The 2007 Otto Aufranc Award. Ceramic-on-metal hip arthroplasties: a comparative in vitro and in vivo study

Are Corrosion and Material Loss a Threat for Titanium-Titanium Tapers in Total Hip Arthroplasty Modular Acetabular Components?

BACKGROUND

Extensive research has reported on fretting corrosion and material loss for a variety of metal taper interfaces in orthopedic devices. For modular acetabular shell-liner constructs, the interfaces studied thus far have consisted of mixed-metal pairings, and the risk of fretting corrosion and material loss for the all-titanium (Ti) shell-liner taper junction in one ceramic-on-ceramic (COC) design remains poorly understood. We asked: do Ti shell-liner taper interfaces in COC total hip arthroplasty devices show in vivo evidence of (1) fretting and/or corrosion, and (2) quantifiable potential material loss?

METHODS

We examined 22 shell-liner pairs and 22 single liners from retrieved COC components. The taper interface surfaces were assessed for fretting corrosion using a semiquantitative scoring method and imaged with scanning electron microscopy. A subcohort of components was measured with a coordinate measuring machine, and volumetric material loss and maximum wear depth were calculated.

RESULTS

Fretting corrosion at the taper interfaces was minimal to mild for 95% of liners and 100% of shells. Imaging revealed fretting marks within a band of corrosion on some implants and evidence of corrosion not in the proximity of mechanical damage. Estimated material loss ranged from 0.2 to 1.3 mm3 for liners, and 0.5 to 1.1 mm3 for shells. Maximum wear depth for all components was 0.03 mm or less.

CONCLUSIONS

Our results indicate that, compared to other taper junctions in total joint arthroplasty, the risk of corrosion and material loss may be minimal for Ti shell-liner interfaces.

Influence of Physical Activity and Cup Orientation on Metal Ion Release and Oxidative Stress in Metal-on-Metal and Ceramic-on-Metal Total Hip Arthroplasty

BACKGROUND

Metal-on-metal (M-M) total hip arthroplasty (THA) has shown adverse reactions to metal debris, abnormal soft-tissue reactions, and high blood metal ion levels. This study aims to: (1) assess whether the toxicity of high levels of ions is related to altered oxidative stress and (2) evaluate tribological factors related to increased blood levels of chromium (Cr) and cobalt (Co) ions.

METHODS

A cross-sectional analytical descriptive study was conducted on 75 patients. A total of 25 underwent M-M THA, 25 ceramic-on-metal (C-M) THA, and 25 were on the THA waiting list. Ion metallic levels in blood, oxidative stress, physical activity, and implant position were compared.

RESULTS

In the M-M group, Co and Cr levels were significantly higher than those found in the C-M group and the control group (p < 0.01). We found no differences in terms of oxidative stress between the groups. Also, we did not find a correlation between metal blood levels and oxidative stress indicators, the physical activity of the patients or the position of the implants between groups.

CONCLUSIONS

The use of M-M bearing surfaces in THA raises the levels of metals in the blood without modifying oxidative stress regardless of the physical activity levels of the patients. Therefore, although patients with M-M bearings require close monitoring, it does not seem necessary to recommend the restriction of physical activity in patients with M-M or C-M arthroplasties.

Ceramic-on-Metal Bearing in Total Hip Arthroplasty—Was It So Bad? A Narrative Review and a Critical Analysis of the Literature

Hip replacement has significantly improved the quality of life of patients with symptomatic hip osteoarthritis. Various bearings have been developed over the years. Each of these has advantages and disadvantages. On the one hand, Metal-on-Metal (MoM) has been associated with a high level of wear and metal ion release of chromium (Cr) and cobalt (Co). On the other hand, Ceramic-on-Ceramic (CoC) bearings, known to have a wear rate close to zero, have been associated with an increased risk of squeaking and component fracture. Ceramic-on-Metal (CoM), a hybrid hard-on-hard bearing, was proposed to overcome the CoC and MoM limits. Preliminary clinical and radiographical results have been described as favourable. Due to the failure of MoM and the increased risk of ion release and metal toxicity, CoM was withdrawn from the market without causing significant clinical complications. Data from the literature showed that CoM bearings are reliable and safe at medium- and long-term follow-up, if correctly implanted. In this narrative review, we analysed the real risks and benefits associated with the implantation of CoM bearings.

Comprehensive Review on Biomaterials and Their Inherent Behaviors for Hip Repair Applications

Developing biomaterials for hip prostheses is challenging and requires dedicated attention from researchers. Hip replacement is an inevitable and remarkable orthopedic therapy for enhancing the quality of patient life for those who have arthritis as well as trauma. Generally, five types of hip replacement procedures are successfully performed in the current medical market: total hip replacements, hip resurfacing, hemiarthroplasty, bipolar, and dual mobility systems. The average life span of artificial hip joints is about 15 years, and several studies have been conducted over the last 60 years to improve the performance and thereby increase the lifespan of artificial hip joints. Present-day prosthetic hip joints are linked to the wide availability of biomaterials. Metals, ceramics, and polymers are some of the most promising types of biomaterials; nevertheless, each biomaterial has advantages and disadvantages. Metals and ceramics fail in most applications owing to stress shielding and the emission of wear debris; ongoing research is being carried out to find a remedy to these unfavorable responses. Recent research found that polymers and composites based on polymers are significant alternative materials for artificial joints. With growing research and several biomaterials, recent reviews lag in effectively addressing hip implant materials' individual mechanical, tribological, and physiological behaviors. This Review comprehensively investigates the historical evolution of artificial hip replacement procedures and related biomaterials' mechanical, tribological, and biological characteristics. In addition, the most recent advances are also discussed to stimulate and guide future researchers as they seek more effective methods and synthesis of innovative biomaterials for hip arthroplasty application.

Adverse Local Tissue Reaction Associated With Ceramic-On-Metal Bearing Surface in Primary Total Hip Arthroplasty: Report of Two Cases

Total hip arthroplasty (THA) is one of the most common and successful surgical procedures worldwide. At the same time, it is constantly evolving, and as a consequence, advances in implant technology have led to significant improvements in the different materials of the acetabular and femoral components. The selection of bearing surfaces and their tribology are critical to achieving a successful outcome. Pseudotumors are important, and usually misdiagnosed, complications associated with hard bearing surfaces such as metal-on-metal couples. They belong to a group of reactions called adverse local tissue reaction, which can occur in the vicinity of any THA. We present 2 cases of adverse local tissue reaction associated with the use of ceramic-on-metal bearings surfaces in 2 primary THAs that were treated with modular component exchange during single-stage revision surgery.

Level of Evidence

IV.

