Lamenting the condition!
THE PROBLEM OF LAMINITIS.
Laminitis is a very serious, debilitating and extremely painful condition of the horse’s foot. It is the second biggest killer of horse after colic.
The condition has been long known about and is probably as old as the domestication of horses. There is no human medical equivalent other than an autoimmune condition known as epidermyloisis bullosa but this is only a mild resemblance.
When laminitis strikes a horse it can be heartbreaking – the pain can be excruciating and the course of the disease can be variable and unpredictable. Formulating an effective management plan can be very difficult involving the cooperation and team approach by the owner, veterinary surgeon and farrier.
There is much research on the condition including locally the Australian Equine Laminitis Research Unit (AELRU) based in the School of Veterinary Science at The University of Queensland headed Professor Chris Pollitt and funded by RIRDC. This research is world class and hopefully will continue to give us more knowledge so that we can make this condition a thing of the past.A REVIEW OF FOOT ANATOMY.
The horse’s foot is an extremely specialized structure, a truly amazing feat of engineering! The horse has a single digit and soft tissue structures enclosed within a hard capsule on the end of relatively light weight limbs that allow the horse to travel at speed and over huge distances and tough terrain.
Outside and Inside the Hoof.
All “The Stuff” Crammed into the Hoof!
The pedal bone (P3) is enclosed and attached to the hard horn capsule by a very highly differentiated and tough tissue consisting of LAMELLAE. The lamellae form the foundation of the support of the bony column within the hoof capsule. Their surface area is huge due to the architecture.
The lamellae are a very complex arrangement of structures; the dermal laminae are attached to the bone and interdigitate with the epidermal laminae of the inner hoof wall. These are further differentiated into primary and secondary epidermal lamellae (PEL and SEL).
At the interface of the epidermal and dermal laminae is a tough, unbroken sheet of connective called the BASEMENT MEMBRANE. This structure has a huge array of receptor sites for many different chemicals such as growth factors, cytokines, adhesion molecules and integrins. Disruption of this membrane causes major disruption to the integrity of the hoof capsule and its function.
Professor Pollitt’s work has delved deep into the structure at the cellular level and the localized enzymes and chemicals that are present in healthy and laminitic affected hooves. It is worth reading his material as it is absolutely fascinating both in terms of the anatomy and the local physiology and biochemistry.
What Happens in The Foot During Laminitis?
When laminitis occurs the lamellar foundations are damaged and disrupted. The continuous physiological strain on the hoof- dermo- epidermal junction makes repair very difficult. Laminitis can be considered as a “natural process” gone wrong. The process can be divided into 3 phases, however these can be overlapping and in combination, there can be reoccurrence of phases and the severity can be variable too – it just aint that straight forward!!
The Developmental Phase.
This is a 30 -40 hour phase during which the lamellar separations are triggered. This occurs prior to the clinical appearance of foot pain and may be associated with disease process of other organ systems gut, respiratory, reproductive, immune etc). Aberrations in these other systems / organs remote form the foot result in the lamellar tissues being expose to factors and agents that lead to the separation and disorganisation of the lamellar anatomy. As stated above the exact nature is not fully understood as forms the basis of Pollitt’s work – we do know that the factors reach the lamellar tissues via the circulation. Sometimes no developmental phase is recognised!
The Acute Phase.
The developmental phase merges into the acute phase. This is when the first sign of foot pain is recognised. This phase lasts from the onset of clinical pain and lameness at the walk and trot to where there is evidence of displacement of the pedal bone within the hoof capsule. Displacement does not occur in all cases.
The Chronic Phase.
After the acute phase then often there is displacement of the pedal bone in the hoof capsule – this is the hallmark of chronic laminitis. Early displacement can be detected with good radiographs – see below. In the severe cases there may be signs evident in the hoof capsule – see below. The chronic phase can last for variable periods of time to indefinitely. Signs range from mild lameness, continued foot pain to sole penetration by the pedal bone, recumbancy, hoof wall deformation and sloughing of the hooves.
