Introduction. Fretting crevice-corrosion (tribocorrosion) of metallic biomaterials is a major concern in orthopedic, spinal, dental and cardiovascular devices. 1. Stainless steel (i.e., 316L SS) is one alloy that sees extensive use in applications where fretting, crevices and corrosion may be present. While fretting-corrosion of this alloy has been somewhat studied, the concept of fretting-initiating crevice corrosion (FICC), where an initial fretting corrosion process leads to ongoing crevice-corrosion without continued fretting, is less understood. This study investigated the susceptibility of 316L SS to FICC and the role of applied potential on the process. The hypothesis is crevice-corrosion can be induced in 316L SS at potentials well below the pitting potential. Materials and Methods. A pin-on-disk fretting test system similar to that of Swaminathan et al. 2. was employed. Disks were ∼35 mm in diameter and the pin area was ∼500 mm. Samples were polished to 600 mm finish, cleaned with ethanol and distilled water. An Ag/AgCl wire as the reference, a carbon counter electrode and phosphate buffered saline (PBS, pH 7.4, Room T) were used for electrochemical testing. Load was controlled with a dead-weight system, monitored with a six-axis load cell (ATI Inc.). Interfacial motion was captured with a non-contact eddy current sensor (0.5 mm accuracy). Motion and load data acquisition was performed with Labview (National Instruments). Samples were loaded to ∼2 N. The potential per tests was increased from −250 to 250 mV (50 mV increments) with new locations and pins used in each repeat (n=3). Testing incorporated a 1 min rest before fretting (5 min, 1.25 Hz, 60 mm displacement saw tooth pattern). Fretting ceased and the load was held while currents were captured for another 5 min to assess ongoing crevice corrosion. Results. Testing showed that crevice corrosion can be initiated within minutes of fretting (or in a few cycles depending on potential; Fig. 1). Potentials as low as −100 mV showed evidence of corrosion, while sustained crevice corrosion was seen at −50 mV. As the potential increased above −50 mV, susceptibility to FICC increased. Fig. 2 is a typical cyclic polarization curve for 316L SS in PBS without fretting. Pitting starts at 400 mV vs Ag/AgCl, and the protection potential in this case is around potentials where FICC can be induced. Discussion. This study showed that 316L SS is prone to FICC starting at −100 mV and the severity of the crevice-corrosion damage depends on the applied potential (Fig. 3). Current after cessation of fretting takes longer to return to baseline or does not return indicating ongoing corrosion without fretting (Fig. 1). If the pin and disk are separated, the crevice-corrosion process stops immediately. The region immediately outside the fretting contact was crevice-like with a very small separation distance between the pin and disk surface which allowed crevice corrosion to develop (Fig. 3). Conclusion. 316L SS can undergo FICC at potentials close to normal physiological electrode potential conditions. Few fretting cycles are required to develop conditions for continued crevice-corrosion. Higher potentials increased the susceptibility of FICC in 316L SS

Objectives. Screw plugs have been reported to increase the fatigue strength of stainless steel locking plates. The objective of this study was to examine and compare this effect between stainless steel and titanium locking plates. Methods. Custom-designed locking plates with identical structures were fabricated from stainless steel and a titanium alloy. Three types of plates were compared: type I unplugged plates; type II plugged plates with a 4 Nm torque; and type III plugged plates with a 12 Nm torque. The stiffness, yield strength, and fatigue strength of the plates were investigated through a four-point bending test. Failure analyses were performed subsequently. Results. For stainless steel, type II and type III plates had significantly higher fatigue strength than type I plates. For titanium, there were no significant differences between the fatigue strengths of the three types of plates. Failure analyses showed local plastic deformations at the threads of screw plugs in type II and type III stainless steel plates but not in titanium plates. Conclusion. The screw plugs could increase the fatigue strength of stainless steel plates but not of titanium plates. Therefore, leaving screw holes open around fracture sites is recommended in titanium plates. Cite this article: L-W. Hung, C-K. Chao, J-R. Huang, J. Lin. Screw head plugs increase the fatigue strength of stainless steel, but not of titanium, locking plates. Bone Joint Res 2018;7:629–635. DOI: 10.1302/2046-3758.712.BJR-2018-0083.R1

