What Makes Someone More Likely to Tear Their UCL?

It takes a lot to make a professional athlete collapse to the ground during a game. After throwing a pitch on September 14, 2019, Toronto Blue Jays pitcher Tim Mayza knelt on the side of the mound while clutching his arm, expecting the worst. The next day, MRI revealed that what he had feared: Mayza had torn his Ulnar Collateral Ligament (UCL).

player following through after throwing baseball
Photo by Keith Johnston on Unsplash

Because of UCL reconstruction, or Tommy John, surgery, this injury is no longer the career death-sentence that it once was, but there is still a long road ahead for Mayza. He probably will not pitch in a game again until 2021. Sadly, this injury is only becoming more and more common among MLB pitchers. In the 1990s, there were 33 reported cases of UCL tears by MLB pitchers. In the 2000s, this number more than tripled to 101. From 2010 to the beginning of the 2015 MLB season, 113 UCL reconstruction surgeries had already been conducted. It has become so common that surgeons have called it an epidemic, and researchers in the US and abroad are attempting to find a way to combat this increase.

Digital image of elbow joint, with a small, red tear in the UCL
Orthopaedic and Neurosurgery Specialists, 2019

The UCL connects the ulna and humerus at the elbow joint, and its purpose is to stabilize the arm. During the overhead pitching motion, the body rotates in order to accelerate the arm and ball quickly, putting a large amount of stress on the UCL. In fact, according to a study by the American Sports Medicine Institute, the torque, or twisting force, experienced by the UCL during pitching is very close to the maximum load that the UCL can sustain.

Recently, many studies have investigated factors that could make pitchers more susceptible to UCL injuries, with a hope of identifying ways to prevent them. One of the biggest findings has been the correlation between UCL tears and pitch velocity. According to a study from the Rush University Medical Center, there is a steady increase in the frequency of UCL tears as max velocity increases. This makes intuitive sense, as more torque would be required to accelerate a baseball to the higher velocities. While this finding does have a very strong correlation, it does not help the players avoid injuries. Pitchers are unlikely reduce their velocity because it would also decrease their effectiveness, so another answer must be found.

The University of Michigan conducted another study, and found that, in addition to velocity, the number of rest days between appearances decreased by just under a full day for pitchers who later needed Tommy John surgery. While this does not seem like a large number, starting pitchers typically only receive 4 days of rest between starts, so the extra .8 days is equivalent to a 20% increase in rest time.

Because of these findings, the MLB has increased the max roster size from 25 to 26 for the 2020 season, with the hope that teams will use the extra player to reduce the frequency that each pitcher is used. In addition, pitch counts in Little League Baseball have had a positive effect on youth injuries. This can be explored further here. This discovery has already made a tangible impact on Major League Baseball, and hopefully more findings will reduce the rate of UCL tears in the future.

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.

The Mystery Behind the ‘Folded’ Brain

 

Picture of a walnut which has a strong similarity to a human cerebral cortex
Image by Ulrike Leone from Pixabay

Have you ever wondered why one of the most mysterious organ in our body, the brain, has a distinctive shape which has a strong resemblance to a walnut? Or, what are the major factors that could play a significant role in developing its particular shape, with crests and valleys, that wires our motions, senses, feelings and thoughts, which makes each one of us a unique human being?

Brain cortex of 34 different species which indicates relative size and foldedness
From Heuer, K. et al., Cortex 2019 High-res version: https://doi.org/10.5281/zenodo.2538751

For almost a century, the researchers from various different disciplines such as, neurology, engineering, evolutionary biology and applied mathematics have tried to solve the enigma behind the convoluted nature of the cortex, i.e. the outermost layer of the brain. Although the degree of convolution has shown to vary proportionally with the size of the brain among different species, as was shown in a recent study, this (un-)foldedness trait can not be attributed to the size of brain only, while some of the human brain disorders, such as epilepsy, might include the smooth brain aspect,  i.e. lissencephaly.

Interestingly, the human brain is not always folded throughout its stay in the womb. The gyrification (development of gyri and sulci, the two characteristics of the cerebral folding) begins only after the mid-gestation (sixth month of fetal life) and further continues to develop postnatally until adulthood. This remarkable phenomena of the brain has lead the researchers from the University of Jyvaskyla, Harvard and Aix-Marseille to collaborate and startlingly they had been able to replicate this unique behavior of the brain on 3D-printed soft composite layered gel samples using smooth fetal brain morphology obtained from magnetic resonance images (MRI) as a starting point. According to the first co-author Dr. Tallinen from their original research paper which is published in Nature Physics in 2016, when this composite layered gel is submerged in a jar of solvent called Hexanes at room temperature for 20-30 minutes,  the differential swelling of the outer layer of the gel is observed, and this leads to the formation of sulci and gyri which is similar in morphology to the cortex of the brain and occurs in a similar relative time frame that is observed in real fetal brain development. Another great article written on this study is also published in TheHarvardGazette!

