[The presence of the os peroneum and relative metatarsal length - X-ray study].

PURPOSE OF THE STUDY The os peroneum is a sesamoid bone found within the peroneus longus tendon and is present in the form of ossification on radiographs in 8-26% of the population. It is most likely the result of stress in the lateral side of the foot in connection with genetic factors. The factors affecting os peroneum development include anatomical changes, among others the length of the metatarsals especially because of the main tendon insertion on the first metatarsal bone. MATERIAL AND METHODS In the study, 768 standardised radiographs of feet of the Caucasian population, taken between 2006 and 2012 in the Vamed Mediterra hospital (Mostiště, Czech Republic), were investigated. The median age of the patients was 42 years, the range 18-75 years. The presence of an os peroneum was assessed and metatarsal length was measured by a modified method of Maestro. RESULTS The os peroneum was identified in 106 subjects (13.8%). Among the groups established according to the presence of os peroneum and its relation to the length of a metatarsal bone, the relationship with the first metatarsal (1+) was most frequent; it was seven-fold higher compared to the other variants. On the contrary, the variant 3+ was least frequent in the presence of the os peroneum. CONCLUSIONS The study presents a statistically significant relationship between the presence of the os peroneum and the length of the first metatarsal bone. Potentially, this is one of the causes of forefoot pain in relation to the os peroneum development and anatomical connections in this area. Key words: os peroneum, relative metatarsal length.