Dual Modular Titanium Alloy Femoral Stem Failure Mechanisms and Suggested Clinical Approaches

Jan Zajc,Samo Karl Fokter,Andrej Moličnik

doi:10.3390/ma14113078

Abstract

Titanium (Ti) alloys have been proven to be one of the most suitable materials for orthopaedic implants. Dual modular stems have been introduced to primary total hip arthroplasty (THA) to enable better control of the femoral offset, leg length, and hip stability. This systematic review highlights information acquired for dual modular Ti stem complications published in the last 12 years and offers a conclusive discussion of the gathered knowledge. Articles referring to dual modular stem usage, survivorship, and complications in English were searched from 2009 to the present day. A qualitative synthesis of literature was carried out, excluding articles referring solely to other types of junctions or problems with cobalt-chromium alloys in detail. In total, 515 records were identified through database searching and 78 journal articles or conference proceedings were found. The reasons for a modular neck fracture of a Ti alloy are multifactorial. Even though dual modular stems have not shown any clinical benefits for patients and have been associated with worse results regarding durability than monolithic stems, some designs are still marketed worldwide. Orthopaedic surgeons should use Ti6Al4V dual modular stem designs for primary THA in special cases only.

Highlights

Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) [6] guidelines, we have systematically reviewed the literature from 2009 onward to identify studies that have evaluated dual modular stem prosthesis survivorship, complications with clinical use, mechanical complications, and biological responses
We have searched through the National Center for Biotechnology Information (NCBI) database (Pubmed) on 1 January 2021, and through the ScienceDirect and Google Scholar databases on 1 April 2021
The following Medical Subject Headings (MeSH) terms were used to search in the NCBI (PubMed) database: “arthroplasty, replacement, hip”, “prostheses and implants”, “hip prosthesis”, “prosthesis failure”, “corrosion”, “adverse effect”, and “long-term adverse effects”

Summary

Introduction

Even though dual modular stems have not shown any clinical benefits for patients and have been associated with worse results regarding durability than monolithic stems, some designs are still marketed worldwide. Orthopaedic surgeons should use Ti6Al4V dual modular stem designs for primary THA in special cases only. In the last 30 years, implants with dual modular stems consisting of a modular (interchangeable) neck that is separate from both the stem and the head have been introduced to improve biomechanical restoration. For the purpose of this manuscript, the term “monoblock” will be used to refer to an implant with a monolithic stem coupled with a standard modular head (Figure 1). Re-establishing appropriate hip biomechanics can contribute to a slower wear of THA components and may ease the revision of acetabular components by temporarily removing the interchangeable neck [2]

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Discussion

Conclusion