Introduction. Aseptic loosening is a major cause of revision of total joint arthroplasty (TJA). Although crosslinked Ultra-high molecular weight polyethylene (UHMWPE) have improved wear resistance, residual radicals remaining in the material have a possibility to increase bio-reactivity of particles [2]. In this study, we attempt to evaluate the effects of irradiation and residual radicals on bio-reactivity of the material with a new method called the inverse culture method [1]. Material and methods. UHMWPE particles (10µm diameter in average, Mitsui chemicals Co., LTD) along with irradiated particles (RAD, 300kGy electron irradiation) and particles annealed after the irradiation (RAD+ANN, 100°C 72 hours) are co-incubated with mouse macrophage cell line RAW264 using the inverse culture method. The amount of TNF-α was measured with ELISA. Results and discussion. The amount of TNF-α released by macrophages reacting with virgin UHMWPE, RAD and RAD+ANN is shown in Figure 1. The horizontal axis represents the total surface area of the particles. The coefficient of determination and inclination of the approximate curve are calculated to analyze the result. The coefficient of determination suggested that cytokines released from macrophage is dose-dependent to the surface area of polyethylene particles, which was consistent with the result of our former study[1]. We use the inclination of the approximation curve in Figure 1 as an index to evaluate the bio-reactivity. The values of the index of virgin, RAD and RAD+ANN were 21×10. -4. gLm. -2. , 100×10. -4. gLm. -2. and 59×10. -4. gLm. -2. The inclination of the approximation line of RAD is significantly larger than that of virgin (test for the difference of regression line angle). These suggest that the irradiation to UHMWPE particles increases their bio-reactivity possibly due to radicals. The increased reactivity cannot be eliminated by annealing (100°C 72 hours) completely. Conclusion. Although electron irradiation increases the bio-reactivity of UHMWPE particles, annealing after the irradiation can decrease it, but cannot restore to original reactivity. For any figures or tables, please contact authors directly

Nanometre-sized particles of ultra-high molecular weight polyethylene have been identified in the lubricants retrieved from hip simulators. Tissue samples were taken from seven failed Charnley total hip replacements, digested using strong alkali and analysed using high-resolution field emission gun-scanning electron microscopy to determine whether nanometre-sized particles of polyethylene debris were generated in vivo. A randomised method of analysis was used to quantify and characterise all the polyethylene particles isolated. We isolated nanometre-sized particles from the retrieved tissue samples. The smallest identified was 30 nm and the majority were in the 0.1 μm to 0.99 μm size range. Particles in the 1.0 μm to 9.99 μm size range represented the highest proportion of the wear volume of the tissue samples, with 35% to 98% of the total wear volume comprised of particles of this size. The number of nanometre-sized particles isolated from the tissues accounted for only a small proportion of the total wear volume. Further work is required to assess the biological response to nanometre-sized polyethylene particles

