FRI684 So Strong Yet So Fragile: Bilateral Periprosthetic Fractures On Denosumab

Disclosure: A. Syeda: None. F.S. Mirza: None. Background: Denosumab (DN) is a potent antiresorptive and has been associated rarely with atypical femoral fractures. We hereby report the first case of simultaneous bilateral femoral periprosthetic fractures (PPF) while on DN therapy (DNT). Clinical Case: A 78-year-old female with severe osteoporosis on DNT presented in January 2023 with bilateral femoral PPF after a mechanical fall whereby she tripped and landed on her knees. The patient had initially presented to us in late 2012. Treatment history included alendronate (ALN) for 5 years, on drug holiday since 2010. She underwent bilateral knee replacement surgeries in 2012 and DNT was started in 2013 after initial evaluation. She also had primary biliary cirrhosis, and although bone density (BD) improved on DNT, she exhibited escape from DN mediated suppression of bone resorption possibly related to the liver disease that was previously reported (1). DNT was stopped 5 years later when spine BD improved to osteopenic range and ALN 70 mg weekly was started. 1 year later, bone resorption markers were still elevated and zoledronic acid was substituted for ALN. She fell and had a pubic ramus fracture 11 months later. BD showed a 6% decrease for mean total hip and baseline forearm BD showed T-score of -3.7 on the right. DNT was restarted in December 2020 and continued every 6 months. Her health continued to deteriorate over next two years, with increase in LFTS, new anemia and thrombocytopenia due to a combination of myelodysplastic syndrome and splenomegaly. She also needed transcatheter aortic valve replacement for worsening CHF. She tripped and fell in January 2023. X-ray showed acute supracondylar bilateral PPF with comminution. She was high risk for anesthesia and anticoagulation was withheld due to a history of thrombocytopenia and gastrointestinal bleeding. Prior to the anticipated orthopaedic procedure, the patient developed severe hypotension and a rapid drop in hematocrit due to hemorrhagic shock. The family had requested DNR due to the multitude of medical issues. Conclusion: Occasional PPF have been reported in the setting of DNT, which may reflect the severity of osteoporosis. Altered stress distribution and decreased tensile strength of the bone secondary to screw/pin placement are thought to contribute to PPF, although the occurrence of PPF as an unusual presentation of an AFF cannot be excluded. Contribution of other comorbidities to poor bone quality may also have contributed to the bilateral PPF with poor outcome in our patient. 1. Vedere, T.R. and Mirza, F.S., 2017, April. Escape from Denosumab Mediated Suppression of Bone Resorption in Primary Biliary Cirrhosis. In 99th Annual Meeting of the Endocrine Society. Endocrine Society. Presentation: Friday, June 16, 2023