Periprosthetic osteolysis and its association with RANKL expression

Extensive osteolysis adjacent to orthopedic implants is often associated with wear particles of prosthetic material. The activation of the RANKL/RANK/OPG system is considered to be a likely cause of periprosthetic osteolysis leading to implant failure. The aim of this study was to examine the possible correlation between the clinical extent of osteolysis, the number of wear particles and expression of the osteoclastic mediator RANKL (receptor activator of nuclear factor kappa B ligand) in the tissues around aseptically loosened cemented and non-cemented total hip replacements. Periprosthetic tissues were harvested from 59 patients undergoing revision of hip replacement for aseptic loosening. We observed RANKL-positive cells in 23 of our 59 patients, their presence was noted predominantly in tissues with a loosened cemented endoprosthesis. We have found that RANKL is present only in tissues with a large amount of wear debris and predominantly in cases involving loosened cemented implants.     

Circadian rhythm and cartilage extracellular matrix genes in osseointegration: a genome-wide screening of implant failure by vitamin D deficiency

Background

Successful dental and orthopedic implants require the establishment of an intimate association with bone tissue; however, the mechanistic explanation of how biological systems accomplish osseointegration is still incomplete. We sought to identify critical gene networks involved in osseointegration by exploring the implant failure model under vitamin D deficiency.

Methodology

Adult male Sprague-Dawley rats were exposed to control or vitamin D-deficient diet prior to the osteotomy surgery in the femur bone and the placement of T-shaped Ti4Al6V implant. Two weeks after the osteotomy and implant placement, tissue formed at the osteotomy site or in the hollow chamber of T-shaped implant was harvested and total RNA was evaluated by whole genome microarray analyses.

Principal Findings

Two-way ANOVA of microarray data identified 103 genes that were significantly (>2 fold) modulated by the implant placement and vitamin D deficiency. Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses assigned the highest z-score to the circadian rhythm pathway including neuronal PAS domain 2 (NPAS2), and period homolog 2 (Per2). NPAS2 and Aryl hydrocarbon receptor nuclear translocator-like (ARNTL/Bmal 1) were upregulated around implant and diminished by vitamin D deficiency, whereas the expression pattern of Per2 was complementary. Hierarchical cluster analysis further revealed that NPAS2 was in a group predominantly composed of cartilage extracellular matrix (ECM) genes. Whereas the expression of bone ECM genes around implant was not significantly affected by vitamin D deficiency, cartilage ECM genes were modulated by the presence of the implant and vitamin D status. In a proof-of-concept in vitro study, the expression of cartilage type II and X collagens was found upregulated when mouse mesenchymal stem cells were cultured on implant disk with 1,25D supplementation.

Conclusions

This study suggests that the circadian rhythm system and cartilage extracellular matrix may be involved in the establishment of osseointegration under vitamin D regulation.     

Similar Outcomes Achieved Between Anterior and Posterior Approach Total Hip Arthroplasty Using Dual Mobility Implants

BackgroundDual mobility (DM) bearings for total hip arthroplasty (THA) have been proposed to reduce the risk of instability in high-risk patients; however, their utility in primary THA remains relatively unexplored. No previous reports have described whether surgical approach influences outcomes associated with DM implant systems. This study aims to compare patient reported outcomes and post-operative groin pain between patients undergoing anterior approach versus posterior approach following primary THA with DM implants.MethodsWe retrospectively reviewed all patients who underwent primary THA and received a DM implant between 2011-2021. Patients were stratified into two cohorts based on surgical approach (anterior vs. posterior approach). Primary outcomes included the presence of substantial postoperative groin pain as well as readmission and revision rates. Demographic differences were assessed using chi-square and independent sample t-tests. Outcomes were compared using multilinear and logistic regressions.ResultsOf the 495 patients identified, 55 (11%) underwent THA via the anterior approach and 440 (89%) via the posterior approach. Surgical time (100.24 vs. 109.42 minutes, p=0.070), length of stay (2.19vs.2.67 days,p=0.072), discharge disposition (p=0.151), and significant postoperative groin pain (1.8%vs.0.7%,p=0.966) did not statistically differ between the cohorts. 90-day readmission (9.1%vs.7.7%,p=0.823) and revision rate (0.0%vs.3.0%,p=0.993) did not significantly differ as well. Specifically, readmission (p=0.993) and revision (p=0.998) for instability did not significantly differ between the cohorts. We found no statistical difference in HOOS, JR (p=0.425), VR-12 PCS (p=0.718), and VR-12 MCS (p=0.257) delta score improvement from preoperative to 1-year follow-up between the two groups.ConclusionComparable outcomes following implantation of DM constructs may be achievable irrespective of the surgical approach employed. The incidence of iliopsoas injections for groin pain did not significantly differ between anterior and posterior approaches. Future investigation is needed to determine whether surgical approach influences long-term outcomes in patients receiving DM implants. Level of Evidence: III     

