Car Accident Femur Fractures

Thighbone Anatomy From Hip to Knee

The femur, or thighbone, is the longest and strongest bone in the body, and because it is so strong, it usually takes a lot of force to break it. Its long, straight middle section is the femoral shaft, running from below the hip to where the bone begins to widen at the knee, and a break anywhere along that length is called a femoral shaft fracture.

At the top, the head of the femur forms the ball of the hip joint, and the upper femur divides into four areas: the femoral head, the femoral neck just below it, the intertrochanteric area marked by two bony landmarks called the greater and lesser trochanters, and the subtrochanteric area at the upper part of the shaft.

At the bottom, the bone flares out like an upside-down funnel and forms the top part of the knee, the largest weightbearing joint in the body. The quadriceps in the front of the thigh and the hamstrings in the back support that joint and let it bend and straighten. When the lower femur breaks, both muscle groups tend to contract and shorten, so the bone fragments change position and become difficult to line up with a cast.

Dashboard Loading in Frontal Crashes

Motor vehicle accidents are the number one cause of femur fractures. In young people a femoral shaft fracture is frequently due to some type of high-energy accident, and a motor vehicle or motorcycle accident is the most common cause, with being hit by a car while walking, falls from heights, and gunshot wounds among the other common causes.

Among belted drivers of model year 1998 through 2010 vehicles in frontal crashes where the vehicle was towed, the instrument panel or knee bolster was the source of an estimated 87 percent of moderate or more severe upper leg injuries. An estimated 1.5 percent of those drivers had an upper leg injury of that severity from the panel or bolster.

Intrusion changes the odds. For all frontal crashes, the odds of an upper leg injury when the instrument panel or knee bolster intruded were four times the odds without intrusion, rising to eight in full frontal crashes and to 17 in left offset and small overlap impacts. This intrusion occurred in an estimated 3 percent of all vehicles in frontal crashes and was most likely in left offsets, at 8 percent.

Obesity was a risk factor for lower limb injury, especially femoral fracture, and male occupants had a higher proportion of closed knee-thigh-hip fractures than female occupants, a gap tied to height rather than gender. Knee airbags considerably reduced the risk of knee-thigh-hip fractures, at the expense of more lower leg, foot, and ankle fractures.

Early Signs of a Broken Thighbone

A femoral shaft fracture usually causes immediate, severe pain, and the injured person will not be able to put weight on the leg. The leg may look deformed, shorter than the other leg and no longer straight.

Other symptoms are swelling, tenderness, bruising or discoloration, and a bump that is not usually on the leg, along with severe pain in the thigh and leg and not being able to move or use it. A broken femur usually follows a severe injury, and the person will probably know the bone is broken.

With a fracture just above the knee, symptoms are pain with weightbearing, swelling and bruising, pain to touch over the thigh or knee, and a knee that may look out of place on a leg that appears shorter and crooked, with most of these symptoms around the knee. A break near the hip is typically acutely painful in the groin and upper thigh, and the injured leg will often appear shorter than the other and twisted or rotated.

When bone fragments stick out through the skin or a wound reaches down to the broken bone, the fracture is called open or compound, and open fractures often involve much more damage to the surrounding muscles, tendons, and ligaments, have a higher risk for complications, especially infections, and take a longer time to heal.

Patterns Along the Femoral Shaft

Femur fractures vary greatly depending on the force that causes the break. Pieces of bone that line up correctly make a stable fracture, and pieces out of alignment make a displaced fracture. Doctors classify a shaft fracture by its location, with the shaft divided into proximal, middle, and distal thirds, by the pattern of the break, and by whether the skin and muscle over the bone were torn.

Four of the most common shaft patterns are a transverse fracture, a straight horizontal line across the shaft; an oblique fracture, with an angled line across it; a spiral fracture, in which the line encircles the shaft like the stripes on a candy cane and which a twisting force to the thigh causes; and a comminuted fracture, in which the bone has broken into three or more pieces.

Buckle, or impacted, fractures are another pattern, and in a displaced fracture the pieces of bone moved so much that a gap formed around the break.

An accident can land on the shaft itself: an unbelted patient whose airbag deployed was spared head and chest injury but sustained a comminuted fracture in the middle of the femoral shaft.

Breaks Near the Hip and the Knee

Fractures of the thighbone that occur just above the knee joint are called distal femur fractures. In younger patients they are usually caused by high-energy injuries such as motor vehicle accidents, and because of the forceful nature of these fractures, many patients also have other injuries, often of the head, chest, abdomen, pelvis, spine, and other limbs. The break may extend into the knee joint and, in some cases, may shatter the bone into many pieces.

When a fracture extends into the knee joint and separates the surface of the bone into parts, it is called intra-articular, and because it damages the cartilage surface, it can be more difficult to treat. Occasionally the ligaments around the knee can be injured during a femoral shaft fracture as well, as in other knee injuries after a car accident.

At the other end of the bone, a hip fracture is a break in the upper portion of the femur, and while most happen in older adults with bones weakened by osteoporosis, a hip fracture in a younger patient is typically the result of a high-energy event such as a motor vehicle or motorcycle accident. Femoral head fractures account for less than 1% of all hip fractures; they usually result from a high-velocity event and sometimes come with a fracture of the hip socket.

