Musculature of Club Feet - What is Known, and What is Not

I recently undertook to chew on a rather amazing graduate dissertation about genetic research  into the eitioligy of talipes equino varus. It's called "Analysis of Variation in Clubfoot Candidate Genes, by Audrey R. Ester, of the University of Texas Graduate School of Biomedical Sciences at Houston. Most of it is quite above my head, but I tend to rather relish tackling things well above my head from time to time. (And sometime end up well below my feet.)  Usually, I do manage to, at minimum, "get the drift," and many times, actually grok the item at a decent enough lay level that I can afterward follow the conversation, as it were. And sometimes, just once in a while, mind you, I am able to take that limited comprehension and use it in service of deepening my understanding of some associated topic or field of study. I'm kinda kinky that way, I'm told.

But the most interesting part of Dr. Ester's paper is at the beginning. She starts with a brief recap of what constitutes a club foot, and then follows with a section on the current research on the muscular issues related to talipes, especially the nature and possible causes of the lower leg muscular atrophy most clubbies tend to have. And there is some very interesting stuff in this section, so I am going to quote liberally from the paper, and I am providing a link to the paper so you can attempt to tackle it yourself, should you be as kinkily inclined as myself.

Where it seems appropriate, I have inserted word definitions, to aid the reader with deeper understanding of the material. These are bracketed by [ ]. I have also removed the references from the quoted portions, but these can be examined by reading the full paper.

"Musculature and tendons of clubfeet"

"Clubfeet are also characterized by hypoplasia [Underdevelopment or incomplete development of a tissue or organ] of the calf muscles, which often persists throughout life; however there are conflicting studies about muscle placement, fiber density, and even muscle size...... In general, Irani and Sherman concluded that muscles of clubfeet are underdeveloped and smaller when compared to unaffected limbs. Because the
calf muscles have found to be hypoplastic,  they have been the focus of several histological [The study of the form of structures seen under the microscope. Also called microscopic anatomy] studies in clubfeet."



"In 1977, Isaacs et al. investigated the types, number, size, and direction of muscle fibers in individuals with clubfeet. This study concluded that clubfoot calf muscles are “grossly abnormal”, with higher numbers of Type I fibers, and both types of muscle fibers were larger than controls. Type I muscle fibers are also known as slow twitch muscle fibers and are redder in color because they have a higher myoglobin and oxygen content. These fibers are used in long-term activity because they resist fatigue, as opposed to fast twitch (Type II)
muscle fibers, which are used during short bursts of activities, are more fatigable and can only receive energy from glycolysis [is the metabolic pathway that converts glucose, C₆H₁₂O₆, into pyruvate ]. In addition to higher numbers of Type I muscle fibers, Isaacs et al. found evidence of denervation [ interruption of the nerve connection to an organ or part] in calf muscles of clubfoot. The larger muscle fibers imply that atrophy [is defined as a decrease in the mass of the muscle; it can be a partial or complete wasting away of muscle] is not the reason for smaller muscles, but might be caused by a neuropathy. ...

Fukuhara et al. performed histomorphometric [the quantitative study of the microscopic organization and structure of a tissue (as bone) especially by computer-assisted analysis of images formed by a microscope] and immunohistochemical [or IHC refers to the process of localizing antigens (e.g. proteins) in cells of a tissue section] studies on 16 ...clubfeet and 27 normal feet (seven normal feet from unilateral patients and 20 feet ...of the same age range as those affected). This study found that the bone malformations were secondary to ligament and collagen changes. The tibialis posterior ligament was found to be enlarged, and the orientation of the collagen fibers was disrupted. .... This supports data from previous studies that suggest that calf muscles in nonsyndromic [not part of a syndrome] clubfeet are abnormally small.

