Surveillance of atypical femoral fractures in a nationwide fracture register

Hans Peter Bögl; Georg Zdolsek; Lukas Barnisin; Michael Möller; Jörg Schilcher

doi:10.2340/17453674.2022.1380

Authors

Hans Peter Bögl Department of Orthopedic Surgery, Gävle Hospital, Gävle; Department of Orthopedic Surgery and Department of Biomedical and Clinical Sciences, Linköping University, Linköping and Center for Medical Image Science and Visualization, Linköping University, Linköping https://orcid.org/0000-0001-9862-1064
Georg Zdolsek Department of Orthopedic Surgery and Department of Biomedical and Clinical Sciences, Linköping University, Linköping and Center for Medical Image Science and Visualization, Linköping University, Linköping https://orcid.org/0000-0001-8566-2983
Lukas Barnisin Department of Orthopedics, Sahlgrenska University Hospital, Gothenburg
Michael Möller Department of Orthopedics, Sahlgrenska University Hospital, Gothenburg; Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
Jörg Schilcher Department of Orthopedic Surgery and Department of Biomedical and Clinical Sciences, Linköping University, Linköping and Center for Medical Image Science and Visualization, Linköping University, Linköping; Wallenberg Centre for Molecular Medicine, Linköping University, Linköping https://orcid.org/0000-0003-0677-9265

DOI:

https://doi.org/10.2340/17453674.2022.1380

Keywords:

atypical femoral fracture, Bone, Fractures, Implants, Osteoporosis, Radiological imaging

Abstract

Background and purpose — To continuously assess the incidence of atypical femoral fractures (AFFs) in the population is important, to allow the evaluation of the risks and benefits associated with osteoporosis treatment. Therefore, we investigated the possibility to use the Swedish Fracture Register (SFR) as a surveillance tool for AFFs in the population and to explore means of improvement.

Patients and methods — All AFF registrations in the SFR from January 1, 2015 to December 31, 2018 were enrolled in the study. For these patients, radiographs were obtained and combined with radiographs from 176 patients with normal femoral fractures, to form the study cohort. All images were reviewed and classified into AFFs or normal femur fractures by 2 experts in the field (gold-standard classification) and 1 orthopedic resident educated on the specific radiographic features of AFF (educated-user classification). Furthermore, we estimated the incidence rate of AFFs in the population captured by the register through comparison with a previous cohort and calculated the positive predictive value (PPV) and, where possible, the inter-observer agreement (Cohen’s kappa) between the different classifications.

Results — Of the 178 available patients with AFF in the SFR, 104 patients were classified as AFF using the goldstandard classification, and 89 using the educated-user classification. The PPV increased from 0.58 in the SFR classification to 0.93 in the educated-user classification. The interobserver agreement between the gold-standard classification and the educated-user classification was 0.81.

Interpretation — With a positive predictive value of 0.58 the Swedish Fracture Register outperforms radiology reports and reports to the Swedish Medical Products Agency on adverse drug reactions as a diagnostic tool to identify atypical femoral fractures.