Description
Background: Backside wear of the polyethylene insert in total knee arthroplasty (TKA) has been described to produce clinically significant levels of polyethylene debris, which can lead to aseptic loosening of the tibia components. Monoblock design eliminates backside wear of the polyethylene and therefore could improve longterm implant fixation. This randomized trial compares monoblock to modular polyethylene inserts with 7 years follow up including Radiostereometric Analysis (RSA) data.Aim: To compared monoblock and modular cementless TKA designs in a randomized clinical trial with RSA data, clinical outcome and longterm follow-up.
Materials and Methods: : 65 patients (mean age 61 years) were randomized to receive either monobloc (n=33) or modular (n=34) cementless Zimmer Nexgen (TMT) tibia component and a cementless CR- Flex Porous Femoral Component. 35 patients (monoblok=18) (modular=17) completed 7 years follow-up. RSA and clinical outcome score was done postoperatively after weight bearing and after 3, 6, 12, and 24 months. The primary endpoint of the study was comparison of the tibial component migration (maximum total point motion (MTPM)) of the 2 different implant designs.
Results: There was no statistically significant difference in MTPM between the groups at 3 months (p = 0.2) or at 6 months (p = 0.1), but at 12, 24 and 84 months of follow-up there was a significant difference in MTPM of 0.36 mm (p = 0.02), 0.42 mm (p = 0.02) and 39 mm (p=0.02) between groups, with the highest average amount of migration 1.17 (.39-2.0) mm in the modular group. Continuous migration (from 12-84 months) was 0.13 mm in the monoblock group and 0.16 mm and in modular groups with no statistically significant difference (0.45). The largest translational and rotational migrations were a subsidence and a posteriorly tilt.
Interpretation / Conclusion: In this study group we did not detect a significantly different continuous migration for cementless monoblock tibia design when compared to modular design. The difference in initial migration between the groups, we believe should not be attributed to the elimination of backside wear in the monoblock design group.
| Period | 2023 |
|---|---|
| Event title | Dansk Ortopædisk Selskab Kongres 2023 |
| Event type | Conference |