Plantar keratosis is a hyperkeratotic lesion formed by the accumulation of dead skin cells on the plantar aspect of the forefoot. This can either be focused or diffused, depending on the callused region being subjected to excessive pressure and friction.
Focal plantar keratosis is a concentrated lesion; this comprises of a rough core made of avascular tissue which develops under the fibular condyle of a metatarsal head, usually of one of the lesser digits of the foot.
The diffused plantar keratosis affects more than one metatarsal and can form as a result of structural defects of the foot; a pes cavus foot, for example, increases pressure on the heel and beneath the first and fifth metatarsal heads.
Congenital deformities can cause defects in the metatarsal parabola leading to an abnormal distribution of weight across the forefoot; alterations in the length pattern of the metatarsals such as having a short first metatarsal, reduces its capacity for supporting weight.
This, in turn, shifts much of the weight on the lesser metatarsal heads, thereby increasing pressure underneath.
In order to successfully treat plantar keratosis, it becomes important to address the underlying aetiology of the hyperkeratotic lesion in addition to treating the symptoms.
Conservative treatment modalities include the scalpel debridement of the hardened skin surface to remove the core followed by the use of topical salicylic acid pads. This provides relief to the patient, with the lesion resolving itself within weeks of treatment.
There is also an emphasis on the need for comfortable footwear to avoid constriction of the toes in the shoe, which can otherwise create a retrograde hammertoe effect.
A gait analysis would help in identifying biomechanical deficiencies such as a high or low medial arch, which could be responsible for the onset of a number of postural deformities of the foot such as hammertoes and hallux valgus; these deformities further contribute to the formation of plantar keratosis by causing an imbalance in the functioning of the metatarsals.
Biomechanical imbalances could necessitate the need for conservative measures to be applied in order to off-load the pressure from the affected metatarsals. This would involve treating any pronatory pathologies that could potentially lead to the formation of hyperkeratotic skin lesions.
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Repetitive plantarflexion can lead to pain and mechanical limitation in the posterior ankle joint which is known as posterior ankle impingement syndrome. This pathology commonly occurs in ballet dancers and football players.