Wear of the ultra-high molecular weight polyethylene (UHMWPE) insert is one of the major issue related to orthopaedic implants. In this study, the tribo-mechanical properties of zirconia-coated UHMWPE deposited by means of Pulsed Plasma Deposition (PPD) technique were analyzed. Specifically, strength to local plastic deformation, indentation work portioning and creep behavior were evaluated through nanoindentation and micro-scratch tests, whereas preliminary wear data were obtained by tribology tests. A strong reduction of plastic deformation and a drop of the creep phenomenon for the zirconia-coated UHMWPE were evidenced, whereas - in spite of similar wear data - different wear mechanism was also detected. This study supported the use of hard ceramic thin films to enhance the mechanical performance of the plastic inserts used in orthopaedics

Introduction. Protective hard coatings are appealing for several technological applications like solar cells, organic electronics, fuel cells, cutting tools and even for orthopaedic implants and prosthetic devices. At present for what concerns the application to prosthetic components, the coating of the surface of the metallic part with low-friction and low-wear materials has been proposed [1]. Concerning the use of ceramic materials in joint arthroplasty, zirconia-toughned-alumina (ZTA) reported high strength, fracture toughness, elasticity, hardness, and wear resistance [2]. The main goal of this study was to directly deposit ZTA coating by using a novel sputter-based electron deposition technique, namely Pulsed Plasma Deposition (PPD) [3]. The realized coatings have been preliminary characterized from the point of view of morphology, wettability, adhesion and friction coefficients. Materials and methods. ZTA coatings were deposited by PPD technique, which is able to maintain the stoichiometry of the starting target. In this case we started from a cylindrical ZTA target (30 mm diameter × 5 mm thickness, 75% alumina / 25% zirconia). The morphology, micro-structure and chemistry of deposited coatings were characterized by Scanning Electron Microscopy (SEM) equipped with Energy Dispersive X-ray Spectrosopy (EDS) and Atomic Force Microcscope (AFM). Coating-substrate interface quality were investigated by microscratch tests. The degree of wetting was estimated by measuring the contact angle between a drop of 1 ml of ultrapure water and the surface of the sample. Preliminary ball-on-disk tribological tests were carried out in air and deionized water coupling ZTA-coated stainless steel ball (AISI 420, 3 mm radius, grade 200) against medical grade UHMWPE to evaluate the friction of the proposed coupling. Results. Deposited ZTA films exhibited a smooth nanostructured surface. Coatings up to several microns thick have been deposited by PPD [Fig. 1 – SEM image (left) and cross section (right)]. Mechanical tests showed a well-adherent films were deposited. In particular, the good interface adhesion was assessed by scratch tests, reporting at about 0.8 N the first formation of cracking in the coating during testing. The contact angles revealed an hydrophobic behavior of the coating (average contact angle 116° ± 2°), probably due to the nano-roughness of the coating itself [Fig. 2 – Contact angle]. Preliminary tribological tests carried out in deionized water after up to 10000 m tracks showed good average friction coefficient ranging from 0.12 to 0.15 [Fig. 3 – Friction coefficient]. Conclusions. We have presented the preliminary results of a novel approach aiming to the drastically improve the performance of prosthetic couplings by introducing hard ceramic coating. The results showed suggested the feasibility of pursuing this approach of realizing ZTA coatings by means of PPD technique. Further analyese on mechanical properties, nano-roughness and tribology should be performed. Well-adherent ZTA films deposited directly on the surface of prosthetic components of a joint implant would then allow a drastic improvement of the actual prosthetic behaviour

