Out of the roughly 206 bones in our body, the hyoid bone is the only one that is entirely separated from the rest of the skeleton. Vesalius in the 16th century recognized its isolation and depicted the hyoid resting on the plinth like a set of false teeth. Being U-shaped, it is appropriately named after the Greek letter upsilon. The hyoid bone resides immediately under the jawbone, just above the thyroid cartilage (Adam’s apple in men). Here 12 muscles attach that are critical for swallowing and vocalizing. In this well-protected position, it doesn’t get much notice and is rarely broken. Strangulation is the exception, so the coroner in your detective novel might want a look at it.
In humans, and uniquely so, the hyoid bone is moveable, which has been one of the evolutionary changes important for speech development. Its mobility, however, also contributes to obstructive sleep apnea. As the attached base-of-tongue muscles fall backwards in relaxation, they narrow the airway in the throat. Otolaryngologists counter this by drawing the hyoid approximately an inch forward and tethering it with strong sutures either to the inside of the jawbone or to the top edge of the thyroid cartilage. I would think that this might affect speech or swallowing, but the research papers say otherwise.
Don’t confuse the hyoid bone with the wishbone, which is present in some birds and their dinosaur relatives. The wishbone is farther down the neck, is a fusion of those animals’ collar bones, and contributes to efficient flying in some species. (See previous post: Twelve No-Fail Conversation Starters About Wishbones.) By contrast, all vertebrate animals have a hyoid bone, although it varies widely in shape and function. Here are two examples.
The hyoid bone helps a woodpecker pound its beak 22 times a second, 12,000 times a day, without apparently giving itself headaches. The beak is a bit flexible, which absorbs some of the shock, as does a thick pad of spongy bone that separates the beak from the skull. The hyoid bone handles the rest. It starts in the neck, like in the rest of us, but then curls around behind and over the skull to attach next to a nostril, thus bypassing the brain. It is thin and fragile looking.
Not so for the endangered howler monkey. Its hyoid bone is about the size and general shape of a 4-ounce, round-bottomed measuring cup. That is almost half the size of the monkey’s skull. The hyoid is instrumental in the howler’s ability to project its voice two miles.
Given the relative numbers of howlers and humans, it’s good that we are not so well-voiced.
Published in abbreviated form in NYT Book Review Letters, March 21, 2021
With the exception of those living in caves, I suspect that everyone has heard the current and widely disseminated advice regarding the health benefits of walking or jogging 10,000 steps a day. In addition to improving cardiorespiratory health and acquiring some sunshine-derived vitamin D, the repeated impact of feet on pavement is critical for maintenance of bone health. Although swimming and cycling are great for the heart and lungs, they do not jolt the bones sufficiently for them to maintain their density and strength.
The heart is entirely dependent on a steady supply of calcium for its health, and if there is not enough calcium coming in through intestinal absorption, hormones release calcium from bone to the heart’s benefit but to the skeleton’s detriment. Bones attempt to counter this wanton thievery by constantly remodeling themselves and strategically adding new calcium crystals in areas where the bone cells sense mechanical stress. This is particularly critical in the hips and spine, since fractures here can be permanently life-changing if not life-ending. For women, menopause brings added peril, because the absence of critical hormones diminishes bone density, i.e., the shortage causes bones to become porous, i.e., osteoporotic.
Regular impact exercise counters this tendency and underlies the recommendation for achieving 10,000 steps a day. It is hard enough to do this on Earth but is nearly impossible in the near-zero gravity of space. Weight lifting is futile, because barbells float. Magnetic shoes might work but would risk interfering with the complex electronics on board. Futurists have also considered creating artificial gravity by spinning part or all of the spacecraft, making it a large centrifuge. Theoretically this would work, but the cabin would either have to be 100 feet in diameter or spin at a rapid, energy-consuming speed, neither of which seems practical.
Presently, International Space Station inhabitants fasten a harness around their shoulders and waist and hook it with bungee cords to a treadmill to keep from floating away while they jog. Nonetheless, astronauts loose bone mass at ten times the rate seen in postmenopausal women, and a six-month stay on the ISS causes a 10 percent loss of bone. This rate would be unsustainable on a three-to-four-year roundtrip journey to Mars.
