, which are inferred to alter foot function, are accompanied by differences in morphology of the laminar junction. Ten fore feet from adult horses were segregated into normal and low-angle groups, depending on the dorsal angle of the hoof wall. Twenty measurements of external hoof shape and four of the enclosed distal phalanx were tested for differences between groups, and for intragroup correlations. Three measurements of laminar morphology (spacing, orientation and degree of bend) were recorded for samples of up to 50 primary epidermal laminae at each of 20 sample sites. Sites were distributed over the foot in 5 circumferential columns and 4 proximodistal rows. Intergroup differences were investigated, as were correlations among sample sites of the laminar variables with the shape measurements. Results show differences in hoof shape between groups (but not bone shape) and laminar morphology. Six shape measurements are significantly different between groups: dorsal angle, medial and lateral angles, lateral sole width, solar circumference, and dorsal length. In the normal group, shape measurements show patterns of correlation among regions of the hoof, and between hoof and bone measurements. In the low-angle group, shape correlations occur largely within one region of the hoof (the heels) and in the bone measurements. Laminar spacing tends to be nonsignificantly greater in the low-angle group, while variances for laminar spacing and orientation are significantly greater in this group. Laminar spacing correlates with bone width and coronary circumference (CC) of the hoof in the normal group, but only with CC in the low-angle group. When taken as a whole, and interpreted in light of a model of foot mechanical function, the results appear to indicate a deterioration in structural coherence of the foot in the low-angle group.

Radiographic interpretation of normal skeletal variations and pseudolesions in the equine foot

Effective radiographic interpretation requires a veterinarian who is knowledgeable of equine limb anatomy and the various principles that affect the resulting image. The normal and its variations must be recognized and understood before the abnormal can be confidently identified as pathologic. Proper patient positioning and sound radiographic technique are mandatory if reliable diagnostic radiographs are to be produced. This review emphasizes equine foot radiographic variations of normal and pseudolesions that occur with commonly used radiographic views performed in equine practice.

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.

Ultrasonographic characterization of ovarian events and fetal gestational parameters in two southern black rhinoceros (Diceros bicornis minor) and correlation to fecal progesterone

A tremendous potential exists for the application of transrectal ultrasonography as a tool to enhance the captive management of endangered species. Reproductive study of two southern black rhinoceros (Diceros bicornis minor) females was performed daily to every other day for a approximately 60 day period to document ovarian changes, and three times weekly in early pregnancy to once monthly in late pregnancy in order to characterize changes in fetal parameters throughout gestation. All ovarian and fetal anatomical structures were measured in millimeters. The mean (+/- SD) length of the estrous cycle or interovulatory period was 26 +/- 1.4 days (n=2 cycles). Follicular growth rate of a dominant follicle was approximately 3 mm/day once the follicle reached 35 mm in diameter. Ovulation was observed to occur at a mean (+/- SD) follicular diameter of 49.5 +/- 2.6 mm (n=4) and within 48 to 72 h after observed estrus (n=2). Large ovarian structures [mean (+/- SD) diameter of 71.7 +/- 2.9 mm; n=3], considered analogous to equine anovulatory hemorrhagic follicles, were observed to form in the winter months and suggest seasonal periods of reduced fertility. Fecal progesterone assays confirmed ultrasonographic events. Although preliminary, the results of fetal sexing are presented and compared to the horse. Our data indicate that fetal eye or fetal foot diameter measurements can be used to accurately predict gestational age from about 2 months to term, providing useful information to managers of both captive and wild rhino populations. The ability to identify and quickly release animals in late term pregnancy in the wild and thereby reduce-abortions and neonatal mortalities in holding bomas is one potential practical conservation benefit of the fetal age predictive models.

Laminitis in a mature elk hind (Cervus elaphus)

Laminitis should be considered as a differential diagnosis in elk presenting with shifting leg lameness, reluctance to move, recumbency and hoof wall ridging. Eliminating the underlying cause and corrective trimming lead to a good prognosis for recovery.