Effect of Operation Room Nursing Intervention and Ceramic Prosthesis on Total Hip Arthroplasty

In order to solve the problems of large trauma, many postoperative complications, and complex operation of artificial hip arthroplasty, a method to analyze the application effect of operating room nursing intervention in artificial hip arthroplasty was proposed. Firstly, 120 patients who underwent hip arthroplasty in our hospital from January to December 2017 were selected; Secondly, they were randomly divided into routine group (60 cases) and intervention group (60 cases); finally, on this basis, the intervention group strengthened the nursing in the operating room and used nanoceramic prosthesis. The Harris score of hip joint, the incidence of postoperative complications, and the satisfaction with nursing services were compared between the two groups. The results showed that the Harris score of hip joint and the satisfaction score of nursing service in the intervention group were significantly higher than those in the routine group (P < 0.05); the incidence of postoperative complications in the intervention group was significantly lower than that in the routine group (P < 0.05). It is proved that actively carrying out nursing intervention in the operating room and using nanoceramic prosthesis can not only improve the clinical efficacy and nursing service satisfaction of patients undergoing total hip arthroplasty but also reduce the incidence of complications.

Safety of vitamin E-infused highwall liners for routine use in primary total hip arthroplasty: single centre, short-term follow-up of 1221 cases

BACKGROUND

Introduction of new implants should be monitored closely to capture any signs of compromising patient safety. Vitamin E infused highly-crosslinked polyethylene liners (VEPE) offer the potential for reduced wear. Highwall liners have been hypothesised to result in increased wear and potential liner fractures. The aim of this study was to determine the 3-7-year follow-up of highwall VEPE for primary total hip arthroplasty (THA), focusing on liner-related complications.

METHODS

We included 1221 consecutive THA operations from July 2010 to May 2014 with minimum follow-up of 3 (3.1-6.8) years Data collected included demographics, implant data, complications, reoperations, and deaths. Data were cross-referenced with the Danish Hip Arthroplasty Registry in order to ensure validity and completeness. Acetabular shell position was measured using Martell Hip Analysis Suite in a subgroup of 931 THAs.

RESULTS

Cumulative stem revision and shell revision at 3-year follow-up was 3.4% and 0.4% respectively. There were no revisions due to liner failure. Reason for revision included 11 dislocations, 15 soft-tissue revisions for infection, 44 stem revisions of which 34 were periprosthetic fractures and 13 shell revisions of which 6 were combined shell and stem revisions.

CONCLUSION

Early follow-up of VEPE liners for primary THA have not shown any revisions associated with liner failure. Continued monitoring of new materials are necessary to capture any signs of compromised patient safety.

Ceramic-on-metal bearing in short stem total hip arthroplasty: ions, functional and radiographic evaluation at mid-term follow-up

INTRODUCTION

The aim of this study is to evaluate clinical, radiographic and laboratory results of ceramic-on-metal (CoM) (hybrid hard bearing) in total hip arthroplasty (THA), associated with a short stem implant.

METHODS

From a cohort of 37 patients suffering from primary or secondary hip osteoarthritis who underwent THA using CoM bearing, 19 were suitable for this study. All procedures were performed by the same surgeon using a posterior-lateral approach. All patients were compared clinically using the Harris Hip Score (HHS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), visual analogue scale (VAS), 12-item Short Form Health Survey (SF12F/M), and radiographically (offset, CD angle, limb length discrepancy, cup inclination and anteversion, subsidence, osseointegration, heterotopic ossification). Blood samples were collected in order to evaluate chromium (Cr) and cobalt (Co) ions level. Radiographic evaluations were carried out by 3 different blinded surgeons. A statistical analysis was performed.

RESULTS

At a mean follow-up of 97 (73-125) months all implanted stems were well-positioned and osseointegrated. Clear improvements were observed for clinical scores comparing preoperative and postoperative values. Radiographic evaluation showed a good ability to restore proper articular geometry. Cr ion analysis revealed values below the safety threshold except for 1 case. Serum levels of Co were below the threshold in all patients. There was a statistically significant correlation only between Cr metal ions and length of follow-up.

CONCLUSIONS

CoM bearing has proven to be reliable and safe at a mean 8-year follow-up for patients in whom the components were correctly implanted. The rise of blood metal ions was minimal and involved neither systemic or local toxicity nor influenced clinical results.

Early Results of Our International, Multicenter, Multisurgeon, Double-Blinded, Prospective, Randomized, Controlled Trial Comparing Metal-on-Metal With Ceramic-on-Metal in Total Hip Arthroplasty

BACKGROUND

The aim of our prospective, multicenter, randomized, controlled trial (titled M2A-38 Ceramic-on-Metal RCT, NCT00754520) is to demonstrate noninferiority of a ceramic-on-metal (CoM) articulation compared with metal-on-metal (MoM) in total hip arthroplasty. The study arms are at 8 years since implantation, with metal ion and functional score analysis at 5 years.

METHODS

We recruited 211 patients between 2009 and 2011. The patients were randomized to ceramic or metal. A cohort of these patients had whole blood metal ions performed yearly, and all patients underwent annual radiographic and clinical outcome assessment. All revisions were recorded and some explants were analyzed. Recruitment ceased earlier than planned owing to concerns raised with failure of MoM implants.

RESULTS

No significant difference was seen in patient demographics, radiographic parameters, or functional outcomes at any time point. Lower cobalt ion levels were seen in the CoM group (P < .01) at all time points. Chromium levels were significantly lower in the CoM group up to 3 years, but raised at 5 years. There were slightly fewer revisions for adverse reaction to metal debris in the CoM group. Explant analysis suggested a different wear pattern to those seen in the MoM group.

CONCLUSION

The results demonstrated that the CoM articulation behaved the same as the MoM in terms of functional outcome and radiographic parameters. The CoM coupling also demonstrates raised metal ions beyond 3 years and increasing revisions for adverse reaction to metal debris. It remains difficult to see a clinical application for CoM and further exploration or use is not warranted.

Total Hip Arthroplasty: Past, Present, and Future. What Has Been Achieved?

In the 1960s, Sir John Charnley introduced to clinical practice his concept of low-friction total hip arthroplasty (THA). Although early designs were plagued by poor performance and even failure, there have been steady advances in implant designs, biomaterials, surgical techniques and an understanding of the biomechanical restoration of the hip; these advances have contributed to improvements in implant survival and clinical outcomes of THA in the past three decades. With improved wear resistance and mechanical reliability, a potential to last for at least 25 to 30 years are now available for THA. In this review, we focus on the evolution of THA and review current controversies and future directions of this procedure based on a single surgeon's 29-year of experience at a single institution.

Computationally efficient modelling of hip replacement separation due to small mismatches in component centres of rotation

Patient imaging and explant analysis has shown evidence of edge loading of hard-on-hard hip replacements in vivo. Experimental hip simulator testing under edge loading conditions has produced increased, clinically-relevant, wear rates for hard-on-hard bearings when compared to concentric conditions. Such testing, however, is time consuming and costly. A quick running computational edge loading model (Python Edge Loading (PyEL) - quasi-static, rigid, frictionless), capable of considering realistic bearing geometries, was developed. The aim of this study was to produce predictions of separation within the typical experimental measurement error of ∼0.5 mm. The model was verified and validated against comparable finite element (FE) models (including inertia and friction) and pre-existing experimental test data for 56 cases, covering a variety of simulated cup orientations, positions, tissue tensions, and loading environments. The PyEL model agreed well with both the more complex computational modelling and experimental results. From comparison with the FE models, the assumption of no inertia had little effect on the maximum separation prediction. With high contact force cases, the assumption of no friction had a larger effect (up to ∼5% error). The PyEL model was able to predict the experimental maximum separations within ∼0.3 mm. It could therefore be used to optimise an experimental test plan and efficiently investigate a much wider range of scenarios and variables. It could also help explain trends and damage modes seen in experimental testing through identifying the contact locations on the liner that are not easily measured experimentally.

