Atypical Femoral Stress Fracture Research Articles

Atypical Femoral Stress Fracture with Uncommon Location and Mechanism of Injury: A Case Report

Atypical Femoral Stress Fracture with Uncommon Location and Mechanism of Injury: A Case Report

Focal Increased Tc-99m MDP Uptake in the Nutrient Foramen of the Femoral Diaphysis on Bone SPECT/CT.

We present images of an 83-year-old female with a history of osteoporosis and bilateral total knee replacement arthroplasty, referred for bone scintigraphy and single-photon emission computed tomography (SPECT)/computed tomography (CT), owing to left knee pain. No trauma to, or intense exercise of, the knee was reported. The bone scan and SPECT/CT revealed a focally increased Tc-99m methylene diphosphonate (MDP) uptake in the medial cortex of the left femoral diaphysis with matched linear radiolucency on CT images. This was misinterpreted as atypical femoral stress fracture; however, focal stress reaction injury to the nutrient foramen was confirmed on contrast-enhanced magnetic resonance imaging.

Bone scintigraphy depicts bilateral atypical femoral stress fractures with metachronous presentation, long before a complete fracture occurs.

Atypical femoral fractures (AFF), although rare, are recognized more often during the last decade. They are located in the subtrochanteric region or the femoral shaft, may be bilateral, can evolve to complete fractures after bone overload or minimal trauma and have specific radiological features. The complete fractures have horizontal or slightly oblique configuration accompanied by a medial spike, are non-comminuted, and extend to both cortices. There is also generalized cortical thickening of femoral shaft. Newer evidence suggests that AFF are stress or insufficiency fractures, possibly associated with long-term use of bisphoshonates (BP). AFF can also occur in oncologic patients referred for bone scintigraphy and, in such a case, they should be differentiated from bone metastases. We present here a case with bilateral AFF with metachronous appearance in a female patient with a history of breast cancer and osteoporosis. The first AFF had been depicted on bone scintigraphy 3 years before a complete fracture occurred at this site, but the finding was overlooked. A second bone scan performed shortly after the fracture in order to exclude underlying bone metastases disclosed an additional unsuspected incomplete AFF in the contralateral femur, which was confirmed by radiography. In conclusion, oncologists should consider other causes of bone pain besides bone metastatic disease, and physicians interpreting whole body bone scans of oncologic patients should be aware of the entity of AFF, in order to avoid false positive results and provide early information about an impending complete AFF.

Atypical femoral stress fracture in a woman on alendronate therapy

Atypical femoral stress fracture in a woman on alendronate therapy

Atypical femoral stress fractures in bisphosphonate-free patients

The long-term safety of bisphosphonates has been questioned in case series [1, 2] in which atypical femoral stress fractures has been seen with its prolonged use. Atypical femoral stress fractures have distinctive radiographic characteristics: transverse or short oblique configuration, associated with focal or diffuse cortical thickening, so-called “beaking”. However we identified four patients (five fractures) from our series of 50 patients (8%) who fulfilled these radiographic pattern but who were never put on bisphosphonates. The ages of the cases were 50, 53, 66, 70 and 78 years at time of fracture. Two patients had normal BMD, one patient (with bilateral atypical fractures) was osteopenic, and one patient did not have BMD available. In all these patients, there were no prodromal symptoms, no history of hormonal therapy and their 25-hydroxyvitamin D measurements were normal (range 21.9–26.1 ug/L). They had no history of renal impairment, steroids usage or any endocrinological dysfunction (except one patient who had diabetes mellitus). One patient had breast cancer treated more than 20 years ago. Her procollagen type 1 amino-terminal propeptide level was