The theory behind this naturally and experimentally observed cortical patterning can be explained by mechanical principles, and is a result of the mechanical instability generated by constrained cortical expansion due to growth. The computer simulations of gyri and sulci formation which was performed by researchers from Stanford University on 2015 further support this mechanistic perspective such that the mechanical environment and neuronal growth rate on preferred orientations plays a crucial role in controlling the gyral and sulcal pattern formation. Axons or the nerve fibers, which are the transmission cables of our nervous system, tend to respond to mechanical stretch during growth by dynamically adjusting their length, which ultimately serves as a regulator for cortical folding.

Interested in reading more on why our brains are folded? Check out these impressive articles from LiveScience and McGovernMIT!

Also check out this cool TED video from Prof. Suzana Herculano-Houzel 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.

Look Strong, Be Strong, or Be Safe?: The Perils of a New Deadlifter

So, you’ve started deadlifting, but you’re not sure if you’re just weak, or if you’re going to break your spine, and there are plenty of “gym bros” slamming the weights, grunting, and walking around wearing equipment (wrist straps and back belts) that says “I’m literally too strong for my own body.” So, what do you do? Do you need to buy that stuff too?

This blog post will walk you through a biomechanical analysis of the deadlift while wearing supportive equipment, in the hopes of helping you face this daunting task.

First, let’s look at the proper form and muscles recruited in the Deadlift.  As can be seen in the graphic below, the lift begins on the ground in a hinged squat. From A to C, The gluteus maximus (butt), trapezius and lower erector spinae (long muscles that run alongside the spine) are primarily activated, whereas from C to D, the hip extensors and numerous smaller upper back muscles help to “lock out” the form, with the forearms supporting the load throughout.

Graphic of a side view of the proper deadlifting motion
Graphic Depicting Proper Form

The science of using wrist straps as discussed here.  Your forearms are significantly weaker than your gluteus and back, and as such, they will fail first. A comparison of different kinematic variables as a function of wrist straps and unsupported showed a higher activation in the back when using straps.  This means, when using wrist straps, you reduce the load on your forearms, which allows you to go heavier with weight.  In essence, it takes grip strength out of the lift.

Improper form, like arching your back, hips rising too early, leaning too far forward, or many other small inefficiencies can lead to concentrated shear stresses between the vertebrate in the back (not good), excessive reliance on small ligaments in lower back (not good), and high stress concentrations at the moment hinge (especially not good considering your lower back is a nerve junction between your sciatic and spinal nerves).  So how do you prevent this?

Many people instantly reach out to supportive equipment as their saving grace, but does this really prevent injury or does it just add a false sense of security to allow dangerous form? Studies by Thomas and Kingma both look at the effectiveness of weightlifting belts in protecting your spine in various loading conditions.  Although I encourage you to read them and discover their findings for yourself, they both reach generally the same conclusion.  Belts might help, by increasing Internal Abdominal Pressure (IAP) says Thomas, and by decreasing spinal load, tested by Kingma, however, any benefit is nominal.

As far as my suggestion goes, you should begin deadlifting at lower weights, without a belt or straps, until you get a feel for the form.  This will begin to increase your strength in the smaller muscles and form muscle memory required for heavier lifting.  Listen to your body. If a lift went well, and you think you can increase the wight without sacrificing form then go up in weight. Eventually, a weightlifting confidence will step in, and you’ll be able to determine for yourself which strength you want to strive for (grip strength, or bigger deadlift numbers).

If profane language is no issue for you, I STRONGLY encourage watching the YouTube video appended below. Eddie Hall, a now retired professional strongman, owns the record for the ONLY 500 kg Deadlift, and he most certainly knows what he’s talking about.

PS he trains without any supportive equipment, and safe to say he’s lifting heavier than you.

Continue reading Look Strong, Be Strong, or Be Safe?: The Perils of a New Deadlifter

Brace yourself… You might need surgery

A surgery? For my PCL? Could be more likely than you think.

Usually hiding behind it’s annoying and commonly ruptured brother the ACL, the PCL (posterior cruciate ligament) is a durable ligament that usually doesn’t cause problems for athletes… until it does.

Because of the strong nature of the ligament, injuries that tear the PCL are usually sudden and traumatic. Think car accidents, falling hard on a bent knee… you get the picture. When enough force is applied to the top of the tibia, the tibia can be pushed backwards, past the threshold of the PCL. Even though the PCL does its best to hold your femur and tibia together in the right spot, it just doesn’t hold up to the brute force of a dashboard. These injuries can usually be diagnosed by the presence of a “sag.” When your doctor holds your bent knee up, it looks like your shin bone is sagging underneath your knee. This is your torn PCL crying for aid.

