A review of ceramic bearing materials in total joint arthroplasty

Tribo-corrosive behavior of additive manufactured parts for orthopaedic applications

Background

Additive manufacturing (AM) being an integral component of the production offers a wide variety of applications in the production of different components. The medical industry after the introduction of Additive Manufacturing has resulted in several advancements. The production of intricate patient-specific implants is one of such advancements which greatly assist a surgeon during a surgery. Orthopedic implants apart from possessing good mechanical strength are also expected to exhibit good tribological and corrosion behavior. As a result, the development of various orthopaedic implants and tools has become simple with the use of additive manufacturing.

Objectives and Rationale

In the current paper an effort has been made to discuss actual scientific knowledge on the tribo-corrosive behavior of additive manufactured parts for orthopedic applications. Different studies dealing with the mechanisms of lubrication and friction in synovial joints have also been considered. A special focus has also been laid down to study the corrosive effect of implants on the human body. A section dedicated to texturing of orthopedic implants has also been provided. The paper further elaborates the different research challenges and issues related to the use of additive manufacturing for the production of optimized orthopedic implants.

Conclusion

The study revealed that additive manufacturing has greatly aided in the manufacture of different orthopaedic implants with enhanced properties. However, a detailed study of the effect of processes like friction, wear, lubrication and corrosion in these implants needs to be done. The performance of these implants in the presence of various synovial fluids also needs to be addressed. However, the lack of more biocompatible materials, scalability and cost issues hinder the widespread use of AM in the different orthopaedic applications.

Long-Term Results of Alumina Ceramic-On-Ceramic Bearings in Cementless Total Hip Arthroplasty: A 20-Year Minimum Follow-Up

BACKGROUND

Alumina ceramic-on-ceramic bearings are used in total hip arthroplasty (THA) because of their wear-resistant and inert properties. In this study, we assessed the clinical and radiographic outcomes of patients undergoing primary cementless ceramic-on-ceramic THA at a minimum follow-up of 20 years.

METHODS

A series of 301 consecutive primary THAs in 283 patients were assessed. Clinically, patients were assessed with the modified Harris Hip Score (HHS) and pain questionnaires. Anteroposterior radiographs of the pelvis and lateral radiographs of the hip were used to radiologically assess the implant. Patients were classified as lost to follow-up if they could not be contacted on multiple occasions or did not wish to participate further in this study.

RESULTS

At twenty years after operation, 60 patients had died of a cause unrelated to surgery, 16 had experienced complications requiring reoperation, and 100 hips had both clinical assessments and radiographs at a minimum of 20 years of follow-up. The average HHS improved from 56.1 (range: 17-89) before THA to 92.5 (range: 63-100) at the latest follow-up. The classification of the HHS was good or excellent in 96.4% of patients. Only 1.8% of patients still had moderate residual pain at the thigh or groin. Radiographically, all patients demonstrated bony ingrowth but no clinical symptoms of loosening. The overall survival rate of the implants was 94.2% at 20 years with revision for any reason as the end point.

CONCLUSION

Long-Term follow-up in our series showed excellent implant survival, excellent functional outcomes, and minimal late complications. There was no significant radiographic evidence of failure at a minimum of 20 years after THA.

LEVEL OF EVIDENCE

Therapeutic Level IV.

Incidence, Risk Factors, and Outcome of Ceramic-On-Ceramic Bearing Breakage in Total Hip Arthroplasty

BACKGROUND

Ceramic-on-ceramic bearing breakage is a rare but significant complication of total hip arthroplasty. This study aimed to identify risk factors for breakage and to determine the outcome of different revision options.

METHODS

All ceramic-on-ceramic primary total hip arthroplasty procedures reported to the Australian Joint Replacement Registry from September 1999 to December 2019 were included. Procedures were subdivided into alumina or mixed ceramic (alumina/zirconia). All breakages were identified. The association between ceramic type and head size was assessed. Subsequent revision rates were compared and cause of revision assessed.

