Simon N. Collins

Supporting limb laminitis.

Supporting limb laminitis poses a threat to all horses suffering from severe unilateral lameness. Despite its devastating effects, relatively little is known about the precise pathologic processes that lead to its development. This article reviews the potential mechanisms of supporting limb laminitis, and the authors present some preliminary data based on advanced imaging and computer-based modeling techniques aimed at further elucidating the etiology of this unique form of laminitis. Gaining a better understanding of the pathologic processes that lead to supporting limb laminitis is essential to enable the development of appropriate countermeasures to safeguard horses at risk of the disease.

The lamellar wedge.

In horses with chronic laminitis, an abnormal horn structure called the lamellar wedge develops within the lamellar region of the foot. This pathologic structure adversely affects normal foot function, and influences return to previous performance levels. Understanding the pathologic process that leads to the development of this structure is essential for correct supportive foot management of the horse with chronic laminitis. The ability to prevent or reduce the formation of the lamellar wedge may eventually lead to better outcomes in cases of laminitis.

Preventive health care and owner-reported disease prevalence of horses and ponies in Great Britain

This study aimed to describe the provision of preventive health care and owner-reported disease prevalence in horses and ponies within Great Britain (GB), and to assess geographical variations in health care provision. A cross-sectional survey was conducted, using a postal questionnaire administered to a random sample of veterinary-registered owners of horses and ponies in GB (n=797). The majority of animals received regular preventive health care: 95.6% had regular hoof care; 71.3% were vaccinated for both influenza and tetanus and median time since last anthelmintic administration was 8.7 weeks. Thirty-one percent of owners indicated their animal was overweight/obese. A new health problem within the previous 7 days was reported for 7.4% of animals, 59.3% of which were veterinary-diagnosed. Thirty-two percent of animals were reported to have a long-term/recurrent condition, of which osteoarthritis (13.9%) was the most prevalent. Obesity, musculoskeletal disorders, and dermatological conditions were the most prevalent conditions affecting veterinary-registered horses/ponies.

Frequency of equine laminitis: a systematic review with quality appraisal of published evidence.

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.

Demographics and management practices of horses and ponies in Great Britain: A cross-sectional study

The objectives of this study were to describe the demographic characteristics and management practices undertaken by owners of horses/ponies within GB and assess seasonal and geographical variations in management practices. A cross-sectional study was conducted, surveying a random sample of veterinary-registered owners in GB, using a self-administered postal questionnaire. A total of 797 useable responses were received. Only 4.0% of animals were stabled 24h/day, this proportion being greater in winter compared to other seasons (p<0.001). Shavings (45.7%) and straw (35.3%) were the most frequently used bedding. Ninety-two percent of animals had access to pasture (median 91 h/week). The majority of animals received forage (82.6%) and concentrate/supplementary feeding (86.1%). Retired/companion animals and ponies received supplementary feed less frequently and most animals were used for pleasure riding (60.6%). Seasonal and regional differences in management practices were identified, of relevance to practitioners and researchers in the investigation and management of disease conditions.

An investigation of the relationships between angles and shapes of the hoof capsule and the distal phalanx

REASONS FOR PERFORMING STUDY There is little scientific evidence to support the premise that poor foot conformation predisposes to foot pain and lameness. OBJECTIVES To determine relationships between external characteristics of the hoof capsule and angles of the distal phalanx; to determine variability in shape of the distal phalanx; and to investigate association between distal phalanx angles and the injury causing lameness. MATERIALS AND METHODS Feet were documented photographically and radiographically. Linear and angle measurements were obtained for the hoof capsule and distal phalanx and compared statistically. Horses were categorised according to injury group, and angles and linear ratios were compared between groups. RESULTS There was modest correlation between hoof wall and heel angles and angles of the distal phalanx. There was variation in shape of the distal phalanx. There was no significant association between injury type and angles of the distal phalanx, although there was a trend for the angle of the dorsal aspect of the distal phalanx with the horizontal to be smaller in horses with injuries of the podotrochlear apparatus or deep digital flexor tendon compared with other groups. CONCLUSIONS There are variations in shape of the distal phalanx largely due to differences in orientation of the concave solar border and the solar border to the horizontal. Variations in shape of the distal phalanx were not accurately correlated with external characteristics of the hoof capsule. There were weak associations between injury groups and angles of the distal phalanx. CLINICAL RELEVANCE Further work is required to elucidate risk factors for foot-related lameness.