Pseudotumor and Subsequent Implant Loosening as a Complication of Revision Total Hip Arthroplasty with Ceramic-on-Metal Bearing: A Case Report

Pseudotumors are not uncommon complications after total hip arthroplasty (THA) and may occur due to differences in bearing surfaces of the head and the liner ranging from soft to hard articulation. The most common causes of pseudotumors are foreign-body reaction, hypersensitivity and wear debris. The spectrum of pseudotumor presentation following THA varies greatly-from completely asymptomatic to clear implant failure. We report a case of pseudo-tumor formation with acetabular cup aseptic loosening after revision ceramic-on-metal hip arthroplasty. The patient described herein underwent pseudotumor excision and re-revision complex arthroplasty using a trabecular metal shell and buttress with ceramic-on-polyethylene THA. Surgeons should be aware of the possibility of a pseudotumor when dealing with revisions to help prevent rapid progression of cup loosening and implant failure, and should intervene early to avoid complex arthroplasty procedures.

Recent updates for biomaterials used in total hip arthroplasty

Background

Total hip arthroplasty (THA) is probably one of the most successful surgical interventions performed in medicine. Through the revolution of hip arthroplasty by principles of low friction arthroplasty was introduced by Sir John Charnley in 1960s. Thereafter, new bearing materials, fixation methods, and new designs has been improved. The main concern regarding failure of THA has been the biological response to particulate polyethylene debris generated by conventional metal on polyethylene bearing surfaces leading to osteolysis and aseptic loosening of the prosthesis. To resolve these problems, the materials of the modern THA were developed since then.

Methods

A literature search strategy was conducted using various search terms in PUBMED. The highest quality articles that met the inclusion criteria and best answered the topics of focus of this review were selected. Key search terms included ‘total hip arthroplasty’, ‘biomaterials’, ‘stainless steel’, ‘cobalt-chromium’, ‘titanium’, ‘polyethylene’, and ‘ceramic’.

Results

The initial search retrieved 6921 articles. Thirty-two articles were selected and used in the review.

Conclusion

This article introduces biomaterials used in THA and discusses various bearing materials in currentclinical use in THA as well as the newer biomaterials which may even further decrease wear and improve THA survivorship.

Increased Serum Ion Levels After Ceramic-on-Metal Bearing Total Hip Arthroplasty: Influence of an Asian Lifestyle

BACKGROUND

Recent clinical studies have suggested that systemic metal ion levels are significantly elevated at midterm follow-up in patients with ceramic-on-metal (COM) bearing. However, it is not clear whether there is a correlation between patient-related factors including the lifestyle and elevated levels of serum metal ions following COM total hip arthroplasty (THA).

METHODS

Serum metal levels were measured in 201 patients (234 hips) including 121 COM patients (140 hips) and 80 non-COM patients (94 hips). The Harris Hip Score, University of California, Los Angeles activity scale score, and Western Ontario and McMaster Universities Osteoarthritis Index score were measured and radiographs were obtained for the analysis.

RESULTS

Significantly higher levels of cobalt (Co) and chromium (Cr) were detected in the serum of the COM THA group (Co: 1.86 ± 4.0 μg/L; Cr: 1.81 ± 2.87 μg/L) than those of the non-COM THA group (Co: 0.27 ± 0.14 μg/L; Cr: 0.19 ± 0.25 μg/L; P < .001). The serum metal levels of patients who achieved the squatting position and the kneeling position were significantly higher than those of patients who could not squat (Co: P = .033; Cr: P = .074) and kneel (Co: P = .049; Cr: P = .031). The metal ion levels of the COM THA group correlated with the total range of motion (Co: P = .0293; Cr: P = .0399).

CONCLUSION

Patients who underwent a 36-mm COM THA showed high serum metal levels although good clinical outcomes at the midterm follow-up. We found that COM THA patients who were capable of greater range of motion, squatting, and kneeling are at risk of metal ion-related problems.

An in vitro simulation model to assess the severity of edge loading and wear, due to variations in component positioning in hip joint replacements

The aim of this study was to develop a preclinical in vitro method to predict the occurrence and severity of edge loading condition associated with the dynamic separation of the centres of the head and cup (in the absence of impingement) for variations in surgical positioning of the cup. Specifically, this study investigated the effect of both the variations in the medial–lateral translational mismatch between the centres of the femoral head and acetabular cup and the variations in the cup inclination angles on the occurrence and magnitude of the dynamic separation, the severity of edge loading, and the wear rate of ceramic‐on‐ceramic hip replacement bearings in a multi‐station hip joint simulator during a walking gait cycle. An increased mismatch between the centres of rotation of the femoral head and acetabular cup resulted in an increased level of dynamic separation and an increase in the severity of edge loading condition which led to increased wear rate in ceramic‐on‐ceramic bearings. Additionally for a given translational mismatch, an increase in the cup inclination angle gave rise to increased dynamic separation, worst edge loading conditions, and increased wear. To reduce the occurrence and severity of edge loading, the relative positions (the mismatch) of the centres of rotation of the head and the cup should be considered alongside the rotational position of the acetabular cup. This study has considered the combination of mechanical and tribological factors for the first time in the medial–lateral axis only, involving one rotational angle (inclination) and one translational mismatch. © 2017 The Authors Journal of Biomedical Materials Research Part B: Applied Biomaterials Published by Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1897–1906, 2018.

Clinical Results and Serum Metal Ion Concentrations following Ceramic-on-Metal Total Hip Arthroplasty at a Mean Follow-Up of 60 Months

Background. Increased metal ion levels following total hip arthroplasty (THA) with metal-on-metal bearings are a highly debated topic. Local soft tissue reactions with chronic pain and systemic side effects such as neuropathy are described. The aim of the current study was to determine the serum metal ion concentrations of Cobalt (Co) and Chrome (Cr) after THA with a ceramic-on-metal (CoM) bearing. Patients and Methods. Between 2008 and 2010, 20 patients underwent THA using a CoM bearing. Clinical function was evaluated by standardized scores systems (Harris Hip Score and WOMAC Score) and radiological examination included X-rays. Patient's blood samples were obtained for metal ion analysis and correlation analysis was done between these results and implant position. Results. Overall, 13 patients with 14 CoM devices were available for the current series. The mean age at time of surgery was 61 years (range, 41 to 85). The postoperative follow-up ranged from 49 to 68 months (mean, 58). Metal ion determination showed mean concentrations of 3,1 µg/L (range, 0,3–15,2 µg/L) for Co and 1,6 µg/L (range, 0,1–5,5 µg/L) for Cr, respectively. A correlation between cup anteversion and Co and Cr concentrations was shown. Conclusion. The current series showed increments for Co and Cr following CoM THA. However, these levels are lower compared to metal ion concentrations in patients with metal-on-metal bearings and the international accepted threshold for revision of MoM devices. We recommend routine follow-up including at least one obligatory evaluation of serum metal ion concentrations and an MRI once to exclude local soft tissue reactions.

