Study Group
Institutional review board approval and patient consent were obtained prior
to the initiation of the study. The cohort consisted of fifty-eight patients
(sixty-six hips) who underwent an uncemented total hip arthroplasty between
1997 and 2003. All patients had biopsy-confirmed adenocarcinoma of the
prostate and had been managed with definitive or adjuvant irradiation to the
pelvis prior to undergoing total hip arthroplasty. Patients with pathological
fracture, metastatic disease, and those undergoing revision arthroplasty were
excluded. The mean age at the time of the operation was seventy-four years
(range, fifty-six to eighty-nine years). The underlying diagnosis was
degenerative joint disease in thirty-five hips (53%) and radiation-induced
osteonecrosis of the femoral head in thirty-one hips (47%). All patients with
osteonecrosis had complete collapse of the femoral head. The majority of
patients had a history of concomitant medical comorbidities with a mean
American Society of Anesthesiology score of 2.44 (range, 1.0 to 3.0). The
average height was 176.0 cm (range, 157.5 to 188.0 cm), and the average weight
was 82.4 kg (range, 58.5 to 126.9 kg).
Cancer Data
All patients had adenocarcinoma of the prostate, which was diagnosed on the
basis of histological examination. All patients had received irradiation to
the pelvis at a mean of 66.7 months (range, one to 292 months) prior to
undergoing total hip arthroplasty. The types of radiation therapy included
external beam radiation (range, 6 to 25 MV) in fifty-three patients (sixty
hips) and permanent radioactive seeds (14,500 cGy) with iodine-125
combined with external beam irradiation in five patients (six hips). The
average dose of total external beam radiation was 7065 cGy (range, 6440 to
7900 cGy) administered over a mean of thirty-six fractions (range, forty to
forty-four fractions) and a mean of fifty-four days (range, forty-eight to
fifty-nine days). Three patients (three hips) received the application of
intensity modulated radiation therapy. Radical prostatectomy had been
performed in eighteen patients (twenty hips). Adjuvant androgen suppression
therapy was administered in twenty-three patients.
Surgical Data
Total hip arthroplasty was performed with the patient under regional
anesthesia and in the supine position and with use of an anterolateral
approach. All patients underwent uncemented total hip arthroplasty with use of
a plasma-sprayed hemispherical acetabular component (PSL [Stryker
Orthopaedics, Mahwah, New Jersey] or Universal [Biomet, Warsaw, Indiana]) and
a proximally coated collarless tapered femoral stem (Taperloc [Biomet] or
Accolade [Stryker Orthopaedics]). The acetabulum was reamed to reveal a
bleeding osseous bed prior to insertion of the components. Acetabular
components were inserted with a press-fit in accordance with the
manufacturer's recommendation of underreaming the acetabulum by 1 mm.
Supplemental screw fixation was used in eighteen hips. The mean outer diameter
of the acetabular component was 56 mm (range, 50 to 62 mm). The type of
bearing surface utilized was at the discretion of the surgeon and included
Trident ceramic-on-ceramic (Stryker Orthopaedics) in thirty hips and metal on
highly cross-linked polyethylene (Crossfire; Stryker Orthopaedics, or Arcom;
Biomet) in the remaining thirty-six hips. Femoral components were inserted
with a press-fit after appropriate reaming and broaching of the proximal
femoral canal. No intraoperative fractures were identified. The estimated
blood loss in this series averaged 265 mL (range, 100 to 550 mL), resulting in
the need for an average transfusion of 1.5 units of blood per patient.
Postoperative Protocols
All patients received a second-generation cephalosporin antibiotic (Ancef;
cefazolin) prior to the induction of anesthesia and for twenty-four hours
after surgery. Coumadin (warfarin) was administered for six weeks
postoperatively for thromboprophylaxis. Patients were encouraged to walk with
assistance and were allowed to bear weight as tolerated starting the day after
surgery. Patients were instructed to use a walking aid until they were able to
walk without a limp. Precautions against dislocation included limitation of
hip flexion to <90°, avoidance of adduction, and avoidance of excessive
external rotation. Patients were allowed to ride in a car as a passenger,
drive a car, sleep on their side, or engage in any other activities if they
were able to and so desired.
Outcome Assessment
All data were retrospectively retrieved from the clinical and radiographic
records of the patients. The functional outcome was assessed with use of the
Harris hip score16
and the Short-Form Health Survey (SF-36)
questionnaire17.
Preoperative and postoperative sequential anteroposterior radiographs of the
pelvis and anteroposterior and lateral radiographs of the hip were evaluated
for radiolucent zones around the uncemented femoral
component18 or the
acetabular component
19, assessment of
component positioning, and evidence of osteolysis, pedestal formation, and
component
subsidence20.
Femoral loosening was evaluated according to the criteria described by Engh et
al.18. Acetabular
loosening was assessed according to the method of Yoder et
al.21.
Postoperative heterotopic ossification was graded according to the
classification by Brooker et
al.22.
The orientation of the femoral component was classified as valgus, slight
valgus, neutral, slight varus, or varus alignment. Slight varus or slight
valgus alignment was used to describe a femoral stem with <5° of
malalignment with respect to the neutral axis of the femoral canal. Varus or
valgus alignment was used to describe a femoral stem that was oriented
=5° beyond neutral.
