A computational 3D analysis for assessing bone remodeling following total hip arthroplasty: a longitudinal study spanning six years

Objectives: This study aimed to enhance the comprehension of volumetric bone mineral density (vBMD) changes following Total Hip Arthroplasty (THA) by establishing a protocol to (i) precisely locate alterations in the proximal femur in three dimensions and (ii) evaluate these changes over an extended period. Methods: Twelve individuals who underwent unilateral THA, using either cemented or uncemented prostheses, were recruited. CT-scans of the proximal femur were acquired at three distinct time points: 24 h, 1 and 6 years post-surgery. Utilizing the acquired data, 3D models of the proximal femur were generated, and a novel algorithm was developed to categorize them into Gruen zones. Comparative analysis of density values among the three sets of scans allowed the calculation of bone density gains/losses for the entire proximal femur and specific regions. Results: A lower trabecular bone quantity was observed in the cemented group compared to the uncemented cohort, with discernible differences in vBMD evolution observed in the overall femur and certain Gruen zones. Noteworthy inter-patient variability was evident, ranging from physiological bone remodeling to unexpected increases/decreases in vBMD (e.g.,+340% after one year). Conclusions: This analysis proves to be a valuable tool to understand the long-term vBMD evolution in THA patients.