Femoral Head Fractures

Fractures of the femoral head are relatively uncommon but often are associated with a poor functional outcome. They are typically seen in the setting of high-velocity trauma that results in a hip dislocation, such as a motor vehicle accident. In a dashboard injury the hip is vulnerable to dislocation due to its flexed and adducted position. The fracture occurs either from impaction or shearing. Reportedly, femoral head fractures occur in 7% to 15% of posterior hip dislocation injuries and as high as 68% of anterior hip dislocations. Associated complications include injuries to the sciatic nerve, AVN of the femoral head, periarticular heterotopic ossification, and secondary osteoarthritis.

Although several classifications exist, the Pipkin classification, which is based on the location of the femoral head fracture and the presence of associated acetabular or femoral neck fractures, is most widely used. A type I fracture involves the femoral head inferior to the fovea capitis, and type II fractures involve the femoral head superior to the fovea capitis. A type III fracture is a type I or II injury associated with a fracture of the femoral neck. A type IV fracture is a type I or II fracture with an associated acetabular fracture ( Fig. 15-1 ). The Pipkin scheme does not differentiate the type of hip dislocation injury. A more comprehensive classification that includes anterior and central hip dislocations has been proposed by Brumback and colleagues. This scheme divides fractures into one of five categories with A and B subsets incorporating the position of the femoral head with respect to the acetabulum ( Fig. 15-2 ).

A, Pipkin classification. Type 1, fracture inferior to the fovea capitis. Type 2, fracture extending superior to fovea capitis. Type 3, any femoral head fracture with concurrent femoral neck fracture. Type 4, any femoral head fracture with concurrent acetabular fracture. B, Coronal computed tomographic (CT) reconstruction of Pipkin I fracture. The fracture does not involve the weight-bearing portion of the femoral head. C, Three-dimensional (3-D) CT reconstruction of the same fracture viewed from an anteroposterior (AP) direction. D, Radiograph of Pipkin II fracture. Note the fracture line (white arrowheads) extends superior to the fovea capitis (red arrow) .

Brumback classification.

Type 1, posterior dislocation with fracture of the inferomedial aspect of the femoral head. 1A, stable hip joint with minimal or no fracture of the acetabular rim. 1B, significant acetabular rim fracture and joint instability. Type 2, posterior dislocation with fracture of the superomedial aspect of the femoral head. A and B subsets are divided the same way as type I on the basis of acetabular involvement and joint stability. Type 3, dislocated hip (in any direction) with a femoral neck fracture. 3A, no femoral head fracture. 3B, with an associated femoral head fracture. Type 4, anterior dislocation with a femoral head fracture. 4A, femoral head fracture is an impaction fracture. 4B, femoral head fracture is a shearing-type fracture. Type 5, central fracture-dislocation with a femoral head fracture.

Radiographically an alteration in the normal contour of the femoral head denotes a femoral head fracture (but this may require computed tomography [CT] for diagnosis). Any fracture that creates a step-off greater than 2mm constitutes a surgical lesion. It is also essential to evaluate for a concurrent femoral neck fracture. Additional observations on CT that may be seen in patients with a femoral head fracture include the presence of intra-articular fragments, congruency of the articular surfaces, and the integrity of the acetabulum.

Femoral Neck Fractures

Femoral neck fractures occur most commonly in older adults. Several theories related to the mechanism of these fractures have been postulated, including direct trauma to bone that is weakened by osteoporosis, rotational forces incurred on the femoral neck at the time of a fall, or the completion of a fatigue fracture that subsequently causes a fall. Femoral neck fractures in patients under 50 years of age are relatively rare and are typically the result of high-energy trauma such as a motor vehicle accident or fall from height. Most femoral neck fractures occur just below the femoral head at the junction of the femoral head and neck (subcapital), although fractures may also occur through the midportion of the femoral neck (transcervical) or at the base of the femoral neck (basicervical). The medial and lateral femoral circumflex arteries supply 75% of the blood to the femoral head by way of the medial and lateral epiphyseal arteries and the inferior metaphyseal artery. Additional blood supply comes from the obturator internus artery and the artery of the ligamentum teres. The circumflex vessels may be disrupted when femoral neck fractures become displaced, resulting in AVN of the femoral head.

