The proximal modular neck in THA: a bridge too far: opposes.

Neck/cup impingement is a serious issue, especially with hard/hard bearings. It can produce noise, locking mechanism failure, and an increase in wear debris and dislocation. The double taper neck used by the author has cogs on the neck/stem taper junction for additional rotational stability. One hundred forty-six procedures were performed using the thin mantle cement technique. Mean follow-up was 5 years (range, 3-8 years). A 32-mm neck was used in 73.8% of cases and a 35-mm neck in 26.2%, because most of the patients were elderly women. The neck was anteverted in 1.4%, neutral in 26.4%, and retroverted in the rest (mild in 34.2%, moderate in 14.3%, and maximum in 13.4%). There were no dislocations and no loosenings. Problems were encountered with the neck/stem taper in 3 cases. The stem was therefore taken off the market. The taper was lengthened and the strength doubled. Since its reintroduction 3 years ago, a further 187 cemented stem procedures have been performed with no failures and no dislocations. Of interest in this series, no necks were anteverted, 23.5% were in neutral, 35.8% were in mild retroversion, 31.1% were in moderate retroversion, and 9.6% were in maximal retroversion. Most necks were placed in retroversion to avoid impingement. This suggests that if a nonmodular neck had been used, some degree of impingement would have occurred in 70% of cases.