Ceramic versus cobalt-chrome femoral components; wear of polyethylene insert in total knee prosthesis

Long term follow-up of a completely metal free total knee endoprosthesis in comparison to an identical metal counterpart

Aseptic loosening is a feared and not yet fully-understood complication of total knee arthroplasty (TKA). Hypersensitivity reactions may be the underlying cause within some susceptible patients. Metal-free implants have been developed as a possible solution. The aim of this prospective, observational long-term study was the assessment of a completely metal-free ceramic knee replacement system compared to its identical metal counterpart 8 years after implantation, conducted as a follow-up of a previous report. A total of 88 patients (mean age 69 years) were enrolled in this prospective, observational long-term 8-year follow-up study. The "ceramic group" with a completely metal-free total knee replacement system was compared to the "conventional group" with an identical metal TKA system at the final follow-up. Clinical assessment included Knee Society Score (KSS), Oxford Knee Score (OKS), European Quality of Life 5 Dimensions 3 Level Version (EQ-5D-L), European Quality of Life 5 Dimension Visual Analogue Scale (EQ-VAS) and High Activity Arthroplasty Score (HAAS) as well as perioperative or postoperative complications and need for revision. The tibial/femoral positioning, signs of periprosthetic fissures/fractures or radiolucent lines were documented radiographically. All postoperative clinical scores in the ceramic group primarily improved from baseline to 4-year follow-up, but then decreased at the final 8-year follow-up. At the final follow-up, statistically non-significant differences were found in comparison of both groups for the KSS (ceramic: 166 ± 31, conventional: 162 ± 29; p > 0.05), OKS (ceramic: 37, conventional: 39; p > 0.05), EQ-VAS (ceramic: 77 ± 17, conventional: 72 ± 18; p > 0.05), and HAAS (ceramic: 8.29 ± 3.32, conventional: 9.28 ± 4.44; p > 0.05). A significant difference was found for EQ-5D-L (ceramic: 0.819 ± 0.284, conventional: 0.932 ± 0.126; p ≤ 0.05). Progressive radiolucent lines have been found around the uncemented tibial stem (0.8 mm at initial diagnosis (mean 19 months); 1.3 mm at 4-year follow-up; 1.6 mm at 8-year follow-up) without any clinical signs of loosening. One revision surgery was performed after a traumatic polyethylene inlay-breakage. No allergic reactions could be detected. The used ceramic TKA system meets the functional performance standards of an established identical metal TKA system after an 8-year follow-up period, offering a safe option for patients with prior hypersensitivity reactions to metallic materials. Full cementation of ceramic components is recommended.

Osteointegration of functionalised high-performance oxide ceramics: imaging from micro-computed tomography

BACKGROUND

This study evaluated the osseointegration potential of functionalised high-performance oxide ceramics (HPOC) in isolation or coated with BMP-2 or RGD peptides in 36 New Zeeland female rabbits using micro-computed tomography (micro CT). The primary outcomes of interest were to assess the amount of ossification evaluating the improvement in the bone volume/ total volume (BV/TV) ratio and trabecular thickness at 6 and 12 weeks. The second outcome of interest was to investigate possible differences in osteointegration between the functionalised silanised HPOC in isolation or coated with Bone Morphogenetic Protein 2 (BMP-2) or RGD peptides.

METHODS

36 adult female New Zealand white rabbits with a minimum weight of three kg were used. One-third of HPOCs were functionalised with silicon suboxide (SiOx), a third with BMP-2 (sHPOC-BMP2), and another third with RGD (sHPOC-RGD). All samples were scanned with a high-resolution micro CT (U-CTHR, MILabs B.V., Houten, The Netherlands) with a reconstructed voxel resolution of 10 µm. MicroCT scans were reconstructed in three planes and processed using Imalytics Preclinical version 2.1 (Gremse-IT GmbH, Aachen, Germany) software. The total volume (TV), bone volume (BV) and ratio BV/TV were calculated within the coating area.

RESULTS

BV/TV increased significantly from 6 to 12 weeks in all HPOCs: silanised (P = 0.01), BMP-2 (P < 0.0001), and RGD (P < 0.0001) groups. At 12 weeks, the BMP-2 groups demonstrated greater ossification in the RGD (P < 0.0001) and silanised (P = 0.008) groups. Trabecular thickness increased significantly from 6 to 12 weeks (P < 0.0001). At 12 weeks, BMP-2 promoted greater trabecular thickness compared to the silanised group (P = 0.07), although no difference was found with the RGD (P = 0.1) group.

CONCLUSION

Sinalised HPOC in isolation or functionalised with BMP-2 or RGD promotes in vivo osteointegration. The sinalised HOPC functionalised with BMP-2 demonstrated the greatest osseointegration.

Mid-term clinical outcomes of a posterior stabilized total knee prosthesis for Japanese patients: A minimum follow-up of 5 years

BACKGROUND

A high-flexion posterior-stabilized total knee prosthesis has been developed for the Asian population. The component design was based on computed tomography images of Japanese osteoarthritic knees. The femoral component is composed of zirconia ceramics, which exhibit low friction and high durability. The present study aimed to evaluate the mid-term clinical outcomes of this implant.

METHODS

This study included 334 knees of 210 patients who underwent primary total knee arthroplasty with this implant at our hospital between October 2010 and December 2014. The patients comprised 28 men and 172 women with an average age of 73 years. The average follow-up period was 5.9 years, and the follow-up rate was 71.1%. Clinical outcomes were assessed using the Knee Society scoring system, 2011 Knee Society questionnaire, and Knee Injury and Osteoarthritis Outcome Score. Kaplan-Meier survivorship analysis was performed to determine the cumulative prosthesis survival rate.