Simultaneous measurement of friction and wear in hip simulators

We propose and have evaluated a method to measure hip friction during wear testing on a popular multi-station hip simulator. A 6-degree-of-freedom load cell underneath the specimen sensed forces and torques during implant wear testing of simulated walking. This included internal–external and adduction–abduction rotations which are often neglected during friction testing on pendulum-type machines. Robust mathematical analysis and data processing provided friction estimates in three simultaneous orthogonal rotations, over extended multi-million cycle wear tests. We tested various bearing couples including metal-on-plastic, ceramic-on-plastic, and metal-on-metal material couples. In one test series, new and intentionally scratched CoCrMo 40-mm-diameter femoral heads were tested against conventional ultrahigh-molecular-weight polyethylene, highly cross-linked, and highly cross-linked with vitamin E versions. The scratching significantly increased friction and doubled the wear of all groups. Before scratching, friction levels for the aforementioned plastic groups were 0.056 ± 0.0060, 0.062 ± 0.0080, and 0.070 ± 0.0045, respectively, but after scratching increased to 0.088 ± 0.018, 0.076 ± 0.0066, and 0.082 ± 0.0049, respectively, all statistically significant increases (p = 0.00059, 0.00005, 0.0115, respectively). In another test series of 44-mm femoral head diameter hips, metal-on-plastic hips with conventional ultrahigh-molecular-weight polyethylene showed the lowest friction at 0.045 ± 0.0085, followed by highly cross-linked with 0.046 ± 0.0035 (not significantly different). In a ceramic-on-plastic design with conventional ultrahigh-molecular-weight polyethylene, higher friction 0.079 ± 0.0070 was measured likely due to that ceramic surface being rougher than usual. Metal-on-metal hips were compared without and with a TiN coating, resulting in 0.049 ± 0.014 and 0.097 ± 0.020 friction factors, respectively (statistically significant, p < 0.001), and the coating wore away on all coated hips eventually. Higher friction mostly correlated with higher wear or damage to femoral heads or implant coatings, except for the highly cross-linked wear resistant ultrahigh-molecular-weight polyethylene which had slightly higher friction, confirming the same finding in other independent studies. This type of friction measurements can help screen for clamping and elevated wear of metal-on-metal and resurfacing total hip replacements, surgical malpositioning, and abraded and otherwise damaged surfaces.

Chemistry-driven structural alterations in short-term retrieved ceramic-on-metal hip implants: Evidence for in vivo incompatibility between ceramic and metal counterparts

Ceramic-on-metal (CoM) hip implants were reported to experience lower wear rates in vitro as compared to metal-on-metal (MoM) bearings, thus hinting metal-ion release at lower levels in vivo. In this article, we show a spectroscopic study of two short-term retrieval cases of zirconia-toughened alumina (ZTA) femoral heads belonging to CoM hip prostheses, which instead showed poor wear performances in vivo. Metal contamination and abnormally high fractions of tetragonal-to-monoclinic (t→m) polymorphic transformation of the zirconia phase could be found on both ZTA heads, which contrasted with the optimistic predictions of in vitro experiments. At the molecular scale, incorporation of metal ions into the ceramic lattices could be recognized as due to frictionally assisted phenomena occurring at the ceramic surface. Driven by abnormal friction, diffusion of metal ions induced lattice shrinkage in the zirconia phases, while residual stress fields became stored at the surface of the femoral head. Diffusional alterations destabilized the chemistry of the ceramic surface and resulted in an abnormal increase in t→m phase transformation in vivo. Frictionally driven metal transfer to the ceramic lattice thus hinders the in vivo performance of CoM prostheses. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1469-1480, 2017.

Clinical Results and Metal Ion Levels After Ceramic-on-Metal Total Hip Arthroplasty: A Mean 50-Month Prospective Single-Center Study

BACKGROUND

The aim of our study was to investigate the clinical results and serum metal ion levels in a cohort of patients who received total hip arthroplasty (THA) with ceramic-on-metal (CoM) bearings.

METHODS

From September 2009 to December 2011, 78 patients (89 hips) who underwent THA with CoM bearings were involved in this study. Harris Hip Score, Short-Form 12, and Western Ontario and McMaster Universities Osteoarthritis Index scores were measured and radiographs were taken for radiographic analysis. Serum metal ion levels of cobalt (Co), chromium (Cr), molybdenum (Mo), and titanium (Ti) were measured using high-resolution inductively coupled plasma-mass spectrometry.

RESULTS

Severy-four patients (85 hips) were followed up at a mean of 50 months. At the end of follow-up, HSS, Short-Form 12, and Western Ontario and McMaster Universities Osteoarthritis Index scores were improved significantly compared with preoperative values. No intraoperative and postoperative complications occurred, and no radiolucency, osteolysis, and loosening was found from radiographic examination. Metal ion analysis showed that serum metal ions levels were significantly elevated compared with normal values. Spearman correlation analysis revealed that there was a correlation between 3 metal ion levels and body mass index(Co: r = 0.49, P < .01; Cr: r = 0.47, P < .01; Mo: r = 0.36, P = .04). No correlation was found between metal ion levels and age, cup abduction angle, cup anteversion angle, acetabular version, bilateral arthroplasty, cup screw used, hip stem implant type, or femoral head size.

CONCLUSION

Our study concluded that the use of a CoM THA is effective clinically, but the systemic metal ion levels are significantly elevated at midterm follow-up. Whether the elevated metal ion levels will induce an adverse reaction is unknown and long-term follow-up is need.

No Difference in Reoperations at 2 Years Between Ceramic-on-metal and Metal-on-metal THA: A Randomized Trial

BACKGROUND

Hard-on-hard bearings for total hip arthroplasty continue to warrant analysis even though crosslinked polyethylene is performing very well. Ceramic-on-metal (CoM) has low in vitro wear and did well in an early clinical trial. We report on a prospective, randomized, multicenter investigational device trial comparing CoM with metal-on-metal (MoM).

QUESTIONS/PURPOSES

(1) Is there a difference in the number or type of revisions comparing CoM with MoM? (2) Are cobalt and chromium metal levels different for CoM and MoM THA?

METHODS

Between August 2005 and October 2006, of 1015 patients screened, 390 patients were enrolled at 11 centers and randomized to 194 CoM and 196 MoM bearings. There was no difference in the preoperative patient demographics between the study groups. Mean followup was 50 months (range, 22-75 months). Seventy-two patients from two centers had metal level analysis.