Maybe once they get to Mars, could travelers bulk up their bones in preparation for their zero-gravity trip back to Earth? Gravity on Mars is one-third that of Earth’s. Nobody knows whether that is enough to maintain or restore bone health. Then if travelers wanted to take their families along or have families en route, they would have to deal with the unknown effects of low gravity on growing bones. Nonetheless, kids would undoubtedly have a blast doing cartwheels and flips during the entire adventure.
Solutions might come from a surprising source—hibernating bears. It’s Spring, and bears are beginning to rouse themselves from four to five months of complete indolence, yet they come through without a trace of diminished bone density. Brave investigators have darted grizzlies and similar species and sampled their bone and blood immediately before, during, and after hibernation. (Who said that studying bone hormones had to be dull.) The researchers have found that a bear’s bone metabolism essentially shuts down along with its other bodily functions during hibernation, which proves to be a highly complex, multisystem process affecting the brain, heart, kidneys, muscles, and bone. Investigators understand the process incompletely, so time will tell if bears can offer humans some help with bone health. In the meantime, it’s Spring. Anyone for a walk?
Despite the pandemic, my wife and I have “traveled” internationally every Wednesday since July. Our imaginary private jet flies at the speed of light, so we happily skip security checks and avoid jet lag. We start the day in our on-board bed by listening to our destination’s national anthem and googling what the locals have for breakfast. Later we join Rick Steves and Barby at Geography Now, both of whom are fountains of knowledge about our chosen country. Continuing on YouTube, we delve into the nation’s language quirks, sports, dog breeds, best and worst parts of visiting, cuisine, politics, national parks, and so on. Living in multi-cultured Los Angeles, we have only once missed being able to order a pick-up dinner of that country’s cuisine. (There don’t seem to be any Croatian restaurants near by!) We round out our trip by watching a locally made movie. We have seen some great ones. Just google “best films from __________.”
Why am I telling you about our virtual travels? First to recommend such trips—highly educational and diversionary. Secondly, everywhere I go I find some unique bones, and last week’s visit to the Czech Republic was no exception.
A huge clock has graced the wall of Prague’s Old Town Hall since 1410, which makes it the world’s oldest working astronomical clock. If you want to know the local time and current date, the sidereal time (ask an astronomer to explain), the Old Bohemian time (ask an old Bohemian), Babylonian time, or the current position of the sun, moon, Zodiac constellations, and other planets, the clock will show you. It also indicates the time of today’s sunrise and sunset and which saint is having his feast day.
So far, jaded Rolex owners may not be impressed, but there’s more. Enough that crowds gather on the hour to watch the show. Two small doors above the dials open, and carved figures of the Apostles parade past. Above the Saints, a golden rooster flaps its wings. Carved figures also flank both discs. The lower set, to symbolize goodness, represents an archangel, philosopher, astronomer, and historian. The other set represents disdainful activities. A vain man shakes his head as he sees his reflection in a mirror, a miser rattles his purse, a skeleton rings a bell and turns an hourglass over (hint, hint), and a hedonist stands frozen in extravagance and pleasure.
Naturally, I have to critique the skeleton’s anatomical correctness. Both hips are dislocated, but otherwise it looks pretty good. The pigeon netting helps.
By itself, a clock, even one with some bones, is probably not worth a trip to Central Europe. Presently, however, when time seems to be standing still, appreciating a mechanical marvel over 600 years old, one that has witnessed numerous bouts of political and disease-induced turmoil, is a good reason to acknowledge the capacity to keep on ticking.
Valentine’s Day conjures up sweet images of romance that humans typically associate with roses and chocolate. Casanova, however, had his own ideas about heightening sexual desire and shared large platters of raw oysters with his lovers, even though no solid evidence supported or supports this indulgence. “We sucked them in, one by one, after placing them on the other’s tongue. Voluptuous reader, try it, and tell me whether it is not the nectar of the gods!” Imagine, however, how much easier it would be to consume oysters unshucked and just crush the shells in your throat before swallowing the treat.
