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Detailed Physical Examination for Laminitis
Abstract
This chapter presents physical examination descriptions relating to three categories of horses: those with potential laminitis; those with mild lameness; and those horses with typical painful manifestations of laminitis. Equine healthcare professionals along with the horses' owners need to be looking for, recording, and monitoring changes over time: horse's overall body condition and unusual stances, specific hoof changes, and level of pain. Laminitis ought to be on a primary rule-out list for any lame horse. Other physical examination considerations include: systemic effect on the vital signs and foot conformation. The well-documented sepsis cases that are at higher risk of secondary serious laminitis are gastrointestinal medical and surgical cases, pleuropneumonia, and retained placenta cases. The early physical signs of subclinical laminitis are primarily hoof changes of deteriorating quality, sole bruising, and increasing numbers of lesions. Potentially, all horses, sound or lame, need to be considered as having subtle laminitis.
... Without histology of the lamellae, it is not possible to confirm a diagnosis of acute laminitis 22 ; however, this histological confirmation is impractical in the live horse. Although lamellar biopsy is possible and has been described experimentally, 23 it causes lasting damage and is generally not considered necessary for the confirmation of laminitis, which is considered a clinical diagnosis in practice. ...
Background
Traditional radiographic measurements of distal phalanx (Pd) displacement based on the outer hoof wall are not useful for diagnosis of acute laminitis.
Objectives
We hypothesised that the distance between the inner hoof wall and Pd (‘lamellar lucent zone’; LLZ) measured on lateromedial digital radiographs would be increased in horses with acute and subacute laminitis compared with healthy horses.
Study design
Retrospective cohort study and in vivo experimental study.
Methods
Forelimb radiographs from 32 healthy and 18 laminitic mixed‐breed horses were analysed retrospectively. Laminitis was defined by at least two clinical signs (acute multi‐limb lameness, increased digital pulse amplitude and/or persistently warm hooves) for ≤3 days (acute), or >3 and ≤14 days (subacute) duration, without overt palmar rotation (≥3°), remodelling, or distal displacement of the Pd. Some laminitic limbs initially classified as acute were subsequently radiographed later in hospitalisation and also included as subacute. Twelve measurements including LLZ at proximal, middle, and distal locations were performed on 126 forelimb radiographs that met the criteria for acute laminitis (n = 39), subacute laminitis (n = 23) or healthy control (n = 64). A mixed effects linear regression model was used for comparisons and a receiver‐operator characteristic (ROC) curve was created for select measurements. Three horses were serially radiographed to study the impact of magnification and obliquity.
Results
The mean [95% confidence interval] LLZ (mm) was increased in acute and subacute laminitis compared with control in the proximal (acute = 8.8 [8.4–9.2]; subacute = 9 [8–9.9]; control = 7.3 [7–7.7]), middle (acute = 8.9 [8.5–9.3]; subacute = 9.1 [8.2–10]; control = 6.9 [6.5–7.2]), and distal (acute = 9.1 [8.5–9.7]; subacute = 10.2 [9.1–11.3]; control = 7.5 [7.2–7.8]) dorsal lamellar regions (p < 0.001). At a cut‐off of >7.5 mm for middle LLZ, sensitivity was 87% [73%–94%] and specificity 91% [81%–96%] for diagnosis of acute laminitis. Using the ratio of middle LLZ to distal phalanx cortical length, sensitivity was 95% [81%–99%] and specificity was 95% [87%–99%] (cut‐off >0.11). Magnification and obliquity affected absolute LLZ measurements but did not alter LLZ ratios.
Main limitations
No histological confirmation of laminitis.
Conclusions
LLZ measurements are potentially useful for radiographic diagnosis of acute and subacute laminitis.
A thorough examination and assessment of the equine foot forms an essential part of pre-purchase and lameness examination. Because foot problems are the most common cause of lameness, the examiner must have an accurate knowledge of foot anatomy, foot balance, and sources of foot pathology, and he/she must be willing to perform a "hands-on" approach to fully delineate abnormal-ities and pre-disposing factors for the development of lameness. Author's address: 16445 70th Street NE, Elk River, MN 55330; e-mail: turner@anokaequine.com. © 2006 AAEP.
