Wear-induced Osteolysis Research Articles

Midterm osteolysis-induced aseptic failure of the M6-C™ cervical total disc replacement secondary to polyethylene wear debris

BackgroundAccording to published meta-analyses, cervical total disc replacement (CTDR) seems to be superior to anterior cervical decompression and fusion (ACDF) in most clinical parameters. Despite short-term clinical success of CTDR, there are concerns regarding long-term durability of these prostheses.MethodsThis prospective study involved 382 patients who received standalone CTDR or a hybrid procedure (ACDF/CTDR). A retrospective comparison between different CTDR devices was conducted regarding patient-reported outcome measures (PROMs), failure scenarios, and revision surgeries. The M6-C™ Artificial Cervical Disc (Orthofix, Lewisville, Texas) cohort was compared to the other CTDR devices clinically. Etiological reasons for revision, and the surgical technique of the revision was investigated.ResultsFifty-three patients received M6-C CTDR. Eighteen patients (34%) were revised at an average of 67 months postoperatively for wear-induced osteolysis. There were three additional cases of pending revision. The PROMs of the two groups were similar, indicating that the failure mode (wear-induced osteolysis) is often asymptomatic. The demographics of the two groups were also similar, with more women undergoing revision surgery than men. There were three one-level CTDR, four two-level hybrids, seven three-level hybrids, and three four-level hybrids revised anteriorly. Sixteen patients underwent removal of the prosthesis and were treated according to the extent of osteolysis. There were four vertebrectomies, six revisions to ACDF, and six revisions to another CTDR. One patient underwent supplemental fixation using a posterior approach. The other CTDR cohort had an incidence of 3.3% at the equivalent time, and none of these were due to osteolysis or wear-related events.ConclusionsThere is a concerning midterm failure rate related to ultra-high-molecular-weight-polyethylene wear-induced osteolysis in the M6-C. Patients implanted with the M6-C prosthesis should be contacted, informed, and clinically and radiologically assessed.

A Systematic Review of Compliant Mechanisms as Orthopedic Implants

Abstract Currently available motion-preserving orthopedic implants offer many advantages but have several limitations to their use, including short device lifetime, high part count, loss of natural kinematics, and wear-induced osteolysis and implant loosening. Compliant mechanisms have been used to address some of these problems as they offer several potential advantages - namely, wear reduction, reduced part count, and the ability to achieve complex, patient-specific motion profiles. This article provides a systematic review of compliant mechanisms as orthopedic implants. Based on the PRISMA guidelines for an efficient review, this work identified fourteen implantable orthopedic devices that seek to restore anatomical motion by utilizing mechanical compliance. From reviewing these implants and their results, advantages and consequences for each are summarized. Trends were also identified in how these devices are capable of mitigating common challenges found in orthopedic design. Design considerations for the development of future compliant orthopedic implants are proposed and discussed.

Surface Modification and Biological Approaches for Tackling Titanium Wear-Induced Aseptic Loosening

Aseptic loosening induced by wear-induced osteolysis is considered to be one of the primary factors leading to the revision surgeries which represent a major hurdle for successful total joint arthroplasty. Even though Ti and its alloys possess high specific strength, reduced modulus, and excellent corrosion resistance beneficial for orthopedic implant applications, its success rates are impeded by inadequate wear resistance. Ti wear debris particles are capable of eliciting undesirable osteolytic events by activating pro-inflammatory cytokines such as (TNF)-α, IL1β, and IL6. An effective strategy to circumvent this limitation would require a synergistic (a) improvement of the wear resistance of Ti implant materials via surface modification and (b) inhibition of specific pathways leading to Ti particle-induced aseptic loosening. These two aspects are reviewed in the present article which covers pertinent surface modification strategies (shot peening, laser peening, burnishing, ion implantation and oxygen diffusion hardening) and biological approaches (protein-based biologics and polyphenolic flavanoids) to prevent osteolysis. Combining the respective beneficial aspects from the existing individual surface modification techniques, development of novel biocompatible material coating technologies with high wear resistance and a basic understanding of the biological approaches to prevent the unavoidable inflammatory reactions represent the need of the hour. The ideas outlined in the present review will assist in reducing the research gap between material science as well as biological approaches to reduce the complications associated with Ti wear-induced aseptic loosening leading to revision surgeries.

