Tag Archives: bone

Work Smarter Not Harder!

We have all likely heard the saying, “Work smarter not harder.” While this is generally referenced in an academic setting, it is also very applicable in athletics! One of the benefits to being a runner is that it’s a sport people can participate in at any age and nearly anywhere. Unfortunately, however, anywhere from 65-80% of runners get injured in a given year. A large portion of these injuries are related to overuse.

Recovery

It’s a common misconception amongst runners that the harder you push during your runs, the faster you will be on race day. As a result, the majority or runners overdo their “easy” days. This leaves their legs fatigued and tired going into workouts and races. The majority of fitness is gained during a “workout” day, so overdoing easy days reduces your ability to push hard on workout days. To truly maximize their potential, an athlete must focus on their recovery. Recovery is a broad term that includes a variety of factors such as sleep quality, nutrition, and post run stretching and rehab exercises. Monitoring your heart rate is one way to manage your recovery, reduce overtraining, and limit bone stress injuries. 

Managing Heart Rate

Photograph of a smartwatch reading heart rate
Photo by Brooke Trossen

Heart rate monitors are used by runners to train smarter and ultimately race faster. Resting heart rate and heart rate recovery measurements are indications of how an athlete’s body is responding to stress and exercise long term. Heart rate measurements can be used to guide what the pace of a run should be. Heart rate measurements are commonly separated into five “zones.” On different days of the week and stages in a training cycle, a run should fall into the different zones. It may be beneficial for an athlete to also have a general idea of what their heart rate is at a given running pace. If their heart rate is more than 7 beats per minute above the usual rate, it may be a sign that the athlete has not fully recovered from their last training session and that they should continue with easy days until having another intense session. This is also important for runners since the weather conditions can greatly affect the difficulty of a run. Rather than having a goal pace for a given day, it is better to have a goal range of heart rates to make sure the run is best serving the athletes body. This will enable an athlete to get the appropriate effort in whether it is 70° and sunny or 30° with 20 mph winds.

Monitoring heart rate after exercise can also accurately indicate whether or not an athlete is fully recovered. It is important to note that your heart rate fluctuates, so it is more valuable to observe general trends than it is to overanalyze specific data points. A morning heart rate 5 beats per minute above your usual heart rate may be indicative that your body needs more rest or that you are getting sick. The image below shows a chart with ranges of resting heart rates depending on gender and age.

Chart of healthy resting heart rates for men and women with varying ages.
Photo by Jeremy on Agelessinvesting.com

Minimizing Bone Stress Injuries

Photograph of a stress reaction in the femur of a female runner
Photo by Brooke Trossen

Building a training plan with runs in a variety of zones will help limit overtraining and make the development of overuse injuries less likely. A bone stress injury (BSI) is defined as the inability of a bone to withstand repetitive loading. There are varying degrees of bone stress injuries from stress reactions to complete bone fracture. When performing repetitive motions such as running, micro-cracks form in your bone. These micro-cracks are actually healthy because loading your bones makes them stronger. In the process of remodeling, the micro-cracks are healed. Generally, additional remodeling units can be recruited in response to increase loads. The increase in remodeling units present, decreases the amount of bone mass. This results in a decrease in the ability for the bone to absorb energy and an increase in the number of cracks formed. When insufficient time is given for remodeling, the micro-cracks will begin to accumulate and stress reactions and fractures will form. A stress reaction in the right femur of a female runner is shown in the image above. The white highlights represent inflammation in the bone. 

Although overuse injuries are very common in runners, research shows that the use of heart rate monitors can help regulate recovery and positively influence training plans to limit overtraining. 

Down to the Bear Bones: How Polar Bears evolved from Grizzlies to hunt in the Arctic

Katmai National Park in Alaska holds an annual “Fat Bear Week”, in which Twitter followers are asked to vote for the fattest bear in the park. This year’s winner was Holly, somewhere in the range of 500 to 700 lbs. That’s a big bear. However, in 1960, a male polar bear in Kotzebue Sound, Alaska, weighed in at 2,209 lbs. In fact, on average, polar bears weight up to 60% more than Grizzly bears, their closest animal relative. 

