We previously described the minimum nine-year results after total
knee arthroplasty with the cemented LCS (low contact stress) rotating-platform
design (DePuy, Warsaw, Indiana) in a cohort of eighty-six patients (119
knees)1. In that
study, we reported on a prospective consecutive series of selected patients
who were treated for osteoarthritis by a single surgeon. All patients who were
deemed to require a total knee arthroplasty between 1985 and 1988 received the
cemented LCS rotating-platform tibial and femoral implants mated with a
cemented Townley all-polyethylene dome patellar component
(Fig. 1). During the same
time-period, seventy-five unicompartmental knee arthroplasties were performed
in selected patients.
At the time of the previous
report1, no revision
had been performed and no knee had aseptic loosening of a component. Of the
sixty-four patients (eighty-six knees) who were alive at the time of the
nine-year follow-up, forty-five (70%; sixty-six knees) returned for
radiographic evaluation. The average clinical and functional Knee Society
scores had improved from 30 and 44 points, preoperatively, to 90 and 75
points. The average range of motion of the knee was 0° of extension to
102° of flexion. There were no complications of bearing dislocation or
so-called spin-out.
The purpose of this study was to provide the longer-term results of this
cohort at a minimum follow-up of fifteen years with an emphasis on the rates
of revision, reoperation, and osteolysis.
The original study cohort included eighty-six patients (119 knees)
with an average age of seventy years (range, thirty-seven to eighty-eight
years) at the time of index surgery. Since the time of the original report,
thirty additional patients (thirty-seven knees) died and the four previously
lost patients were found. Thus, the subjects in this update included
thirty-seven patients (fifty-three knees) who were still living and had a mean
age of eighty-one years (range, fifty-nine to ninety-seven years); forty-eight
patients (sixty-five knees) who had died; and one patient, who had not had a
revision or reoperation, who refused to participate in the study.
Data on the clinical examination and radiographs made at a minimum of
fifteen years (range, fifteen to eighteen years) postoperatively were
available for thirty-nine knees (74%) in twenty-eight living patients. Of the
twenty-eight patients, eight (twelve knees) had been examined by the authors
and the rest had been examined by physicians at outside institutions. Clinical
outcome questionnaires (the WOMAC) were completed for all thirty-seven living
patients (fifty-three knees). The living patients were followed
radiographically for an average of thirteen years (range, 0.1 to eighteen
years) and the patients who had died had been followed radiographically for an
average of four years (range, 0.1 to eleven years).
The average preoperative Knee Society clinical and functional knee scores
for the living patients were 43 points (range, 17 to 70 points) and 49 points
(range, 30 to 70 points), respectively. At the final clinical examination, the
functional Knee Society scores were 85 points (range, 41 to 99 points) and 58
points (range, 0 to 100 points), respectively. The preoperative and final
follow-up scores on The Hospital for Special Surgery knee-rating system were
61 points (range, 41 to 77 points) and 79 points (range, 56 to 95 points),
respectively. At the final follow-up evaluation, the average scaled WOMAC
score was 21 points (range, 0 to 63 points). At that time, thirty-one knees
were pain-free, six were mildly painful, one was moderately painful, and one
was severely painful.
The average preoperative active range of motion was -7° (range,
-30° to 15°) of extension to 114° (range, 85° to 140°) of
flexion. At the final follow-up examination, the average active range of
motion was -1° (range, -10° to 0°) of extension to 105°
(range, 35° to 125°) of flexion.
Revision or Reoperation
No knee had a revision of an implant. Three knees underwent a reoperation
to treat a supracondylar femoral fracture (two knees) or an infection (one
knee) (Fig. 2). The latter knee
was seen fourteen years after the index surgery because of a late hematogenous
infection (Peptostreptococcus) and was treated successfully with open
débridement, polyethylene exchange, and implant retention. Both
patients with a supracondylar femoral fracture were treated successfully with
open reduction, internal fixation, and retention of the components. The three
knees requiring a reoperation had stable bone-cement interfaces on the final
follow-up radiograph, with no radiolucencies at the bone-cement interface.
Aseptic Loosening
No knee had aseptic loosening of the femoral, tibial, or patellar
component. Zonal analysis of the radiographs of the thirty-nine knees showed
no radiolucencies that were >1 mm thick at the bone-cement interfaces; no
radiolucencies were progressive (see Appendix). No knee had a circumferential
radiolucency around any of the three components, and no component had
migrated. One knee had a healed, nondisplaced asymptomatic patellar
fracture.
Osteolysis or Wear
Three knees had osteolytic lesions (one at the anterior femoral flange [1
cm by 1 cm on the lateral radiograph], one involving the tibia [2.5 cm by 1 cm
on the lateral radiograph and 2 cm by 2 cm on the anteroposterior radiograph],
and one involving the patella [2 cm by 1 cm]). No knee had discernible
asymmetrical wear of the tibial or patellar polyethylene.
Rotating-platform mobile-bearing knee prostheses were designed to
reduce contact stresses in the polyethylene by decoupling sagittal plane
motion and rotation and by minimizing bone-prosthesis stresses at the tibial
surface6-14.
The present study demonstrates the durability of the cemented LCS
rotating-platform mobile-bearing total knee replacement at a minimum follow-up
of fifteen years. These results are comparable with the fifteen-year results
reported for fixed-bearing
devices15-18.
No implant failed secondary to loosening, and no implant had been revised
since the time of the last follow-up. No knee demonstrated instability or had
excessive wear of the polyethylene. The Knee Society clinical and functional
scores deteriorated since the minimum nine-year follow-up study, but we
suggest that these changes are most likely associated with factors related to
the aging of the patients. We observed minimal evidence of osteolysis (only
three small lesions) despite a critical assessment of the radiographs.
This rotating-platform design appears to be safe as well as efficacious in
an older population. This study cannot completely address the long-term
performance of this device with cement fixation in the younger patient as only
three patients were less than fifty years of age at the time of the primary
arthroplasty.
A table presenting the data on the radiolucencies is 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
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