Role of polyethylene particles in peri-prosthetic osteolysis: A review

Mitigating polyethylene-mediated periprosthetic tissue inflammation through MEDSAH-grafting

Periprosthetic tissue inflammation is a challenging complication arising in joint replacement surgeries, which is often caused by wear debris from polyethylene (PE) components. In this study, we examined the potential biological effects of grafting a [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide (MEDSAH) polymer onto the surface of PE through a solvent-evaporation technique. J774A.1 macrophage-like cells and primary cultured mouse osteoblasts were treated with PE powder with or without the MEDSAH coating. MEDSAH grafting on PE substantially reduced the expression of pro-inflammatory cytokines and other mediators in primary cultured mouse osteoblasts, but did not significantly impact macrophage-mediated inflammation. Our findings suggest that a MEDSAH coating on PE-based materials has potential utility in mitigating periprosthetic tissue inflammation and osteolysis and preventing aseptic loosening in total joint replacements. Further research, including large-scale clinical trials and biomechanical analyses, is needed to assess the long-term performance and clinical implications of MEDSAH-coated PE-based materials in total joint arthroplasty.

The Measurement of the Oxidative Index of Polyethylene Obtained during Revision Hip Arthroplasty and Assessment of Its Variability Depending on the Degree of Osteolysis, Implantation Time, as Well as the Size and Material of the Utilized Head

Background/Objectives: Aseptic loosening is the leading cause of late revision in total hip arthroplasty, primarily due to degenerative oxidation of polyethylene components, leading to wear particle formation and periacetabular osteolysis. This study aimed to analyze the oxidation levels in polyethylene liners and cemented cups retrieved from revision surgeries using Fourier-transform infrared spectroscopy (FTIR) and to explore the correlation between oxidation levels and factors such as head size, head material, fixation method, and implant survival time. Methods: Polyethylene liners and cups were analyzed post-revision surgery to assess oxidation levels, which were then compared to periacetabular bone loss measured by the Paprosky classification. This study evaluated the impact of head size (28 mm vs. 32 mm), head material (ceramic vs. metal), and fixation methods on oxidation. The relationship between the mean oxidation index (OI) and implant survival time was also investigated. Results: There was a significant positive correlation between the mean oxidation index of the polyethylene components and the severity of periacetabular osteolysis according to the Paprosky scale. While the mean OI for samples articulating with ceramic heads was lower than for those with metal heads, and the mean OI for samples with a 32 mm head size was lower than for those with a 28 mm size, these differences were not statistically significant. Furthermore, the fixation method did not affect the oxidation index, and no correlation was found between OI and the survival time of the implants. Conclusions: This study confirms a direct correlation between polyethylene oxidation and periacetabular osteolysis in hip replacements, highlighting the importance of material choice and design in potentially reducing the risk of aseptic loosening. Despite the lack of significant differences in oxidation levels based on head material and size, these factors may still play a role in the long-term outcome of hip arthroplasty, warranting further investigation.

Massive Periprosthetic Osteolysis Spreads to the Soft Tissue and Pelvic Region after Primary Total Hip Replacement: A Case Report

Introduction

Periprosthetic osteolysis (PPOL) is a serious complication after total hip replacement and requires immediate action to prevent further spread to nearby tissues and has the opportunity to restore hip function successfully. We present the case of PPOL of a patient with a challenging course of treatment.

Case Report

We report a 75-year-old patient with PPOL that spreads to the soft tissues and pelvic region 14 years after primary total hip arthroplasty. At all stages of treatment, an elevated neutrophil-dominant cell count was detected in the analysis of synovial fluid aspiration of the left hip joint without detection of microbiological culture. Due to severe bone loss and general patient condition, no further surgical treatment was indicated, and there is no clear vision of future actions.

Conclusion

Management of severe PPOL can be challenging, as there are limited surgical treatment options with a good long-term prognosis. If an osteolytic process is suspected, it should be treated as soon as possible to avoid more severe progression of the complications.

Wear Analysis of Tibial Inserts Made of Highly Cross-Linked Polyethylene Supplemented with Dodecyl Gallate before and after Accelerated Aging

The wear of the tibial insert is one of the primary factors leading to the failure of total knee arthroplasty. As materials age, their wear performance often degrades. Supplementing highly cross-linked polyethylene (HXLPE) with dodecyl gallate (DG) can improve the oxidation stability of tibial inserts for use in total knee arthroplasty (TKA). This study aimed to evaluate the wear resistance of HXLPE supplemented with DG (HXLPE-DG) tibial inserts before and after accelerated aging. HXLPE-DG tibial inserts were subjected to wear testing of up to 5 million loading cycles according to ISO 14243, and the resulting wear particles were analyzed according to ISO 17853. The wear rate, number, size, and shape of the wear particles were analyzed. The average wear rate of the unaged samples was 4.39 ± 0.75 mg/million cycles and was 3.22 ± 1.49 mg/million cycles for the aged samples. The unaged tibial inserts generated about 2.80 × 107 particles/mL following the wear test, but this was considerably lower for the aged samples at about 1.35 × 107 particles/mL. The average equivalent circle diameter (ECD) of the wear particles from the unaged samples was 0.13 μm (max: 0.80 μm; min: 0.04 μm), and it was 0.14 μm (max: 0.66 μm; min: 0.06 μm) from the aged samples. Moreover, 22.1% of the wear particles from the unaged samples had an aspect ratio (AR) of >4 (slender shape), while this was 15.4% for the aged samples. HXLPE-DG improves the wear performance of the material over time. HXLPE-DG is a novel material that has been demonstrated to have antiaging properties and high wear resistance, making it a promising candidate for use in TKA. Nevertheless, the results are preliminary and will be clarified in further studies.