A very fat grizzly bear standing on rocks.
Holly, aka Bear 435, the 2019 winner of the Fat Bear Contest. From Katmai National Park via Twitter.

So just how did Polar Bears get so big? Well, as anyone in the Midwest knows, a harsh winter requires a good winter coat. The advantage of thick skin and fur, as well as a higher capacity to put on weight made heavier polar bears more adept to survive. However, bigger bears that could survive the cold were more likely to fall through the ice, so these adaptations required better foot mechanics.

Consequently, polar bears developed a distinctive gait. A rotary gait is a “double suspension” gait, meaning the animal bounces both off the hind limbs and then the fore limbs . This is contrasted from the grizzly bear’s transverse gallop, which involves only one “bounce,” — this loads each limb for a longer time and more vertically. The rotary gait improves stability, giving the polar bear the ability to travel quickly and smoothly on icy surfaces. 

A series of drawings depicting the gait of a galloping polar bear.
A series of drawings depicting the gait of a polar bear. Modified from S. Renous, J.P. Gasc, and A. Abourachid, Netherlands Journal of Zoology (1998).

Another significant difference between the species are their skulls, which, while similar in size, vary greatly in bite force and bone strength. The polar bear has a stronger bite, but a weaker skull. Polar bears are one of the most rapid instances of evolution in surviving species of animals, having evolved from the grizzly bear within the last five hundred thousand years. So why are their skulls weaker if their bite is stronger? 

Simply put: seals are easy to chew. Grizzlies are omnivores, as most bear species. Their diet subsists of salmon, elk, and small game, but includes a hefty amount of vegetation. Polar Bears, in the ice and cold, were forced to eat seals (as well as penguins, fish, even belugas). Seals are largely blubber, providing the caloric intake necessary to sustain these large beasts, but offering little resistance in the chewing process. 

Two line drawings of skulls, one of a polar bear and a grizzly bear
Skulls of the polar (left) and grizzly bear (right). Modified from P. Christiansen, Journal of Zoology (2006).

The polar bear’s skull morphed quickly, elongating to allow it to hunt for seals and fish through small holes in the ice. This weakened and lowered the density of the skull; however, because the seal-heavy diet required less effort to chew than vegetation, there was no selective advantage to a skull reinforcing. So, with a more efficient gait and a stronger bite, the polar bear developed into a killing machine in the icy north.

Interested in more of the polar bear’s hunt? Learn about how they can swim for hundreds of miles, or to see these arctic advantages in action, check out this video of a polar bear hunting a seal.

In the Womb: Alive and Kicking

For a pregnant woman, it can be a thrilling moment when her baby kicks for the first time. Women have described the feeling as a flutter, a tumble, or a gentle thud. However, these movements are not only exciting because they are unpredictable but because they indicate healthy fetal development. 

Although a pregnant woman may not feel her baby’s kicks and punches until 18 to 25 weeks of pregnancy, fetal movement may begin as early as seven weeks and science shows that it is crucial in the development of joints and bones. In fact, a lack of fetal movement can be a sign of abnormal musculoskeletal development and other poor birth outcomes. In the last decade, scientists have begun to wonder how mechanical factors have positive or negative effects on a baby in utero. 

MRI scan animation of developing fetuses
An animation composes of MRI scans of fetal movement during various stages of development. (Image: © Stefaan W. Verbruggen, et al./Journal of the Royal Society)

In particular, researchers Stefaan Verbruggen and Niamh Nowlan at Imperial College in London decided to take a deeper look at the mechanics of these fetal movements through several different studies. As it turns out, neonates can throw a pretty strong punch. In one experiment, researchers saw that fetal kicks can incur an impact of 6 lbs at 20 weeks, 10 lbs at 30 weeks, and less than 4 lbs beyond 30 weeks of pregnancy. The force of fetal kicks decrease after 30 weeks due to the limited amount of space for the baby to move. 

