Between January 22, 1986, and November 17, 1988, the senior author
performed seventy consecutive so-called hybrid revision total hip
arthroplasties in sixty-four patients at Methodist Hospital
in Des Moines, Iowa. The criteria for inclusion in the study was
a revision of both components secondary to mechanical failure of
a cemented total hip prosthesis. Nine patients (nine hips) who had
undergone conversion of a surface replacement or a bipolar hemiarthroplasty
to a total hip arthroplasty or who had had revision of only one
component because of aseptic loosening were therefore excluded from the
study. Thus, fifty-five patients with sixty-one involved hips formed
the study population.
All acetabular components were replaced with a porous-coated
Harris-Galante-I hemispherical acetabular cup
(Zimmer, Warsaw, Indiana), inserted without cement and with supplemental
fixation by two or three 5.1-mm titanium screws through the dome.
The acetabular component was impacted into a reamed bed of the same
diameter (line-to-line fit). It was impacted into viable bone even
if it required placing the component in a high-hip-center position
(that is, with the hip center >30 mm proximal to the interteardrop
line). Fourteen (23%) of the sixty-one components
were placed in this high-hip-center position. No structural bone
grafts were used, and only autograft bone produced by the reaming
was used to fill cavitary defects. All femoral components were replaced
with an Iowa precoated, grit-blasted femoral component
(Zimmer, Warsaw, Indiana), inserted with use of contemporary cementing
techniques (that is, a distal cement plug and a cement gun delivery
system).
At the time of the index revision, the study population included
thirty-one men (56%) and twenty-four
women (44%) who were, on the average, 67.6 years of age
(range, thirty-nine to eighty-nine years of age).
The average height was 168 cm (range, 150 to 185 cm), and the average
weight was 80 kg (range, 40 to 109 kg).
Thirty-one index revisions (51%) were performed
on the right hip and thirty (49%), on the left. The indication
for the revision was aseptic loosening in fifty-six hips
(92%), fracture of the femoral stem in three (5%),
and recurrent dislocation in two (3%). The index procedure
was the first revision in forty-nine hips (80%),
the second in ten (16%), and the third in two (3%).
Of the original fifty-five patients (sixty-one
hips), twenty-eight (thirty-two hips) were alive at the
time of the current study and twenty-seven (twenty-nine
hips) had died from causes unrelated to the index revision.
The living cohort included fourteen men (50%) and fourteen women,
whose average age at the revision was 64.2 years (range, thirty-nine
to seventy-six years). Their average height was 166 cm
(range, 140 to 185 cm), and their average weight was 74 kg (range,
49 to 102 kg). Thirty (94%) of the thirty-two
hips were revised because of aseptic loosening, and two (6%)
were revised because of a fracture of the femoral component. Prior
to the index revision, twenty-eight hips (88%)
had not been revised previously, three (9%) had been revised
once, and one (3%) had been revised twice.
Clinical Evaluation
Clinical results regarding pain, function, and satisfaction were reported
for the twenty-eight living patients (thirty-two
hips), all of whom had been followed for at least ten years (average, 12.9
years; range, 11.5 to 14.3 years). Clinical outcomes were assessed
with use of telephone interviews, conducted by one individual with
a questionnaire employing standard terminology17.
All patients, some with help from their family, were able to answer
the questionnaire.
Clinical results regarding complications and repeat revisions were
reported for all fifty-five patients (sixty-one
hips) in the study group. Relatives of twelve patients (fourteen
hips) who had died subsequent to the minimum five-year
follow-up interval were interviewed by telephone, and this
information was used to identify complications and repeat revisions.
Radiographic Evaluation
Current radiographs were available for thirty hips in twenty-seven
living patients, who were followed for an average of 12.8 years
(range, 10.2 to 14.2 years) subsequent to the index revision. One
living patient (two hips) declined radiographic evaluation; his
most recent radiograph, made at five years, demonstrated maintenance
of the fixation of the acetabular and femoral components. None of
the thirty acetabular components that were examined radiographically
had been revised subsequent to the index procedure.
Two of us examined the most recent of the available anteroposterior
radiographs of the pelvis. For each patient in the study, these
radiographs were compared with the corresponding preoperative and
serial postoperative radiographs, with particular attention given
to the immediate postoperative radiograph.