RESULTS

With the numbers available, there was no difference in the proportion of patients undergoing revisions between the MoM and the CoM cohorts (MOM: 3% [six of 196]; COM: 1.5% [three of 194]; p = 0.50). Four MoM revisions were unrelated to the bearing surface. Two had bearing surface-related reoperations, one for an aseptic lymphocyte-dominated vasculitis-associated lesion and one for elevated metal levels with acetabular malposition. None of the CoM revisions were related to the bearing surface. The metal level analysis revealed that in contrast to the CoM, the MoM bearing group had increasing values of erythrocyte and serum cobalt from 1 to 5 years (CoM erythrocyte 0.45-0.55 ppb, p = 0.11 and CoM serum 0.88-0.85, p = 0.55, and MoM erythrocyte 0.32-0.51 ppb, p < 0.01 and MoM serum 0.65-1.01 ppb, p < 0.01). In addition, the MoM cobalt levels in erythrocytes and serum at 5 years were more variable than at 1 year (erythrocyte interquartile range [IQR], 0.26-0.44 to 0.31-1.21 ppb and serum IQR, 0.42-0.80 to 0.64-2.20 ppb, p < 0.02 for both).

CONCLUSIONS

Although both bearings performed well at short-term followup, the CoM bearing group had no wear-related revisions and maintained consistently low metal levels. The MoM cobalt elevations may be important considering recent reports of taper corrosion. This CoM bearing was approved by the FDA but withdrawn from the market because of low sales. If it were available, the authors would not use CoM until long-term data were available. The bearing would have to outperform crosslinked polyethylene because it is unlikely that CoM metal levels will return to normal.

LEVEL OF EVIDENCE

Level I, therapeutic study.

A prospective study of ceramic-on-metal bearings in total hip arthroplasty at four-year follow-up: clinical results, metal ion levels, inflammatory factor levels, and liver-kidney function

BACKGROUND

Despite the theoretical advantages of ceramic-on-metal (CoM) bearings observed in laboratory settings, limited clinical data are available to support in vitro results. Our present study prospectively investigated the clinical results, serum metal ion levels, inflammatory factor levels, and liver-kidney function in a cohort of patients who received total hip arthroplasty (THA) with CoM bearings.

METHODS

The cohort comprised 82 THAs in 71 patients (41 men and 30 women), with a mean age of 54 (range 22-77) years. The mean follow-up was four years. All patients completed pre- and postoperative clinical assessment using the Harris Hip Score, Short Form-12, Western Ontario and McMaster Universities Osteoarthritis Index, and radiographic analysis. The serum metal ion levels of cobalt, chromium, molybdenum, and titanium were measured using high-resolution inductively coupled plasma mass spectrometry, and were compared with normal reference values. Inflammatory factors including C-reactive protein, erythrocyte sedimentation, and interleukin-6 levels, and liver-kidney function including alanine aminotransferase, aspartate aminotransferase, total bilirubin, creatinine, and blood urea nitrogen, were measured in our hospital clinical key laboratory.

RESULTS

At the end of the follow-up period, all clinical assessments showed a statistically significant improvement. Although the inflammatory factor levels and liver-kidney function were within normal ranges, the serum levels of metal ion were significantly elevated compared with normal values: cobalt, 2.8 μg/L; chromium, 2.2 μg/L; molybdenum, 0.9 μg/L; and titanium, 2.1 μg/L. Spearman's correlation analysis showed an association between cobalt, chromium, and titanium metal ion levels and BMI values.

CONCLUSIONS

Our study demonstrated that the use of a CoM THA was clinically effective and that metal ion levels were significantly elevated at midterm follow-up. Whether the elevated metal ion levels may reduce adverse reactions is unknown, and long-term follow-up is needed.

Adverse reaction to metal debris in a patient with acetabular shell loosening 8 years after ceramic-on-metal total hip arthroplasty

A 41-year-old woman presented 8 years after a left total hip arthroplasty. She complained of progressive groin pain for several months. Radiographs demonstrated a hard-on-hard bearing surface combination and radiolucent lines surrounding the acetabular shell. Laboratory analysis revealed a mild leukocytosis, a normal erythrocyte sedimentation rate, and a mildly elevated C-reactive protein. Serum cobalt and chromium levels were markedly elevated. Aspiration of the hip joint was negative for infection. Magnetic resonance imaging failed to demonstrate a pseudotumor. Revision total hip arthroplasty was performed, and a ceramic-on-metal bearing surface combination was explanted. Significant intraoperative findings included dark gray synovial fluid, metal transfer onto the ceramic femoral head, and a grossly loose acetabular shell pivoting about a single well-fixed screw. The explanted components otherwise appeared normal macroscopically. Histologic analysis of the capsular tissue demonstrated aseptic lymphocyte-dominated vasculitis-associated lesion and inclusion bodies consistent with third-body wear. Revision arthroplasty to a ceramic-on-polyethylene bearing surface combination was performed with a good clinical result and laboratory normalization at 9-month follow-up.

The current state of bearing surfaces in total hip replacement

We reviewed the literature on the currently available choices of bearing surface in total hip replacement (THR). We present a detailed description of the properties of articulating surfaces review the understanding of the advantages and disadvantages of existing bearing couples. Recent technological developments in the field of polyethylene and ceramics have altered the risk of fracture and the rate of wear, although the use of metal-on-metal bearings has largely fallen out of favour, owing to concerns about reactions to metal debris. As expected, all bearing surface combinations have advantages and disadvantages. A patient-based approach is recommended, balancing the risks of different options against an individual’s functional demands.

Cite this article: Bone Joint J 2014;96-B:147–56.

Wear performance of ceramic-on-metal hip bearings

Ceramic-on-metal (CoM) bearings are considered to be a promising alternative to polyethylene-based bearings or hard-on-hard bearings (Ceramic-on-Ceramic (CoC) and Metal-on-Metal (MoM)). Although, CoM shows lower wear rates than MoM, in-vitro wear testing of CoM shows widely varying results. This may be related to limitations of wear-measuring methods. Therefore, the aim of this study was to improve the gravimetric measurement technique and to test wear behaviour of CoM bearings compared to CoC bearings. Level walking according to ISO-14242 was simulated for four CoM and four CoC bearings. Prior to simulation, errors in measurement of gravimetric wear were detected and improvements in measurement technique incorporated. The results showed no differences in mean wear rates between CoM and CoC bearings. However, the CoM bearings showed wear results over a wide range of wear performance. High reliability of wear results was recorded for the CoC bearings. Material transfer was observed on the ceramic heads of the CoM bearings. Therefore, for level walking a partial mixed or boundary lubrication has to be assumed for this type of bearing. CoM is a highly sensitive wear-couple. The reasons for the observed behaviour cannot be clarified from this study. Simulator studies have to be considered as an ideal loading condition. Therefore, high variations in wear rates as seen in this study, even at low levels, may have an adverse effect on the in-vivo wear behavior. Careful clinical use may be advisable until the reasons for the variation are fully clarified and understood.

A prospective study of a ceramic-on-metal bearing in total hip arthroplasty

We prospectively assessed the efficacy of a ceramic-on-metal (CoM) hip bearing with uncemented acetabular and femoral components in which cobalt­–chrome acetabular liners and alumina ceramic heads were used.