In addition, the force of fetal kicking was also observed in three different neonatal positions: typical (head-first), breech (feet first), and twin fetuses. These studies revealed that twin fetuses can exert the same amount of kick force and motion as a healthy singleton fetus in the typical head-first position. However, fetuses in the breech position showed significantly lower kick forces and lower stress and strain in their hip and knee joints. This discovery might explain why babies in the breech position have the highest probability of being born with hip problems.

simulated strain concentrations in a fetal leg
Simulation of principal strain which indicates that strain increases with gestational age for fetuses in the head first position.  Modified from Verbruggen et al., 2018.

 In another study, three mothers volunteered to have their wombs monitored via MRI so that the researchers could observe the geometry, force, and frequency of fetal motion. It was found that fetal muscles are able to produce nearly 40 times more force than the kick itself. The magnitude of force exerted by these muscles confirms the importance of fetal kicks for proper growth of the hip and knee joints. This information is helping scientists and doctors connect the dots between neonatal environment and newborn joint abnormalities.

Interested in learning more? Check out some of the new technology being developed to further this study!

Why Not Running Could Lead to Bad Bone Health

Is staying active and fit enough to avoid bone loss? Maintaining high bone mineral density (BMD) is important for preventing osteoporosis, fractures, and other conditions associated with bad bone health. However, high-impact sports that often involve running or jumping might be necessary in order to preserve and improve BMD among athletes of all ages. Low-impact sports (such as cycling) as well as weight training may not be enough to maintain high BMD and avoid associated health risks.

Among senior athletes, a 2005 study examined BMD among those competing in the Senior Olympics [1]. They concluded that competing in high-impact sports (basketball, running, volleyball, track and field, and triathlon) correlated with a higher BMD compared to low-impact sports (including cycling, race walking, and swimming), among other factors such as younger age and absence of obesity. Similar results were found in a Norwegian study comparing elite cyclists and runners, as cyclists—despite heavy weights programs as part of their training—were shown to have lower BMD than runners [2].

On the other hand, a study comparing younger men and women showed BMD increases as a result of resistance training, but only among men in the spine and neck. Women showed no significant BMD increase [3].

Bone mass changes with age, peaking for both genders at around 30-40 years old.
Modified from Wikimedia Commons

In light of unsubstantial data to support resistance training as a method to increase BMD, why do many articles online praise weight training as the perfect way to promote healthy bones? Online articles with catchy titles claim that “resistance training is really the best way to maintain and enhance total-body bone strength” and it “increases bone mineral density,” but either provide no sources or cite research that showed no significant increase in BMD [4] [5] [6] [7]. Promoting weight training as the perfect solution to late-in-life bone problems sounds wonderful, but formal research concerning its effects on BMD is as best contested and inconsistent. It is not a blanket solution for those looking to improve bone health through staying fit, and should not be used as the only supplement to other low-impact sports such as cycling or swimming.

Running is among high-impact sports that can promote bone health
Modified from Wikimedia Commons

Ultimately, it seems as though staying fit through low-impact sports and weight training might put an athlete at risk for low BMD and associated health risks. Regular participation in high-impact sports (such as running, basketball, and volleyball) has been shown to correlate with higher BMD across different age groups and athletic skill levels [1] [2]. Even though cycling and weight training might cover all the bases from cardiovascular and strength fitness standpoints, bone health requires more impact than just staying fit.

For further reading on the relationship between running and bone health and how other factors play a role, look at Runner’s World’s article.

