Laminitis

LAMINITIS. . DEFINITION. Laminitis is not an inflammatory condition of the foot per se but a peripheral vascular disorder caused by either systemic disease and or chronic overloading of a single limb (like in the case of fractures of the opposing limb). The Equine foot appears to be a target for vascular abnormalities due to the unique disposition of the blood vessels within a non expandable hoof capsule. Pony breeds seem to be more predisposed to laminitis. PATHOGENESIS, AETHIOLOGY AND CLASSIFICATION. The alterations in vasoactive mechanisms lead to laminar ischaemia in the horse’s foot, developing necrosis in the structures of the hoof wall specially the dorsal aspects of coronary band, hoof wall and sole. The resulting pain causes further release of catecholamines that cause vasoconstriction and further ischemia, thus oedema forming at the epidermal-dermal junction allowing the support of the pedal bone within the hoof capsule to be lost, due to weight bearing and the pull of the deep digital flexor tendon mechanical separation occurs mainly in the toe region, with the pedal bone rotating or sinking. The Causes are multifactorial as many different predisposing factors can trigger the same vascular mechanism. Will divide them into 4 main categories. Alimentary: Grain overload, Grass overload, Cold water ingestion and Electrolyte imbalances. Single Limb overloading: in severe unilateral lameness Hormonal: Corticosteroid overloading, high testosterone and oestrogen, Hyperthyroidism, Hyperadrenocorticism and Cushings. Endotoxic: as a sequel to colic, pneumonia, metritis…. We have 3 presentations, Acute (acute phase of systemic illness with lameness) Chronic (residual lameness following resolution of systemic illness) and Chronic laminitis not associated with any active disease but concurrent to chronically distorted feet. CLINICAL SIGNS. Acute laminitis. Pain and lameness concurrent with signs of the systemic disease. Other signs will vary depending on the aetiology, i.e., cresty ponies on grass laminitis, diarrhoea in grain overload… There’s always increased digital pulse, pain of hoof testers, evidence of depression of the dorsal coronary wall with or without exudates, some cases may show convex sole or discoloured by blood effusion, the white line may show evidence of haemorrhage, The animals will display a typical stance with the forelimb stretched out in front and the hidlimbs placed beneath the body, the gait is typical heel before toe foot placement and obvious lameness. Picture 1. Animal with chronic laminitis have local signs of foot pain similar to those of horses with acute laminitis, however the feet develop long term deformation, rings parallel to the coronary band reflect temporary alterations in hoof growth causing diverging growth rates and the typical appearance of the slipper foot Picture 2. and convexity of the sole with ultimate ulceration and prolapse of the sole, secondary infection are a common feature of laminitis ranging from simple sub solar abscesses to more extensive infections and some can lead to septicaemia and this will cause a sudden exacerbation of lameness. RADIOLOGY. Radiographs are necessary to identify the degree of phalangeal displacement, presence of infection and chronic bony remodelling of the third phalanx, plain radiography should be used in combination to the use of markers in the hoof capsule in order to assess not only rotation but sinking, this is done by placing a radio-opaque marker on the dorsal hoof wall and at the tip of the frog in the solar surface. Evidence of remodelling of the tip of the pedal bone, gas densities, fractures and irregular radiolucencies justify a guarded prognosis…pictures.3a,3b,4a,4b TREATMENT. Acute laminitis should always be an emergency and has to be multifactorial. a. Removal of initiating cause. I.e. treating systemic disease or Alimentary imbalance… b. Treatment of peripheral vascular disease. Acetylpromazine to reduce vasoconstriction, NSAIDS to control digital pain and endotoxaemia, Ice to reduce the local oedema, other treatments will include removing sodium from diet and supplementing with potassium chloride, Isoxsuprine and topical application of Glyceryl trinitrate to the pastern. c. Mechanical support of the diseased laminae and sole. As in preshaped frog pads or bandaging with plaster of paris slippers or similar. In Chronic laminitis the treatment is aimed at correcting the residual foot problems and the general management of the animal. a. Limited intake of carbohydrates and control obesity b. Supplementation of diet with potassium chloride, methionine and biotin. c. Corrective foot trimming including dorsal wall hoof resection.(picture 5) and orthopaedic shoeing,(picture 6) guidance with radiographs.See pictures. d. Deep flexor tenotomy as a salvage procedure in those unresponsive to medical treatment. Most animals that develop laminitis recover with medical treatment and once they have shown no signs of rotation by day 10 of the condition treatment can be stopped gradually, but the prognosis becomes unfavourable when the acute phase last longer than 10days, digital pain is uncontrollable, blood pressure remains higher than 200mmHg, secondary infection is present and if rotation of the pedal bone exceeds 5.5 degrees. Pictures.. Prognosis becomes hopeless in cases of Sinking of the third phalanx and exungulation of the hoof. Dorsal hoof wall resection. Picture 5 heart bar shoe applied to a hoof with a dorsal hoof wall resection. Picture 6a lateral appearance of foot with impression material and heart bar shoe, note the ulceration and sinking of the coronary band. Picture 6b. Lateromedial radiograph of a chronically rotated limb showing gas densities and remodeling of the distal PIII, turk slipper. Picture 3a Another more extreme example with a very clear osteolysis of the distal aspect of PIII. Picture 4a Calculations of angles of rotation. Picture 3b hopeless prognosis, see the angle of rotation of 16 degrees. Picture 4b. Typical stance on laminitis. Picture 1. Typical appearance of chronic foot changes in chronic laminitis, see rings and elongated toe. Picture 2. References. Adams’ lameness in horses, Ted Stashack Equine Medicine, Surgery and Reproduction, Mair, Love, Schumacher and Watson. The Glass horse, University of Georgia and Glass Horse Project.