The classical triad of a mid-shaft femoral fracture, a hip injury on the same side, and disruption of the extensor mechanism of the knee appeared in only 5.8% (5 of 82) of restrained occupants with knee injuries rated 2 or higher on the Abbreviated Injury Scale.

Three Thighbone Fractures Compared

The table sets the three regions of the femur side by side: shaft, distal femur, and hip fractures.

X-Rays and Computed Tomography in the Emergency Room

If the injury came from a car accident, it helps the doctor to know how fast the vehicle was going, whether the patient was the driver or a passenger, whether a seat belt was worn, and whether the airbags went off, because that history shows how the injury happened and whether something else may be hurt. The exam looks for an obvious deformity, breaks in the skin, bruises, and bony pieces pushing on the skin, and the doctor feels along the thigh, leg, and foot to check the tightness of the skin and muscles, feel for pulses, and test sensation and movement.

X-rays are the most common way to evaluate a fracture, and they show whether the bone is intact or broken, the type of fracture, and where it is located within the femur. When more information is needed, a CT scan gives a cross-sectional image of the limb that can show the severity of the fracture or, in some cases, detect subtle fracture lines that are very thin and hard to see on an x-ray.

Near the knee, x-rays may also be taken of adjacent bones and joints to look for other injuries, and a CT scan can show whether the fracture enters the joint surface and, if so, how many pieces there are. That scan helps the surgeon decide how to fix the break, and other tests are sometimes done to check the blood supply to the leg.

MRI is rarely needed for a hip fracture, but because it is very sensitive it can sometimes detect a small or incomplete fracture that cannot be seen on an x-ray. X-ray, MRI, and CT scan are the tests providers use to take pictures of the femur and the area around it. A radiologist writes up each study in a report, and an MRI report has its own terminology.

Traction and Timing Before Surgery

Most femur fractures are fixed within 24 to 48 hours, though fixation is sometimes delayed until other life-threatening injuries or unstable medical conditions are stabilized. To reduce the risk of infection, open fractures are treated with antibiotics as soon as the patient arrives at the hospital, and the wound, tissues, and bone are cleaned during surgery.

Between emergency care and surgery, the leg may be placed in a long-leg splint or in traction to keep the broken bones as aligned as possible and maintain the length of the leg. Traction takes two forms: a weighted traction splint, a frame with straps around the ankle, shin, and leg that puts gentle pressure on the femur, and skeletal traction, in which a temporary pin in the femur or shin bone is attached to weights and pulleys outside the body.

An external fixator, metal pins or screws placed in the bone above and below the fracture and attached to a bar outside the skin, is often put on when a patient has multiple injuries and is not yet ready for a longer surgery, and it is usually a temporary treatment for femur fractures that provides good stability until the patient is healthy enough for the final surgery.

Most distal femur fractures are not operated on right away unless the fracture is open, and surgery is typically performed 1 to 3 days after the patient is first seen by a doctor, which gives the surgical team time to plan and prepare the patient.

Intramedullary Nails, Plates, and Screws

Most femoral shaft fractures require surgery to heal, and it is unusual to treat one without it. The method most surgeons currently use is intramedullary nailing: a specially designed metal rod, usually made of titanium, is inserted into the canal of the femur at either the hip or the knee and passes across the fracture, and screws placed above and below the break hold the leg in correct alignment while the bone heals.

Open reduction and internal fixation is the most common surgery for a femur fracture: the surgeon realigns the bone and usually inserts a metal rod through its center, and plates, screws, or wires may be added if the femur is broken into more than two pieces or the fracture is near the hip joint.

Plates and screws attached to the outer surface of the bone are often used when nailing may not be possible, such as for fractures that extend into the hip or knee joints. For a break above the knee in many small pieces, a plate or rod can be fixed at both ends of the fracture without piecing the fragments back together, so that new bone fills in while the overall shape and length stay correct. In extreme cases, a fracture may be too complicated and the bone strength too poor to fix, and the fragments are often removed and replaced with a knee replacement implant.

Near the hip, the options depend on the exact spot: pins, screws, or a plate and screw device for a nondisplaced femoral neck fracture, hip replacement often for a displaced one, a sliding compression hip screw and side plate or an intramedullary nail for intertrochanteric fractures, and a nail with a screw into the femoral head for subtrochanteric fractures.

Most of the time, the rods and plates used to help the bone heal will not need to be removed in a later surgery.

Healing Time and Weightbearing

Most femoral shaft fractures take 3 to 6 months to completely heal, and some take even longer, especially if the fracture was open or broken into several pieces or if the patient uses tobacco products.

Recovery after femur fracture repair most often takes 4 to 6 months, with the length depending on how severe the fracture is, whether there are skin wounds and how severe they are, whether nerves and blood vessels were injured, and what treatment was used. Recovery from surgery usually takes four to six months, and it can take up to a year to recover fully from a broken femur.

A distal femur fracture typically takes 1 year or more to completely heal, and it may take 1 year or more of rehabilitation before a return to all everyday activities. These injuries frequently require a period with no weight on the leg, and it may take 3 months or more of healing before weightbearing can be done safely.