Introduction. Protective hard coatings are appealing for several technological applications and even for orthopaedic implants and prosthetic devices. For what concerns the application to prosthetic components, coating of the surface of the metallic part with low-friction and low-wear materials has been proposed [1, 2]; at the same time, concerning use of ceramic materials in joint arthroplasty, zirconia-toughned-alumina (ZTA) ceramic material has shown high strength, fracture toughness, elasticity, hardness, and wear resistance [3, 4]. The purpose of this study was to directly deposit ZTA coatings by using a novel sputter-based electron deposition technique, namely Pulsed Plasma Deposition (PPD) [5]. Preliminary characterization of realized coatings from the point of view of morphology, wettability, adhesion and friction coefficients was performed. Materials and methods. PPD technique was used to deposit ZTA coatings; this technique is able to maintain the stoichiometry of the starting target. In this study we started from a cylindrical ZTA target (30 mm diameter × 5 mm thickness, 75% alumina / 25% zirconia) and followed the procedure described by Bianchi et al [5]. Characterization of morphology, micro-structure and chemistry of deposited coatings was performed by Scanning Electron Microscopy (SEM) equipped with Energy Dispersive X-ray Spectroscopy (EDS) and Atomic Force Microscope (AFM). Coating-substrate interface quality were investigated by micro-scratch tests. Measurement of the contact angle between a drop of 1 ml of ultrapure water and the surface of the sample was performed to estimate the degree of wetting. A ZTA-coated stainless steel ball (AISI 420, 3 mm radius) was coupled against medical grade UHMWPE to evaluate the friction of the proposed coupling in preliminary ball-on-disk tribological tests. Results. Coatings up to several microns thick have been deposited by PPD. Deposited ZTA films exhibited a smooth nanostructured surface. Mechanical tests showed a well-adherent films were deposited. In particular, scratch tests assessed a good interface adhesion: first formation of cracking in the coating during testing was reported at about 0.8 N. Hydrophobic behavior of the coating was revealed by contact angles (average contact angle 116° ± 2°), probably due to the nano-roughness of the coating itself. Good average friction coefficient ranging from 0.12 to 0.15 was showed by preliminary tribological tests carried out in deionized water after up to 10000 m tracks. Conclusions. The preliminary results of a novel approach aiming to drastically improve the performance of prosthetic couplings by introducing hard ceramic coating was presented. Showed results suggested the feasibility of pursuing this approach of realizing ZTA coatings by means of PPD technique. Further analyses on mechanical properties, nanoroughness and tribology are ongoing. Well-adherent ZTA films deposited directly on the prosthetic components surface would then allow a drastic improvement of the actual prosthetic behaviour

Animal studies examining tendon-bone healing have demonstrated that the overall structure, composition, and organization of direct type entheses are not regenerated following repair. We examined the effect of Low-Intensity Pulsed Ultrasound (LIPUS) on tendon-bone healing. LIPUS may accelerate and augment the tendon-bone healing process through alteration of critical molecular expressions. Eight skeletally mature wethers, randomly allocated to either control group (n=4) or LIPUS group (n=4), underwent rotator cuff surgery following injury to the infraspinatus tendon. All animals were sacrificed 28 days post surgery to allow examination of early effects of LIPUS. Humeral head – infraspinatus tendon constructs were harvested and processed for histology and immunohistochemical staining for BMP2, Smad4, VEGF and RUNX2. All the growth factors were semiquantitative evaluated. T-tests were used to examine differences which were considered significant at p < 0.05. Levene's Test (p < 0.05) was used to confirm variance homogeneity of the populations. The surgery and LIPUS treatment were well tolerated by all animals. Placement of LIPUS sensor did not unsettle the animals. Histologic appearance at the tendon-bone interface in LIPUS treated group demonstrated general improvement in appearance compared to controls. Generally a thicker region of newly formed woven bone, morphologically resembling trabecular bone, was noted at the tendon-bone interface in the LIPUS-treated group compared to the controls. Structurally, treatment group also showed evidence of a mature interface between tendon and bone as indicated by alignment of collagen fibres as visualized under polarized light. Immunohistochemistry revealed an increase in the protein expression patterns of VEGF (p = 0.038), RUNX2 (p = 0.02) and Smad4 (p = 0.05) in the treatment group. There was no statistical difference found in the expression patterns of BMP2. VEGF was positively stained within osteoblasts in newly formed bone, endothelial cells and some fibroblasts at the interface and focally within fibroblasts around the newly formed vessels. Expression patterns of RUNX2 were similar to that of BMP-2; the staining was noted in active fibroblasts found at the interface as well as in osteoblast-like cells and osteoprogenitor cells. Immunostaining of Smad4 was present in all cell types at the healing interface. The results of this study indicate that LIPUS may aid in tendon to bone healing process in patients who have undergone rotator cuff repair. This treatment may also be beneficial following other types of reconstructive surgeries involving the tendon-bone interface

