Fractures of the Femoral Shaft and Distal Femur
Fractures of the femoral shaft are often the result of high energy trauma such as a motor vehicle crash, a fall from a height, or a gunshot wound. Most femoral shaft fractures require surgical treatment. Fractures in the diaphysis (i.e., the mid shaft) are typically treated with the insertion of a metal rod (also known as an intramedullary nail) into the canal of the femur. Fractures located closer to the hip or knee, whose angulation might disrupt joint mechanics and function, require more precise restoration of anatomical alignment that can be offered by an intramedullary nail. Such fractures are therefore usually treated with a surgical plate. The outcomes after femur fractures are usually good, but can be marred by blood loss, infection, delayed union, non-union, mal-union, or problems from associated injuries. Rarely but consequentially, fat from the medullary canal, exposed by the fracture, can travel through the vascular system to the lungs. This can produce a so-called fat embolism syndrome, a serious condition characterized by pulmonary dysfunction and mental status changes related to the resultant hypoxia.
Structure and Function
The femur is the largest bone in the body. Proximally, the femoral head articulates with the acetabulum of the pelvis in the ball-in-socket hip joint. Distal to the hip, the shaft courses toward the knee. Just above the knee joint, the femur widens to form the medial and lateral condyles, whose cartilage-lined surfaces allow articulation with the proximal tibia and patella (Figure 1).
Muscular Anatomy and Deforming Forces
The femur is surrounded by a thick layer of muscles on all sides. Grossly, the muscles around the femur form groups. The forces produced by these muscles can deform a fractured femur in characteristic patterns.
The anterior compartment of the thigh contains the quadriceps femoris muscles. The muscles of the quadriceps (with one small exception, noted below) originate from the shaft of the femur and insert on the proximal tibia via the patella tendon. The four muscles of the quadriceps, the vastus medialis, vastus intermedius, vastus lateralis, and rectus femoris, extend the knee. The rectus femoris, however also can flex the hip, owing to its “long head” which originates from the anterior inferior iliac spine and crosses the hip joint. In general, axial pull from the quadriceps after fracture tends to shorten the leg. The sartorius also lies in the anterior compartment, but is relatively weak and has only a scant impact on fracture deformity.
The posterior compartment of the thigh contains the hamstrings muscles: the short and long heads of the biceps femoris laterally, and semimembranosis and semitendinosis medially. These posterior compartment muscles originate on the pelvis and proximal femoral shaft and insert distal to the knee on the proximal tibia and head of the fibula. Following a fracture, these muscles also cause shortening of the femur.
The medial compartment of the thigh contains the adductor brevis, adductor longus, and adductor magnus, along with the grascilis. All of these muscles originate on the pelvis; the adductors insert along the medial femur and the gracilis inserts on the medial tibia just past the knee. These muscles primarily shorten the leg after fracture but also can introduce a varus (bowing) deformity of a fracture.
The hip abductors, the hip flexors and the short external rotators are muscle groups that originate from the pelvis and insert proximally on the femur. The hip abductors insert on the greater trochanter, the hip flexors insert on the lesser trochanter, and the short external rotators insert on the intertrochanteric ridge of the femur. These muscles, as their name implies, can abduct, flex, or externally rotate the proximal fragment after femur fracture, respectively.
Finally, the two heads of the gastrocnemius muscle of the posterior calf are also attached to the posterior femur, just proximal to the medial and lateral condyles. Following a fracture of the femoral shaft, these two muscle heads can hyperextend the distal fracture fragment creating an anterior angulation deformity.
Femoral fractures are seen primarily in younger or older patients, with the middle-aged population relatively spared. Young patients tend to sustain femoral shaft fractures because of their participation in riskier activities. Their fractures are usually from high energy trauma, such as motor vehicle accidents, falls from extreme heights, or gunshot wounds.
Femoral fractures in the elderly are typically caused by falls. Most commonly, low energy falls in the elderly cause hip fractures, however, the subtrochanteric region of the femoral shaft or the distal femoral metaphysis can be fractured as well. Geriatric femoral fractures are potentiated by conditions causing bone fragility, more frequent falls, or a decreased capacity to catch oneself after a fall and minimize the energy applied to the bone.
Young Patient, High Energy Trauma
This patient is most commonly a young male who has sustained severe trauma. This patient will have severe pain in their leg with shortening of the extremity.
About 10% of femur fractures are seen in companion with other fractures or with severe visceral injury. Patients with polytrauma can have a systemic inflammatory response which can lead to possible multi-organ failure.
Physicians must make all efforts to detect additional injuries at the time of presentation and to prevent complications associated with these injuries. Special attention should also be paid to the spine and pelvis in this group.
