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Unusual Fracture of Sesamum Peroneum

1942; Radiological Society of North America; Volume: 38; Issue: 1 Linguagem: Inglês

10.1148/38.1.90

1527-1315

Henry G. Hadley,

Foot and Ankle Surgery

There are eleven accessory bones of the foot (1): as trigonum, as sustentaculum proprium, calcaneus accessorius, calcaneus secundarius, ossiculum trochleae, tibiale externum, cuboides secundarium, as intercuneiforme, sesarnum peroneum, as intermetatarseum, and os vesalianum. Of these eleven, only one is a sesamoid bone. The term “sesamoid” (from the resemblance to sesame seed) is applied to bones which are enclosed and located near the insertion of tendons in close contact with other bones. Sesamoid bones are divided into those which are constant and those which are inconstant in their occurrence. Examples of the former are those of the hallux, which are not included in the above list of accessory bones. The tibiale externum is considered by some to be a sesamoid bone in the tendon of the tibialis posticus. Pfitzner (2), however, claims it is never enclosed in a tendon. Dwight (3) found it to be a separate bone in 10 per cent of cases. Two of the accessory bones of the foot, when present, are found in the plantar portion of the longitudinal arch. The os vesalianum is at the base of the fifth metatarsal and the sesamum peroneum at the posterior edge of the cuboid in the peroneus longus tendon. The other bone in this location is the epiphysis of the fifth metatarsal, which is ununited up to the fourteenth to twenty-second year, when normal fusion takes place. The appearance of an os vesalianum in an adult may be only a result of a lack of fusion of the epiphysis. The sesamum peroneum was found in 5 per cent of individuals by Bizarro (4), in less than 10 per cent by Dwight, and in 6 per cent of a personal series of 200. The possibility of fracture of this bone by direct trauma cannot be great, as no previous case could be found in the literature. In the patient to be described, no known injury occurred other than weight-bearing. A fracture of this bone might be confused with an avulsion of the anterior inferior portion of the os calcis, There are two distinguishing features: the difference in density and the later absorption of the posterior portion. In avulsion of the anterior portion of the os calcis, no such absorption would take place as occurred in this case. Case Report I. S., a white male, aged 34, was examined Sept. 20, 1938. His chief complaint was pain in the arch of the foot, which had appeared one week earlier after the weight had been suddenly thrown on this part of the foot at the edge of a street curbing. X-rays revealed a fracture of a peroneal sesamoid through the center. This bone measured 10 mm. × 15 mm. and was located just under the posterior margin of the cuboid. There was a 5-mm. separation of the fragments. Treatment by cast for four weeks produced satisfactory results. The diagnosis of fracture was made certain by the irregular edges of the adjacent surfaces, and by the changes shown in the later films taken Oct. 17, 1938, and July 9, 1939. The last film shows almost complete absorption of the posterior fragment.