Introduction. Ultra-high molecular weight polyethylene (UHMWPE) tape, which comprised threads of UHMWPE fibers with the thickness less than 0.5 mm, was developed as a flexible fixation device. We describe new techniques using UHMWPE tape for the reattachment of the osteotomised fragment and the repair of intraoperative calcar fractures in total hip arthroplasty (THA). Patients & Methods. We reviewed the medical records and radiographs of the studied subjects after approval of this study by the institutional review board committee. Experiment 1: Between October 2011 and May 2012, 60 consecutive primary THAs were performed with the mini-trochanteric approach, which involved reattaching the osteotomised fragment using UHMWPE tape (Nesplon; Alfresa Pharma, Osaka, Japan). [Fig.1] By splitting the anterior one-fourth of the gluteus medius, the minitrochanteric osteotomy, a half-ellipsoid body about 15 mm long, 10 mm wide, and 5 mm deep, is performed using a curved chisel. After implanting of the prosthesis, the osteotomised fragment is reattached by using two 3-mm wide Nesplon tapes. Using 2.4 mm Kirshner wire, two sets of drill holes are created below the trochanteric bed of the femur. Nesplon tapes are passed through each drill hole and penetrated over the trochanteric fragment. Nesplon tape is tied using a double-loop sliding knot in conjunction with a special tightening gun tensioner up to 20 kgf. [Fig.2] The radiographic results were retrospectively analyzed to determine the incidence of nonunion and complications related to trochanteric site. Hip functional results were rated according to the Japanese Orthopedic Association (JOA) hip score. Experiment 2: Between July 2011 and May 2012, 5-mm wide Nesplon tapes were used for restoration of intraoperative femoral fractures in 4 primary THAs. For the repair of intraoperative proximal femoral fractures, 5-mm wide Nesplon tape is tightened with cerclage wiring technique using the gun tensioner up to 30 kgf. [Fig.3] The postoperative radiographic changes were analyzed. Results. Experiment 1: Nonunions occurred in no (0%) patient. Bone union with minimally displaced was present in three (5.0%) patients. The mean JOA scores improved 47.1 to 84.6 at 1 year postoperatively. Experiment 2: There were no migrations of the femoral prosthesis in the postoperative period. Discussion. These techniques using UHMWPE tapes are simple and more advantageous to prevent the complications resulting from metal wires. UHMWPE tape, which has flat configuration with high flexibility, can provide a greater contact area avoiding the risk of bone cutout. Using a special tightening gun can easy reattachment with precise tension even in the setting of poor bone quality

INTRODUCTION. Ultra-High Molecular Weight Polyethylene (UHMWPE) wear debris is thought to be a main factor in the development of osteolysis (1). However, the method for the evaluation of the biological response to UHMWPE particles has not yet been standardized. In this study, four different types of UHMWPE particles were generated using a mechanized pulverizing method and the biological responses of macrophages to the particles were investigated using an inverted cell culturing process (2). MATERIALS & METHODS. Virgin samples were manufactured via Direct Compression Molding (DCM) technique from UHMWPE GUR1050 resin powder (Ticona, USA). For vitamin E (VE)-blended sample, the resin was mixed with VE at 0.3 wt% and the mixture was then molded using DCM. The crosslinked virgin samples were made by gamma ray irradiation to UHMWPE GUR1020 resin sheet (Meditech, USA) with doses of 95kGy ±10% and annealed. The VE-blended crosslinked samples were made by electron beam irradiation to VE-blended samples with doses of 300kGy and annealed. The material conditions were summarized in Figure 1. To pulverize the samples, the Multi-Beads Shocker (Yasui Kikai, Japan) was used. After pulverization, samples were dispersed in an ethanol solution and sequentially filtered through polycarbonate filters. Over 100 sections of the filter were selected randomly and images of the particles were analyzed using scanning electron microscope (SEM). To analyze the macrophage biological response, an inverted cell culturing process was used (2). The mouse macrophage-like cells were seeded at densities of 4×105cells per well in a 96-well culture plate and incubated for 1h. UHMWPE particles suspended in the culture medium were then added to each well in the appropriate amount. After that, fresh medium was added to fill the wells, and a sealing film was used to cover the culture plate. The culture plate was then inverted to cause the UHMWPE particles interact with the adhered macrophages. The inverted culture plate was incubated for 8h. The amount of TNF-α was measured by enzyme-linked immunosorbent assay (ELISA). RESULTS & DISCUSSION. Geometric measurements showed no significant difference in the UHMWPE particles (Figure 2). The amount of TNF-α released stimulated by the crosslinked virgin particles showed significantly higher relative to the other UHMWPE particles (Figure 3). During crosslinking irradiation, the carbon free radicals are generated in the main chain (3). In the presence of oxygen, these radicals can react to form peroxy radicals and when the peroxy free radicals react with hydrogen they form hydroperoxides, which can further degrade into other oxidation products (4). It has been reported that VE hinders this cascading in UHMWPE (5). Therefore, it is possible that oxidation of the crosslinked virgin UHMWPE was involved in the cytokine response observed in this study. However resin material, molding technique and the irradiation method were different between crosslinked virgin and VE-blended crosslinked samples. Further consideration will be needed to examine the relationship between residual radicals, hydroperoxides and biological response

