High incidence of the os peroneum in a cadaver sample in Johannesburg, South Africa: possible clinical implications?

This study set out to investigate the incidence of the os peroneum in a cadaver sample from Johannesburg, South Africa and to note how bio-demographic parameters affect such incidence. The os peroneum (OP) is a sesamoid bone frequently found in the tendon of the fibularis longus muscle (FLM), as it passes on the plantar aspect of the cuboid bone. While this bone is often an incidental dissection room or radiological finding, OP fractures, with or without associated rupture of the fibularis (peroneus) longus tendons have been reported. Some investigators have also suggested that the presence of the OP may render the tendon of the FLM susceptible to avulsion injuries. The reported incidences of the OP range between 8 and 26%. These data have emanated by and large from radiographic rather than dissection studies, and the influences of biological indices such as age, sex, population group of origin, and side of the body on these incidences remain largely unknown. Forty cadavers (average age = 75 years) were dissected. Os peronei were present in 36 of these cadavers (90.0%), with 96% of them occurring bilaterally. This bilateral incidence was statistically significant (P = 0.007), but there was no significant difference in age (P = 0.38), sex (P = 0.97), or population group (P = 0.17). We hope that the unusually high incidence of the OP reported here will stimulate further research into possible predisposing factors as well as into the speculated associations between sesamoid occurrence, osteoarthritis, and tendon injuries.