Background: Bipolar hip arthroplasty has been advocated by some as
an alternative to total hip arthroplasty for the treatment of degenerative
arthritis of the hip. We sought to assess the results of this procedure at our
institution after a minimum duration of follow-up of ten years.
Methods: We retrospectively reviewed a consecutive series of 152
patients (173 hips) who underwent primary bipolar hemiarthroplasty for the
treatment of symptomatic degenerative arthritis of the hip with a cementless
femoral component between 1983 and 1987. Of the original cohort of 152
patients, ninety-two patients (104 hips) were available for clinical and
radiographic review at a mean of 12.2 years postoperatively. At the time of
the latest follow-up, self-administered Harris hip questionnaires were used to
assess pain, mobility, activity level, and overall satisfaction with the
procedure. Biplanar hip radiographs were made to evaluate bipolar shell
migration, osteolysis, and femoral stem fixation.
Results: At the time of the latest follow-up, nineteen patients
(nineteen hips) had undergone revision to total hip arthroplasty because of
mechanical failure, and three patients (three hips) were awaiting revision
because of symptomatic radiographic mechanical failure. Twelve acetabular
revisions were performed or scheduled for the treatment of pelvic osteolysis
or protrusio acetabuli secondary to component migration. Acetabular
reconstruction required bone-grafting, an oversized shell, and/or a pelvic
reconstruction ring. The overall rate of mechanical failure was 21.2%
(twenty-two of 104 hips), with 91% (twenty) of the twenty-two failures
involving the acetabular component. Reaming of the acetabulum at the time of
the index arthroplasty was associated with a 6.4-fold greater risk of
revision. The rate of implant survival, with revision because of mechanical
failure as the end point, was 94.2% for femoral components and 80.8% for
acetabular components at a mean of 12.2 years. Of the remaining sixty-nine
patients (eighty-one hips) in whom the original prosthesis was retained,
seventeeen patients (24.6%) rated the pain as moderate to severe. Nearly 30%
of patients with an intact prosthesis required analgesics on a regular basis.
Radiographs were available for fifty-eight hips (including all of the hips
with moderate to severe pain) after a minimum duration of follow-up of ten
years; twenty-eight of these fifty-eight hips had radiographic evidence of
acetabular component migration.
Conclusions: This bipolar cup, when used for hemiarthroplasty in
patients with symptomatic arthritis of the hip, was associated with
unacceptably high rates of pain, migration, osteolysis, and the need for
revision to total hip arthroplasty, especially when the acetabulum had been
reamed. To the extent that these findings can be generalized to similar
implant designs with conventional polyethylene, we do not recommend bipolar
hemiarthroplasty as the primary operative treatment for degenerative arthritis
of the hip.
Level of Evidence: Therapeutic Level IV. See Instructions
to Authors for a complete description of levels of evidence.