A broken bone, bone fracture, crack in bone, stress break, are often synonymous terms to refer to a structural break in the integrity of a bone.
Anatomy of Long Bones
For the 206 bones that comprise the adult skeleton, form follows function: The broad flat plates of our shoulder blades are there to anchor some of the different muscle groups that give the shoulder such freedom of movement. The helmet-shaped cranium protects the delicate brain inside. The pelvis is designed for walking upright. And so on.
Despite their variety, bones share a common internal anatomy. The exterior, called the cortex, consists of a dense smooth layer of bone that acts as an extremely hard shell. Beneath the cortex lies cancellous bone, a honeycombed network of intersecting plates and cross-braced struts (called trabeculae) that greatly reinforces the shell against external mechanical forces. Nerve pathways and blood vessels wind their way through the honeycomb, providing sensation and nourishment to the bone tissue. Red marrow, which produces red blood cells, platelets and most white blood cells, is usually found in the cancellous regions of flat bones such as the hip, breastbone and shoulder blades.
From an engineering perspective, the upper arm (humerus), forearm (radius), thigh (femur) and shin (tibia) are hollow, thick-walled tubes that can be used as levers to apply force or as columns to support weight. The shaft of the long bones is called the diaphysis, and the term describes the hard shell that surrounds the central (or medullary) cavity, which is filled with soft, sponge-like bone tissue. Tucked away in the spaces of this spongy tissue is the yellow marrow, which acts as a nursery for stem cells that can evolve into a variety of cell types (bone, muscle, cartilage and others).
Toward the ends of long bones, the diaphysis flares out, and the interior become cancellous. The struts and plates inside this area, known as the metaphysis, help transfer loads from joint surfaces to the exceptionally strong diaphysis. At the actual ends of the long bones, called the epiphysis, cancellous bone provides the structural foundations for the extra-hard cortical bone and cartilage that together comprise the joint surface.
Types of Fractures
For all its strength and durability, the human skeleton is still at risk of fractures – particularly the long bones of the arms and legs. If hit hard enough or forced in the wrong direction, bones can bend, crack, splinter or even snap in two. However, the type of fracture that occurs is often determined as much by an individual’s age and overall health as by circumstance.
Children’s bones, for example, are springy and resilient, and the periosteum (the membrane that envelops bones) is still quite thick. Since the forces acting on a child’s skeleton are defined by its body size and weight, childhood fractures rarely involve severe displacement of bone or injury to soft tissues. Long-bone fractures in children tend to be incomplete – so-called greenstick fractures where one side of the bone is broken, and the other side is simply bent.
By contrast, adult fractures typically tend to result from direct, high-energy impacts that often have an explosive effect on bone and surrounding soft tissues, such as a fall from a height or a car crash. If the broken bone doesn’t pierce the skin, it’s classified as a “closed” fracture. A simple break across a bone is known as a transverse fracture. When a bone is broken, splintered or crushed into several pieces, doctors call it a comminuted fracture. Under certain circumstances, a bone can be twisted apart, causing a spiral fracture. And if a bone is broken and displaced so that it pierces the skin, then it’s considered an open fracture.
With age, bone tissue becomes increasingly brittle and frail – particularly the cancellous bone in the shoulders, wrists, hips, knees and vertebrae. People of advanced age become vulnerable to low-impact, fragility fractures, often as a result of minor falls. Wrist and hip fractures are common and difficult traumas to overcome for seniors. Osteoporosis accelerates the thinning of cancellous bone and increases the risk of low-impact fractures. Also, high-dose or long-term corticosteroid treatment for an array of chronic inflammatory diseases, as well as for some cancers, can also cause cancellous bone to thin and weaken.
Small blood vessels in the bone and surrounding muscle tissues often rupture during a fracture, causing bleeding and swelling at the fracture site (called a fracture hematoma). The bleeding distends the periosteum, which is full of nerve endings, and makes any pressure or movement acutely painful. Blood also leaks into the surrounding tissues and can even travel quite a distance from the fracture site, leading to additional pain and stiffness. The blood eventually works its way to the skin’s surface, where it forms a bruise. And like all bruises, it begins as a deep purple, then slowly changes to shades of green and yellow as the blood is reabsorbed by the body.
Much can be deduced from the circumstances of the injury, patient history and direct observation of signs and symptoms such as:
- inability to move or use an affected limb or joint,
- acute pain caused by movement,
- open wounds, and so on.
Nevertheless, a definitive diagnosis requires X-ray examination to reveal the true nature and extent of the injury and how best to help the body repair the damage.