Changes in Metabolism and Mitochondrial Bioenergetics during Polyethylene-Induced Osteoclastogenesis

Changes in mitochondrial bioenergetics are believed to take place during osteoclastogenesis. This study aims to assess changes in mitochondrial bioenergetics and reactive oxygen species (ROS) levels during polyethylene (PE)-induced osteoclastogenesis in vitro. For this purpose, RAW264.7 cells were cultured for nine days and allowed to differentiate into osteoclasts in the presence of PE and RANKL. The total TRAP-positive cells, resorption activity, expression of osteoclast marker genes, ROS level, mitochondrial bioenergetics, glycolysis, and substrate utilization were measured. The effect of tocotrienols-rich fraction (TRF) treatment (50 ng/mL) on those parameters during PE-induced osteoclastogenesis was also studied. During PE-induced osteoclastogenesis, as depicted by an increase in TRAP-positive cells and gene expression of osteoclast-related markers, higher proton leak, higher extracellular acidification rate (ECAR), as well as higher levels of ROS and NADPH oxidases (NOXs) were observed in the differentiated cells. The oxidation level of some substrates in the differentiated group was higher than in other groups. TRF treatment significantly reduced the number of TRAP-positive osteoclasts, bone resorption activity, and ROS levels, as well as modulating the gene expression of antioxidant-related genes and mitochondrial function. In conclusion, changes in mitochondrial bioenergetics and substrate utilization were observed during PE-induced osteoclastogenesis, while TRF treatment modulated these changes.

The lexicon for periprosthetic bone loss versus osteolysis after cervical disc arthroplasty: a systematic review

BACKGROUND

Periprosthetic bone loss is a common observation following arthroplasty. Recognizing and understanding the nature of bone loss is vital as it determines the subsequent performance of the device and the overall outcome. Despite its significance, the term "bone loss" is often misused to describe inflammatory osteolysis, a complication with vastly different clinical outcomes and treatment plans. Therefore, the goal of this review was to report major findings related to vertebral radiographic bone changes around cervical disc replacements, mitigate discrepancies in clinical reports by introducing uniform terminology to the field, and establish a precedence that can be used to identify the important nuances between these distinct complications.

METHODS

A systematic review of the literature was conducted following PRISMA guidelines, using the keywords "cervical," "disc replacement," "osteolysis," "bone loss," "radiograph," and "complications." A total of 23 articles met the inclusion criteria with the majority being retrospective or case reports.

RESULTS

Fourteen studies reported periprosthetic osteolysis in a total of 46 patients with onset ranging from 15-96 months after the index procedure. Reported causes included: metal hypersensitivity, infection, mechanical failure, and wear debris. Osteolysis was generally progressive and led to reoperation. Nine articles reported non-inflammatory bone loss in 527 patients (52.5%), typically within 3-6 months following implantation. The reported causes included: micromotion, stress shielding, and interrupted blood supply. With one exception, bone loss was reported to be non-progressive and had no effect on clinical outcome measures.

CONCLUSIONS

Non-progressive, early onset bone loss is a common finding after CDA and typically does not affect the reported short-term pain scores or lead to early revision. By contrast, osteolysis was less common, presenting more than a year post-operative and often accompanied by additional complications, leading to revision surgery. A greater understanding of the clinical significance is limited by the lack of long-term studies, inconsistent terminology, and infrequent use of histology and explant analyses. Uniform reporting and adoption of consistent terminology can mitigate some of these limitations. Executing these actionable items is critical to assess device performance and the risk of revision.

LEVEL OF EVIDENCE IV

Diagnostic: individual cross-sectional studies with consistently applied reference standard and blinding.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Prednisone prevents particle induced bone loss in the calvaria mouse model

INTRODUCTION

Glucocorticoids are essential in the treatment of many chronic inflammatory and malignant diseases but are known to have detrimental effects on bone. This study aimed to investigate the effects of prednisone on osteoclast functioning in vivo in the calvaria particle-induced bone loss mouse model.

METHODS

12-week-old male C57BL6/J mice received subcutaneously implanted prednisone (2.5 mg/d, 60 day release (n = 14)) or placebo pellets (n = 10). Osteolysis of the calvaria bone was induced two weeks later by application of ultra-high-molecular-weight polyethylene- (UHMWPE) particles to the dome (vs sham operation). The extent of osteolysis was determined histologically and by micro-computer tomography.

RESULTS

Prednisone significantly inhibited particle-induced osteolysis in the skull. No significant difference in osteoclast numbers was seen in mice with prednisone vs placebo treatment. Prednisone treatment alone without particle application did not reduce bone mineral density or deterioration in bone microarchitecture parameters.

CONCLUSIONS

The calvaria particle-induced bone loss mouse model can be adapted to investigate osteoclast activity in vivo and the effect of prednisone on osteoclasts. In this preventive experimental design, the application of short-term low-dose prednisone has osteoprotective effects without measurable systemic side effects on bone parameters.

