Case reports: subtrochanteric femoral stress fractures after prolonged alendronate therapy

Abstract

Background: Alendronate is known for its ability to reduce bone loss in osteoporotic and osseous metastatic conditions. Its long-term effects remain unclear although several reports describe cases of proximal femur stress fractures associated with long-term alendronate use.

Case description: We report the cases of four women who sustained low-energy subtrochanteric or femoral shaft stress fractures while being on alendronate therapy for more than 5 years. All radiographs showed typical patterns consisting of a transverse fracture line with external cortical bone reaction and medial cortical spike. Alendronate discontinuation along with nonoperative treatment was sufficient for one patient, whereas surgical stabilization was required in three patients.

Literature review: The side effects of alendronate therapy include osteonecrosis of the jaw, esophageal irritation, and musculoskeletal pain. Several cases of insufficiency femoral fractures associated with prolonged alendronate use have been reported. Their radiographic pattern and clinical presentation are consistent with our observations. Although various hypotheses have been suggested, the physiopathogenesis of these stress fractures is not completely understood.

Purposes and clinical relevance: Although bisphosphonates play an important role in preventing pathologic fractures in patients with cancer, these subtrochanteric stress fractures associated with prolonged use of alendronate should not be ignored.

Fig. 1A–C

(A) An AP radiograph shows a nondisplaced incomplete fracture of the left femur with an (B) external cortical reaction. (C) An AP radiograph shows the femur after plate fixation of the fracture.

Fig. 2A–F

AP radiographs show (A) right and (B) left femoral shaft cortical reactions. (C) An AP radiograph shows a right femur transverse fracture with medial spike. (D) Right and (E) left AP radiographs show the femurs after intramedullary nailing. (F) Removal of the distal left locking screw led to subsequent healing.

Fig. 3A–E

(A) AP and (B) lateral radiographs show an external cortical shaft reaction without an evident fracture line. The cortical reaction is identified on a (C) MR image and (D) CT scan. (E) An AP radiograph taken 1 year after initial presentation shows a similar image despite clinical improvement.

Fig. 4A–B

(A) An AP radiograph shows a displaced transverse subtrochanteric fracture of the right femur with external cortex thickening and spiking of the medial cortex. (B) Another AP radiograph shows the right femur after intramedullary nailing of the fracture.

Fig. 5

A diagram illustrates the distraction and compression areas in the proximal femoral shaft as suggested by Blaimont et al. [6].