The mechanical failure of ultra-high molecular weight polyethylene (UHMWPE) acetabular cups in vivo is due mainly to a combination of excessive plastic flow and fretting. Localised overheating of the bearing surface, due to insufficient lubrication, causes this. The purpose of this study was to determine the amount of creep in UHMWPE under various conditions. Test pieces were cut from a piece of raw material and tested according to ASTM D2990. In the first test, to determine the anisotropic behaviour of the material, test pieces of raw material were cut at various orientations. The material was then tested in the virgin state and the virgin state at different temperatures. It was also gamma sterilised under different conditions, namely 24 kGy in air, 25 kGy in a nitrogen atmosphere and 25 kGy in air, and heat treated at 80°C to get an annealing effect. Further tests were conducted to determine the effect of cross-linking on creep behaviour. These tests were administered at room temperature, at 50°C and at 60°C. The material showed extreme anisotropic behaviour. It was more sensitive to creep in the centre of the bar than on the outside (32%). Maximum creep, however, occurred at a 45°-angle. This is significant if we assume that maximum loading of an acetabular cup occurs at an angle of 70.7°. The difference in creep for the virgin material, measured at room temperature and at 60°C, was 87.3% or 0.716 mm. The variance in creep for the different methods of sterilisation was a maximum of 0.3 mm. Creep for the cross-linked material, however, was markedly less than for the virgin material. There was a decrease of 36% (0.58 mm) in creep at room temperature and almost 83% (0.84 mm) at 60°C. The test results show that the cross-linked material is much more stable. This may explain the good in-vivo service of these products

Between January 1990 and October 2000, 108 total hip arthroplasties using a cemented polished titanium stem and a cemented ultra-high molecular weight polyethylene (UHMWP) cup were performed at our hospital. Because during routine follow-up visits we noted instances of resorption of the calcar, we decided to assess whether this was a problem. We were able to assess 85 of the original 108 hips. Calcar resorption was observed in 43 hips. The extent of calcar resorption varied from 1 mm to over 15 mm. In one patient a biopsy showed typical polyethylene granuloma. Because there is a risk of long-term failure, we concluded that it is inadvisable to use a cemented polished titanium stem when UHMWP is one of the bearing surfaces

Since artificial joints are expected to operate for more than decades in human body, animal and clinical studies are not suitable for evaluation of their durability. Instead, in-vitro mechanical tests have been employed, but they cannot fully reproduce complex in-vivo mechanical and biochemical environment. For instance, lipids in synovial fluid have been known to be absorbed in ultra-high molecular weight polyethylene (UHMWPE) components of artificial joints in vivo, and recently it was found that absorbed lipids have potential to degrade UHMWPE. In order to assure clinical relevance of the in-vitro mechanical tests, understanding of the effect of the in-vivo environment on mechanical properties is indispensable. However, well-developed mechanical tests cannot be applied to retrieved components, because they require large specimens. In this study, we attempted to develop methods to evaluate mechanical properties of retrieved UHMWPE components. We prepared five kinds of UHMWPE. Those are molded UHMWPE made from GUR 1020 resin without any further treatment, remelted highly crosslinked UHMWPE, annealed highly crosslinked UHMWPE, squalene absorbed UHMWPE which was prepared by immersing in squalene at 80°C for 7 days (SQ) and squalene absorbed and artificially aged UHMWPE which was prepared by artificially aging SQ at 80°C for 21 days in air (SQA). SQ and SQA were employed in this study to mimic lipid absorption and lipid induced degradation. These materials were tested by two well-established mechanical tests, namely, tensile tests and compression tests, and two proposed mechanical tests that can be applied to retrieved components, namely, tensile punch tests and micro indentation tests. It was possible to clearly identify the difference between materials by any of test methods used in this study. Stiffness obtained from tensile punch tests and elastic modulus obtained from micro indentation tests were shown to be highly correlated with elastic modulus obtained from compression tests except for SQA, which was inhomogeneous due to degradation at the surfaces. The results showed that the elastic modulus of the local surface could be evaluated by micro indentation tests, while the average of that of the entire specimen could be evaluated by compression tests. ield load, fracture load and maximum load obtained from tensile punch tests showed little correlation with yield stress, fracture stress and maximum stress obtained from tensile tests, respectively. These differences were considered to be attributed to the differences in a stress condition between these two test methods. It is multi-axial tension in tensile punch tests, while it is uniaxial in tensile tests. Although some of the parameters obtained by tensile punch tests showed no or limited correlation with those obtained by tensile tests, it was possible to clearly identify the difference between materials by these proposed test methods. In particular, micro indentation tests could evaluate the mechanical properties very locally. These proposed test methods have the potential to provide useful information on mechanical properties of retrieved UHMWPE components