Ceramic-on-ceramic vs ceramic-on-polyethylene, a comparative study with 10-year follow-up.

BACKGROUNDIn press-fit total hip arthroplasty (THA) ceramic-on-ceramic (CoC) bearings are a potential for overcoming the wear that is seen in ceramic-on-polyethylene (CoPE) bearings, and can lead to wear-induced osteolysis, resulting in loosening of the implant. However, CoC bearings show disadvantages as well, such as squeaking sounds and being more fragile, which can cause ceramic head or liner fracture. Because comparative long-term studies are limited, the objective of this study was to determine the long-term difference in wear, identify potential predictive factors for wear, investigate radiological findings such as osteolysis, and evaluate clinical functioning and complications between these bearings.AIMTo determine 10-year differences in wear, predictive factors for wear, and investigate radiological findings and clinical functioning between CoC and CoPE.METHODSThis observational prospective single-center cohort study with a 10-year follow-up includes a documented series of elective THAs. Primary outcome was wear measured by anteroposterior (AP) radiographs. Secondary outcomes were potential predictive factors for wear, complications during follow-up, Harris hip score (HHS), and radiological findings such as presence of radiolucency, osteolysis, atrophy, and hypertrophy around the cup. Due to the absence of wear in the CoC group, stratified analysis to identify risk factors for wear was only performed in the CoPE group by use of univariate linear regression analysis. HHS was expressed as a change from baseline and the association with bearing type was assessed by use of multivariate linear regression analysis, adjusted for potential confounders.RESULTSA total of 17 CoPE (63.0%) and 25 CoC (73.5%) cases were available for follow-up and showed a linear wear of respectively 0.130 mm/year (range 0.010; 0.350) and 0.000 mm/year (range 0.000; 0.005), which was significant (P < 0.001) between both groups. Wear always occurred in the cranial direction. Cup inclination was the only predictive factor for polyethylene (PE) wear. No dislocations, ceramic head, or liner fractures were seen. The HHS showed a mean change from baseline of 37.1 points (SD 18.5) in the CoPE group and 43.9 (SD 17.0) in the CoC group. This crude difference of 6.8 (range -5.2; 18.7) in favor of the CoC group was not significant (P = 0.26) and was not significant when adjusted for age, gender, and diagnosis either (P = 0.99). No significant differences in complications and radiological findings were seen between groups. CONCLUSIONCoC bearing shows lower wear rates compared to CoPE at 10-year follow-up with cup inclination as a predictive factor for wear and no differences in complications, HHS, and radiological findings.

The use of bisphosphonates to meet orthopaedic challenges.

The anti-resorptive properties of bisphosphonates have been explored to manage several conditions that traditionally have required a surgical solution. In osteonecrosis, their use is predicated on the principle that bone collapse occurs during the revascularisation phase of the disease. If the associated resorptive activity were modulated, the resultant preserved joint architecture may improve clinical outcome and reduce the need for joint replacement. Pre-clinical and small-scale clinical studies have given non-conclusive support for this principle. Adequately powered clinical trials with relevant long-term endpoints are still required to firmly clarify the clinical efficacy of this treatment. Several clinical studies have shown that bisphosphonates can reduce periprosthetic bone loss and, in some situations, enhance implant fixation in the early period after joint replacement. This may be advantageous in settings where osseointegration is problematic. However, the ultimate goals of their use in joint replacement has been to reduce the incidence of late periprosthetic inflammatory osteolysis, the main cause of prosthesis failure. Population-based observational studies have associated bisphosphonate use with a lower incidence of revision surgery, supported by pre-clinical data. However, clinical trials have, to date, failed to demonstrate any efficacy for the human disease. The timing of bisphosphonate administration for secondary prevention after acute osteoporotic fracture has been subject to extensive investigation, with pre-clinical studies showing increased callus formation but decreased remodelling and no effect on the restoration of mechanical integrity of bone. Meta-analysis of clinical trial data indicates that early administration of bisphosphonate after acute fracture does not adversely affect fracture union, pain or functional outcomes. Finally, bisphosphonates have also been explored as a treatment for complex regional pain syndrome type-I. A recent meta-analysis has shown a beneficial effect on visual analogue scale pain scores, but an increase in mild adverse events.