A fracture requires emergency treatment. Whether a fracture is simple or complex, closed or open, the goal of treatment is to assure reunion of the broken bone, stabilize motion between bone ends and fragments to promote healing, and restore normal length and alignment to affected limbs.
Immediate first aid for a suspected fracture requires immobilizing and supporting the affected limb with a makeshift sling or splint. To limit swelling, the limb should be elevated with pillows to the same level as the heart. Also apply ice to reduce pain and further control swelling. Restrict pain medication to acetaminophen, since anti-inflammatories (ASA, ibuprofen and others) impair blood clotting and could potentially worsen any internal bleeding. Call 911 for emergency medical services to dispatch an ambulance.
Most fractures are closed and can be treated without surgery. If the two bone ends are displaced/separated, then the attending physician can often perform a “closed reduction.” This involves manipulating, from the outside, the two bone ends back together so that they are in their normal position. Patients may need to be anesthetized either with a local (hematoma block/injection or fracture site injection), a regional (epidural), a general with an epidural, or a general anesthetic. In some cases, the doctor uses X-rays to guide the manipulation and a short period of traction using pulleys, ropes and weights may be required to gently pull the bone ends into place.
If all goes well, usually the next step will be a splint or a cast to stabilize the fracture site. However, when X-rays reveal that closed reduction has not been achieved or that the fracture is complicated because of its type or location, the specialized skills of an orthopaedic surgeon are required.
One surgical approach to a difficult closed reduction or a reduction that is inherently unstable is to use external fixation, wherein the surgeon inserts long pins or screws through the skin and bone above and below the fracture. These are then secured on the outside of the skin with a system of clamps, rods and bars to create a frame around the fracture, pulling the bone ends together. Once healing is complete, the device can be removed.
For some types of fractures, the surgeon will perform an “open reduction and internal fixation,” by first cutting through the skin above the injury and then taking advantage of a wide array of surgical hardware to reconstruct and fix the bone in its optimal position for healing. Using special instruments to manipulate the fragments, the surgeon secures the fragments to the main body of bone, usually using some combination of metal wires, pins, screws, rods and metal plates. Stainless steel, titanium rods, and other metal alloys can be inserted into the marrow cavity for structural support; contoured metal plates are fixed to the outside of the bone with screws to clamp together two large bone segments; and other fragments are stitched together with wire or nailed into place.
Most open fractures are associated with car crashes or pedestrian injuries, industrial accidents and falls, and are best treated by a multi-disciplinary trauma team, since a patient will likely have other life-threatening injuries. These types of fractures are clinically the most serious, since they involve an open wound that is frequently contaminated with dirt and debris, which could lead to infection. Additional complications include the extent of injury to soft tissues and blood vessels, and the complexity of the fracture pattern. For some people, blood loss is so great their blood pressure drops dangerously low, leading to systemic shock.
Once vital signs are stabilized, the orthopaedic surgeon will first clean (“debride”) the wound and fractured bone, and repeatedly flush the area with sterile fluid. Then, as the circumstances dictate, he/she will opt either for external or internal fixation. If the wound is small, then it will be closed with sutures. Wounds that are too large to close will eventually require plastic surgery; in the meantime, the wound is cleansed every two to three days in the OR until it has healed sufficiently to receive tissue grafts, usually after a week or so. People are usually provided antibiotics prophylactically following an open fracture.
Bone Heals Itself
Whereas soft tissues depend on fibrous scar tissue to engineer repairs, bone is unique among the body’s tissues for its ability to heal by producing more living bone tissue. If properly stabilized, even bone fragments reattach to the main body of bone. This takes place in three overlapping stages. First comes the inflammatory stage, where immune cells clean up the debris (damaged cells, bone particles, blood clots) from the fracture site. As the inflammatory stage reaches its peak in a day or two, the area around the fracture swells, stiffens, feels hot to the touch, and slight pressure causes acute pain. Over several weeks, the inflammatory process slowly dies down.
New tissue, called callus, begins to form between the bone ends several days after the fracture and then continues to grow for a month or more. Initially, callus contains no calcium and is soft and pliable. This makes the new tissue vulnerable to tearing if the bone ends become displaced, which is why stabilization is so important. After three to six weeks, the callus hardens into calcified tissue and becomes structurally sound.
The third stage, during which specialized cells shape the bone’s surface to return it to its normal contours, can last many months. Callus is gradually replaced with harder, stronger bone, and any danger of a second disunion has usually passed. Bone formation is faster in children than adults. A simple fracture may take four to six weeks to heal for a toddler, whereas a similar injury may take as many months in an adult.
