Total hip acetabular cup flange design and its effect on cement fixation.

The design of pods and flanges on the acetabular cup surface was investigated to determine the effects on cement fixation of the total hip arthroplasty (THA) acetabular cup. To a basic cup designed with pods, four different types of flange designs were added: a cup without a flange, a cup having a flange with 12 scallops, a cup having a flange with three scallops, and a cup having a continuous flange. The cups were each inserted, via an MTS machine, into an instrumented simulated acetabulum containing polymerizing polymethylmethacrylate (PMMA). The PMMA intrusion pressure was measured by four pressure transducers, and the cement intrusion depth was measured via three rheometers. Also, three continuous-flange cups were manually inserted into cadaver acetabula in order to study the shape of the cement mantle around the cup. A cup with a continuous flange generated significantly higher cement intrusion pressures and depths when compared with the other three cups. A cup with pods and a continuous flange produced concentric positioning of the cup with a uniform cement thickness around the cup and was well contained within the reamed acetabulum.