RESULTS

There were 23,534 alumina and 71,144 mixed ceramic procedures. Breakage was the reason for 1^st revision in 84 alumina (5.27% of all revisions and 0.36% of procedures) and 56 mixed ceramic procedures (2.46% of all revisions; 0.08% of procedures). Alumina had a higher breakage rate than mixed ceramic (HR 2.50 (95% CI 1.75, 3.59), P < .001), and breakage was higher for 36-38mm head sizes using alumina (HR 2.84 (1.52, 5.31), P = .001). 17.8% of 2^nd revisions occur by 3 years, due to dislocation, infection, metal-related pathology, and loosening. A neck adapter sleeve did not reduce 2^nd revisions. Numbers were too low to compare revision bearing surface options.

CONCLUSION

Ceramic breakage has reduced with mixed ceramics but has a 0.79/1000 incidence at 15-year follow-up. It is unclear what the risk factors are for modern ceramics with increasing head size a risk for alumina only. Risk of 2^nd revision is high and occurs early. The optimal revision option is unknown.

Development of hydrofluoric acid-cleaned silicon nitride implants for periprosthetic infection eradication and bone regeneration enhancement

Orthopedic implant is commonly associated with occurrence or relapse of osteomyelitis. This study developed a hydrofluoric acid (HF) cleaned silicon nitride (Si₃N₄) implant Si₃N₄_AC for osteomyelitis control and established a rat tibial osteomyelitis model to evaluate its efficacy on eradicating periprosthetic infection and enhancing bone regeneration. In vitro studies revealed Si₃N₄_AC had improved biocompatibility and inhibited Staphylococcus aureus adhesion. A custom-made Si₃N₄_AC implant was prepared and inserted into the rat tibia longitudinal cavity inoculated with Staphylococcus aureus. The in vivo bacteriostatic and osteogenic efficacies of Si₃N₄_AC implant were evaluated by histological, microbiological and Micro-CT analyses and compared with implants of pure Ti and Si₃N₄ . Si₃N₄_AC implant group revealed 99.5% inhibition of periprosthetic Staphylococcus aureus compared to the osteomyelitis group after 14 days post-operation. Implant-adhering bacteria density of Si₃N₄_AC was also much lower than pure Ti and Si₃N₄. In addition, micro-CT evaluation of peri-implant bone formation under the condition of periprosthetic osteomyelitis after 30 days post-surgery confirmed the osteogenic ability of Si₃N₄_AC. Taken together, Si₃N₄_AC can be an effective orthopedic biomaterial to eradicate periprosthetic infection and enhance bone regeneration.

Pushing Ceramic-on-Ceramic in the most extreme wear conditions: A hip simulator study

BACKGROUND

Hip revision surgery for fractured ceramic components may represent the worst-case wear scenario due to the high risks of recurrent dislocations, instability, and third body wear. The ideal bearing choice for the new prosthetic articulation is still subject of debate, while alumina matrix composite (AMC) articulations offer theoretical superior performances; the present work was designed to test the wear behaviour of ceramic on ceramic articulations (liner and head) in a worst-case scenario by adding ceramic third-body particles to the test lubricant with combined walking and subluxation cycles in a hip joint simulator. Therefore, we performed an in vitro study aiming to assess how does AMC articulation perform with 1) third-body particles added to the test environment and 2) under subluxation stresses.

HYPOTHESIS

We hypothesised that AMC articulations offer superior performances in such worst conditions.

