Atraumatic Bilateral Lumbar Pedicle Fractures in a Patient with Back Pain and History of Long- Term Bisphosphonate Therapy: A Case Report

Abstract

of atypical femoral fractures is a known complication of chronic bisphosphonate therapy; however, the finding of atraumatic lumbar pedicle fractures without a prior history of spinal surgery or contralateral spondylolysis is rare. While a few cases of osteoporotic pedicle fractures associated with adjacent vertebral compression fractures have been reported, only a single case of isolated atraumatic bilateral pedicle fractures has been published in a patient who had been on chronic risedronate therapy of 10-year duration. Case Report: The present case report illustrates a 63-year-old man who developed isolated atraumatic bilateral lumbar pedicle fractures after 3 years and 5 months on alendronate treatment. The patient’s past medical history had been significant for osteoporosis with a lumbar spine T-score of -2.7. At the time of initial diagnosis, a comprehensive work-up for secondary causes of osteoporosis proved to be negative; this was followed by initiation of bisphosphonate treatment with 70 mg of alendronate once per week. Ten months after starting bisphosphonate therapy, he underwent magnetic resonance imaging (MRI) of the lumbar spine for low back pain that had not responded to conservative management, with imaging not revealing any evidence of pedicle fractures or pedicle stress reaction. He was again seen in the spine clinic, for atraumatic exacerbation of his chronic low back pain with concurrent right lower extremity radiation, 6 months after stopping bisphosphonate therapy. Since the patient failed to respond to conservative management over the ensuing 6 months, a repeat MRI was obtained, which showed new acute/subacute bilateral L5 pedicle fractures. Conclusion: An isolated atraumatic lumbar pedicle fracture may be an additional type of atypical fracture associated with chronic bisphosphonate therapy in an osteoporotic patient. Key words: Chronic low back pain, bisphosphonate, alendronate, pedicle fracture Pain Medicine