Couple métal-métal ultamet versus céramique-céramique dans l’arthroplastie totale de hanche. Une même survie, mais un taux d’ostéolyse supérieur. Étude à 8 ans de recul

BackgroundTo avoid wear-induced osteolysis, ceramic-on-ceramic (CoC) and metal-on-metal (MoM) bearings have been developed. At present, there are no direct material related clinical comparisons between cementless total hip arthroplasty with CoC and MoM at more than 5-year follow-up. The bearing that is more likely to prevent osteolysis is still controversial. Therefore, we performed a retrospective case control study evaluating CoC and MoM cementless THAs in order to: compare the longevity and complications for CoC and MoM THAs at 5–10 years postoperatively; compare the incidence of osteolysis between both type THAs, and; evaluate pseudotumors in MoM THAs. HypothesisCoC THAs will have a lower rate of osteolysis, better longevity, and better clinical outcomes than MoM THAs. Patients and methodsNinety-six hips underwent CoC THAs, and 56 hips underwent MoM THA (Ultamet, Pinnacle, Depuy). Average patient age at the time of surgery was 57.1 years (range, 28 to 77 years). ResultsThere were no differences with regard to the Harris hip score (89.5 and 90.3 for the CoC and MoM groups, respectively). Osteolysis (9 hips, 14.3%) among MoM THAs were significantly more frequently observed compared to CoC THAs (2 hips, 2.1%). Kaplan-Meier survival at 8 years with implant loosening or revision THA as the endpoint was 98.2% (95% CI: 87.8–99.8) for CoC, and 98.6% (95% CI: 90.2–99.8) for MoM (p=0.684). There was one audible squeaking (1.0%) and no ceramic fracture among CoC THAs. Five (8.9%) hips showed pseudotumors among MoM THAs. DiscussionCoC THAs had a low incidence of osteolysis. No significant difference was seen in the 8 year survival rate between implants, when using implant loosening and revision THA as endpoints. These data indicate that CoC THAs have excellent clinical and radiological outcomes, compared with MoM THAs. Ultamet MoM had a higher rate of osteolysis compared to other MoM bearings; the cup modularity (without polyethylene) and the use of 36mm heads as well as the process of production (after 2006) may play a significant role in the higher rate of osteolysis. Level of evidenceIII, case control study, case control retrospective design.

Same survival but higher rate of osteolysis for metal-on-metal Ultamet versus ceramic-on-ceramic in patients undergoing primary total hip arthroplasty after 8 years of follow-up

BackgroundTo avoid wear-induced osteolysis, ceramic-on-ceramic (CoC) and metal-on-metal (MoM) bearings have been developed. At present, there are no direct material related clinical comparisons between cementless total hip arthroplasty with CoC and MoM at more than 5-year follow-up. The bearing that is more likely to prevent osteolysis is still controversial. Therefore, we performed a retrospective case control study evaluating CoC and MoM cementless THAs in order to:– compare the longevity and complications for CoC and MoM THAs at 5–10 years postoperatively;– compare the incidence of osteolysis between both type THAs;– evaluate pseudotumors in MoM THAs. HypothesisCoC THAs will have a lower rate of osteolysis, better longevity, and better clinical outcomes than MoM THAs. Patients and methodsNinety-six hips underwent CoC THAs, and 56 hips underwent MoM THA (Ultamet, Pinnacle, Depuy). Average patient age at the time of surgery was 57.1 years (range, 28 to 77 years). ResultsThere were no differences with regard to the Harris hip score (89.5 and 90.3 for the CoC and MoM groups, respectively). Osteolysis (9 hips, 14.3%) among MoM THAs were significantly more frequently observed compared to CoC THAs (2 hips, 2.1%). Kaplan-Meier survival at 8 years with implant loosening or revision THA as the endpoint was 98.2% (95% CI: 87.8–99.8) for CoC, and 98.6% (95% CI: 90.2–99.8) for MoM (p=0.684). There was one audible squeaking (1.0%) and no ceramic fracture among CoC THAs. Five (8.9%) hips showed pseudotumors among MoM THAs. DiscussionCoC THAs had a low incidence of osteolysis. No significant difference was seen in the 8-year survival rate between implants, when using implant loosening and revision THA as endpoints. These data indicate that CoC THAs have excellent clinical and radiological outcomes, compared with MoM THAs. Ultamet MoM had a higher rate of osteolysis compared to other MoM bearings; the cup modularity (without polyethylene) and the use of 36mm heads as well as the process of production (after 2006) may play a significant role in the higher rate of osteolysis. Level of evidenceIII, Case control study, case control retrospective design.

