Introduction

Trabecular Titanium is a biomaterial characterized by a regular three-dimensional hexagonal cell structure imitating trabecular bone morphology. Components are built via Electron Beam Melting technology in aone- step additive manufacturing process. This biomaterial combines the proven mechanical properties of Titanium with the elastic modulus provided by its cellular solid structure (Regis 2015 MRS Bulletin). Several in vitro studies reported promising outcomes on its osteoinductive and osteoconductive properties: Trabecular Titanium showed to significantly affect osteoblast attachment and proliferation while inhibiting osteoclastogenesis (Gastaldi 2010 J Biomed Mater Res A, Sollazzo 2011 ISRN Mater Sci); human adipose stem cells were able to adhere, proliferate and differentiate into an osteoblast-like phenotype in absence of osteogenic factors (Benazzo 2014 J Biomed Mater Res A). Furthermore, in vivo histological and histomorphometric analysis in a sheep model indicated that it provided bone in-growth in cancellous (+68%) and cortical bone (+87%) (Devine 2012 JBJS). A multicentre prospective study was performed to assess mid-term outcomes of acetabular cups in Trabecular Titanium after Total Hip Arthroplasty (THA).

The discussion will focus on new approaches to reduce bacterial adhesion on the surface of polymethylmethacrylate (PMMA) in contact with bone, comparing the clinical and engineering point of view. One possibility is to encourage and speed up direct interaction with the bone, for example by adding a bioactive phase in the cement (hydroxyapatite, glass and bioactive glass ceramic). A widespread strategy is also the addition of different types of antibiotics (gentamicin, tobramycin vancomycin, etc.), although they are known to have some drawbacks: not complete release, resistant strain development. Another strategy could be represented by the PMMA-based composite cements loaded with a completely inorganic filler consisting of a bioactive glass doped with ions whose bioactivity mechanism is well-known and encompasses a chemical and biological interaction with tissues promoting osteoinduction. Bioactive glasses can be doped with antibacterial ions (silver, copper, etc.) preserving their biocompatibility and bioactivity and, at the same time, acquiring antibacterial properties. Thus, it is possible to produce composite cements that combine the properties of the polymer matrix with those of the inorganic filler, overcoming the main problems associated with the use of antibiotics. An additional possibility is the addition of essential oils, vegetable oils with remarkable antibacterial properties.

There is still little information on the histological characteristics of the acetabular bone tissue after failure of the primary prosthetic component. The purpose of this study is to characterize the viability and quality of the acetabular bone tissue in patients undergoing acetabular revision for aseptic loosening of uncemented components.

19 patients were enrolled: 14 hip revisions and 5 primary total hip arthroplasty. Samples collecting: three acetabular bone biopsy of patients were collected at the time of surgery with a 8G diameter needle after reaming. Histological evaluation: all samples, after removing the mineral component, were cut longitudinally with a thickness section of 5μm and colored with hematoxylin-eosin dichromic dye. Histological evaluation was done by optical microscopy with 40× magnification. Five bone quality classes were developed by evaluating percentage of aseptic necrosis, percentage of active osteoblasts, presence of osteopenia, presence of osteoclasts, absence of intramedullary hematopoietic component. Histological evaluation: the bone quality of cases was significantly poorer than the controls. The differences found were statistically significant between the two groups for percentage of necrosis (p=0.0033), percentage of active osteoblasts (p=0.0071) and presence of osteopenia (p=0.037).

Overall bone quality was significantly worse in the study group due reduced viability, overturn of lamellar structures, reduced amount of intramedullary hematopoietic component in respect to the controls; this could result in poor ability of the host bone to interact with the implanted components.

Tannast has recently shown that safe hip dislocation (SHD) for femoroacetabular impingement treatment does not result in atrophy and degeneration of periarticular hip muscles. In more complex procedures, such as relative neck lengthening for Perthes disease (PD) or modified Dunn procedure for slipped capital epiphysis (SCFE), minimus gluteus femoral insertion is detached to achieve enough mobility of osteotomized trochanter and to fix the latter more distally. Aim of this study was to evaluate MRI appearance of minimus and medius gluteus after relative neck lengthening.