The cohort comprised 94 total hip replacements (THRs) in 83 patients (38 women and 45 men) with a mean age of 58 years (42 to 70). Minimum follow-up was two years. All patients had pre- and post-operative assessment using the Western Ontario and McMaster Universities osteoarthritis index (WOMAC), Oxford hip score and Short-Form 12 scores. All showed a statistically significant improvement from three months post-operatively onwards (all p < 0.001).

After two years whole blood metal ion levels were measured and chromosomal analysis was performed. The levels of all metal ions were elevated except vanadium. Levels of chromium, cobalt, molybdenum and titanium were significantly higher in patients who underwent bilateral THR compared with those undergoing unilateral THR (p < 0.001). Chromosomal analysis demonstrated both structural and aneuploidy mutations. There were significantly more breaks and losses than in the normal population (p < 0.001). There was no significant difference in chromosomal aberration between those undergoing unilateral and bilateral procedures (all analyses p ≥ 0.62).

The use of a CoM THR is effective clinically in the short-term, with no concerns, but the significance of high metal ion levels and chromosomal aberrations in the long-term remains unclear.

Cite this article: Bone Joint J 2013;95-B:1040–44.

Clinical failure analysis of contemporary ceramic-on-ceramic total hip replacements

The present study investigates the performance of ceramic-on-ceramic total hip replacements by combining a retrieval analysis with a survivorship analysis to elucidate mechanisms that led to clinical failure. Semiquantitative surface damage assessment, contact profilometry, contour measurements, and scanning electron microscopy were performed to characterize the types and quantify the extent of surface damage on the retrieved ceramic components. The implantation period was positively correlated with both damage scores of the femoral heads (R = 0.573, p < 0.001) and the acetabular cups (R = 0.592, p < 0.001). Increased maximal out-of-roundness values of the femoral heads correlated with both increased metal transfer damage score (R = 0.384, p = 0.023) and increased stripe damage score (R = 0.729, p ≤ 0.001) of the acetabular liners. The damage rate (damage score/year) for both the retrieved heads and acetabular liners was at least 2.2-fold greater at inclination angles of >45° than the damage rate at inclination angles of ≤45°. For the retrieved femoral heads only, the linear wear rate of 25.5 ± 21.3 µm/year at inclination angles of >45° was 6-fold greater than the linear wear rate of 4.2 ± 2.3 µm/year at inclination angles of ≤45°. Metal transfer on the ceramic bearing surface could possibly contribute to fluid-film starvation and, in combination with an increased inclination angle, may facilitate an adhesive wear mechanism associated with stripe surface damage. At our institution, the clinical survivorship of ceramic-on-ceramic total hip replacements was 98.9% (a total of 9 out of 815 patients were revised within 10 years after total hip arthroplasty) with revision as the end point, suggesting their safe use in younger patients.

A prospective, randomised controlled trial comparing ceramic-on-metal and metal-on-metal bearing surfaces in total hip replacement

In a double-blinded randomised controlled trial, 83 patients with primary osteoarthritis of the hip received either a ceramic-on-metal (CoM) or metal-on-metal (MoM) total hip replacement (THR). The implants differed only in the bearing surfaces used. The serum levels of cobalt and chromium and functional outcome scores were compared pre-operatively and at six and 12 months post-operatively. Data were available for 41 CoM and 36 MoM THRs (four patients were lost to follow-up, two received incorrect implants). The baseline characteristics of both cohorts were similar. Femoral head size measured 36 mm in all but two patients who had 28 mm heads. The mean serum cobalt and chromium levels increased in both groups, with no difference noted between groups at six months (cobalt p = 0.67, chromium p = 0.87) and 12 months (cobalt p = 0.76, chromium p = 0.76) post-operatively. Similarly, the mean Oxford hip scores, Western Ontario and McMaster Universities Osteoarthritis index and University of California, Los Angeles activity scores showed comparable improvement at 12 months. Our findings indicate that CoM and MoM couplings are associated with an equivalent increase in serum cobalt and chromium levels, and comparable functional outcome scores at six and 12-months follow-up.

Effect of femoral head size on the wear of metal on metal bearings in total hip replacements under adverse edge-loading conditions

Metal-on-metal (MoM) bearings have shown low-wear rates under standard hip simulator conditions; however, retrieval studies have shown large variations in wear rates and mechanisms. High-wear in vivo has caused catastrophic complications and has been associated with steep cup-inclination angle (rotational malpositioning). However, increasing the cup-inclination angle in vitro has not replicated the increases in wear to the same extent as those observed in retrievals. Clinically relevant wear rates, patterns, and particles were observed in vitro for ceramic-on-ceramic bearings when microseparation (translational malpositioning) conditions were introduced into the gait cycle. In the present study, 28 and 36-mm MoM bearings were investigated under adverse conditions. Increasing the cup angle from 45° to 65° resulted in a significant increase in the wear rate of the 28 mm bearings. However, for the 36 mm bearings, head-rim contact did not occur under the steep cup-angle condition, and the wear rate did not increase. The introduction of microseparation to the gait cycle significantly increased the wear rate of the MoM bearings. Cup angle and head size did not influence the wear rate under microseparation conditions. This study indicated that high-in vivo wear rates were associated with edge loading due to rotational malpositioning such as high-cup-inclination angle and translational malpositioning that could occur due to several surgical factors. Translational malpositioning had a more dominant effect on the wear rate. Preclinical simulation testing should be undertaken with translational and rotational malpositioning conditions as well as standard walking cycle conditions defined by the ISO standard.

Pulsed plasma deposition of zirconia thin films on UHMWPE: proof of concept of a novel approach for joint prosthetic implants

Wear of ultra-high molecular weight polyethylene (UHMWPE) has been recognized as the main cause for long-term revision in joint arthroplasty. A new approach to overcome this detrimental issue is here presented: zirconia (ZrO₂) thin films were directly deposited onto the surface of UHMWPE by Pulsed Plasma Deposition (PPD) technique. The obtained films were structurally, morphologically and mechanically characterized by X-ray diffraction, scanning electron microscopy and nanoindentation tests, respectively. The critical fracture load was estimated by the analysis of the indenter footprints, while the adhesion degree was evaluated by a cross-cut tape test. Zirconia films exhibited a fully cubic structure, with densely packed grains, whereas mechanical tests showed that hard, tough and well-adherent films were deposited. These preliminary results suggested the feasibility of pursuing this alternative route to improve UHMPWE performances while preserving its well-established mechanical properties.

Advantages and disadvantages of ceramic on ceramic total hip arthroplasty: a review

BACKGROUND

Ceramic on ceramic (COC) total hip arthroplasty (THA) was developed to reduce wear debris and accordingly, the occurrence of osteolysis and aseptic loosening especially in younger patients. Based on the excellent tribological behavior of current COC bearings and the relatively low biological activity of ceramic particles, significant improvement in survivorship of these implants is expected.