Evaluation of a patient suspected of having a hip fracture begins with radiographs. Proper technique is critical to accurately detecting femoral neck fractures. Anteroposterior radiographs of the pelvis should be performed with the hip in internal rotation when possible. Oblique frog-leg or cross-table lateral views are useful for delineating displacement of a fracture. As in pelvis fractures, it is useful to compare symmetry with the contralateral hip. When radiographs are negative or inconclusive for a fracture but there remains high clinical suspicion (i.e., unwillingness to bear weight), then magnetic resonance imaging (MRI) is the modality of choice for further study. The reported sensitivity and specificity of MRI for detection of radiographically occult fractures is nearly 100%, and it also has the added benefit of surveying the surrounding soft tissues for additional injuries.

Subcapital femoral neck fractures may be complete or incomplete. In addition, complete fractures may be impacted or displaced. There are numerous available classification systems for describing subcapital fractures, but the Garden classification, which consists of four stages, is perhaps the most recognizable. A stage I fracture is an incomplete (or occasionally complete) fracture with lateral impaction resulting in a valgus angulation. A type II fracture is a complete nondisplaced fracture that is impacted along the entire length of the fracture. A type III fracture is a complete fracture with partial displacement, usually with varus angulation. A type IV fracture is a completely displaced fracture with displaced fragments caused by proximal migration of the femoral shaft ( Fig. 15-3 ). Subcapital fractures may be extremely subtle, and a combination of a sclerotic line caused by trabecular overlap, cortical buckling or irregularity, and trabecular angulation should suggest this diagnosis.

Garden classification.

A, Garden I, subcapital fracture of the left femoral neck. There is no displacement, but there is impaction laterally, resulting in valgus angulation at the fracture site. B, Garden II, fracture of the left femoral neck. There is a complete fracture with impaction along the entire length of the fracture (black arrowheads) . C, Garden III, fracture with partial displacement and varus angulation at the fracture site. D, Garden IV. There is complete displacement of the fracture with proximal migration of the femoral shaft. The Shenton line is disrupted.

True transcervical femoral neck fractures are rare and are treated in the same way as patients with subcapital fractures. Basicervical fractures occur at the base of the femoral neck at its junction with the trochanters ( Fig. 15-4 ). When a basicervical fracture occurs, the possibility of a completed stress fracture or a pathologic fracture should be considered.

Femoral neck fracture.

Basicervical fracture at the base of the femoral neck near the junction with the trochanters. Note that these fractures mimic intertrochanteric fractures.

There are two types of stress fractures, fatigue and insufficiency. Fatigue stress fractures result from abnormally increased stress placed on normal bone, which occurs frequently in athletes and military recruits. Insufficiency stress fractures are the result of normal stress placed on abnormal bone occurring, for instance, in the settings of osteoporosis, renal osteodystrophy, or chronic steroid use. In the femoral neck, stress fractures may affect the compressive side or the tensile side. The majority of stress fractures are compressive, involving the inferomedial cortex of the femoral neck. Radiographically the appearance of these fractures is a linear area of sclerosis perpendicular to the cortex with or without an associated linear lucency through the cortex. Surrounding endosteal sclerosis and periosteal reaction may be observed as well ( Fig. 15-5 ). Tensile stress fractures typically are insufficiency type of fractures occurring in the superolateral cortex of the femoral neck just inferior to the femoral head. The characteristic radiographic appearance is an ill-defined linear area of sclerosis or simply a break in the cortex ( Fig. 15-6 ). These fractures may progress to a complete subcapital fracture if left untreated.

Compressive side femoral neck stress fracture.

A, Focal linear sclerosis in the inferomedial aspect of the femoral neck denotes a compressive stress fracture. There are associated endosteal and periosteal reactive changes. B, Coronal computed tomographic (CT) reconstruction of the same fracture clearly demonstrates the unicortical nature of the fracture.

Tensile side femoral neck stress fracture.

