At a minimum of fifteen years postoperatively, forty-one patients
(forty-three hips) had died, seven patients (eight hips) had been lost to
follow-up, and twenty patients (twenty hips) had undergone a repeat revision
of the acetabular component. This left sixty-seven hips in sixty-four patients
for the present study. The mean age of these sixty-four patients at the time
of surgery was fifty-five years old. Fifty-four patients (fifty-seven hips)
were evaluated both clinically and radiographically, and ten patients (ten
hips) had a clinical evaluation only. The ten patients completed a telephone
questionnaire but either could not or would not have new radiographs made. The
latest clinical and radiographic evaluations were performed at a mean of 205
months (range, 180 to 231 months) postoperatively. A comparison of the results
between the current and previous studies is shown in
Table I.
The Harris hip score for the patients who did not have a repeat revision
improved from a mean of 49 points preoperatively to a mean of 82 points
(range, 38 to 100 points) at the most recent evaluation (p < 0.001). A
comparison of the hip scores in the present study with those in the previous
studies is shown in Table II.
Of the fourteen patients with a poor score, seven had severe low-back pain,
two had polyarticular arthritis, and one had a cervical spine disorder; the
poor scores for the remaining four patients were directly related to a poorly
functioning hip replacement.
Of the 138 hips in the entire cohort of 132 patients, twenty (14%)
underwent repeat revision of the acetabular component. Seven repeat revisions
(5%) were performed because of recurrent dislocation; five of these procedures
followed the index revision, and two followed a later femoral revision. All of
these metal shells were well fixed. Seven metal shells, six of which were well
fixed, were removed at the time of femoral revision surgery, and six were
revised because of infection. Thus, at the time of the repeat revision,
nineteen of the twenty components were deemed to be well fixed. The one
patient with a loose metal shell underwent revision at 122 months because of
aseptic loosening of the femoral component. At the time of surgery, the screws
were removed and the metal shell was found to be fixed by fibrous tissue only
and was removed. Preoperative radiographs showed a radiolucent line of <2
mm in thickness in four of the five zones surrounding this component. In the
entire cohort of sixty-seven hips that were followed for a minimum of fifteen
years, thirty-eight did not require a reoperation and still had the original
femoral component, acetabular component, and polyethylene liner in place at
the most recent evaluation.
Two patients underwent a reoperation on the hip for a problem directly
related to the acetabular component but did not require revision of the metal
shell. One of these patients, who was twenty-six years old at the time of the
index revision, underwent the reoperation because of excessive wear of the
polyethylene liner at 142 months postoperatively; the metal shell was found to
be well fixed at the reoperation and was retained. The polyethylene liner in
this patient was 9.2 mm in thickness. The other patient, who was thirty-five
years old at the time of the index revision, underwent a repeat revision
because of wear of the polyethylene liner and osteolysis at 189 months; the
metal shell was found to be well fixed at the reoperation and was retained.
The polyethylene liner in this patient was 6.2 mm in thickness. A comparison
of the repeat acetabular revisions reported in this study and our previous
studies is shown in Table
III.
In the entire cohort of 138 hips, two metal shells (1.4%) were definitely
loose as seen radiographically. One patient died before revision surgery was
required, and the other patient was asymptomatic and elderly at the time of
writing. Of the fifty-seven metal shells that were followed radiographically
for more than fifteen years, one was definitely loose, six were possibly
loose, and fifty were deemed to be well fixed
(Table IV). All six of the
possibly loose components had previously been classified as possibly loose,
and none showed evidence of progressive radiolucent lines. Four of these six
components were in patients with a Harris hip score of >90 points, and the
two remaining components were in the same patient, who, at the time of
writing, was ninety years of age and had multiple medical comorbidities and
musculoskeletal problems.