Radiation crosslinking decreases the wear of ultra-high molecular weight polyethylene (UHMWPE) and subsequent heating increases its oxidative stability. Clinical trials are showing lower femoral head penetration rate with highly crosslinked vs. conventional UHMWPE liners. Recently, a follow-up report showed a surprising increase in the femoral head penetration rate with a highly crosslinked UHMWPE, prompting us to closely analyze surgically explanted highly crosslinked UHMWPEs. Thirty-four highly crosslinked components, all irradiated (100kGy) and melted, were included in the study. The components were surgically removed from patients for non-polyethylene related reasons. Oxidation was determined at the rim immediately after explantation. After shelf storage in air for 5–77 months, oxidation and crosslink density were measured at the rim and articular surfaces. An additional retrieval (92 mos. in vivo) was tested on the hip simulator; oxidation and crosslink density were determined after simulator testing. All components showed no detectable oxidation immediately after explantation; however, surprisingly oxidation levels increased during shelf storage. Areas with increased oxidation showed a decrease in crosslink density. These changes did not correlate with in vivo duration; however, they correlated strongly with ex vivo duration. The component subjected to hip simulator testing showed no measurable wear and showed no detectable oxidation or marked decrease in crosslink density. Two mechanisms may have reduced the oxidation resistance of highly crosslinked UHMWPE upon exposure to in vivo elements and subsequent exposure to air. One mechanism is based on free radical formation during cyclic loading; the other is based on an oxidation cascade initiated by absorbed lipids. Further studies are necessary to determine the impact of these mechanisms, if any, on the stability of components during in vivo service

Introduction

About 2% of primary total joint replacement arthroplasty (TJA) procedures become infected. Periprosthetic joint infection (PJI) is currently one of the main reasons requiring costly TJA revisions, posing a burden on patients, physicians and insurance companies.¹ Currently used drug-eluting polymers such as bone cements offer limited drug release profiles, sometimes unable to completely clear out bacterial microorganisms within the joint space. For this study we determined the safety and efficacy of an antibiotic-eluting UHMWPE articular surface that delivered local antibiotics at optimal concentrations to treat PJI in a rabbit model.

Alpha Lipoic Acid (L.A.) is an effective natural antioxidant discovered in the human body in 1951 from L.J. Reed and I.C. Gunslaus from liver.

It is inside broccoli, spinach and red meats, especially liver and spleen.

Actually it is largely used as antioxidant in antiaging products according to the low toxicity level of the product.

The present study take into consideration the possibility to reduce oxidation of medical irradiated UHMWPE GUR 1050, mixing together polyethylene powder and Alpha Lipoic Acid powder.

The study is composed of two parts.

Part 1 Thermostability of alpha lipoic acid during polyethylene fusion Part 2 detection of oxygen level in artificially aged irradiated polyethylene

Solid pieces were made with Gur 1050 powder (Ticona Inc., Bayport, Tex, USA) and mixed with Alpha Lipoic Acid (Talamonti, Italy, Stock 1050919074) 0,1%-­‐0,3%-­‐0,5%-­‐1%-­‐2% and gamma ray irradiated with 30 kGy (Isomedix, Northborough, MA).