RESULTS

In terms of clinical outcomes at the final follow-up, the average ranges of motion were -2.0 in extension and 126.7 in flexion. The Knee Society knee and function scores were 94.2% and 72.6%, respectively. With revision surgery or radiographic failure for any reason as the endpoint, the survival rates at 5 and 9 years were 98.2% and 95.5%, respectively. The most common reason for revision surgery or radiological failure was aseptic loosening.

CONCLUSIONS

Despite several revision cases mainly due to aseptic loosening, the present study found that this new high-flexion posterior-stabilized total knee arthroplasty prosthesis design showed comparable results for Asian populations with other PS prosthesis.

LEVELS OF EVIDENCE

Level Ⅱ (Prospective cohort study).

Magnetic Resonance Safety Evaluation of a Novel Alumina Matrix Composite Ceramic Knee and Image Artifact Comparison to a Metal Knee Implant of Analogous Design

Background

Image artifacts caused by metal knee implants in 1.5T and 3T magnetic resonance imaging (MRI) systems complicate imaging-based diagnosis of the peri-implant region after total knee arthroplasty. Alternatively, metal-free knee prostheses could effectively minimize MRI safety hazards and offer the potential for higher quality diagnostic images.

Methods

A novel knee arthroplasty device composed of BIOLOX delta, an alumina matrix composite (AMC) ceramic, was tested in a magnetic resonance (MR) environment. American Society for Testing and Materials test methods were used for evaluating magnetically induced displacement force, magnetically induced torque, radiofrequency-induced heating, and MR image artifact.

Results

Magnetically induced displacement force and magnetically induced torque results of the AMC ceramic knee indicated that these effects do not pose a known risk in a clinical MR environment, as assessed in a 3T magnetic field. Moreover, minimal radiofrequency-induced heating of the device was observed. In addition, the AMC ceramic knee demonstrated minimal MR image artifacts (7 mm) in comparison to a cobalt-chromium knee (88 mm). The extremely low magnetic susceptibility of AMC (2 ppm) underlines that it is a nonmetallic and nonmagnetic material well suited for the manufacturing of MR Safe orthopaedic implants.

Conclusions

The AMC ceramic knee is a novel metal-free total knee arthroplasty device that can be regarded as MR Safe, as suggested by the absence of hazards from the exposure of this implant to a MR environment. The AMC ceramic knee presents the advantage of being scanned with superior imaging results in 3T MRI systems compared to alternative metal implants on the market.

A sustained release lubrication method of agarose-sodium hyaluronate hydrogels for artificial joint

The artificial joint prosthesis's surface is subjected to wear due to the destruction of the joint lubrication environment after surgery. In this study, an agarose-sodium hyaluronate hydrogel was used as lubricant additive in order to supply and preserve the lubricating fluid of artificial joint prostheses. A ball on disc experiment was conducted using this hydrogel to evaluate the lubrication efficiency and release rate under various frequencies. The results showed that this hydrogel could release lubricant under pressure and then absorb the released fluid after decompression. Furthermore, the agarose-sodium hyaluronate hydrogel acted as an effective transport mechanism to release sodium hyaluronate lubricant into the metal-on-polymer friction interface. Compared with pure water lubrication, the friction coefficient and wear volume were reduced by up to 62.9%, and 86.9% respectively. Moreover, the proposed lubrication method provided a long-term lubrication on artificial hip joints.

Ceramic Coatings Confer No Survivorship Advantages in Total Knee Arthroplasty-A Single-Center Series of 1641 Knees

Background

Ceramic coatings in total knee arthroplasty have been introduced with the aim of reducing wear and consequently improving implant survivorship. We studied both cobalt-chrome-molybdenum (CoCrMo) and ceramic-coated components of the same implant design from a single center to identify if the ceramic coating conferred any benefit.

Methods

We identified 1641 Columbus total knee arthroplasties (Aesculap AG, Tüttlingen, Germany) from a prospectively collected arthroplasty database. Of the 1641, 983 were traditional CoCrMo, and 659 had the Columbus AS ceramic coating. Patients were followed up until death or revision of any component of the implant.

Results

There was no significant difference in implant survivorship using any component revision as the endpoint between the CoCrMo femur and the ceramic-coated femur at a mean of 9.2 years in follow-up for the CoCrMo group and 5 years for the ceramic-coated group (37 vs 14; P = .76). There was no reduction in the proportion of components revised for aseptic loosening or infection in the ceramic-coated cohort.

Conclusions

At midterm follow-up, there was no benefit in terms of implant survivorship in using a ceramic coating.

Prospective Mid-Term Results of a Completely Metal-Free Ceramic Total Knee Endoprosthesis: A Concise Follow-Up of a Previous Report

BACKGROUND

Hypersensitivity reactions are suspected to cause premature aseptic loosening in susceptible patients after total knee arthroplasty. In response, metal-free implants have been developed. The aim of this prospective, observational midterm study was the assessment of a completely metal-free ceramic knee replacement system as a concise follow-up of a previous report.

METHODS

Thirty-eight patients, with anamnestic suspected or documented allergy to the metal used in prosthetic alloys, participated in this 4-year follow-up of the metal-free BPK-S (Peter Brehm) total knee replacement system with ceramic femoral and tibial components. Clinical assessment included Knee Society Score (KSS), Oxford Knee Score, Euro Quol-5D-Visual Analogue Scale (EQ-5D-VAS), and perioperative or postoperative complications and need for revision. The position of the implant, signs of loosening, and leg alignment were assessed radiographically.

RESULTS

All postoperative clinical scores improved significantly from baseline to 48-month follow-up examination. The Oxford Knee Score improved from 39 to 15 points. The KSS improved from 99 to 195 points (the KSS knee score 42.5 to 96 and the KSS function score 60 to 100). The EQ-5D improved from 12 to 7 points; the EQ-VAS improved from 52.5 to 97 points. No allergic reactions could be detected. Radiologically, a median preoperative varus deformity of 5° improved to 0° at 4-year follow-up. Radiolucent lines appeared around uncemented areas with no clinical symptoms.