Preoperative radiographs of all of the patients were evaluated for
osseous deficiencies of the acetabulum with use of a modification
of the system developed by the American Academy of Orthopaedic Surgeons18. Segmental, cavitary, and combined
defects of the acetabular bone stock exceeding 2 cm in width were
recorded.
Pelvic osteolysis of >5 mm2 and
radiolucency at the bone-prosthesis interface were evaluated with
respect to the three zones of the acetabulum described by DeLee
and Charnley19.
The technique proposed by Massin et al.20 was
used to determine the placement of the hip center in relation to
the interteardrop line and to measure migration of the acetabular
component. Migration of the acetabular component was defined as
a change in the vertical or horizontal position of the hip center
of >5 mm. A coefficient, the ratio of the actual and measured
widths of the femoral head, was calculated for each radiograph of
interest and was used to adjust all measurements for magnification.
Digital edge-detection measurement, described by Shaver et al.21, was used to calculate linear and
volumetric acetabular wear. Linear acetabular wear was defined as
penetration of the femoral head into the acetabular liner or shell.
All hips with a minimum of two years of radiographic follow-up
were included in this analysis.
The femoral cementing technique was graded in accordance with
the criteria of Barrack et al.22.
Femoral osteolysis of >5 mm2 and
radiolucency at the bone-cement interface of the femoral component
were localized with respect to the seven zones described by Gruen
et al.23. Radiographic loosening
of the femoral component was classified according to the system
of Harris and McGann24. The greater
trochanter was noted to be united, ununited and stable, or ununited
and migrated. Heterotopic ossification was classified with the scheme
of Brooker et al.25.
Subsidence of the femoral component, defined by Loudon and Charnley26, was noted when an increase of 5
mm in the vertical distance from the tip of the femoral stem to
the drill-hole for the trochanteric reattachment wire in the lateral
cortex was observed.
Debonding was noted when any separation of the femoral stem from
the surrounding cement mantle was seen.
Data Analysis
The Wilcoxon rank-sum test was used to test the correlation of
acetabular wear (linear and volumetric) with gender, preoperative
femoral osteolysis, and preoperative acetabular osteolysis. The
Spearman correlation was used to assess wear as a function of age
at the index revision. The Fisher exact test (two-tailed)
was used for all other comparisons. The prescribed level of significance
was a = 0.05 for all statistical tests.
Kaplan-Meier survivorship analysis27 was
used to estimate the probability of component retention as a function
of time since the index revision. Survivorship analyses were performed
for the following end points: (1) repeat revision of the acetabular
component because of aseptic loosening; (2) radiographic evidence
of probable or definite aseptic loosening of the acetabular component,
including that precipitating repeat revision; and (3) removal or
repeat revision of the acetabular or femoral component for any reason.
Survivorship statistics were reported with corresponding measurements
of standard error.
Clinical Results
At the latest follow-up evaluation, fifteen (47%)
of the thirty-two hips were pain-free, ten (31%)
were occasionally mildly painful, and seven (22%) were
moderately painful, requiring the patient to modify or avoid certain
activities. The study group reported a mean pain index of 2.7 (range,
0 to 8) on an analog scale of 0 to 10, with 0 indicating a complete
absence of pain and 10 indicating extreme pain. Eighteen patients (twenty
hips; 63%) used medication to alleviate hip pain. Of these
patients, sixteen (seventeen hips; 85%) experienced substantial
relief as a result of the medication, one (two hips; 10%)
experienced only minimal relief, and one (one hip; 5%) did
not specify whether pain was relieved. Ten patients (twelve hips;
38%) did not use analgesics specifically for the treatment
of hip pain. Overall, twenty-six patients (thirty hips; 94%)
stated that their pain and dependence on analgesics had decreased
as a result of the index hybrid revision.
Of the twenty-five patients (twenty-nine hips) who responded to
questions about the ability to walk, thirteen patients (fifteen hips;
52%) could walk without support for an unlimited amount
of time, two patients (three hips; 10%) could walk for eleven
to thirty minutes before experiencing major pain, five patients
(five hips; 17%) could walk for two to ten minutes, two
patients (two hips; 7%) could walk for less than two minutes
or indoors only, and three patients (four hips; 14%) could not
walk for any duration in the absence of support. Three patients
(three hips) did not comment on their ability to walk. At the most
recent follow-up evaluation, fourteen patients (sixteen hips; 50%)
did not require ambulatory support, four patients (five hips; 16%)
used a cane on long walks only, nine patients (ten hips; 31%)
needed full-time support, and one patient (one hip; 3%)
was bedridden.
