Where have all the sesamods gone?

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netizens

Piece in the Independent. The last time I counted the foot had 28 bones.

http://www.independent.co.uk/studen...ot-expert-keeps-you-on-your-toes-1963838.html

Had it been The Guardian I might have understood.
toeslayer

 

My lecturer raised this issue with us on Thursday and stated that there were 29 s bones in the foot: A challenge!?

Sesamoid bones apart from joints are seldom found in the tendons of the upper limb; one is sometimes seen in the tendon of the Biceps brachii opposite the radial tuberosity. They are, however, present in several of the tendons of the lower limb, viz., one in the tendon of the Peronæus longus, where it glides on the cuboid; one, appearing late in life, in the tendon of the Tibialis anterior, opposite the smooth facet of the first cuneiform bone; one in the tendon of the Tibialis posterior, opposite the medial side of the head of the talus; one in the lateral head of the Gastrocnemius, behind the lateral condyle of the femur; and one in the tendon of the Psoas major, where it glides over the pubis. Sesamoid bones are found occasionally in the tendon of the Glutæus maximus, as it passes over the greater trochanter, and in the tendons which wind around the medial and lateral malleoli.

and therefore there are 31 bones in the foot. Not being clever but if you start looking in all the wrong places you can prove that the earth if flat too.

 

The patella is also a sesamoid bone.

 

Unless the patella has slipped somewhat, I dont think it is in the foot!!

 

I didnt think you were only talking about the foot as you mentioned biceps brachii!

 

well, there are sesamoids, then there are accessory ossicles, then there are intratendinous calcifications.

It's always been my understanding (correct me if I'm wrong) that a true sesamoid is one which is always present (such as the patella) vs an accessory ossicle which may or may not be, vs a calcification secondary to trauma.

Steve

 

well put!

 

Subtle genetic changes are implicated in analyses of morphological variance within adult foot populations; research has suggested that these include calcaneus secundarius, hallucal interphalangeal sesamoid and os intermetatarsum. Furthermore, the incidence and ossification of sesamoid foot bones apparently differs between populations.

Mann RW: Calcaneus Secundarius: Description and Frequency in Six Skeletal Samples. Am J Phys Anthropol 81: 17-25, 1990.
Roukis TS, Hurless JS: The Hallucal Interphalangeal Sesamoid. J Foot Ankle Surg 35(4): 303-308, 1996.
Case DT, Ossenberg NS, Burnett SE: Os Intermetatarseum: A Heritable Accessory Bone of the Human Foot: Am J Phys Anthropol 107: 199-209, 1998.
Dharap AS, Al-Hashimi H, Kassab S et al: Incidence and Ossification of Sesamoid Bones in the Hand and Feet: A Radiographic Study in an Arab Population: Clin Anat 20: 416-423, 2007.

 

"Subtle genetic changes are implicated in analyses of morphological variance within adult foot populations"

Is this a MANN quote? Does he mean that these "subtle" genetic changes are blamed in just the analysis of variance????

First, it should read "Morphological variations in the adult foot can be traced to genetic origin"

Second, what the heck is a "subtle" genetic change???????

Steve

 

Actually this is not a Mann quote at all but is simply an opinion of mine that does perhaps need some clarification. I should hurriedly point out that the rationale for what initially appears to be a somewhat poorly articulated (perhaps sloppy) term is supported from within a body of recent molecular biology and genetics research. I have attempted to address this in a recently submitted podiatry paper.

It is becoming clearer that expression of phenotypic variation is strongly influenced by epigenetic mechanisms that vary within and between populations. I simply thought that others might be interested to consider such structural inter-population differences and that in those authors opinions genetic differences are implicated. The fact that an emerging coherent 'subtle' epigenetic explanation may explain such findings may prove helpful to understand such morphological variance.

 

The phenotypic variance can be partitioned into genetic and environmental (all non-genetic factors, i,e, epi-genetic factors) components. If we take the length of the nose as a phenotype and measure the length of your nose, this is your phenotype for nose length. I then punch you in the nose- real hard, the phenotype, i.e. the length of your nose may have changed due to the environmental influence of my fist. To measure the relative contributions of genotype and environment we can estimate heritability for a population for a given trait by partitioning the variance within related individuals: hallux abduction angle, metatarsal length, arch height- anything that can be quantitated... There you go, quantitative genetics theory in a paragraph without excessive use of big, obscure words. Having just reviewed a couple of papers for a podiatry journal on this topic, I can honestly say that while the content was fine, they could have been much easier to understand for the average podiatrist had they been written in plain, common use, English. And, would probably have reached a greater audience had they been written so.