Diagnosis and treatment of a fractured third phalanx in a Masai giraffe (Giraffe camelopardalis tippelskirchi)

A 10-yr-old male Masai giraffe (Giraffe camelopardalis tippelskirchi) presented with acute right forelimb lameness. Radiographs revealed a fracture of the medial claw of the distal phalanx penetrating into the distal interphalangeal joint. The giraffe was sedated while it was standing in a chute, and a wooden "hoof block" was applied to the lateral claw of the same limb. The animal was no longer lame 3 days after the procedure. Subsequent treatments included vitamin E, phenylbutazone, and glycosaminoglycans. For 7 wk it was maintained in a small holding yard on packed sand during the day and on deep sand during the night. The hoof block slowly wore down, and at 7 wk, it was placed back on concrete in the evening. At 8 wk, the block had completely worn off and the animal was no longer lame, but radiographs indicated minimal fracture healing. Radiographs performed at 7 mo indicated that there was still a radiolucent zone at the fracture line but calcification was evident at the margins of the fracture.

Use of radiography, computed tomography and magnetic resonance imaging for evaluation of navicular syndrome in the horse

Radiographic evaluation of navicular syndrome is problematic because of its inconsistent correlation with clinical signs. Scintigraphy often yields false positive and false negative results and diagnostic ultrasound is of limited value. Therefore, we assessed the use of computed tomography and magnetic resonance imaging in a horse with clinical and radiographic signs of navicular syndrome. Cadaver specimens were examined with spiral computed tomographic and high-field magnetic resonance scanners and images were correlated with pathologic findings. Radiographic changes consisted of bony remodeling, which included altered synovial fossae, increased medullary opacity, cyst formation and shape change. These osseous changes were more striking and more numerous on computed tomographic and magnetic resonance images. They were most clearly defined with computed tomography. Many osseous changes seen with computed tomography and magnetic resonance imaging were not radiographically evident. Histologically confirmed soft tissue alterations of the deep digital flexor tendon, impar ligament and marrow were identified with magnetic resonance imaging, but not with conventional radiography. Because of their multiplanar capability and tomographic nature, computed tomography and magnetic resonance imaging surpass conventional radiography for navicular imaging, facilitating earlier, more accurate diagnosis. Current advances in imaging technology should make these imaging modalities available to equine practitioners in the future.

[Ultrasonographic measurement of the sole horn thickness in bovine claw]

Ultrasonographic thickness measurement and imaging of sole horn and the encapsulated soft tissue layers was evaluated in 100 bovine claw specimens. The claws were trimmed and examined in longitudinal planes using a 7.5 MHz linear transducer. In each claw, ultrasonographic measurements of horn thickness of sole and distance from outer claw surface to distal phalanx surface were made at three marked points on the weightbearing surface. All claws were then frozen, transected and anatomical reference measurements were made after thawing. The sole horn, corium, subcutis and distal surface of the distal phalanx of all claws were clearly visualized. The sole horn had a heterogeneous hypoechoic appearance, the underlying soft tissue layer was predominantly anechoic. Corium and subcutis could be differentiated. Best imaging of these structures was achieved in claws with less than 10 mm sole horn thickness and soft sole horn. Statistical correlation coefficients of 0.88 to 0.91 were found for ultrasonographic and anatomical measurements of sole horn thickness. Therefore, B-mode ultrasonography proved to be an accurate, non-invasive technique for measurement of the sole horn thickness in bovine claws.

Radiological measurements from the feet of normal horses with relevance to laminitis

Lateromedial radiographic projections were made from the feet of 25 normal horses and 3 angles and 3 distances were measured. From these, normal ranges of calculated variables were obtained. The width and length of each foot and the height of the horse at the withers was also measured. In view of its possible importance in clinical laminitis, particular attention was paid to 'founder' distance (D). This is the vertical distance between the proximal limit of the dorsal hoof wall and the proximal limit of the extensor process of the distal phalanx. There were significant differences between breeds in D (P<0.05) and in wall thickness (P<0.01). Further studies investigated the effects of time, differing radiographic projections and different operators on D. D did not alter significantly (P>0.05) over a 6 week study period. It was concluded that errors due to radiographic beam obliquity were not of practical importance. Errors in measuring D between operators can be minimised by use of a standard radiographic technique. Although there was some variation in the value of D measured over time and with different operators, which could make the interpretation of early or subtle changes difficult, measurement variation was not considered to interfere with the assessment of large changes associated with severe laminitis.