In vitro Growth Pattern of Primary Human Osteoblasts on Calcium Phosphate- and Polymethylmethacrylate-Based Bone Cement

Background/Purpose: Polymethylmethacrylate (PMMA) and calcium phosphate (Ca-P) cements are widely used for arthroplasty surgery and augmentation of bone defects. However, aseptic implant loosening in absence of wear-induced osteolysis indicates an unfavourable interaction between the cement surface and human osteoblasts. Our underlying hypothesis is that cement surfaces directly modify cell viability, proliferation rate, and cell differentiation. Methods: To test this hypothesis, we examined primary human osteoblasts harvested from six individuals. These cells were pooled and subsequently seeded directly on cement pellets prepared from Palacos® R, Palacos® R+G, and Norian® Drillable cements. After incubation for 24 and 72 h, cell viability, proliferation rate, apoptosis rate, and cell differentiation were analysed. Results: Upon cultivation of human osteoblasts on cement surfaces, we observed a significantly reduced cell viability and DNA content compared to the control. Analysis of the apoptosis rate revealed an increase for cells on Palacos R and Norian Drillable, but a significant decrease on Palacos R+G compared to the control. Regarding osteogenic differentiation, significantly lower values of alkaline phosphatase enzyme activity were identified for all cement surfaces after 24 and 72 h compared to cultivation on tissue culture plastic, serving as control. Conclusions: In summary, these data suggest a limited biocompatibility of both PMMA and Ca-P cements, necessitating further research to reduce unfavourable cell-cement interactions and consequently extend implant survival.

Metal-on-metal total hip arthroplasty: risk factors for pseudotumours and clinical systematic evaluation.

The potential advantages of contemporary MoM THA implants include less volumetric wear with subsequent reduction of polyethylene wear-induced osteolysis and greater component stability with use of large-diameter femoral heads. However, there have been concerns regarding significantly elevated revision rates in MoM THA due to MoM-related complications such as adverse local tissue reaction (pseudotumour) formation. The increased failure rate in MoM hip arthroplasty is associated with the generation of biologically active, nanometer sized metal particles from the MoM bearing surfaces and taper junctions, which result in the development of a localized, adverse periprosthetic soft tissue response. The focus of this article is to provide an update on (1) implant, surgical and patient factors associated with adverse local tissue reactions (pseudotumours) and (2) the clinical systematic evaluation and management of patients with MoM hip arthroplasty based on the currently available evidence. There should be a low threshold to conduct a systematic clinical evaluation of patients with MoM hip arthroplasty as early recognition and diagnosis will allow the initiation of prompt and appropriate treatment. As a symptomatic MoM total hip arthroplasty may have intrinsic and extrinsic causes, patients should be evaluated systematically, utilizing risk stratification algorithms. Although specialized laboratory tests such as metal ion levels and cross sectional imaging modalities such as MARS MRI can be used to facilitate clinical decision making, over-reliance on any single investigative tool in the clinical decision-making process should be avoided. Further research is required to obtain a better understanding of implant and patient risk factors associated with tribocorrosion in MoM total hip arthroplasty.

A review of UHMWPE wear-induced osteolysis: the role for early detection of the immune response.

