Risk factors for atypical forearm fractures associated with bisphosphonate usage

The purpose of this study was to find the diagnostic factors for atypical forearm fractures additional to atypical femur fractures, via a retrospective case-control study. Thus, our authors performed a complete enumeration survey for patients under the treatment of bisphosphonate (BP).

We identified 53 patients that met the following inclusion criteria between March 2009 and February 2019: a BP therapy history or ongoing administration of at least 1 year, presence of simple radiographs of bilateral femurs and forearms, and availability of complete medical records and radiological data. The patients were divided into two groups: those with any lesion of atypical fractures of ulna or radius, regardless of the displacement of at least one side extremity in simple radiographs (group 1, 20 patients); and those without any lesions of pathognomonic finding or fractures in either forearm in simple radiographs (group 2, 33 patients).

Univariate analyses of basic demographic characteristic such as age, smoking, comorbidity of diabetes mellitus or any connective tissue disease needing steroid treatment, and BMD showed no significant differences between the groups (P > 0.05). The co-morbidity of malignant cancer inevitably needing BP usage was not different between the two groups. Multivariate analyses of the several variables that differed significantly between the two groups in univariate analyses demonstrated that total period and single prescribing physician/surgeon were significantly associated with forearm fractures. A cut-off value of 65 months for the total period predicted the presence atypical forearm fractures.

Atypical forearm fractures are probably more common than reported in the literature to date, and all forearm lesions were accompanied by preceding atypical femur fractures. The period of BP administration had the main effect on the occurrence of atypical forearm fractures, particularly if more than 65 months. Also, the prescription by multiple physician was predicting factor for forearms lesion additionally to AFFs, however, more evidence-based study is needed to understand the effects of cancer-related BP usage on the forearm.

Level III, retrospective case-control study.