Cortical bone density of the proximal femur following cementless total hip arthroplasty.

A quantitative analysis of cortical bone remodeling was performed using calibrated videodensitometry. Six femoral specimens were obtained at autopsy from 3 patients treated with unilateral porous coated femoral components in situ > 6 years. Transverse thick sections of the remodeled and normal femora were obtained. Slab radiographs of the sections were analyzed using computer assisted videodensitometry. Detailed density plots of each section were constructed and the average density in defined quadrants was recorded. The density plots were also used to measure the cortical bone area present on each section. Two cases showed a gradient of resorptive remodeling change with the greatest density loss noted medially at the proximal levels (33% and 36%). The 3rd case had porotic cortical bone in the normal femur and demonstrated a different remodeling pattern, with the greatest average resorptive change (57%) measured in the midstem region. Changes in cortical area were variable: 1 showed cortical thickening in the midstem region; another had decreased cortical area in the entire region adjacent to the porous coating; and the 3rd had decreased cortical area proximally, with minimal changes noted in the distal levels. The volumetric densities measured by videodensitometry were compared with area densities measured with dual energy xray absorptiometry. There was a strong linear correlation between the 2 methods (r2 = 0.80).