An owen (80° Celsius) was used to produce an aging effect for 35 days in the doped and control samples (Conventional not doped polyethylene). This process simulate an aging effect of 10 years into the human body.

Part 1 : THERMAL STABILITY : a Fourier Transfer Infra Red (FTIR) test was made in pieces molded in a cell at 150° and 200°Celsius and pressure of 200 MPa comparing to the UHMWPE powder mixed with alpha lipoic acid. The presence of Alpha Lipoic Acid in the polyethylene was found at any depth in the manufacts.

Part 2 : OXIDATION OF THE SURFACE : After 5 weeks at 80° Celsius in a owen (ASTM standard F-­‐2003-­‐02)A FOURIER TRANSFER INFRA RED TEST (FTIR) was made in the superficial layer and deeper on the undersurface of doped 0,1% and conventional UHMWPE.

The antioxidation limit is defined as the ratio of the area under 1740cm/−­‐1 carbonyl and 1370 cm/−­‐1 Methylene absorbance peaks.

In conventional UHMWPE oxidation is detected on the surface and decreases in the deeper layers down to zero under 1500 Micron.

In the doped UHMWPE, FTIR demonstrate a very low oxidation limit on the surface and at any depth, comparing to conventional UHMWPE.

The examples show that Lipoic Acid is effective as antioxidant in irradiated UHMWPE and it is stable with respect to thermal treatment.

For any figures or tables, please contact authors directly.

Introduction

Osteolysis caused by wear of the ultrahigh molecular weight polyethylene (UHMWPE) often leads to failure. Cross-linking improves wear, but also produces residual free radicals that decrease oxidative stability. In vitro studies have shown that the anti-oxidative properties of vitamin E UHMWPE stabilize free radicals while retaining the physical and chemical properties of UHMWPE. The porous surface of the Regenerex™ shell was developed for improved bone in-growth fixation. The increased porosity of the Regenerex™ shell promotes early bony in-growth with the goal of greater long-term stability. The purpose of this study was to evaluate vitamin E infused polyethylene (VEPE) wear and stability of acetabular and femoral components using RSA.

Introduction: Highly cross-linked polyethylene acetabular cups and Oxinium femoral heads were developed to reduce wear debris induced osteolysis. Laboratory tests have shown less wear with these new materials. This RSA-study was performed to compare these new materials in vivo with conventional bearing materials used in total hip arthroplasty. Methods:150 patients were randomized to 5 groups. The patients received either a cemented Charnley mono-block stainless steel femoral stem with a 22.2 mm head or a cemented Spectron EF femoral stem with a 28 mm head. The Charnley stem articulated with a cemented Charnley Ogee acetabular cup. The Spectron EF stem was used with either cemented Reflection All-Poly EtO-sterilized ultra-high molecular weight polyethylene (UHMWPE) acetabular cups or cemented Reflection highly cross-linked polyethylene (XLPE) acetabular cups, combined with either Cobalt Chrome or Oxinium 28 mm femoral heads. Patients were followed up with repeated radiostereometric analysis (RSA) for two years to assess the rate of penetration of the femoral head into the cup (MTPM). Results: At 2 years follow-up the mean MTPM (95 % CI) for Charnley Ogee (n=25) was 0.20 mm (0.11–0.29). For the Spectron EF femoral stem used with Reflection All-Poly UHMWPE acetabular cups the mean MTPM (CI) at 2 years was 0.40 mm (0.23–0.57) when combined with Cobalt Chrome femoral head (n=23) and 0.50 mm (0.29–0.71) when combined with Oxinium femoral head (n=16). When using the Spectron EF femoral stem with Reflection XLPE combined with Cobalt Chrome (n=27) or Oxinium (n=24) femoral head the mean MTPM (CI) at 2 years was 0.19 mm (0.10–0.28) and 0.18 mm (0.07–0.29), respectively. There were no differences in penetration between the Charnley/Ogee, XLPE/CoCr and XLPE/Oxinium groups (student t-test, p=0.5–0.8). There was no statistically significant difference between the two Reflection All-Poly UHMWPE groups (p=0.09). The groups with Reflection All-Poly cups had a statistically significant higher penetration than the three groups mentioned above (p< 0.001). Discussion: The use of Reflection XLPE cups instead of Reflection All-Poly cups reduced femoral head penetration at 2 years. We used the Charnley Ogee cup as a reference due to a long clinical record. This cup was superior to Reflection All-Poly, but not Reflection XLPE, regarding femoral head penetration. Because the femoral head of Charnley Ogee is smaller than the Oxinium/Cobalt Chrome head it might be more clinical relevant to measure volumetric wear. The groups with Oxinium heads did not have less wear than the groups with Cobalt Chrome heads after 2 years follow-up. Further follow-up is needed to evaluate the benefits, if any, of Oxinium femoral heads in the clinical setting