Patients treated with SHD and relative neck lengthening eventually associated to epiphyseal realignment for PD or SCFE treatment underwent magnetic resonance imaging (MRI) to study gluteus minimus (MI) and medius (ME) muscles. In the axial T1-weighted sequences, cross sectional area (CSA) and signal intensity were evaluated at acetabular roof level. Statistical comparison was made with the opposite healthy side.

Fifteen patients underwent an MRI at an average of 59 months (SD=27.3) after surgery.

Average ratio between gluteus minimus CSA (treated/healthy side) was 0.90 (SD=0.2): this reduction in volume was statistically significant (p=0.04) as well as the signal intensity (p=0.04). CSA and signal intensity of gluteus medius did not differ between two sides (respectively p=0.78 and p=0.30).

In conclusion, gluteus medius appearance was not influenced by distal fixation of the trochanter. The minimus gluteus was reduced in volume as much as 10% in respect to healty side; increased signal intensity in MRI T1-weighted (fatty infiltration) was found in the minimus gluteus.

Summary

Prosthetic UHMWPE added with vitamin E and crosslinked UHMWPE are able to decrease significantly the adhesion of various bacterial and fungal strains limiting biomaterial associated infection and consequent implant failure.

Introduction

Trabecular Titanium™ is a highly porous biomaterial with a regular hexagonal cell structure, which has shown excellent mechanical properties. Several in vitro studies reported promising data on its osteoinductive and osteoconductive properties. Furthermore, it has demonstrated in vivo to enhance bone in-growth. Aim of this multicentre prospective study was to assess Trabecular Titanium™ osseointegration by measuring change in bone mineral density (BMD) around a cementless DELTA-TT cup with dual-emission X-ray absorptiometry (DXA).

Trabecular TitaniumTM is a tri-dimensional material composed by multi-planar regular hexagonal cells and characterised by a highly open porosity that has been studied to optimise bone osteointegration. The aim of this study is to evaluate bone remodelling measuring BMD changes around an acetabular cup made from Trabecular TitaniumTM in primary total hip arthroplasty (THA).

Between February 2009 and December 2010, 89 patients (91 hip) underwent primary THA with a modular acetabular cup in Trabecular TitaniumTM (DELTA-TT cup, Limacorporate, Villanova di San Daniele, Italy). The average age was 63.5± 9.4 years, the average height and weight were 75.9± 12.9 kg and 168.8± 8.9 cm, respectively (av. BMI 26.8± 4.2). There were 46 (51.7%) males and 43 (48.3%) females affected by primary coxarthrosis in 80 (87.9%) cases, avascular necrosis in 5 (5.5%), posttraumatic coxarthrosis in 3 (3.3%), dysplasia in 2 (2.2) and oligoarthritis in 1 (1.1%) case. The study includes the clinical evaluation with Harris Hip Score (HHS) and SF-36, radiographic evaluation and dual-energy x-ray absorptiometry (DEXA) analysis preoperatively and postoperatively at 1 week, 3, 6, 12 and 24 months.

Preliminary results are currently available for 47 patients at 12 months, 68 at 6 months and 80 at 3 months. The average HHS significantly improved from 48.7± 14.99 preoperatively to 93.8± 5.91 at 12 months, with a constant progression in the intermediate follow-ups. All patients showed a significant ROM increase, with an average flexion from 86.6°± 15.9° preoperatively to 105°±13.14 at 12 months. Sf-36 highlighted a satisfactory improvement of general health status from an average preoperative value of 50.8± 18.7 to 80.7± 12.9 at 12 months (from 42.9 to 80.1 for physical health; from 58.4 to 81.3 for mental one). All cups were stable at 12 months with no radiolucent lines. Preliminary DXA analysis reported an initial bone mineral density decrease from 1 week baseline values (BMD R1: 1.40± 0.37; R2: 1.20± 0.45; R3:1.16± 0.31) to 3 months (BMD R1: 1.31± 0.41; R2: 1.17± 0.3; R3: 1.06± 0.37) followed by BMD recovery up to initial values (BMD R1: 1.37± 0.3; R2:1.18± 0.34; R3: 1.12± 0.36) at 12 months.

Trabecular TitaniumTM demonstrates a good primary and secondary stability. Preliminary densitometric outcome confirms an optimal osseointegration of the DELTA-TT cup and early clinical and patient subjective results are very promising at a short term follow-up. However, the completions of follow-up evaluation are necessary to draw a conclusive analysis.