METHODS

We used manual search to identify all relevant studies reporting clinical data on COC THAs in PubMed. The objective was to determine whether current COC THA offers a better clinical outcome and survivorship than non-COC THA.

RESULTS

Studies with early generation ceramic bearings yielded 68% to 84% mean survivorship at 20 years follow-up which is comparable with the survivorship of non-COC THAs. Studies on current ceramic bearings report a 10-year revision-free interval of 92% to 99%. These outcomes are comparable to the survivorship of the best non-COC THAs. However, there are still concerns regarding fracture of sandwich ceramic liners, squeaking, and impingement of the femoral neck on the rim of the ceramic liner leading to chipping, especially in younger and physically active patients.

CONCLUSION

Current COC THA leads to equivalent but not improved survivorship at 10 years follow-up in comparison to the best non-COC THA. Based on this review, we recommend that surgeons weigh the potential advantages and disadvantages of current COC THA in comparison to other bearing surfaces when considering young very active patients who are candidates for THA.

(iv) Enhancing the safety and reliability of joint replacement implants

A new Stratified Approach For Enhanced Reliability (SAFER) pre-clinical simulation testing of joint prostheses is presented in this article. The aim of this approach is preclinical systematic testing of wear performance in the much wider envelope of conditions found clinically rather than relying only on the standard testing conditions that are currently used. The approach includes variations in surgical delivery, variations in kinematics, variations in the patient population and degradation of the biomaterial properties. Clinical experience of existing prostheses has been used to validate the new in vitro methods.

What's next? Alternative materials for articulation in total joint replacement

The use of an artificial joint is always related to a certain amount of wear. Its biological effects, e.g., the osteolysis potential, are a function of the bulk material as well as its debris. Following comprehensive experiences with polyethylene (PE) wear, material science is tracking two ways to minimize the risk of a particle-induced aseptic implant loosening: (i) reduction of the PE debris by a low-wearing articulation partner; and (ii) replacement of the PE by other materials. Therefore, new ceramics (e.g., ZTA, Si(3)N(4)), as well as coatings (e.g., TiN, "diamond-like" carbon) and modifications of a bulk metal (e.g., oxidizes zirconium) or cushion bearings (polyurethane, hydrogels), are currently available for total joint replacements or have been used for pre-clinical testing. This review gives a brief overview and evaluates the potential of those that have recently been published in literature.

State of the art in hard-on-hard bearings: how did we get here and what have we achieved?

Total hip arthroplasty has shown excellent results in decreasing pain and improving function in patients with degenerative disease of the hip. Improvements in prosthetic materials, designs and implant fixation have now resulted in wear of the bearing surface being the limitation of this technology, and a number of hard-on-hard couples have been introduced to address this concern. The purpose of this article is to review the origins, development, survival rates and potential advantages and disadvantages of the following hard-on-hard bearings for total hip arthroplasty: metal-on-metal standard total hip arthroplasty; metal-on-metal hip resurfacing arthroplasty, ceramic-on-ceramic total hip arthroplasty; and ceramic-on-metal bearings. Improvements in the manufacturing of metal-on-metal bearings over the past 50 years have resulted in implants that provide low wear rates and allow for the use of large femoral heads. However, concerns remain regarding elevated serum metal ion levels, potential teratogenic effects and potentially devastating adverse local tissue reactions, whose incidence and pathogenesis remains unclear. Modern total hip resurfacing has shown excellent outcomes over 10 years in the hands of experienced surgeons. Current ceramic-on-ceramic bearings have demonstrated excellent survival with exceptionally low wear rates and virtually no local adverse effects. Concerns remain for insertional chipping, in vivo fracture and the variable incidence of squeaking. Contemporary ceramic-on-metal interfaces are in the early stages of clinical use, with little data reported to date. Hard-on-hard bearings for total hip arthroplasty have improved dramatically over the past 50 years. As bearing designs continue to improve with new and modified materials and improved manufacturing techniques, it is likely that the use of hard-on-hard bearings will continue to increase, especially in young and active patients.

Hip replacement in the athlete: is there a role?

Sport and total hip arthroplasty (THA) have been regarded by many as being mutually exclusive. The primary indication for hip arthroplasty has always been pain. With advances in the technology surrounding hip replacement surgery and increasing patient expectations of what THA can offer, there is a growing demand for hip replacement with the aim of returning to sporting activity. The aim of this review article is to report the advances in hip replacement surgery that aim to make the procedure more suitable for the sporting individual and to summarise the literature on the subject of returning to sports after THA.

Wear and surface analysis of 38 mm ceramic-on-metal total hip replacements under standard and severe wear testing conditions

The purpose of this study was to compare the wear of zirconia-toughened alumina (ZTA) and alumina femoral heads tested against as-cast CoCrMo alloy acetabular cups under both standard and severe wear conditions. A new severe test, which included medio-lateral displacement of the head and rim impact upon relocation, was developed. This resulted in an area of metal transfer and an area of increased wear on the superior-anterior segment of the head that were thought to be due to dislocation and rim impact respectively. While the wear of all ceramic heads was immeasurable using the gravimetric method, the wear rates for the metallic cups from each test were readily calculated. An average steady state wear rate of 0.023 ± 0.005 mm3/106 cycles was found for the cups articulating against ZTA under standard wear conditions. A similar result had previously been obtained for the wear of cups articulated against alumina heads of the same size (within the same laboratory). Under severe wear conditions an increase in the metallic cup steady state wear rate was found with the ZTA and alumina tests giving 0.623 ± 0.252 and 1.35 ± 0.154 mm3/106 cycles respectively. Wear of the ceramic heads was detected using atomic force microscopy which showed, under severe wear conditions, a decrease in polishing marks and occasional grain removal. The surfaces of the ZTA heads tested under standard conditions were virtually unchanged from the unworn samples. Friction tests showed low friction factors for all components, pre and post wear.

The future of hip resurfacing

With experience in metal-metal resurfacing, several opportunities to improve resurfacing technology have been identified. There is a need for better education on hip resurfacing in residency training programs. The majority of short-term complications associated with resurfacing are related to surgical technique or component position. Innovations to improve acetabular component position and femoral-acetabular mating are needed. Although the majority of high wear and adverse local tissue reactions (ALTR) can be prevented by proper component positioning, the variable exposure to metal particles and ions associated with metal-metal resurfacing components continues to be a concern and bearing surface technology will evolve.

Serum metal ion levels after second-generation metal-on-metal total hip arthroplasty

INTRODUCTION

Metal-on-metal bearings for total hip arthroplasty are increasing in popularity. However, metal ion toxicity, metal hypersensitivity, and metal carcinogenicity are the causes concern for patients with metal-on-metal hip replacement. We investigated serum levels of cobalt and chromium ions in patients with successfully implanted second-generation metal-on-metal total hip arthroplasty (THA) using PINNACLE-A (DePuy, Warsaw, IN, USA).

MATERIALS AND METHODS

Thirty-three patients underwent primary cementless THA with the use of a 36-mm femoral head PINNACLE-A with a metal-on-metal articulation. Blood samples were taken preoperatively, at 3 months, and at 1 year, and levels of cobalt and chromium were determined.