The effect of strontium ranelate on titanium particle-induced periprosthetic osteolysis regulated by WNT/β-catenin signaling in vivo and in vitro

Aseptic loosening following periprosthetic osteolysis is the primary complication that limits the lifetime of total joint arthroplasty (TJA). The wear particles trigger a chronic inflammation response in the periprosthetic tissue and turn over the bone balance to bone resorption. The present study aimed to investigate the possible effect and mechanism of strontium ranelate (SR), a clinically safe drug for osteoporosis, on particle-induced periprosthetic osteolysis. Thirty-six female C57BL/6j mice underwent tibial Ti-nail implantation to establish an animal model of aseptic loosening. After 12 weeks, micro-CT results showed that strontium ranelate could inhibit periprosthetic bone resorption. In vitro, Ti particles were used to stimulate RAW264.7 cell line to collect conditioned medium, and co-culture MC3T3-E1 cell line with conditioned medium to establish a cell model of aseptic loosening. The results of alkaline phosphatase (ALP) detection, immunofluorescence, and flow cytometry demonstrated that strontium ranelate could regulate the expression of OPG/RANKL, promote differentiation and mineralization, and inhibit apoptosis in osteoblasts. Moreover, we revealed that SR's exerted its therapeutic effect by down-regulating sclerostin, thereby activating the Wnt/β-catenin signal pathway. Therefore, this research suggests that strontium ranelate could be a potential drug for the prevention and treatment of particle-induced aseptic loosening post-TJA.

The Genetic Variations Associated With Time to Aseptic Loosening After Total Joint Arthroplasty

BACKGROUND

Total joint arthroplasty (TJA) is one of the most frequent surgical procedures performed in modern hospitals, and aseptic loosening is the most common indication for revision surgeries. We conducted a systemic exploration of potential genetic determinants for early aseptic loosening.

METHODS

Data from 423 patients undergoing TJA were collected and analyzed. Three analytical groups were formed based on joint arthroplasty status. Group 1 were TJA patients without symptoms of aseptic loosening of at least 1 year, group 2 were patients with primary TJA, and group 3 were patients receiving revision surgery because of aseptic loosening. Genome-wide genotyping comparing genotype frequencies between patients with and without aseptic loosening (group 3 vs groups 1 and 2) was conducted. A case-control association analysis and linear modeling were applied to identify the impact of the identified genes on implant survival with time to the revision as an outcome measure.

RESULTS

We identified 52 single-nucleotide polymorphisms (SNPs) with a genome-wide suggestive P value less than 10^-5 to be associated with the implant loosening. The most remarkable odds ratios (OR) were found with the variations in the IFIT2/IFIT3 (OR, 21.6), CERK (OR, 12.6), and PAPPA (OR, 14.0) genes. Variations in the genotypes of 4 SNPs-rs115871127, rs16823835, rs13275667, and rs2514486-predicted variability in the time to aseptic loosening. The time to aseptic loosening varied from 8 to 16 years depending on the genotype, indicating a substantial effect of genetic variance.

CONCLUSION

Development of the aseptic loosening is associated with several genetic variations and we identified at least 4 SNPs with a significant effect on the time for loosening. These data could help to develop a personalized approach for TJA and loosening management.

Evidence for Gender-Specific Bone Loss Mechanisms in Periprosthetic Osteolysis

Osteolysis adjacent to total hip replacement (THR) prostheses is a major cause of their eventual failure. Periprosthetic osteolysis is associated with the production of bioactive particles, produced by the wear of articulating prosthesis surfaces. Wear particles invade the periprosthetic tissue, inducing inflammation and bone resorption. Previous studies have shown that osteocytes, the most numerous cell type in mineralised bone, can respond to wear particles of multiple orthopaedic material types. Osteocytes play important roles in bone resorption, regulating bone resorption by osteoclasts and directly through osteocytic osteolysis, also known as perilacunar remodelling. In this study, we perform a histological analysis of bone biopsies obtained from cohorts of male and female patients undergoing either primary THR surgery or revision THR surgery for aseptic loosening. The osteocyte lacunae area (Ot.Lac.Ar) and percentage lacunar area/bone area (%Ot.Lac.Ar/B.Ar) were significantly larger overall in revision THR bone than bone from similar sites in primary THR. Analysis by patient gender showed that increased Ot.Lac.Ar, indicative of increased perilacunar remodelling, was restricted to female revision samples. No significant differences in osteoclast parameters were detectable between the cohorts. These findings suggest previously unrecognised gender-specific mechanisms of bone loss in orthopaedic wear particle-induced osteolysis in humans.

To cement or not to cement acetabular cups in total hip arthroplasty: a systematic review and re-evaluation

INTRODUCTION

Total Hip Arthroplasty (THA) in the treatment of primary osteoarthritis of the hip has evolved to a very safe and cost-effective intervention with revision rates below 5% after 10 years. To this day, however, controversy remains on whether or not to cement the acetabular cup.

METHODS

A comprehensive PubMed search of the English literature for studies published between 2007 and 2018 was performed. Studies comparing the clinical (revision rate, functionality), radiological (wear) or economic (cost) differences between cemented (cemented stem with cemented cup) and hybrid (cemented stem with uncemented cup) prostheses for primary osteoarthritis of the hip were identified as eligible.