Frail Elderly Patient, Low Energy or Absent Trauma
This patient is most commonly an elderly female who fell from standing or had a sudden pain without overt trauma. Elderly patients with a fracture may have cognitive dysfunction from a pre-existing dementia or from acute delirium brought on by pain, dehydration, and adverse effects of medications, among other causes. These patients thus cannot articulate a detailed history of injury.
Elderly patients should be assessed for concomitant fragility fractures such as those of the thoracolumbar spine, proximal humerus, and distal radius. Providers should have a high index of suspicion for associated non-musculoskeletal diagnoses, such as subdural hemorrhage and myocardial infarction.
In the diagnosis of femur fractures below the lesser trochanter, x-ray evaluation is sensitive and specific, and the fracture is usually obvious (Figure 2).
In addition to shaft fractures, the femur may be broken more distally. These fractures can extend into the knee joint (see Figure 3).
There are, however, some specific types of fractures which may need additional imaging to be fully characterized. These include femoral neck fractures associated with femoral shaft fractures, and fractures of the distal femur potentially involving the knee joint.
An ipsilateral fracture of the femoral neck (Figure 4) is seen in association with ~10% of femoral shaft fractures, many of which (20% to 50%) are initially missed! In the setting of a femoral shaft fracture, the femoral neck should be evaluated for concomitant fracture. In the case of equivocal x-ray evaluation, the addition of internal rotation and lateral views or a fine cut CT through the femoral head and neck has been shown to significantly reduce the chance of missing this second fracture. Early diagnosis is critical as it may prevent a relatively easily-fixed minimally or non-displaced fracture (amenable to pinning) from becoming a displaced fracture at high risk of avascular necrosis (and requiring a hip arthroplasty).
A Hoffa Fracture (Figure 5) is a fracture of the posterior aspect of the medial or lateral femoral condyle that needs to be considered in the setting of distal femoral fractures. The fracture lies in the coronal plane and may be difficult to detect on plain x-rays alone. Cross-sectional imaging with CT should therefore be considered in the assessment of distal femur fractures.
Fractures of the femoral shaft and distal femur comprise less than 1% of all fractures. As noted, the incidence of femur fractures demonstrates a bimodal age distribution.
Globally, the annual incidence of femoral fracture is between 15 and 45 per 100,000 population with the risk in low- and middle-income countries almost double that of wealthier countries, owing to poverty, poor road safety standards and more frequent violence.
Below the hip, femoral shaft fractures are five times as common as distal femur fractures and 2.5 times more common than subtrochanteric femur fractures.
Femur fractures are rarely subtle: patients present with a clear history of injury, obvious deformity, pain, and inability to bear weight on the injured limb. Nonetheless, there are important differential diagnosis considerations, emphasizing two questions: Why did the femur fracture? and Are there other, concurrent diagnoses present?
Malignancy may initially present as subacute hip, thigh, or knee pain. Pain with no preceding trauma and x-rays showing changes in bone appearance warrant further investigation, as metastatic disease is the most common bone tumor of the femur. (See chapter, Metastatic Bone Disease and Pathological Fractures)
Pain around the femoral component of a total hip replacement can be from a peri-prosthetic fracture or from septic or aseptic loosening and stress fractures.
A high energy femoral shaft fracture should be a red flag alerting to the possible presence of an ipsilateral femoral neck fracture.
Pain in the thigh region, especially pain that is severe, worsening, and associated with bearing weight is a red flag for stress fracture or malignancy.
Respiratory distress (especially with a petechial rash and mental status changes) after a femur fracture is a red flag for “fat embolism syndrome.”
Treatment Options and Outcomes
Patients with high energy trauma causing a femur fracture should have the injured leg immobilized expeditiously. Placing the extremity in traction may assist resuscitation, by decreasing the volume of the thigh and slowing blood loss from the fracture. Traction also assists in pain control by providing counter tension to thigh muscles that might be in spasm and by limiting the movement of the fractured bone fragments.
Early stabilization of the fracture and restoration of functional movement are essential. Rapid treatment is particularly critical in the frail elderly patient, for whom any extended period of bed rest is poorly tolerated and may be fatal. Muscle wasting and deconditioning occur rapidly with bed rest and their effects are very difficult to reverse. Pressure injuries over the bony prominences of the sacrum and heels can occur within hours, as can deep vein thromboses with subsequent pulmonary emboli. Opiate pain medications used while awaiting surgery can lead to delirium and should be kept to a minimum. Care must be taken to manage chest secretions to avoid pneumonia.
In many low-income countries, access to advanced orthopaedic care is limited and non-operative management of femoral fractures is common. Traction is the most common non-operative method used in these circumstances and generally leads to union within ~50 days. Traction can be applied either via bandages wrapped around the foot or leg (skin traction) or through pins inserted percutaneously through the bone of the distal femur of proximal tibia (skeletal traction). As might be expected, there is a high rate of complications (up to 50%) with prolonged treatment with traction, including malunion, non-union, venous thromboembolism, pressure sores and lung infection.