Clinical situations' associated with high glucocorticoid levels in horses sometimes the development of laminitis. Laminitis is a clinical component of equine Cushing's syndrome associated with pituitary pars intermedia dysfunction. Laminitis reportedly develps when dexamethasone or triamcinolome is used to treat inflammation in horses. Substantial new data point to a role for inflammation in the development of laminitis, suggesting that glucocorticoids should inhibit its development. That glucocorticoids might cause laminitis is. paradoxical and lacks, a satisfactory explanation. Possible and plausible pathophysiologic, explanations for the risk of laminitis, that accompanies high glucocorticoid levels in horses have been proposed and are reviewed in this article.
All feet of 10 clinically sound mammoth donkeys (Group I) were radiographed to determine the appearance of the distal phalanx. The distal phalanges had blunted to concave-shaped dorsal solar margins which varied in appearance from slight to pronounced. The distal phalanges of the forefeet were wider than those of the hindfeet, and also were positioned a greater distance from the dorsal aspect of the hoof wall. The greater distance between the dorsal aspect of the hoof wall and the distal phalanges seemed related to the presence of a periosteal-like bony proliferation on the dorsum of the distal phalanx. This bony proliferation occurred in those distal phalanges which also had radiographic findings consistent with pedal osteitis. Next, all feet of 5 additional mammoth donkeys (Group II) that were to be necropsied for various reasons, were examined similarly to Group I, necropsied and found to have laminitis. Only 2 of these 5 donkeys had been lame; only one had rotation of the distal phalanges (in the forefeet). Radiographic data from the 4 donkeys without rotation seemed most similar to that found in those Group I donkeys which had periosteal reactions on their distal phalanges. Conclusions from this study were that: 1) feet of mammoth donkeys have some anatomic differences from those of domestic horses, 2) subclinical laminitis and pedal osteitis can occur in mammoth donkeys, 3) rotation of the distal phalanx occurs in some, but not all laminitic donkeys, 4) laminitic changes may be more pronounced in their fore than in their hindfeet, and 5) additional studies of donkeys need to be done, examining both proven normal and confirmed laminitic feet.
This study described a scoring system for the assessment of apparent neck adiposity and evaluated morphometric measurements for assessment of neck and overall adiposity. Twenty-one barren Thoroughbred mares, 13 Arabian geldings and 75 Welsh, Dartmoor, or crossbred pony mares, were clinically examined and blood samples analysed for insulin, glucose, leptin, and triglycerides. Bodyweight (BW), height, length, girth and abdominal circumferences, neck length, neck crest height and neck circumference were measured, and body condition scores (BCS) and cresty neck scores (CNS) were rated.Girth:height ratio had the strongest associations with BCS (rs = 0.64, P < 0.001 in horses; rs = 0.83, P < 0.001 in ponies) and blood variables, such as leptin (rs = 0.39, P = 0.024 in horses; rs = 0.68, P < 0.001 in ponies). Crest height and neck circumference:height ratio had the strongest association with CNS (rs > 0.50, P < 0.01) and blood variables, such as insulin (rs ⩾ 0.40, P < 0.05).Cresty neck score was useful in the assessment of neck crest adiposity and had physiological relevance, as demonstrated by associations with blood variables. Girth:height was the most suitable morphometric for assessment of overall adiposity, and either crest height or neck circumference:height was a suitable morphometric for assessment of apparent neck adiposity.
Reasons for performing study: A significant proinflammatory response is known to occur in the forelimb lamina after carbohydrate administration. As the hindlimbs are often less affected by laminitis compared with the forelimbs, we assessed hindlimb inflammatory response in the early stages of carbohydrate-induced laminitis to determine whether differences in the response existed.
Objective: To determine whether a similar proinflammatory response occurs in the hindlimb laminae to that previously reported for the forelimb.