CONCLUSION

The fully metal-free BPK-S Integration ceramic knee replacement system exhibits excellent immuno-allergological compatibility, offering a safe option for patients with prior hypersensitivity reactions to metallic materials. Full cementation of all components is recommended to avoid radiolucent lines around the implant.

Cobalt-chromium femoral components developed scratches and released metal debris in simulated wear whereas ceramic femoral components did not

AIMS

The aims of this study were to evaluate wear on the surface of cobalt-chromium (CoCr) femoral components used in total knee arthroplasty (TKA) and compare the wear of these components with that of ceramic femoral components.

METHODS

Optical profilometry was used to evaluate surface roughness and to examine the features created by the wear process in a knee wear simulator. We developed a method of measuring surface changes on five CoCr femoral components and quantifying the loss of material from the articular surface during the wear process. We also examined the articular surface of three ceramic femoral components from a previous test for evidence of surface damage, and compared it with that of CoCr components.

RESULTS

We found that the surface roughness of CoCr components rapidly increased during the first 1,000 wear cycles, then reached a steady state, but material loss from the surface continued at a rate of 1,778,000 μm³ per million cycles as carbides were removed from its matrix. These carbides formed third-body wear particles, leading to the formation of new scratches even as older scratches were worn away. In contrast, no scratching, loss of material, or other surface damage, when evaluated with one nanometer resolution, was found on the surface of the ceramic components after a 15 M wear cycle test.

CONCLUSION

This study showed wear and loss of CoCr material from scratching and microabrasive wear in TKA. The material loss from the surface continued in a linear relationship with increasing cycles. We also found the absence of scratching and roughening of ceramic femoral components in simulated wear, suggesting an advantage in wear rate and avoiding metal sensitivity. This may have implications in the management of persistent pain after TKA. Cite this article: Bone Joint J 2021;103-B(6 Supple A):94-101.

Ultra-high-molecular-weight Polyethylene (UHMWPE) Wing Method for Strong Cranioplasty

We developed a new cranioplasty method that utilizes artificial bone made of ultra-high-molecular-weight polyethylene, with a wedge-shaped edge (UHMWPE Wing). This study shows the methods and data of case series and finite element analyses with the UHMWPE Wing. A circumferential wing was preoperatively designed for a custom-made artificial bone made of UHMWPE to achieve high fixed power and to minimize the usage of cranial implants. Here, we present 4 years of follow-up data and finite element analyses for patients treated with the UHMWPE Wing between February 2015 and February 2019. Eighteen consecutive patients underwent cranioplasty using our UHMWPE Wing design. There were no postoperative adverse events in 17 of the patients for at least 18 months. One case of hydrocephalus experienced screw loosening and graft uplift due to shunt malfunction. Placement of a ventriculo-peritoneal shunt immediately returned the artificial bone to normal position. Finite element analyses revealed that a model using the UHMWPE Wing had the highest withstand load and lowest deformation. This is the first report on the UHMWPE Wing method. This method may enable clinicians to minimize dead space and achieve high strength in cranioplasty.

Similar outcome during short-term follow-up after coated and uncoated total knee arthroplasty: a randomized controlled study

PURPOSE

Patients with known hypersensitivity to metals often require hypoallergenic TKA implants. Coating of a standard implant is a common solution, and although in vitro tests have demonstrated reduction of polyethylene wear for these coatings, it is still unknown whether these implants have any clinical benefit. This study was initiated to investigate metal ion concentrations, knee function and patient-reported outcome (PRO) after coated and uncoated TKA.

METHODS

One hundred and twenty-two (122) patients were randomized to receive a coated or a standard TKA and, after exclusions, 59 patients were included in each group. Knee function and PRO were assessed with validated scores up to 3 years after surgery. Metal ion concentrations in blood samples were determined for chromium, cobalt, molybdenum and nickel, preoperatively and 1 year after surgery.

RESULTS

Chromium concentrations in patient plasma increased from a median of 0.25 to 1.30 µg/l in the standard TKA group, and from 0.25 to 0.75 µg/l in the coated TKA group (p = 0.012). Thirteen patients (3 coated, 10 standard TKA) had chromium concentrations above 2 µg/l. The concentrations of cobalt, molybdenum and nickel did not change. Patient-reported outcome measures (PROM) demonstrated a substantial improvement after TKA, without any differences between the groups.

CONCLUSION

The increase in chromium concentration in the standard group needs further investigation. If surgeons use coated implants, they can be confident that these implants perform as well as standard implants.

LEVEL OF EVIDENCE

I.

What Is the Incidence of Cobalt-Chromium Damage Modes on the Bearing Surface of Contemporary Femoral Component Designs for Total Knee Arthroplasty?

BACKGROUND

The purpose of this study was to determine the incidence of metal release in contemporary total knee arthroplasty and the patient-related factors associated with this release.

METHODS

In total, 256 retrieved cobalt-chromium femoral components were collected through a multi-institutional orthopedic implant retrieval program (implanted: 1-15 years). Implants were mainly revised for loosening (84/256), instability (62/256), and infection (46/256). Third-body damage was assessed using a semiquantitative scoring method. Microscale electro-corrosion damage (MECD) was evaluated using digital optical microscopy. Radii of curvature were measured from representative components to calculate anterior-posterior and medial-lateral ratios. Femoral component surface roughness was measured using a white light interferometer. Using a multivariable linear model, associations between damage score, implant, and patient factors were tested. Spearman's ρ correlation tests were performed to determine the association between roughness measurements and damage score.