RESULTS

A total of 1032 studies were identified whereof twelve were included for qualitative synthesis. All studies concerning the risk of revision were based on registry data, covering a total of 365,693 cups. Cemented prostheses had a similar or lower risk of revision compared to hybrid prostheses in every study, but performed slightly worse on functionality and quality of life. While cemented prostheses were the cheapest option, hybrids were the most cost-effective.

DISCUSSION

The widespread preference for cementless fixation of the acetabulum cannot be explained by a superior survival of cementless or hybrid models. Irrespective of age, cemented fixation of the acetabulum remains the gold standard to which other techniques should be compared.

Osteocytes respond to particles of clinically-relevant conventional and cross-linked polyethylene and metal alloys by up-regulation of resorptive and inflammatory pathways

Periprosthetic osteolysis is a major cause of implant failure in total hip replacements. Aseptic loosening caused by osteolytic lesions is associated with the production of bioactive wear particles from the articulations of implants. Wear particles infiltrate the surrounding tissue of implants, promoting inflammation as well as bone resorption. Osteocytes have been shown to both regulate physiological osteoclastogenesis and directly remodel their perilacunar bone matrix by the process of osteocytic osteolysis. We hypothesise that osteocytes respond to wear debris of orthopaedic implant materials by adopting a pro-catabolic phenotype and thus contribute to periprosthetic osteolysis through the known pathways of bone loss. Osteocyte responses to particles derived from clinically relevant materials, ultra-high molecular weight polyethylene (UHMWPE), highly cross-linked polyethylene (XLPE) and metal alloys, Ti6Al4V and CoCrMo, were examined in vitro in human primary osteocyte-like cultures. Osteocyte-like cells exposed to both polyethylene and metal wear particle types showed upregulated expression of catabolic markers associated with osteocytic osteolysis, MMP13, carbonic anhydrase 2 (CA2) and cathepsin K (CTSK). In addition, pro-osteoclastogenesis markers RANKL and M-CSF were induced, as well as the expression of pro-inflammatory cytokines, IL-6 and TNFα, albeit with different kinetics. These findings suggest a previously unrecognised action of wear particles of multiple orthopaedic materials on osteocytes, and suggest a multifaceted role for osteocytes in periprosthetic osteolysis. STATEMENT OF SIGNIFICANCE: This study addresses periprosthetic osteolysis, a major clinical problem leading to aseptic loosening of orthopaedic implants. It is well accepted that wear particles of polyethylene and of other implant materials stimulate the activity of bone resorbing osteoclasts. Our recent work provided evidence that commercial particles of ultra-high molecular weight polyethylene (UHMWPE) stimulated osteocytes to adopt a bone catabolic state. In this study we demonstrate for the first time that particles derived from materials in clinical use, conventional UHMWPE, highly cross-linked polyethylene (XLPE), and Ti6Al4V and CoCrMo metal alloys, all stimulate human osteocyte activities of osteocyte-regulated osteoclastogenesis, osteocytic osteolysis, proinflammatory responses, osteocyte apoptosis, albeit to varying extents. This study provides further mechanistic insight into orthopaedic wear particle mediated bone disease in terms of the osteocyte, the most abundant and key controlling cell type in bone.

Dysregulated expression of antioxidant enzymes in polyethylene particle-induced periprosthetic inflammation and osteolysis

Small wear particles (0.1–10 μm) in total joint replacement are generally considered as the major causative agent leading to periprosthetic inflammation and osteolysis. However, little is known about the roles of larger wear particles (10–100 μm) in periprosthetic inflammation and osteolysis. Additionally, although ample studies demonstrated that increased oxidative stress is critically involved in particle-induced inflammation and osteolysis, detailed changes in antioxidant enzymes expression in the disease development remain largely unclear. Herein, we used a rat knee prosthesis model to assess effects of polyethylene (PE) particles (20–60 μm) on the levels of oxidative stress markers such as malondialdehyde (MDA) and total antioxidant capacity (TAC) in blood plasma, and on the expression profiles of antioxidant enzymes in knee joint tissues. In combination with a forced-exercise intervention for all surgical rats, we found that the rat groups treated with both artificial joint and PE particles exhibited higher MDA levels and lower TAC levels, together with lower levels of physical activity and higher levels of inflammatory markers, than the sham group and the groups receiving artificial joint or PE particles alone at weeks 20–24 post-operatively. Dose-response relationships between the exposure to PE particles and the induction of oxidative stress and inflammation were also observed in the artificial joint/PE groups. Under such conditions, we unexpectedly found that most of antioxidant enzymes displayed pronounced up-regulation, with concomitant induction of inflammatory and osteoclast-inducing factors (including IL-1β, NF-κB and RANKL), in the artificial joint/PE groups as compared to the sham, artificial joint only, or PE only group. Only a few antioxidant enzymes including SOD2 and GPx2 showed down-regulation. Collectively, our findings demonstrate that implantation of artificial joint along with large PE particles synergistically trigger the induction of oxidative stress; however, down-regulation of many antioxidant enzymes may not necessarily occur during the disease development.