Incomplete lucent fracture line in the inferolateral aspect of the femoral neck denotes a tensile stress fracture.

Trochanteric and Intertrochanteric Fractures

Intertrochanteric fractures are common in older adults. Isolated trochanteric fractures are less common and can affect people in any age-group. Isolated greater trochanteric fractures are often the result of a fall or direct trauma ( Fig. 15-7 ). They may be difficult to detect radiographically, particularly in osteoporotic or thin patients. The treatment of greater trochanteric fractures is conservative unless the greater trochanter is severely displaced. It is important to characterize the fracture as not part of a more extensive intertrochanteric fracture. If the radiographic findings are equivocal, MRI is recommended to accurately define the extent of the fracture. In skeletally immature patients, avulsion fractures of the greater trochanter may occur owing to sudden forceful contraction of the gluteal muscles on the apophysis. These are treated conservatively if displacement is less than 1 cm and displacement does not increase on sequential follow-up radiographs. Isolated fractures of the lesser trochanter are usually the result of tension by the iliopsoas tendon on the enthesis and characteristically occur in children or adolescent athletes. In skeletally mature people, isolated lesser trochanteric fractures often are pathologic fractures, indicative of an underlying bone neoplasm or metastasis ( Fig. 15-8 ).

Greater trochanteric fracture.

There is soft tissue swelling lateral to the hip (white arrowheads) . Avulsion fracture of the greater trochanter (black arrow) is slightly displaced. This fracture occurred after a fall.

Lesser trochanter fracture.

There is a distracted fracture of the lesser trochanter (arrow) with medial and superior displacement of the fragment caused by an avulsion of the insertion of the iliopsoas. This fracture was a pathologic fracture. Note the permeative appearance of the bone in the intertrochanteric region, as well as periosteal reaction along the lateral cortex (white arrowheads) .

Intertrochanteric fractures extend from the superolateral aspect of the greater trochanter to the inferomedial aspect of the lesser trochanter along the intertrochanteric ridge. Comminution is common, and as many as 50% are considered unstable. The integrity of the calcar femorale, posterior and medial cortices, number of fragments, and displacement determine stability.

There are several classifications available for characterizing intertrochanteric fractures. A common method employed is the Evans classification, which subdivides intertrochanteric fractures into six types ( Fig. 15-9 ). A type I is a simple two-part nondisplaced fracture that parallels the intertrochanteric line. A type II is a two-part fracture that is displaced. Both of these are considered stable. A type III fracture is a three-part fracture with displacement of the greater trochanter, resulting in loss of posterolateral support. A type IV fracture is also a three-part fracture but with displacement of the lesser trochanter, resulting in loss of medial support. Both type III and type IV Evans fractures are considered unstable and difficult to reduce. A type V fracture is a four-part fracture with displacement of both the greater and lesser trochanters. The final type is termed R and denotes a fracture with reversed obliquity, with the fracture line beginning in the lesser trochanter medially and extending inferolaterally to exit below the lesser trochanter. These fractures are inherently unstable due to the unopposed traction of the abductors on the greater trochanter and adductors on the lesser trochanter and femoral shaft. It is noteworthy, however, that these fractures may be nondisplaced at presentation ( Fig. 15-10 ).

Evans classification.

Type I, two-part nondisplaced fracture. Type II, two-part displaced fracture. Type III, three-part fracture with displacement of the greater trochanter. Type IV, three-part fracture with displacement of the lesser trochanter. Type V, four-part fracture with displacement of both the greater and lesser trochanters. Type R, fracture with reversed obliquity. Type I and type II fractures are considered stable.

Intertrochanteric fractures in two different patients.

A, Three-part fracture with displacement of the lesser trochanter (white arrow) results in loss of medial support and instability of the fracture. This would be considered an Evans type IV fracture. B, Reversed obliquity fracture with the fracture line oriented from the superomedial to inferolateral cortex. There is medial displacement of the femoral shaft due to the action of the adductor muscles, and the greater trochanter is displaced superolaterally by unopposed action of the abductor muscles.