Perhaps efficient, but unappetizing and certainly not sexy, you say. Nevertheless, many fish perform these feats, thanks to teeth embedded in a second set of jaws that is located in their throat. These bones and teeth have likely developed independently in various types of fish, including flying fish, tilapia, and sunfish as well as in common aquarium dwellers such as angelfish.
Two adaptations of pharangeal jaws are particularly remarkable. Mobility characterizes the first. After a moray eel captures a meal with its oral teeth, it opens its pharangeal jaws, moves them forward to grasp the prize, and pulls it irreversibly into the eel’s digestive system. Researchers think that morays developed this mechanism as a result of living in tight burrows where they could not expand their bodies sufficiently to create negative pressure, necessary to draw prey deep into their mouths. Fortunately, that is not an issue with humans consuming chocolate, at least not until clothes become too tight.
An even more amazing adaptation is one characterized by strength. Black drums, also known as drums and drummers, are common along the East Coast of the United States and in the Gulf of Mexico. They typically weigh five to thirty pounds but can grow to over one hundred. Their hardened pharangeal jawbones and accompanying strong muscles are adapted to crushing crabs and other shellfish, and drums find oysters particularly delectable. Fishermen look for drums in oyster beds and sometimes see their tails sticking out of the water, which results from the drums’ habit of bottom feeding in shallow areas. And feed they do. In a day a drum can consume roughly one commercially sized oyster per pound of body weight. For me, that would be 170 oysters, far more then I would either want to shuck or to crush and spit out the shells.
Whether black drums are affected romantically by sharing a bed of raw oysters is yet to be determined. But without a pharangeal jaw, I’m sticking with chocolate and a sentimental card, both safely obtained online. Happy Valentine’s Day.
When he wasn’t hating his paleontology archrival in some tangible way, Edward Drinker Cope* was discovering and naming fossil fauna. In 1892 he found a dog-like creature with skeletal features suggesting its jaws could crush bones with impunity. These features included oversized premolars placed in a short, robust jaw, which provided wide attachment areas for muscles. Drinker named the beast Borophagus (gluttonous eater). Based on the presence and measurements of other skeletal parts found across North America, it roamed widely between 16 and 2 million years ago and weighed about 50 pounds. Its mighty bite force allowed it to occupy a unique ecological niche, presently represented in Africa by the spotted hyena. Because “Boro” could crack open large bones and savor the marrow within, it could stay back and let other large carnivores finish their meal and then enjoy their leftovers. Or maybe they hunted in packs as hyenas do, devouring large prey, bones and all, within a few frenzied minutes. In that case, Boro would have an advantage if it could snap off an entire leg and trot off to enjoy it in peace.
Because Drinker and subsequent paleontologists had just the bones, they were unable to determine anything about Boro’s behavior. Was it a hyena-like pack animal? A scavenger? A predator? Answers have come recently from a surprising source—its fossilized poop.
While boating on Turlock Lake, east of Modesto, California, an amateur fossil collector recognized a blob on the shore as a coprolite, scientific parlance for feces turned to stone. It had fragments of bone visible near the surface, so the collector surmised that the donor was a large carnivore, and Boro was the only known carnivore from that time in that area. He dug around and recovered 14 coprolites, which became the material for a 42-page scientific publication.
The fact that Boro and company dropped feces in clusters, which is how wolves and spotted hyenas mark territory, implied to the investigators that they were social animals and that the fossil collector had come across their outhouse. Computed tomography analysis of the coprolites revealed bone fragments that came from ribs or limbs of animals as large as 220 pounds, the size of today’s mule deer. Although some of the bone fragments were nearly 2 ½ inches long, most were in the quarter-to-half-inch range, which made the source generally unidentifiable, although one clearly came from a bird wing and another from a beaver jaw. The investigators suggest that Boro’s habit of crushing bone accelerated recycling of the contained nutrients into the food web and remark that no animal took Boro’s place following its extinction. Modern day carnivores living in the area (coyotes, foxes, cougars) do not have Boro’s bone-crushing capabilities, which indicates a fundamental shift in food web dynamics—quite a lesson derived from a latrine.
