Osteolysis associated with a cemented modular posterior-cruciate-substituting total knee design : five to eight-year follow-up.

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 degrees (range, 90 degrees to 130 degrees ) 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.