Tibial shaft fractures have a high incidence of delayed and non-union, often requiring multiple procedures. Pulsed electromagnetic field (PEMF) stimulation is a safe and effective treatment for tibial non union but little is known about the efficacy of PEMF in preventing non-union in acute fractures. Between August 2005 and December 2008, eligible patients presenting at six major metropolitan hospitals with acute tibial shaft fractures (AO classification 4-2) were included. Participants were randomised by an independent allocation centre to identical active or inactive PEMF devices, both prescribed to be worn ten hours daily for twelve weeks. Baseline data were collected, and patients and surgeons were surveyed serially via post and/or phone at three, six and twelve months. Participants, data collectors and data analysts were blinded. The main outcome was any surgical intervention for delayed/non union. Data from 150 patients (76 active and 74 inactive) were available for analysis (12 month follow up 78%). There was no between-group difference in age, gender, mechanism of injury, open grade, smoking status, or compliance with the device (hours of use). Overall compliance was moderate (5.7 hours daily use). Fifteen of 76 (20%) of active device patients required surgery for delayed/non-union vs. 8 of 74 (11%) in the placebo group; odds ratio of surgery=2.03, p=0.13, 95% CI 0.80 to 5.12. An intention to treat analysis adjusted for open grade and hours the device was used showed an odds ratio of requiring surgery of 1.78 (p=0.24, 95% CI 0.68 to 4.64). A sub-group analysis of 80 compliant patients (defined a priori as a minimum average of six hours daily use) was performed. Nine of 35 (26%) patients with an active device required surgery for delayed/non-union vs. 3 of 45 (7%) in the placebo group; odds ratio of surgery=7.60 (p=0.017, 95% CI 1.43 to 40.24). Based on these unexpected initial results, PEMF stimulation does not prevent revision surgery for delayed/non-union in acute fractures of the tibial shaft

Staphylococcus aureus is responsible for 60–70% infections of surgical implants and prostheses in Orthopaedic surgery, with cumulative treatment costs for all prosthetic joint infections estimated to be ∼ $1 billion per annum (UK and North America). Its ability to develop resistance or tolerance to a diverse range of antimicrobial compounds, threatens to halt routine elective implant surgery. One strategy to overcome this problem is to look beyond traditional antimicrobial drug therapies and investigate other treatment modalities. Biophysical modalities, such as ultrasound, are poorly explored, but preliminary work has shown potential benefit, especially when combined with existing antibiotics. Low intensity pulsed ultrasound is already licensed for clinical use in fracture management and thus could be translated quickly into a clinical treatment

Using a methicillin-sensitive S. aureus reference strain and the dissolvable bead assay, biofilms were challenged with gentamicin +/− low-intensity ultrasound (1.5MHz, 30mW/cm2, pulse duration 200µs/1KHz) for 180 minutes and 20 minutes, respectively. The primary outcome measures were colony-forming units/mL (CFU/mL) and the minimum biofilm eradication concentration (MBEC) of gentamicin. The mean number of S. aureus within control biofilms was 1.04 × 109 CFU/mL. Assessment of cellular metabolism was conducted using a liquid-chromatography-mass spectrometry, as well as a triphenyltetrazolium chloride assay coupled with spectrophotometry.

There was no clinically or statistically significant (p=0.531) reduction in viable S. aureus following ultrasound therapy alone. The MBEC of gentamicin for this S. aureus strain was 256 mg/L. The MBEC of gentamicin with the addition of ultrasound was reduced to 64mg/L. Metabolic activity of biofilm-associated S. aureus was increased by 25% following ultrasound therapy (p < 0 .0001), with identification of key biosynthetic pathways activated by non-lethal dispersal.