This year’s suggestion spans the entire gambit from frugality to extravagance. You will find it particularly helpful for those discerning, curious individuals on your gift list who like to learn, and smile a bit in the process, i.e., nearly everybody!
Choose between the traditional, Kindle, and Audiobook versions. For the hard-to-please linguists on your list, consider the Russian or Korean translation.
If the recipient responds with a quizzical, “Why me? Why this?” when they open the gift, explain that
Amazon readers have given the choice five stars and included comments such as “this is how science writing should be done,” “entertaining and informative,” and “a wonderful read for anyone with a backbone.”
Radio interviewers and podcasters have clambered for opportunities to interview the author. These include KERA Think, NPR Cool Science, and Talk Nerdy. (If any of your giftees have been naughty this year, consider just sending them the links to these interviews!)
Linguistics: Pater or faeder? Jawbone size affects speech.
Paleontology: Boro, the Bone Crusher
Geology: What bones have to say about earthquakes.
and topics on anatomy, strontium, hibernation
To end the suspense, here’s the recommended gift. Happy Holidays. To make your first-edition gift even more precious, contact us with the lucky recipient’s name and your snail mail address to receive an autographed bookplate.
Consider gifting BONES to yourself if you haven’t already.
For thousands of years, bone setters and doctors could not accurately diagnosis broken bones or differentiate such injuries from joint dislocations and torn ligaments. That all began to change with a chance discovery 125 years ago this month. Subsequently, perhaps with equal parts of chagrin and enlightenment, doctors began using the new discovery to discount many of their long-held assumptions and begin to accurately diagnose skeletal diseases.
In his darkened laboratory on November 8, 1895, a German mechanical engineer and physicist, Wilhelm Röntgen, electrified a vacuum tube and happened to observe a strange glow coming from a nearby card, one that he had coated with a photosensitive chemical. He turned the electricity off. The glow disappeared. He flipped the switch on and placed his hand in front of the card. A shadow of his hand appeared on the card. Astounded, he ate and slept in his laboratory over the following weeks and studied this unknown ray, which he labeled “X,” the mathematical symbol for an unknown.
He learned that X-rays passed through books, no matter how thick, and that coins cast a shadow on the photosensitive board. Six weeks later Röntgen shared the secret with his wife, who allowed him to take a fifteen-minute exposure of her hand, the first orthopedic X-ray. When she saw the image of her hand skeleton, she exclaimed, “I have seen my death.” Far more broadly, she was witnessing the advent of diagnostic radiology and modern orthopedic surgery.
A week later, Röntgen presented his findings in a scientific paper titled, “On a New Type of Rays.” This caught the immediate attention of physicists, who alerted the lay press. The discovery made the front-page headline news within a week of Röntgen’s public presentation.
At the time, vacuum tubes were well known and easy to make. After Röntgen’s discovery and announcement, many investigators contributed to the understanding and practical applications of X-rays. Interest was intense and advances were rapid. Less than three months after Röntgen’s public announcement, an enterprising electrical contractor and avid photographer opened a laboratory and offered diagnostic services.
Röntgen received the Nobel Prize in 1901, the first one ever awarded for physics. Röntgen not only gave the reward money to his university, he also refused to take out patents on his discovery in order to promote wide-spread application.
I suppose when X-rays were in their infancy, patients were asking, “Now that you have finished obtaining a thorough medical history, performing a careful physical examination, and telling me that you know with assurance what is wrong, aren’t you going to order an X-ray, Doctor?” This question implied a lack of trust in the doctor’s diagnosis unless he threw in a high-tech, oh-so-modern X-ray evaluation. Gradually, doctors and patients came to understand when an X-ray study could help with the diagnosis or treatment and when one would be superfluous. For instance, today it is intuitive that a sore tooth most likely deserves an X-ray while a sore throat does not. In general, X-rays reveal calcium-rich structures—those containing enough calcium to cast a shadow in the X-ray beam. Examples are bones, teeth, hardened arteries, and kidney stones.
