Wear performance of ceramic-on-metal hip bearings

METAL ION RELEASE ACCORDING TO LEG LENGTH DISCREPANCY IN CERAMIC-ON-METAL HIP ARTHROPLASTY

Objective

The ceramic-on-metal (CoM) bearing has the theoretical advantages over ceramic-on-ceramic (CoC) and metal-on-metal bearings. This study aimed to analyze factors affecting the metal ion release of CoM bearings and compare clinical performance with CoC bearings.

Methods

The 147 patients were divided into 96 patients in group 1 (CoM group) and 51 patients in group 2 (CoC group). Additionally, within group1, 48 patients and 30 patients were sub-categorized into group 1-A with leg length discrepancy (LLD) less than 1cm and group 1-B greater than 1 cm. The level of serum metal ions, functional scores and plain radiographs were obtained for the analysis.

Results

The level of cobalt (Co) 2-years after surgery and chromium (Cr) 1-year after surgery showed significantly higher in the group1 than the group2. LLD indicated statistically significant positive correlation between serum metal ion levels among CoM bearing THAs. In comparison of the average metal ions level changes, group 1-B showed higher level of metal ion than group 1-A.

Conclusion

In patients underwent THA with CoM bearings, large LLD have a higher risk of complications associated to metal ions. Therefore, it is critical to reduce the LLD to 1 cm or less in using CoM bearing. Level of Evidence III; Case Control Study.

BIOMECHANICAL ASSESSMENT OF WEAR IN CERAMIC ON CERAMIC AND CERAMIC ON XLPE THAs

Total Hip Arthroplasty (THA) is an effective treatment for severe hip arthritis, with patients reporting high rates of satisfactory results postoperatively. There are a variety of choices regarding THA implant designs. Ceramic on Ceramic and Ceramic on Highly Cross-Linked Polyethylene (XLPE) THAs are the materials of choice nowadays. The purpose of this study is to review the effect of kinematics and kinetics on wear (in vivo and in vitro testing) that affect wear in Ceramic on Ceramic and Ceramic on XLPE total hip arthroplasties and identify possible advantages amongst them. The study hypothesis was that THA kinematics and/or kinetics, since they directly affect THA wear, could provide data for possible advantages between the examined implant designs. A systematic review of the literature identified no significant evidence for biomechanical advantages between these two prostheses in terms of wear. Further research is proposed with the use of gait analysis systems combined with surface electromyography to further investigate THA biomechanics at a laboratory set up. Wearable sensors technology could also identify detailed biomechanical parameters in more complex daily activities.

Materials for Hip Prostheses: A Review of Wear and Loading Considerations

Replacement surgery of hip joint consists of the substitution of the joint with an implant able to recreate the articulation functionality. This article aims to review the current state of the art of the biomaterials used for hip implants. Hip implants can be realized with different combination of materials, such as metals, ceramics and polymers. In this review, we analyze, from international literature, the specific characteristics required for biomaterials used in hip joint arthroplasty, i.e., being biocompatible, resisting heavy stress, opposing low frictional forces to sliding and having a low wear rate. A commentary on the evolution and actual existing hip prostheses is proposed. We analyzed the scientific literature, collecting information on the material behavior and the human-body response to it. Particular attention has been given to the tribological behavior of the biomaterials, as friction and wear have been key aspects to improve as hip implants evolve. After more than 50 years of evolution, in term of designs and materials, the actual wear rate of the most common implants is low, allowing us to sensibly reduce the risk related to the widespread debris distribution in the human body.

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.

Wear of different materials for total hip replacement under adverse stop-dwell-start in vitro wear simulation conditions

Hip simulation is a common technique for pre-clinical evaluation of wear performance of total hip arthroplasty. Standard techniques replicate kinematics of walking patterns of a typical patient. Attention has focussed in developing simulations of other typical patient daily activities to improve accuracy of wear predictions. A method for simulating stop-dwell-start motion during patient walking and the effect on 36-mm metal-on-metal total hip arthroplasty was previously presented by the authors. This study sought to extend the previous work to look at the effect of these conditions on ceramic-on-ceramic, metal-on-polyethylene and ceramic-on-polyethylene bearings. Two stop-dwell-start protocols were used: one reproducing average patient movement patterns and one examining more severe conditions. For all materials tested, no significant increase in wear was observed under average stop-dwell-start conditions, suggesting the bearing types tested are robust to this type of activity. A significant increase in wear was observed for metal-on-metal, metal-on-polyethylene and ceramic-on-polyethylene bearings under severe stop-dwell-start conditions, this was attributed to depletion of lubricant in the bearing during the dwell period. A greater relative increase in wear was observed for metal-on-metal bearings compared with metal-on-polyethylene and ceramic-on-polyethylene bearings. This may be explained by the contributions of the different lubrication mechanisms in each bearing type. Wear of ceramic-on-ceramic was very low in all tests, suggesting normal measurement variation was masking any effect of the adverse conditions. It was not possible to determine any effect of the different activities. These results emphasise the importance of exploring adverse patient activity simulations. The increase in wear rate associated with an adverse activity such as seen in stop-dwell-start motion, has to be considered in the context of the frequency of the adverse activity cycle relative to other activities such as standard continuous walking, to determine the impact on the total wear in a given time period.

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.