 

[1] Leigey D, Irrgang J, Francis K, Cohen P, Wright V. Participation in High-Impact Sports Predicts Bone Mineral Density in Senior Olympic Athletes. Sage: Sports Health. 2009. [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3445153/]

[2] Andersen OK, Clarsen B, Garthe I, Morland M, Stensrud T. Bone health in elite Norwegian endurance cyclists and runners: a cross-sectional study. BMJ Open Sport & Exercise Medicine. 2018. [https://bmjopensem.bmj.com/content/4/1/e000449]

[3] Almstedt HC, Canepa JA, Ramirez DA, Shoepe TC. Changes in bone mineral density in response to 24 weeks of resistance training in college-age men and women. Journal of Strength and Conditioning Research. 2011. [https://www.ncbi.nlm.nih.gov/pubmed/20647940]

[4] Heid, M. (2017, June 6). Why Weight Training Is Ridiculously Good For You. Retrieved from http://time.com/4803697/bodybuilding-strength-training/

[5] (2018, February 2). 10 Health Benefits of Strength Training That Are Backed by Science. Retrieved from https://www.myoleanfitness.com/health-benefits-of-strength-training/

[6] Nelson ME, Fiatarone MA, Morganti CM, Trice I, Greenberg RA, Evans WJ. Effects of high-intensity strength training on multiple risk factors for osteoporotic fractures. A randomized controlled trial. JAMA. 1994. [https://www.ncbi.nlm.nih.gov/pubmed/7990242]

[7] Going SB, Laudermilk M. Osteoporosis and Strength Training. American Journal of Lifestyle Medicine. 2009. [https://journals.sagepub.com/doi/abs/10.1177/1559827609334979]

A Mystery: How Can Distance Runners Avoid the Most Common and Dreaded Injury?

Man running on track surface.
Photo by Steven Lelham on Unsplash

Stress fractures are small cracks in the bone produced by repetitive stress. The most common locations include the tibia, fibula, and navicular bone [1]. An article by Crowell and Davis on gait analysis stated the occurrence of bone stress injuries in track and field athletes (male and female) to be as high as 21% [2]. Furthermore, approximately 50% of female track and field athletes have had at least one stress fracture [3] . Bone stress injuries  can have a devastating effect on the athlete, their team, and the willingness of these runners to continue to compete. The only treatment for stress fractures is to completely stop running for an average of 6-8 weeks [4].   Runners have no clear and confirmed guidance on injury prevention or appropriate volume of training.

Female Athlete Triad triangle consisting of energy deficiency, low bone density, and menstrual disturbance that make up the three corners of the triangle.
Female Athlete Clinic, Children’s Wisconsin, 2019

Most studies of stress fractures in women have been looked at from a purely biological standpoint. As seen in an article by Hames and Feingold, the female athlete triad is often considered the main reason for the large number stress fractures in female distance runners [5]. The female athlete triad is the connection between energy deficit (due to excessive exercise or under nutrition) and irregular hormone levels which cause a decrease in bone mineral density.  However, despite normal bone density and hormone levels, many competitive runners continue to suffer from season or career-ending stress fractures [6].

Taking a more mechanical rather than biological approach, the source of stress fractures can be explained in the same way as any other material fatigue. A fatigue fracture is caused by a repetitive cyclic stress. For example, consider a paper clip. When a paper clip is bent just once, it does not break. After bending it several times, the paper clip will eventually fracture. This same concept can be applied to bones with forces caused by running. There are two main differences. First, while a paper clip will break through an abundance of minimal stresses over an extended period of time, the bone works to regenerate, with the help of osteoblasts, to compensate for added stress [7].  However, the body’s work to restore the bone is unsuccessful if there is not enough time for repair. Secondly, unlike a paperclip, muscles surround the bone that work to absorb the impact stress. At a given force, the muscles are unable to adequately protect the bone. With a high force frequency and magnitude, a bone stress injury occurs.

While the reason behind stress fractures is known, the mystery of  how to reduce the risk remains. For many competitive runners, dramatically increasing recovery time or reducing mileage is not an option. There are several different factors than might play a distinct role in the solution, including footwear, running form, and running surfaces.