MATERIALS AND METHODS

A hip simulator test was designed to analyse how AMC articulation performs with third-body particles added to the test environment and under subluxation stresses. Two different load patterns including level walking and subluxation of the ceramic liner were applied. The test fluid lubricant was contaminated by adding coarse ceramic particles during the first 2 million cycles and fine ceramic particles from 2 to 4 million cycles. Group 1 consisted of an alumina matrix composite articulation (liner and head); group 2 consisted of an alumina liner and an alumina matrix composite head. A control group consisting of an alumina ceramic liner articulated against an alumina matrix composite head was provided and only axially loaded. The liners of groups 1 and 2 were tested at an in vivo angle of 45° in the medial lateral plane (inclinationangle), which corresponds to an angle L=30° relative to the ISO standard fixated position used for in vitro testing. All mass measurements were performed using a high precision balance (Sartorius BP211D). During each examination, images on dedicated location of the bearing surfaces were taken using a digital microscope.

RESULTS

Mean cumulative wear of 0.09mg per million cycles between 2 and 4 million cycles was detected in group 2, and this value was significantly lower (p=0.016) in comparison with the average value in group 1 (0.21mg per million cycle). This result can be explained in light of a possible transformation phase of zirconia in AMC liners, probably due to excessive stress during subluxation cycles. However, wear levels observed are close to the gravimetric measurement detection limit of the Sartorious Balance (about 0.1-0.2mg); therefore, wear can be considered negligible in all groups.

CONCLUSION

Our results confirm that AMC couplings perform very well even in the worst-case wear scenario. Since AMC articulations revealed 25% lower cumulative wear respect to AMC on cross linked polyethylene in same simulator setup, AMC articulations should be considered the bearing of choice in revision surgery in light of the high risk of recurrent dislocations, instability, and third body wear.

LEVEL OF EVIDENCE

III, prospective case-control study, in vitro.

Early Short-Term Postoperative Mechanical Failures of Current Ceramic-on-Ceramic Bearing Total Hip Arthroplasties

Although ceramic-on-ceramic (CoC) bearings have been shown to produce the smallest amount of wear volume in vitro as well as in vivo studies when used for total hip arthroplasties (THA), concerns about the failure of these bearing surfaces persist due to early failures observed after short postoperative time. In this study, an exhaustive analysis of the early failure occurred on the new generation of ceramic bearings, consisting of a composite alumina matrix-based material reinforced with yttria-stabilized tetragonal zirconia (Y-TZP) particles, chromium dioxide, and strontium crystals, was performed. For this study, 118 CoC bearings from 117 patients were revised. This article describes a group of mechanical failure CoC-bearing BIOLOX THA hip prosthesis patients without trauma history. The retrieved samples were observed under scanning electron microscopy (SEM), composition was analyzed with energy dispersive X-ray spectroscopy (EDX), and damaged surfaces were analyzed by grazing-incidence X-ray diffraction (GI-XRD) and white light interferometry. In the short term, CoC articulations provided similar mechanical behavior and functional outcome to those in XLPE cases. However, 5% more early mechanical failures cases were observed for the ceramic components. Although the fracture rate of third generation CoC couples is low, the present study shows the need to further improve the third generation of CoC-bearing couples for THA. Despite the improved wear compared to other materials, stress concentrators are sources of initial crack propagation, such as those found in the bore-trunnion areas. Moreover, in view of the evidence observed in this study, the chipping observed was due to the presence of monoclinic phase of the Y-TZP instead of tetragonal, which presents better mechanical properties. The results showed that total safety after receiving a THA is still a goal to be pursued.