Subtrochanteric Fractures

Subtrochanteric fractures occur between the lesser trochanter and the proximal 5 to 7 cm of the femoral shaft and account for about 10% to 34% of all hip fractures. These fractures have a bimodal age distribution. In younger patients they are typically the result of high-energy trauma resulting in comminution and significant soft tissue injuries. In older patients the fractures are often the result of low-energy trauma, and diminished overall bone density is an important contributing factor. Radiographically, fractures in older adults tend to be linear or spiral and only minimally displaced.

Numerous classifications for subtrochanteric fractures have been proposed. The AO classification is a complicated three-part scheme with multiple subtypes often used in research. The Seinsheimer classification consists of eight subgroups based on stability of the medial cortex. The Russell-Taylor classification is useful in determining the mode of fixation required based on involvement of the piriformis fossa. Type I fractures do not involve the piriformis fossa. Type I fractures are subdivided into type IA, which occur below the lesser trochanter, and type IB, which involve the lesser trochanter. Type II fractures involve the piriformis fossa. Type IIA fractures demonstrate a stable medial cortex, and type IIB denotes involvement of the piriformis fossa with lack of stability of the medial femoral cortex. Management is determined by the extent of the fracture, with type I fractures being treated with intramedullary devices whereas type II fractures require open reduction and internal fixation ( Fig. 15-11 ). The Fielding classification divides subtrochanteric fractures into three zones. Zone 1 includes fractures that involve the lesser trochanter, zone 2 occurs 1 to 2 inches distal to the lesser trochanter, and zone 3 occurs 2 to 3 inches distal to the lesser trochanter ( Fig. 15-12 ).

Russell-Taylor classification of subtrochanteric fractures.

Type I fractures do not involve the piriformis fossa, and type II fractures involve the piriformis fossa. A and B subsets are divided on the basis of stability of the medial cortex determined by involvement of the lesser trochanter.

Fielding classification.

This classification divides subtrochanteric fractures on an anatomic basis, describing the position of the fracture in relation to the lesser trochanter.

Hip Dislocation

Hip dislocations are severe injuries caused by high-energy trauma and account for 5% of all joint dislocations. Dislocation of the femoral head is dictated by the position of the lower extremity and hip at time of injury, as well as the vector or direction of force. There are three types—central, posterior and anterior—based on the terminal position of the dislocated femoral head.

Although assessment of hip dislocations begins with radiographs, CT is critical in the management of hip dislocations. Long-term disability may be caused by an injury to the sciatic nerve; AVN, which occurs in up to 17% of hip dislocations; and osteoarthritis. The risk for AVN increases proportionally with the length of time that the hip is dislocated. Osteoarthritis is the most common complication, occurring in 16% of dislocations without associated fractures and up to 80% when there is a concomitant acetabular fracture. Computed tomography is ideal for determining congruency of the joint after reduction, identifying other fractures of the acetabulum or femoral head, and detecting trapped intra-articular fracture fragments. The role for MRI is currently reserved for chronic or persistent pain that may be caused by underlying injuries to the ligamentum teres, acetabular labrum, or articular cartilage.

Central dislocations occur in patients with acetabular fractures that disrupt the quadrilateral plate, produced when a lateral force strikes an adducted femur. In this injury the femoral head displaces medially and the joint space may narrow medially, superiorly, or in both directions. Computed tomography is critical for preoperative planning because the acetabular fracture is often complex. Most surgeons advocate that CT be performed within the first 10 days of the injury for optimal results ( Fig. 15-13 ).

Central hip dislocation.

The fracture of the quadrilateral plate allows medial displacement of the femoral head.

Posterior dislocations account for 80% to 85% of all hip dislocations. The most common mechanism of injury is an anterior-to-posterior force directed to the lower extremity with the hip held in flexion (i.e., a dashboard injury). In this dislocation the femoral head displaces superiorly to the acetabulum and the femur rotates internally ( Fig. 15-14 ). Associated fractures of the posterior wall of the acetabulum are common and should be evaluated with CT because fractures that affect greater than 60% of the articular surface are likely unstable ( Fig. 15-15 ). Fractures of the femoral head are relatively less common and are the result of impaction or a shearing when the femoral head strikes the posterior wall of the acetabulum. Note that posterior dislocations may also occur with fractures of the ipsilateral femoral shaft.