Differential proteomic analysis of synovial fluid from hip arthroplasty patients with a pseudotumor vs. Periprosthetic osteolysis

Adverse tissue reactions to metal implants, including pseudotumors, can compromise implant functionality and survivorship. The identification of specific proteins in the synovial fluid (SF) of hip arthroplasty patients with a pseudotumor may lead to a better understanding of the underlying pathomechanisms. The objective of the present study was to compare the protein content of SF from patients with a short-term metal-on-metal hip implant associated with a pseudotumor and patients with a long-term metal-on-polyethylene hip implant associated with periprosthetic osteolysis. Discovery proteomics was used to identify differentially abundant proteins in albumin-depleted SF. In toto, 452 distinct proteins (present in at least half of the patients in one or both groups) were identified. Thirty of these 452 proteins were differentially abundant between the two groups, including two potential biomarkers: 6-phosphogluconate dehydrogenase (which plays a major protective role against oxidative stress) for the pseudotumor group, and scavenger receptor cysteine-rich type 1 protein M130 (which is involved in low-grade inflammation) for the periprosthetic osteolysis group. Other differentially abundant proteins identified suggest the presence of an adaptive immune response (particularly a type-IV hypersensitivity reaction), necrosis, and greater oxidative stress in patients with a pseudotumor. They also suggest the presence of an innate immune response, oxidative stress, tissue remodeling, and apoptosis in both patient groups, although differences in the specific proteins identified in each group point to differences in the pathomechanisms. Overall, results provide insights into the molecular mechanisms underlying metal-related pseudotumors and periprosthetic osteolysis, and may ultimately help elucidate pseudotumor etiology and assess the risk that asymptomatic pseudotumors will develop into an aggressive lesion. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1849-1859, 2018.

Influence of analyzed lubricant volumes on the amount and characteristics of generated wear particles from three different types of polyethylene liner materials

The articulating components of artificial joints consist mainly of metals, ceramics, or polymers. Resulting abrasive wear particles can promote osteolysis and aseptic loosening of the endo-prosthetic implants. Ultra-high-molecular-weight-polyethylene is the material used most for bearing couples in total hip replacement. In the present study, three types of polyethylene (PE) liners varying in material composition, i.e., (1) conventional PE (C-PE), (2) sequentially cross-linked PE (SX-PE), (3) cross-linked PE blended with vitamin E (EX-PE) articulating with two types of femoral heads were used. After ultrasound treatment of each simulator lubricant, different concentrations (0.1/0.25/0.5/1.0 mL) were taken and dissolved in hydrochloric acid (37%) in a similar manner. The aim was to analyze the characteristics of wear particles generated in a hip simulator, with respect to different volumes of the lubricant. Within the scope of particle analysis, distinct alterations for particle characteristics were determined in the lubricant volumes and types of PE material used. A significant decrease in particle number for SX-PE liners, compared to the C-PE inserts and even more for EX-PE inserts, was detected at each lubricant volume. Particle morphologies varied depending on PE material. Alterations in particle size and other morphologic parameters between the four tested volumes, could be proven for each PE type. In general, particle sizes and parameters (e.g., length and width) increased with increasing serum volumes. In conclusion, the chosen volume of the simulator lubricant used for particle analysis has a crucial influence on detected particle number, size distribution, and morphologic parameters. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1299-1306, 2018.

Histological Analysis of Early Osteolysis in Total Ankle Arthroplasty

BACKGROUND

The purpose of this study was to perform a histological comparative analysis of tibiotalar joint samples taken from areas of osteolysis adjacent to total ankle arthroplasties vs control synovial specimens to determine the reaction to and presence of polyethylene (PE) particles.

METHODS

A total of 57 pathology samples were identified in the osteolysis group, while 11 were identified in the control group. For each sample, hematoxylin and eosin, Oil Red O (ORO), and macrophage marker CD163-stained slides were created. Polarized light and ORO stain were used to identify PE particles. The presence of metal particles and giant cell reaction to PE particles were also scored.

RESULTS

Macrophages, PE particles, metallosis, and foreign body giant cell reaction scores were significantly higher in the osteolysis group compared with the control group. In the osteolysis group, ORO staining was positive in 93% (53/57), birefringent material was present in 96.5% (55/57), and macrophage infiltrates were present in 96.5% (55/57). Foreign body giant cell reaction with giant cells surrounding PE particles was present in 49.1% (28/57) of osteolytic specimens. The presence of foreign body giant cell reaction was associated with significantly higher macrophage, ORO, and polarizable material scores. The average time to surgery for osteolysis from the index ankle replacement was 6.0 (range, 0-15) years for the 57 patients in the osteolysis group.

CONCLUSION

This study is the largest ankle arthroplasty histological analysis to show that areas of osteolysis consist of abundant polyethylene wear particles, present both intracellularly and extracellularly. Furthermore, these areas were associated with a CD163⁺ macrophage infiltrate and frequently a foreign body reaction with giant cells engulfing PE particles. It is likely that implant wear particles play a significant role in osteolysis based on the histopathology.

LEVEL OF EVIDENCE

Level III, retrospective comparative series.