INTRODUCTION

Trabecular Titanium™ is an innovative material characterised by an high open porosity and composed by multi-planar regular hexagonal cells. It is not a traditional coating and its tri-dimensional structure has been studied to optimise osteointegration. Furthermore, it has excellent mechanical properties, as a very high tensile and fatigue resistance and an elastic module very similar to the that of the trabecular bone. The aim of this study is to evaluate the osteointegration and bone remodelling measuring the longitudinal pattern of change in BMD around a cementless acetabular cup made from Trabecular Titanium™ (Delta TT cup, Lima Corporate, Italy) in primary total hip arthroplasty (THA).

The performance of ultra-high molecular weight polyethylene (UHMWPE) used in total joint replacement prosthesis depends on its wear resistance, oxidation resistance and mechanical properties. Several studies have now established that radiation crosslinking by applying a dose of 50–100 kGy gamma or electron beam radiation followed by remelting to quench free radicals fulfils the criterion of high wear resistance as well as oxidation resistance. However, post-irradiation remelting leads to a decrease in several mechanical properties of UHMWPE including fracture toughness and resistance to fatigue crack propagation, which are deemed important for components in joints where they are subjected to high stresses, such as in tibial components.

In this study, we used uniaxial compression and high-pressure crystallization to disentangle UHMWPE, expecting that this would assist in increasing its crystallinity since disentangled polymer chains would be more readily incorporated into crystalline lamellae, thereby increasing overall crystallinity. This could then result in an increase in some mechanical properties of irradiated, remelted UHMWPE since high crystallinity is associated with high modulus and yield stress. Uniaxial compression of irradiated, remelted GUR 1050 UHMWPE at 130C to a compression ratio up to 2.5 followed by remelting to recover crystallographic orientation showed no statistically significant increase in crystallinity (p> 0.05, ANOVA). High-pressure crystallization at 500 MPa and temperatures in a range of 130-220C also did not show statistically significant increase in crystallinity of irradiated, remelted UHMWPE. However high-pressure crystallization at 500MPa pressure and 240C, where crystallization occurs via the hexagonal phase, increased the crystallinity from 46.2% to 56.4% (p< 0.05, ANOVA).

We conclude that high-pressure crystallization via the hexagonal phase is more effective than uniaxial compression followed by strain recovery or high-pressure crystallization via the orthorhombic phase in increasing the crystallinity of irradiated, remelted UHMWPE, with potential to recover some mechanical properties.

Aims: ACL lesion is one of the most frequent event in sport injuries. It is generally a complete lesion which does not evolve to a spontaneous healing. In particular, after non surgical treatment, ACL often repairs on PCL with a residual articular laxity. A healing response technique has been described to treat ACL incomplete tears in skeletally immature athletes. Our technique is based on microfractures next to the ACL femoral insertion to obtain a scar reinforcement thanks to the action of mes-enchymal stem cells.

Methods: The authors report their experience using the same surgical technique and rehabilitation protocol in patients selected by type of lesion, age and time from injury.

The authors selected for the study young-middle age active patients, with incomplete ACL lesion: 27 patients (mean age of 23 years) have been evaluated, inclusion criteria was Lachman test < 1 cm, negative Jerk test and a proximal partial tear of ACL on MRI. Before and after surgery the patients have been evaluated using KT1000, MRI, clinical examination and Lysholm score with a 3 years average follow up.

Results: Clinical examination showed a significative improvement in Lysholm score from 63 to 85 and a minor anterior tibial translation measured with KT1000 (from a mean difference between the two legs of 5 mm preoperatively to 2 mm postoperatively). In only one case the ACL didn’t seem to heal and was necessary the traditional reconstruction. MRI at one year pointed out a reparative healing in almost all cases.

Conclusions: according to these results the healing response procedure can restore a subjective and objective stability and knee function, with proper patient selection and strictly following the rehabilitation protocol despite of age and time of lesion.

