Abrasion resistance of oxidized zirconium in comparison with CoCrMo and titanium nitride coatings for artificial knee joints

Retrieval Analysis of Titanium Nitride Coatings for Orthopaedic Implants

BACKGROUND

The first generation of titanium nitride (TiN) coatings for orthopaedic implants was clinically introduced in the 1990s because of their promising biocompatibility, wear resistance, and corrosion resistance. This study evaluated the in vivo performance of early TiN-coated knee and hip implants, focusing on the bearing surfaces and mechanisms of in vivo damage.

METHODS

There were 13 TiN-coated implants (5 knee and 8 hip) retrieved from 8 patients as part of a multi-institutional implant retrieval program. The average implantation time was 4.25 years for knees and 17.5 years for hips. Implant revisions occurred for various reasons, including polyethylene wear, loosening, pain, infection, and instability. Components were examined using a semiquantitative scoring method, and surface roughness measurements were performed using white-light interferometry. Surface morphology, chemistry, and particle characterization were also assessed by scanning electron microscopy.

RESULTS

For hips, mild corrosion was found on femoral head tapers, along with severe scratching on certain femoral heads. Knee implants exhibited low burnishing and scratching for both mechanisms. Roughness measurements (Sa) were 37.3 nm (interquartile range = 22.0 to 62.4) for hips and 85.3 nm (interquartile range = 66.3 to 110) for knees. The observed scratch depth in both hip and knee implants due to third-body particles ranged from 0.3 to 1.3 μm. The coating coverage remained intact in the majority of the implants, with 2 cases of small, localized cohesive chipping and substrate exposure.

CONCLUSIONS

The results of this study confirm the potential in vivo durability of early TiN coatings and will be useful in benchmarking wear tests for modern TiN-coated orthopaedic implants.

Load, unload and repeat: Understanding the mechanical characteristics of zirconia in dentistry

OBJECTIVES

Zirconia-based dental restorations and implants are gaining attention due to their bioactivity, corrosion resistance and mechanical stability. Further, surface modification of zirconia implants has been performed at the macro-, micro- and nanoscale to augment bioactivity. While zirconia's physical and chemical characteristics have been documented, its relation to mechanical performance still needs to be explored. This extensive review aims to address this knowledge gap.

METHODS

This review critically compares and contrasts the findings from articles published in the domain of 'mechanical stability of zirconia\ in dentistry' based on a literature survey (Web of Science, Medline/PubMed and Scopus databases) and a review of the relevant publications in international peer-reviewed journals. Reviewing the published data, the mechanical properties of zirconia, such as fracture resistance, stress/tension, flexural strength, fatigue, and wear are detailed and discussed to understand the biomechanical compatibility of zirconia with the mechanical performance of modified zirconia in dentistry also explored.

RESULTS

A comprehensive insight into dental zirconia's critical fundamental mechanical characteristics and performance is presented. Further, research challenges and future directions in this domain are recommended.

SIGNIFICANCE

This review extends existing knowledge of zirconia's biomechanical performance and it they can be modulated to design the next generation of zirconia dental restorations and implants to withstand long-term constant loading.

No difference in patient reported outcome and inflammatory response after coated and uncoated total knee arthroplasty - a randomized controlled study

BACKGROUND

Allergies against implant materials are still not fully understood. Despite controversies about its relevance, some patients need treatment with hypoallergenic implants. This study compared coated and standard total knee arthroplasty (TKA) regarding inflammatory response and patient-reported outcome measures (PROMs).

METHODS

76 patients without self-reported allergies against implant materials were included in a RCT and received a coated or standard TKA of the same cemented posterior-stabilized knee system. 73 patients completed the 3-year follow-up. Two patients died and there was one revision surgery. Serum levels of cytokines with a possible role in implant allergy were measured in patient`s serum (IL-1beta, IL-5, IL-6, IL-8, IL-10, IFN γ, TNF α) prior to, one and three years after surgery. Furthermore, PROMs including knee function (Oxford Knee Score, Knee Society Score) and health-related quality of life (QoL, EuroQuol questionnaire) were assessed. Additionally, 8 patients with patch-test proven skin allergy against implant materials who received the coated implant were assessed similarly and compared to a matched-pair group receiving the same implant.