Aims. This study reports the ten-year wear rates, incidence of osteolysis, clinical outcomes, and complications of a multicentre randomized controlled trial comparing oxidized zirconium (OxZr) versus cobalt-chrome (CoCr) femoral heads with ultra-high molecular weight polyethylene (UHMWPE) and highly cross-linked polyethylene (XLPE) liners in total hip arthroplasty (THA). Methods. Patients undergoing primary THA were recruited from four institutions and prospectively allocated to the following treatment groups: Group A, CoCr femoral head with XLPE liner; Group B, OxZr femoral head with XLPE liner; and Group C, OxZr femoral head with UHMWPE liner. All study patients and assessors recording outcomes were blinded to the treatment groups. The outcomes of 262 study patients were analyzed at ten years’ follow-up. Results. Patients in Group C were associated with increased mean liner wear rates compared to patients in Group A (0.133 mm/yr (SD 0.21) vs 0.031 mm/yr (SD 0.07), respectively; p < 0.001) and Group B (0.133 mm/yr (SD 0.21) vs 0.022 mm/yr (SD 0.05), respectively; p < 0.001) at ten years’ follow-up. Patients in Group C were also associated with increased risk of osteolysis and aseptic loosening requiring revision surgery, compared with patients in Group A (7/133 vs 0/133, respectively; p = 0.007) and Group B (7/133 vs 0/135, respectively; p = 0.007). There was a non-statistically significant trend towards increased mean liner wear rates in Group A compared with Group B (0.031 mm/yr (SD 0.07) vs 0.022 mm/yr (SD 0.05), respectively; p = 0.128). All three groups were statistically comparable preoperatively and at ten years’ follow-up when measuring normalized Western Ontario and McMaster Universities Osteoarthritis Index (p = 0.410), 36-Item Short Form Health Survey (p = 0.465 mental, p = 0.713 physical), and pain scale scores (p = 0.451). Conclusion. The use of UHMWPE was associated with progressively increased annual liner wear rates after THA compared to XLPE. At ten years’ follow-up, the group receiving UHMWPE demonstrated an increased incidence of osteolysis and aseptic loosening requiring revision surgery compared to XLPE. Femoral heads composed of OxZr were associated with trend towards reduced wear rates compared to CoCr, but this did not reach statistical significance and did not translate to any differences in osteolysis, functional outcomes, or revision surgery between the two femoral head components. Cite this article: Bone Joint J 2022;104-B(7):833–843