Patient-specific hip geometry has greater effect on THA wear than femoral head size

In vivo linear penetration in total hip arthroplasty (THA) exhibits similar values for 28mm and 32mm femoral head diameter with considerable variations between and within the studies. It indicates factors other than femoral head diameter influence polyethylene wear. This study is intended to test the effect of patient׳s individual geometry of musculoskeletal system, acetabular cup orientation, and radius of femoral head on wear. Variation in patient׳s musculoskeletal geometry and acetabular cup placement is evaluated in two groups of patients implanted with 28mm and 32mm THA heads. Linear wear rate estimated by mathematical model is 0.165-0.185mm/year and 0.157-0.205mm/year for 28 and 32mm THA heads, respectively. Simulations show little influence femoral head size has on the estimated annual wear rate. Predicted annual linear wear depends mostly on the abduction angle of the acetabular cup and individual geometry of the musculoskeletal system of the hip, with the latter having the greatest affect on variation in linear wear rate.

Particle Disease: A Current Review of the Biological Mechanisms in Periprosthetic Osteolysis After Hip Arthroplasty

Background:

Inflammatory responses to wear debris cause osteolysis that leads to aseptic prosthesis loosening and hip arthroplasty failure. Although osteolysis is usually associated with aseptic loosening, it is rarely seen around stable implants. Aseptic implant loosening is a simple radiologic phenomenon, but a complex immunological process. Particulate debris produced by implants most commonly causes osteolysis, and this is called particle-associated periprosthetic osteolysis (PPO).

Objective:

The objective of this review is to outline the features of particle-associated periprosthetic osteolysis to allow the physician to recognise this condition and commence early treatment, thereby optimizing patient outcome.

Methods:

A thorough literature search was performed using available databases, including Pubmed, to cover important research published covering particle-associated PPO.

Results:

Although osteolysis causes bone resorption, clinical, animal, and in vitro studies of particle bioreactivity suggest that particle-associated PPO represents the culmination of several biological reactions of many cell types, rather than being caused solely by the osteoclasts. The biological activity is highly dependent on the characteristics and quantity of the wear particles.

Conclusion:

Despite advances in total hip arthroplasty (THA), particle-associated PPO and aseptic loosening continue to be major factors that affect prosthetic joint longevity. Biomarkers could be exploited as easy and objective diagnostic and prognostic targets that would enable testing for osteolysis after THA. Further research is needed to identify new biomarkers in PPO. A comprehensive understanding of the underlying biological mechanisms is crucial for developing new therapeutic interventions to reverse or suppress biological responses to wear particles.

Evidence that osteocyte perilacunar remodelling contributes to polyethylene wear particle induced osteolysis

Periprosthetic osteolysis (PO) leading to aseptic loosening, is the most common cause of failure of total hip replacement (THR) in the mid- to long-term. Polyethylene (PE) particulates from the wear of prosthesis liners are bioactive and are implicated in the initiation and or progression of osteolysis. Evidence exists that cells of the osteoblast/osteocyte lineage are affected by PE particles and contribute to the catabolic response by promoting osteoclastic bone resorption. In this study, we hypothesised that osteocytes contribute directly to PO by removing bone from their perilacunar matrix. Osteocyte responses to ultra-high molecular weight PE (UHMWPE) particles were examined in vitro in human primary osteocyte-like cultures, in vivo in the mouse calvarial osteolysis model, and in the acetabulum of patients undergoing revision total hip replacement (THR) surgery for PO. Osteocytes exposed to UHMWPE particles showed upregulated expression of catabolic markers, MMP-13, carbonic anhydrase 2 (CA2), cathepsin K (CTSK) and tartrate resistant acid phosphatase (TRAP), with no effect on cell viability, as assessed by Caspase 3 activity. Consistent with this catabolic activity causing perilacunar bone loss, histological analysis of calvarial sections from mice exposed to UHMWPE revealed a significant (p<0.001) increase in osteocyte lacunar area (Lac.Ar) compared to sham-operated animals. Furthermore, acetabular biopsies from patients with PO also showed significantly (p<0.001) increased osteocyte lacunar size in trabecular bone adjacent to PE particles, compared with osteocyte lacunar size in bone from primary THR patients. Together, these findings suggest a previously unrecognised action of UHMWPE wear particles on osteocytes, which directly results in a loss of osteocyte perilacunar bone. This action may exacerbate the indirect pro-osteoclastic action of UHMWPE-affected osteocytes, previously shown to contribute to aseptic loosening of orthopaedic implants.

STATEMENT OF SIGNIFICANCE

This study addresses the clinical problem of periprosthetic osteolysis, bone loss in response to polyethylene wear particles derived from materials used in orthopaedic implants. Periprosthetic osteolysis has been thought to be due largely to wear particles stimulating the activity of bone resorbing osteoclasts. However, in this study we demonstrate for the first time that polyethylene particles stimulate another type of bone loss, mediated by the direct activity of bone mineral embedded osteocytes, termed osteocytic osteolysis or osteocyte perilacunar remodelling. This study provides new mechanistic insight into wear-particle mediated bone loss and represents a new paradigm for the way in which bone cells, namely osteocytes, the key controlling cell type in bone, react to biomaterials.