Doctors have learned to order X-rays with some caution because radiation damages living tissues and their DNA. That fact required discovery, and the harmful effects of early X-ray examinations were slow to reveal themselves. Since X-rays could not be seen or felt, investigators had no reason to consider them harmful. Both Nicola Tesla and Thomas Edison experimented with X-rays, and both observed that their eyes became irritated; but neither drew a connection between the radiation and their symptoms.
For convenience, dentists originally held the film inside the patient’s mouth with their fingers when shooting dental X-rays. Decades later the skin on their hands dried, cracked, and became cancerous. I have been fortunate to escape similar problems. In the 1950s I watched my toe bones wiggle under fluoroscopy in the shoe department at Sears, and in the 1960s I received enough radiation for acne that it left me “sunburned.” Nowadays the radiology tech steps behind a lead shield before shooting the film, and there are generally accepted standards for how much radiation a person can receive on an annual and lifetime basis without incurring undue risk.
Despite our best efforts, we cannot avoid radiation exposure entirely. Some comes naturally from the sun and some from the ground. We get more during a plane flight because the thinner air at high altitude blocks less of the sun’s radiation. This fact poses a major, unsolved problem for interplanetary travel because of the absence of Earth’s radiation-shielding atmosphere and because of the impracticality of armoring spaceships with lead. Stay tuned, or maybe just stay earthbound.
Most would agree, however, that the potential benefits of a timely chest X-ray or mammogram far outweigh the risks. Even an occasional and judiciously planned CT scan may help maintain or restore your health; but avoid advice such as, “I don’t have a clue about what’s wrong, so let’s get a CT scan.” A second opinion is safer. Remember, it took decades for the damaged DNA in dentists to turn into skin cancers. Similarly, avoid being your own doctor and proclaiming, “I would just feel better, Doctor, if you ordered a CT scan.”
Röntgen discovered his new type of ray a few decades after the introduction of general anesthesia and the acceptance of aseptic surgical techniques. These developments, along with the invention of stainless steel, ushered into the modern era orthopedic surgery and the practicality of operative fixation of fractures. Looking ahead 125 years, fractures will still exist. Arthritis and osteoporosis may be fully preventable. Bone imaging techniques will be even more sophisticated than they are today. X-ray imaging may be obsolete, replaced completely by magnetic resonance imaging, ultrasound, or some yet-to-be-discovered alternative. Nevertheless, Röntgen’s discovery and its enduring 125-year legacy deserves recognition and respect.
Nothing is more evocative of Halloween than pumpkins, black cats, and skeletons. Should you want to dress up for maximum effect this season, consider that nobody looks good in a pumpkin outfit and only certain, lovely shaped bodies should go out as cat women. For most of us, that leaves skeletons, which not only allows us to reveal our inner selves but also to reenact a bit of history.
Frescos, paintings, and woodcuts depicting dancing skeletons appeared in the 15th century. There were many of them, so they must have been popular. Artists portrayed royalty and commoners cavorting with corpses and skeletons to remind the living of life’s fragility and the inevitability and universality of death. This allegorical genre became known as danse macabre—dance of death.
Over the following centuries, many musicians adopted the theme, the most famous of which was Camille Saint-Saens’ symphonic poem by the same name. It prominently features the xylophone to simulate the dancers’ rattling bones.
The descriptions so far are representations of skeletons dancing, sometimes naked, sometimes clothed. Far less well documented is the converse—live people dressing up as skeletons. One early depiction comes from an 1831 French lithograph titled the Political Carnival. (Any resemblance to current affairs is purely coincidental.)
Another representation appeared in 1896 newspapers, only weeks after the discovery of X-rays. The article notes that a reigning beauty showed up to a ball in Munich wearing “…a watered silk skirt and close-fitting basque, upon which had been deftly painted the principal bones of the human frame. The ribs, collar bones, arms, thigh bones and spine were outlined in black upon the white background. The idea was not carried above the neck, nor below the knees, and a pair of roguish eyes peeped through a satin mask. The whole thing was dainty in its conception and execution.” At about the same time came the costume depicted above in the lower right, certainly not dainty, from Tibet. A Buddhist monk danced in it to illustrate the impermanence of life, and by extension, of everything.