Background. Intramedullary nailing is a widely accepted treatment method for femoral fractures. Failure of locking screws is often a threatening complication, particularly on comminuted fractures. For comminuted fractures, the locking nails are load-bearing devices. The load transfer between fractured fragments is made through especially the locking screws for these load bearing situations. Nonunion, malunion, delayed union, shortening, and nail migration are the expected results if early failure of locking screws is present with comminuted fractures. In this study our aim was to compare the bending resistance of titanium and stainless steel locking screws. Methods. We tested 60 locking screws in six groups (titanium, stainless steel, unthreaded, low threaded and high threaded) in a steel tube that has 30 mm inner diameter, which imitates the lesser trochanter level. We determined the yield points at three-point bending tests that permanent deformation started in the locking screws using an axial compression testing machine. Results. The three-point bending resistance of 5 mm low threaded titanium locking screws (bending at 1413 N loading) was 46.5 % less than the three-point bending resistance of 5 mm low threaded stainless steel locking screws (bending at 2171 N loading) (p < 0.001). Five mm stainless steel locking screws are 29–57 % more resistant to three-point bending deformation than titanium ones. Conclusions. Therefore, stainless steel locking screws instead of titanium ones must be preferred in comminuted femur shaft fractures. In intramedullary nailing of comminuted or long oblique femur fractures, a locking screw should be 5 mm low threaded or unthreaded stainless steel or 5 mm unthreadedtitanium. Five mm high threaded titanium or stainless steel screws must not ever be used as a locking screw. Level of Evidence. 5. Disclosure. Authors declare that there is no conflict of interest related to the present study

Introduction/Aims. The Exeter Stem can be used with metal femoral head that are made of either cobalt chrome, or stainless steel. The aim of this study was to compare the rates of revision of these two metal femoral head types when used with this femoral component. Method. Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) Data from September 1999 until December 2015 for all primary THRs using an Exeter or an Exeter v40 stem with the diagnosis of osteoarthritis were analysed. Only bearing couples that used a metal head with polyethylene were included. The cumulative percent revision (CPR) calculated using Kaplan-Meier estimates were compared for the two metal head types. CPR were further analysed by age, polyethylene type and head size. Reasons for revision and types of revision were assessed. Results. There were 51666 THR that used Exeter or Exeter v40 stems of which 12554 had femoral heads made of cobalt chrome and 39112 had heads made of stainless steel. There was no difference in the rate of revision overall when head types were compared. There was also no difference in CPR between the two head types with age. Hips that used cobalt chrome heads had a higher CPR than stainless steel heads when these were used against non-crosslinked polyethylene. When heads with a diameter of 32mm or greater were compared, those made of cobalt chrome had a higher rate of revision than stainless steel HR 1.38 (1.15, 1.66) P<0.001). Conclusion. There was no difference comparing cobalt chrome or stainless-steel heads, except where non-crosslinked polyethylene was used, or where the heads size was 32mm or greater. In these comparisons, heads made from cobalt chrome had a higher rate of revision

Relatively high rates of fracture of the femoral stem of total hip replacements were seen with early designs manufactured with stainless steel. Improvements in metallurgy, alloy chemistry, materials and stem design have led to a reduction in the incidence of this complication and the occurrence of fracture with modern femoral stems is a now a rare event. However, the implantation of modern stems into heavy patients and the use of higher offset stems leads to considerable testing of the mechanical capabilities of some stem designs. We present ten cases of fracture of modern stainless steel polished tapered stems. The fractures occur either in the neck, or in the distal half of the stem. Our clinical data suggests that heavy patients with small stems and high offsets are at risk of breaking their implants. Varus positioning of the stem in a number of cases further increases the bending moment of the stems, and the sacrifice of cement mantle thickness for implant size within narrow medullary canals may lead to the loss of proximal support. Failure analysis of the retrieved high nitrogen stainless stems also suggests there may be metallurgical factors that contribute to their failure. On the basis of our findings, careful consideration is required when using high offset stainless steel stems in large patients

