Trabecular metal in total knee arthroplasty associated with higher knee scores: a randomized controlled trial

Abstract

Background: Porous tantalum is an option of cementless fixation for TKA, but there is no randomized comparison with a cemented implant in a mid-term followup.

Questions/purposes: We asked whether a tibial component fixed by a porous tantalum system might achieve (1) better clinical outcome as reflected by the Knee Society Score (KSS) and WOMAC Osteoarthritis Index, (2) fewer complications and reoperations, and (3) improved radiographic results with respect to aseptic loosening compared with a conventional cemented implant.

Methods: We randomized 145 patients into two groups, either a porous tantalum cementless tibial component group (Group 1) or cemented conventional tibial component in posterior cruciate retaining TKA group (Group 2). Patients were evaluated preoperatively and 15 days, 6 months, and 5 years after surgery, using the KSS and the WOMAC index. Complications, reoperations, and radiographic failures were tallied.

Results: At 5-year followup the KSS mean was 90.4 (range, 68-100; 95% CI, ± 1.6) for Group 1, and 86.5 (range, 56-99; 95% CI, ± 2.4) for Group 2. The effect size, at 95% CI for the difference between means, was 3.88 ± 2.87. The WOMAC mean was 15.1 (range, 0-51; 95% CI, ± 2.6) for the Group 1, and 19.1 (range, 4-61; 95% CI, ± 2.9) for Group 2. The effect size for WOMAC was -4.0 ± 3.9. There were no differences in the frequency of complications or in aseptic loosening between the two groups.

Conclusions: Our data suggest there are small differences between the uncemented porous tantalum tibial component and the conventional cemented tibial component. It currently is undetermined whether the differences outweigh the cost of the implant and the results of their long-term performance.

Fig. 1

The CONSORT flow diagram shows the progression of the study through patients’ enrollment, allocation, followup, and analysis at the end point. PS = posterior stabilized.

Fig. 2A–D

Radiolucencies were analyzed following the KS criteria [26] and the modification proposed for uncemented pegged tibial components [66]. (A) The implant-bone interface zones are shown in this AP view of a stemmed cemented tibial component used in our study. (B) The zones are shown in this lateral view of the stemmed cemented tibial component. (C) The implant-bone interface zones are shown in the AP view of the uncemented tibial component used our study. (D) The implant-bone interface zones are shown in this lateral view of the uncemented tibial component.