Comparative Study of Clinical and Radiological Outcomes of Unconstrained Bicondylar Total Knee Endoprostheses with Anti-allergic Coating

Abstract

Background: Hypersensitivity reactions to implant materials have become more important in total knee replacement (TKR). The purpose of this retrospective comparative study was to evaluate the clinical and radiological outcomes of unconstrained bicondylar total knee prostheses with and without anti-allergic titanium(niobium)nitrite (Ti(Nb)N) coating.

Methods: Twenty-four patients (25 TKRs) underwent a preoperative clinical evaluation and then a postoperative evaluation after 26.2 months in the allergy group treated with coated implants (n=13 implants) and after 24.5 months in the control group treated with uncoated implants but identical geometry (n=12) using HSS, WOMAC and SF-36 scores. Radiological evaluations were performed using standard anterior-posterior (a.p.) and lateral X-rays.

Results: During follow-up two patients of the allergy group had to undergo revision surgery due to non-implant-related reasons. A comparative analysis of both study groups showed a significant difference in the HSS scores at both evaluation time points (MW test p≤0.050); these findings are remarkable since the control group had a significantly lower score preoperatively (54.0 vs 65.0 points) and a significantly higher score (82.5 vs 75.0 points) postoperatively. The preoperative and postoperative WOMAC and SF-36 scores were comparable in both groups (MW test p≥0.052), although the postoperative increase in the score for the allergy group was lower. The radiological results were comparable in both groups and were unlikely to influence the results.

Conclusions: This clinical study demonstrates the restricted outcome in postoperative function and quality of life in the allergy group compared to the control group.

Keywords: Allergy; bicondylar surface replacement; functional outcome; implant materials; radiological outcome; total knee replacement..

Fig. (1)

Histological analysis (haematoxylin and eosin staining) of adhesion tissue in a proximal recess obtained from the knee joint three months after implantation of a total knee endoprosthesis made of a cobalt-chromium alloy with a proven sensitization to nickel(II)- sulphate. Excessive lymphoplasmacellular fibrinous infiltration was found as part of type IV neosynovialitis, according to the consensus classification [10] (courtesy of the Department of Pathology, University of Rostock).

Fig. (2)

X-rays (anterior-posterior and lateral) of the knee joint of a 73-year-old female patient 25 months after implantation of a cement-free Genia^® total knee replacement (left) with an anti-allergic (Ti(Nb)N) coating, as well as X-rays of a 55-year-old male patient 24 months after implantation of a cemented Genia^® total knee replacement made of a cobalt-chromium alloy (right). No radiolucent lines were detected around the components in either of these cases. In the lateral view of the total knee replacement with the anti-allergic coating, a gap is visible in femoral zone 1, which is caused by discrete over-dimensioning with flexed positioning of the component.