From my viewpoint as an orthopedic surgeon, I find each of these skeleton costumes wanting in anatomical correctness and completeness, and I cannot recommend any of them to you for your Halloween costume. Rather, I would like to help you choose from current options at Amazon. Possibilities abound, and to ease the burden of the discriminating buyer, I have restricted my selection to costumes for adult humans. Children and dogs are so cute that they can get away with styling cartoonish, anatomically incorrect bones. Adults who want to pay proper respect to the dead and to the beauty of the human skeleton need costumes that to some extent simulate nature, at least enough to keep orthopedist and radiologist party-goers and trick-or-treaters from shuddering.
To begin with, the bones must be white, not multicolored or decorated with psychedelic patterns or bogus arterial patterns. You can select among costumes that are printed just on the front, which I guess are OK if you are staying home and dispensing treats to neighborhood children while just facing forward. For party goers who plan to shout and twist, I advise an outfit that is printed front and back. Some have paint that glows in the dark. Whether this is a plus or a minus is up to you. As a bone lover, I insist that your costume extend at least to your wrists and ankles. You will score extra points with all bone aficionados if your outfit also covers your hands and feet. Get even more points if it has an all-in-one hoodie with a see-through and Covid-approved mask displaying a frightening skull. I know the following are available, but please, no open shoulders, short sleeves, T-shirt dresses, fishtail skirts, body suits with thigh-high stockings and garters, or plunging necklines. One description says “from naked to awesome in just one zip.” You decide whether that’s for you. Another description indicates “concealed fly.” At least that one has an out. Not explicitly described, but other offerings appear to require pretty much stripping the onesie to the knees to relieve oneself.
The fabric is typically nylon or polyester. Some include Spandex. One description indicates “stretchy to fit most builds.” Another says, “shows your figure.” Think seriously about these likely true statements and decide if that is what you want. Also, assess your height in comparison to the costume’s size. Several of the Amazon ads depict models who are height-challenged when compared to the length of their costume’s legs, which gives the leg bones down near the ankles an extremely unnatural, crumpled up appearance.
Finally, the devil is in the details—anatomical correctness. For example, the historical images depicted above are all wanting. Regarding the first image, humans have twelve pairs of ribs, not six. In the second, the rib cage is naturally oval, not busting out in front as on the beautiful Munich fraulein. In the third, a monk with upper arm bones that thick would be weighted down too much to dance.
Among the current offerings, some have no cervical vertebrae at all. You would risk your head falling off. I can cut some slack to the artists that did not get the ball-and-socket nature of the shoulder and hips exactly right, but those joints should be at least at the proper level, not half way up the neck, half way down the chest, or at the waist line. The knees are equally problematic and give me the creeps because in reality the kneecaps are in front of the leg and thigh bones. (Remember the song. It is not “ … the leg bone connects to the kneecap, the kneecap connects to the thigh bone, …). Some artists missed that day in health class and have positioned the kneecap between the two main lower limb bones like a big dot separating two dashes. And then there are the hands and feet. True, the numerous ankle and wrist bones are complexly arranged in nature, and probably nobody will notice any errors if you keep gyrating, but please, at least let’s have five digits on each foot and hand. Then there are several subtleties. From the internet I can’t tell that any of the available costumes have included the hammer, anvil, and stirrup bones residing in our ears; but I can overlook that, since they are too small to concern anybody other than ear doctors. Of great interest to bone doctors, however, is one costume that depicts a broken thigh bone, which has been anatomically aligned and surgically secured with a metal rod. This would support an early return to dancing and would definitely be a conversation starter with any bonehead, especially if the costume is just one zip from awesome to naked.
A final note. This shopping guide is not just about preparing you for Halloween. Many of the advertisements say that your carefully selected skeleton costume is also suitable for theme parties, Mardi Gras, clubbing, and even Christmas. Wouldn’t that be a surprise for Santa. In the meantime, Happy Halloween.
Launching October 20. Available now for pre-order.
“This is how science writing should be done. I loved this book. It has everything I want in science writing: plain explanations, conversational tone, a little bit of the author’s journey, and a fair amount of humor. The book was hard to put down … “Goodreads.