Methods: Archived laminar samples from 12 horses administered 17.6 g of starch (85% corn starch, 15% wood flour)/kg bwt via nasogastric tube that were anaesthetised either after developing a temperature >38.9°C (DEV; n = 6) or at the onset of Obel grade 1 lameness (OG1; n = 6) were used in addition to 6 control horses (CON) that were anaesthetised 24 h after administration of water. Real-time quantitative polymerase chain reaction for selected proinflammatory mediators and MAC387 immunohistochemistry were performed. The data were analysed nonparametrically to compare groups.
Results: Increases in laminar MAC387-positive leucocytes and laminar messenger ribonucleic acid (mRNA) concentrations (P<0.05) for interleukin-1β, interleukin-6, cyclo-oxygenase-2, chemokine (C-X-C motif)ligand (CXCL)1 and CXCL8 were present in both fore- and hindlimb laminae from horses with OG1 lameness. Both CXCL1 and CXCL8 were also increased in forelimb and hindlimb laminae in the DEV horses.
Conclusions: Administration of carbohydrate resulted in a similar inflammatory response in the hindlimb laminae to that previously reported for the forelimb laminae. These findings suggest that other factors, such as weightbearing, may play an important role in the development of laminitis after a systemic inflammatory condition develops.
Potential relevance: Evidence of inflammation in the hindlimb laminae suggests that the hindfeet should be addressed in the septic horse at risk for laminitis; however, laminitis is often less severe in the hindlimbs due to other factors, such as weightbearing and hoof angle.
Endocrinopathic causes of laminitis may be a common underlying causative pathogenesis in first-opinion or field cases presenting with laminitis, as opposed to laminitis produced in inflammatory research models. This study aimed to determine whether evidence of an underlying endocrinopathy was present in horses presented for laminitis to a first-opinion/referral veterinary teaching hospital. A second aim was to compare the signalment of horses and ponies with laminitis with the equine hospital population during the same period. All horses presenting for laminitis at Helsinki University Equine Teaching Hospital, Finland, over a 16-month period were examined for an underlying endocrinopathy. Horses presenting for laminitis were compared with the hospitalized population over the same period. There were 36 horses presented for laminitis, and evidence of endocrinopathy was present in 89%. Of the horses showing an underlying endocrinopathy, one-third had a diagnosis of pituitary pars intermedia dysfunction, and two-thirds showed basal hyperinsulinemia indicative of insulin resistance, without evidence of hirsutism. Phenotypic indicators of obesity were present in 95% of horses with basal hyperinsulinemia without hirsutism. Compared with the hospital population during the same period, horses with laminitis associated with an underlying endocrinopathy were significantly older and more likely to be pony breeds. Our data support that endocrine testing should be performed on all cases of laminitis that do not have a clear inflammatory or gastrointestinal origin.
Equine laminitis is a highly debilitating disease of the foot. Despite its perceived importance, epidemiological characteristics are poorly understood and the true frequency of the disease remains unclear. The objective of this study was to retrospectively assess previous research to identify publications which provide the best evidence of the frequency of naturally-occurring equine laminitis. A systematic review of English language publications was conducted using MEDLINE (1950-2010), CAB Direct (1910-2010) and IVIS (1997-2010). Additional publications were included by searching bibliographies. Search terms included laminitis, equine, frequency, prevalence and incidence. Studies that allowed frequency estimations to be made for naturally-occurring equine laminitis were included. Information was extracted using predefined data fields, including 13 study quality indicators. Sixty-nine publications were appraised. Ten were considered to provide the most reliable information, estimating the frequency of equine laminitis ranging from 1.5% to 34%. Previous publications estimating laminitis frequency were generally poor quality. Laminitis frequency varied across publications however the publications included in this review focussed on many of the different underlying laminitis aetiologies and comparison of the frequencies between groups would be inappropriate. High-quality evidence-based studies are needed to estimate the true disease frequency in different equine populations.