In a world where increasing joint arthroplasties are being performed on increasingly younger patients, osteolysis as the leading cause of failure after total joint arthroplasty (TJA) has gained considerable attention. Ultra-high molecular weight polyethylene wear-induced osteolysis is the process by which prosthetic debris mechanically released from the surface of prosthetic joints induces an immune response that favors bone catabolism, resulting in loosening of prostheses with eventual failure or fracture. The immune response initiated is innate in that it is nonspecific and self-propagating, with monocytic cells and osteoclasts being the main effectors. To date, detecting disease early enough to implement effective intervention without unwanted systemic side effects has been a major barrier. These barriers can be overcome using newer in vivo imaging techniques and modules linked with fluorescence and/or chemotherapies. We discuss the pathogenesis of osteolysis, and provide discussion of the challenges with imaging and therapeutics. We describe a positron emission tomography imaging cinnamoyl-Phe-(D)-Leu-Phe-(D)-Leu-Phe-Lys module, specific to macrophages, which holds promise in early detection of disease and localization of treatment. Further research and increased collaboration among therapeutic and three-dimensional imaging researchers are essential in realizing a solution to clinical osteolysis in TJA.

Dexamethasone-loaded TiO2 nanoparticles to locally target wear-debris induced inflammation

Event Abstract Back to Event Dexamethasone-loaded TiO2 nanoparticles to locally target wear-debris induced inflammation Melissa Rodrigues1, Stefano D. Perni1, 2, Alastair Sloan3 and Polina D. Prokopovich1, 2 1 Cardiff University, Pharmacy, United Kingdom 2 Massachusetts Institute of Technology,, Department of Biological Engineering, United States 3 Cardiff University, Dentistry School, United Kingdom Introduction: Like other parts of the body, joints become damaged or weakened by age, accidents or disease; joint degenerative diseases such arthritis affect the quality of life of millions worldwide.One of the ways to help such people is to have artificial joint replacement, although considered a successful procedure, these implants generate a large number of particles as result of wear with time/age. Such released particles, wear-debris, can compromise survival of joint implants by triggering an adverse inflammatory-response, which can lead to periprosthetic bone-loss, so called osteolysis[5]. During last decades, aseptic loosening due to osteolysis has been considered one of the most common causes for revision surgery[6]. Therefore the present project aims to develop an anti-inflammatory drug-eluting implant model system to prevent aseptic loosening following wear-induced osteolysis. Materials and Methods: Dexamethasone-loaded functionalized TiO2 nanoparticles were synthesized by covalently conjugating dexamethasone to carboxylic acid-amino functionalized nanoparticles. The functionalization of TiO2 nanoparticles was assessed by means of zeta potential measurements and thermogravimetric-analysis (TGA). Whilst dexamethasone release from TiO2 nanoparticles was quantified as function of time and pH using high-performance-liquid chromatography. Results and Discussion: The zeta potential measurements (Figure 1) show a more positive surface charge after amino-functionalization of TiO2 particles when compared to bare-TiO2. In contrast a more negative charge is observed after carboxyl and dexamethasone functionalization. As previously indicated in other studies, this is an indirect evidence showing that amino[2], carboxyl-acid groups[1], and dexamethasone[4] were successfully conjugated to TiO2-nanoparticles. Furthermore, TGA profile (Figure 2) shows an increase weight-loss after each step of functionalization. These results are related to an increase of organic material after each step of functionalization, thus confirming the successful attachment of functional groups and dexamethasone on the surface of TiO2-nanoparticles. After 24h, dexamethasone release from the functionalized-nanoparticles was suppressed at pH 7.0, 6.0 and 5.0; whilst at pH 4.0, a constant daily release of dexamethasone (10µg/mL) was observed over a period of 6 days (Figure 3). The results suggest that functionalized nanoparticles may remain stable and release more dexamethasone under acidic inflammatory conditions (pH=4)[3],[7] . Conclusions: Despite being one the most common complication after total joint replacement, there is no approved therapy to avoid aseptic-loosening following wear-induced osteolysis. Our study indicated that dexamethasone was successfully attached to TiO2 nanoparticles, with the advantage that the chemistry utilized could be applicable to conjugate other anti-inflammatory drugs. Furthermore, being controlled and constant drug release one of the most important features to modulate inflammation, dexamethasone-loaded-nanoparticles appears to be a potential approach to overcome the several limitations of current anti-osteolytic therapies e.g. lack of efficacy, systemic side-effects. Therefore more studies i.e. in vitro assessment of the anti-inflammatory effect are currently being performed by our research group to confirm safety and efficacy of drug-eluting-implant model system developed. Arthritis Research UK

