Atypical femoral fracture
Updates to Article Attributes
Bisphosphonate-related proximal femoral fractures are an example of insufficiency fractures, although the direct causative link remains somewhat controversial 2.
The atypical fracture pattern occurs in the proximal third of the femur, typically subtrochanteric, and may be unilateral or bilateral. Atypical femoral fractures can also occur more inferiorly to the level of the supracondylar region 1, 2, 3, 4, 6.
An atypical femoral fracture is a diagnosis of exclusion 6:
- not be spiral or comminuted
- not be femoral neck or intertrochanteric
- no evidence of malignant bone tumour (primary or metastatic)
- not be periprosthetic
Epidemiology
The rate of this fracture as pattern outlined above in women who are treated continuously with bisphosphonates is 1 in 1000 compared to 0.2.02 in 1000 for untreated women 1. They occur in older, postmenopausal women 1.
Overall, the risk for all types (i.e. both typical and atypical) of femoral fractures is lower in women who take bisphosphonates 5, 6.
Clinical presentation
Most patients have been on long-term bisphosphonate therapy (> 3-5 years) and report a weeks-to-months history of thigh or groin pain 1, 2, 5, 6. Fractures can be atraumatic or result from a low-energy mechanism (e.g. fall from standing height) 1, 4, 5. They are often bilateral; if the patient has contralateral pain, the opposite femur should also be imaged.
Pathology
A direct link between bisphosphonate use and atypical femoral fractures has not been unquestionably proven due to a lack of high-quality data 2, 5.
The theory that has been proposed is prolonged bisphosphonate use suppresses bone remodelling, leading to microdamage that would normally be repaired but is inhibited, thus increasing skeletal fragility 2, 3, 4.
Radiographic features
Plain radiograph
- changes first occur within the lateral cortex of the proximal femur with cortical thickening and other changes of insufficiency fractures 1,2,6
- incomplete fractures affect the lateral cortex only 6
- complete fractures are typically transverse, sometimes oblique (<30 degrees), and can have a 'beaked' appearance of one cortex 3,4,6
Nuclear medicine
- increased osteoblastic activity (i.e. uptake) in the lateral proximal femur on Tc-99m bone scan 1
MRI
Early changes will follow the pattern of insufficiency fractures with the lateral periosteum and cortex being initially affected 6.
Fractures have the following pattern 6:
- T1: low signal fracture line; diffuse low marrow signal
- T2 and STIR: low signal fracture line; diffuse high marrow signal
Treatment and prognosis
There is no consensus on treatment (conservative vs operative) and the length for which bisphosphonates should be prescribed 2,3.
Delayed fracture healing occurs in ~25% of cases 4. Healing of atypical fractures and restoration of bone quality can be aided by teriparatide, a recombinant human parathyroid hormone (rhPTH) 7,8.
Related pathology
-</ul><h4>Epidemiology</h4><p>The rate of this fracture as pattern outlined above in women who are treated continuously with bisphosphonates is 1 in 1000 compared to 0.2 in 1000 for untreated women <sup>1</sup>. They occur in older, postmenopausal women <sup>1</sup>.</p><p>Overall, the risk for all types (i.e. both typical and atypical) of femoral fractures is lower in women who take bisphosphonates <sup>5, 6</sup>.</p><h4>Clinical presentation</h4><p>Most patients have been on long-term bisphosphonate therapy (> 3-5 years) and report a weeks-to-months history of thigh or groin pain <sup>1, 2, 5, 6</sup>. Fractures can be atraumatic or result from a low-energy mechanism (e.g. fall from standing height) <sup>1, 4, 5</sup>. They are often bilateral; if the patient has contralateral pain, the opposite femur should also be imaged.</p><h4>Pathology</h4><p>A direct link between bisphosphonate use and atypical femoral fractures has not been unquestionably proven due to a lack of high-quality data <sup>2, 5</sup>.</p><p>The theory that has been proposed is prolonged bisphosphonate use suppresses bone remodelling, leading to microdamage that would normally be repaired but is inhibited, thus increasing skeletal fragility <sup>2, 3, 4</sup>.</p><h4>Radiographic features</h4><h5>Plain radiograph</h5><ul>- +</ul><h4>Epidemiology</h4><p>The rate of this fracture as pattern outlined above in women who are treated continuously with bisphosphonates is 1 in 1000 compared to 0.02 in 1000 for untreated women <sup>1</sup>. They occur in older, postmenopausal women <sup>1</sup>.</p><p>Overall, the risk for all types (i.e. both typical and atypical) of femoral fractures is lower in women who take bisphosphonates <sup>5, 6</sup>.</p><h4>Clinical presentation</h4><p>Most patients have been on long-term bisphosphonate therapy (> 3-5 years) and report a weeks-to-months history of thigh or groin pain <sup>1, 2, 5, 6</sup>. Fractures can be atraumatic or result from a low-energy mechanism (e.g. fall from standing height) <sup>1, 4, 5</sup>. They are often bilateral; if the patient has contralateral pain, the opposite femur should also be imaged.</p><h4>Pathology</h4><p>A direct link between bisphosphonate use and atypical femoral fractures has not been unquestionably proven due to a lack of high-quality data <sup>2, 5</sup>.</p><p>The theory that has been proposed is prolonged bisphosphonate use suppresses bone remodelling, leading to microdamage that would normally be repaired but is inhibited, thus increasing skeletal fragility <sup>2, 3, 4</sup>.</p><h4>Radiographic features</h4><h5>Plain radiograph</h5><ul>
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