As I have pointed out in previous threads on the Arena here and have been stating since the late '90's, foot function and foot traits can and have been studied in this way. What is required are twin-studies (Monozygotic twins are clones- 100% same genotype, any differences in the phenotypes between them is probably due to the environment however shared environment elevates the heritability estimate) and adoption studies (children that are adopted share 0% genotype, but share a home environment) in order to tweek out the environmental from genetic components in the phenotypic variance. There were some twin studies published in JAPMA many, many years ago regarding foot pronation etc. If I can find the refs I will.

While it is interesting, how does it help us treat patient X with plantar fasciitis?

 

Here you go:
http://www.japmaonline.org/cgi/sear...fdatedef=1 September 1965&tdatedef=1 May 2010

There was another early paper, probably pre- 1970's, but hey.

 

Simon,

Would you agree that epigenetics is a term that generally refers to the activation or de-activation of protein-coding genes by non-coding genes i.e. A 'genetically' interactive effect?

In this way phenotype does not necessarily follow genotype. The processes involved created my individual nose length that you seek to hit so hard... presumably for using big 'obscure' words?

Yours in sport,

Greg

PS. You're quite right. This knowledge doesn't help... yet!

 

Greg,

Epi-genetics: "In biology, epigenetics is the study of inherited changes in phenotype (appearance) or gene expression caused by mechanisms other than changes in the underlying DNA sequence, hence the name epi- (Greek: επί- over, above) -genetics."

My point being, you need to differentiate and partition the variation in the phenotype, i.e. nose length, into attributable components. So, we have variance which is due to genotype and variance which is due to something other than the genotype, so this might include mechanisms which influence gene expression, it could also include being hit on the nose. How do you know which has the greatest responsibility for the resulting phenotype?

P.S. nothing personal about the nose, it's just an example people seem to understand.

 

Hi Simon,

I think that we largely agree. Fundamentally there are two aspects of epigenesis: genetic interaction (molecular biology) and environmental effects. Distinguishing between the two is difficult given the lack of research findings. This was (as you probably know) identified by Gottlieb (1991) with regard to psychological development but usefully introduced the term 'probabilistic epigenesis'. This assumes a constant interplay between the two, which seems likely.

Your comments (and not just here) have been very useful and I thank you for them. My interest is in drawing attention to how recent molecular evidence is beginning to clarify processes of growth and development. The reciprocal relationship with forces is likely to continue throughout life. Therefore we must, as a profession, grasp this subject (and its terminology) because surely we are better placed to understand the environmental forces effect on the process.

The fact that molecular evidence is emerging will come as a challenge for many. Perhaps, explaining its relevance will mean reducing it into more concise simple terms. The whole concept though does, I believe, at least allow us to consider forces within a variable structure. Too many podiatrists are stymied by STJN thinking: Maybe this approach will help us all?

Thanks again,

Greg

 

Thanks for your thanks. Good luck with the rest of your PhD. We can have a chat about it at Summer School.

 

I'm not a geneticist (is that the way you spell it?) but I always thought of epigenetic as anything that effects or influences or controls the development of a multicellular organism other than the genetic code. Period. Whether that is environmental or - as I suspect, intracellular, nonDNA sequence activity not yet appreciated, it's all nongenetic.

SO........ where do the sesamoids fit in??????

Steve

BTW:As I understand this, and correct me if I'm wrong: when you hit Gregg in the nose and it swells up, it's (hopefully) temporary and a physiological response to a (surprisingly quick I presume) stimuli. Now if you broke his nose and, after healing, it remained physically altered, then Simon, you are the epigenetic God. I kinda like the sound of that!)

 

Well Steve, if your work long and hard... wait a minute you're a surgeon, so every time you inadvertently shorten that metatarsal or "advertently" for that matter, you are an epigenetic God too. Wow! I change phenotypes... I am a god. Perhaps that explains the surgeon thing?

As you said:

Exactly.

 

"Perhaps that explains the surgeon thing?"

haha
well, not entirely.
I think our income and incredible good looks add to the aura!

Steve