Bone Abstracts

Background and aim: Eight cases of bisphosphonate-associated osteonecrosis of the external auditory canal have been reported in case-reports. Our aim was to describe the incidence of external auditory canal and middle ear diseases in Danish patients exposed to bisphosphonates in the treatment of osteoporosis.

Methods: The study was a retrospective, nationwide cohort study, within the Danish population of approximately 5.6 million individuals and based on Danish national registers.

From 2003–2010, 131 794 patients had bisphosphonates prescribed for treatment of osteoporosis. These cases were matched 3:1 for age and gender with a total of 395 382 persons unexposed to bisphosphonates. Primary outcome was disease in the external auditory canal and middle ear, defined as first occurrence of an ICD10 hospital diagnosis code of destruction of bones in the ear (H74.3B), cholesteatoma of the external auditory ear canal (H60.4) or cholesteatoma of the middle ear (H71.9). The primary explanatory variable was bisphosphonate exposure.

Results: The overall incidence of cholesteatoma in the ear was low. Only 350 events were seen in 527 176 cases and controls. One hundred and nineteen events of cholesteatoma in the ear were recorded after initiation of bisphosphonate therapy, 34 in the external auditory canal and 85 in the middle ear. Cholesteatoma in the external auditory canal was significantly higher in the exposed than in the unexposed group (P<0.0001). We found a significant dose-event relationship between incidence of cholesteatoma and dose of alendronate (P<0.0001) and etidronate (P<0.0001) Furthermore, we found an association between duration of treatment and risk of cholesteatoma in the external auditory ear canal (log rank, P=0.002).

No cases of bone destruction were observed in cases or controls.

Conclusion: Use of oral bisphosphonates is associated with an increased risk of cholesteatoma of the external auditory canal. The risk is small and associated with duration and dosage of bisphosphonate.