Abstract
PurposeConcerns remain about potential increased wear with dual mobility cups related to the multiple articulations involved in this specific design of implant. This finite element analysis study aimed to compare polyethylene (PE) wear between dual mobility cup and conventional acetabular component, and between the use of conventional ultra-high molecular weight PE (UHMWPE) and highly cross-linked PE (XPLE).MethodsPatient-specific finite element modeling was developed for 15 patients undergoing primary total hip arthroplasty (THA). Five acetabular components were 3D modeled and compared in THA constructs replicating existing implants: a dual mobility cup with a 22.2-mm-diameter femoral head against UHMWPE or XLPE (DM22PE or DM22XL), a conventional cup with a 22.2-mm-diameter femoral head against UHMWPE (SD22PE) and a conventional cup with a 32-mm-diameter femoral head against UHMWPE or XLPE (SD32PE or SD32XL).ResultsDM22PE produced 4.6 times and 5.1 times more volumetric wear than SD32XL and DM22XL (p < 0.0001, Cohen’s d = 6.97 and 7.11; respectively). However, even if significant, the differences in volumetric wear between DM22XL and SD32XL as well as between DM22PE and SD22PE or SD32PE were small according to their effect size (p < 0.0001, Cohen’s |d|= 0.48 to 0.65) and could be therefore considered as clinically negligible.ConclusionWhen using XLPE instead of UHMWPE, dual mobility cup with a 22.2-mm-diameter femoral head produced a similar amount of volumetric wear than conventional acetabular component with a 32-mm-diameter femoral head against XLPE. Therefore, XLPE is advocated in dual mobility cup to improve its wear performance.
Highlights
Dual mobility cups demonstrate a marked increase in use to achieve hip stability during primary and revision total hip arthroplasty (THA), concerns remain about potential increased wear related to the multiple articulations involved in this specific design of implant [1,2,3,4]
Reports on the long-term wear in vivo of recent designs of dual mobility cup are sparse in literature, previous clinical and laboratory studies suggest that wear of dual mobility cup compared favorably with conventional PE bearings with large heads routinely used in THA [1,2,3]
Adam et al and Geringer et al [10, 11] both demonstrated a volumetric wear rate of 54 mm3/year in dual mobility cup mobile components made of ultra-high molecular weight PE (UHMWPE) that was higher than the rate of 24 m m3 we observed in our numerical study after a simulated one year of level walking
Summary
Dual mobility cups demonstrate a marked increase in use to achieve hip stability during primary and revision total hip arthroplasty (THA), concerns remain about potential increased wear related to the multiple articulations involved in this specific design of implant [1,2,3,4]. Biomechanical studies using hip simulator with gravimetric measurement usually do not consider parameters such as patient’s level of activity and hip anatomy, body mass index (BMI) or variation in implant positioning related to surgeon’s experience [6,7,8] Another limitation of these ex vivo studies is related to their ability to determine the exact parts played in wear by the small and large articulations [6,7,8,9,10,11]. In previous studies [12,13,14], we developed patient-specific modeling of the hip using finite element analysis (FEA) to simulate the in vivo biomechanical functioning of THA that enables simulation and evaluation of wear of dual mobility and conventional cups. This FEA study aimed to evaluate and compare PE wear between dual mobility and conventional cups, as well as between the use of conventional ultra-high molecular weight PE (UHMWPE) or highly cross-linked PE (XPLE)
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