Thin-Walled Cross-Linked Acetabular Liners Need Not Exhibit Reduced Locking Strength

Use of larger diameter femoral heads has emerged as a promising strategy to reduce the risk of dislocation after total hip arthroplasty, but thinning the walls of cross-linked ultra-high-molecular-weight polyethylene (UHMWPE) acetabular liners to accommodate these larger heads may compromise the locking mechanism of the liner. The purpose of this study was to test the mechanical integrity of the locking mechanism in cross-linked and re-melted UHMWPE acetabular components with reduced wall thickness. The locking mechanism of cross-linked (100 kGy/re-melted) acetabular liners in sizes 50/28, 50/36, and 52/36 mm of 1 design was evaluated by lever-out tests and torsion tests. Torsion tests were performed at 2 angles to isolate the liner's locking tabs independent of the contribution of its central post. Lever-out testing demonstrated nominally reduced failure strength in 50/36-mm liners (13.3 N · m) compared with 50/28-mm liners (12.3 N · m; P=.0502), whereas the lever-out strength of 52/36-mm liners was 12.2±0.94 N · m. Failure torques were similar between 50/28- and 50/36-mm liners at 45° and 90°, but the failure torque of size 52/36-mm liners was significantly higher at each angle. The use of larger diameter femoral heads does not compromise the locking mechanism of thinned MicroSeal (Signal Medical Corp, Marysville, Michigan) acetabular liners. Use of a cross-linked UHMWPE acetabular liner, with a locking mechanism that is not compromised when the liner is thinned to a thickness of at least 2.86 mm, appears to be a biomechanically sound construct when articulated with large diameter femoral heads.

Is Hemiresurfacing Arthroplasty for Osteonecrosis of the Hip a Viable Solution?

We conducted a systematic review of published studies that evaluated the outcomes of hemiresurfacing arthroplasty (HRA) in patients with osteonecrosis (ON). A structured literature review of multiple databases referenced articles from 1950 to 2014. A total of 430 patients from 14 published studies were identified. The mean duration of follow-up after the HRA was 69 months. At the final follow-up, the mean postoperative Harris hip score was 85. Overall clinical success rate was 74%. A total of 102 (21%) revision surgeries were required after the index procedure. Our study has helped to further elucidate the outcomes of HRA in patients with ON. We believe that HRA in young, active patients is a viable option providing symptomatic relief and functional improvement.

Evaluation and management of the painful total ankle arthroplasty

Total ankle arthroplasty (TAA) is an increasingly popular treatment option for patients with end-stage ankle arthritis. Although improved short- and long-term clinical and radiographic outcomes have been achieved with TAA, revision surgery may be necessary in the setting of aseptic loosening, subsidence, impingement, arthrofibrosis, or infection. Factors such as patient selection, implant design, and surgical technique can all contribute to TAA failure. Treatment of patients with a painful TAA is complex and requires careful consideration of symptom history, workup, and nonsurgical and surgical treatment options. Surgical management of failed TAA includes arthrodesis, revision surgery, or below-knee amputation.

Are there biological markers for wear or corrosion? A systematic review

BACKGROUND

Identification of biomarkers associated with wear and tribocorrosion in joint arthroplasty would be helpful to enhance early detection of aseptic loosening and/or osteolysis and to improve understanding of disease progression. There have been several new reports since the last systematic review (which covered research through mid-2008) justifying a new assessment.

QUESTIONS/PURPOSES

We sought to determine which biomarkers have the most promise for early diagnosis and monitoring of aseptic loosening and/or osteolysis related to wear or corrosion in total joint arthroplasty.

METHODS

We performed a systematic review using MEDLINE and EMBASE databases, covering the period through December 2013, and identified 1050 articles. We restricted the definition of biomarker to biomolecules and imaging parameters useful for diagnosis and monitoring of disease progression, only including articles in English. We chose 65 articles for full review, including 44 from the original search and 21 from subsequent hand searches. We used the 22 articles in which patients with total joint arthroplasty who had aseptic loosening and/or periimplant osteolysis unrelated to sepsis had been compared with patients with total joint arthroplasty with stable implants. There were 90 comparisons of these two patient populations involving 35 different biomarkers.

RESULTS

Diagnostic accuracy was assessed in nine of the 90 comparisons with the highest accuracy found for tartrate-resistant acid phosphatase 5b (0.96), although a separate comparison for this biomarker found a lower accuracy (0.76). Accuracy of > 0.80 was also found for crosslinked n-telopeptide of type I collagen, osteoprotegerin, and deoxypyridinoline. The most studied markers, tumor necrosis factor-α and interleukin-1β, were found to differ in the affected and control groups in < 30% of the comparisons. Thirty of the 35 biomarkers were studied in four or fewer separate comparisons with nearly half of the biomarkers (17) studied in only one comparison. Many of the comparisons were not able to eliminate a number of confounding variables, and there was only one prospective study.

CONCLUSIONS

Currently, there are no validated biomarkers for early diagnosis and monitoring of the biological sequelae of wear or tribocorrosion, although there are some promising leads, including markers of bone turnover.

Human polyethylene granuloma tissues inhibit bone healing in a novel xenograft animal model

During revision of a conventional polyethylene joint replacement, surgeons usually remove the source of osteolysis (polyethylene) but cannot always remove all of the polyethylene granuloma tissues. We developed a human/rat xenograft model to investigate the effects of polyethylene granuloma tissues on bone healing. Human osteoarthritic and periprosthetic tissues collected during primary and revision hip arthroplasty surgeries were transplanted into the distal femora of athymic nude rats. After 3 weeks in vivo, there was a significant difference in the bone volume fraction (Vf ) between empty, primary, and revision defects (p = 0.02), with a lower Vf in defects with revision granuloma tissues compared to defects with primary osteoarthritic tissues. Polyethylene granuloma tissues in trabecular bone defects inhibited bone healing. Therefore, debridement around a metal-on-polyethylene hip replacement may shorten the time it takes to achieve secondary stability around a revision hip replacement.

