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Primary Cementless Acetabular Reconstruction: HGP at Average ELEVEN-YEAR Follow-up Aaron G. Rosenberg, M.D. Professor of Orthopaedic Surgery Arthritis
& Orthopaedic Institute Rush
Medical College Rush-Presbyterian
–St. Luke Medical Center Chicago,
Illinois A prospective review of 204 primary total
hip arthroplasties in 184 patients.
In all patients, a cementless, hemispherical, porous-coated acetabular
component (Harris/Galante I, Zimmer, Inc.) was inserted. All surgeries were performed between May
1984 and December 1985 by four surgeons at Rush-Presbyterian-St. Luke's Medical Center. During the study period, twenty-seven
patients with thirty hips died prior to ninety-two month follow-up and seven
patients with seven hips were lost to follow-up leaving 150 patients with 167
hips available for review. Of these,
eight patients with ten hips were unable to obtain radiographic follow-up,
though telephone interview established that these acetabular components
remained in place. The study group consisted of 102 females
(55%) and eighty-two males (45%) with an average age at time of surgery of
fifty-two years (twenty to eighty-four years). Preoperative diagnosis was osteoarthritis in 109 hips (63%),
avascular necrosis in forty-three hips (25%), rheumatoid arthritis in eleven
hips (6%), ankylosing spondylitis in five hips (3%), post-traumatic arthritis
in four hips (2%), and acute femoral fracture in two (1%). 165 hips (81%)
were reconstructed using cementless femoral components (151 Harris/Galante
stems and fourteen Gustillo/Kyle stems) and thirty-nine (19%) were
reconstructed using cemented femoral components (Precoat). All cementless, porous-coated acetabular
components were inserted after line-to-line reaming of the acetabulum. Three to five intracortical screws were
used to supplement fixation. Radiographic analysis consisted of
qualitative evaluation of radiographs for interface radiolucencies,
migration, osteolysis, screw lucency, screw breakage and fragmentation of the
porous coating. The acetabulum was
divided into five zones in a method modified from that of DeLee and
Charnley. Additionally, a qualitative
evaluation was performed using a Sigma Scan digitizing system (Jandel
Scientific, San Rafael, CA) to measure changes in component position. Initial
six-week anteroposterior radiographs were compared to those obtained at
yearly intervals and at final follow-up.
Components demonstrating a change of position of two degrees or more were
considered unstable. Those with a radiolucency
in at least 4 of five zones, with at least one zone greater than 2 mm were
considered probably unstable. Postoperative complications were
infrequent. Of the 204 hips
comprising the study group, three patients (three hips) experienced a post-operative
dislocation (1.5%), two patients (two hips) had a superficial wound infection
(1.0%), two patients (two hips) had late hematogenous infection of the hip
(1.0%), one patient (one hip) experienced a temporary nerve palsy (0.5%), and
one patient (one hip) had a deep vein thrombosis (0.5%). Two patients (two
hips) died in the peri-operative period: one patient with chronic liver
disease who died two weeks post-operatively due to operative procedure due to
electrolyte imbalance (1.3%) and one patient who died within the first week
post-operatively due to a major pulmonary embolism. 167 patients (150 hips) were available for
clinical review at mean 132 month follow-up (range ninety-two to 171
months). Four stable acetabular
components (2.4%) required revision.
One stable component (0.6%) was revised at 13 months for recurrent
dislocation following revision of the femoral component and another stable
component (0.6%) was revised at 138 months when a liner dissociation was
discovered at the time of revision for femoral loosening. The remaining two acetabular components
(1.2%) were revised for acetabular osteolysis. One component was revised at 123 months since retroacetabular
osteolysis was discovered at the time of femoral revision. A second acetabular component was revised
at 127 months for progressive retroacetabular osteolysis which was recognized
on serial radiographs. Seven other hips (4.2%) required
re-operation for problems related to the acetabulum in which the acetabular
component was retained. In five asymptomatic patients with five hips (3.0%),
the polyethylene liner of the acetabular component was removed and exchanged
due to excessive liner wear at average 117 months (range, 84-142 months). Two hips (1.2%) underwent debridement and
grafting of progressive osteolytic lesions along with liner exchange at
average 111 months (range, 89-132 months). Thirty-five other re-operations were
performed for reasons which were unrelated to the acetabular component
(21%). Twenty-eight femoral
components were revised without acetabular revision (16.8%). Three hips
required excision of extensive heterotopic bone (1.8%). One hip required
incision and drainage for a late hematogenous infection (0.6%). One hip required
incision and drainage of a superficial wound infection (0.6%). One hip
underwent evacuation of a hematoma in the early post-operative period (0.6%).