Independent Evaluation of a Mechanical Hip Socket Navigation System in Total Hip Arthroplasty

BackgroundAcetabular cup malpositioning during total hip arthroplasty may lead to impingement, instability, wear-induced osteolysis, and increased rates of revision surgery. The purpose of this study was to independently evaluate the accuracy of acetabular cup orientation using a novel mechanical navigation device. MethodsAn adjustable, reusable mechanical navigation device was used in a consecutive series of patients. Angles (inclination and anteversion) were measured by 2 independent reviewers with a validated 2-dimensional/3-dimensional matching application using a preoperative computed tomographic scan and a postoperative plain film. ResultsThere were no outliers for inclination or anteversion for errors within 10° of the preoperative plan. There were 6 (12.8%) outliers for inclination and 11 (23.4%) for anteversion for errors within 5° of the preoperative plan. All patients simultaneously met both targets when an outlier was considered 10°, whereas 30 (63.8%) simultaneously met both targets when the criteria was tightened to 5°. The absolute errors for both inclination and anteversion were significantly less than both 5° and 10° (P<.001). ConclusionThis device reliably navigates acetabular cup inclination and anteversion individualized for each patient to within 10° of a preoperative plan. Outliers increased when this criteria is tightened to 5° but still appears to be more accurate than conventional acetabular cup component placement. Further research is warranted to assess the clinical impact of reducing outliers using this device.

Ceramic liner fracture and impingement in total hip arthroplasty.

Ceramic-on-ceramic bearing surfaces were developed to provide an alternate to metal-on-polyethylene to decrease wear-induced osteolysis in total hip arthroplasty patients. In an effort to decrease the risk of ceramic acetabular component fracture or damage during implantation, a raised metal rim was added. How many fractures or impingements have occurred in our population of patients with ceramic liners with raised rims? With IRB-approved consent, a case series was reviewed from a single center registry and 4 of 169 patients were identified who had revision hip surgery with the ceramic liner with a raised metal rim: one for ceramic liner fracture and three for metallosis, pain, and squeaking. Implant alignment and operative findings were reviewed. One ceramic liner fracture and three cases of metallosis from impingement of the femoral neck on the posterior elevated metal rim of the acetabular liner were observed at revision. The femoral neck in each patient had a divot that corresponded to a divot in the posterosuperior liner rim. Three of the four patients had audible squeaking or clicking prior to revision. A total of 3% of patients in this series had clinically significant impingement with this implant type. Acoustic phenomenon in a ceramic on ceramic bearing surface should be investigated with a cross-table lateral radiograph to evaluate component position. If symptomatic impingement is demonstrated, revision should be considered to avoid failure from metallosis or fracture.

Influence of Clinical and Radiological Variables on the Extent and Distribution of Periprosthetic Osteolysis in Total Hip Arthroplasty with a Hydroxyapatite-Coated Multiple-Hole Acetabular Component: A Magnetic Resonance Imaging Study

Polyethylene wear-induced osteolysis constitutes the most severe long-term complication of total hip arthroplasties (THA). Our aim was to assess through MRI the severity and growth pattern of osteolysis, as well as the influence clinical-radiographic variables exert. We analyzed 75 THA with an average evolution time of 13.67years. The implant was a titanium alloy, non-cemented, multiple-hole model with hydroxyapatite coating. Osteolysis was found with a peripheral pattern in 48 and a central pattern in 6; in 52 cases it was continuous, and in 4, isolated. Out of 118 screws, 20 exhibited lysis. There was a proportional correlation between osteolysis severity and wear rate with age, physical activity and acetabular abduction, as well as an association between said variables and peripheral and continuous patterns.