RESULTS

Mild to severe damage was observed in 52% (134/256) of the components. In the multivariable linear model, anterior-posterior ratio (β = -8.07; P < .001), loosening (β = -0.52; P = .006), and patient weight (β = 0.01; P = .007) were associated with damage score. Suspected MECD damage was observed in 82% (209/256) of components. The R_a value (ρ = 0.196; P = .002) and R_q value (ρ = 0.157; P = .012) increased as the damage score increased.

CONCLUSION

The findings of this retrieval study support that similar damage mechanisms exist in contemporary and long-term total knee arthroplasty devices. Additionally, we observed associations between loosening, anterior-posterior conformity, and patient weight with increased surface damage.

A novel ceramic tibial component is as safe as its metal counterpart

Failure rates of 2–10% provide evidence for further development in knee arthroplasty. The purpose of our study was to examine the safety of the tibial component of a novel all-ceramic total knee replacement (TKR) (BPK-S Integration ceramic) consisting of BIOLOX®delta ceramic. The standards ISO 14879-1 and ASTM F1800-07 describe the test set-up for the experimental strength verification with a significantly increased maximum load of 5300 N (900 N are required) and post-fatigue burst strength testing. All specimens were able to prove their mechanical strength against fracture in the alternating load test. There was no material fracture in any of the included tibial components. The subsequent post-fatigue burst strength testing revealed the maximum strength against fracture of all specimens. With at least 9.7 kN for size 3 and at least 12.1 kN for size 6, all specimens showed relatively large strength reserves to the stress in the alternating load test. So far we simulated an in vivo lifetime of 10 years for the tibial component. Further studies should be conducted in which longer in vivo lifetimes of the components are simulated to investigate possible fatigue of the used material over a longer period of time.

Ceramic Total Knee Arthroplasty: Ready to Go?

Total knee arthroplasty (TKA) is a well-established surgical procedure in the late stages of knee osteoarthritis. Nevertheless, this procedure is associated with a percentage of unsatisfactory results and biomechanical failures, with aseptic loosening being the most common cause of revision. Beside these problems, cutaneous and systemic hypersensitivity reactions to metals have arisen as an increasing concern after joint arthroplasties, even if allergies against implant materials are still a quite rare and not well-known problem. Ceramic composites have been recently used in prosthetic components, showing minimum wear and excellent long-term results in total hip replacement, due to their high resistance to scratching and their better wettability with respect to cobalt-chromium alloy. Furthermore, the biologic response to debris generated from these bearings is less aggressive. Knee joint simulator tests and clinical results demonstrate promising results of TKAs with ceramic components that should led to benefit for the patients.

Long-Term Durability of Ceramic Tri-Condylar Knee Implants: A Minimum 15-Year Follow-Up

BACKGROUND

Ceramic bearings are not commonly used in total knee arthroplasty (TKA). So far, little information is available about whether long-term survivorship and good clinical outcomes can be ensured with ceramic knee implants. The purposes of the present study were to evaluate the clinical and radiological outcomes, and to assess the long-term durability of a ceramic tri-condylar implant.

METHODS

A total of 507 consecutive TKAs were carried out using a ceramic tri-condylar femoral implant. The posterior cruciate ligament was sacrificed, and all components were fixed with bone cement. Clinical outcomes were assessed retrospectively with the Knee Society scoring system. Kaplan-Meier survivorship was calculated to determine the cumulative survival rate.

RESULTS

One hundred sixty-seven knees (114 patients) were available for clinical outcomes. The average range of flexion improved from 118.1° preoperatively to 123.7° at a minimum 15-year follow-up (P < .001). The average Knee Society knee score improved from 39.1 to 92.8 (P < .001). The functional score also improved from 36.0 to 47.0 (P < .001). With revision for any surgery or radiographic failure as the end point, Kaplan-Meier survivorship at 15 years was 94.0%. With revision of any component as the end point, the corresponding survivorship was 96.2%.

CONCLUSION

Clinically, the postoperative knee flexion range and Knee Society scores were good after long-term follow-up. The survivorship of the ceramic knee implant was excellent over the 15-year follow-up, and long-term durability was achieved, making ceramic a promising alternative material for the femoral component in TKA.

Prospective comparative clinical study of ceramic and metallic femoral components for total knee arthroplasty over a five-year follow-up period

BACKGROUND

The aim of this prospective comparative study was to evaluate the clinical and radiological outcomes of a TKA system, comparing a ceramic (BIOLOX® delta) and metallic (Co28Cr6Mo) femoral component over a five-year follow-up period.

METHODS

Forty-three TKA patients (17 metallic and 26 ceramic femoral components) were enrolled in the study. Clinical and radiological evaluations were performed preoperatively and at three, 12, 24 and 60months postoperatively, using the HSS-, WOMAC- and SF36-Scores, in addition to standardized X-rays.

RESULTS

The HSS-Score improved significantly from 58.7±12.7 points preoperatively to 88.5±12.3 points at five-years postoperative in the ceramic group, and 60.8±7.7 to 86.2±9.4 points in the metallic group. WOMAC- and SF-36-Scores showed significant improvement over time in both groups. There were no significant differences between groups for HSS-, WOMAC- and SF-36-Scores, nor for range of motion (p≤0.897) at any follow-up evaluation. Furthermore, radiological evaluation showed no implant loosening or migration in either group.

CONCLUSIONS

Mid-term outcomes for the ceramic femoral components demonstrated good clinical and radiological results, as well as comparable survivorship to the metallic femoral component of the same total knee system, and to other commonly used metallic total knee systems. Therefore, ceramic knee implants may be a promising solution for the population of patients with osteoarthritis and metal sensitivity. Long-term studies are required in order to confirm the positive mid-term clinical results, and to follow the implant survival rate in regard to the enhanced wear resistance of ceramic implants.

