Page:Fabella prevalence rate increases over 150 years, and rates of other sesamoid bones remain constant - a systematic review.pdf/10

10 Fabella: more common than it once was, M. A. Berthaume et al. Table 5 Results from binomial regressions testing the relationship between time and prevalence rates of six sesamoid bones in the hand.

Data taken from Table 2 in Yammine (2014). Although Yammine (2014) reported differences in prevalence due to sex and race, all data were pooled here, as there were only 16 studies stretching over 120 years. Prevalence rates were given per hand. In cases where ulnar and radial sesamoid bones were reported separately, the higher value was used, as it was not possible to determine whether the sesamoid bones were always from the same or different individuals. Z-value = test statistic. A Bonferroni-corrected P-value of 0.00833 (P = 0.05/6) shows a lack of any statistically significant trends.

Fig. 6 Temporal changes in six sesamoid bone in the hand: the sesamoid bones at the metacarpophalangeal (MCP) joint of the first (MCPI), second (MCP-II), third (MCP-III), fourth (MCP-IV), and fifth (MCP-V) fingers, and at the interphalangeal joint of the first finger (IP-I). Data from table 2 in Yammine (2014) (n = 16 studies). Unlike with the fabella, there was no correlation between hand sesamoid bone prevalence and time (Table 5).

Table 6 Results from binomial regressions testing the relationship between time and prevalence rates of four sesamoid bones in the feet.

Data taken from Table 6 in Yammine (2015): data on the hallux (Table 2) were not analysed because they were highly mixed. Similar to the data with the sesamoid bones in the data, all data were pooled here, as there were only 16 studies stretching over 121 years. Prevalence rates were given per foot. In cases where tibial and ulnar sesamoid bones were reported separately, the higher value was used, as it was not possible to determine if the sesamoid bones were always from the same or different individuals. Z-value = test statistic. A Bonferroni-corrected P-value of 0.0125 (P = 0.05/4) shows a lack of any statistically significant trends.

means people are taller, weigh more, and have bigger muscles today than they did 100 years ago. 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. However, these factors do not explain the high prevalence of cartilaginous fabellae in foetuses, or why there was no relationship between presence and height in our sample.

Lastly, it is possible there is no shift in fabella prevalence rate, but the increase in prevalence rates is due to a change in fabella identification, where fabellae that were being

Fig. 7 Temporal changes in four sesamoid bone in the foot: the sesamoid bones at the metatarsophalangeal (MTP) joint second (MTP-II), third (MTP-III), fourth (MTP-IV), and fifth (MTP-V) toes. Data from table 6 in Yammine (2015) (n = 16 studies). Similar to the sesamoid bones in the hand, there was no correlation between foot sesamoid bone prevalence and time (Table 6).

previously ignored are now being identified. We believe this is highly unlikely for two reasons. First, there were no other changes in the prevalence of sesamoid bones in the hand or foot, and if there was a change in sesamoid bone identification protocol, it would likely not be isolated to the fabella. Secondly, the inclusion of X-ray and CT scans to determine prevalence rates in recent studies should lead to a decrease, not an increase, in prevalence rates through time, as cartilaginous fabellae, which may or may not have been included in previous studies, cannot be detected by Xrays and CT scans.

In this study, we investigated the prevalence rate of the fabella in a Korean population using published CT scans. Our prevalence rate of 52.83 and 44.34% for individuals and knees, respectively, falls within the range of those reported in the literature and shows an increase in fabella prevalence in Koreans over the past 80 years. In addition, we found bilateral fabellae to be more common than unilateral ones, there were no sex differences in prevalence © 2019 Anatomical Society