The Role of Oxidative Stress in Aseptic Loosening of Total Hip Arthroplasties

This study investigated the hypothesis that wear particle-induced oxidative stress initiates osteolysis after total hip arthroplasty (THA). Patient radiographs were scored for osteolysis and periprosthetic tissues were immunostained and imaged to quantify polyethylene wear, inflammation, and five osteoinflammatory and oxidative stress-responsive factors. These included high mobility group protein-B1 (HMGB1), cyclooxygenase-2 (COX2), inducible nitric oxide synthase (iNOS), 4-hydroxynonenal (4-HNE), and nitrotyrosine (NT). The results show wear debris correlated with inflammation, 4-HNE, NT and HMGB1, whereas inflammation only correlated with NT and HMGB1. Similar to wear debris and inflammation, osteolysis correlated with HMGB1. Additionally, osteolysis correlated with COX2 and 4-HNE, but not iNOS or NT. Understanding the involvement of oxidative stress in wear-induced osteolysis will help identify diagnostic biomarkers and therapeutic targets to prevent osteolysis after THA.

Highly Cross-Linked Polyethylene May Not Have an Advantage in Total Knee Arthroplasty

Long-term results after total knee replacement (TKR) with conventional and compression-molded polyethylene (PE) have been excellent. The introduction of highly cross-linked polyethylene (XLPE), which has demonstrated superior wear properties in total hip replacement (THR), has led to its recent use in TKR. However, the knee has a unique biomechanical environment characterized by large contact stresses and shear forces and differs from the highly conforming articulation (and primarily abrasive and adhesive wear) found in THR. For this reason, XLPE, with its decreased fatigue resistance and toughness compared to PE, may not be the best material to withstand these unique forces. This review and evaluation of the literature aims to answer the following questions. What are the advantages and disadvantages of XLPE in TKR? Does its success in THR ensure a favorable outcome in TKR? Does the increased cost of XLPE justify its use in TKR? A systematic literature review of MEDLINE, Science Direct, and Google Scholar databases was performed searching for advantages and disadvantages of XLPE in TKR. We found 18 biomechanical in vitro investigations and 3 clinical studies comparing conventional and XLPEs. We included levels I through IV published articles in peer-reviewed journals in English language. Several in vitro studies found XLPE to have significantly better wear properties compared to conventional PE. However, the two clinical investigations that directly compared conventional PE and XLPE found no difference in clinical or radiographic outcomes. Additionally, clinical studies with long-term follow-up on TKR with conventional PE did not find wear-induced osteolysis to be a major cause of failure. Four studies did find cost to be significantly higher for XLPE compared to conventional PE. Based on our review, we concluded that (1) the material properties of XLPE reduce adhesive and abrasive wear, but not the risk of crack propagation, deformation, pitting, and delamination found in TKR; (2) wear-induced osteolysis in TKR has not been found to be a major cause of failure at long-term follow-up; (3) mid-term follow-up studies show no difference in any recorded outcome measure between conventional PE and XLPE; and (4) XLPE is two to four times the cost of conventional PE without an improvement in clinical or radiographic outcomes. For these reasons, we currently cannot recommend the use of XLPE in TKR. Conventional compression-molded polyethylene with its outstanding long-term results should remain the material of choice in TKR.

Long-Term Performance of Ceramic and Metal Femoral Heads on Conventional Polyethylene in Young and Active Patients