For shaft fractures, doctors in most cases allow as much weight as possible on the leg right after surgery, though full weight may have to wait until the fracture has started to heal. Walking usually starts with crutches or a walker, and because muscle strength in the injured area is most likely lost, physical therapy works to restore strength, joint motion, and flexibility.

In adults with femoral shaft fractures in Malawi, 26 of 37 patients treated with an intramedullary nail had returned to work at 6 months, and average quality of life scores across the study were lower at 1 year than at baseline. These scores also did not return to the pre-injury level after surgery for femoral shaft fractures.

In 50 patients with femoral shaft fractures treated with unreamed intramedullary nailing, the overall healing rate was 93.6 percent, with an average healing time of 19.36 weeks, and there were three nonunions, one delayed union, and one rotational malunion. The knee extensor muscles in the thigh were significantly weaker afterward, which is the strength that physical therapy works to rebuild.

Fat Embolism and Blood Clots

In fat embolism syndrome, particles of fat get into the bloodstream and block blood flow, and the blockages can affect the brain, lungs, skin, and other areas. Fat emboli form any time a bone breaks but are usually too small to cause blockages, and about 95% of cases involve fractures of the pelvis or long bones, especially the femur, tibia, and fibula.

With an isolated break of a long bone like the femur, the syndrome happens in between 0.5% and 2% of cases, and in between 5% and 10% when multiple bones are broken, especially in the pelvis. It usually happens within 2 to 3 days after a major bone break but can happen as soon as 12 hours after the injury. Trouble breathing usually develops before other symptoms, and the other main symptoms are changes in mental state, such as confusion, and a rash of small bruise-like spots that usually appear on the head, neck, chest, and arms.

Most people with the condition recover fully, though it is deadly in between 5% and 20% of cases, with the death rate trending downward largely because of preventive measures and better in-hospital monitoring for those at greatest risk. Fat embolism is among the complications of femur surgery, and it can also happen from the fracture itself without surgery.

Blood clots are the other early concern. Blood clots are among the complications of surgery, and doctors may give blood thinners because clots may develop in the leg veins after surgery. Discharge instructions tell patients to contact the surgeon for shortness of breath or chest pain when breathing, swelling in one leg that is red and warmer than the other, or pain in the calf.

Malrotation and Leg Length Changes

Because intramedullary nailing is usually performed as a closed procedure, malalignment can frequently occur, and the resulting deformity may include improper length, malrotation, and angular malalignment. Malrotation is the most frequent of these, reported in a range of 2.3% to 35%, and it is very difficult to detect both on x-rays and in a clinical exam.

A rotational difference under 10 degrees is widely considered normal, while more than 30 degrees is a deformity that requires correction. Complaints can involve the hip, the knee, or below the knee, and patients with malrotation reported anterior knee pain, especially when climbing stairs and doing sports. Patients often compensate for the twist while standing and walking, which may decrease the symptoms.

A leg length difference of less than 10 mm is often well tolerated, while a difference of 10 mm or more creates an asymmetry that may cause lower back pain, hip pain, and other problems. Poorly healed fractures are among the acquired causes of unequal legs, and the imbalance places stress on the lower back, hip, knee, and ankle, which can lead to premature joint degeneration.

Nonunion, Infection, and Knee Stiffness

Delayed union, when the bone heals slower than usual, and nonunion, when it does not heal at all, are among the complications of femur surgery, along with infection, injury to nerves and blood vessels, malalignment, and hardware irritation, in which the ends of the nail or its screws irritate the overlying muscles and tendons.

Above the knee, open fractures and high-energy fractures are most at risk of not healing, and a follow-up x-ray showing rods, plates, and screws breaking or pulling out of the bone may be a sign that the bone is not healing. To help the fracture heal, a bone graft and changes to the fixation may be suggested.

Less than 5% of patients currently get infections after distal femur fractures, although open fractures and high-energy fractures, such as those from a motor vehicle accident, carry a higher risk. In an open shaft fracture, the bone can become infected even with good surgical cleaning, and bone infection is difficult to treat and often requires multiple surgeries and long-term antibiotics.

Some knee stiffness is expected after a distal femur fracture, and moving the knee soon after surgery is the best way to prevent it. Fractures that enter the knee joint may heal with a defect in the joint surface that can damage cartilage and, over time, result in posttraumatic arthritis, and in severe cases that limit activity a total knee replacement may be the best option.

Measurements and Discharge Records

Regular x-rays monitor how well a fracture is healing and whether it is lined up, with weightbearing starting once the doctor determines the fracture is stable enough. At later visits, doctors assess pain level, leg strength, knee motion, and how well daily activities are going.

Leg length discrepancy is measured on physical examination with the block method and with standing, full-length x-rays, and a CT scan with cuts at the femoral neck and the knee is the most commonly used and accepted exam for malrotation.

Instructions after femur repair cover daily checks of the incision for redness, drainage, or opening, weightbearing limits set by the surgeon or physical therapist, and telling every provider, including a dentist, about a rod or pin in the leg.