Metal Ion Concentrations in Body Fluids after Implantation of Hip Replacements with Metal-on-Metal Bearing – Systematic Review of Clinical and Epidemiological Studies

Introduction

The use of metal-on-metal (MoM) total hip arthroplasty (THA) increased in the last decades. A release of metal products (i.e. particles, ions, metallo-organic compounds) in these implants may cause local and/or systemic adverse reactions. Metal ion concentrations in body fluids are surrogate measures of metal exposure.

Objective

To systematically summarize and critically appraise published studies concerning metal ion concentrations after MoM THA.

Methods

Systematic review of clinical trials (RCTs) and epidemiological studies with assessment of metal ion levels (cobalt, chromium, titanium, nickel, molybdenum) in body fluids after implantation of metalliferous hip replacements. Systematic search in PubMed and Embase in January 2012 supplemented by hand search. Standardized abstraction of pre- and postoperative metal ion concentrations stratified by type of bearing (primary explanatory factor), patient characteristics as well as study quality characteristics (secondary explanatory factors).

Results

Overall, 104 studies (11 RCTs, 93 epidemiological studies) totaling 9.957 patients with measurement of metal ions in body fluids were identified and analyzed. Consistently, median metal ion concentrations were persistently elevated after implantation of MoM-bearings in all investigated mediums (whole blood, serum, plasma, erythrocytes, urine) irrespective of patient characteristics and study characteristics. In several studies very high serum cobalt concentrations above 50 µg/L were measured (detection limit typically 0.3 µg/L). Highest metal ion concentrations were observed after treatment with stemmed large-head MoM-implants and hip resurfacing arthroplasty.

Discussion

Due to the risk of local and systemic accumulation of metallic products after treatment with MoM-bearing, risk and benefits should be carefully balanced preoperatively. The authors support a proposed „time out“ for stemmed large-head MoM-THA and recommend a restricted indication for hip resurfacing arthroplasty. Patients with implanted MoM-bearing should receive regular and standardized monitoring of metal ion concentrations. Further research is indicated especially with regard to potential systemic reactions due to accumulation of metal products.     

Patient Reported Outcomes After Conversion vs. Primary Total Hip Arthroplasty: A Propensity Matched Analysis

