Dual-Modular Versus Single-Modular Stems for Primary Total Hip Arthroplasty: A Long-Term Survival Analysis

Abstract

Background and Objectives: Increased revision rate of dual-modular (DM) femoral stems in primary total hip arthroplasty (THA) because of modular-neck breakage and adverse local tissue reactions (ALTRs) to additional junction damage products is well established and some designs have been recalled from the market. However, some long-term studies of specific DM stems did not confirm the inferiority of these stems compared to standard single-modular (SM) stems, and a head-to-head comparison THA is missing. The objectives of this multicentre study were to determine the survivorship and complication rates of a common DM stem design compared to a similar SM stem. Materials and Methods: In a time frame from January 2012 to November 2015, a cohort of 807 patients (882 hips) consecutively underwent primary cementless THAs at two orthopaedic centres. 377 hips were treated with a Zweimüller-type DM stem THA system and 505 hips with a similar SM stem THA system, both including a modern press-fit acetabulum. Kaplan-Meier survivorship and complication rates were compared between both groups in a median follow-up of 9.0 years (maximum, 9.9 years). Results: The 9-year survivorship of the DM stem THA system (92.6%, 95% CI 89.9–95.3) was significantly lower than that of the SM stem THA system (97.0%, 95% CI 95.2–98.8). There were no differences in revision rates for septic loosening, dislocation, and periprosthetic fractures between the two groups. One ceramic inlay and one Ti-alloy modular neck breakage occurred in the DM stem THA system group, but the main reason for revision in this group was aseptic loosening of components. Conclusions: The survivorship of the DM stem THA system was lower than the similar SM stem THA system in a comparable clinical environment with long-term follow-up. Our results confirmed that no rationale for stem modularity exists in primary THAs.

Is There Safety Outside the “Safe Zone” in Total Hip Replacement? A Retrospective Observational Study

“…Other reports clearly show an increased revision rate in dual mobility implants and significantly lower survival, being one of the essential parameters in modern hip alloplasty. Despite the fact that modular stems could be a good option in the case of severe deformities or hip dysplasia, they are rather avoided in primary THA [30]. Our team also support this statement, so the implants used in our research were not modular.…”

Mechanisms of Premature Fracture in Modular Neck Stems Made of CoCrMo/Ti6Al4V and Ti6Al4V/Ti6Al4V Alloy

“…The recent literature data on survivorship of the modular neck stem THA system confirm a lower yield than the similar mono-block stem THA system in a comparable clinical environment with long-term follow-up [28][29][30][31][32][33].…”

Evaluation of Rotational Stability and Stress Shielding of a Stem Optimized for Hip Replacements—A Finite Element Study

“…According to Wolff's law, [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] bone remodeling occurs to adapt bone structure and geometry to loads acting from the outside. Before the implant is inserted into the femur, all the load is discharged along the bone surfaces, and after the insertion of the prosthesis, the bone is found to be subjected to lower stresses.…”