J Pathol Transl Med.  2020 Jul;54(4):346-350. 10.4132/jptm.2020.05.14.

Atypical femoral neck fracture after prolonged bisphosphonate therapy

• Kim Kk
• Park Yw
• Kim Th
• Seo Kd

• KMID: 2504566
• DOI: http://doi.org/10.4132/jptm.2020.05.14

Abstract

Of the drugs developed to prevent and treat osteoporosis, bisphosphonate has played a very important role in preventing osteoporotic fractures. However, case reports describing atypical femoral fractures in patients using long-term bisphosphonates have emerged. The majority of atypical femur fractures occurs in the lateral aspect of the subtrochanteric or femur diaphysis, which is explained by accumulation of tensile stress in these areas. Although the superior cortex of the femur neck withstands maximum tensile stress, to our knowledge, there have been only two reports (three cases) of atypical femoral neck fracture. In addition, none of those case reports revealed detailed pathology related to suppressed bone turnover rate. We encountered an incomplete femoral neck fracture and diagnosed it as “atypical” on the basis of the patient’s lack of trauma and medication history and pathological findings. For patients with groin pain, minimal or no trauma, and a history of long-term bisphosphonate use, an atypical femoral neck fracture should be considered.

Keyword

Atypical femur fracture; Femur neck fracture; Tensile strength; Bisphosphonate

Figure

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  Fig. 1. (A) A radiograph performed 3 weeks before referral to our hospital shows a minimal fracture line (white arrow) on the superior cortex of the right femoral neck. (B) A radiograph performed at our hospital at admission shows a more definite and nearly vertical radiolucent line (fracture) in the right femoral neck. (C) T1 magnetic resonance imaging shows a decreased signal intensity in the superior and central aspect of the right femoral neck, which represents bone marrow edema.

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  Fig. 2. (A) Specimen shows a definite incomplete fracture of the superior femoral neck (arrow). (B) A thin fracture line (arrows) extends through the entire thickness of the cortex. (C) A thin fracture gap contained amorphous acellular material (asterisk) but no hematoma, vessels, chondrocytes, or inflammatory cells. However, remodeling cavities with increased cellular activity are seen in the bone adjacent to the fracture gap (arrows). (D) A deep portion of the fracture site is mostly replaced by fibrovascular tissue with a focal area of osteoid formation representing the fracture-healing process (magnification of square area of B).

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  Fig. 3. A giant multinucleated osteoclast with more than 8 nuclei detached from the shallow resorption cavity.

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