Objectives: The purpose of this biomechanical study was to compare the mechanical properties of locked nails and screws made from either stainless steel or titanium alloy. Methods: The specially designed locked nails and screws with the same structures were made from either stainless steel or titanium alloy. The structural factors investigated included inner diameter and root radius for locking screws and outer diameter and nail hole size for locked nails. The mechanical properties investigated included bending stiffness, strength, and fatigue life. Finite element models were used to simulate the mechanical tests and compute the stress concentration factors. Results: Increasing the root radius and the inner diameter could effectively increase the fatigue strength of the locking screws. Fatigue strength increased more in titanium than in stainless steel screws, especially when the inner diameter was increased. In contrast, the titanium locked nails were much weaker than their stainless steel counterparts. Finite element models could closely predict the results of the biomechanical tests with a correlation coefficient that ranged from −0.58 to −0.84 for screws and was −0.98 for nails. The stress concentration factors ranged from 1 to 1.81 for screws and from 3.06 to 4.17 for nails. Conclusions: With larger root radius and inner diameter, titanium locking screws could provide much stronger fatigue strength than stainless steel counterparts. However, titanium locked nails might lose their advantages of superior mechanical strength because of high notch sensitivity and this limitation should be a critical concern clinically. Finite element analyses could be reliably used in research and development of locked nails and locking screws

A report published in 1999 showed that whether stainless steel or titanium screws were used in spinal surgery made little difference to outcome. However, the smaller number of titanium group patients, who had a shorter follow-up period, skewed statistical analysis in the study. The present study re-evaluates the incidence of complications, especially the pseudarthrosis rate, in a series of patients who underwent lumbosacral fusion with a segmental spinal correction system fixation device. Of over 1 100 patients who underwent surgery between July 1993 and December 2000, 846 could be followed up adequately. Stainless steel devices were used in 410 and titanium implants in 436. There were roughly equal numbers of male and female patients, and occupation and smoking profiles were similar. The incidence of pseudarthrosis was equal and the incidence of screw breakage was less than 1% in both groups

Background: Paediatric spinal systems made from stainless steel are effective at correcting early onset scoliosis in a non-fusion technique. The use of similar systems manufactured from titanium is an attractive alternative as it would allow Magnetic Resonance Imaging of the patient with its recognised imaging advantages. Objective: We performed a prospective in vitro study to compare the mechanical performance of a current clinically used stainless steel construct with an identical proposed titanium alternative. Methods: Twelve spinal constructs of each material were constructed in a typical in vivo configuration using a corpectomy model in accordance with ASTM F1798 standard. Five samples for each metal were subjected to axial compressive static loading at a rate of 1mm/s until plastically deformed. Seven samples for each metal were then subject to varying compressive cyclic loads until a 5 million cycle run out was observed. From this data a fatigue S-N curve was generated. Results: The stiffness of each construct was then calculated and the results were statistically analysed. For steel and titanium we calculated 95% confidence intervals of 23.9 to 35.7 and 18.8 to 23.7 respectfully. Significance P(< 0.05). The fatigue strength to 5 million cycles was 179N and 150N for steel and titanium respectfully. Failure occured most commonly in the rods close to the transverse rod connector or the pedicle screw / polyethylene block interface. Conclusions: We conclude that with identical dimensions, the stainless steel constructs had a significantly higher Modulus of Elasticity than titanium. The fatigue strength for steel was also higher than titanium. The potential use of titanium as an alternative to stainless steel in paediatric spinal systems is still an attractive alternative. Given the results, we would suggest that further re-designing and testing be carried out before clinical release and then initially be reserved for selected patients with lower body weight or physical demands