Posterior hip dislocation.

The femoral head projects superior and lateral to the acetabulum. Note that the femur is internally rotated so that the lesser trochanter overlaps the femoral shaft (red arrow) .

Posterior hip dislocation.

A, Axial computed tomography (CT) of posterior hip dislocation with concomitant acetabular fracture. B, Sagittal CT reconstruction of a different patient with a posterior hip dislocation. There is also a comminuted fracture of the acetabulum involving the posterior wall and roof. C, Axial CT image after reduction of left hip dislocation in a third patient. A trapped intra-articular fracture fragment is present in the medial joint space (red arrowhead) , as well as a concomitant fracture of the posterior acetabular rim (white arrow) .

Anterior dislocations account for 10% to 15% of hip dislocation injuries. The dislocation occurs when a posteriorly directed force is applied to the inner aspect of the knee while the hip is abducted and externally rotated. There are two types, obturator and subspinous, and the degree of hip flexion determines the type of dislocation that will occur. An obturator dislocation is more common, with the femoral head displacing inferomedially while the femur abducts and externally rotates ( Fig. 15-16 ). In a subspinous dislocation the femoral head displaces superiorly beneath the spine of the iliac bone, and the femur extends and abducts. The terminal position of the femoral head, which is superior and lateral, may be confused for a posterior dislocation injury. The key to differentiating between these dislocations is the femoral position. In an anterior dislocation the femur is locked in external rotation, and the femur will also be abducted or neutral in position. In a posterior dislocation the femur is adducted and fixed in internal rotation ( Fig. 15-17 ).

Anterior hip dislocation.

A, The femoral head displaces inferomedially beneath the anterior column in the obturator type of dislocation. Note that the femur is abducted and externally rotated. B, Computed tomographic (CT) three-dimensional (3-D) reconstruction in a different patient demonstrating the anterior displacement of the femoral head from the acetabulum. There is a fracture of the femoral head with an intra-articular fragment (black arrow) .

Anterior hip dislocation.

A, In the subspinous type the femoral head superiorly displaces beneath the spine of the iliac bone. The femur is abducted and externally rotated, profiling the lesser trochanter (white arrow) . B and C, Left posterior oblique Judet and cross-fire lateral views confirm anterior dislocation of the femoral head from the acetabulum. D, In a posterior dislocation the femur is adducted and fixed in internal rotation with the lesser trochanter overlying the femoral shaft (black arrow) . (From Fuller M. Radiography of hip dislocations. Applied radiography. Case 1, Figs. 1 to 3. wikiRadiography . 2010.)

Septic Arthritis

Septic arthritis of the hip is more prevalent in children than adults. Adult populations at increased risk include intravenous drug abusers; patients with chronic liver disease or kidney disease, diabetes, or rheumatoid arthritis; and patients requiring long-term corticosteroid use. Patients with joint replacements are also at increased risk.

Radiographically, early findings tend to be relatively nonspecific, but as the infection progresses, the joint space narrows because of destruction of the cartilage. Periarticular osteopenia, marginal erosion, and osteolysis of the cortex are also important observations ( Fig. 15-18 ). Synovial inflammatory arthropathies share some similar findings, but rapidly progressive destructive changes should prompt an expeditious search for an infectious cause. Joint aspiration is useful in confirming the diagnosis and providing critical information regarding the source.

Septic arthritis.

A, Anteroposterior (AP) radiograph of the left hip shows narrowing of the joint space (black arrowheads) , periarticular osteopenia, and osteolysis of the lateral aspect of the femoral head (white arrow) . B, Coronal short tau inversion recovery (STIR) magnetic resonance image (MRI) shows marked edema within the bones on both sides of the joint. Note the erosion on the lateral aspect of the femoral head from bone lysis (red arrow) . There is also a large joint effusion containing proteinaceous debris.