In developed countries, fractures of the femur are generally managed operatively. Non-operative management of femur fractures is usually only reserved for patients for whom surgery is not feasible or desirable, that is, those with a short life expectancy or bed ridden with very low baseline function.
Treatment options include intramedullary nail (IM) fixation (Figure 6) or plate and screw constructs. IM nails are generally mechanically stronger than plates and are usually the first choice for treating shaft fractures, where gross restoration of length and alignment is more essential than perfect anatomical alignment.
Treatment begins with mechanical alignment of the fracture on a trauma operating table before making any incisions (a so-called closed reduction). Once the fracture is reduced, the IM nail is inserted from either the proximal end of the femur (antegrade nailing) or the intracondylar area of the distal femur (retrograde nailing). This maneuver ensures that the soft tissues near the fracture itself are not disturbed. Keeping the soft tissue envelope intact minimizes the risk of infection and promotes healing. Most fractures treated with IM nailing heal uneventfully (Figure 7).
Fractures close to the articular surfaces require rigid anatomical fixation to maintain joint congruency and biomechanical function of the joint. Restoration of joint alignment helps prevent the development of early arthritis. Thus, fractures near the joints often require an open surgical procedure, in which the fracture is directly visualized, reduced and then stabilized with rigid plates and screws (Figure 8). Immediate knee range of motion is usually prescribed after internal fixation to avoid stiffness, though weight bearing may be more limited post-operatively, as plate fixation is usually not as strong as IM nailing.
In some patients, their femur fracture is part of a severe “multi-trauma” requiring intensive resuscitation measures and for whom early prolonged surgical procedures are deemed to be unsafe. The femur fracture is instead initially managed with temporary emergency stabilization with external fixation or traction. This approach is termed “damage control orthopaedics. Most patients with femur fractures however are amenable to “early total care,” namely appropriate resuscitation and early (within 24 hours) definitive management of fractures, with the advantage that it improves pain control and facilitates the care of associated non-skeletal conditions.
Risk Factors and Prevention
The risk of high energy femur fractures can be reduced by primary, secondary and tertiary prevention strategies.
- A primary prevention strategy is one that minimizes the likelihood of events that may lead to fracture: maintenance of the roads and adequate lighting, for example.
- Secondary prevention strategies are those that mitigate physical damage after a possibly injurious event has occurred, e.g., automobile side airbags.
- Tertiary prevention is the provision of optimal care to minimize the chances of complications once an injury has taken place.
Monitoring and treating patients with osteoporosis or osteopenia can reduce the incidence of fragility fractures. The use of bisphosphonate is cost-effective in people whose risk of sustaining a fragility fracture is greater than ~10% over a 5-year period.
Calcium and vitamin D supplementation has been determined to be extremely cost effective in patients with poor bone health. It is estimated that anywhere from 15-50% of a reduction in fragility fracture risk can be achieved with the utilization of these supplements alone in individuals with osteopenia and osteoporosis.
Patients who are taking bisphosphonate medication to treat osteoporosis can be at risk for developing an atypical subtrochanteric hip fracture. The absolute risk of these fractures in patients on bisphosphonates is low, ranging from 3.2 to 50 cases per 100,000 person-years. These atypical fractures have also been observed in patients who have undergone gastric sleeve or gastric bypass procedures and are thought to be due to the resulting nutritional deficiencies following these procedures.
Prior to the introduction of the Thomas splint (Figure 9) in 1916, during the first world war, the mortality from fractures of the femur was about 80%. By 1918 the mortality was reduced to 20%. The splint was originally designed by Hugh Owen Thomas, considered the father of orthopaedic surgery in Britain, but it was not fully appreciated until his nephew, Robert Jones, introduced it for use in the war. Even today, femoral splints remain a critical part of the initial management of femoral fractures.
In many low-income countries, the management of femoral fractures is undertaken by traditional bone setters with no medical training. Traditional bone setters use a variety of handed-down techniques in addition to, or in place of, traction. These techniques, such as tight bandages and skin creams are associated with high complication rates. (See, for example Complications of traditional bone setters treatment of musculoskeletal injuries: experience in a private setting in Warri, South-South Nigeria. Pan Afr Med J. 2018;30:189. Published 2018 Jul 2. doi:10.11604/pamj.2018.30.189.15730)
Femur, Fracture, Trauma, Fragility, Osteoporosis, Long-bone Fracture, Damage Control Orthopaedics, Early Total Care, Fat Embolism Syndrome, Bisphosphonates
Trauma Assessment, Pulmonary Exam, Resuscitation of a traumatized patient.