13 cases of overloading laminitis were examined using clinical, computertomographical and morphological methods ranging from macroscopical to ultrastructural levels. Like systemic (i.e, in most cases toxic) laminitis, overloading laminitis is a disease of the suspensory apparatus of the coffin bone. The symptomless initial phase of overloading laminitis differs distinctly from the systemic forms of laminitis. The initial phase of overloading laminitis (averaging eight days) is dominated by vasocompression caused by permanent and double burdening of the limb, whereas the initial phase of systemic forms of laminitis (lasting one to three days) is dominated by vasoconstriction induced by vasoactive mediators such as ,,endothelin". After the outbreak of overloading laminitis with its typical pattern of symptoms, hardly any general, but rather gradual differences are distinguishable compared with the systemic forms of laminitis. In subacute overloading laminitis, the classical inflammatory symptoms and microcirculatory disturbances with capillary hemostasis, postcapillary resistance, increased endothelial cell permeability and thrombus-formation are prevailing. In the suspensory apparatus of the coffin bone, overstraining and microscopical lacerations with severing of fibres and separation of collagen filament bundles from the basement membrane as well as separation of the basement membrane from the vital epidermal cells are inconspicuous, but these impairments worsen as the disease enters the chronic phase. Chronic overloading laminitis with its drastic sinking and slight to medium rotation of the coffin bone as well as increasing circulatory disruption is characterized by necrosis of the old and formation of a new suspensory apparatus of the coffin bone. Lacerations, reparatory and destructive changes, to some degree even necrosis, are visible in the peripheral areas of the newly formed suspensory apparatus of the coffin bone. In two cases, exungulation appeared in the late phase of overloading laminitis. A prophylactic horseshoe, which was developed according to biomechanical requirements, proved to be successful in practice. Diagnosis has been improved and refined by computertomography, because extent and degree of the pathological changes can be thus determined, especially in the chronic phase of the disease. Degeneration and regeneration of the suspensory apparatus of the coffin bone as well as the degree to which the coffin bone has demineralized can be evaluated. Therapy is aimed at preventing the spread of the disease to healthy areas of the hoof, toward alleviating pathological alterations, and finally, at healing, which is supported by the orthopaedic treatment principle of relieving the stress on diseased parts and burdening the remaining healthy parts of the hoof. Repeated clearing away of the scar horn wedge is indispensable to the elimination of circulatory disturbances and growth obstacles as well as to the restoration of parallelism of the dorsal hoof wall and distal phalanx. After exungulation or clearing away of the horny wall, the newly formed white line (Zona alba) has to be protected from any destructive burdening (suspension) until the new supporting pier of the suspensory apparatus of the coffin bone, i.e. the newly formed hoof wall, has been pushed down over the level of the lip of the coffin bone to form a supporting edge as protection for the newly formed white line. Through use of a hoof repair compound (artificial horn) for hoof wail reconstruction in those areas where the horn wall was cleared away or has not been pushed down far enough, the period during which the patient cannot be worked with can be shortened. The degree of restoration of the barrier function of the white line is of great prognostic value. The limprovement of stable hygiene and use of orthopaedic hoof boots are recommended.