Synthesis and Tribological Properties of Bio-Inspired Nacre-Like Composites

Ceramic materials possessing the properties of high-strength and rigidity are widely used in industry. The shell nacre has a layered structure containing both macroscopic and microscopic levels and is equipped with superior qualities regarding hardness and strength. Therefore, the ceramic composites with a nacre-like layered structure have the potential to be utilized as sliding bearings employed in the harsh conditions of wells. For the purpose of this paper, a porous Al₂O₃ ceramics skeleton with nanometer powder is prepared using the freeze-casting method. Then the porous ceramic skeleton is filled with polymer polymethyl methacrylate (PMMA) through mass polymerization to produce a bionic Al₂O₃/PMMA composite with a lamellar structure. The properties of the prepared composite are determined by the analysis of micro-hardness, fracture toughness, friction coefficient, wear scar diameter, and the morphology of the worn surface. Consequent results indicate that elevation in the A1₂O₃ powder, which acts as the initial solid phase content, prompts the ceramic slurry to exhibit an increase in viscosity and a gradual decrease in the pore size of the ceramic skeleton. The prepared layered Al₂O₃/PMMA composite possesses high fracture toughness, which closely resembles that of Al, is approximately four times that of the matrix of the Al₂O₃ ceramics and 16 times that of the PMMA. Three kinds of composites containing different solid phase content are subjected to testing involving lubrication by water-based drilling fluid to determine the friction coefficient of each. The results indicate that an increased load leads to a decreased friction coefficient while the impact of speed is not evident. Under dry conditions, the friction coefficient of three different composites tested, declines with elevated load and speed. With the use of water-based drilling fluid as lubrication, the wear scar diameter increases at higher speed, while dry conditions denote increased load. Abrasive wear is determined to be the principal form of erosion of layered Al₂O₃/PMMA composites.

Do ceramic femoral heads reduce taper fretting corrosion in hip arthroplasty? A retrieval study

BACKGROUND

Previous studies regarding modular head-neck taper corrosion were largely based on cobalt chrome (CoCr) alloy femoral heads. Less is known about head-neck taper corrosion with ceramic femoral heads.

QUESTIONS/PURPOSES

We asked (1) whether ceramic heads resulted in less taper corrosion than CoCr heads; (2) what device and patient factors influence taper fretting corrosion; and (3) whether the mechanism of taper fretting corrosion in ceramic heads differs from that in CoCr heads.

METHODS

One hundred femoral head-stem pairs were analyzed for evidence of fretting and corrosion using a visual scoring technique based on the severity and extent of fretting and corrosion damage observed at the taper. A matched cohort design was used in which 50 ceramic head-stem pairs were matched with 50 CoCr head-stem pairs based on implantation time, lateral offset, stem design, and flexural rigidity.

RESULTS

Fretting and corrosion scores were lower for the stems in the ceramic head cohort (p=0.03). Stem alloy (p=0.004) and lower stem flexural rigidity (Spearman's rho=-0.32, p=0.02) predicted stem fretting and corrosion damage in the ceramic head cohort but not in the metal head cohort. The mechanism of mechanically assisted crevice corrosion was similar in both cohorts although in the case of ceramic femoral heads, only one of the two surfaces (the male metal taper) engaged in the oxide abrasion and repassivation process.

CONCLUSIONS

The results suggest that by using a ceramic femoral head, CoCr fretting and corrosion from the modular head-neck taper may be mitigated but not eliminated.

CLINICAL RELEVANCE

The findings of this study support further study of the role of ceramic heads in potentially reducing femoral taper corrosion.

Third-body abrasive wear of tibial polyethylene inserts combined with metallic and ceramic femoral components in a knee simulator study

AIM

Total knee arthroplasties have reached a high grade of quality and safety, but most often fail because of aseptic implant loosening caused by polyethylene wear debris. Wear is generated at the articulating surfaces, e.g. caused by third-body particles. The objective of this experimental study was to determine the wear of tibial polyethylene inserts combined with metallic and ceramic femoral components under third-body wear conditions initiated by bone cement particles.


METHODS AND MATERIALS

Wear testing using a cemented unconstrained bicondylar knee endoprosthesis (Multigen Plus CR knee system) was performed in a knee wear simulator. Tibial polyethylene inserts were combined with the identical femoral component design, but made of two different materials (cobalt-chromium and ceramic). Bone cement debris including zirconium oxide particles was added every 500,000 cycles between the articulating surfaces. After 5 million load cycles, the amount of wear was determined gravimetrically and compared with results from standard wear test conditions. The surfaces of tibial inserts were also analyzed.


