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

Abstract

Background Monoblock acetabular components used in uncemented total hip arthroplasty (THA) have certain mechanical characteristics that potentially reduce acetabular osteolysis and polyethylene wear. However, the degree to which they achieve this goal is not well documented. Questions/purposes The purpose of this study was to use a systematic review of controlled trials to test the hypothesis that monoblock cups have superior (1) polyethylene wear rate; (2) frequency of cup migration; (3) frequency of acetabular osteolysis; and (4) frequency of aseptic loosening compared with modular components used in uncemented THA.Methods A systematic search was conducted in the Medline, Embase, and Cochrane electronic databases to assemble all controlled trials comparing monoblock with modular uncemented acetabular components in primary THA. Included studies were considered ''best evidence'' if the quality score was either C 50% on the Cochrane Back Review Group checklist or C 75% the Newcastle-Ottawa quality assessment scale. A total of seven publications met our inclusion criteria. Results Best evidence analysis showed no difference in polyethylene wear rate, the frequency of cup migration, and aseptic loosening between monoblock and modular acetabular components. No convincing evidence was found for the claim that lower frequencies of acetabular osteolysis are observed with the use of monoblock cups compared with modular uncemented cups. Conclusions The purported benefits of monoblock cups were not substantiated by this systematic review of controlled studies in that polyethylene wear rates and frequencies of cup failure and acetabular osteolysis were similar to those observed with modular implants. Other factors should therefore drive implant selection in cementless THA. Level of Evidence Level III, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Backside Wear Analysis of Retrieved Acetabular Liners with a Press-Fit Locking Mechanism in Comparison to Wear Simulation In Vitro

“…Insufficient locking mechanism, the amount of micromotion, and the metal surface finish have been well accepted factors for backside wear [ 14 ]. Several studies have shown that suboptimal conformity between the shell and the liner could be the major influence factor on liner instability causing backside wear and subsequent osteolysis [ 3 , 12 , 14 , 16 ]. The reason for this is that synovial fluid with debris particles from the articulation surface could occupy this empty backside space and a piston pumping mechanism generated during gait could push the debris solution into the iliac bone through the screw holes and create osteolysis [ 10 , 16 ].…”

“…Moreover, the so-called “monoblock” cups, whose polyethylene liners and cups are factory-preassembled into a single solid construct, theoretically eliminate backside wear of polyethylene liners. Nevertheless, a systematic review performed by Halma et al [ 3 ] as well as a study by González Della Valle et al [ 38 ] showed that there was no difference in the polyethylene wear rate between monoblock and modular acetabular components at intermediate-term follow-up.…”

“…Aseptic loosening of the implant is the main reason for revision in total hip arthroplasty (THA), with over 50% of the cases [ 1 – 3 ]. The main stimulator of periprosthetic osteolysis and subsequent aseptic loosening is the particulate debris generated by the wear at the articulating surface between the acetabular polyethylene liners and the femoral heads [ 2 , 4 – 6 ].…”

How Have Alternative Bearings and Modularity Affected Revision Rates in Total Hip Arthroplasty?

“…Insufficient data were available on alternative polymers (eg, polyetheretherketone [PEEK]), metal-on-ceramic and ceramic-on-metal implants, and monoblock acetabular designs, which were evaluated in other recent systematic reviews [31,83], so these were not evaluated here. Study quality was specified by listing the level of evidence for each of the studies included in the systematic review.…”

Raloxifene Prevents Early Periprosthetic Bone Loss for Postmenopausal Women after Uncemented Total Hip Arthroplasty: A Randomized Placebo‐Controlled Clinical Trial

“…T otal hip arthroplasty (THA) can restore hip function to significantly improve the quality of life (QoL) 1,2 . More than 230,000 patients in the United States alone and approximately 500,000 patients worldwide undergo THA surgery every year 3 . These figures increase by approximately 10% per year 4,5 .…”