BackgroundConversion total hip arthroplasty (cTHA) is increasingly utilized as a salvage procedure for complications associated with fracture fixation around the hip and acetabulum and for failed hip preservation surgery. While primary THA (pTHA) has a high success rate, little is known about outcomes following conversion THA. The purpose of this study is to evaluate patient reported outcomes (PROs) and complication rates following conversion THA compared to primary THA.MethodsPatients that underwent cTHA or pTHA from 2015-2020 at a large tertiary referral academic center were retrospectively identified. THA patients were propensity matched in a 1:1 fashion by age, body mass index (BMI), and sex. Pain scores and PROMIS physical function (PF), pain interference (PI), and depression (DA) scores were compared at preoperative and final postoperative follow up timepoints using independent t-tests. Differences in complication and reoperation rates between cohorts were assessed using chi square analysis.ResultsA total of 118 THAs (59 cTHA, 59 pTHA) were included in this analysis with an average follow up of 21.3 months. cTHAs were most commonly performed following hip fracture fixation (50.8%). The conversion cohort had significantly longer lengths of stay (3.6 days vs 1.9 days, p<0.01) and greater use of revision-type implants (39.0% vs 0.0%, p<0.01) compared to pTHA. There was no significant difference in complication rates (cTHA = 15.3%, pTHA = 8.5%; p=0.26), with intraoperative fracture being the most common for both. Primary and conversion THA groups also experienced similar reoperation rates (cTHA = 5.1%, pTHA = 6.8%; p=0.70). No significant differences in PROs at final follow up were identified between groups.ConclusionPatients undergoing cTHA required increased utilization of revision hip implants and had longer lengths of stay, but had comparable complication and reoperation rates, and ultimately demonstrated similar improvements in PROMIS scores compared to a matched cohort of pTHA patients. Level of Evidence: III     

Self-reported diseases and symptoms by rupture status among unselected Danish women with cosmetic silicone breast implants

Epidemiologic evidence does not support an association between silicone breast implants and connective tissue or other rheumatic diseases. However, a recent study has suggested that women with ruptured implants may be at increased risk of developing fibromyalgia. An analysis of adverse health outcomes according to breast implant rupture status was conducted in 238 unselected Danish women with cosmetic silicone breast implants. Ninety-two of the women had definite implant rupture, and 146 had intact implants as determined by magnetic resonance imaging. Before undergoing imaging, the women provided blood samples and completed a self-administered questionnaire. Women with ruptured implants overall, and the subgroup with extracapsular ruptures (n = 23), were compared with women with intact implants regarding a number of self-reported diseases and symptoms and the presence of specific autoantibodies, such as antinuclear antibodies, rheumatoid factor, and cardiolipin immunoglobulin G and M antibodies. Overall, there were no differences in the occurrence of self-reported diseases or symptoms or in the presence of autoantibodies between women with intact implants and women with ruptured implants, including extracapsular rupture. The only exception was capsular contracture, which was reported six times more frequently by women with extracapsular ruptures than by women with intact implants (OR, 6.3; 95 percent CI, 1.7 to 23.5). In conclusion, this study of unselected women with silicone breast implants could establish no association between silicone implant rupture and specific diseases or symptoms related to connective tissue disease or other rheumatic conditions, except for an excess of capsular contracture among women with extracapsular rupture.     

Macrophage migration inhibitory factor: a regulator of MMP13 and inflammation in titanium particles-stimulated air pouch in vivo

Macrophage migration inhibitory factor (MIF) is a significant regulator of inflammatory diseases, and local inflammation plays an important role in the aseptic loosening of failed total hip arthroplasty (THA). A high-level MIF expression was found in the interfacial membrane around implants. However, the cause of increased MIF expression and the action of MIF in the process of aseptic-loosening implant is still unknown. This study is to investigate MIF expression and its upregulating effect on matrix metalloproteinases (MMPs) expression in the particles-stimulated air pouches in mice that appear to closely resemble the interfacial membranes. A total of 48 murine air pouches were divided into four groups, and were injected with PBS, titanium particles suspensions, titanium particles suspensions with neutralizing antibody of MIF, and titanium particles suspensions with normal IgG, respectively. Histological and cytokine responses were evaluated. The inflammatory reaction of air pouch membranes induced by titanium particles was significantly suppressed by neutralizing antibody. The levels of MIF protein and mRNA were significantly increased in the titanium particles-stimulated air pouch membranes compared with the control groups. So were the levels of MMP13 protein and mRNA. However, the levels of MMP13 protein and mRNA were significantly reduced by neutralizing antibody. Our study demonstrates that titanium particles can cause the air pouch membranes to increase the expression of MIF, which upregulates the production of MMP13 and induces inflammatory reaction in vivo. The results indicate that MIF may play an important role in the process of aseptic-loosening implants after THA.     