Introduction and Aims: Zirconia heads were introduced into hip replacement surgery with in vitro reports of lower wear on polyethylene compared with metal. Over 400,000 zirconia heads have been implanted worldwide and yet clinical studies have varied in their results. The aim of this study was to compare the radiological wear rate of zirconia and stainless steel heads on polyethylene. Method: Between March 1998 and August 2001, 186 patients having a hip replacement by one of the two authors were entered into a randomised trial to receive either a 26mm stainless steel head, a 28mm stainless steel head or a 28mm zirconia head. In all patients a posterior approach and a cemented Exeter femoral stem were used. One surgeon used a cementless cup in patients under 65. All other patients received an all-polyethylene cemented cup. An upper age limit of 75 was chosen to hopefully allow at least 10 years follow-up. The penetration of the heads into the polyethylene was then assessed by the modified Livermore technique. Results: Sixty-seven hips were randomised to receive a 26mm metal head, 58 a 28mm metal head and 61 a 28mm ‘HIPed’ zirconia head. The average radiological follow-up was 48 months. The penetration rate on the all-polyethylene cup for the 26mm metal head was 0.06mm/yr. This was equivalent to a previous study using the same components. This compared with a penetration rate of the 28mm metal head of 0.07mm/yr and the 28mm zirconia head of 0.13mm/yr. There was considerable variation in the latter, which is consistent with the theory that some zirconia heads may undergo phase transformation that in turn increases the surface roughness. Conclusion: Although we have only a short follow-up, this study already shows a statistically significant difference in the penetration rates produced by zirconia femoral heads on polyethylene when compared with stainless steel heads. This agrees with several other clinical studies, but to our knowledge is the first reported randomised trial

Introduction: Long bone fracture treatment with interlocking intramedullary nails is associated with long operative procedures, re-operations and long periods of infirmity. We assessed the clinical and economical factors associated with tibial fracture fixation with interlocking nails in comparison to fixation with an expandable stainless steel intramedullary nail. Methods: Eighty diaphysial tibial fractures were consecutively treated with either an interlocking intramedullary nail (n=53 patients) or an expandable nail (n=27 patients). Results: The duration of surgery was 139 minutes with interlocking nails and 52.9 minutes with expandable nails (p< 0.001). Re-hospitalization and re-operations were required in 51% and 42% of patients with interlocking nails respectively, compared to one patient (3%) with an expandable nail (p< 0.0001). Complications related to the introduction of interlocking screws (e.g., neurological deficits, screw breakage and delayed or non-union requiring dynamization) occurred in 19 interlocking nail patients and in none of the expandable nail patients. Union was achieved after 17.5 weeks (mean) with the interlocking nails compared to 11.5 weeks for expandable nails (p=0.071). The beneficial economic ramifications of using expandable nails were a 39% reduction in hospital expenses. Conclusions: The use of an expandable stainless steel intramedullary nail is associated with a substantial reduction in clinical complications and hospital costs. An expandable nail features a unique fixation modality, which has superior mechanical fixation strength and is better adapted to the physiological bone healing process. Based on these advantages, as well as its simplicity in use and short surgical technique, we recommend it for treatment of long bone fractures