Aims: Crosslinked acetabular inserts have been introduced as a solution to the wear related periacetabular osteolysis, caused by the polyethylene wear debris. Laboratory tests and simulators have demonstrated that crosslinked-polyethylene has a higher resistance to wear than conventional polyethylene. However, studies have shown early crack or degeneration of crosslinked inserts. Concerns still remain about the clinical performances of crosslinked inserts. Although questionable, the roentgenographic measurement of the wear of the cup represents an indicator of the performance of the implant. Early catastrophic failures of other inserts taught us that for new materials it is mandatory to conduct an accurate clinical surveillance. In this work the radiographic-evaluated linear wear of a group of cross-linked inserts is compared to that of a non-crosslinked inserts for the same socket at 5 years.

Methods: From 2000 to 2002 we implanted a series of cups in which crosslinked and conventional acetabular inserts were placed randomly. Patients from each group underwent radiographic assessment after implantation, at 3 and 6 months and then yearly. Radiographs were obtained using a digitalized image system, which allowed a computerized bi-dimensional measurement by a specially developed Auto-CAD program. 12 healthy and active patients (6 crosslinke – 6 conevtional UHMWPE) have been selected for measurement.

Results: No macroscopic signs of loosening, mobilization and osteolysis were detected. Despite an increased wear rate for the conventional insert, no statistically sig-nificant differences of the linear wear were detected at five years for the two groups.

Conclusions: Longer follow-up and larger case studies are needed for more definitive conclusions. Nevertheless, this preliminary study shows that crosslinked polyethylene in vivo at 5 years does not give early failures and that its linear wear in the short term does not differ from that of a conventional polyethylene. Several other factors, such as the number and dimension of the debris, which are not detected by roentgenographic measurements, might be taken into consideration. Moreover it has been hypothesized for the crosslinked polyethylene an early plastic deformation, with consequent penetration of the head without wearing, which could affect the measurement on plan radiographs. Despite these limitations, roentgenographic measurements are quick and easy to perform, and therefore might be useful for the clinical practice of the periodical evaluation of the implants.

Introduction: Packaging of Muscolo-Skeletal Tissues (MST) stored at −80°C must assure safety and sterility in order to minimize any risk of bacterial contamination and/or mechanical failure. Polymeric bags demonstrated problem of integrity at −80°C; gamma ray sterilisation induce oxidation decreasing mechanical properties, whereas Ethylene Oxide (EtO) does not. Antioxidant biocompatible additive, as Vitamin E, could improve mechanical resistance.

Objectives: Based on a previous paper presented at EATB 2005 congress, to analyse mechanico-chemical properties of plastic bags routinely used in MST Banks and new samples in order to identify and solve possible problems arising from the chemical composition and/or sterilisation.

Materials and Methods: Five different polymeric sterile bags used in three International Banks (three gamma and two EtO sterilised) and four experimental sample, manufactured on purpose from a Linear Low Density PolyEthylene (LLDPE) 150 microns thick films (EtO and e-beam sterilised), two added of Vitamin E, were analysed. Impact resistance was evaluated both on frozen and unfrozen material (in oven at 37°C); results were related to chemical composition, Tg, sterilisation and Fourier Transformed InfraRed Spectroscopy (FTIR).

Results: Three samples routinely used (one gamma and one EtO) showed severe macroscopic modification (glassy behaviour) at frozen temperature with no resistance to any mechanical stress Two samples (EtO) did not resist to mechanical tests at frozen state. The four experimental LLDPE, EtO and e-beam sterilised, resisted to mechanical tests. FTIR analysis confirmed the chemical composition declared by the commercial film: pure LLDPE, without any toxic additive and LLDPE with vitamin E.

Discussion: Packaging must use polymers with adeguate glass transition temperature (Tg) in order to maintain at −80° the rubbery state, not stiff nor fragile (not to pass to glassy state). High energy radiation oxidize polymer and decrease their mechanical resistance. LLDPE combine low Tg of the amorphous phase and low crystallinity, resulting in good mechanical properties at working temperature and at −80°C. Addition of Vitamin E protect against oxidation. EtO sterilisation does not modify the structure.

Conclusion: A LLDPE added of Vitamin E, sterilised by EtO and e-beam could improved packaging and storage of tissues at −80°C, with increased resistance to oxidation.

Aims: In recent years, radiation crosslinking has become an important processing step in the manufacture of ultra-high molecular weight polyethylene (PE) components of joint replacement prostheses due to its associated high wear resistance. Gamma or electron beam radiation treatment is usually followed by a heating step, either complete melting or annealing of PE close to but below the melting temperature for a specific time duration. The heat treatment is performed to decrease free radical concentration within the crystalline lamellae in order to make PE more oxidation resistant.