Midterm Results After Coated and Uncoated TKA: A Randomized Controlled Study

Patients undergoing total knee arthroplasty (TKA) who have hypersensitivity to metals usually receive hypoallergenic TKA implants. Coating of a standard implant is a common solution. Although in vitro tests have demonstrated reduction in polyethylene wear for these coatings, it is unknown whether these costly implants have a clinical benefit for patients. One hundred twenty patients undergoing TKA were randomly assigned to receive a novel 7-layer-coating implant or a standard TKA implant. One revision occurred in the standard group, resulting in a calculated 5-year survival of 100% in the coated group and 98.1% in the standard group. The Oxford Knee Score improved substantially in both groups from a mean of 21.6 points preoperatively in the coated group and 21.9 points in the standard group to 39.2 points and 39.2 points, respectively. The current authors observed no adverse effects with the new coating during midterm follow-up. However, longer follow-up time is needed to evaluate possible advantages of this coating. [Orthopedics. 2016; 39(3):S13-S17.].

In-vivo kinematics of high-flex posterior-stabilized total knee prosthesis designed for Asian populations

PURPOSE

The purpose of this study was to determine in-vivo kinematics of our developed posterior-stabilized (PS) total knee prosthesis for Asian populations in comparison with a popular high-flexion PS prosthesis.

METHODS

We analyzed 62 osteoarthritic knees: 31 knees with the new PS prosthesis (group A) and 31 knees with a popular high-flexion PS prosthesis (group B). Radiographic knee images were taken during standing, lunge, and kneeling activities. The three-dimensional position and orientation of the implant components were determined using model-based shape matching techniques.

RESULTS

Group A showed slightly greater implant flexion angles compared with knees with conventional prosthesis at maximum lunge (average: 119 vs. 110°, p = 0.001), and at maximum kneeling (121 vs. 114°, p = 0.004), although the range of motion was not significantly different. The femoral centre positions were more posterior in group A at standing, at 90° lunge, at maximum lunge (-9 and -7 mm, p = 0.004), at 90° kneeling, and at maximum kneeling (-9 vs. -7 mm, p = 0.016), and posterior translations of the femoral center were greater at 90° knee flexion postures. The femoral centre positions had a strong negative correlation with implant flexion angles at maximum lunge in group B (r = -0.893, p < 0.001), but not in group A (p = 0.242).

CONCLUSIONS

The new PS prosthesis designed for Asian knee morphology achieved flexion angles and range of motion at least comparable to that of conventional high-flexion PS prosthesis. The femoral roll-back pattern, however, is different from a conventional knee, reflecting the post/cam design.

First clinical study of a novel complete metal-free ceramic total knee replacement system

Background

The aim of the study was to evaluate the safety and efficacy of a novel metal-free ceramic total knee replacement system.

Methods

Thirty-eight primary total knee arthroplasties (TKAs) were performed on 34 patients using the metal-free BPK-S ceramic total knee replacement system with both the femoral and tibial components of an alumina/zirconia ceramic composite. The clinical outcome was evaluated pre- and postoperatively at 3 (n = 32 TKA) and 12 months (n = 32 TKA) using the Knee Society Score (KSS), the Oxford Knee Score and the EQ-5D. Safety analysis was performed by radiological examination and assessment of adverse events.

Results

Postoperatively, the KSS, Oxford Knee Score and EQ-5D improved significantly at 3 and 12 months (p < 0.001). Non-progressive partial radiolucent lines were observed in six cases, but there was no osteolysis and no implant loosening. Induction or exacerbation of allergies did not occur during the follow-up.

Conclusions

The metal-free BPK-S ceramic total knee replacement system proved to be a safe and clinically efficient alternative to metal implants in this short-term follow-up study.

Elucidating trends in revision reverse total shoulder arthroplasty procedures: a retrieval study evaluating clinical, radiographic, and functional outcomes data

BACKGROUND

The purpose of this study was to explore relationships between damage modes in explanted reverse total shoulder arthroplasty (RTSA) components, patient and radiographic risk factors, and functional data to elucidate trends in RTSA failure.

METHODS

Fifty RTSA systems, retrieved from 44 patients, with 50 polyethylene (PE) liners, 30 glenospheres, 21 glenoid baseplates, 13 modular humeral metaphases, and 17 humeral stems, were examined for damage modes, including abrasion, burnishing, dishing, embedding, scratching, and pitting. PE liners were also analyzed for delamination and edge deformation. Charts were reviewed for patient, surgical, and functional data. Pre-revision radiographs were analyzed for scapular notching and loosening.

RESULTS

Average term of implantation was 20 months (range, 0-81 months). Metallic components exhibited abrasion, burnishing, dishing, pitting, and scratching. PE liners displayed all damage modes. Damage was exhibited on 93% of glenospheres and 100% of PE liners. Of 29 aseptic shoulders, 13 showed evidence of scapular notching and 5 of humeral loosening. There was a moderate correlation between radiographically observed implant failure or dissociation and PE embedding (r = 0.496; P < .001). There were weak and moderate correlations between scapular notching severity and PE dishing (r = 0.496; P = .006), embedding (r = 0.468; P = .010), and delamination (r = 0.384; P = .040).

CONCLUSIONS

To date, this is the largest series of retrieved RTSA components and the first to relate damage modes to radiographic and clinical data. Most damage was observed on the PE liners, on both the articular surface and rim, and glenosphere components. Correlation of retrieval findings with radiographic and clinical data may help establish predictors of prostheses at risk for failure.

Prospective multi-centre study on a composite ceramic femoral component in total knee arthroplasty: Five-year clinical and radiological outcomes

BACKGROUND

Enhanced wear resistance of ceramics in general and improved mechanical characteristics of composite ceramics in terms of strength and resistance meet the demands for application in TKA. The aim of this prospective international multi-centre study was to evaluate the 5-year clinical and radiological outcomes of an unconstrained TKA with a composite ceramic femoral component.

