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December 20, 2011

Collateral Damage

Rounding Up the Usual Suspects: Fractures

by Corey Dawkins and Ben Lindbergh

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In this installment, it’s back to the basics as we look at how fractures heal. Baseball players suffer their fair share of fractures. Clavicles, fingers, toes, hands, feet, tibias, fibulas, forearm bones, wrists, and sometimes the humerus—hey, it’s not funny when it’s broken—are among those most commonly injured. They all heal through the same mechanisms, although some take longer than others.

Functions of bone/skeletal system
Bone is a living tissue that has six major functions: support, movement, protection, blood cell production, storage, and endocrine regulation. We’re all familiar with the support and protection functions, and when we think about it, movement makes sense too. Unless you’re a worm, muscles need something to pull on to produce the force required for motion. Without bone marrow, blood cells would not be made. Bone cells secrete the hormone osteocalcin, which helps regulate blood sugars and fat deposits, and they also store calcium and ferritin, which are involved in calcium metabolism and iron metabolism, respectively.

Anatomy of bone/Types of bone
There are five main types of bone: long bones (forearm, thigh, and lower leg), short bones (wrist and ankle), flat bones (skull), irregular bones (spine or hip), and sesamoid bones (patella or sesamoids in feet). We can see the different parts of a long bone in the picture below. The periosteum is the outside covering of the bone and is the tissue to which the tendons and ligaments anchor. Underneath the periosteum is the compact bone layer that really gives the bone its strength and resistance to bending.Spongy bone lies at the end of the long bones and provides the greatest amount of elastic strength, in large part because it is subjected to the greatest compressive forces. The compact bone forms a tube in which the yellow marrow resides and functions as fat storage in adults. In the spaces between the spongy bone, red blood cells are produced.



Bone is constantly changing as old bone is replaced by new, healthier bone. New bone is created by osteoblasts, while old bone is destroyed and reabsorbed by osteoclasts. The process involves the osteoclasts breaking down portions of bone that can be up to a millimeter in width and a couple millimeters in length. After the osteoclasts are finished, the osteoblasts come back in and fill in the area. The process is complete once the new bone reaches the surface of the blood vessels in the area. This activity is continuous, and most adult bodies strike a balance between breaking down bone and creating new bone until around age 40, after which the osteoblasts slow down.

Source 1 NSBRI.org

Types of fractures/Mechanism of injury
Even the strongest steel has some give to it before it fractures and fails. Bones acts the same way: they can take a certain amount of stress or strain before they fail and fractures occur. Think about how many times you have tripped or fallen down in your life without suffering a fracture. In those cases, the bones and the soft tissue were able to absorb all of the force of the falls without reaching the structural failure level of the bone. When the stresses go beyond this tipping point, fractures can occur.

People may get caught up in wondering whether an injury is a “fracture” or a “break,” but in reality, those terms refer to the same thing. There are many different types of classification systems for fractures, including historical references to the doctors who first officially recognized a particular type. After a while, everyone developed their own opinions about what classification system should be used, and the system got out of control. There has been a move toward consistent classification of fractures using a standardized system, especially in today’s database-intensive healthcare system.

Official fracture classification depends on several variables, including which bone is injured, the location of the fracture(s) in the bone, and the type, group, and subgroup. There are a million—okay, maybe not quite that many, but close—different fractures, given all the different combinations of bones, locations, types, group, and subgroups. The first part of the equation is easy enough, but things gets tricky after that. To summarize briefly, a fracture can either be closed (no skin breakthrough) or open (through the skin) and can be simple or have multiple fragments.

Simple fractures occur when there is a complete circumferential disruption of the diaphysis or metaphysis or through one articular surface. These simple fractures are the ones we typically think of, involving a gap in the middle of two pieces of the bone. These can be transverse (straight across), spiral, or oblique in orientation.

Multi-fragmented fractures are—as you probably guessed—fractures that have at least one fragment that separates from the rest of the bones. These fractures often need surgical repair and can be further grouped as wedge or complex. Comminuted fractures are included in this group.

Stress fractures are not traumatic fractures, but they can lead to that. In stress fractures, the osteoclast activity is much higher than the osteoblast activity. This can be the result of many things but most often includes an element of repetition and over-training. Nutrition also plays a significant role. If the osteoclasts dig enough tunnels that the osteoblasts don’t fill in, the bone becomes weakened and prone to complete fracture. The sites in which we most often see this in baseball players are the elbow, lumbar spine, shin, and foot.

Symptoms
Just because a bone is fractured does not mean you cannot use that particular body part. Many athletes have suffered a small fracture to their wrist, hand, or even ankle without knowing that it was fractured. The bone tissue itself doesn’t have pain receptors, but the periosteum covering the compact and spongy bones do. That’s why breaking a bone usually hurts, but it isn’t always painful enough that a player knows something is wrong. Muscles also go into spasm in order to try and protect the damaged body part from further injury. Certain fractures are much more serious and need to be medically evaluated and stabilized immediately, such as those to the spine, head, or femur, and any open fracture.