Overall, of the twenty-seven patients (thirty hips) responding to
questions regarding function, who were followed clinically for an
average of 12.9 years, twenty-six patients (twenty-nine hips; 97%)
stated that the index hybrid revision had increased their level
of function and twenty-six patients (twenty-nine hips) were satisfied
with the result of the operation. One patient (one hip; 3%),
an eighty-one-year-old woman with a pain index of 8, was dissatisfied
with the result of the revision. One patient with bilateral revision
did not comment.
Radiographic Results
Of the thirty hips (twenty-seven patients) with complete radiographic
follow-up, seventeen (57%) had had osseous deficiencies
of >2 cm on preoperative radiographs. Eleven acetabula
(37%) demonstrated cavitary defects; five (17%), segmental
defects; and one (3%), combined segmental and cavitary
defects. Osseous deficiencies were absent or unremarkable in thirteen
acetabula (43%).
Immediate postoperative radiographs revealed acetabular radiolucencies
in twenty-four hips (80%). The radiolucencies involved
one zone in seven hips (23%), two zones in ten (33%),
and three zones in seven (23%). At the time of the review,
acetabular radiolucencies were present in twenty-five hips
(83%) and involved one zone in four hips (13%),
two zones in eleven (37%), and three zones in ten (33%). Twenty-one
hips (70%) demonstrated persistent radiolucencies (that
is, present on the immediate and most recent postoperative radiographs),
seventeen hips (57%) had new radiolucencies, and sixteen
hips (53%) had both. No hip demonstrated global acetabular
radiolucencies that included the area of the screws.
Comparison of the placement of the hip center on the immediate
postoperative and most recent radiographs demonstrated migration
and definite loosening of one acetabular component (3%).
It should be noted, however, that this patient reported no functional
deficit, pain, or other complications in association with the index
revision. One other patient, who had died, had had migration of
the acetabular component at three months with no additional migration
during the 9.8 remaining years of her life.
The most recent radiographs demonstrated osteolysis in four acetabula
(13%). The osteolysis involved one zone in three hips (10%)
and three zones in one (3%).
Definite aseptic loosening of the femoral component was observed
in two hips (7%); probable loosening, in no hips; possible
loosening, in one (3%); and no loosening, in twenty-two
(73%). Five hips (17%) had been revised after
the index revision for aseptic femoral loosening. Thus, including
those five hips and the two unrevised hips with evidence of definite loosening,
the overall rate of femoral loosening in living patients was 23%.
Repeat Revisions
At the time of the review, repeat revision had been performed in
thirteen (21%) of the sixty-one hips in the original cohort. Of
these thirteen hips, six were revised because of aseptic loosening
of the femoral component. During three of these femoral revisions
the polyethylene liner was also exchanged, and during one the constrained
liner was cemented into the intact acetabular shell. Four hips had
revision of the femoral component because of recurrent dislocation;
the acetabular liner was exchanged during two of these procedures,
and the constrained liner was cemented into the intact acetabular
shell during the other two. One of these hips was revised again because
of dissociation of the constrained acetabular liner, and the repeat
revision involved cementing of an elevated liner into the intact
acetabular shell. Hence, overall five liners were exchanged and
three constrained polyethylene liners were cemented into intact
acetabular shells. In one additional hip, a lateral lip polyethylene
augmentation was added to the existing liner because of recurrent
dislocation. Two Girdlestone procedures were performed. One, performed
because of recurrent dislocation, entailed removal of the femoral
head only; the acetabular component and the femoral stem were secure
and were left in place. Septic loosening of both components was
the indication for the second Girdlestone procedure. The time until
repeat revision (of any kind) averaged 5.0 years (range, three months
to 12.0 years), and the time until repeat revision of a loose femoral
component averaged 6.8 years (range, 1.1 to 10.3 years).
Statistical Analyses
Correlates of Linear and Volumetric Acetabular
Wear
The mean rate of linear acetabular wear was 0.145 mm/yr (range,
0.000 to 0.392 mm/yr) and the mean rate of volumetric wear
was 48.1 mm3/yr (range, 0.000
to 148.7 mm3/yr) for the thirty-seven
hips (twenty-seven in living patients and ten in patients
who had died) that had been followed radiographically for a minimum
of two years. The acetabular components in male patients demonstrated
significantly greater rates of linear wear (p = 0.005)
and volumetric wear (p = 0.006) than did the acetabular
components in female patients. Furthermore, the rates of linear
(p = 0.031) and volumetric (p = 0.019) wear were
significantly greater in hips exhibiting femoral osteolysis but
were not significantly different in hips exhibiting acetabular osteolysis
(p = 0.791). There was no significant correlation between
age and either the linear wear rate (r = 0.15; p = 0.384)
or the volumetric wear rate (r = 0.21; p = 0.238).