Follow-up
The mean duration of follow-up was 4.8 years (range, two to 7.5 years). All
patients were followed for a minimum of two years or until the failure of the
prosthesis or death. No patient died in the first six months. Three patients
(four hips) died within two years following surgery, and four patients (four
hips) were lost to follow-up. Hence, the final analysis is based on fifty-one
patients with fifty-eight hip replacements.
Statistical Analysis
Statistical evaluation was carried out with use of the SPSS software
package (SPSS, Chicago, Illinois). The changes in the Harris hip scores and
SF-36 were evaluated with the Student t test and the Pearson nonparametric
chi-square test. Statistical significance was determined with use of a 95%
confidence interval.
Functional Outcome
In fifty-one patients (fifty-eight hips) who were still living and had
adequate follow-up, the mean Harris hip score significantly improved from 47
points (range, 8 to 81 points) preoperatively to 90 points (range, 42 to 100
points) at the time of the latest follow-up (p < 0.05). Similarly, two
summary measures of the SF-36 improved significantly after surgery. The
summary measures for physical and mental health improved from a mean of 45.1
points and 65.3 points, respectively, before the operation to a mean of 73.4
and 83.7 postoperatively (p < 0.05 for both comparisons). The hips were
fully functional at the time of latest follow-up for the patients who were
lost to follow-up or who had died.
Radiographic Findings
The radiographs of all patients, including those who had died, were
reviewed. All uncemented femoral and acetabular components showed evidence of
osseointegration and were deemed to be stable at the latest follow-up
evaluation. The position of the acetabular component was between 40° and
50° of abduction and 15° and 20° of anteversion in all hips. The
femoral component was in neutral alignment in sixty-three hips and was
positioned in slight varus alignment in three hips. A nonprogressive
radiolucent line (<2 mm) was noted around the acetabular components in two
hips (zone 1 in one hip and zone 2 in one hip) and around the femoral
component in six hips. A distal pedestal that was in contact with the tip of
the stem was noted in two hips. Heterotopic bone formation was seen in four
hips and was categorized as class I in three hips and class II in one hip. One
femoral component had subsided and subsequently underwent revision.
Complications
There were no intraoperative complications. Postoperative medical
complications developed in ten patients and included postoperative confusion
(three patients), atrial fibrillation (two patients), urinary tract infection
(two patients), exacerbation of chronic renal failure (one patient),
myocardial infarction (one patient), and aspiration pneumonitis (one
patient).
A postoperative wound discharge developed in three hips; it resolved
without surgical treatment in all three and the wounds healed per primam.
There were no skin problems. One hip dislocated despite having appropriately
positioned and fixed components. It was treated successfully by a single
closed reduction. Other perioperative complications included deep-vein
thrombosis in one patient and transient peroneal nerve palsy in another. One
hip had a deep infection, which required a subsequent resection
arthroplasty.
Reoperations and Revisions
One patient underwent resection arthroplasty of an infected hip. There were
two additional revisions. One patient had subsidence of an undersized femoral
component that required revision to an extensively coated stem. The other
revision was performed in a patient who sustained a periprosthetic fracture
around the femoral component after a fall in the early postoperative period.
None of these complications were deemed to be related to irradiation, the
underlying cancer, or metastatic disease.
In the past decade, medical advances have resulted in longer life
expectancy in general, a better survivorship of certain cancer patients, and,
specifically, an improved prognosis for patients with prostate
cancer10,23,24.
With the exception of skin cancer, prostate cancer is the most commonly
diagnosed cancer in men in the United
States10,11,23.
The age-adjusted incidence of invasive prostate cancer is 161.2 per 100,000 in
the United
States12. Because
patients with cancer of the prostate are generally older, it is not uncommon
that orthopaedic surgeons encounter patients with prostate cancer and severe
arthritis of the hip who are candidates for total hip arthroplasty.
Radiation therapy has become a common treatment modality for patients with
adenocarcinoma of the prostate. Because of the anatomic vicinity of the
prostate bed, the hip may be exposed to a large radiation dose. Modern
conformal radiation therapy has been used to limit exposure of the bladder,
rectum, and the adjacent sites to the radiation. With use of a six-field
three-dimensional conformal plan, the average dose to the hips is
approximately 4000 cGy (Figs. 1-A and
1-B, 1-C and 1-D)
of a total dose of 7560 cGy. The latest technological advance in the field of
radiation oncology is the application of intensity modulated radiation
therapy, which allows for more precise radiation delivery than conventional
conformal radiation therapy. With use of intensity modulated radiation
therapy, the beam is modulated to further conform the radiation to the target.
The target in this example is the prostate and seminal vesicles, as well as
the periprostatic lymph nodes for high-risk disease. The enhanced precision
from intensity modulated radiation therapy allows for greater sparing of the
bladder, rectum, and hips. A reduction of 1000 cGy to the hips can be achieved
with use of this technique. Although the results of intensity modulated
radiation therapy are not fully known, there appear to be fewer side effects
with its use. In this study, only three patients received intensity modulated
radiation therapy.
