Background: Debris displaced from the articular and backside
surfaces of the polyethylene inserts of modular tibial components is
considered a chief cause of osteolysis at the sites of total knee
arthroplasties. One design of total knee replacement featured changes, over
time, in the proximal surface roughness of the tibial baseplate and the method
of sterilization of the polyethylene insert. We hypothesized that polishing
the baseplate surface and sterilizing the insert with means other than gamma
radiation in air had reduced the prevalence of osteolysis.
Methods: Three hundred and sixty-five posterior cruciate
ligament-retaining Anatomic Modular Knee primary total knee arthroplasties
were performed in 300 patients from 1987 to 1998. Anteroposterior and lateral
radiographs of the knees were made within a five to ten-year postoperative
interval. Two arthroplasty specialists independently examined the radiographs
for evidence of osteolysis (defined as any nonlinear region of cancellous bone
loss with delineable margins).
Results: Osteolysis was identified in 34% (eighty-two) of 242 knees
treated with an insert that had been gamma-irradiated in air and affixed to a
rough baseplate surface, and it was identified in 9% (nine) of ninety-eight
knees treated with an insert that had been gamma-irradiated in an inert gas,
or had not been irradiated, and joined to a polished surface. Osteolysis was
associated with six factors, including one related to the patient (male
gender), one related to the tibial baseplate (the proximal surface finish),
three related to the polyethylene insert (the material from which it was
machined, the sterilization method, and the shelf age), and one related to the
technique (hyperextension of the femoral component relative to the tibial
Conclusions: In this design of a total knee prosthesis, polishing
the tibial baseplate counterface and implementing a more contemporary
sterilization practice (as opposed to gamma radiation in air) noticeably
diminished but did not eliminate osteolysis.
Level of Evidence: Therapeutic Level III. See
Instructions to Authors for a complete description of levels of evidence.