High Initial Stability in Porous Titanium Acetabular Cups: A Biomechanical Study

Joint Replacement Surgeons of Indiana Foundation, Inc., Mooresville, Indiana.
The Journal of arthroplasty (Impact Factor: 2.67). 11/2012; 28(3). DOI: 10.1016/j.arth.2012.07.035
Source: PubMed


Initial stability with limited micromotion in uncemented total hip arthroplasty acetabular components is essential for bony attachment and long-term biomechanical fixation. This study compared porous titanium fixation surfaces to clinically established, plasma-sprayed designs in terms of interface stability and required seating force. Porous plasma-sprayed modular and metal-on-metal (MOM) cups were compared to a modular, porous titanium designs. Cups were implanted into polyurethane blocks with1-mm interference fit and subsequently edge loaded to failure. Porous titanium cups exhibited 23% to 65% improvement in initial stability when compared to plasma-sprayed cup designs (P=.01): a clinically significant increase, based on experience and prior literature. The results of this study indicate increased interface stability in porous titanium-coated cups without significantly increasing the necessary force and energy required for full seating.

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    • "Therefore, the seating forces generated in this study can only be compared with corresponding values estimated from other in vitro studies. Of the few studies that have quantified seating forces with similar press-fit values (0 mm to 2 mm) and substrate densities (0.2 g/cm3 and 0.5 g/cm3), four have reported a range between 1.5 kN and 5 kN with a variety of uncemented implants that included purely hemispherical as well as peripherally enhanced designs.10,11,15,30 The range of seating forces generated in the current study (between 4 kN and 8 kN) is somewhat higher. "
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    ABSTRACT: This study compared the primary stability of two commercially available acetabular components from the same manufacturer, which differ only in geometry; a hemispherical and a peripherally enhanced design (peripheral self-locking (PSL)). The objective was to determine whether altered geometry resulted in better primary stability. Acetabular components were seated with 0.8 mm to 2 mm interference fits in reamed polyethylene bone substrate of two different densities (0.22 g/cm(3) and 0.45 g/cm(3)). The primary stability of each component design was investigated by measuring the peak failure load during uniaxial pull-out and tangential lever-out tests. There was no statistically significant difference in seating force (p = 0.104) or primary stability (pull-out p = 0.171, lever-out p = 0.087) of the two components in the low-density substrate. Similarly, in the high-density substrate, there was no statistically significant difference in the peak pull-out force (p = 0.154) or lever-out moment (p = 0.574) between the designs. However, the PSL component required a significantly higher seating force than the hemispherical cup in the high-density bone analogue (p = 0.006). Higher seating forces associated with the PSL design may result in inadequate seating and increased risk of component malpositioning or acetabular fracture in the intra-operative setting in high-density bone stock. Our results, if translated clinically, suggest that a purely hemispherical geometry may have an advantage over a peripherally enhanced geometry in high density bone stock. Cite this article: Bone Joint Res 2013;2:264-9.
    Full-text · Article · Dec 2013
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    ABSTRACT: Hip instability after total hip replacement has been shown to be a critical cause of failure. The use of dual mobility has been classically restricted to patients "at risk", over 70years of age. The question rises up about extended indications of so-called "modern" second generation dual mobility cups. This prospective multicenter study reports on first results at 2-5years of the HA anatomical ADM cup upon two comparative groups of patients under 70years (112 hips) vs. over 70years of age (325 hips). No dislocation, migration, tilting, wear, or intra-prosthetic dislocation was recorded within each of the two cohorts. Survivorship for cup failures at this 4-year period was ideal at 100% in the younger patients, and 99.7% in the older group of patients.
    No preview · Article · Dec 2013 · The Journal of arthroplasty
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    ABSTRACT: The principle of dual mobility cups, often called "tripolar", has been developed to overcome the problem of instability following primary hip arthroplasty. We prospectively compared two cohorts which differed only by the type of bearings, i.e." mobile bearing hip" (MBH) in a 143 hips study cohort of ADM cups versus "fixed bearing hip" (FBH) of 130 Trident PSL cups, at a follow-up at 2–6 years. The survival rates at 4.13-year, with instability as endpoint was significantly (p = 0.0176) in favor of mobile bearings at 100% with no dislocation reported, versus 94.8% with fixed bearings. These mobile bearings, matching both "modern" dual mobility cups and annealed highly crossed polyethylene, would appear to offer at longer follow-up a valuable solution to clinical outcomes in acetabular replacement.
    No preview · Article · Oct 2014 · The Journal of Arthroplasty
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