Acetabular cup groove and pod design and its effect on cement fixation in total hip arthroplasty

The effect of pods and grooves of a total hip acetabular cup on the cement-cup interfacial fixation strength was studied with five differently designed acetabular cups. The first cup had no pods and no grooves; the second cup had pods and no grooves; the third cup had pods and 1.0-mm-deep grooves; the fourth cup had pods and 1.5-mm-deep grooves; and the fifth cup had pods and 1.5-mm-deep, undercut grooves. All were embedded in cement and in block molds and were torsionally loaded until failure. The cup with no pods and no grooves showed almost no torsional resistance when compared to the cups with pods. While no statistically significant difference was found among the different depths of grooves, the addition of undercutting of grooves tended to give higher resistance to torsional load when compared with the plain grooved cups. Pods and grooves on the cup are prerequisites for adequate fixation; however, deeper grooves not only are unnecessary but pose potential problems in regard to creep, fracture, and wear. Pods on the cup aid in positioning the cup in a concentric manner.