Population-based rates of revision of primary total hip arthroplasty: a systematic review

Background

Most research on failure leading to revision total hip arthroplasty (THA) is reported from single centers. We searched PubMed between January 2000 and August 2010 to identify population- or community-based studies evaluating ten-year revision risks. We report ten-year revision risk using the Kaplan-Meier method, stratifying by age and fixation technique.

Results

Thirteen papers met the inclusion criteria. Cemented prostheses had Kaplan-Meier estimates of revision-free implant survival of ten years ranging from 88% to 95%; uncemented prostheses had Kaplan-Meier estimates from 80% to 85%. Estimates ranged from 72% to 86% in patients less than 60 years old and from 90 to 96% in older patients.

Conclusion

Data reported from national registries suggest revision risks of 5 to 20% ten years following primary THA. Revision risks are lower in older THA recipients. Uncemented implants may have higher ten-year rates of revision, regardless of age.     

Topological optimization in hip prosthesis design

With particular interest on total hip arthroplasty (THA), optimization of orthopedic prostheses is employed in this work to minimize the probability of implant failure or maximize prosthesis reliability. This goal is often identified with the reduction of stress concentrations at the interface between bone and these devices. However, aseptic loosening of the implant is mainly influenced by bone resorption phenomena revealed in some regions of the femur when a prosthesis is introduced. As a consequence, bone resorption appears due to stress shielding, that is to say the decrease of the stress level in the implanted femur caused by the significant load carrying of the prosthesis due to its higher stiffness. A maximum stiffness topological optimization-based (TO) strategy is utilized for non-linear static finite element (FE) analyses of the femur–implant assembly, with the goal of reducing stress shielding in the femur and to furnish guidelines for re-designing hip prostheses. This is accomplished by employing an extreme accuracy for both the three-dimensional reconstruction of the femur geometry and the material properties maps assigned as explicit functions of the local densities.     

Prevalence of Failure due to Adverse Reaction to Metal Debris in Modern,Medium and Large Diameter Metal-on-Metal Hip Replacements – The Effect of Novel Screening Methods: Systematic Review and Metaregression Analysis

Metal-on-metal (MoM) hip replacements were used for almost a decade before adverse reactions to metal debris (ARMD) were found to be a true clinical problem. Currently, there is a paucity of evidence regarding the usefulness of systematic screening for ARMD. We implemented a systematic review and meta-analysis to establish the prevalence of revision confirmed ARMD stratified by the use of different screening protocols in patients with MoM hip replacements. Five levels of screening were identified: no screening (level 0), targeted blood metal ion measurement and/or cross-sectional imaging (level 1), metal ion measurement without imaging (level 2), metal ion measurement with targeted imaging (level 3) and comprehensive screening (both metal ions and imaging for all; level 4). 122 studies meeting our eligibility criteria were included in analysis. These studies included 144 study arms: 100 study arms with hip resurfacings, 33 study arms with large-diameter MoM total hip replacements (THR), and 11 study arms with medium-diameter MoM THRs. For hip resurfacing, the lowest prevalence of ARMD was seen with level 0 screening (pooled prevalence 0.13%) and the highest with level 4 screening (pooled prevalace 9.49%). Pooled prevalence of ARMD with level 0 screening was 0.29% and with level 4 screening 21.3% in the large-diameter MoM THR group. In metaregression analysis of hip resurfacings, level 4 screening was superior with regard to prevalence of ARMD when compared with other levels. In the large diameter THR group level 4 screening was superior to screening 0,2 and 3. These outcomes were irrespective of follow-up time or study publication year. With hip resurfacings, routine cross-sectional imaging regardless of clinical findings is advisable. It is clear, however, that targeted metal ion measurement and/or imaging is not sufficient in the screening for ARMD in any implant concepts. However, economic aspects should be weighed when choosing the preferred screening level.     

