Ossification timeline of sesamoid bones at metatarsophalangeal joints.

Ossification timeline is a critical issue in studies regarding sesamoid bones at metatarsophalangeal (MTP) joints, but actual knowledge is still incomplete. The present study determines the cutoff age of sesamoids ossification at MTP joints. We conducted a retrospective review of radiographs of the feet from 5553 males and 3225 females between November 2005 and September 2012 to identify presence of sesamoids at 5 MTP joints and 3 variations of hallucal sesamoids. Age-specific prevalence of each presence and variations was calculated and clustered to produce latent age groups corresponding to the sesamoid ossification process in males and females, respectively. Males older than 7 years of age were divided into 5 age groups (8-11, 12-15, 16-29, 30-76, and 77-92 years), while females were classified into 4 age groups (8-11, 12-26, 27-76, and 77-92 years). According to the characteristics of sesamoid prevalence in each age group, the pre-ossification stage was defined at age 1-7 years in both genders and the ossifying stage was defined at age 8-29 years in males and 8-26 years in females. We also defined ossified stage as age 30-92 years in male and 27-92 years in females. The ossifying and ossified stages include 2 or 3 substages in both genders. A clustering analysis provided novel cutoff age points as ossification timelines for the sesamoid bones at MTP joints in males and females, which may have an impact on future sesamoid and skeletal development research.