Ceramic femoral heads produce less wear of the opposing polyethylene than do metal femoral heads in wear simulation studies. This is a matched-pair analysis of the wear of ceramic and metal femoral heads on conventional polyethylene in uncemented total hip replacements in young, active patients at a minimum of fifteen years of follow-up. From June 1989 to May 1992, thirty-one matched pairs of alumina ceramic or cobalt-chromium metal femoral heads were identified. Patients were matched on the basis of age, sex, body weight, diagnosis, and activity level. The mean age was 55 ± 9 years (range, twenty-three to sixty-five years) at the time of surgery. All procedures were performed with a posterolateral surgical approach by a single surgeon using press-fit Ranawat-Bernstein femoral stems, Harris-Galante-II acetabular cups, GUR 4150 conventional polyethylene (sterilized in argon), and 28-mm-diameter femoral heads. Wear measurements were performed by two independent observers using the computer-assisted Roman software. The average duration of follow-up was 17 ± 1.7 years (range, fifteen to twenty years). The mean Hospital for Special Surgery hip scores (and standard deviation) in the ceramic and metal groups were 39 ± 4 and 40 ± 3 at the time of final follow-up. The University of California Los Angeles activity score at the time of the final follow-up was 6 ± 2 for both groups. The mean wear rates for the ceramic group and the metal group were 0.086 ± 0.05 mm/yr and 0.137 ± 0.05 mm/yr, respectively (p = 0.0015). There was one reoperation in the ceramic group because of distal femoral osteolysis. There were three failures in the metal group, requiring isolated liner exchange in two hips and revision of the acetabular component in one hip because of wear-induced osteolysis and/or loosening that caused symptoms. Five hips in the ceramic group and six hips in the metal group had radiographic evidence of acetabular or femoral osteolysis, but none were symptomatic. Ceramic femoral heads produced significantly less wear on conventional polyethylene liners at the time of long-term follow-up than did metal heads in this matched-pair analysis of young and active patients with uncemented fixation.

Excellent Survivorship of the Morscher Monoblock Cup With a 28-mm Metasul-on-Metasul Bearing at a Mean of 5-Year Follow-Up

The Morscher monoblock cup is designed for optimal osteointegration and holds the potential for excellent long-term survival. The Metasul-on-Metasul bearing was introduced to eliminate wear-induced periprosthetic osteolysis. This study reviews 137 Morscher cups with a 28-mm Metasul-on-Metasul bearing used in primary THA at 5.1years (3.2-6.6) after implantation. One hundred thirty-seven cups were implanted in 119 patients. Three patients (2.2%) had died of unrelated causes, and 10 patients (8.0%) were lost to follow-up. The mean Harris Hip score was 89.8 and the mean WOMAC sum score was 18.5. No cases of acetabular osteolysis were found. The 5-year cup survival rate was 98.5%. The Morscher cup with a 28-mm Metasul-on-Metasul bearing used in uncemented THA showed no acetabular osteolysis and promising survivorship at intermediate-term follow-up.

Orthopedic wear debris mediated inflammatory osteolysis is mediated in part by NALP3 inflammasome activation

Activation of myeloid cells by orthopedic particulate debris is a key event in the pathogenesis of periprosthetic osteolysis and implant loosening after total joint replacement (TJR). Several lines of evidence implicate NACHT, LRR, and PYD domains-containing protein 3 (NALP3) inflammasome-mediated production of interleukin 1 beta (IL-1β) in the pathogenesis of clinical disorders ascribable to foreign particulate materials, including asbestos, silica, and urate crystals. Recent reports indicate that orthopedic polymer products and metallic particulates and ions may activate the same pathway. Here, we investigated the contribution of the NALP3 inflammasome to the pathogenesis of peri-implant osteolysis. Pharmaceutical and genetic perturbations of caspase-1 and inflammasome components were used to assess the role of the NALP3 inflammasome in IL-1β production and osteoclast formation by human monocytes and mouse macrophages in response to polymethylmethacrylate (PMMA) particle phagocytosis. The role of caspase-1 in a mouse calvarial model of particle-mediated osteolysis was assessed using µCT. Phagocytosis of PMMA particles induces caspase-1 dependent release of IL-1β from human monocytes and mouse macrophages. Importantly, using macrophages from mice deficient in components of the NALP3 inflammasome, we show PMMA-induced IL-1β production is strictly dependent on these components. Mice lacking caspase-1, the sole effector of the NALP3 inflammasome, show reduced orthopedic wear particle-induced calvarial osteolysis compared to wild-type controls. Absence of NALP3 inflammasome components fails to alter osteoclast formation in vitro. Our findings identify the NALP3 inflammasome as a critical mediator of orthopedic wear-induced osteolysis and as a viable therapeutic target for the treatment of periprosthetic osteolysis.

Identification of new alternative pathways and therapeutic targets in tnf-α-mediated inflammation and osteolysis induced by ultra-high molecular weight polyethylene

Identification of new alternative pathways and therapeutic targets in tnf-α-mediated inflammation and osteolysis induced by ultra-high molecular weight polyethylene