Although much has been written about laminitis in the context of its association with inflammatory processes, recognition is growing that most cases of laminitis examined by veterinarians in private practice are those associated with pasture grazing, obesity, and insulin resistance (IR). The term 'endocrinopathic laminitis' has been adopted to classify the instances of laminitis in which the origin seems to be more strongly associated with an underlying endocrinopathy, such as either IR or the influence of corticosteroids. Results of a recent study suggest that obesity and IR represent the most common metabolic and endocrinopathic predispositions for laminitis in horses. IR also plays an important role in the pathogenesis of laminitis that develops when some horses or ponies are allowed to graze pastures at certain times of the year. The term equine metabolic syndrome (EMS) has been proposed as a label for horses whose clinical examination results (including both physical examination and laboratory testing) suggest heightened risk for developing laminitis as a result of underlying IR.
Chronic laminitis involves laminar morphologic changes resulting in digital collapse and can vary greatly in its clinical manifestation depending on duration, severity of lameness, and stability of the distal phalanx/hoof wall interface. Accurate assessment of the whole patient is mandatory and consideration must be given to signalment, occupation, and owner expectations, as well as history and etiology, which often predict the broad course of the disease. Diagnosis is made via physical examination with adjunctive serial radiographic evaluation and possibly venography. Eventual functionality of the foot is determined by structural integrity, which is dictated by the degree of morphologic damage of the soft tissue and bone architecture of the foot. Structures involved include the digital vasculature, the laminar/hoof wall interface, and the distal phalanx. Patient outcome is largely determined by the degree of instability between the distal phalanx and hoof wall, and the ultimate prognosis is further influenced by owner expectation.
The foot is the most common source of limb pain. The problems vary from simple to quite complex. An accurate diagnosis is dependent upon a thorough and detailed knowledge of anatomy and of what is available in the way of ancillary examination techniques. The correction of most foot problems requires an appreciation of a multitude of factors and a thorough knowledge of farrier science.
Case records of 202 horses treated for laminitis were reviewed with the intent of determining the long-term outcome and correlating this with digital radiographic findings and with the degree of pain associated with the laminitis. At long-term follow-up 57 horses had returned to athletic soundness (Group 1), 20 horses were intermittently lame (Group 2), 19 horses had permanent severe lameness (Group 3), 97 were dead (Group 4), and 9 were lost to follow up. Using simple regression analysis, functional outcome did not correlate with the degree of rotation (R2 = 0.004) or the presence of distal displacement (R2 = 0.139). Functional outcome did correlate with the clinical grade of laminitis (R2 = 0.504). Horses in Group 1 had significantly less distal phalangeal rotation (5.89 +/- 6.48 degrees) than did horses in Group 2 (11.10 +/- 8.19) and Group 3 (14.50 +/- 10.80), but were not significantly different from Group 4 horses (7.49 +/- 6.57). Of 96 surviving horses, 23 had evidence of distal displacement compared with 54 of 97 non-survivors. Based on these results, horses that develop distal displacement of the distal phalanx are more likely to die than are horses without distal displacement; however, the presence or absence of distal phalangeal displacement and the degree of distal phalangeal rotation cannot be used to predict the outcome of a horse with laminitis. Clinical assessment is a more reliable means of determining the final outcome and should be given precedence over radiographic findings.
Lameness examinations and radiography of the distal phalanx and associated soft-tissue structures of the front feet of 103 Thoroughbred racehorses, 4 to 9 years old, were performed to determine normal radiographic appearance and morphometry. Of 103 horses examined, 41 were used in the study that were without clinical signs of foot problems or lameness, had raced at least twice prior to radiography, and had raced at least twice more in the 6 months after radiography.
Lateromedial and dorsoproximal-palmarodistal radiographic views of each front distal phalanx were used to measure 28 bone and soft-tissue structures, and to evaluate 14 radiographic findings. Significant differences were not observed between left and right digits for any radiographic determination.
Mean thickness of the soft tissues dorsal to the distal phalanx, which provides an evaluation of the epidermal laminae, was 14.6 ± 1.0 mm when measured adjacent to the distal aspect of the distal phalanx. Most horses had straight, smooth hoof walls that were parallel to the dorsal cortex of the distal phalanx. The mean degree of palmar rotation of the distal phalanx was −0.5 ± 1.3, and none was rotated more than 4°.