METHODS

A total of 107 patients (109 knees) underwent TKA with the MULTIGEN-PLUS Ceramic Knee at seven centres in three European countries. Clinical and radiological assessments were performed preoperatively and postoperatively at 3, 12, 24 and 60 months, using HSS, WOMAC, SF-36 and standardised radiographs.

RESULTS

Mean HSS and WOMAC increased significantly from 55.1±11.5 (21-83) and 48.1±16.6 (3-90) preoperatively to 85.6±9.6 (49-98) and 73.3±20.4 (17-100) at 60 months. Mean SF-36 showed significant improvements in patients' quality of life (49.1±17.6 (12-96) preoperatively versus 67.7±23.1 (12-100) at 60 months). Non-progressive radiolucent lines (<1 mm) were observed around the femoral component in four cases. Neither implant migration nor loosening were registered. Kaplan-Meier survivorship was 96.0% at 60 months (92.1-100%, CI 95%).

CONCLUSIONS

Five-year implant survival rate of the ceramic knee is comparable to other metallic and ceramic unconstrained TKA systems. Although the assessment of long-term implant survivorship is still pending, the ceramic implants represent a promising solution for patients with allergies against metallic components and furthermore for the general osteoarthritis population due to enhanced wear resistance.

Reduced UHMWPE wear using magnesia-stabilized zirconia instead of CoCr femoral components in a knee simulator

Magnesia-stabilized zirconia (Mg-PSZ) is stable and maintains a scratch-resistant surface in hip replacement, but is untested in knees. We assessed whether using Mg-PSZ instead of cobalt-chromium (CoCr) femoral components resulted in less tibial insert wear, and evaluated changes in topography and roughness of the femoral components. Inserts bearing against CoCr or Mg-PSZ were tested using standard (9 Mc) and aggressive (6 Mc) waveforms. Femoral component surface topography and roughness were evaluated before and after testing by optical profilometry. When bearing against Mg-PSZ, UHMWPE wear rate decreased by 73% (standard) and by 59% (aggressive conditions). After 15 Mc, CoCr components featured deep scratches, and roughness increased five-fold, while Mg-PSZ components were unchanged. Mg-PSZ femoral components may be indicated for high-demand patients and those with metal sensitivity.

Experimental testing of total knee replacements with UHMW-PE inserts: impact of severe wear test conditions

Aseptic implant loosening due to inflammatory reactions to wear debris is the main reason for the revision of total knee replacements (TKR). Hence, the decrease in polyethylene wear particle generation from the articulating surfaces is aimed at improving implant design and material. For preclinical testing of new TKR systems standardized wear tests are required. However, these wear tests do not reproduce the entire in vivo situation, since the pattern and amount of wear and subsequent implant failure are underestimated. Therefore, daily activity, kinematics, implant aging and position, third-body-wear and surface properties have to be considered to estimate the wear of implant components in vivo. Hence, severe test conditions are in demand for a better reproduction of the in vivo situation of TKR. In the present article an overview of different experimental wear test scenarios considering clinically relevant polyethylene wear situations using severe test conditions is presented.

Scanning electron microscopical observation of an osteoblast/osteoclast co-culture on micropatterned orthopaedic ceramics

In biomaterial engineering, the surface of an implant can influence cell differentiation, adhesion and affinity towards the implant. On contact with an implant, bone marrow-derived mesenchymal stromal cells demonstrate differentiation towards bone forming osteoblasts, which can improve osteointegration. The process of micropatterning has been shown to improve osteointegration in polymers, but there are few reports surrounding ceramics. The purpose of this study was to establish a co-culture of bone marrow-derived mesenchymal stromal cells with osteoclast progenitor cells and to observe the response to micropatterned zirconia toughened alumina ceramics with 30 µm diameter pits. The aim was to establish whether the pits were specifically bioactive towards osteogenesis or were generally bioactive and would also stimulate osteoclastogenesis that could potentially lead to osteolysis. We demonstrate specific bioactivity of micropatterns towards osteogenesis, with more nodule formation and less osteoclastogenesis compared to planar controls. In addition, we found that that macrophage and osteoclast-like cells did not interact with the pits and formed fewer full-size osteoclast-like cells on the pitted surfaces. This may have a role when designing ceramic orthopaedic implants.

Designing prosthetic knee joints with bio-inspired bearing surfaces

It has long been known that articular cartilage exhibits a surface microtexture with shallow indentations. By contrast, prosthetic joints consist of ultra-smooth bearing surfaces, the longevity of which does not reach that of natural cartilage. We show that adding a microtexture to the smooth femoral component of a prosthetic knee joint reduces friction by increasing the lubricant film thickness between the bearing surfaces of the knee. We have implemented an elastohydrodynamic lubrication model to optimize the geometry of the microtexture, while taking into account the deformation of the polyethylene tibial insert. We have manufactured several microtexture designs on a surrogate femoral component, and experimentally demonstrate that the microtexture reduces friction between the surrogate femoral component and tibial insert.

Total knee replacement system with a ceramic femoral component versus two traditional metallic designs: a prospective short-term study

PURPOSE

To compare the short-term outcome of the Multigen Plus system using a symmetric ceramic femoral component with that of 2 metallic total knee replacement (TKR) systems.

METHODS

60 patients (62 knees) with osteoarthritis or rheumatoid arthritis underwent primary TKR using the Genia system (n=20), the Multigen Plus system (n=17), and the Multigen Plus system with a ceramic femoral component (n=25). Outcome was evaluated pre- and post-operatively (at 3, 12, and 24 months) using the Hospital for Special Surgery (HSS) score, the Western Ontario and McMaster Universities (WOMAC) score, and the Short-Form 36 (SF-36) score.