Orthopaedic implant failure: aseptic implant loosening–the contribution and future challenges of mouse models in translational research

Aseptic loosening as a result of wear debris is considered to be the main cause of long-term implant failure in orthopaedic surgery and improved biomaterials for bearing surfaces decreases significantly the release of micrometric wear particles. Increasingly, in-depth knowledge of osteoimmunology highlights the role of nanoparticles and ions released from some of these new bearing couples, opening up a new era in the comprehension of aseptic loosening. Mouse models have been essential in the progress made in the early comprehension of pathophysiology and in testing new therapeutic agents for particle-induced osteolysis. However, despite this encouraging progress, there is still no valid clinical alternative to revision surgery. The present review provides an update of the most commonly used bearing couples, the current concepts regarding particle–cell interactions and the approaches used to study the biology of periprosthetic osteolysis. It also discusses the contribution and future challenges of mouse models for successful translation of the preclinical progress into clinical applications.

Bone and the innate immune system

The immune system and bone are intimately linked with significant physical and functionally related interactions. The innate immune system functions as an immediate response system to initiate protections against local challenges such as pathogens and cellular damage. Bone is a very specific microenvironment, in which infectious attack is less common but repair and regeneration are ongoing and important functions. Thus, in the bone the primary goal of innate immune and bone interactions is to maintain tissue integrity. Innate immune signals are critical for removal of damaged and apoptotic cells and to stimulate normal tissue repair and regeneration. In this review we focus on the innate immune mechanisms that function to regulate bone homeostasis.

Hemiarthroplasty of the shoulder joint using a custom-designed high-density nano-hydroxyapatite/polyamide prosthesis with a polyvinyl alcohol hydrogel humeral head surface in rabbits

In this study, a novel custom-designed high-density nano-hydroxyapatite/polyamide (n-HA/PA) prosthesis with a polyvinyl alcohol (PVA) hydrogel humeral head surface was employed to repair the shoulder joint head for hemiarthroplasty in rabbits. The prosthesis was fabricated using three-dimensional computed tomography and computer-aided design and computer-aided manufacturing systems for perfect fitting. Sixteen New Zealand white rabbits underwent humeral head excision, and received the composite prostheses for hemiarthroplasty. The implant sites were free from suppuration and necrosis at all periods. The X-ray results showed that there was a clear space between the prosthesis head and the glenoid surface, and the joint capsules and surfaces of the glenoid and PVA were well preserved without any damage during the whole inspection period. A high density of bone was observed around the firmware part of the prosthesis. Histological results revealed that significant osteogenesis was surrounding the firmware part, and the joint space was clear and the cartilage of the upper joint surface was basically intact. There was no visible absorption of the joint surfaces even after 3 months of continuous functional motions. The maximum tensile strength between the prosthesis and host bone reached 2.63 MPa at the 12th week postimplantation. In conclusion, the customized prosthesis by combination of PVA and high-density n-HA/PA has excellent biocompatibility and biological fixation, and offers a promising substitute for both the cartilage and the bone of the humeral head in a rabbit model as level V evidence.

Highly crosslinked polyethylene does not reduce the wear in total knee arthroplasty: in vivo study of particles in synovial fluid

The aim was to assess if the reduction in polyethylene wear with highly crosslinked polyethylene suggested by studies with knee simulators is confirmed in patients with a knee arthroplasty. The use of a conventional or a highly crosslinked polyethylene was randomly assigned intraoperatively. Twelve months after surgery a knee arthrocentesis was performed and the synovial fluid of 17 patients in each group was studied analysing the number, size and shape of the polyethylene particles by scanning electron microscope. We found no significant differences in the concentration, size or morphology of polyethylene particles between groups. The great variability in the number of particles between individuals suggests that in vivo polyethylene wear depends on many factors and probably the type of polyethylene is not the most significant.

Polyethylene particles stimulate expression of ITAM-related molecules in peri-implant tissues and when stimulating osteoclastogenesis in vitro

Wear particle-induced orthopaedic prosthesis loosening is associated with elevated osteoclast activity. The immunoreceptor tyrosine-based activation motif (ITAM)-related molecules OSCAR, FcRγ, TREM2 and DAP12 are important for osteoclast formation. The aim of this study was to determine if these molecules are involved in peri-implant loosening by investigating their expression in peri-implant tissues obtained at revision of joint replacement components containing polyethylene (PE) wear particles, and in osteoclasts formed in vitro in the presence of PE particles. The results showed that there was a marked and statistically significant increase in protein levels of the ITAM-related molecules in the revision tissues. The levels of OSCAR, FcRγ, TREM2 and DAP12 mRNA in the revision tissues were also increased. In vitro PE particles stimulated osteoclast resorption in the presence of 50 ng ml(-1) receptor activator NFκB (RANKL) and significantly elevated the expression of OSCAR, FcRγ, TREM2 and DAP12 during osteoclast formation. These findings suggest that the ITAM signalling molecules and their co-receptors have a role in pathogenic bone loss associated with implant PE wear.