Effect of Bone Type on Clinical and Radiographic Outcomes of a Proximally-coated Cementless Stem in Primary Total Hip Arthroplasties

We determined the effect of pre-operative bone structure upon the temporal effects of remodeling after total hip arthroplasty (THA) in a series of uncemented implants. We evaluated 345 patients (375 hips), who had either Dorr Type-A (238 hips) or Type-B (137 hips) bone, and who received a proximally-coated cementless THA and were followed for a mean of 6 years. Outcomes evaluated included aseptic survivorship, Harris hip scores, and radiographic evaluation for patterns of remodeling. The aseptic survivorship (97.5% vs. 98%) and the mean final Harris hip scores (92 vs. 94 points) were similar between Types-A and -B bone, respectively. Bone remodeling was seen significantly earlier and over a longer duration for patients who had Type-B bone. At 5-years, periprosthetic condensation (78% vs. 54%) and cortical hypertrophy (53% vs. 37%) were significantly higher and radiolucencies at any zone were lower (53% vs. 37%) in Type-B compared to Type-A bone. There was increased condensation in men and higher cortical hypertrophy in women. Various radiographic remodeling differences may not negatively impact clinical outcome at mid-term follow-up. Morphologic bone type appears to be predictive of physiologic response to loading.