RESULTS

The 3 groups did not differ significantly at all 4 time points in terms of the HSS score, WOMAC score, and SF-36 score. The range of motion was significantly less in patients treated with the Genia system. Postoperatively, the HSS and WOMAC scores improved significantly in all 3 groups, whereas the SF-36 score improved significantly (at 12 and 24 months) only in patients treated with the Multigen Plus system with a ceramic femoral component. The implant position in most patients was optimal. All radiolucent lines were within 1 mm and did not progress.

CONCLUSION

The short-term outcome of the 3 TKR systems was comparable. Ceramic femoral components performed comparably to traditional metallic designs.

Are the long term results of a high-flex total knee replacement affected by the range of flexion?

PURPOSE

The purpose of this study was to examine the effect of deep flexion on the long-term durability of a high-flex ceramic implant in total knee arthroplasty.

METHODS

Five hundred and five consecutive knees replaced with a Bi-Surface knee system (Kyocera Medical, Osaka, Japan) were divided into two groups according to the range of flexion by 135° postoperatively. Comparison of implant durability was made between the high- and low-flexion groups after a minimum ten year follow-up.

RESULTS

With revision for any surgery as the end point, the survival rates at ten years were 95.5% and 96.2% in the high- and low-flexion group, respectively (p = 0.63). With revision for mechanical failure as the end point, survival rates were 98.7% and 98.5%, respectively (p = 0.94).

CONCLUSION

Implant survival rate was similar for both groups. Deep flexion seemed not to affect long-term durability.

Total knee prosthesis polyethylene wear reduction by a new metal part finishing method

PURPOSE

The purpose of this study was to assess a new metal component finishing designed to improve total knee prosthesis durability. Wear of ultrahigh molecular-weight polyethylene (UHMWPE), with generation of submicrometer- and micrometer-sized particles, has been associated with osteolysis and artificial joint failure. Wear extent is influenced by several factors, some of which are related to manufacturing.

METHODS

UHMWPE wear was assessed in metal prosthesis components finished with the Microloy® technology and in traditionally finished components by wear simulation experiments (pin on disk and knee simulator tests) and analysis of wear debris.

RESULTS

Microloy®-finished prosthesis showed a 48.5% reduction in UHMWPE total weight loss compared with traditional components (P=0.002). A statistically significant (P<0.05) reduction of UHMWPE debris were detected from the Microloy®-finished compared with the traditionally finished components.

CONCLUSIONS

These findings suggest the Microloy® metal finishing may enhance the long-term performance of knee prostheses.

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.

Radiographic and retrieval wear analyses of the first generation highly cross-linked polyethylene cup against a ceramic femoral head

In this study, the in vivo wear of highly cross-linked polyethylene (CLPE) cups against alumina ceramic femoral heads was evaluated by radiographic and retrieval analysis. The radiographic wear of six ethylene oxide gas-sterilized (i.e., non-cross-linked) conventional polyethylene (PE) cups with the mean follow-up of 20.9 years and 60 CLPE cups with the mean follow-up of 7.4 years was measured. The retrieved 16 PE cups with clinical use for mean 21.5 years and 10 CLPE cups with clinical use for mean 2.9 years was evaluated as a retrieval analysis. In the radiographic analysis, the linear wear of CLPE cups was significantly lower (99% reduction) compared to conventional polyethylene cups. The results of retrieval analyses for both cups were similar to those of radiographic analyses. Even when third-body wear occurred during clinical use, no surface damage was observed on the surface of ceramic femoral heads. The surface is not sensitive to third-body wear, and hence, the ceramic femoral head has a great advantage in terms of the wear of CLPE under third-body wear conditions. In conclusion, CLPE cups used with alumina ceramic femoral heads in total hip arthroplasty should have favorable wear resistance in several in vivo situations.

Embossing of micropatterned ceramics and their cellular response

The aim of this work is to investigate the use of microtopographies in providing physical cues to modulate the cellular response of human mesenchymal stem cells on ceramics. Two microgrooved patterns (100 μm/50 μm, 10 μm/10 μm groove/pitch) were transcribed reversely onto alumina green ceramic tapes via an embossing technique followed by sintering. Characterization of the micropatterned alumina surfaces and their cellular response was carried out. Spread and polygonal cell morphologies were observed on the wider groove (50 μm/100 μm) surface. Cells seeded onto the narrow groove (10 μm/10 μm) surface aligned themselves alongside the grooves, resulting in more elongated cell morphology. More osteoid matrix nodules shown by osteopontin and osteocalcin biomarkers were detected on the larger grooved surfaces after cell culture of 21 days, indicating a greater level of osteogenicity. This study has shown that micropatterned wider groove (50 μm) topographies are more suitable surfaces for improving osseointegration of ceramic implants.

Alternative bearings in total knee arthroplasty: risk of early revision compared to traditional bearings: an analysis of 62,177 primary cases

BACKGROUND AND PURPOSE

There is no substantial clinical evidence for the superiority of alternative bearings in total knee arthroplasty (TKA). We compared the short-term revision risk in alternative surface bearing knees (oxidized zirconium (OZ) femoral implants or highly crosslinked polyethylene (HXLPE) inserts) with that for traditional bearings (cobalt-chromium (CoCR) on conventional polyethelene (CPE)). The risk of revision with commercially available HXLPE inserts was also evaluated.

METHODS

All 62,177 primary TKA cases registered in a Total Joint Replacement Registry between April 2001 and December 2010 were retrospectively analyzed. The endpoints for the analysis were all-cause revisions, septic revisions, or aseptic revisions. Bearing surfaces were categorized as OZ-CPE, CoCr-HXLPE, or CoCr-CPE. HXLPE inserts were stratified according to brand name. Confounding was addressed using propensity score weights. Marginal Cox-regression models adjusting for surgeon clustering were used.