RESULTS

There were no differences in function and QoL between the assessed groups at any follow-up. The majority of patients demonstrated no elevation of the measured blood cytokines. Cytokine patterns showed no differences between study groups at any follow-up. The allergy patients demonstrated slower functional improvement and minor differences in cytokine pattern. Yet these results were not significant. There were no differences in the matched-pair analysis.

CONCLUSION

We observed no relevant increase in serum cytokine levels in any group. The inflammatory response measured seems limited, even in allergy patients. Furthermore, there were no differences between coated and standard TKA in non-allergy patients in the 3-year Follow-Up period.

TRIAL REGISTRATION

The study protocol was registered in the US National Institutes of Health's database ( http://www.

CLINICALTRIALS

gov ) registry under NCT03424174 on 03/17/2016.

"Systematic review and meta-analysis of ceramic coated implants in total knee arthroplasty. Comparable mid-term results to uncoated implants."

BACKGROUND

Nitride-based ceramic coatings, such as titanium nitride (TiN) and titanium niobium nitride (TiNbN), have been introduced in total knee arthroplasty (TKA) to enhance the mechanical properties and biocompatibility of knee components, harden the metal surface and reduce CoCrMo exposure and metal ion release. However, the theoretical advantages of these ceramic coatings in TKA have yet to be fully elucidated. This systematic review aimed to provide clinical evidence on mid-term outcomes of ceramic-coated knee prostheses in comparison with uncoated standard CoCrMo knee prostheses in primary TKA. The hypothesis was that ceramic-coated implants can be used in primary TKA with no inferior outcomes compared to uncoated CoCrMo implants.

METHODS

A systematic review of the literature was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines to find all clinical studies regarding primary TKA with ceramic-coated knee prostheses. MEDLINE (PubMed), Embase and Cochrane Library were searched from 1990 to October 2020 to identify relevant studies for the first qualitative analysis. Using PICOS eligibility criteria, a subgroup of the selected studies was used to perform a meta-analysis.

RESULTS

Fifteen studies were included in this systematic review, of which six were included in the meta-analysis: 3 randomized controlled trials, 2 retrospective comparative studies and 1 prospective cross-sectional study. Pooled data overall included 321 coated TKAs vs. 359 uncoated TKAs and a mean follow-up of 4.6 years (range, 2-10 years). No significant difference in the implant survival risk ratio with revision or reoperation due to any reason was found between coated and uncoated TKAs, even considering the RCT study subgroup with a risk ratio of 1.02 (P = 0.34). No significant differences were found for postoperative complications, clinical scores, or metal blood concentrations at 1 year.

CONCLUSION

The findings of this systematic review and meta-analysis support the statement that ceramic-coated TKAs are not inferior to uncoated TKAs, showing comparable survival rates, complication rates and clinical outcomes. There is strong evidence that ceramic-coated TKA does not improve the clinical results or survival rate in comparison with uncoated TKA.

LEVEL OF EVIDENCE

II,  Therapeutic.

Amorphous Carbon Coatings for Total Knee Replacements-Part I: Deposition, Cytocompatibility, Chemical and Mechanical Properties

Diamond-like carbon (DLC) coatings have the potential to reduce implant wear and thus to contribute to avoiding premature failure and increase service life of total knee replacements (TKAs). This two-part study addresses the development of such coatings for ultrahigh molecular weight polyethylene (UHMWPE) tibial inlays as well as cobalt-chromium-molybdenum (CoCr) and titanium (Ti64) alloy femoral components. While a detailed characterization of the tribological behavior is the subject of part II, part I focusses on the deposition of pure (a-C:H) and tungsten-doped hydrogen-containing amorphous carbon coatings (a-C:H:W) and the detailed characterization of their chemical, cytological, mechanical and adhesion behavior. The coatings are fabricated by physical vapor deposition (PVD) and display typical DLC morphology and composition, as verified by focused ion beam scanning electron microscopy and Raman spectroscopy. Their roughness is higher than that of the plain substrates. Initial screening with contact angle and surface tension as well as in vitro testing by indirect and direct application indicate favorable cytocompatibility. The DLC coatings feature excellent mechanical properties with a substantial enhancement of indentation hardness and elastic modulus ratios. The adhesion of the coatings as determined in modified scratch tests can be considered as sufficient for the use in TKAs.