RESULTS

At 3 months, levels of both cobalt and chromium had increased significantly compared with preoperative levels. There were no significant differences between levels of either metal at 3 months and 1 year.

CONCLUSION

Patients with metal-on-metal THA had higher circulating levels of metal ions than before arthroplasty at 3 months, with no additional significant increases at 1 year in this study.

Evaluating antimicrobials and implant materials for infection prevention around transcutaneous osseointegrated implants in a rabbit model

Transcutaneous osseointegrated implants can improve function for select amputee patients, but infection serves as a significant limitation of implantable transcutaneous devices. This study examined the efficacy of an antimicrobial, pexiganan acetate (SUPONEX), and a porous tantalum implant material (Trabecular Metal) in preventing pin tract infection of osseointegrated implants in a rabbit model. Thirty-seven rabbits were randomized to three groups: Ti-control group (n = 11) with titanium alloy implant and no antimicrobial, Ti-Pexiganan group (n = 8) with titanium alloy implant and topical pexiganan acetate 1% applied daily at the skin/implant interface, and Ta-control group (n = 18) with porous tantalum implant and no antimicrobial. All implants were placed transcutaneously through skin, muscle, and bone. Rabbits were monitored for infection for 24 weeks. We observed a 75% reduction in rates of pin tract infection in the Ti-Pexiganan group compared to that observed in the Ti-control group (p = 0.019). No difference in rates of infection was observed between the Ta-control group and the Ti-control group (p = 0.230). In conclusion, pexiganan acetate may be an important antimicrobial for transcutaneous osseointegrated implants. Porous tantalum will not likely prevent pin tract infection without additional methods of soft tissue immobilization around the implant site.

Metal ions levels measurments for early total hip replacement malfunction diagnosis with "plasma-sprayed ceramic" bearings couple

Diagnosis of total hip arthroplasty malfunction is usually based on clinical and radiographic findings, while metal ion blood levels monitoring is generally recommended for metal-on-metal bearings hip replacements. However, these measurements may be very useful in detecting anomalies in other bearing surfaces such as plasma sprayed ceramic bearings. We report on the case of a patient with a painful cementless ceramic-on-ceramic total hip prosthesis (Plasmaceram) for which metal ions blood levels suggested revision surgery in the absence of any demonstrable radiographic anomaly. The high Cobalt and moderate Chromium ion levels in blood suggested a mechanical dysfunction of the bearing couple which revealed to be a severe cam effect requiring revision surgery of both components. Measurement of metal ion blood levels may play a substantial role in the assessment of a total hip prosthesis mechanism when using another bearing surface than metal-on-metal for which this measurement is usually recommended.

The fundamentals of biotribology and its application to spine arthroplasty

The biological effect of wear of articulating surfaces is a continued concern with large joint replacements and, likewise, of interest for total disc replacements. There are a number of important biotribological testing parameters that can greatly affect the outcome of a wear study in addition to the implant design and material selection. The current ASTM and ISO wear testing standards/guides for spine arthroplasty leave many choices as testing parameters. These factors include but are not limited to the sequence of kinematics and load, phasing, type of lubricant, and specimen preparation (sterilization and artificial aging). The spinal community should critically assess wear studies and be cognizant of the influence of the selected parameters on the test results.

Integrated friction measurements in hip wear simulations: Short-term results

Hip joint wear simulators are used extensively to simulate the dynamic behaviour of the human hip joint and, through the wear rate, gain a concrete indicator about the overall wear performance of different coupled bearings. Present knowledge of the dynamic behaviour of important concurrent indicators, such as the coefficient of friction, could prove helpful for the continuing improvement in applied biomaterials. A limited number of commercial or custom-made simulators have been designed specifically for friction studies but always separately from wear tests; thus, analysis of these two important parameters has remained unconnected. As a result, a new friction sensor has been designed, built, and integrated in a commercial biaxial rocking motion hip simulator. The aim of this study is to verify the feasibility of an experimental set-up in which the dynamic measurement of the friction factor could effectively be implemented in a standard wear test without compromising its general accuracy and repeatability. A short wear test was run with the new set-up for 1×106 cycles. In particular, three soft-bearings (metal-on-polyethylene, Φ = 28 mm) were tested; during the whole test, axial load and frictional torque about the vertical loading axis were synchronously recorded in order to calculate the friction factor. Additional analyses were performed on the specimens, before and after the test, in order to verify the accuracy of the wear test. The average friction factor was 0.110 ± 0.025. The friction sensors showed good accuracy and repeatability throughout. This innovative set-up was able to reproduce stable and reliable measurements. The results obtained encourage further investigations of this set-up for long-term assessment and using different combinations of materials.

Ceramic-on-metal bearings in total hip replacement: whole blood metal ion levels and analysis of retrieved components

This study reports on ceramic-on-metal (CoM) bearings in total hip replacement. Whole blood metal ion levels were measured. The median increase in chromium and cobalt at 12 months was 0.08 microg/1 and 0.22 microg/1, respectively, in CoM bearings. Comparable values for metal-on-metal (MoM) were 0.48 microg/1 and 0.32 microg/1. The chromium levels were significantly lower in CoM than in MoM bearings (p = 0.02). The cobalt levels were lower, but the difference was not significant. Examination of two explanted ceramic heads revealed areas of thin metal transfer. CoM bearings (one explanted head and acetabular component, one explanted head and new acetabular component, and three new heads and acetabular components) were tested in a hip joint simulator. The explanted head and acetabular component had higher bedding-in. However, after one million cycles all the wear rates were the same and an order of magnitude less than that reported for MoM bearings. There were four outliers in each clinical group, primarily related to component malposition.

Tribological and surface analysis of 38mm alumina–as-cast Co–Cr–Mo total hip arthroplasties

There is currently much discussion over the use of ceramic femoral components against metal acetabular cups, for use in total hip arthroplasty. The current study investigates six hot isostatically pressed alumina femoral heads of 38 mm diameter articulating against six as-cast Co—Cr—Mo metallic acetabular cups. Standard walking-cycle simulator wear testing was carried out to 5×106 cycles using the Durham Mark II hip wear simulator, and wear was determined gravimetrically. In addition, surface topography, using a non-contacting profilometer, an atomic force microscope, and an optical microscope, was monitored throughout the wear test. The wear of the ceramic heads was found to be undetectable using the current gravimetric method; however, a change in the surface topography was seen, as grain removal on the pole was observed through atomic force microscopy analysis. A biphasic wear pattern was found for the metallic cups, with low wear rates of 1.04 ± 0.293 mm3/106 cycles (mean, ±95 per cent confidence interval) and 0.0209 ± 0.004 mm3/106 cycles (mean, ±95 per cent confidence interval) for running-in and steady state wear phases respectively. Frictional measurement revealed that the joints were tending towards full fluid-film lubrication in parts of the walking cycle. The results show that the combination of hot isostatically pressed alumina and as-cast Co—Cr—Mo is a promising alternative for total hip arthroplasties.