Ankle sprains occur in France at the rate of 6000 cases per day. Of these, 20 to 25% are sprains of the midfoot, which most often go unnoticed since this pathology is little known or not at all, and no specific treatment exists for the moment.
Among the current treatments proposed in the case where there is a diagnosis of sprain of the midfoot, one can mention the Barouk shoe, or the strapping bandage in the form of metatarsal collars, or indeed the plaster boot, all of which support the joint of the midfoot, but without holding it firmly between the forefoot and the rearfoot. Because of this, the resumption of walking is delayed. Elimination of the pain can be achieved only with the plaster boot, and walking can be achieved without aid. In addition, the use of the plaster boot necessitates a treatment to prevent platelet aggregation up to the return to full walking, and can induce secondary trophic difficulties.
The application of elastic bandages (strapping or taping according to the elasticity of the straps) calls for a suitable technique and therefore appropriate training, in order to avoid a garotting effect accompanied by oedema and painful compression points that appear with the sprain. The* other drawbacks of elastic bandages, and especially strapping, are a possible cutaneous intolerance, the obligation to change the bandage or strapping about every three days, and above all the fact that this change has to be effected by specialist staff.
Sprains of the midfoot are one of the most frequent occurrences, and at present there is no orthosis suitable for its treatment. The midfoot is a transition zone between the forefoot or ball, which has a horizontal structure, and the rearfoot, which has a vertical structure. The midfoot has a frontal and unstable structure, since it is multi-articular, and is supported by a multiplicity of ligaments that are subjected to regular stresses (at every step) of some consequence (the full weight of the body).
There are several reasons that render particularly difficult the implementation of an orthosis for the midfoot that is effective and easy to use:                the anatomic constitution of the midfoot, which includes the innominate joint, the Chopart mediotarsal joint and the Lisfranc tarsometatarsal joint;        the clinical approach access to the midfoot, rendered difficult by its particular architecture, its mechanical complexity, and the magnitude and impact of the stresses on it.        