Wear performance of inverted non-conforming bearings in anatomic total shoulder arthroplasty

BACKGROUND

Glenoid component failures still represent the most common complication in total shoulder arthroplasty. These failures depend on several factors, including ultra-high molecular weight polyethylene (UHMWPE) wear. One reason for UHMWPE wear in total shoulder arthroplasty may be the current use of a spherical prosthetic humeral head against a radially mismatched UHMWPE glenoid component, which leads to reduced glenohumeral translations, glenoid edge loading and high translational forces during shoulder motions. The aim of this study was to assess the in vitro wear of an anatomic total shoulder prosthesis with non-spherical non-conforming bearings with inverted conventional materials.

METHODS

The wear of a vitamin E-blended UHMWPE non-spherical humeral head articulating against a non-conforming titanium-niobium nitride (TiNbN)-coated metallic glenoid was tested using a joint simulator. The wear test was performed by applying a constant load of 756 N with angular motions and translations.

RESULTS

After 2.5 million cycles, the mean wear rate of the humeral head was 0.28 ± standard deviation (SD) 0.45 mg/million cycles.

CONCLUSION

The low wear rate of the vitamin E UHMWPE humeral head supports the use of non-spherical non-conforming bearings with inverted conventional materials in anatomic total shoulder arthroplasty.

Aucubin suppresses Titanium particles‑mediated apoptosis of MC3T3‑E1 cells and facilitates osteogenesis by affecting the BMP2/Smads/RunX2 signaling pathway

Aucubin represents an iridoid glucoside separated from multiple Chinese herbs, which has been demonstrated to possess numerous pharmacological activities. In the present study, the aim was to investigate the roles and mechanisms of aucubin in the suppression of mouse MC3T3-E1 osteoblast apoptosis induced by Titanium particles and the promotion of bone formation. MTT assay and flow cytometry were performed to analyze cell viability and apoptosis, respectively. ELISA and para-nitrophenyl phosphate colorimetry were carried out to evaluate the oxidative stress markers and alkaline phosphatase (ALP). Western blotting and reverse transcription-quantitative polymerase chain reaction assays were used to evaluate the associated mRNA and protein expression. The results revealed that aucubin enhanced the cell activity of MC3T3-E1 cells treated with Ti particles. Aucubin suppressed the apoptosis of Ti particles-induced MC3T3-E1 cells and facilitated osteogenesis by affecting the B-cell lymphoma-2 (Bcl-2), Bcl-2 associated X protein, ALP and associated osteogenic factors expression. Aucubin reduced the oxidative stress in Ti particles-induced MC3T3-E1 cells. In addition, aucubin upregulated the bone morphogenetic protein 2 (BMP2)/Smads/runt related transcription factor 2 (RunX2) pathway in Ti particles-induced MC3T3-E1 cells. In conclusion, the present study confirmed that aucubin suppressed the Ti particles-mediated apoptosis of MC3T3-E1 cells and facilitated osteogenesis by affecting the BMP2/Smads/RunX2 signaling pathway.

In vitro evaluation of frictional force of a novel elastic bendable orthodontic wire

OBJECTIVES

To determine the frictional force (FF) of the novel, elastic, bendable titanium-niobium (Ti-Nb) alloy orthodontic wire in stainless steel (SS) brackets and to compare it with those of titanium-nickel (Ti-Ni) and titanium-molybdenum (Ti-Mo) alloy wires.

MATERIALS AND METHODS

Three sizes of Ti-Nb, Ti-Ni, and Ti-Mo alloy wires were ligated with elastic modules to 0.018-inch and 0.022-inch SS brackets. The dynamic FFs between the orthodontic wires and SS brackets were measured at three bracket-wire angles (0°, 5°, and 10°) with an Instron 5567 loading apparatus (Canton, Mass).