Low intensity pulsed ultrasound was associated with a four-fold reduction in the effective biofilm eradication concentration of gentamicin, bringing the MBEC of gentamicin to within clinically achievable concentrations. The mechanism of action was due to partial disruption of the extracellular matrix which led to an increase of nutrient availability and oxygen tension within the biofilm. This metabolic stimulus was responsible for the reversal of gentamicin tolerance in the biofilm-associated S. aureus.

Aim

Irrigation is a major step during debridement surgery in the context of Prosthetic Joint Infections (PJI), but its effects on biofilms are poorly described.

The present study aims at evaluating the effect of PW alone or followed by antibiotics on MSSA and MRSA biofilms grown on Ti6Al4V coupons in-vitro.

Background

Fracture non-union is still a major challenge to the orthopaedic surgeon and established non-union has zero probability of achieving union without intervention.

Ultrasound treatment can be used as an alternative to surgical methods for treating non-union or to enhance healing in a delayed union. This study presents our short-term results of using low intensity pulse ultrasound stimulation in long bone non-union. 18 patients with surgically treated long bone non-union were treated using the Exogen® ultrasound stimulator (Smith & Nephew Inc., UK). The average age of patients was 48 years (20–73 yrs). There were 8 femur fractures, 9 tibial fractures and 1 knee arthrodesis. 5 of these patients had infected non-union. The average follow up after initiation of treatment was 4 months (range 2–8 months). They received 20 minutes stimulation daily at the fracture site with regular follow up in clinic. We reviewed their serial radiographs and clinical progress. The mean interval to initiation of the ultrasound treatment was 7.9 months (2–27 months). Complete bony union was obtained in 6 of the 18 cases (33%) within 4 months of initiation of treatment. In 7 of 18 cases (38%) there was good evidence of progress towards bony union, while in 4/18(22%) patients there was no progress towards union at average of 4 months (range 2–8 months). There were no complications noted with this treatment. Most non-unions are treated by surgical revision, with consolidation rates ranging from 85 to 100% according to previous studies. Our study suggested 72% patients showing progress towards union with 33% achieving bony consolidation at 4 months. Patients with infected non-union also benefitted from this treatment. In summary ultrasound treatment can be a viable option to treat long bone non-unions, which may avoid the morbidity and complications associated with surgery.

INTRODUCTION

Several reports suggest that low-intensity pulsed ultrasound stimulation (LIPUS) facilitates chondrogenesis¹⁾. Recently it has been suggested that LIPUS may be transmitted via Integrin: a protein which mediates cellular attachment between cells and extracellular matrix²⁾. In this study, the Arg-Gly-Asp (RGD) amino acid sequence, which is a ligand of Integrin, was induced to the fibroin substrates by either gene transfer or physical mixing, and the variation of chndrocyte response to LIPUS was evaluated.

Gold standard for the management of non-union is open surgical debridement, stabilisation, and autologous bone grafting. LIPUS is becoming more popular, yet the evidence is still inconclusive. LIPUS involves the use of ultrasound at the fracture site with little risk to the patient.

The purpose of this study was to assess effectiveness and cost benefit of LIPUS in the management of non-unions post sustaining an open fracture.

We retrospectively reviewed 29 patients with open fractures with established non-union undergoing LIPUS since 2010 (4 females, mean age 48) range 3–27 months, mean 9 months, either post injury or last intervention. All were tertiary referrals, sustaining injuries to the following areas; Tibial 21, Femur 6, Humerus 2, Radius 1. Definitive fixation being; 9 TSF's, 11 IMN's, 9 plates. (undergoing a mean 2.4 procedures). Aside from sustaining an open fracture, 7 had risk factors for non-unions 5 smokers, 2 NSAID's. Failure of treatment was based on undertaking bone grafting.

In 28 patients (1 lost to follow up) union was achieved in 71% (mean 157 days). All were screened for infection, 4 had organisms on enrichment culture. 8 (5 Gustillo Anderson Grade 3A/B) injuries did not show evidence of callus formation, LIPUS was discontinued and grafting performed. Open fractures were graded as; 7 Grade 1, 4 Grade 2, 8 Grade 3A, 10 Grade 3B being received. Of these; 20 underwent primary closure, 6 free flaps and 3 SSG. The cost of LIPUS is approx £2500, compared bone grafting using autologous iliac crest graft with no medical comorbidities of £3715.