For more information, visit the following articles:

Preventing Stress Fractures“,

Risk Factors for Recurrent Stress Fractures in Athletes“,

Biomechanical Factors Associated with Tibial Stress Fracture in Female Runners.”

“The Relationship between Lower-Extremity Stress Fractures and the Ground Reaction Force: A Systematic Review.”

References:

[1] “Breaking Point: when running stress gets too much.”

[2] “Models for the pathogenesis of stress fractures in athletes.

[3] “Biomechanical factors associated with tibial stress fracture in female runners.”

[4] “Stress Fractures of the foot and ankle.”

[5] “Female Athlete triad and stress fractures.” 

[6] “Sex-related Differences in Sports Medicine: Bone Health and Stress Fractures.”

[7] “The relationship between lower-extremity stress fractures and the ground reaction force: A systematic review”

Why do bone fractures take a long time for healing?

An athlete walking on crutches across the field - from The Washington Post
An athlete walking on crutches across the field – from The Washington Post

Have you observed that someone around you has broken their arms or legs? Bone fracture is a complete or incomplete break of bone continuity. And it is very common in our daily lives that there are more than 3 million cases in the U.S. per year. Many events may cause bone fractures, such as falls, car accidents or sports injuries. So, do you know how long it takes for the fracture to heal?

Locking compression plate used for treatment of a proximal femoral fracture - by Bjarke Viberg on ResearchGate
Locking compression plate used for the treatment of a proximal femoral fracture – by Bjarke Viberg on ResearchGate

Bone fracture healing is a repair process that consists of multiple stages. There are two types of repair: primary and secondary bone healing. Primary healing only occurs with the application of rigid internal fixation, for example, a compression plate. The rigid fixation provides absolute stability, and primary healing includes attempting to reconstruct the continuity between fracture fragments.

In contrast, secondary healing occurs when the fixation is not rigid. For secondary healing, there are four stages: inflammatory response, soft callus formation, hard callus formation, and bone remodeling. After the bone fracture, torn vessels form hematoma, which is localized bleeding outside of blood vessels within the fracture site and provides a foundation for the following stages. The inflammation begins immediately and continues until the cartilage or bone begins to form. During the inflammatory phase, stem cells migrate to the fracture site, form the granulation tissue (new connective tissue and microscopic blood vessels), and release growth factors that stimulate bone formation. This phase usually lasts 3-4 days and may last up to one week.

In the second week after the bone fracture, soft callus (cartilage) begins to form. At this stage, cells within periosteum (the membrane covers the outer surface of the bone) and granulation tissue begin to proliferate and differentiate into chondrocytes until they bind with each other. Chondrocytes are the cells found in cartilage connective tissue and constitute the “bridging callus”. In addition, the amount of newly formed cartilage is related to stability, that less stability leads to more cartilage. The formation of soft callus will be completed within the first three weeks after the fracture, which means this phase needs approximately two weeks to complete.

The following stage is hard callus formation, also known as endochondral ossification. It is a replacement of cartilage with bone. Mineralization of cartilage develops from the ends to the center of the fracture site. The trabecular bone would be formed from osteoblasts (cells that synthesize bone tissue) on the newly exposed mineralized surface. Finally, all the cartilage turns into trabecular bone and forms the “hard callus”. At the end of this phase, the injured bone will be able to recover sufficient strength and rigidity for rehabilitation exercise.

4 stages of secondary fracture healing. Stage 1: Inflammatory response. Stage 2: Soft callus formation. Stage 3: Hard callus formation. Stage 4: Bone remodeling - from Bigham-Sadegh & Oryan, International Wound Journal 2014
4 stages of secondary fracture healing. Stage 1: Inflammatory response. Stage 2: Soft callus formation. Stage 3: Hard callus formation. Stage 4: Bone remodeling – from Bigham-Sadegh & Oryan, International Wound Journal 2014

The final stage of secondary bone healing is bone remodeling. This phase starts 3-4 weeks after the bone fracture. Bone remodeling is a slow process that may last 6-9 years, which is 70% of the total healing time. In the remodeling, osteoclasts (cells that break down bone tissue) resorb the trabecular bone, and osteoblasts deposit compact bone. It is a process of equilibrium between resorption and formation, that the trabecular bone is replaced by compact bone, in order to recreate the bone to appropriate shape and adapt to mechanical loads and strain.

