Comparison of trabecular metal cups and titanium fiber-mesh cups in primary hip arthroplasty

Abstract

Background Trabecular metal has shown promising results in experimental studies of bone ingrowth. Several clinical studies support these results. However, until now, no randomized clinical radiostereometric analysis (RSA) studies have been published. In this randomized RSA trial, we compared a new acetabular cup with a surface made of tantalum trabecular metal and a cup with a titanium fiber-mesh surface.Patients and methods Between 2004 and 2006, we operated 60 patients with noninflammatory hip arthritis. The patients were randomized to receive either an uncemented cup with a titanium fiber-mesh surface (Trilogy cup) or a cup with a trabecular tantalum surface (Monoblock cup). After 2 years, 50 patients had completed the study. The primary endpoint was cup migration within the first 2 years after surgery; the secondary endpoints were change in bone mineral density and Harris hip score at 3 months.Results Both cup types showed excellent fixation. RSA revealed minimal translation and rotation at 2 years. There was no statistically significant difference between the cup types with regard to translation. However, less rotation along the transverse axis was seen in the trabecular metal cups than in the fiber mesh cups: mean –0.01º (95% CI: –0.11 to 0.12) for trabecular metal cups and –0.60º (–0.72 to –0.48) for fiber-mesh cups (p = 0.04). The degree of periprosthetic bone loss was similar between the cup types in any of the regions of interest at 2 years of follow-up. 3 months postoperatively, we found a similar increase in Harris hip score in both groups: from around 50 to over 90.Interpretation We found promising early results concerning fixation of trabecular metal components to the acetabular host bone. However, we recommend a longer observation period to evaluate the outcome of this new cup design.

Do Monoblock Cups Improve Survivorship, Decrease Wear, or Reduce Osteolysis in Uncemented Total Hip Arthroplasty?

“…Furthermore, in the randomized controlled trial between the monoblock Trabecular Metal (Zimmer, Warsaw, IN, USA) cup and the modular Trilogy (Zimmer) cup, radiostereometric analysis, no significant differences in migration were found with regard to translation at 2 years followup. However, the monoblock cup showed significantly less rotation along the transverse axis at 2 years followup [3]. Table 2.…”

“…The fact that the best evidence of controlled trials showed no difference in migration between monoblock and [8] modular cups could predict that long-term survival will not be different. In one of the primary studies, a monoblock cup showed significantly less rotation along the transverse axis compared with a modular cup at 2 years of followup [3]. However, the clinical implications of this finding are not well documented.…”

“…Best evidence analysis showed no difference in migration between monoblock and modular acetabular components with regard to translation (= migration in the horizontal or vertical plane) [3,18]. Primary stability is the prerequisite for osseous in-and ongrowth, which is necessary to achieve long-term fixation in uncemented THA [31].…”

“…Therefore, locking mechanisms and dome holes are absent in monoblock acetabular components. These characteristics provide them with various advantages such as optimal liner-shell conformity, thicker polyethylene, and the elimination of liner-shell micromotion thereby eliminating the risk of backside wear [3,39]. Furthermore, the absence of dome holes prevents the possibility of polyethylene wear debris particles to directly access the subchondral bone, thereby eliminating the associated risk of acetabular osteolysis [13].…”

Acetabular Component Thickness Does Not Affect Mid-term Clinical Results in Hip Resurfacing

“…With similar clinical outcomes at 5-years minimum followup, comparable metal ion concentrations, and 7-year survivorship, there is no reason to abstain from using the 3.5-mm thick acetabular component. Excellent results of ultraporous trabecular-like acetabular component backing (made of titanium or tantalum) have been reported [7,20] for conventional THAs and open the way for additional improvement of cementless fixation of hip resurfacing devices.…”