Background:
Most intermediate and long-term studies of cemented posterior-cruciate-substituting
total knee prostheses were performed with nonmodular tibial components.
The purpose of this study was to evaluate the intermediate-term
results of posterior-cruciate-substituting total knee arthroplasties
in which a cemented modular tibial component had been used, with
a particular focus on evaluating the prevalence of radiographic
osteolysis.
Methods:
Between 1992 and 1995, 176 consecutive primary total knee arthroplasties
with use of the Insall-Burstein II system were performed in 134
patients at our institution. A modular metal-backed tibial component
was inserted in 145 knees, and an all-polyethylene tibial component
of the same design was inserted in thirty-one. Standard-terminology
questionnaires were completed or Knee Society and The Hospital for
Special Surgery scores were determined preoperatively and at the time
of final follow-up, at an average of 6.4 years (range, 5.0 to 7.9
years). Initial postoperative radiographs were compared with those
made at the time of final follow-up to assess component position,
wear, radiolucent lines, and osteolysis.
Results:
Ninety-two patients (128 knees) treated with the modular tibial
component were alive at the time of final follow-up. No patient
was lost to follow-up. Radiographs were available for 105 knees
(82%). Three knees had been revised because of instability or infection;
none had been revised because of loosening or osteolysis. The mean
Knee Society clinical and functional scores were 85 points (range,
41 to 100 points) and 79 points (range, 30 to 100 points), respectively,
at the time of final follow-up. According to The Hospital for Special
Surgery score, 94% of the knees had a good or excellent result. Knee
flexion averaged 113° (range, 90° to 130°)
at the time of final follow-up. Osteolysis was present in seventeen
(16%) of the knees with radiographic follow-up. Osteolysis did not
develop in any knee in which an all-polyethylene tibial component
had been used. Two knees (in one patient) were revised because of
osteolytic lesions found at the time of follow-up for the study.
Both of these knees had anterior wear of the tibial post due to
impingement and backside tibial polyethylene wear.
Conclusions:
Modular Insall-Burstein II total knee prostheses were found to
function well after five to eight years of follow-up. However, the
high prevalence of osteolysis in patients who had good or excellent
clinical scores is worrisome. Particular attention should be paid
to preventing flexion of the femoral component, posterior slope
of the tibial component, or hyperextension of the knee when posterior-cruciate-substituting total
knee arthroplasty is performed. We also recommend routine follow-up
radiographs after all total joint arthroplasties to detect asymptomatic
osteolytic changes.