[Hallux valgus--an atavism?].
In biology, atavism is generally understood as a biological phenomenon which brings to sight a recurrent phenotypic character which was lost for extinct generations. Phylogenic evolution of homo sapiens demonstrates today that the first plantar ray in tetrapods has always been a very stable ray and the lateral foot experienced a progressive adduction to the talo-metatarsal axis, together with a remodeling of the lateral column of the foot and a progressive valgus of the calcaneus beneath the talus. The foot appears as a strongly modified extremity, starting at a prehensile foot organ, common to our ancestors. In homo sapiens, the hand became a very mobile, less loaded organ, while the foot became a rather less mobile, but more loaded organ. The first ray, distal to Lisfranc's ligament, has no ligamentous structure holding it to the second ray. Stability is thus precarious and controlled by extrinsic and intrinsic muscles. Passive mobility of the tarso-metatarsal joints has been studied in vitro and in vivo. A relationship between unstable or hypermobile first ray and relevant Hallux valgus deformity has been demonstrated. Factors which facilitate the deformity are a long hallux and a functional equinus of the foot. Clinical pathology includes metatarsalgia, hammer toes, together with metatarsus primus varus and shortened gastrocnemii. Logical treatment of relevant and painful deformity includes tarso-metatarsal fusion with or without fusion to the second metatarsus. Osteotomies seem less secure in severe cases on the long run. In conclusion, Hallux valgus cannot be considered as an atavism because clinical history and findings do not correspond to the archaic prehensile foot and its evolution, but rather do correspond to a weak spot on a (still) fragile, often overloaded, phylogenetically young organ.
Klaue
K
K
Reparto di Chirurgia Ortopedica, Clinica Luganese, sede Moncucco, Lugano. k.klaue@bluewin.ch
D002648:Child; D006215:Hallux Valgus / Q000175:diagnosis / Q000000981:diagnostic imaging / Q000601:surgery; D006801:Humans; D007231:Infant, Newborn; D010027:Osteotomy; D011859:Radiography