RESULTS

FFs increased gradually with the angle and wire size. In the 0.018-inch-slot bracket, the dynamic FFs of Ti-Nb and Ti-Ni alloy wires were almost the same, and those of the Ti-Mo alloy wire were significantly greater ( P<0.05). FF values were 1.5-2 times greater in the 0.022-inch-slot bracket than in the 0.018-inch-slot bracket, regardless of alloy wire type, and the Ti-Mo alloy wire showed the greatest FF. Scanning electric microscopic images showed that the surface of the Ti-Mo alloy wire was much rougher than that of the Ti-Ni and Ti-Nb alloy wires.

CONCLUSION

These findings demonstrate that the Ti-Nb alloy wire has almost the same frictional resistance as the Ti-Ni alloy wire, although it has a higher elastic modulus.

Titanium-Nitride Coating of Orthopaedic Implants: A Review of the Literature

Surfaces of medical implants can be enhanced with the favorable properties of titanium-nitride (TiN). In a review of English medical literature, the effects of TiN-coating on orthopaedic implant material in preclinical studies were identified and the influence of these effects on the clinical outcome of TiN-coated orthopaedic implants was explored. The TiN-coating has a positive effect on the biocompatibility and tribological properties of implant surfaces; however, there are several reports of third body wear due to delamination, increased ultrahigh molecular weight polyethylene wear, and cohesive failure of the TiN-coating. This might be due to the coating process. The TiN-coating process should be optimized and standardized for titanium alloy articulating surfaces. The clinical benefit of TiN-coating of CoCrMo knee implant surfaces should be further investigated.

Hip dislocation increases roughness of oxidized zirconium femoral heads in total hip arthroplasty: an analysis of 59 retrievals

The aims of this study were to assess damage on the surface of retrieved oxidized zirconium (OxZr) metal femoral heads, to measure surface roughness of scratches, and to evaluate the extent of surface effacement using scanning electron microscopy (SEM). Ceramic zirconia-toughened alumina heads were analyzed for comparison. OxZr femoral heads explanted for recurrent dislocation had the most severe damage (P<0.001). The median surface roughness of damaged OxZr femoral heads was 1.49μm, compared to 0.084μm for damaged ceramic heads and 0.052μm for undamaged OxZr (P<0.001). This may be of clinical concern because increased surface roughness has the potential to increase the wear of polyethylene liners articulating against these OxZr heads in THA.

Advances in the surface modification techniques of bone-related implants for last 10 years

At the time of implanting bone-related implants into human body, a variety of biological responses to the material surface occur with respect to surface chemistry and physical state. The commonly used biomaterials (e.g. titanium and its alloy, Co-Cr alloy, stainless steel, polyetheretherketone, ultra-high molecular weight polyethylene and various calcium phosphates) have many drawbacks such as lack of biocompatibility and improper mechanical properties. As surface modification is very promising technology to overcome such problems, a variety of surface modification techniques have been being investigated. This review paper covers recent advances in surface modification techniques of bone-related materials including physicochemical coating, radiation grafting, plasma surface engineering, ion beam processing and surface patterning techniques. The contents are organized with different types of techniques to applicable materials, and typical examples are also described.

Ceramics in THR Bearings: Behavior under Off-Normal Conditions

The use of ceramics bearings in total hip joint replacement (THR) has increased markedly in the last ten years thanks to the optimum wear behaviour of ceramic-on-ceramic bearings and of the high biological safety of ceramic wear debris. As the number of ceramic THR bearings is increasing, also the number of implants that experience off-normal working conditions, e.g. edge loading, third bodies in the joint, soft tissues laxity, dislocation/subluxation of the joint, increases. Under all such conditions the surface of the bearing can be damaged to variable extent, leading eventually to a limitation of the expected performances of the implant.