Background: Tension Band wiring technique is commonly used to treat transverse patella fractures. The commonly used configuration has parallel K wires and a stainless steel wire loop oriented as a figure of 8. Use of non-metallic suture materials as reliable fixation materials have been reported. We investigated the properties of composite polyester suture (Fibre wire) when used in Tension band wiring of patella. Methods: A wooden model of a transversely fractured patella was used. The fracture was fixed using two K wires and a loop of horizontally oriented stainless steel wire or fibre wire. Two wire twists placed at corners were used for SS wire loops. For fibre wire samples a tensioning device was used and the knots placed at one corner. Interfragmentary compression at the point of wire breakage and fracture displacement on physiologic cyclic loading was measured for each fixation construct. The reliability of tensioning device (Arthrex) and the effect of using multiple strands of wire were assessed. Results: Use of the tensioning device produced interfragmentary compression that could be repeated reliably. The addition of a further strand increased the interfragmentary compression developed by 94%. There was no significant difference between interfragmentary compression developed between groups (p> 0.05). The average interfragmentary compression produced for three repetitions for the individual groups, Fibre wire (1394N), SS wire of 1.0mm diameter (1320N), SS Wire of 1.25mm diameter (1594N) were comparable. This increased significantly when a second loop of fibre wire was used (2566N). Permanent fracture displacement at physiologic loads were, Fibre wire (9.7mm, SD 2.7mm), SS wire of 1.0mm diameter (7.0mm, SD 1.0mm) and SS Wire of 1.25mm diameter (7.4mm, SD 2.3mm). The addition of the second strand of fibre wire decreased the displacement significantly (4.8mm, SD 0.6mm). The effect of second strand of fibre wire decreased the displacement by 97% while the decrease on addition of the second strand of stainless steel wire was only 14%. Discussion: Interfragmentary compression produced to failure was comparable between a single strand of fibre wire, 1.0mm SS wire and 1.25mm SS wire, the commonly used SS wire diameters in fixation of fractured patella. The standard deviations of final permanent displacement were higher with the larger diameter of SS wire, indicating that the use of a thicker wire would require some preloading before it is uniformly tensioned. Amongst the SS wire diameters tested, 1.0mm resulted in least variations (SD 1.0mm). The addition of second strand resulted in a marked improvement in displacement with Fibre wire and variations between different samples were smaller than in any other group tested (SD 0.6mm). Conclusions:. Fibre wire has similar strength to failure when compared the commonly used thickness of stainless steel wire for fixation of patella. Use of tensioning device produces interfragmentary compression in a reliable and reproducible manner. The addition of second loop of fibre wire, separately tensioned results in significant improvements in interfragmentary compression and resistance against displacement

Introduction. The most common treatment options for fixation of osteoporotic distal femur fractures are retrograde nails and locking plates. There are proponents of more elastic titanium plates as well as more rigid steel plates; No clear superiority of one over the other has been established. We aimed to evaluate the mechanical differences between stainless steel and titanium locking plates in the fixation of distal femur fractures in osteoporotic bone. We hypothesized that due to its higher elasticity titanium locking plates can absorb more energy and are therefore less likely to “cut” into the bone compared to stainless steel locking plates resulting in improved metaphyseal osteoporotic fracture fixation. Methods. We used eight matched pairs of osteoporotic fresh-frozen human cadaveric femurs (age >70 years, all female). Within each pair we randomized one femur to be fitted with a Less Invasive Stabilization System (LISS-Titanium locking plate) and one with a Distal Locking Condylar Plate (DLCP-Stainless steel locking plate). A fracture model simulating an AO 33-A3 fracture was created (extraarticular comminuted fracture) and specimens were subsequently subjected to step-wise cyclic axial loading to failure. We used an advanced three dimensional tracking system (Polhemus Fastrak) to monitor the movement of the distal fragment relative to the real time distal plate position allowing us to evaluate distal implant cut-out. Results. During cyclic testing, seven of the eight pairs of matched femurs, the DLCP failed before the LISS plate (p=0.03). All constructs were able to withstand cyclical loading up to 800N. The overall plastic deformation as measured by the displacement of the Instron crosshead experienced by the titanium plate constructs was significantly lower compared to the stainless steel plate construct: The plastic deformation of the LISS plates was 39% lower compared to the Locking Condylar plates after cycle testing at 400 Newtons and 70% lower at 800N. Furthermore during the 800N cycle testing the LISS plating system showed a significantly lower rate of plastic deformation not only for the entire bone-implant construct, but also between the plate and the distal fragment than the locking condylar plate (=less distal implant cut-out). Conclusions. The use of a more advanced three dimensional tracking system, fresh-frozen osteoporotic matched human specimen and the ability to test all constructs to failure allowed us a more thorough comparison of titanium versus stainless steel implants compared to previous studies. The titanium locking plates provided an overall superior fixation of osteoporotic distal femur fractures with less distal implant cut-out, a better elastic recoil, and a slower rate of residual plastic deformation