RESULTS

The average gravimetrical wear of the tibial polyethylene inserts in combination with 
cobalt-chromium and ceramic femoral components under third-body wear conditions amounted to 31.88 ± 4.53 mg and 13.06 ± 1.88 mg after 5 million cycles, respectively, and was higher than under standard wear test conditions in both cases.


CONCLUSIONS

The wear simulator test demonstrates that wear of polyethylene inserts under third-body wear conditions, in combination with ceramic femoral components, was significantly lower than with metallic femoral components.

Risk factors for ceramic liner fracture after total hip arthroplasty

The aim of this study was to detect risk factors for ceramic liner fractures. 26 cementless ceramic on ceramic (COC) total hip arthroplasties (THA) revised because of ceramic liner fracture in 24 patients were compared with 49 well-functioning COC THA performed in 49 patients. Demographic parameters, type of ceramic of the liner, size and neck length of the femoral head, cup abduction angle, cup anteversion, femoral off-set, height of the centre of rotation and the incidence of noisy hips during follow-up examination were compared. A greater number of cups placed outside the optimal range of cup anteversion was found in the fracture group (p = 0.03). An audible noise was detected in 21 cases (80.7%) in the fracture group and in 3 cases (6.1%) in the non-fracture group (p = 0.001). A cup anteversion angle out of the optimal range of 15˚+/-10˚ was found to be a risk factor for ceramic liner fracture and the presence of a noisy hip frequently anticipated the failure. In our opinion neck-to-cup impingement with head subluxation and edge loading on the liner rim could have an important role in the onset of noise and subsequent liner failure, and cup malposition contributes to this mechanism of failure.

Fatal cardiomyopathy after revision total hip replacement for fracture of a ceramic liner

Symptomatic cobalt toxicity from a failed total hip replacement is a rare but devastating complication. It has been reported following revision of fractured ceramic components, as well as in patients with failed metal-on-metal articulations. Potential clinical findings include fatigue, weakness, hypothyroidism, cardiomyopathy, polycythaemia, visual and hearing impairment, cognitive dysfunction, and neuropathy. We report a case of an otherwise healthy 46-year-old patient, who developed progressively worsening symptoms of cobalt toxicity beginning approximately six months following synovectomy and revision of a fractured ceramic-on-ceramic total hip replacement to a metal-on-polyethylene bearing. The whole blood cobalt levels peaked at 6521 µg/l. The patient died from cobalt-induced cardiomyopathy. Implant retrieval analysis confirmed a loss of 28.3 g mass of the cobalt–chromium femoral head as a result of severe abrasive wear by ceramic particles embedded in the revision polyethylene liner. Autopsy findings were consistent with heavy metal-induced cardiomyopathy.

We recommend using new ceramics at revision to minimise the risk of wear-related cobalt toxicity following breakage of ceramic components.

Cite this article: Bone Joint J 2013;95-B:31–7.

Early fixation of cobalt-chromium based alloy surgical implants to bone using a tissue-engineering approach

To establish the methods of demonstrating early fixation of metal implants to bone, one side of a Cobalt-Chromium (CoCr) based alloy implant surface was seeded with rabbit marrow mesenchymal cells and the other side was left unseeded. The mesenchymal cells were further cultured in the presence of ascorbic acid, β-glycerophosphate and dexamethasone, resulting in the appearance of osteoblasts and bone matrix on the implant surface. Thus, we succeeded in generating tissue-engineered bone on one side of the CoCr implant. The CoCr implants were then implanted in rabbit bone defects. Three weeks after the implantation, evaluations of mechanical test, undecalcified histological section and electron microscope analysis were performed. Histological and electron microscope images of the tissue engineered surface exhibited abundant new bone formation. However, newly formed bone tissue was difficult to detect on the side without cell seeding. In the mechanical test, the mean values of pull-out forces were 77.15 N and 44.94 N for the tissue-engineered and non-cell-seeded surfaces, respectively. These findings indicate early bone fixation of the tissue-engineered CoCr surface just three weeks after implantation.