An overview of recent advances in designing orthopedic and craniofacial implants

Great deal of research is still going on in the field of orthopedic and craniofacial implant development to resolve various issues being faced by the industry today. Despite several disadvantages of the metallic implants, they continue to be used, primarily because of their superior mechanical properties. In order to minimize the harmful effects of the metallic implants and its by-products, several modifications are being made to these materials, for instance nickel-free stainless steel, cobalt-chromium and titanium alloys are being introduced to eliminate the toxic effects of nickel being released from the alloys, introduce metallic implants with lower modulus, reduce the cost of these alloys by replacing rare elements with less expensive elements etc. New alloys like tantalum, niobium, zirconium, and magnesium are receiving attention given their satisfying mechanical and biological properties. Non-oxide ceramics like silicon nitride and silicon carbide are being currently developed as a promising implant material possessing a combination of properties such as good wear and corrosion resistance, increased ductility, good fracture and creep resistance, and relatively high hardness in comparison to alumina. Polymer/magnesium composites are being developed to improve mechanical properties as well as retain polymer's property of degradation. Recent advances in orthobiologics are proving interesting as well. This paper thus deals with the latest improvements being made to the existing implant materials and includes new materials being introduced in the field of biomaterials.

Metal hypersensitivity and metal ion levels in patients with coated or uncoated total knee arthroplasty: a randomised controlled study

PURPOSE

Metal ion release by orthopaedic implants may cause local and systemic effects and induce hypersensitivity reactions. Coated implants have been developed to prevent or reduce these effects. This study was initiated to investigate the safety of a novel coating for total knee arthroplasty (TKA) implants.

METHODS

A total of 120 patients undergoing primary TKA with no history of hypersensitivity and no other metal implant were randomised to receive either a coated or uncoated implant. Chromium (Cr), cobalt (Co), molybdenum (Mb) and nickel (Ni) hypersensitivity patch testing and plasma ion concentrations were evaluated pre-operatively and one year post-operatively.

RESULTS

At the one year follow-up both groups demonstrated significant improvement in knee function and quality of life. One new weakly positive reaction to Co in the TKA group with coated implant and two doubtful skin reactions to Ni (one in each group) were noted. Even with sensitisation to implant materials no skin reactions were observed. Plasma metal ion concentrations did not increase and were not elevated at the one year follow-up in either group.

CONCLUSIONS

Sensitisation after TKA was rare and had no influence on clinical results. TKA with coated implant and standard TKA demonstrated no plasma metal ion elevation.

In vivo testing of canine prosthetic femoral components with HA-Ti ladder-type coating on vacuum plasma-sprayed Ti substrate

The purpose of the present study was to observe the structure and functional change of the bone-coating-prosthesis interface in vivo and to evaluate the histocompatibility of self-made prosthetic femoral components in the body and the degree of their bonding with the surrounding bone tissues as well as their stability. Six mature beagle dogs underwent bilateral hip replacement with prosthetic femur components. Three groups were established in terms of different coating of prothesis (four joints in each group): atmosphere (A) plasma-sprayed pure titanium (Ti) prosthetic joint with hydroxyapatite (HA) coating (HA+Ti+A group); vacuum (V) plasma-sprayed pure Ti prosthetic joint with HA coating (HA+Ti+V group); vacuum plasma-sprayed pure Ti prosthetic joint with Ti-HA stepped coating (Ti+HAG+Ti+V group). The hip joints were functionally evaluated, and subjected to X-ray examination, biomechanics inspection, and histological examination. As a result, X-ray imaging revealed all prosthetic joints were in a good location and no dislocation of joint was found. Shear strength of interface was significantly higher in Ti+HAG+Ti+V group than in HA+Ti+V group (P<0.05) and HA+Ti+A group (P<0.05) at 28th week. Histological examination showed the amount of newborn bone in Ti+HAG+Ti+V group was more than in HA+Ti+V group and HA+Ti+A group after 28 weeks. It was suggested that vacuum plasma-sprayed pure Ti prosthetic joint with TI-HA stepped coating could improve the bonding capacity of bone-prosthesis, enhance the stability of prosthesis, and increase the fixion of prosthetic femoral components because of better bone growth. This new type of biological material in prosthetic femoral components holds promises for application in clinical practice.