Abstract
BACKGROUND: Prodromal symptoms might lead to an early diagnosis of atypical femoral fracture (AFF). However, incomplete AFF can progress to complete fractures because they are often misdiagnosed as degenerative diseases such as lumbar canal stenosis or knee and hip osteoarthritis. The purpose of this study was to examine how many AFFs are misdiagnosed as degenerative diseases and the characteristics of the site of prodromal symptoms in a multicenter study. METHODS: We retrospectively analyzed the medical records of patients with AFFs at two institutions. In addition, a survey was sent to affiliated institutions to collect data on prodromal symptoms. RESULTS: Analysis in two institutions revealed 46 AFFs in 35 patients. Seventeen fractures were associated with localized prodromal symptoms in the groin or lateral thigh (conventional type), and 12 fractures had prodromal symptoms not localized to the fracture site, such as widespread lateral thigh, knee, or lateral lower leg (modified type). Eleven fractures were misdiagnosed as degenerative diseases. The survey of 11 affiliated institutions revealed that prodromal pain was reported in 29 of 49 AFFs. Nineteen fractures were associated with modified prodromal pain, and 9 fractures were misdiagnosed as degenerative diseases. CONCLUSIONS: Twenty-one percent of AFFs were misdiagnosed with degenerative diseases. All of the misdiagnosed cases were associated with prodromal symptoms. We believe that the prodromal symptoms of AFF are diverse and very similar to those of degenerative diseases, which may have caused the misdiagnosis.