Characteristic Expression of Extracellular Matrix in Subcutaneous Adipose Tissue Development and Adipogenesis; Comparison with Visceral Adipose Tissue

Adipose tissue is a connective tissue specified for energy metabolism and endocrines, but functional differences between subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) have not been fully elucidated. To reveal the physiological role of SAT, we characterized in vivo tissue development and in vitro adipocyte differentiation. In a DNA microarray analysis of SAT and VAT in Wistar rats, functional annotation clusters of extracellular matrix (ECM)-related genes were found in SAT, and major ECM molecules expressed in adipose tissues were profiled. In a histological analysis and quantitative expression analysis, ECM expression patterns could be classified into two types: (i) a histogenesis-correlated type such as type IV and XV collagen, and laminin subunits, (ii) a high-SAT expression type such as type I, III, and V collagen and minor characteristic collagens. Type (i) was related to basal membrane and up-regulated in differentiated 3T3-L1 cells and in histogenesis at depot-specific timings. In contrast, type (ii) was related to fibrous forming and highly expressed in 3T3-L1 preadipocytes. Exceptionally, fibronectin was abundant in developed adipose tissue, although it was highly expressed in 3T3-L1 preadipocytes. The present study showed that adipose tissues site-specifically regulate molecular type and timing of ECM expression, and suggests that these characteristic ECM molecules provide a critical microenvironment, which may affect bioactivity of adipocyte itself and interacts with other tissues. It must be important to consider the depot-specific property for the treatment of obesity-related disorders, dermal dysfunction and for the tissue regeneration.     

Characterization of implants from Dupuytren's contracture tissue into the nude (athymic) mouse

Dupuytren's contracture tissues were obtained from six patients as excess surgical material. Pieces of these tissues (a total of 38 implants) were placed into subcutaneous pockets in the suprascapular area of nude (athymic) mice. The objective was to determine whether the implant tissues would be maintained in the mouse with the characteristics of Dupuytren's tissue. The implants were removed for study at 14-179 days after implantation. Microvascular anastomosis between implant and host skin was established within the first 14 days. Histologic character and electron microscopic structure of the implants did not change during the course of the study. The implants became reduced in size with time. However, neither the spatial pattern of collagen nor the appearance of fibroblast cells changed. The original high levels of chondroitin-4-sulfate were significantly decreased in the 66- to 179-day postimplantation group, but were not significantly different from the values for normal fascial bands. The hyaluronic acid of the implants increased significantly with time of implantation, but never reached the level found in the normal fascial bands. The use of implants into nude mice may be useful for further experimental studies of Dupuytren's contracture.     

Differences in Infection Rates by Surgical Approach in Total Hip Arthroplasty and Patient Sex: A Systematic Review

BackgroundThere exists conflicting data that patient sex may influence complication and revision rates when undergoing total hip arthroplasty (THA), specifically when comparing different surgical approaches. Differences in body fat or muscular distribution are proposed mechanisms, but these are poorly understood and not well described in current literature.MethodsA systematic review of the literature was conducted from PubMed, Embase, and Web of Science from inception of the database through September 15, 2020. Studies were included if they included patients undergoing primary elective unilateral THA, delineated infections by surgical approach, and delineated infections by patient sex. Basic science, cadaveric, and animal studies were excluded as were case reports. Two authors screened abstracts and then extracted data from the full text article.ResultsThree studies, including 1,694 patients undergoing 1,811 THA were included. 80 infections were included. No study reported a statistically significant difference in infection risk by patient sex or surgical approach, though there was substantial heterogeneity in study design, approach, and analysis.ConclusionLimited data suggests no relationship between sexes across surgical approaches for infection rates. However, poor reporting and small sample sizes preclude definitive conclusions from being drawn. Future studies should emphasize reporting differences in outcomes by patient sex to better elucidate differences, if any, in adverse outcomes between sexes following THA across surgical approaches. Level of Evidence: IV     

In-vivo 6 degrees-of-freedom kinematics of metal-on-polyethylene total hip arthroplasty during gait