Most fractures are diagnosed through x-rays, but if the x-ray results aren’t clear, then a CT or MRI may be ordered. In cases where stress fractures are a concern, a bone scan may also be used.

Healing process
Now to the nitty gritty, i.e the healing process. Don’t worry, we’re not going to bore you to death and bring you back to high school biology/anatomy class, but there are at least a few things you need to know before we move on. With fractures, bleeding and swelling occurs, just like any other musculoskeletal injury. Sometimes it’s not severe, but at times, there can be a significant amount of swelling and bruising. Immediately after the injury, as the swelling and bruising begins, the body starts to form a clot called a hematoma made of blood and fibrous tissue around the fracture site to limit the damage. Some areas are better than others—certain wrist fractures are notoriously slow healers—but there is always some sort of response.

Within a few days, the periosteum cells begin to replicate and form both chondroblasts and osteoblasts. The cells on one side of the fracture gap build cartilage through the chondroblasts, while the other side of the fracture gap begins to create new bone tissue through the osteoblasts. These two areas continue to grow until they run into each other and begin forming a new heterogeneous tissue called the fracture callus.

The new cartilage and new bone tissue callus gradually transform into lamellar bone, which is trabecular bone and close to the strength of the original material. This usually occurs after the proverbial “four to six weeks” you will hear about in injury reports, or more, depending on the fracture. Once the lamellar bone forms in enough quantity and the bone is in good alignment, it is safe for the athlete to return to play.

Over a period of several years, this new trabecular bone is gradually transformed into the same compact bone that was originally there. This is done by the same osteoclast/osteoblast mechanism by which normal healthy bone replenishes itself.

Immediate Treatment of Fractures
Fracture treatment is fairly standardized but depends some extent on the exact fracture. Initially, there is a period of rest from the offending activity. Occasionally, a functional brace cast be used, but often a cast of plaster or fiberglass material is required. It is important that the cast remains snug so as not to allow any movement and increase the damage or delay healing.

If the fracture is severe enough, it will be repaired surgically. Fractures can be treated by the open reduction, internal fixation method. This method involves realigning the bones through an incision while the patient is under anesthesia and then stabilizing them with screws, plates, nails, or some other hardware. This allows near optimal realignment, and some hardware never needs to be removed.

The alternative method to surgically stabilizing a fracture is external fixation. While the patient is under anesthesia, the bones are realigned, but pins or screws are attached from the bone through the skin to metal bars outside of the skin. The bars represent a frame that is completely stable or sometimes very slowly lengthens over a long period of time. A halo brace for treatment of neck fractures is an example of an external fixation device.

Other fracture treatment
There has been some controversy over the use of bone stimulators, but many physicians swear by it, especially as technology advances and permits use on an increasing number of fracture types. There are two main types of bone stimulators: electrical and ultrasound. Electrical bone stimulators use either a constant microcurrent or a pulsed current that promotes growth factors in the area and thus increases the activity of the osteoblasts and other bone-building tissue.

Ultrasound bone stimulators utilize low-intensity ultrasound, which theoretically provides the same overall benefit of decreased healing time. There is still some debate about whether this has a positive effect on fracture healing, and many peer-reviewed journals have called for larger trials before a definitive answer can be given. Personal anecdotal evidence certainly points to its effective use in treatment of several different fresh fractures, non-union fractures, and stress fractures.

Fracture Prevention
We’ve all heard it before: make sure to drink your milk. There’s truth to that. Calcium is vital for the strength and integrity of bones and needs to be maximized before the mid-twenties when calcium levels in bone slowly start to decline. Regular exercise is also important, although too much is a bad thing. A couch potato is more prone to fractures in the short term, but we wouldn’t want him or her to try to run a marathon in two weeks without any prior training.

Lastly, there is the issue of padding and bracing. A large majority of hand fractures in baseball are the result of getting hit by a pitch. This batting glove by All-Star Sports utilizes D30 technology—that’s the number zero—to provide flexibility to a batting glove that hardens instantly when a quick force is applied. Something like this could be extremely helpful in decreasing the likelihood of fractures.

Long-Term Recovery of Fractures
In the long term, the prognosis for most fractures, when treated properly initially, is exceptionally good. There are a few types of fractures, especially in the hip, wrist, and spine, which can jeopardize the blood supply of the fragment and lead to bone dying even with proper care. Those are few and far between, however, and most of the time, athletes return to their sports without any long-term consequences, Kendrys Morales notwithstanding. The risk of repeating a fracture is pretty low once the new bone has been formed, and especially once it remodels.

Summary
Fractures make up a significant share of baseball injuries, but there are ways to decrease their likelihood, as well as their recovery time. Even with the best plan in place, a medical staff can’t predict when a player will jump and land the wrong way on home plate, but as even newer technology arrives, a large majority of fractures may prove preventable.

Corey Dawkins is an author of Baseball Prospectus. 
Click here to see Corey's other articles. You can contact Corey by clicking here
Ben Lindbergh is an author of Baseball Prospectus. 
Click here to see Ben's other articles. You can contact Ben by clicking here

Related Content:  The Process,  Fractured Ankle

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