Atypical fracture of the femur in a patient with postmenopausal osteoporosis after four injections of zoledronic acid

Bisphosphonates are one of the most effective medications widely used in the treatment of osteoporosis. In the last 15 years, descriptions, and observations of unusual low-energy femoral fractures with atypical localization for osteoporosis after prolonged use of these drugs have been published.

A 78-year-old patient applied to the osteoporosis center. She received parenteral bisphosphonate therapy for severe osteoporosis for 4 years. In 2017, a spontaneous fracture of the middle third of the femoral shaft was registered (the fracture occurred while walking). Regarding the fracture, metal osteosynthesis with a plate was performed. Subsequently, there was a delayed consolidation of the fracture with the formation of a false joint and the need for repeated surgical intervention. Examination of the patient revealed vitamin D deficiency, and significant negative trend in densitometry.

A feature of this case is poor fracture consolidation and long-term uncompensated vitamin D deficiency. Physicians should be aware of this rare but serious complication of bisphosphonate therapy, as it requires discontinuation of antiresorptive drugs and the appointment of bone anabolic therapy for osteoporosis, which, in addition to treating the underlying disease, also promotes consolidation fracture.