Dual mobility cup in hip arthroplasty: An in-depth analysis of joint registries.

AbstractAlthough total hip arthroplasty (THA) has shown successful results, instability remains a major complication. In recent years, dual mobility cups (DMC) have gained interest among clinicians thanks to its low rate of dislocation and good clinical results. The main aim of this work was to describe the accuracy of data on DMC from national and regional joint registries (JRs) and the available worldwide literature. We identified topics on DMC among JRs to propose a new harmonized and standardized section for DMC with the aim to understand its surveillance over the time. We extracted survival and implant data for a separate analysis. After performing a critical exclusion process, nine JRs were considered eligible and included for final synthesis; these were the results from the available worldwide data from JRs. In our study, eight analyzed JRs reported a slight increase in DMC use in the last decade. In all the JRs evaluated and the available articles, dislocation remains one of the main reasons for revision and re‐revision in hip arthroplasties. DMC is considered to be a valid construct increasingly used worldwide in primary and revision THA with the primary aim of reducing dislocation rates. Annual reports from JRs collect heterogeneous and low‐quality information about outcomes and surveillance of DMC, creating a burden for clinicians to extract comparable data from different JRs. Longer follow‐up and a systematic registering of DMCs with international registry harmonization are needed to monitor DMC outcomes

Tribological Behaviour of Ceramic Hip Replacements

Since 1960, when the first hip prosthesis was introduced, up to now, several implant typologies have been proposed trying to meet the increasing clinical demands of more and more active and young patients. A substantial evolution of implant design has been occurring, both in terms of materials and geometry, basically driven by their tribological performances. Indeed, the main concern of hip implants consists in the release of wear debris, which can lead to implant loosening and failure. Thus, many studies on wear and lubrication of hip prostheses have been published in the last 15 years, mainly focused on experimental researches but also on numerical/modeling approaches. The aim of this work is to review the history of hip implants from a tribological point of view with a focus on ceramic-on-ceramic replacements, which represent the most advanced solution in terms of wear strength and chemical inertness. The main drawbacks of these implants, as the brittleness and the squeaking, are discussed and novel solutions examined

In Silico Optimization of Femoral Fixator Position and Configuration by Parametric CAD Model

Structural analysis, based on the finite element method, and structural optimization, can help surgery planning or decrease the probability of fixator failure during bone healing. Structural optimization implies the creation of many finite element model instances, usually built using a computer-aided design (CAD) model of the bone-fixator assembly. The three most important features of such CAD models are: parameterization, robustness and bidirectional associativity with finite elements (FE) models. Their significance increases with the increase in the complexity of the modeled fixator. The aim of this study was to define an automated procedure for the configuration and placement of fixators used in the treatment of long bone fractures. Automated and robust positioning of the selfdynamisable internal fixator on the femur was achieved and sensitivity analysis of fixator stress on the change of major design parameters was performed. The application of the proposed methodology is considered to be beneficial in the preparation of CAD models for automated structural optimization procedures used in long bone fixation

Wear behavior characterization of hydrogels constructs for cartilage tissue replacement

This paper aims to characterize the wear behavior of hydrogel constructs designed for human articular cartilage replacement. To this purpose, poly (ethylene glycol) diacrylate (PEGDA) 10% w/v and gellan gum (GG) 1.5% w/v were used to reproduce the superior (SUP) cartilage layer and PEGDA 15% w/v and GG 1.5% w/v were used to reproduce the deep (DEEP) cartilage layer, with or without graphene oxide (GO). These materials (SUP and DEEP) were analyzed alone and in combination to mimic the zonal architecture of human articular cartilage. The developed constructs were tested using a four-station displacement control knee joint simulator under bovine calf serum. Roughness and micro-computer tomography (µ-CT) measurements evidenced that the hydrogels with 10% w/v of PEGDA showed a worse behavior both in terms of roughness increase and loss of uniformly distributed density than 15% w/v of PEGDA. The simultaneous presence of GO and 15% w/v PEGDA contributed to keeping the hydrogel construct’s characteristics. The Raman spectra of the control samples showed the presence of unreacted C=C bonds in all the hydrogels. The degree of crosslinking increased along the series SUP < DEEP + SUP < DEEP without GO. The Raman spectra of the tested hydrogels showed the loss of diacrylate groups in all the samples, due to the washout of unreacted PEGDA in bovine calf serum aqueous environment. The loss decreased along the series SUP > DEEP + SUP > DEEP, further confirming that the degree of photo-crosslinking of the starting materials plays a key role in determining their wear behavior. µ-CT and Raman spectroscopy proved to be suitable techniques to characterize the structure and composition of hydrogels