Is there an association between ossification of the cartilages of the foot and collateral desmopathy of the distal interphalangeal joint or distal phalanx injury

REASONS FOR PERFORMING STUDY Associations between degree of ossification of the cartilages of the foot and injuries to other structures of the foot have been suggested, but have not been investigated by large scale studies. OBJECTIVES To describe the frequency of grade >3 ossification of the cartilages of the foot (possibly significant ossification, PSO), mediolateral symmetry of ossification and left-right symmetry between feet; and to investigate associations between PSO and injury of either the collateral ligaments (CLs) of the distal interphalangeal (DIP) joint or the distal phalanx. HYPOTHESES Possibly significant ossification of the cartilages of the foot is associated with CL and distal phalanx injury. Distal phalanx injury is associated with a mediolateral difference in ossification grade of > or =2. METHODS Horses were examined for lameness localised to the foot by perineural analgesia, and underwent radiographic and magnetic resonance imaging examinations. Age, breed, occupation, duration of lameness, lame(st) limb, primary cause of lameness, and presence or absence of CL injury were recorded. Dorsopalmar (dorsoplantar) radiographs were examined and ossification of the cartilages of the foot graded using a modification of a previously published scale. RESULTS One foot from each of 462 horses was included for analysis. There was left-right symmetry of ossification between feet, and significant association between grades of each foot, with lateral > or =medial cartilages. Possibly significant ossification occurred in the maximally ossified cartilage in 59 (12.8%) feet. There were significant associations between PSO of the maximally ossified cartilage of the foot and injuries of both the CLs of the DIP joint and the distal phalanx. There was no association between distal phalanx injury and marked asymmetry of the ossified cartilages of the foot. CONCLUSIONS AND CLINICAL RELEVANCE Extensively ossified cartilages of the foot are significantly associated with CL or distal phalanx injury. Markedly asymmetric ossification did not increase the likelihood of distal phalanx injury and should be considered at a prepurchase examination.

Risk factors for equine laminitis: a case-control study conducted in veterinary-registered horses and ponies in Great Britain between 2009 and 2011.

Laminitis is a highly debilitating disease of the foot known to have a complex and multifactorial aetiology of metabolic, inflammatory, traumatic or vascular origin. The disease has major welfare implications due to unrelenting pain associated with degenerative changes, which often necessitate euthanasia on welfare grounds. Despite this, there have been few high-quality studies investigating risk factors for equine laminitis, and only a limited number of risk factors have been previously investigated. The aim of this study was to conduct a case-control study of risk factors for active episodes of veterinary-diagnosed laminitis in horses and ponies attended by veterinary practitioners in Great Britain, based on multivariable statistical analyses. Questionnaires were received for 1010 animals, comprising 191 laminitis cases and 819 controls. Factors associated with an increased risk of laminitis were weight gain in the previous 3 months, summer and winter months compared to spring, new access to grass in the previous 4 weeks, box rest in the previous week, owner-reported history of laminitis, lameness or foot-soreness after shoeing/trimming, existing endocrinopathic (pituitary pars intermedia dysfunction and equine metabolic syndrome) disease and increasing time since the last anthelmintic treatment. Factors associated with a decreased risk of laminitis were increasing height (cm), feeding of additional supplements in the previous week and transportation in the previous week. Novel associated factors were identified that may aid in the management and prevention of the disease in the veterinary-registered equine population.

External characteristics of the lateral aspect of the hoof differ between non-lame and lame horses

During a pre-purchase examination (PPE) there is always a debate about how clinical findings of the hoof different from ideal should be interpreted in relation to future lameness risk and/or unsuitability of the horse for the potential purchaser. The objectives of this study were to describe and compare external angular measurements, linear ratios and hoof capsule characteristics of non-lame and lame feet. Photographs of feet from 300 horses with foot pain and 25 non-lame horses were analysed. Hoof wall, heel and coronary band angles and hoof wall length and height, weight-bearing length, coronary band length and height of the coronary band at dorsal and palmar locations were measured and expressed as linear ratios. Mean hoof wall, heel and coronary band angles were larger in lame compared with non-lame feet; only the ratio of dorsal to palmar coronary band heights and the shape of the coronary band were significantly different between lame and non-lame horses. Growth rings were divergent and horn tubules were non-parallel in lameness of >3 months. At a PPE, a larger ratio of dorsal to palmar coronary band heights in one limb may be indicative of previous lameness in that foot. Changes in coronary band shape and divergent growth rings and horn tubules would suggest a longer duration.

Laminitic pain: parallels with pain states in humans and other species.

Laminitis poses a threat to all horses, and is widely considered as being one of the most important diseases of horses and a global equine welfare problem. The effects of laminitis lead to debilitation, development of pronounced digital pain, and great suffering in the afflicted animal. The precise pathophysiological processes that result in laminitic pain are poorly defined, and hence the delivery of effective palliative care is clinically challenging. Knowledge and understanding of pain states in other animal species may further aid the elucidation of equine laminitic pain mechanisms, guide the search for treatable causes of this multifactorial problem, and thereby help achieve enhanced therapeutic and palliative care. However, parallels drawn from pain states in other animals must consider species differences in both anatomy and physiology, and the specific nature of the laminitic disease process.