This case series further supports union rates after LIPUS. Cost and morbidity benefit of utilising LIPUS over opting for bone grafting initially is £1215 per patient. Whilst autologous bone grafting is currently the gold standard, it is not without morbidity. We achieved union rates of 71% despite a number of patients having recognised risk factors, showing that LIPUS is a useful resource in the management of non-union.

Introduction

When osteoarthritis occurs, joint replacement is the most frequent treatment. Currently, the mean survival rate for total joint arthroplasty is ∼90% after 10 years: the main reason for long-term implant failure, that generally required a revision surgery, are osteolysis and aseptic loosening of the implant, which are strongly correlated with wear debris formation from the UHMWPE insert [Ingham, 2005], as a consequence of the cyclic loading against the metallic or ceramic counterface [Dumbleton, 2002]. Wear debris bring to chronic inflammation of periprosthetic tissues causing an increase of bone reabsorption that finally provoke aseptic loosening, so implant failure[Holt, 2007]. Different solutions were proposed to reduce wear debris production but agreement has not been achieved yet. Our challenging approach prefigures the direct coating of the plastic component with a hard and well-adherent ceramic film, in order to drastically reduce wear debris formation from the plastic substrate while preserving its well-established bulk mechanical properties, especially under high local loads [Bianchi, 2013].

Introduction. Total joint arthroplasty is frequently necessary when a traumatic or degenerative disease leads to develop osteoarthritis (OA). Nowadays, the main reason for long term prosthesis failure is due to osteolysys and aseptic loosening of the implant itself, that are related to UHMWPE wear debris [1–3]. Different solutions to overcome this issue have been proposed, including different couplings like metal-on-metal and ceramic-on-ceramic. Our hypothesis was that a hard ceramic thin film realized on the plastic component (i.e. UHMWPE) could improve the friction and wear performance in a prosthetic coupling. The purpose of the presented study was therefore to characterize from the point of view of structure and mechanical performance of this ceramic-coated plastic component. The thin films were specifically realized by means of the novel Pulsed Plasma Deposition (PPD) technique [4]. Materials and methods. PPD technique was used to deposit Yttria-stabilized zirconia (YSZ at 3%) films on medical-grade UHMWPE substrates [4]. The morphology and micro-structure were characterized by Scanning Electron Microscopy (SEM) equipped with Energy Dispersive X-ray Spectroscopy (EDS), X-ray diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS). By means of nanoindentation and scratch tests mechanical properties were investigated. Ball-on-disk tribological tests were carried out in air, deionized water and physiological solution against alumina balls (6 mm diameter, grade 200) used as counterpart; friction evaluation of the proposed approach and the corresponding worn track were analyzed by SEM-EDS. Results. Deposited zirconia films up to several micron thickness exhibited a fully cubic structure and a smooth nanostructured surface. Good high hardness and Young's modulus values (17 GPa and 154 GPa respectively) were revealed by nanoindentation tests, while no radial cracks, spalling or pile-up phenomena were observable at critical fracture tests. Assessment of the very strong interface adhesion was observed by scratch tests (with initial delamination at about 2 N load). When the UHMWPE substrate was covered by a ceramic film as thin as 1.5 micron, an indentation depth reduction of about 330% was registered. Further, the material yielding under an applied constant load (creep) was larger for UHMWPE compared to coated UHMWPE, whose total creep being only the 19% of the total creep of UHMWPE, respectively. Finally, preliminary tribological tests carried out in air against an alumina ball counterpart showed wear rate as low as 3.2*10-6mm3N-1m-1 after 500.000 cycles, showing an average friction coefficient evaluated on unpolished materials ranging from 0.15 to 0.3 in air. Conclusions. The proposed approach was able to directly coat the plastic insert of a commercial implant joint with hard ceramic materials, thus providing specific additional mechanical and superficial properties, while preserving the well established mechanical properties of UHMWPE. The results of this study showed an alternative and promising approach to improve UHMWPE mechanical properties in arthroplasty