RESULTS

The proportion of females was 62%. Average age was 68 (SD 9.3) years, and median follow-up time was 2.8 (IQR 1.2-4.9) years. After adjustments, the risks of all-cause, aseptic, and septic revision with CoCr-HXLPE and OZ-CPE bearings were not statistically significantly higher than with traditional CoCr-CPE bearings. No specific brand of HXLPE insert was associated with a higher risk of all-cause, aseptic, or septic revision compared to CoCr-CPE.

INTERPRETATION

At least in the short term, none of the alternative knee bearings evaluated (CoCr-HXLPE or OZ-CPE) had a greater risk of all-cause, aseptic, and septic revision than traditional CoCr-CPE bearings.

Mid-term clinical results of alumina medial pivot total knee arthroplasty

PURPOSE

The medial pivot total knee prosthesis has been designed to reproduce physiological knee kinematics. It has been reported that alumina ceramic femoral components reduce polyethylene wear. Thus, medial pivot total knee prostheses with alumina ceramic femoral components were introduced. The purpose of this study was to evaluate the clinical results of patients who underwent newly introduced alumina medial pivot total knee arthroplasties (TKA).

METHODS

We evaluated the clinical results of 107 alumina medial pivot TKAs in 80 consecutive patients with a mean follow-up period of 5 years.

RESULTS

Alumina medial pivot TKAs provided significant improvements in the patients' Knee Society knee scores, function scores and post-operative ranges of motion compared with their pre-operative statuses (each, P < 0.05). There was no statistical correlation between the change in maximum knee flexion and the increase in posterior condylar offset. Revision surgery was required in one knee due to a post-operative fracture of the tibial plateau after a fall that occurred 2 years postoperatively. No knees had aseptic loosening, osteolysis, or ceramic fractures. The survival rate was 98.6% at 5 years.

CONCLUSIONS

This study demonstrates satisfactory mid-term clinical results for patients receiving the alumina medial pivot prosthesis.

LEVEL OF EVIDENCE

Therapeutic study, Level IV.

The influence of sterilization method on articular surface damage of retrieved cruciate-retaining tibial inserts

This observational study was designed to determine the importance of sterilization method and insert thickness as predictors of articular damage of cruciate-retaining polyethylene components used in total knee arthroplasty. Ninety-nine explanted tibial inserts were evaluated for surface damage. Severe damage modes were observed in 36 of 52 of γ-irradiated inserts but none of those sterilized by ethylene oxide. Articular damage significantly correlated to time in vivo but not to insert thickness. Inserts sterilized by ethylene oxide gas in gas-permeable packaging exhibited a significantly lower damage accumulation rate compared with inserts sterilized by γ radiation and stored in air or an inert environment. γ irradiation and storage in argon instead of air reduced the frequency of severe damage such as delamination but not the overall damage rate.

Intraoperative impaction of total knee replacements: an explicit finite-element-analysis of principal stresses in ceramic vs. cobalt-chromium femoral components

BACKGROUND

In connection with technological advances in the manufacturing of medical ceramics, a newly developed ceramic femoral component was introduced in total knee arthroplasty. We generated an explicit finite-element-model to calculate the stresses developed under the highly dynamic intraoperative impaction with regard to cobalt-chromium and ceramic implant material as well as application of a silicone cover in order to reduce stress.

METHODS

The impaction was calculated with the hammer hitting the backside of the impactor at previously measured initial velocities. Subsequently the impactor, consisting of a steel handhold and a polyoxymethylene head, hit the femoral component. Instead of modelling femoral bone, the implant was mounted on four spring elements with spring constants previously determined in an experimental impaction model. The maximum principal stresses in the implants were evaluated at 8000 increments during the first 4 ms of impact.

FINDINGS

The ceramic implant showed principal stresses 10% to 48% higher than the cobalt chromium femoral component. The simulation of a 5mm thick silicone layer between the impactor and the femoral component showed a strong decrease of vibration resulting in a reduction of 54% to 68% of the maximum stress amounts. The calculated amounts of principal stress were beneath the ultimate bending strengths of each material.

INTERPRETATION

Based on the results, intraoperative fracture of femoral components in total knee replacement may not be caused solely by impaction, but also by contributing geometrical factors such as inadequate preparation of the distal femur. In order to minimize the influence of impaction related stress peaks we recommend limiting the velocity as well as the weight of the impaction hammer when inserting femoral components. The silicone cover seems to deliver a strong decrease of implant stress and should be considered in surgery technique in the future.

The Bi-Surface total knee arthroplasty: minimum 10-year follow-up study

The Bi-Surface Knee System (Japan Medical Material, Kyoto, Japan), which has a unique ball-and-socket joint and whose femoral component is made from alumina ceramic, was designed to improve deep knee flexion and long-term durability after total knee arthroplasty. The purpose of this study was to review the clinical results of a minimum 10-year follow-up. Between 1989 and 1997, 507 total knee arthroplasties were carried out in 371 patients. Forty three patients (56 knees) were lost to follow-up. The mean age of the patients at operation was 68.5 years, and the patients were followed up for a mean of 11.7 years. The knees were evaluated on the basis of Knee Society knee score and functional score, radiographs, and Kaplan-Meier survivorship analysis. The knee score was improved from 38.9+/-17.4 points preoperatively to 93.3+/-7.8 points at the latest follow-up (p<0.001). The functional score was improved from 34.9+/-19.3 points to 52.7+/-24.1 points (p<0.001). The mean range of flexion was improved from 118.7+/-21.7 degrees to 124.2+/-20.8 degrees (p<0.001). The critical angle, which means the border to gain more range of flexion postoperatively, was 130.1 degrees. Kaplan-Meier survivorship at 10-year was 95.9% with any operation or radiographic failure as the end point. The corresponding rate was 97.4% with revision of any component as the end point. No ceramic component fracture occurred. The present study demonstrates that good range of flexion was maintained for a long time after total knee arthroplasty with excellent durability. The Bi-Surface Knee System appears to have achieved its design objectives.