Survivorship Analysis
Overall survival, with removal or repeat revision of either component
for any reason as the end point, was 79.2% ±
5.7% at ten years (Fig. 1-A). With failure defined as repeat
revision of the acetabular component because of aseptic loosening,
the rate of survival was 100% at ten years after the index
revision. With an end point of definite or probable loosening of
the acetabular component, the probability of survival at ten years
was 97.7 ± 2.3% (Fig. 1-B).
Although cementless acetabular fixation has been utilized in revision
hip surgery for more than a decade, there is a paucity of ten-year
follow-up studies16.
Hence, the objective of the present study was to evaluate the durability
of cementless acetabular fixation used in revision hip surgery and
followed for a minimum of ten years. The present study is unique
in that all of the index revisions were performed by the same surgeon,
the femoral components were also revised, and the femoral and acetabular
component designs were uniform across the study populations. Weaknesses
of the study include the potential for intraobserver and interobserver
variability in the interpretation of radiographs and the fact that
the femoral component design (the grit-blasted 80-microinch Ra Iowa
femoral component) had a relatively high failure rate11.
After a minimum ten-year follow-up interval,
none of the acetabular shells had been revised because of aseptic
loosening. Two acetabular shells (3%) were noted to have
migrated. One of these components migrated in the first three postoperative months,
stabilized, and did not migrate further during the remainder of
the patient’s lifetime (9.8 years). The migration of the
other component was detected only through the course of radiographic
measurement; this component had stabilized subsequent to migration,
and the patient was able to function without pain or other complications
at twelve years. These results are comparable with those reported
by Leopold et al., who followed a series of the same Harris-Galante-I
devices for 10.5 years16. In the
present series, despite a well-fixed acetabular shell, nine patients
(nine hips) underwent additional procedures on the acetabulum: five
underwent a liner exchange; three, cementing of a constrained liner;
and one, lateral augmentation of the liner. One of the patients
required an additional liner exchange because of dissociation of
the constrained liner. Osteolysis was noted in four acetabula (13%),
all of which were in living patients with at least ten years of
radiographic follow-up. This prevalence of pelvic osteolysis
is comparable with that reported by Leopold et al. (17%)
in a series of 138 hips followed radiographically for an average
of 10.5 years16. Linear acetabular
wear (femoral head penetration) averaged 0.145 mm/yr in
the present series.
These results represent a marked improvement compared with the
results of the same surgeon using acetabular fixation with cement.
As we previously reported28, at
a minimum of ten years after eighty-one acetabular revisions
performed with cement by the senior author, eleven (14%)
of the acetabular components were revised because of aseptic loosening
and twenty-seven (33%) (including the revised cases) were
loose radiographically. In the only other minimum ten-year
follow-up study of cemented acetabular fixation of which
we are aware, Estok and Harris reported rerevision of seven (22%)
of thirty-two acetabular components and radiographic loosening in
an additional six hips, for a total prevalence of loosening of 41% (thirteen
of thirty-two)29.
The results of cemented femoral fixation in our study group were
not as encouraging, however, as 10% (six) of sixty-one femoral
components were revised because of aseptic loosening and the total
prevalence of femoral loosening was 15% (nine of sixty-one).
These results did not represent an improvement compared with those
in the senior author’s previous series, in which 5% (four)
of seventy-three femoral components were revised because of aseptic
loosening and the total prevalence of femoral loosening was 16% (twelve
of seventy-three)28. On the basis
of these findings, additional investigation of cementless femoral
components and impaction allografting with cement in revision surgery
is warranted.
The findings of this study strongly support the continued use of
cementless acetabular fixation in revision total hip arthroplasty
as the durability of the fixation was better, after a minimum of
ten years of follow-up, than that in series in which cemented
acetabular fixation was utilized. The high polyethylene linear wear
rate (0.145 mm/yr) and the relatively high prevalence of
acetabular osteolysis (13% in living patients) will require
further follow-up to determine their importance in terms
of component durability.