The inaugural post concluded with: “I will compare bone to sewing thread, Tootsie Pops, licorice sticks, and jazz. … Learning should always be fun, which is easy when telling this story. … The blog is an opportunity to extol the wonders of bone as it supports life and captures history. Let me know if you have questions or if there is some aspect of this wonderful substance that you would like to learn more about.”
Now 79 posts later, AboutBone remains true to its original vision. Early on, I was concerned about eventually running out of topics. No way! Between the leads I find and ones that readers send me, I have enough topics that I could hammer your in box with a new announcement weekly. But as enduring and endearing as bone is, we DO have other things to attend to. So I plan to continue to post a new article every 2-3 weeks.
Looking back: Here are five of the most popular posts, whose topics span 3.2 million years from anthropology and the history of anatomy to a thriving 19th century bone business, a 20th century orthopedic mistake with serendipitous results, and a space-age interplanetary application.
Looking forward: After an eight-year incubation, BONES, Inside and Out, will launch October 20. An audiobook version and translations into Korean and Russian will soon follow along with several podcast interviews and virtual book signings. Advance praise for BONES includes:
I loved this book. It has everything I want in science writing: plain explanations, conversational tone, a little bit of the author’s journey, and a fair amount of humor. Goodreads
An expansive and lively treatment of a material most of us take for granted. Kirkus, starred review
Naturally we tend to take things for granted unless something is amiss, and so it is with our bones. Sure, people take note when they have arthritis or osteoporosis, and a fracture commands the bone owner’s complete attention. For the moment, however, appreciate how close to normal your bones are. A good way to do so is to understand that normality is not universal and that there are some amazing and strange ways that bone can go bad—so strange and rare that most orthopedists, myself included, have never encountered a patient so afflicted. However, we do read about these diseases in journal articles, and the topics may appear on certification exams. Here is a brief overview of three rare conditions that will definitely heighten your appreciation of normal bones.
The first is the genetic deficiency of an enzyme, alkaline phosphatase, which bone-building cells need to function. Bone growth and turnover are normally a balance between bone production and degradation; but in this condition, hypophosphatasia, bone is slowly resorbed and not replaced. In the severe early-childhood form of this disease, the ribs melt away, and the patient requires mechanical assistance for breathing. Early death ensues, at least until recently. Now the disease can be thwarted by periodic, lifelong injections of a synthetic form of the missing enzyme.
Although not fatal, the second condition, vanishing bone disease, is even more vexatious because nobody knows its cause. It can occur at any age but shows up most commonly in young adults where large segments of bone in a given region, typically face or upper arm, just gradually disappear. When it attacks the ribs, it can be fatal, otherwise it is just disabling, since the affected part of the skeleton lacks stability. For instance, contracting the muscles in a transformed arm just telescope the limb rather than bend and straighten the joints. Sometimes the process stops spontaneously, but it is not known to reverse. Radiation may provide some benefit but risks later malignant transformation. At times grafted bone can span the defect and improve stability and function.
In the third condition, an overabundance of bone rather than a dearth causes problems. It’s called fibrodysplasia ossificans progressive (FOP). A chemical messenger, bone morphogenetic protein, normally stimulates bone cells to make bone, which is a process integral to bone growth and fracture healing. In FOP, bone morphogenetic protein does not get switched off, and it stimulates bone formation in extra-skeletal locations, starting in the neck and shoulder muscles and gradually working its way down the spine and into the limbs. Any muscle irritation, an injection or bruise for instance, leads to the local formation of an extra-skeletal lump of bone. Surgical excision of the knot leads to more bone formation. The condition begins in childhood, gradually stiffens all joints in the spine and limbs, and makes even self-care activities impossible. Sadly, chewing and chest expansion become restricted, so either malnutrition or pneumonia causes early death.
The first malady discussed, hypophosphatasia, is far more common than the other two and is treatable. The others are exceedingly rare. Total worldwide cases number no more than a few hundred. Awareness of the three allows a glimpse into the amazing and complex life of normal bone, which is worthy of our utmost appreciation.