Factors involved in the prognosis of equine laminitis in the UK

The significance of clinical and radiological parameters as prognostic indicators for laminitis, 'founder' and 'sinking syndrome' was studied using case records of 216 horses and ponies. Five animals were destroyed without treatment and were not included in the results of the study. One hundred and sixty-two (77%) animals returned to athletic soundness; 7 animals (3%) did not regain full athletic function, 42 animals (20%) died or were destroyed. Cases were assigned to 4 groups on the basis of initial clinical examination alone. These groups were laminitis, acute founder, 'sinker' and chronic founder. This grouping was found in itself to be the most important prognostic parameter which was studied. Stepwise regression analysis of the data from animals by group indicated that the radiological measurement of founder distance, was the most significant radiological prognostic measurement for acute founder cases. Less significant prognostic parameters were the severity of lameness, rotation angles, the presence of solar prolapse, and the number of feet affected. The height of the animal at the withers was not significantly related to outcome. The prognosis for horses was not significantly different from that for ponies.

Clinical presentation, diagnosis, and prognosis of chronic laminitis

This article focuses on the initial assessment of the horse affected with chronic laminitis. Variations in the clinical presentation and primary considerations in making a differential diagnosis are included. The elements of a clinical history essential to sound, therapeutic management, and prognosis are summarized. The physical and radiographic assessment of the digital lesions and diagnostic approaches to the common systemic aspects of the disease are presented and discussed.

Detection of a radiographically occult fracture of the lateral palmar process of the distal phalanx in a horse using computed tomography

A horse with a suspected injury of the distal phalanx was examined using radiography at day two and 19 after the onset of the lameness, with no definite diagnosis. Using computed tomography an incomplete fracture of the lateral wing of the distal phalanx was diagnosed at day 25. Based on computed tomography it was determined that the fracture probably did not enter the joint or involve the palmar cortex throughout its length which were of prognostic importance. The day following the CT examination a new oblique radiographic projection was made. In this radiography which was based on, and never would have been attempted without, the information about the geometric pattern of the fracture achieved by CT examination, a radiolucent area indicative of a wing fracture was seen. This report emphasizes the value of computed tomography in diagnosing a geometric complicated nonarticular oblique fracture of the palmar process of the pedal bone in a horse.

Ultrasonographic imaging and thickness measurement of the sole horn and the underlying soft tissue layer in bovine claws

Ultrasonographic imaging and thickness measurements of sole horn and underlying soft tissue layer were evaluated in 100 bovine claw specimens. The claws were trimmed and examined in longitudinal planes using a 7.5 MHz linear transducer. The sole horn, underlying soft tissue layer and distal surface of the distal phalanx of all claws were clearly visualized. The sole horn had a heterogeneous hypoechoic appearance; the underlying soft tissue layer was predominantly anechoic. Corium and subcutis could be differentiated. The best imaging of these structures was achieved in claws with less than 10 mm sole horn thickness and soft sole horn. Imaging of the dorsal wall structures was more difficult. In each claw, B- and A-mode measurements of horn thickness of sole and dorsal wall and distance from outer claw surface to distal phalanx surface were made at three marked points on the weightbearing surface and at one point on the dorsal wall. In 10 claws, CT-images were taken and the horn density was determined. All claws were then frozen, transected and anatomical reference measurements were made after thawing. Statistical correlation coefficients of 0.88 and higher were found for B-mode ultrasonographic and anatomical measurements of sole horn thickness. A-mode proved not to be useful for the sole horn thickness measurement. B-mode ultrasonography was carried out successfully in the claws of five living cattle.

Clinical study of toe ulcer and necrosis of the apex of the distal phalanx in 53 cattle

Clinical signs, causative factors, radiographic findings, type and duration of treatment or reason for killing were evaluated in 53 cattle (mean age: 5.3 years) suffering from toe ulcer and/or apical pedal bone necrosis. A total of 78 claws were affected. Four cattle suffered from a toe ulcer in one claw, 35 cattle showed osteolysis of the apex of the distal phalanx in a single claw and 14 cattle in two or three claws per cow. Overtrimming by means of a grinding disc and/or perforation of the sole was diagnosed as the major cause in 27 cattle (49%), laminitis in 30.2% and traumatic injuries in 11.3%. Radiography revealed a varying degree of osteolysis involving up to two-thirds of the pedal bone. Twenty-one cattle (39.6%) showing multiple toe disorders or involvement of one single claw with concurrent internal diseases were destroyed. In 23 cattle, the osteolytic bone was resected using a bone curette or hammer and chisel. Of these, the treatment was successful in 20 animals. The healing period ranged from 16-60 days when one claw was affected and from 43-53 days when two claws were affected. In five cattle, the digit was amputated.