Aims. Biofilm infections are among the most challenging complications in orthopaedics, as bacteria within the biofilms are protected from the host immune system and many antibiotics. Halicin exhibits broad-spectrum activity against many planktonic bacteria, and previous studies have demonstrated that halicin is also effective against Staphylococcus aureus biofilms grown on polystyrene or polypropylene substrates. However, the effectiveness of many antibiotics can be substantially altered depending on which orthopaedically relevant substrates the biofilms grow. This study, therefore, evaluated the activity of halicin against less mature and more mature S. aureus biofilms grown on titanium alloy, cobalt-chrome, ultra-high molecular weight polyethylene (UHMWPE), devitalized muscle, or devitalized bone. Methods. S. aureus-Xen36 biofilms were grown on the various substrates for 24 hours or seven days. Biofilms were incubated with various concentrations of halicin or vancomycin and then allowed to recover without antibiotics. Minimal biofilm eradication concentrations (MBECs) were defined by CFU counting and resazurin reduction assays, and were compared with the planktonic minimal inhibitory concentrations (MICs). Results. Halicin continued to exert significantly (p < 0.01) more antibacterial activity against biofilms grown on all tested orthopaedically relevant substrates than vancomycin, an antibiotic known to be affected by biofilm maturity. For example, halicin MBECs against both less mature and more mature biofilms were ten-fold to 40-fold higher than its MIC. In contrast, vancomycin MBECs against the less mature biofilms were 50-fold to 200-fold higher than its MIC, and 100-fold to 400-fold higher against the more mature biofilms. Conclusion. Halicin is a promising antibiotic that should be tested in animal models of orthopaedic infection. Cite this article: Bone Joint Res 2024;13(3):101–109

Aims

We present the ten-year data of a cohort of patients, aged between 18 and 65 years (mean age 52.7 years; 19 to 64), who underwent total hip arthroplasty. Patients were randomised to be treated with a cobalt-chrome (CoCr) femoral head with an ultra-high molecular weight polyethylene (UHMWPE), highly cross-linked polyethylene (XLPE) or ceramic-on-ceramic (CoC) bearing surface.

Aims. We propose a state-of-the-art temporary spacer, consisting of a cobalt-chrome (CoCr) femoral component and a gentamicin-eluting ultra-high molecular weight polyethylene (UHMWPE) tibial insert, which can provide therapeutic delivery of gentamicin, while retaining excellent mechanical properties. The proposed implant is designed to replace conventional spacers made from bone cement. Methods. Gentamicin-loaded UHMWPE was prepared using phase-separated compression moulding, and its drug elution kinetics, antibacterial, mechanical, and wear properties were compared with those of conventional gentamicin-loaded bone cement. Results. Gentamicin-loaded UHMWPE tibial components not only eradicated planktonic Staphylococcus aureus, but also prevented colonization of both femoral and tibial components. The proposed spacer possesses far superior mechanical and wear properties when compared with conventional bone cement spacers. Conclusion. The proposed gentamicin-eluting UHMWPE spacer can provide antibacterial efficacy comparable with currently used bone cement spacers, while overcoming their drawbacks. The novel spacer proposed here has the potential to drastically reduce complications associated with currently used bone cement spacers and substantially improve patients’ quality of life during the treatment. Cite this article: Bone Joint J 2020;102-B(6 Supple A):151–157

Aims. The aim of this prospective cohort study was to evaluate the early migration of the TriFit cementless proximally coated tapered femoral stem using radiostereometric analysis (RSA). Methods. A total of 21 patients (eight men and 13 women) undergoing primary total hip arthroplasty (THA) for osteoarthritis of the hip were recruited in this study and followed up for two years. Two patients were lost to follow-up. All patients received a TriFit stem and Trinity Cup with a vitamin E-infused highly cross-linked ultra-high molecular weight polyethylene liner. Radiographs for RSA were taken postoperatively and then at three, 12, and 24 months. Oxford Hip Score (OHS), EuroQol five-dimension questionnaire (EQ-5D), and adverse events were reported. Results. At two years, the mean subsidence of the head and tip for the TriFit stem was 0.38 mm (SD 0.32) and 0.52 mm (SD 0.36), respectively. The total migration of the head and tip was 0.55 mm (SD 0.32) and 0.71 mm (SD 0.38), respectively. There were no statistically significant differences between the three to 12 months' migration (p = 0.105) and 12 to 24 months' migration (p = 0.694). The OHS and EQ-5D showed significant improvements at two years. Conclusion. The results of this study suggest that the TriFit femoral stem achieves initial stability and is likely to be stable in the mid and long term. A long-term outcome study is required to assess late mechanisms of failure and the effects of bone mineral density (BMD) related changes. Cite this article: Bone Joint J 2021;103-B(4):644–649