Predisposing Factors For Laminitis.
There are many factors that can trigger laminitis that are often at sites remote from the foot.
- Gastrointestinal tract – several causes including grain or grass overload, enteritis, colic, colitis and diarrhoea.
- Reproductive tract – retained placenta and uterine infections.
- Lungs – pneumonia and pleuritis
- Generalised infections – septicaemia and endotoxaemia
- Endocrine system – hormone related conditions such as Cushing’s diseases and equine metabolic syndrome (see article : A look at Laminitis and Equine Metabolic Syndrome)
- Muscle issue – severe equine rhabdomyolyis
- Musculoskeletal conditions – pain elsewhere can result in laminitis in other feet e.g. weight bearing laminitis in the leg opposite to one that has another severe problem.
The gastrointestinal tract is commonly involved particularly with grain or grass overload but the majority of cases seem to have an endocrinological basis.
Clinical Signs of Laminitis.
Classical laminitic stance.
- Shifting weight from 1 foot to another – may be subtle!
- Palpable heat in hoof – may be warm rather than hot!
- Increased digital pulses – these are palpated over the back of the fetlock – this is not specific for laminitis and may be present in other hoof conditions (abscess, bruises etc)
- Hoof testers on toe may but not always elicit pain.
- Tapping the dorsal wall may elicit a pain response
- Lameness when walking and turning – can be variable in severity.
- Classical laminitic stance – the feet are placed forward of the normal position so the weigh is taken off the toes (see above).
- Trembling, sweating, increased respiratory rates.
- Reluctance to pick up feet.
- Very severe cases may lie down and be reluctant to get up.
As the structures in the foot are affected (including descending of the pedal bone) then changes in the hoof may become apparent, again not of all these may be present and they may vary in their severity:
- The coronary band shows a defect where the pedal bone has descended in the hoof capsule.
- The sole may bulge (normally concave but becomes a convex shape) – again due to the descending pedal bone. In less severe cases it may become flat.
- May be bruising at toe in a crescent shape.
- Hoof growth changes – deformed hoof growth occurs. The front part has retarded growth the heels grow at a normal rate. There are often growth rings present and they converge at the toe. In some severe cases they take on an Aladdin’s slipper appearance with turned up toes.
- Regions of seedy toe or hoof separation.
Range of Chronic Laminitic Hoof Changes.
The diagnosis is made based on the history, the clinical signs and a thorough physical examination of the feet
The key to what is going on in the foot is good quality radiographs; usually 2 – 3 radiographs of each foot are taken with markers to allow us to evaluate the position of the pedal bone within the hoof capsule. These allow decisions to be made with regard to the severity, the chronicity, the preferred treatment for that particular case and the prognosis. They are extremely useful to the farrier when treating these cases. Usually the farrier and the vet will look at the X-rays together to plan the best treatment strategy. They are not expensive – usually $150 – $200 to look inside the foot.
This is, in my opinion an essential step and unfortunately one that many owners decline, preferring a wait and see approach!
Laminitis X-rays compared to some of the other studies we do are easy and can be performed at home providing there is a flat, firm surface and an adequate electrical power source (generators are not ideal for X Ray machines)
Often serial radiographs are useful to monitor changes during the course of treatment – laminitis is a dynamic process.
Venograms are also useful – they give an appreciation of the blood supply in the foot. The technique involves injecting dye into the vasculature of the foot and assessing by radiography. This is a more involved technique (but still straight forward) and is usually performed in a hospital environment. They are more expensive – $400 – $500 but definitely worth considering because of the amount of information they yield.
At Samford we can offer these both of these techniques.
Laminitic Foot X-rays.
Moderately rotated pedal bone.
A Selection of Laminitic X- Rays!
If you have any questions with regard to Laminitis, please do not hesitate to contact any of the large animal vets at Samford valley veterinary hospital. 3289 1322