In clinical treatment, bone fracture usually takes 6-8 weeks to heal. However, it does not mean the bone is totally cured. When the doctor says the treatment is finished and it is fine to let the body free from the fixation, the bone actually is at the beginning of the final stage since the bone remodeling may take several years.

For more details of the bone fracture healing, please check the following video:

For further reading, please click here and here.

Canine Hip Dysplasia: What You Should Know

Canine hip dysplasia (CHD) is a degenerative hip disease that tends to develop in large breed dogs, such as the Bernese Mountain Dog, affectionately referred to as Berners. CHD significantly decreases the quality of life of a dog and often leads to complete immobility if left untreated. Experts estimate that about 28% of Berners are affected by dysplastic hips, making them the 8th most susceptible dog breed.

Bernese mountain dog with superimposed image of hip ball and socket joint.
Image from Packerland Veterinary Clinic.

At birth, puppy skeletal structures are largely composed of cartilage that is much softer than bone. This softer cartilage is able to adapt much more easily to the rapid growth that occurs during the early months of a dog’s life. In their first few months, Berners will typically gain 2-4 pounds per week, which adds increasingly large stresses to their developing bones and joints. While genetics play a large role in the susceptibility of a dog to develop CHD, the loading cycles and forces on the cartilage greatly shape the development of the dog’s hip.

Correctly formed hip versus a deformed femur head and shallow hip socket.
Image from Dog Breed Health.

The hip is a ball and socket joint, where the head of the femur, the very top of the dog’s leg, should fit perfectly into a socket in the pelvis. If the ligaments that hold the femur in the hip socket are too weak or damaged at all, the positioning of the

Evenly distributed forces on a correctly developed hip joint versus force concentration acting on a dysplastic hip joint.
Modified from The Institute of Canine Biology.

hip joint will be off and the hip will be subjected to unbalanced forces and stresses over the course of the dog’s life. The distribution of forces experienced by the hip joint in normal hips is evenly spread, while dysplastic hips are subjected to a stress concentration on the tip of the femur. These unnatural forces will cause laxity in the hip joint, leading to instability, pain, and often times the development of osteoarthritis.

 

There are also a number of environmental factors, many of which are inherent to large dog breeds, that dramatically increase a dog’s susceptibility to CHD. A study by Dr. Wayne Riser concluded that factors such as oversized head and feet, stocky body type with thick, loose skin, early rapid growth, poor gait coordination, and tendency of indulgent appetite all contributed to the development of CHD. All of these features are generally inherent to large breed dogs, such as Berners, so great care must be taken in order to mitigate their effects on the quality of life for these dogs.

Multiple studies have shown that treatment that is implemented early in the dog’s life is much more effective than late-in-life treatments. CHD warning signs can be seen in puppies as young as 4 months old, and most veterinary professionals agree that if scans occur at 2 years of age, the most optimal time for treatment has passed. Since larger stresses will be put on the hip joint as the dog grows, surgical repairs, or changes in diet and exercise, are most effective if implemented before the dog’s skeletal frame is completely developed.

 

timeline of canine hip dysplasia development
Modified from The Institute of Canine Biology

Additional information regarding this topic can be found at The US National Library of Medicine or The Journal of Veterinary Pathology.