Ionizing radiation is known to have a deleterious effect on the bone in a
dose-related
manner25-29.
Although the exact biological mechanisms underlying radiation osteonecrosis
remain undefined, ionizing irradiation has been shown to result in decreased
osteocyte number, suppressed osteoblast activity, and diminished
vascularity30. This
may decrease successful osseous repair by altering cytokine expression
profiles resulting from or leading to a change in the osteoblastic
differentiation
state30-32.
These changes may, in turn, cause alterations in osteoblast proliferation and
extracellular matrix formation.
Because of the adverse biological effects of irradiation on bone, and the
potential for reduced osseointegration, total hip arthroplasty with cement may
seem to be a better alternative for patients with prior irradiation to the
pelvis6,8,9.
However, the outcome of total hip arthroplasty with cement for patients with
an irradiated pelvis has been uniformly
disappointing2,6,8.
In a study involving forty-two hips in patients who had had a total hip
replacement after pelvic irradiation, Massin and
Duparc8 reported
that 52% (twenty-two) of the acetabular components and 12% (five) of the
femoral components were loose at a mean follow-up of sixty-nine months. In a
recent study of eighteen hips that had been followed for a mean of fifty-eight
months, Cho et al.6
reported a 50% failure rate of both cemented (two of four hips) and uncemented
acetabular components (seven of fourteen hips) without any femoral loosening.
In a study of eight patients (nine hips) who had uncemented total hip
arthroplasty in a previously irradiated pelvis, the outcome was also
disappointing, with a failure rate of four of nine hips at a mean of
twenty-five
months9.
Our encouraging findings are in contrast to those reported in the
literature for a number of reasons. First, our study consisted of a
homogeneous group of patients with adenocarcinoma of the prostate who had
received moderate to high doses of radiation. In contrast, previous studies
have included patients with gynecological malignant lesions, such as cervical
and endometrial cancer, lymphoma, or colorectal cancer, who would have
received varying doses of
radiation6-9.
Since the exact dose of radiation was not disclosed in detail in those
studies, a direct dose comparison was not possible. Second, our patients
underwent total hip arthroplasty in recent years and were likely to have
benefited from the improvement in surgical techniques and component designs
that have occurred over the last two decades. Finally, our study involves male
patients exclusively. Over 95% of the patients in previous studies were
female6-9.
Male patients with better bone density and bone quality may be less vulnerable
to mechanical and biological problems such as component subsidence and
periprosthetic fractures.
Because of their older age and the underlying malignant tumor, the patients
in our cohort had likely received more intense medical preparation prior to
arthroplasty. This may have prevented potentially catastrophic complications
that can occur at a high frequency in these
patients33-35.
Diligent prophylaxis against thromboembolism and infection, both of which are
common in patients with cancer and previous
irradiation36-39,
were administered. This was despite the fact that the diagnosis of cancer and,
in some instances, the administration of radiation therapy had occurred many
years prior to the total hip arthroplasty. Only five patients had the total
hip arthroplasty within one year after pelvic irradiation. Although the dose
of radiation received by the patients in this study varied, all patients
received >5000 cGy to the prostate, a dose known to be critical for cell
death9,28.
A dose-response relationship between the dose of radiation received by the
hips and the failure of the arthroplasty components is still
lacking9. On the
basis of the literature, it is plausible that the number of fractions and the
duration of exposure (elapsed days) are likely to be more important
determinants of outcome than the absolute dose of radiation per
se40,41.
Although the total dose of radiation (>6000 cGy to the prostate) for our
patients was higher than that received by patients in the previous hip
arthroplasty studies, both the number of fractions and the elapsed days were
longer than those in any other reported
groups6-9.
Despite the favorable outcomes, our study has certain limitations. First,
this was a retrospective study with all of the inherent limitations of such a
study design related to the uniformity of data collection. Second, the
follow-up in this study is relatively short for an arthroplasty outcome
report, thus limiting any conclusions that can be drawn regarding the ultimate
survivorship of the prosthesis in this cohort. However, these early results
are encouraging because the majority of arthroplasty component failures in
patients who have had pelvic irradiation occur
early9.
The purpose of this study was to evaluate the osseointegration potential of
uncemented arthroplasty components in patients receiving irradiation for the
treatment of prostate cancer. As bone ingrowth is a process that occurs during
the early months following the implantation of components, we are confident
that biological fixation of the uncemented components used in this cohort was
not compromised even with the short follow-up.
In conclusion, this study on a homogeneous and relatively large group of
patients is the first, to our knowledge, to describe a satisfactory outcome
for uncemented total hip arthroplasty in patients with prostate cancer and a
previously irradiated pelvis. On the basis of these observations, we continue
to advocate the use of uncemented total hip arthroplasty for patients with
prostate cancer and a history of pelvic irradiation, especially when the
current technique of intensity modulated radiation therapy is used. Careful
preoperative medical optimization, meticulous surgical techniques to obtain
secure initial fixation, and diligent postoperative surveillance continue to
be part of our strategy for minimizing complications in these patients.
?