Cortical Thickness Index and Canal Calcar Ratio: A Comparison of Proximal Femoral Fractures and Non-Fractured Femora in Octogenarians to Centenarians

Background: The cortical thickness index (CTI) is a measure of bone quality and it correlates with the risk of proximal femoral fractures. The purpose of this study was to investigate the CTI in femoral neck, trochanteric fractures and non-fractured femora in geriatric patients and to determine whether there is a correlation between the CTI and the presence of a fracture. Methods: One hundred and fifty patients (fifty femoral neck- (FNFx), fifty trochanteric fractures (TFx) and fifty non-fractured (NFx)) with a mean age of 91 (range 80-104) years were included. Hip radiographs (antero-posterior (ap), lateral) were evaluated retrospectively. Measurements on the proximal femoral inner and outer cortices, including CTI and Dorr's canal calcar ratio (CCR), were assessed for inter-observer reliability (ICC), differences of each fracture and correlation of parameters. Results: The mean ap CTI on the affected side was 0.43, 0.45 and 0.55 for FNFx, TFx and NFx, respectively. There was a significant difference of the ap CTI and CCR comparing the injured and healthy side for both fracture cohorts (p < 0.001). Patients with FNFx or TFx had significantly lower CTI on both sides compared to the NFx group (p < 0.05). There was no difference for CTI (p = 0.527) or CCR (p = 0.291) when comparing both sides in the NFx group. The mean inter-observer reliability was good to excellent (ICC 0.88). Conclusions: In proximal femoral fractures, the CTI and CCR are reduced compared with those in non-fractured femora. Both parameters are reliable and show a good correlation in geriatric patients. Therefore, especially for geriatric patients, the CTI and CCR may help to predict fracture risk and consult patients in daily practice.