Skeletal Support Seekers’ Success (So Far)

Bones break, and broken bones need time to heal, or regrow. Fans of J.K. Rowling’s Harry Potter series are quite familiar with the concept of bone repair, as Harry is once required to drink a Skele-Gro potion to magically (and painfully) regrow his arm bones overnight. Now, as fantastic as it would be to completely fix broken bones in a few hours, modern medicine has not yet discovered that secret of the Wizarding World; however, several treatments have been developed in attempts to speed the rate of fracture repair as well as increase the comfort of the patient (take that, Skele-Gro).

Images of a broken bone and the progression of a callus being formed over time
Image from Cambridge Fracture Clinic

For those unfamiliar with the process of bone repair, a quick overview is in order. In short, inflammation provides stability to a fractured area, and over the course of several weeks fibrous tissue forms a callus around the fracture which is eventually replaced by bone. The mechanical environment at the fracture site is influential in healing, with factors such as hormones, vitamins, minerals, diet, fluid flow, and physical and electrical stimuli affecting healing rates. With these factors in mind, engineers and scientists are attempting to speed bone regrowth.

Low-level laser therapy (LLLT) is one practice found to accelerate bone healing. A study published in Lasers in Medical Science revealed that LLLT stimulates bone cells in fracture areas which increases the rate of callus development. Tests performed on the broken tibial bones of two groups of white rabbits demonstrated that bone mineral density at fracture sites remained higher in the group receiving laser therapy than in the control group throughout healing. 

However, post-mortem tests revealed that bones healed under LLLT endured significantly lower maximum stresses than intact bones or bones healed under normal conditions. This is a controversial result, as other studies have concluded opposite findings, so despite the enhanced growth resulting from LLLT, the authors of this study agree that additional experiments are necessary to satisfactorily settle this issue.

Images of stress concentrations in and around a solid titanium implant and porous titanium implants with various levels of bone ingrowth
Modified from Spoerke, et al., Septermber 2005

Surgical implants are another device used to facilitate bone healing. Most bone implants are made of titanium due to its lightness, durability, and biocompatibility. While these supports effectively immobilize and position bones for proper healing, some patients experience complications later on, largely due to stiffness differences between bone and titanium—resulting stress concentrations increase risk of fracture or implant loosening. Titanium foam implants coated in an organoapatite (OA) layer are a developing solution to this issue, described in detail in an Acta Biomaterialia article.

The porous surface of titanium foam, studied in vitro, substantially decreases implant stiffness, thus enabling stress to be more evenly shared between the foam and surrounding bone. Allowing bone ingrowth into the pores also reduces stress concentrations at the materials’ interface which helps alleviate risk of implant failure. Furthermore, the OA coating on the foam stimulates bonding between bone tissue and the implant, thereby increasing stability. The success of these studies suggest that titanium foam is ready for in vivo testing. 

Check out this video on the advantages of titanium foam:

Although the results of these fracture repair treatments are still a far cry from those achieved with Skele-Gro, further research and development regarding bone regrowth may lead to significant advances in the very near future. Interested in learning more? Check out articles on other developing fracture treatment technologies here and here.

3-D Print a New Leg for Your 4-Legged Friend

3-D printing is a quite exciting technology that has come to light in recent years. The process involves a nozzle much like in a regular inkjet printer that layers material upon material to build up a 3D structure. The printer receives this data from a computer designed file that maps out where the printer should add material. Combine this with filler material that serves to hold everything in its final upright position, and the final product is born, after setting and clearing off the filler. This process has been used to make many different things, from simple objects like phone cases and luggage tags to complex scaffolds used to hold cells for tissue engineering, or as in this post, specific implants for dogs and other animals. The usual types of orthopedic implants that have somewhat of a cookie cutter size distribution for humans do not always fit in dogs or other animals. So, 3-D printing has been employed to create implants used to repair and replace bones in veterinary situations.

