Value of Proximal Femur Geometry in Predicting Occult Hip Fracture

Abstract

Background and Objectives: Patients with occult hip fractures are a difficult subgroup to treat. MRI is the gold standard for diagnosing occult proximal femur fractures but is costly and may not be readily available in an emergency setting. The purpose of this study was to determine whether changes in the proximal femur geometry can predict the likelihood of an occult hip fracture in patients presenting with hip pain following a ground-level fall. Material and Methods: Patients admitted to the hospital with a clinical suspicion of a hip fracture but initial negative radiographs over a seven-year period were included. All patients were additionally investigated with an MRI scan, and retrospectively, six radiologic parameters were obtained on plain radiographs: The cortical thickness index (CTI), the canal to calcar ratio (CCR), the canal flare index (CFI), the morphological cortical index (MCI), the canal bone ratio (CBR) and the canal bone aria ratio (CBAR). Subsequently the result of the plain radiographic indices of the patients with a negative MRI (Group A, no occult fracture) were compared to those with a positive MRI (Group B, occult fracture). Results: A total of 78 patients (59 female, 19 male) could be included in the study. The mean age was 82 years. The univariate analyses revealed a poor predictive ability of all radiological parameters with AUC values ranging from 0.515 (CBR) to 0.626 (CTI), whereas a multivariate prognostic model demonstrated improved prognosis (AUC = 0.761) for the CTI (p = 0.024), CBAR (p = 0.074) and CRR (p = 0.081) as the most promising predictive radiological parameters. Conclusions: Single radiologic indices obtained from conventional X-rays of the proximal femur have a weak predictive value in detecting occult fractures of the hip and cannot be used as clinical decision-making factors.

Keywords

• occult proximal femur fracture
• fragility fracture
• radiographs
• cortical thickness
• femoral geometry