In 1998, a prospective study was performed by Loren et al. in which muscles of children with clubfoot were examined histologically, and further investigated if surgical intervention impacted these histopathological findings. About half of the patients with clubfeet showed abnormal muscle morphology. Twenty percent had fiber type disproportion [Congenital fiber-type disproportion is a disorder that primarily affects skeletal muscles, which are muscles the body uses for movement. People with this disorder typically experience muscle weakness...] , and 30% had fiber size variation (>3:1 ratio). The clubfeet with abnormal muscle morphologies had an increased risk for clubfoot recurrence and a second operation (5.6 fold increase). "
 .
"A histological study of clubfoot in 2006 reported on 431 muscle specimens obtained from 68 patient surgeries. This study gave very different results with 86.3% having “no discernible pathology”. Atrophy and an over-abundance of type I muscle fibers was found in 12.8% of the specimens. This study was much larger than the Omeroglu study and was a better representation of the average clubfoot compared to normal musculature. Other case studies have reported an additional muscle coming out of the soleus [one of the calf muscles] muscle. There have also been reports of a flexor digitorum accessorius [an accessory, that is, extra]  longus muscle that is aberrant in children with clubfoot. These case studies involve small numbers of clubfeet and from individual collection sites. In addition, many of these evaluated the “clubfoot deformity” but do not
discriminate between idiopathic clubfoot and syndromic clubfoot, and so these clubfeet might have different musculature due to syndromes (such as a neuropathy). A large-scale comprehensive study in idiopathic clubfoot patients is needed to validate these findings."

So, what does this all mean? First, it shows that there is more behind the musculature atrophy of club feet than merely the aftereffects of serial casting, bracing, and long period of non-weight bearing may produce alone (or rather, in combination.) [Quick aside - non-weight bearing during various growth stages in childhood means less pressure on the growth plates (epiphyseal plates) at the ends of the long bones of the leg, which alone can cause variable degrees of atrophy. When this occurs under unilateral conditions - that is, on one side - it can also induce some level of leg length difference, as the non-weigh bearing limb has limited growth during such periods.] The section also illustrates that, "the jury is still out," that is, there are some contradictory studies, and therefor, there needs to be more, and probably different kinds, of studies to further understand what is going on with club foot related atrophy.

At both a developmental level and a genetic level, there are factors that affect the muscle fibers themselves, causing these fibers to be less developed (hypoplastic.) There is also some intimation these changes may or may not be amenable to improvement by exercise, but this seems to be more difficult to determine who might be impacted by such efforts - it seems the percentages aren't all that high. To refer back to " Type I muscle fibers are also known as slow twitch muscle fibers and are redder in color because they have a higher myoglobin and oxygen content. These fibers are used in long-term activity because they resist fatigue, as opposed to fast twitch (Type II) muscle fibers, which are used during short bursts of activities, are more fatigable..." Don't be too confused by the apparent contradiction of " higher numbers of Type I fibers,..." A higher number of such fibers does not translate to "stronger', or more durable. Any change from a "norm" is seldom a good thing. Atrophy is sometimes reversible, but if the cause is a disease or genetic factor, there will be minimal improvement, and in the long term, a higher potential for increased weakness.


As I have mentioned in several prior posts, there is a unique parallel to post-polio syndrome, though the causes are different - both seem to show increased muscle degradation with age. It could be a more rapid, age-related break-down, or long-term overuse, but what is most important for us clubbies is how this may potentially affect our quality of life, and what additional costs may be associated with the aspect of post-club feet.

Finally, the last line in the above-quoted text -  "A large-scale comprehensive study in idiopathic clubfoot patients is needed to validate these findings." Amen, I say. But when, and by whom? And I would add, in post-club foot patients, as well. Because if the findings are validated in histological studies and later confirmed through other types of studies with infants and children still in treatment, the one certain way to validate such a theory it to study post-club feet muscular degeneration. This would have the effect of determining what, if anything, might be done differently during initial treatments - surgeries, casting, bracing, etc., to reduce such degradation in future generations of people who live with post-club feet.

I urge you to go and read this paper, at least as much as you are able to. I will confess that once I got to the actual genetics analysis part of the paper, my eyes took on the look of a crazed cop who'd run out of glazed donuts. You can see the paper here.