Background. Currently, stailess steel, titanium and carbon-fiber reinforced polyetheretherketone (CF-PEEK) plates are available for the treatment of distal radius fractures. Since the possibility to create a less rigid fixation may represent an advantage in case of ostheoporotic or poor quality bone, the aim of this study is to compare the biomechanical properties of these three materials in terms of bending stiffness with a single static load and after cyclical loading, simulating physiologic wrist motion. Materials and Methods. Three volar plating systems with fixed angle were tested: Zimmer stainless steel volar lateral column (Warsaw, IN); Hand Innovations titanium DVR (Miami, FL); Lima Corporate CF-PEEK DiPHOS-RM (San Daniele Del Friuli, Udine, Italy). For each type of plate tested four right synthetic composite bone radii were used. An unstable, extraarticular fracture was simulated by making an 8 mm gap with a saw starting 12 mm proximal to the articular surface of the radius on the distal radio-ulnar joint side. The osteotomies were made perpendicular to the long axis of the bone to allow for a consistent fracture gap on the dorsal and volar sides of the radius. Plates were implanted using all the distal and proximal fixation holes [Fig. 1]. Each synthetic radius model was potted in methylmethacrylate and tested in a bi-axial servo-hydraulic test frame (MTS Minibionix 858, universal testing machine) for load to failure by advancing a cobalt chrome sphere centered over the articular surface at a constant rate of displacement of 5 mm/min. The sphere was advanced until the construct failed or the dorsal edges of the fracture met. The resultant force was defined as bending stiffness pre fatigue. Three constructs for each plate were then dynamically loaded for 6000 cycles of fatigue at a frequency of 10Hz, with a load value corresponding to the 50% of the previously calculated bending strength. Finally, the constructs were loaded to failure, measuring the bending stiffness post fatigue. Results. All fracture constructs survived all phases of the cyclic loading testing. The mean bending stiffness pre fatigue was higher for the Zimmer plate (155.23±1.91 N/mm), in comparison to Hand Innovations (138.67±4.72 N/mm), and DiPHOS-RM (124.75±3.60 N/mm) [Fig. 2]. After cyclic loading, stiffness increased significantly of a mean 24% for the Zimmer plate (190.42±4.33 N/mm); 33% for the Hand Innovations (186.57±1.71 N/mm); and 18% for the DiPHOS-RM (146.28±1.52 N/mm) [Fig. 2–3]. Conclusions. CF-PEEK plate is less stiff than stainless steel and titanium plates, with an elastic modulus more similar to bone as well as the ability to withstand prolonged fatigue strain. From these preliminary data it might be assumed that the CF-PEEK plates could provide a sufficiently stable osteosynthesis, flexible enough to unload the implant-bone interface, minimising peak stresses at the bone- implant interface, making them particularly suitable for fracture fixation in osteoporotic patients. A proper patient selection (avoiding incompliant or non collaborative) should be performed using CF-PEEK plates to avoid possible implant breakage consequent to a fall or a second trauma on the injuried wrist until the complete fracture healing. For any figures or tables, please contact authors directly (see Info & Metrics tab above).