In this study, we hypothesized that high pressure processing of PE would be advantageous if it is performed only after irradiation and quenching of free radicals and that it would be detrimental if it preceded irradiation. We used accelerated oxidation, mechanical tests and wear tests to show

Methods: Ram-extruded rod stock of GUR 1050 PE (Ticona, Bayport, TX) was purchased from MediTECH Medical Polymers (Fort Wayne, IN) and machined into cylinders to snugly fit into a custom-built high-pressure cell. A Carver hydraulic press was used to apply a pressure of 500MPa to PE specimens preheated to various temperatures, slow cooled to room temperature followed by pressure release. The PE cylinders and untreated control PE were subjected to 50kGy gamma radiation, which is a dose sufficient for a high degree of crosslinking in PE. A Parr bomb reactor filled with oxygen gas and operating at 5atm pressure and 70_C temperature was used to oxidize PE for a period of 14 days, according to ASTM standard F2003–02, and later characterized using Fourier Transform Infrared Spectroscopy (FTIR). A second batch of PE was first irradiated, melted and then subjected to high pressure processing. ASTM standard tensile tests were conducted to determine whether there was any increase in mechanical properties. Scanning electron microscopy (SEM) and differential scanning calorimeter (DSC) were used to characterize the lamellar morphology.

Results: The morphological characterization techniques, SEM and DSC, showed that high pressure processing increased the crystallinity as well as lamellar thickness regardless of whether the process was conducted prior to or after irradiation. FTIR showed that there was a monotonic increase in oxidation with lamellar thickness if the irradiation was carried out after high pressure processing. Several mechanical properties such as modulus and yield stress of PE increased with increase in crystallinity, which is desirable for applications where PE is subjected to high stresses.

Conclusions: High-pressure processing benefits the mechanical properties of crosslinked PE when it is conducted after irradiation and melting. However, if it conducted prior to irradiation and is not followed by thermal treatment, it can lead to more trapped free radical and excessive oxidation. Therefore, it is important to employ this processing method after irradiation so that it improves the mechanical properties of crosslinked PE.

During the last 15 years we have had the opportunity of analysing more than 700 UHMWPE prosthetic components (hip, knee and shoulder). Among them, about 500 were retrieved during revision surgery, while the remaining were new, ready-to implant, variably shelf-aged samples. The analysis of such a large, representative sample provided several important insights into the variables which influence the behaviour of UHMWPE in vivo; moreover, a long period of observation gave us the opportunity to follow changes and improvements in the field over time. All samples dated back to the nineties or before and sterilized with high energy radiation, either shelf-aged or retrieved, showed variable, but generally high, oxidation levels. Starting from the observation of these samples and with the aid of specimens irradiated on purpose under controlled conditions, some improvement has been achieved in the knowledge of radiation-induced oxidation process. The importance of the determination of hydroperoxides on the oxidation potential has been highlighted and the influence of variables such as sterilisation atmosphere, packaging, temperature and dose rate on the oxidation process has been clarified. The need for a suitable stabilizer to minimize oxidation arises during these studies.

We also had the opportunity of analysing a large number of EtO-sterilised samples, both new and retrieved. A small amount of them, all manufactured in the nineties, showed some bulk-oxidation which has been related to the presence of calcium stearate into the pristine resin. None of the newly produced, calcium stearate-free samples showed any oxidation and this group allowed to explore the behaviour of undegraded UHMWPE in vivo and in the shelf. Diffusion of polar compounds from the synovial fluid into polyethylene was observed in the majority of the retrieved samples. The nature of these products have been investigated along with their possible influence on the mechanical properties of the polymer.

In the last five years, we had the opportunity to study a significant number of crosslinked polyethylenes, both new and retrieved. The results of this study indicate that the variables of the crosslinking process can greatly influence final material properties and that not all cross-linked polyethylenes are the same.

Aims: To understand why during routine analyses of the physico-chemical properties of retrieved UHMWPE prosthetic components (Pes), it was noticed that some cups, which were directly in contact with bone, evidence a material loss in correspondence with the area adjacent to bone.