The dorsal cortex was smooth and straight, without bone deposition or reaction in either digit for only 5 of the 41 horses. Active bone formation was seen unilaterally along the middle portion of the dorsal cortex in 7 horses, and along the distal portion of the dorsal cortex in 4 of the phalanges from 3 horses. New bone formation along the distal dorsal cortex was often accompanied by resorption of the palmar cortex. For 26 of the 31 horses without active bone deposition, smooth inactive bone formation along the midportion of the dorsal cortex was identified in 1 or both distal phalanges.
Bone at the solar margin of the distal phalanx was uniformly dense and finely trabeculated, without evidence of resorption or fractures. Severe irregularity of the solar margin was not found in any digit, and the margin of both phalanges was smooth in 8 horses. Various degrees of solar margin irregularity were observed in the other 33 horses.
The mean number of vascular canals within the distal phalanx was 8.4 ± 1.7, and the diameter of the largest canal was 3.4 ± 0.6 mm. A mean number of 2.0 ± 1.2 vascular canals was oriented parallel to the radiographic beam on the dorsoproximal-palmarodistal view, and these were termed end-on vessels, because they were visualized as radiolucent dots ≥ 1 mm in diameter in the central portion of the distal phalanx.
Racing performance of horses with subtle radiographic signs of laminitis (palmar rotation, hoof wall curvature or undulations, palmar cortical resorption, distal dorsal cortical bone deposition) was poorer than that of horses without these signs. These findings are suggestive of a subclinical laminitis condition, which may influence performance without causing overt clinical signs.
To determine prevalence and clinical features of pituitary pars intermedia dysfunction (PPID) in horses with laminitis.
Case series.
40 horses with laminitis.
Horses with laminitis that survived an initial episode of pain and were not receiving medications known to alter the hypothalamic-pituitary-adrenal axis were tested for PPID by evaluation of endogenous plasma ACTH concentration. Signalment, suspected cause, month of onset and duration of laminitis, Obel grade of lameness, pedal bone rotation, physical examination findings, results of endocrine function tests, treatment, outcome, and postmortem examination findings were recorded.
Prevalence of PPID as defined by a single high plasma ACTH concentration was 70%. Median age of horses suspected of having PPID (n = 28) was 15.5 years, and median age of horses without PPID (12) was 14.5 years. Laminitis occurred most frequently in horses with and without suspected PPID during September and May, respectively. Chronic laminitis was significantly more common in horses suspected of having PPID. In horses suspected of having PPID, the most common physical examination findings included abnormal body fat distribution, bulging supraorbital fossae, and hirsutism. Five horses suspected of having PPID had no clinical abnormalities other than laminitis. Seventeen horses suspected of having PPID that were treated with pergolide survived, and 3 horses that were not treated survived.
Evidence of PPID is common among horses with laminitis in a primary-care ambulatory setting. Horses with laminitis may have PPID without other clinical signs commonly associated with the disease.
Conformational traits are important in breeding, since they may be indicative for performance ability and susceptibility to injuries.
To study whether certain desired conformational traits of foals are related to lateralised behaviour while foraging and to the development of uneven feet.
Twenty-four Warmblood foals, born and raised at the same location, were studied for a year. Foraging behaviour was observed by means of weekly 10 min scan-sampling for 8 h. A preference test (PT) was developed to serve as a standardised tool to determine laterality. The foals were evaluated at age 3, 15, 27 and 55 weeks. The PT and distal limb conformation were used to study the relation between overall body conformation, laterality and the development of uneven feet. Pressure measurements were used to determine the loading patterns under the feet.
About 50% of the foals developed a significant preference to protract the same limb systematically while grazing, which resulted in uneven feet and subsequently uneven loading patterns. Foals with relatively long limbs and small heads were predisposed to develop laterality and, consequently unevenness.
Conformational traits may stimulate the development of laterality and therefore indirectly cause uneven feet.
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