Examples of computer-modeled custom implants
Examples of computer-modeled custom implants on dog legs

The most prominent veterinary application for 3-D printed implants is dogs. This is due to their slight differences in body type, even within breeds, that can make finding a pre-sized and pre-made implant difficult to find. One such example of this is a dachshund, named Patches, that received a custom made skull implant after other implants were found to be ineffective or dangerous to her long term health. Patches had a brain tumor, one that grew to a very large size and began encroaching on her eyes. The tumor was successfully removed, but the process involved the removal of large portions of her skull, leaving her brain unprotected. If a preexisting implant were tried, the way it would fit would leave her head vulnerable to an impact, making the implant quite pointless. A 3-D printed implant was made, and old Patches made a full recovery.

The process involves taking a CT scan of the area in question and gaining an understanding as to the layout of the area. This allows designers to make a 3-D model of the implant using a computer, and that model can be printed out using a 3-D printer. In the case of implants, titanium is usually used due to its biocompatibility and great mechanical strength. The implants can be used for surgery and repair, or an array of other applications, even studying the cranial activities of primates. In any case, these exciting new developments in 3-D printing are leading to advancements in the medical and biological fields. So, the next time you fire up you 3-D printer to make a cool-looking hood ornament, know that the same technology is at work, saving lives and giving scientists new knowledge about animals they previously had no good way of studying.

Sources:

<https://www.3dprintingmedia.network/dog-3d-printed-titanium-bone/>

<https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5482398/>

<https://www.nytimes.com/2018/09/25/science/3d-print-dog-skull.html>

The future of hearing might be in your bones

 

How many times have you walked up to someone and were unable to get their attention because they had headphones on? This is an increasingly important issue as we become more connected to our devices and less connected to the world around us. Recently, several companies, including Aftershokz and Pyle, have tried to solve this issue by creating bone conducting headphones.

How does bone conduction work?

diagrams of the inner ear displaying the differences in bone and air conduction
Modified from Furuichi, GoldenDance 2008

 

Although these devices may seem futuristic, bone conduction has been used for hundreds of years, especially in applications involving music. In the 18th century, Beethoven, although he had lost much of his hearing, was able to listen to his music by clenching a rod in his mouth that was attached to his piano. In most situations, we hear sounds using air conduction in our ears. Our outer ear channels vibrations that travel through the air into our ear canal where our eardrum transmits these vibrations to our cochlea. Inside the cochlea, each frequency resonates at a different location along the basilar membrane, and these mechanical waves are converted into neural signals that are transmitted to the brain. Bone conduction works by sending these vibrations through our bones directly to the cochlea and bypassing the outer ear and eardrum.

How is bone conduction used?

Szweda, BAE Systems 2015

As time and technology have progressed, bone conduction has become increasingly more common in commercial devices. Currently, the most prevalent use of bone conduction is in hearing aids for those suffering from outer or middle ear damage. Bone conduction is also used in applications where users must still be aware of their environment while listening to music or other sounds. Modern devices are able to transmit frequencies between 20 and 20,000 Hz. This range is perfect for listening to music and voices at reasonable volumes. Bone conduction can also be used in more demanding situations. BAE Systems has utilized bone conducting technology to manufacture helmets that allow soldiers on the battlefield and sailors competing in America’s Cup to communicate with each other while still being able to hear their environment. These grueling environments make perfect use of bone conducting device’s durability in hazardous conditions including water and dust.

What is the future of bone conduction?

image of LG G8 smartphone depicting the cystal sound OLED speaker screen
LG G8 Smartphone, LG Electronics 2019

Although many devices that utilize bone conduction like Google Glass and Zungle Audio sunglasses have not yet become mainstream. This technology still has a bright future. On February 24, 2019, LG unveiled its G8 smartphone which eliminated its top speaker for receiving phone calls. Instead, LG’s design creates sound by vibrating its front glass panel. The user can then press the screen against his or her face conducting the sound through his or her cheek to better hear the person on the other line. As implementations like these become more common, the technology behind bone conduction will only get better. It may seem like the future, but the next headphones or pair of sunglasses you buy might have bone conducting technology inside of it.

 

For more information on this story, check out The Verge and CNN.