A photo showing the location of the PCL and ACL inside of the right knee. The ACL crosses from left to right over the PCL. Both are attached at the top to the femur and at the bottom to the tibia.

When it comes to fixing these injuries, the nonsurgical approach has typically been recommended for low-grade tears that don’t totally rip the PCL apart. These braces are attached to the leg right above the knee, and are supposed to hold the bottom part of your leg under the knee in place. This prevents from your knee from going too far forwards and backwards, and allows scar tissue to build up over your PCL. While your body tries to heal itself with scar tissue, you will work with a physical therapist to build up your quad strength and restore your range of motion. Over 80% of athletes are able to return to play after bracing their knees.

A PCL brace is shown in place on a knee. There are two stabilizing straps above the knee, and two below the knee. They are connected by a metal frame that meets at a hinge joint over the side of the knee.

However, surgery, which was once only reserved for extreme PCL tears, is now seen as a viable, cost-efficient option for even low-grade tears. PCL surgery is intended to restore normal knee biomechanics and stability to about 90% of their post-injury strength. Sometimes, a part of the Achilles tendon is used to create a graft, or a “new” PCL. This is called an allograft, and results in safer and shorter surgeries (8). Within a month, the athlete can walk and bear their own weight. After six months, athletes are able to return to sports.

In theory, surgery sounds like the most “permanently good” option there is for fixing your PCL. However, no scientific studies have yet been done that can accurately compare the return-to-play rates, or even the relative healing of people in braces versus people who immediately got surgery. When people don’t comply with their treatment plans (aka, take off their braces early, skip physical therapy after surgery, etc.) the data for comparisons between bracing and getting surgery aren’t clear. While your PCL may be out of commission, so is the jury on this one. At the end of the day, the best treatment method for you is dependent on the mechanism of injury, severity of your injury, and whether you plan on listening to your doctor or not!

For more info on PCLs:

Posterior Cruciate Ligament Injury

Management of PCL tears

What an Optimized Running Gait Can Do for You

Running is one of the oldest and most common forms of exercise, but there are many ways that running mechanics vary from person to person. Identifying the different running gaits is important so that their efficiencies and effects on the body can be analyzed. Injuries in runners are common and having an understanding of how different gaits apply stresses on the body differently can be used to educate runners on how to run in a way that will reduce the risk of injury.

Running with poor mechanics can lead to overuse injuries, which are more common than acute injuries in serious runners. The majority of these injuries occur in the leg either at or below the knee and include patellofemoral pain syndrome (PFPS) and medial tibial stress syndrome (shin splints). Running gait analysis can be used to identify the poor mechanics and the potential risks associated with the mechanics. Further studies have grouped the variations so that the effects of similar gaits can be identified. Extensive analysis has led to the identification of several potential variations in running gait.

A study at Shanghai Jiao Tong University‘s School of Mechanical Engineering determined the effects of step rate, trunk posture, and footstrike pattern on the impact experienced by the runner. Data was collected by instructing runners to run with specified gait characteristics. Sensors made used to make sure that the gait was correct and the impact forces on the running surface were measured. This study showed the lowest impact was experienced with a high step rate, a forefoot strike pattern, and an increased anterior lean angle. Limiting the impact reduces the effects of the loading. As a result, running with these gait characteristics reduces the risk of knee pain and stress fracture in the tibia.

Runner on treadmill with attached sensors following instructions to modify gait
from: Huang, Xia, Gang, Sulin, Cheunge, & Shulla, 2019

While the most important factor in this analysis is how forces are translated through the body, this is difficult to measure directly. The technology does not exist to measure these forces accurately and noninvasively. Since invasive techniques would not allow the person to run normally, indirect ways of measuring this data have been developed. One of these alternatives involves collecting kinematic data which can be used to calculate the forces and observe different gait patterns. They do this by recording high speed video of runners. Usually, photo reflective stickers or LEDs are fixed to critical points of motion so that the motion of these points relative to each other can be plotted and analyzed. This data can be used to develop algorithms that describe different gaits.

Running gait does not only affect risk of injury, but also efficiency. Kinematic studies have shown that as running speed increases, a runner’s gait changes to accommodate this change in speed. One change in the gait was the foot strike pattern changed from rear foot to forefoot. This motion shortens the gait cycle and increases the step rate. However, when the runners ran at their top speeds for an extended period of time, their mechanics broke down and some of the gait characteristics that increase injury risk became pronounced. Because of this tendency, incremental training with focus on proper mechanics is necessary to reduce injury risk.