One hip underwent ORIF of a late periprosthetic fracture (0.6%). The mean preoperative Harris hip score of
fifty-two (range, fourteen to seventy-seven) improved to eighty-eight (range,
forty-four to 100) at final follow-up. 140 (83.8%) had a good or excellent
result (eighty to 100 points), eleven (6.6%) had a fair result (seventy to
seventy-nine points), and sixteen (9.6%) were rated poor (less than seventy
points). All patients with poor
scores had pain and/or disability explained by femoral component problems,
medical conditions, or other musculoskeletal abnormalities. Radiographs of 142 patients with 157 hips
were reviewed at mean 128 month follow-up (range, 92 - 171 months). 148
acetabular components (94.3%) were considered stable. Seven hips showed a radiolucency of less
than two millimeters in four of five zones and were judged "possibly
unstable" (4.5%). Of these, one hip had a continuous radioluceny. Two acetabular components were judged to
be unstable (1.3%). One acetabular component migrated within the first
twenty-four months due to resorption of a bulk femoral head graft. The second unstable acetabular component
demonstrated late migration in association with progressive osteolysis. The incidence of a radiolucent line of <
1 mm was common: 29.9% in zone A1; 23.6% in zone A2; 7.0% in zone B1; 12.1 %
in zone B2; and 21.0% in zone C. A single cup displayed a radiolucent line
< 1 mm but < 2 mm in zone C. No radiolucent lines >2 mm were
seen. Osteolysis of the acetabulum was seen in
twenty-three hips (14.6%). Twenty acetabuli (12.7%) showed limited lysis at
the peripheral interfaces of the cup or of the adjacent pelvic bone. Three acetabuli (1.9%) demonstrated
retroacetabular lysis at mean ninety-two month follow-up. Of these, two acetabular components went
on to acetabular revision, and one acetabular component was retained with
debridement and grafting of the lesion. Peripheral fragmentation of the porous
coating was seen in three cups (1.9%). A lucent line was seen around three
screws in three hips (1.8%). No screw breakage or complications related to
intrapelvic screw penetration was seen. Measurement of polyethylene liner wear using
a modification of the Livermore technique (which included the use of a
digitizing tablet) showed an average total linear wear rate of 1.52mm at
final follow-up and an average wear rate of 0.15mm/year. Patient's less than
fifty years of age at time of surgery demonstrated an average total linear
wear rate of 1.82 mm and an average wear rate of 0.18 mm/yr as compared to
those greater than or equal to fifty years at time of surgery, who had an
average total linear wear rate of 1.3 mm and an average wear rate of 0.12
mm/yr. An analysis of the radiographs of patients
with final follow-up less than ninety-two months, showed no osteolysis of the
acetabular and no cups with a complete radiolucency. One patient with a renal transplant and
metabolic bone disease had one acetabular component which migrated in
conjunction with a pelvic fracture. Kaplan-Meier survivorship analysis for
revision of the acetabular component revealed a 97.7% chance of acetabular
component survival at mean eleven years (95% confidence limit, 0.99 - 0.96).
Kaplan-Meier survivorship analysis for revision or migration of the
acetabular component or re-operation related to the acetabulum revealed a
93.5% chance of acetabular component survival at mean eleven years (95%
confidence limit, 0.96 - 0.92). The cementless, hemispherical porous-coated acetabular component reported on in this study for primary acetabular reconstruction showed acceptable results at intermediate term follow-up. There was one case of aseptic loosening in the presence of peripheral osteolysis. Radiolucencies between the bone prosthesis interface were infrequent. As anticipated, the incidence of osteolysis of the acetabulum and extensive polyethylene liner wear has increased with time and is responsible for most late re-operations related to the acetabular component. Since many problems related to particulate debris can be expected to occur only at longer intervals, further follow-up is needed to ascertain long-term outcomes in this relatively young patient population.  |