Life With a Cast
Splints are often used first to stabilize a fracture, because their open design allows for tissue swelling during the initial inflammatory stage. A splint can consist of nothing more than a flat board the length of the broken bone that is strapped on with elastic wrap or tape. Health professionals often use “half casts,” molded fiberglass or plaster splints shaped like a “U” that cup the limb without constricting it. These off-the-shelf splints are made in a variety of shapes and sizes, and they have Velcro straps, which make the splints easy to adjust, and to apply and remove.
Traditional casts are made from rolls of plaster or fiberglass strips that harden once they are wet. Fiberglass has the advantage of being more light and durable than plaster, but plaster molds better (an important consideration when positioning and stabilizing a displaced fracture). Plaster also produces fewer painful pressure points on the skin than fiberglass. Before the cast is applied, your injured limb is first dressed with a soft cotton padding to protect your skin from irritation and cushion bony points where the skin is thin.
Depending where the fracture occurs and the muscle/tendon groups that need to be held in place, casts are molded in different lengths. Forearm and wrist fractures are usually stabilized with a short arm cast, from below the elbow to the hand. A long arm cast (from below the shoulder to the hand) is used for upper arm, elbow and forearm fractures, while keeping various muscle and tendon groups properly positioned. A third type, the arm cylinder cast, which is from below the shoulder to the wrist, is used to hold elbow muscles and tendons in place after dislocation or surgery.
Similarly, leg casts come in different lengths. Short leg casts (from below the knee to the toes) are used for fractures of the near the region of the distal tibia or ankle, as well as for severe ankle sprain with ligament tear. The longer version for legs stretches from mid-thigh to the toes and is used for tibia fractures that are close to the knee.
To keep swelling to a minimum, for the first 48 hours, you should ensure your cast remains level with your heart. Also, loosely wrap a large bag of frozen peas or a commercial ice pack around the splint or cast at the level of the injury. Thereafter, elevate your cast at regular intervals according to your doctor’s instructions. Flex your fingers or wriggle your toes often, since this helps pump blood away from your elevated limb and reduces swelling.
A cast should be close-fitting but not feel uncomfortably tight. Report any continuing feelings of pressure or pain or numbness to your doctor promptly, since these symptoms may signal a developing skin ulcer or compartment syndrome (excessive swelling of injured muscles) both of which need quick professional attention.
You and your cast are going to have to get along for at least a couple of months, so here’s some simple advice to keep things trouble-free:
First and foremost, never get your cast’s cotton inner lining wet since the padding can retain moisture and never fully get dry; this in turn can lead to maceration (softening and breakdown of the skin), in which case the cast has to be removed and replaced to avoid possible infection. Commercial waterproof and watertight covers are available; otherwise, try using a large plastic bag and masking tape.
Next, make sure every day to check the skin around the edges of the cast, and apply lotion if there are red or sore spots. If the cast develops some rough edges that could cause chafing or pressure sores, try padding the area with soft, smooth materials such as moleskin or gauze.
Position your cast carefully at night or when you need a rest, wedging and elevating with pillows to prevent the edges from pinching the skin or digging in.
Finally, even though it itches like crazy, resist the temptation to push a sharp or pointed object (pencil, letter opener, etc. ) inside your cast, since – more frequently than you would expect -it can become lodged inside, stabbing you when you move and dropping further into the cast out of reach. That means a trip to the hospital to have the cast removed and replaced. For itchiness, try blowing cool air from a hair dryer down the cast!
After just a few weeks in a long leg cast, the muscle shrinkage from disuse is often so great that most people can insert their hand into what used to be a tight space between the cast and their thigh. The muscles and tendons of joints that are immobilized because of a cast not only lose bulk but also become stiff and unable to completely flex and extend. Consequently, when the cast comes off, most patients begin a course of specific range-of-motion and strengthening exercises under the supervision of a physiotherapist. To fully regain strength in an affected limb, you’ll need to be dedicated and follow a daily exercise regimen.
The older you are, the longer it takes to recover from a fracture. Children heal better and more rapidly, so that often after several years there is no visible trace of a fracture on X-rays. People in their mid-years will also usually mend completely after rehab, although not as quickly as the younger generation. By contrast, people in their seventies and eighties who suffer an immobilizing fracture (such as a fragility fracture of the hip) can face a long and difficult recovery, during which they are dependent on caregivers for basic aspects of everyday life.