All-polyethylene vs. metal-backed tibial component in total knee arthroplasty—a randomized RSA study comparing early fixation of horizontally and completely cemented tibial components: Part 2. Completely cemented components: MB not superior to AP components

Abstract

Background Uncertainty exists as to whether metal backing (MB) of the tibial component is better than an all-polyethylene component (AP). This is valid for both horizontally and completely cemented components. We evaluated completely cemented MB vs. AP (Part 2).Patients and methods In a randomized study, 39 patients (40 knees) with knee arthrosis were operated with cemented low-conforming total knee arthroplasty (AGC, Biomet) with a tibial component of uniform thickness (8 mm), cemented both beneath the tibial tray and around the stem. 20 patients had an all-polyethylene (AP) tibial component and 20 patients had an identical but metal-backed (MB) tibial component. We used clinical examination and radiostereometric analysis (RSA) to evaluate the hypothesis that MB improves component fixation. Fixation was evaluated using RSA up to 2 years after surgery. Clinical assessment was performed preoperatively and after 2 years using the Hospital for Special Surgeons (HSS) score.Results We found no differences in micromotion, and no differences in clinical scores could be detected between the groups at any time point.Interpretation Our findings indicate that there was equal initial fixation of the AP and MB stemmed monobloc components when they were cemented beneath the tibial plateau and around the stem. ▪