A novel method for estimating nail-tract bone density for intertrochanteric fractures

SUMMARY: A novel method based on voxel-based morphometry was proposed to investigate the average volumetric bone mineral density (vBMD) of femoral head nail tract in patients treated with intramedullary nails—proximal femoral nail antirotation (PFNA) and gamma nail (GN). The results showed that there was no significant difference in average vBMD between the two groups. BACKGROUND: For unstable intertrochanteric fractures, poor bone quality might be one of the most important causes of cut-out complications in the femoral head during surgical treatment. Bone quality is generally regarded as an equivalent of BMD. Thus, we develop a novel voxel-based morphometry–based method to quantify vBMD of the femoral head nail tract. METHODS: Automatic calculation of average vBMD of nail tracts requires three main steps. First, we built a standard nail tract in a proximal femur template. Then, we mapped the proximal femur structure of each patient to the template by B-spline and Demons registration so that the anatomical positions of the proximal femur of all patients spatially corresponded to the standard template. Finally, we calculated and visualized the average vBMD distribution of the nail tract of all patients. To verify the feasibility of the method, we enrolled 75 patients (52 women and 23 men) with hip fractures to our study to compare measurements. The root mean square of the standard deviation (RMSSD) was calculated, and the coefficient of variation (CV) of the RMSSD (CV-RMSSD) was used to evaluate the reproducibility of intraoperator and interscan measurements. The Mann–Whitney U test was used to compare the average vBMD of nail tracts for the PFNA and GN. RESULTS: The CV-RMSSD of intraoperator measurements ranged from 1.0% to 2.0%, and the CV-RMSSD of interscan measurements ranged from 3.6% to 4.5%. There was no significant difference in the average vBMD between patients with PFNAs and those with GNs (p > 0.05). CONCLUSIONS: The proposed method is reproducible for determining the average vBMD, which may provide a reference index for selection of appropriate intramedullary nails for individual patients. The current choice of intramedullary nail based on the experience of a surgeon may be biased. THE TRANSLATIONAL POTENTIAL OF THIS ARTICLE: A novel method was proposed to measure the spatial average vBMD of nail tracts, which has good potential to provide a reference index for surgeons to choose appropriate implants.