We describe a cohort of patients with a high rate of mid-term failure following Kinemax Plus total knee replacement inserted between 1998 and 2001. This implant has been recorded as having a survival rate of 96% at ten years. However, in our series the survival rate was 75% at nine years. This was also significantly lower than that of subsequent consecutive series of PFC Sigma knee replacements performed by the same surgeon. No differences were found in the clinical and radiological parameters between the two groups. At revision the most striking finding was polyethylene wear. An independent analysis of the polyethylene components was therefore undertaken. Scanning electron microscopy revealed type 2 fusion defects in the ultra-high molecular weight polyethylene (UHMWPE), which indicated incomplete boundary fusion. Other abnormalities consistent with weak UHMWPE particle interface strength were present in both the explanted inserts and in unused inserts from the same period. We consider that these type 2 fusion defects are the cause of the early failure of the Kinemax implants. This may represent a manufacturing defect resulting in a form of programmed polyethylene failure

Majority of ultra-high molecular weight polyethylene (UHMWPE) medical devices used in total joint arthroplasty are crosslinked using gamma radiation to improve wear resistance. Alternative methods of crosslinking are urgently needed to replace gamma radiation due to rapid decline in its supply. Peroxide crosslinking is a candidate method with widespread industrial applications. Oxidative stability and biocompatibility, which are critical requirements for medical device applications, can be achieved using vitamin-E as an additive and by removing peroxide by-products through high temperature melting, respectively. We investigated compression molded UHMWPE/vitamin-E/di-cumyl peroxide blends followed by high-temperature melting in inert gas as a material candidate for tibial knee inserts. Wear resistance increased and mechanical properties remained largely unchanged. Oxidation induction time was higher than most of the other clinically available formulations. The material passed the local-end point biocompatibility tests per ISO 10993. Compounds found in exhaustive extraction were of no concern with margin-of-safety values well above the accepted level, indicating a desirable toxicological risk profile. Peroxide crosslinked, vitamin-E stabilized, and high temperature melted UHMWPE has recently been cleared for clinical use in tibial knee inserts. With all the salient characteristics needed in a material that can provide superior long-term performance in total joint patients, peroxide crosslinking can replace gamma radiation crosslinking of UHMWPE for use in all total joint replacement implant including acetabular liners

This prospective randomised controlled trial aims to compare the clinical and radiological outcomes of ceramic on ceramic, cobalt chrome on ultra-high molecular weight polyethylene, and cobalt chrome on highly cross-linked polyethylene bearing surfaces at a minimum of five years. One hundred and two primary total hip replacements were performed in ninety one patients between February 2003 and March 2005. All patients were younger than 65 (mean 52.7, 19–64). They were randomised to receive one of the three bearing surfaces. All patients had 28mm articulations with a Reflection uncemented acetabular component and a Synergy stem (Smith & Nephew, Memphis, Tennessee). Patients were followed up periodically up to at least sixty months following surgery. Outcome measures included WOMAC and SF12 scores. Radiological assessment included implant position, evidence of osteolysis and measurement of linear wear. Ninety seven hip replacements in eighty seven patients were available for review at a minimum of five years. Two hips were revised (one for infection and one for periprosthetic fracture), leaving a total of ninety four hips available for final review. There were no differences in age, gender, body mass index, diagnosis, level of activity, and co-morbidities between the three groups. At a minimum of five years there were no statistical differences in the clinical outcomes using the WOMAC or SF12 scores. Three patients in the ceramic group reported squeaking. Radiological evaluation revealed mean annual wear rates in the ceramic group of 0.006mm/yr, standard polyethylene of 0.151mm/yr and highly cross linked polyethylene of 0.059mm/yr. ANOVA analysis revealed these differences in wear rates to be significant (p<0.0001). In the mid term there are no differences in clinical outcome between ceramic on ceramic, cobalt chrome on ultra-high molecular weight polyethylene, and cobalt chrome on highly cross-linked polyethylene bearing surfaces in total hip arthroplasty. Ultra high molecular weight polyethylene has a significantly greater annual linear wear rate than highly cross-linked polyethylene