Incidence and ossification of sesamoid bones in the hands and feet: a radiographic study in an Arab population

The incidence and ossification of sesamoid bones in the hands and feet were studied in 922 radiographs (400 hands and 522 feet) in an Arab population from Bahrain, 5-83 years of age and consisting of 549 adults (393 men and 156 women) and 373 children (286 boys and 97 girls). All radiographs of the hand and foot in the adult population showed two sesamoid bones in the thumb metacarpophalangeal (MCP) joint and in the hallucal metatarsophalangeal (MTP) joint, respectively. Only 2.3% and 1.5% of hands showed sesamoids at the MCP joints of the middle and ring fingers respectively compared to a reported incidence of 7.1% for each digit in Caucasians. The incidence of sesamoids in the MTP joints of third and fourth toes (0.6% each) and inferior to the hallucal interphalangeal joint (3.1%) is probably the lowest reported so far in the literature. In the hands, ossification commenced first in the thumb sesamoids, at the age of 10 years in females and 11 years in males and was completed by the age of 13 and 14 years, respectively. In the feet, ossification began first in the hallucal sesamoids at the age of 8 years in females and 9 years in males and was completed by the age of 10 years in both sexes. The incidence and ossification of sesamoids in the hands and feet in the Arab population from Bahrain seem to differ considerably from reports in other populations. The clinical significance of our findings is discussed.     

Interphalangeal sesamoid bones of the great toe: an anatomic variant demanding careful scrutiny of radiographs

We describe a patient who was found to have two sesamoid bones at the interphalangeal joint of the right great toe after radiographs for dislocation of the joint. Recognition of the sesamoids required careful scrutiny of the films. Interphalangeal sesamoids may cause painful callosities plantar to the joint or may become incarcerated in a dislocated joint. Our patient made a good recovery. The presence of sesamoid bones on the medial and lateral sides of the joint was unusual.     

Fabella prevalence rate increases over 150 years,and rates of other sesamoid bones remain constant: a systematic review

The fabella is a sesamoid bone located behind the lateral femoral condyle. It is common in non‐human mammals, but the prevalence rates in humans vary from 3 to 87%. Here, we calculate the prevalence of the fabella in a Korean population and investigate possible temporal shifts in prevalence rate. A total of 52.83% of our individuals and 44.34% of our knees had fabellae detectable by computed tomography scanning. Men and women were equally likely to have a fabella, and bilateral cases (67.86%) were more common than unilateral ones (32.14%). Fabella presence was not correlated with height or age, although our sample did not include skeletally immature individuals. Our systematic review yielded 58 studies on fabella prevalence rate from 1875–2018 which met our inclusion criteria, one of which was an outlier. Intriguingly, a Bayesian mixed effects generalized linear model revealed a temporal shift in prevalence rates, with the median prevalence rate in 2000 (31.00%) being ~ 3.5 times higher than that in 1900 (7.64%). In all four countries with studies before and after 1960, higher rates were always found after 1960. Using data from two other systematic reviews, we found no increase in prevalence rates of 10 other sesamoid bones in the human body, indicating that the increase in fabella prevalence rate is unique. Fabella presence/absence is due to a combination of genetic and environmental factors: as the prevalence rates of other sesamoid bones have not changed in the last 100 years, we postulate the increase in fabella prevalence rate is due to an environmental factor. Namely, the global increase in human height and weight (due to improved nutrition) may have increased human tibial length and muscle mass. Increases in tibial length could lead to a larger moment arm acting on the knee and on the tendons crossing it. Coupled with the increased force from a larger gastrocnemius, this could produce the mechanical stimuli necessary to initiate fabella formation and/or ossification.     

Skeletal anomalies in trisomy 21 as an example of amplified developmental instability in chromosome disorders: Histological study of the feet of 21 mid-trimester fetuses with trisomy 21

In a previous radiographic study on the feet of 71 adults with trisomy 12 we found, in comparisn to control individuals, an increased prevalence of biphalangeal toes and metatarsophalangeal sesamoid bones. The present histological study on the feet of 21 mid-trimester fetuses with prenatally diagonosed trisomy 21 confirms results of the earlier study. At both stages of development these minor bone anomalies have about the same frequency, thus suggesting 1) that they are selectively neutral, and 2) that they reflect a basic (innate) failure of ordered morphogenesis. Our observation that the normal spatial pattern skeletal variants is reproduced in trisomy 21 simply on a quantitavely higher level lends sound support to the hopothesis of amplified developmental instability in chromosome trisomies.