Methods: PEs retrieved during revision surgery and stored in formalin prior to observation, have been analysed by Fourier Transform InfraRed (FTIR) spectroscopy and Scanning Electron Microscopy (SEM).

Results: The results of the FTIR analyses did not display appreciable differences compared to those of the majority of the retrieved prostheses. Oxidation of UHMWPE was detected, but it is known to be due to sterilisation with high energy radiation in air, under uncontrolled conditions.

The SEM analyses indicated that the PEs surface which was directly in contact with bone shows an anomalous degradation. The surface looks as it has been corroded or “bitten” and its morphology is significantly different from that of surfaces abraded either in vivo or in vitro.

Conclusions: The results so far obtained seem to indicate that the surfaces, which have been in contact with bone during the implant time, undergo a selective biodegradation process, facilitated by gamma in air sterilisation, and influenced by the biological reactivity of the patient (such as osteclast activation).

Aims: to investigate the mechanical properties of a new nanocomposite bone cement radiopacified with Barium Sulfate (BaSu) nanoparticles added at different concentrations, compared to a control cement with the classical BaSu microparticles.

Methods: the starting material was Endurance (J& J/ DePuy, USA) bone cement without BaSu; the radi-opacifier particles have been mixed into the cement powder in several different concentrations of 5, 10, 20, 30, 40% of the weight respectively. Two groups were studied: controls, with classical medical grade BaSu particles (average size 1000 nm) and nanocomposites, with nanoparticles (av. size 100 nm). In accordance with the ASTM, an Instron 4201 machine tested a minimum of 6 specimens for each concentration. Tensile tests were performed at cross-head speeds of 1mm/sec, while compression tests were performed at 25,4 mm/sec. Results were statistically analysed.

Results: nanocomposites had higher compressive Yield strength in all groups except 30 and 40% and lower compressive Modulus in all but 5% group (no significant difference). Nanocomposites had higher tensile values in 5%, 10%, and 40% concentrations for Strain-to-failure, yield stress, and Work-of-Fracture, and no significant differences in the other concentrations. Tensile modulus had not statistically significant variations. Higher BaSu concentrations give increases in tensile modulus and decreases in the other tensile properties for both the groups. The nanocomposite outperformed the control in the 5, 10, and 20% groups, while the 30 and 40% groups had no significant differences; all the results were above ASTM requirements.

Conclusions: bone cement has several uses, like joint replacement, filling defects in tumour or revision surgery, and more recently vertebroplasty. These applications require different properties and would have benefits from the possibility to change viscosity, radiopacity, time of polymerisation, mechanical features. Previous studies have demonstrated the improved performances of the new nanocomposite cement at the clinical used concentration of 10%. This study investigated the possibility to augment the concentration of BaSu and therefore the radiopacity and their relative effect on the mechanical properties; the results demonstrated the good compliance of the nanoparticles cement in this field. This would be useful in particular for specific applications such vertebroplasty. Further studies are needed to investigate and determine the ideal fatigue, handling and mixing properties, viscosity and radiopacity.

Introduction: At the 2nd Orthopaedic Clinic of Turin the subcutaneous rupture of the Achillis tendon is treated with the Ma-Grifþth technique, followed by cast for eight weeks, weight bearing is possible after 2 months. Aim of this work is to evaluate 61 patients operated. Materials and methods: 61 patients were evaluated, divided into 2 groups: group A) 20 male patients treated from 1991 to 1996, mean age 37 years, follow-up 3,3 years, in the 1997 they had a clinical, echosonographic and isokinetic evaluation. Group B) 41 patients, 4 female, treated from 1997 to may 2002, mean age 37,5, mean follow-up 3,6 years, in the 2002 they were clinically evaluated. Results: Group A): the ecographic analysis revealed the thickening of the operated tendon, the isokinetich analysis revealed the same range of movement of the not-affected side, without lack of strength. Group A and B): at the clinical evaluation a normal walking and all the patients came back to the athletic activities in 5 months.

The 5% of the cases presented cicatricial adhaesions, the 10% of the cases presented a light hypoesthesia of the sural nerve. Only one rupture occurred after the re-beginning of the sport activity. Conclusion: This technique has several vantages, like the mini-invasivity, the rapidity of esecution and a low rate of severe complications and gave us good results, therefore we think that could be indicated in the non agonistic patient.