Is metal-on-metal squeaking related to acetabular angle of inclination?

Postoperative audible squeaking has been well documented in ceramic-on-ceramic hip prostheses, and several metal-on-metal (MOM) THA designs, specifically those used for large-head resurfacing and MOM polyethylene sandwich designs, and are attributed to different implant- and patient-specific factors. Current literature does not identify the incidence of squeaking in modular MOM THA or possible etiologic factors.

Our purposes were to (1) identify the incidence of squeaking in modular MOM prostheses in THA; (2) determine whether males or females were more likely to have squeaking; and (3) determine whether the incidence of squeaking relates to acetabular inclination angle.

We retrospectively reviewed the patient records and radiographs of 539 patients (542 hips) from three independent centers who underwent a MOM THA between February 2001 and December 2005. Demographic and implant factors were evaluated, including measurement of cup inclination angles. The minimum followup was 36 months (mean, 76 months; range, 36-119 months).

We identified squeaking in eight of the 542 hips (1.5%); five were in women and two were in men (one patient had bilateral squeaking). The time to onset of patient-reported audible squeaking averaged 23 months (range, 6-84 months). Squeaking was more likely to occur in women (six of eight hips). No hips with 45º or less acetabular inclination squeaked (291 hips); eight of 251 hips (3.2%) with inclination angles greater than 45º squeaked. Patients who reported squeaking had higher inclination angles than those who did not report squeaking.

Our observations suggest an increased frequency of squeaking in female patients and in patients with greater inclination angles with this MOM implant design.