Component impingement is frequently observed in cups after removal, but is rarely found as a direct indication for revision, except in case of hard-on-hard friction couples (polyethylene being the most impingement-tolerant material). Systematic use of extended head flanges and elevated antidislocation rims is not to be recommended, especially in case of excessive ROM. A good head/neck ratio should be sought, notably by increasing the head diameter in less impingement-tolerant hard-on-hard friction couples. Although not identified as a risk factor in the present study, implant orientation should be checked; computer-assisted surgery can be useful in this regard, for adaptation to the patient's individual range-of-motion cone.

Level 3 prospective observational prognostic study.

Adequate selection of MoM articulations ensures their safe use. These articulations are sensitive to orientation. Fifteen years of safe experience with 28- and 32-mm bearings of forged alloy and high-carbide content is the main reason for retaining them in primary and revision THA.