In Vitro versus In Vivo Phase Instability of Zirconia-Toughened Alumina Femoral Heads: A Critical Comparative Assessment

A clear discrepancy between predicted in vitro and actual in vivo surface phase stability of BIOLOX (R) delta zirconia-toughened alumina (ZTA) femoral heads has been demonstrated by several independent research groups. Data from retrievals challenge the validity of the standard method currently utilized in evaluating surface stability and raise a series of important questions: (1) Why do in vitro hydrothermal aging treatments conspicuously fail to model actual results from the in vivo environment? (2) What is the preponderant microscopic phenomenon triggering the accelerated transformation in vivo? (3) Ultimately, what revisions of the current in vitro standard are needed in order to obtain consistent predictions of ZTA transformation kinetics in vivo? Reported in this paper is a new in toto method for visualizing the surface stability of femoral heads. It is based on CAD-assisted Raman spectroscopy to quantitatively assess the phase transformation observed in ZTA retrievals. Using a series of independent analytical probes, an evaluation of the microscopic mechanisms responsible for the polymorphic transformation is also provided. An outline is given of the possible ways in which the current hydrothermal simulation standard for artificial joints can be improved in an attempt to reduce the gap between in vitro simulation and reality

Graphene Oxide‐Doped Gellan Gum–PEGDA Bilayered Hydrogel Mimicking the Mechanical and Lubrication Properties of Articular Cartilage

Articular cartilage (AC) is a specialized connective tissue able to provide a low-friction gliding surface supporting shock-absorption, reducing stresses, and guaranteeing wear-resistance thanks to its structure and mechanical and lubrication properties. Being an avascular tissue, AC has a limited ability to heal defects. Nowadays, conventional strategies show several limitations, which results in ineffective restoration of chondral defects. Several tissue engineering approaches have been proposed to restore the AC's native properties without reproducing its mechanical and lubrication properties yet. This work reports the fabrication of a bilayered structure made of gellan gum (GG) and poly (ethylene glycol) diacrylate (PEGDA), able to mimic the mechanical and lubrication features of both AC superficial and deep zones. Through appropriate combinations of GG and PEGDA, cartilage Young's modulus is effectively mimicked for both zones. Graphene oxide is used as a dopant agent for the superficial hydrogel layer, demonstrating a lower friction than the nondoped counterpart. The bilayered hydrogel's antiwear properties are confirmed by using a knee simulator, following ISO 14243. Finally, in vitro tests with human chondrocytes confirm the absence of cytotoxicity effects. The results shown in this paper open the way to a multilayered synthetic injectable or surgically implantable filler for restoring AC defects

Surface analysis on revised hip implants with stem taper for wear and failure incidence evaluation: a first investigation

Background: As revision surgeries of total hip arthroplasty are going to increase, success or failure of revised implants is a fundamental aspect in the orthopaedic field. Today, slight is known about the success rate of revised total hip arthroplasty when the femoral head is substituted on a retained stem. Question: We wanted to investigate if the interposition of a stem taper adapter between the paired elements can influence this rate of success. Methods: From a total of more than 1000 revised implants, recorded during their follow up in a regional registry, the study was limited to the ones subjected to a surgical revision, where the head has been revised but the stem taper has not. Investigations on wear, roughness, and corrosion on the available explants were conducted, with the aim of providing visual and empirical response on the topic and to furnish to other researches useful data for comparison. Results: Our results highlighted a higher incidence of second revisions when the femoral head is substituted without using an adapter. The topographic analysis refers that it is not evident a predominant roughness along any of the stems directions: no evidences were found that would define a recurrent rougher direction. This indicates a homogeneous worsening or corrosion of the stem taper along the circumference. Further, we found that the roughness values of the specimens analyzed not influence their surfaces and there is no a direct relation between the roughness of the bore heads and the stem tapers