The impact of modularity in total hip arthroplasty.

Use of modularity in total hip arthroplasty has been of benefit in terms of allowing inventory reduction while providing surgeon versatility and thus optimal joint reconstruction. As with any advancement, the improvements gained must be weighed against their cost. The authors sought to examine the effects that modularity may have on the results of total hip arthroplasty in terms of bone loss, durability of fixation, time to failure, and incidence of revision. Using data from their total joint registry, the authors examined their experiences with total hip arthroplasties done during the past 25 years. They sought to compare the results of total hip arthroplasties in patients who differed chiefly by the number of modular junctions present in their hip prostheses. With each incremental increase in modularity, an earlier appearance of radiolucencies, an earlier occurrence of aseptic loosening, and an increased incidence of osteolysis in the absence of loosening was found. The authors conclude that suboptimal design rather than the concept of modularity best explains these results. The presence of suboptimal design in a total hip arthroplasty may cause polyethylene to be stressed beyond its performance limits.