Knowledge of accurate in-vivo 6 degree-of-freedom (6-DOF) kinematics of total hip arthroplasty (THA) during daily activities is critical for improvement of longevity of the components. Previous studies assessed in-vivo THA kinematics using skin marker-based motion analysis. However, skin markers are prone to move with respect to the underlying bones. A non-invasive dual fluoroscopic imaging system (DFIS) based tracking technique has been used to avoid skin artifacts and provide accurate 6-DOF kinematic measurement. This study aimed to quantify in-vivo 6-DOF THA kinematics during gait using DFIS. Twenty eight well-functioning THAs were evaluated during treadmill gait under DFIS surveillance. The maximum translations of the femoral head were 0.46±0.10 mm and 0.45±0.10 mm during the stance and swing phases (p=0.57), respectively. The range of hip flexion was from 8.7° to 47.6°, adduction from 3.0° to 12.5° and external rotation from 19.2° to 29.7°. The THA was flexed, externally rotated and adducted throughout the gait. The magnitudes of the femoral head translations were found to be within the manufacture tolerance of the components, suggesting that in-vivo hip “pistoning” during gait cycle may be minimal in well-functioning THAs. The 6-DOF kinematics could be used as the baseline knowledge for further improvement of wear-testing of hip implant, implants manufacturing and implant positioning during surgery.     

Local oestrogen therapy modulates extracellular matrix and immune response in the vaginal tissue of post‐menopausal women with severe pelvic organ prolapse

This study investigates the effect of local oestrogen therapy (LET) on the expression of proteins participating in collagen/elastin biogenesis and immune markers in vaginal tissues of post‐menopausal women with severe pelvic organ prolapse (POP). Vaginal biopsies were collected from the anterior vaginal wall of informed and consented 52 post‐menopausal women with severe POP undergoing total hysterectomy. Twenty‐nine of the 52 women were treated with LET (in the form of vaginal oestrogen cream or tablet), while the remaining 23 untreated patients served as the controls. This study was approved by Sinai Health System REB. Vaginal tissue specimens were analysed for gene and protein expression using real‐time RT‐PCR and Luminex assays, protein localization and immune cell infiltration were assessed by immunohistochemistry. Forty‐four cytokines were detected. We found that LET application: (a) significantly increased (P < 0.05) gene and protein expression levels of extracellular matrix (ECM) structural proteins, collagen and elastin, as well as the expression of ECM maturation enzyme BMP1; (b) decreased protein expression level of ECM degradation enzymes MMP1, MMP2 and MMP3 accompanied by an increase in their tissue inhibitors, TIMP1 and TIMP4; (c) significantly increased (P < 0.05) the gene and protein expression levels of 14 vaginal cytokines involved in leucocyte infiltration, which was confirmed by immunohistochemistry. Our results indicate that LET plays an important role in the activation of immune system within the local vaginal environment, limiting the undesirable ECM degradation, which supports the strengthening of vaginal ECM in post‐menopausal women, therefore resisting menopause/age‐related changes and inducing urogenital tract tissue regeneration.     

Blood and plasma titanium levels associated with well-functioning hip implants

BackgroundHip implants are usually manufactured from cobalt-chromium and titanium alloys. As the implants wear and corrode, metal debris is released into the surrounding tissue and blood, providing a potential biomarker for their function. Whilst there are laboratory reference levels for blood cobalt and chromium in patients with well and poorly functioning hip implants, there are no such guidelines for titanium. This is despite the increasing use of titanium implants worldwide.Patients and methodsWe recruited a consecutive series of 95 patients (mean age 71 years, mean time after surgery 8.5 years) with one hip implant type, inserted by the same surgeon. We assessed clinical and radiological outcome, and measured blood and plasma titanium using high resolution inductively-coupled plasma mass spectrometry.ResultsThe upper normal reference limit for blood and plasma titanium was 2.20 and 2.56 μg L⁻¹, respectively, and did not differ significantly between males and females.ConclusionWe are the first to propose a laboratory reference level for blood and plasma titanium in patients with well-functioning titanium hip implants. This is an essential starting point for further studies to explore the clinical usefulness of blood titanium as a biomarker of orthopaedic implant performance, and comes at a time of considerable controversy regarding the use of certain titanium alloys in hip arthroplasty.     