Twenty-three (40%) of the fifty-seven metal shells that survived and were
followed radiographically for more than fifteen years were associated with
osteolysis; nine (16%) of the osteolytic lesions were >1 cm in diameter. In
the entire cohort of 138 metal shells, twenty-seven (20%) were associated with
radiographic evidence of osteolysis, and eleven of the lesions were >1 cm
in diameter (8% prevalence in the series). Of the twenty-nine osteolytic
lesions, fifteen were small peripheral lesions, eleven were large peripheral
lesions, one was a small retroacetabular lesion, and two (including the one in
the patient who had a reoperation because of the osteolysis) were large
retroacetabular lesions. Osteolysis was first identified radiographically at a
mean of 137 months (range, fifty-nine to 223 months) after the index
operation.
In the entire cohort of 132 patients (138 hips), the fifteen-year rate of
survival of the acetabular component, with failure defined as revision of the
acetabular metal shell because of aseptic loosening or radiographic evidence
of definite loosening, was 97%. With failure defined as a revision of the
acetabular component for any reason, the fifteen-year survival rate was 81%.
At fifteen years, 70% of the shells were not associated with radiographic
evidence of osteolysis. Kaplan-Meier curves with 95% confidence intervals for
these outcomes are shown in Figures
1,
2, and
3.
With the numbers available, log-rank tests and bivariate Cox regression did
not identify a significant relationship between the time to radiographic
identification of osteolysis and gender, weight or body mass index, liner
thickness, femoral head type, or acetabular inclination angle. However, age
was found to be significant (p = 0.012), with the risk of osteolysis
decreasing as age increased. Age was the only variable that was included in
the final model produced by backward-elimination Cox regression. Similar
results were obtained for the time to the first reoperation: age (p = 0.001)
was the only significant variable (the risk of a reoperation decreased as age
increased) and the only variable kept in the final Cox regression model.
Although not the focus of this report, the outcomes with regard to the
femoral components were also studied. Fifty-two (38%) of the 138 femoral
components were rerevised at a mean of ninety-eight months (range, one to 203
months). Forty-two were re-revised because of loosening; five, because of
infection; three, because of distal osteolysis; and two, because of
periprosthetic fracture. The modular polyethylene acetabular liner was changed
at the time of all fifty-two femoral revisions. Eighteen (38%) of the
forty-eight cementless Harris-Galante stems, sixteen (37%) of the forty-three
cementless Gustilo-Kyle stems, eight (38%) of the twenty-one cementless BIAS
stems, one (14%) of the seven cemented Harris Precoat stems, and the one
allograft-prosthesis composite were revised. Eight (44%) of the eighteen
cemented femoral components that had been retained at the time of the index
acetabular revision were revised, at a mean of 105 months (range, forty-five
to 167 months) postoperatively. The rate of survival of the femoral components
at fifteen years was 58% with revision because of aseptic loosening as the end
point, and it was 52% with revision of the femoral component for any reason as
the end point. Kaplan-Meier curves with 95% confidence intervals for these
outcomes are shown in the Appendix.
Harris-Galante cementless metal shells used for acetabular revision
arthroplasty performed well, with a low rate of aseptic loosening at a minimum
of fifteen years postoperatively. However, since our previous reports, we
found an increase in the prevalence of periacetabular osteolysis. The most
common reasons for repeat revision of the metal shell were recurrent
dislocation and infection. On the basis of this finding, we now routinely use
larger-diameter (36 and 40-mm) femoral heads that articulate with a highly
cross-linked polyethylene liner to try to decrease the rate of dislocation.
Although six well-fixed shells were removed at the time of femoral revision
surgery, we currently recommend retaining well-fixed and well-positioned
acetabular components at the time of femoral revision
surgery8.
On the basis of the results of this and our previous reports, we continue
to use a hemispherical, titanium metal shell with multiple screws for fixation
in the vast majority of our acetabular revisions. Although the component
described in this report is no longer available, the component that we
presently use (Trilogy; Zimmer) is hemispherical and has the same ingrowth
surface as its predecessor. However, larger-diameter screws are used, and the
locking mechanism for the modular polyethylene liner has been improved.
Kaplan-Meier survivorship curves for the femoral components are available
with the electronic versions of this article, on our web site at
(go to
the article citation and click on "Supplementary Material") and on
our quarterly CD-ROM (call our subscription department, at 781-449-9780, to
order the CD-ROM). ?
Note: The authors thank Mitchell B. Sheinkop, MD, for the
contribution of cases for this series.