Background
and purpose — We previously reported a transient, bone mineral density
(BMD)-dependent early migration of anatomically designed
hydroxyapatite-coated femoral stems with ceramic–ceramic bearing
surfaces (ABG-II) in aging osteoarthritic women undergoing cementless
total hip arthroplasty. To evaluate the clinical significance of the
finding, we performed a follow-up study for repeated radiostereometric
analysis (RSA) 9 years after surgery.

Patients
and methods — Of the 53 female patients examined at 2 years
post-surgery in the original study, 32 were able to undergo repeated RSA
of femoral stem migration at a median of 9 years (7.8–9.3) after
surgery. Standard hip radiographs were obtained, and the subjects
completed the Harris Hip Score and Western Ontario and McMaster
Universities Osteoarthritis Index outcome questionnaires.

Results
— Paired comparisons revealed no statistically significant migration of
the femoral stems between 2 and 9 years post-surgery. 1 patient
exhibited minor but progressive RSA stem migration. All radiographs
exhibited uniform stem osseointegration. No stem was revised for
mechanical loosening. The clinical outcome scores were similar between 2
and 9 years post-surgery.

Interpretation
— Despite the BMD-related early migration observed during the first 3
postoperative months, the anatomically designed femoral stems in aging
women are osseointegrated, as evaluated by RSA and radiographs, and
exhibit good clinical function at 9 years.