Total knee arthroplasty : Alternative aspects on fixation, design and postoperative treatment

Abstract: Total knee arthroplasty as a treatment of severe gonarthrosis has become a great success, but tibial component loosening is still a major reason for failure. When total knee arthroplasty was introduced, only all-polyethylene (AP) tibial components were available. Based on mostly theoretical data, AP components were more or less abandoned during the 1980:ies in favor of metal-backed (MB) tibial components. The aim of the present study was to evaluate whether insufficient fixation would result, using an all-polyethylene tibial component instead of a more costly metal-backed prosthesis. Further, to compare different antibiotic loaded bone cements, and to investigate whether post- operative drainage is beneficial in total knee arthroplasty. Radiostereometric analysis (RSA) was used to obtain accurate and standardized evaluations facilitating comparison between prosthetic designs.Magnitude and pattern of migration of a moderately conforming AP tibial component was analyzed in 22 patients. Migration was on par with a more conforming previously used frequently, AP component, indicating a favorable prognosis regarding future aseptic loosening. Another 34 arthroplasties with a flat on flat (non-conforming) articulating geometry were randomized to an AP or MB cemented tibial component. There were no differences in migration between the groups. None of the AP implants displayed any continuous migration between 1 and 2 years postoperative. In a similar randomized series of 38 arthroplasties with a semiconstrained articulation, fixation measured with RSA was not inferior for AP implants compared with MB. Both studies indicate a good long-term prognosis using an AP component. A new antibiotic loaded bone cement was prospectively randomized against a more commonly used bone cement in a series of 51 arthroplasties. Neither fixation of the tibial component nor the radiographic and clinical results differed between the cements, indicating a good prognosis for the new cement. Postoperative drainage of knee arthroplasty is widely used. 90 patients were prospectively randomized into three groups: no drain, ordinary drain system and a retransfusable drain system. Postoperative drainage in knee arthroplasty has no adverse clinical consequences but seems not to be necessary.