Serum kinetics of soluble triggering receptor expressed on myeloid cells-1 differs in relation to the type of arthroplasty

Context: Soluble triggering receptor expressed on myeloid cells-1 (sTREM-1) participates in the inflammatory process.

Purpose: To describe changes of sTREM-1 in the serum after hemiarthroplasty (HA) and total hip arthroplasty (THA).

Methods: Serial blood samples were drawn from 122 patients with hip fracture. Interleukin-6 (IL-6), sTREM-1, and C-reactive protein (CRP) were measured.

Results: IL-6 and CRP were similarly increased after both HA and THA. sTREM-1 was increased early in HA and late after THA. The only parameter that was higher among patients who developed systemic inflammatory response syndrome was IL-6.

Conclusions: Kinetics of sTREM-1 differs among patients undergoing HA of the hip and those undergoing THA.     

Examination of granuloma of revised cemented or cementless total hip arthroplasties using inductively coupled plasma atomic emission spectrometry (ICP-OES)]

INTRODUCTION: Aseptic loosening is the most common problem in total hip arthroplasty (THA). One main aspect is inflammatory reaction against wear particles of the prosthesis materials. Analysing failure mechanisms in THA analysis of the particles and their element distribution of revised granulomatous tissue is essential to improve materials used in THA. MATERIALS AND METHODS: 23 granulomas of revised THA due to aseptic loosening, 13 of which with metal on metal bearing (M/M), were analysed using inductively coupled plasma atomic emission spectrometry (ICP-OES). RESULTS: Elements Cr, Mn, Ni, Al, Cu, Zn, Cd, Ti, V, Zr, Nb and Fe could be detected. The maximum value of Cr was 23.88 ppb (parts per billion), Al 191.02 ppb, Ni 64.95 ppb and Zr 9.96 ppb. The highest value of Al could be found in cementless implants. The maximum value of the elements Cr and Ni could be detected in M/M. In cemented implants the highest value of Zr was found. DISCUSSION: The origin of Zr was the used bone cement in cemented THA. The elements Cr and Ni were significantly higher in M/M bearings. The highest value of Al was detected in granulomas of revised corund rough blasted cementless implants. The histopathologic findings of the revised M/M bearings have been published recently. Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-OES) could not show any differences of the alloying constituents in cases with or without allergic reactions. ICP-OES analysis seems to be not useful examination of histologic sections using SEM with cryotransfer unit.     

Frictional heating of total hip implants. Part 1: measurements in patients

Hip implants heat up due to friction during long lasting, high loading activities like walking. Thermal damage in the surrounding soft and hard tissues and deteriorated lubrication of synovial fluid could contribute to implant loosening. The goal of this study was to determine the implant temperatures in vivo under varying conditions. Temperatures and contact forces in the joints were measured in seven joints of five patients using instrumented prostheses with alumina ceramic heads and telemetry data transmission. The peak temperature in implants with polyethylene cups rose up to 43.1 degrees C after an hour of walking but varied considerably individually. Even higher temperatures at the joints are probable for patients with higher body weight or while jogging. The peak temperature was lower with a ceramic cup, showing the influence of friction in the joint. During cycling the peak temperatures were lower than during walking, proving the effect of force magnitudes on the produced heat. However, no positive correlation was found between force magnitude and maximum temperature during walking. Other individual parameters than just the joint force influence the implant temperatures. Based on the obtained data and the available literature about thermal damage of biological tissues a detrimental effect of friction induced heat on the stability of hip implants cannot be excluded. Because the potential risk for an individual patient cannot be foreseen, the use and improvement of low friction implant materials is important.