Introduction: Biomaterial implants in the human body constitute passive surfaces that are prone to bacterial adhesion as the on-set of biomaterials-associated infection. Antibiotic treatment of infected biomaterial implants is little successful clinically, because the biofilm-mode of growth protects the adhering organisms. Percutaneous implants, such as bone screws used in orthopedics or dental implants, constitute a special class of implants with infection rates exceeding the infection rate of deep body implants by far. Especially fixation frames, used in orthopedic surgery for the treatment of complicated fractures, inevitably become infected during the course of a treatment. The aim of this study is to determine whether it is possible to stimulate bacterial detachment from surgical stainless steel and decrease the viability of the remaining adhering bacteria using block currents. Method: Bacteria were allowed to adhere from a flowing suspension of high ionic strength in a parallel plate flow chamber, after which the suspension was replaced by a bacterium free solution with 10 mM potassium phosphate buffer. Block currents of 15, 60 and 100 ìA with different frequencies (0.1 to 2 Hz) and duty cycles (5 to 50%) were applied to induce bacterial detachment. Results: Initial detachment rate increased with increasing frequency and duty cycle, namely from 0 to 3700 cm. −2. s. −1. The total detachment percentage for block currents of 100 ìA with 25% to 50% duty cycle and frequencies as of 0.5 Hz are similar for all conditions. The detachment percentage in this range amounts on average 76%, whereas DC currents around 100 ìA have an average of 60%, which was found to be significant lower (p=0.03). The killing capacity of these current series can be up to two log scales depending on the current. Conclusion: Current induced detachment of Staphylococcus epidermidis from surgical stainless steel seems very effective, especially for a 100 ìA, 50% duty cycle and 2 Hz block current. The viability of the remaining adhering bacteria decreased with 2 log scales. Clinically this could mean another way of preventing and curing pin tract infection

Introduction: There are more than 60 different hip prostheses currently available for total hip replacement (THR). Cemented prostheses make up about 90 to 95% of current total UK market. The cost of THR prosthesis varies widely with some prostheses cost 5 times more than others. Furlong Stainless steel cemented is a low-cost prosthesis that has been used in few hospitals in UK and Europe. There is no published data to report its survival and performance. Aim: To evaluate the outcome of a low-cost THR prosthesis (Furlong stainless steel) that has been in use in our hospital since 1993. Patients and Methods: we retrospectively reviewed 142 THR performed between 1993 and 2001. The average age was 72 and osteoarthritis was the primary pathology in 92%. Operations were performed by different grades of surgeons. 25 patients were dead at the time of the study. Results: 4 cases underwent revision (2.8%) with survival rate of 97.2%. 6 cases of dislocation, 17 cases of heterotopic calcifications, 5 cases of DVT and one neurological injury. 88% reported no pain and 79.6% were satisfied. Conclusions: The results of this study compare favourably with Furlong Titanium cemented prosthesis and other popular THR prostheses (e.g. Charnley). It is rational to continue using this prosthesis, which appears to be cost effective

Movement between an implant surface and overlying soft tissue gives rise to fibrous capsule formation with a liquid filled void. Clinically, this situation is more prevalent with electropolished stainless steel (EPSS) implants compared to commercially pure titanium (CpTi) implants. We hypothesise this is mainly due to lack of microtopography on the EPSS. Four experimental EPSS surfaces with varying microtopographies were selected by a combination of morphological analysis using the scanning electron microscope and quantitative roughness analysis using laser profilometry. Standard treated EPSS (ISO 5832/1) and CpTi (ISO 5832/2) surfaces were also used. The plates had only one screw hole at either end so that the interaction of the tissue with an intact surface could be evaluated. Six plates of each type were implanted on both the left and right tibia, randomly, of 18 white New Zealand rabbits under the muscle for 12 weeks. After sacrifice samples underwent standard histological processing. Briefly, fixation, dehydration, embedding in methyl methacrylate, sectioning at 250μm slices (with implant), grinding to 50μm and staining with Giemsa. Digital images were taken with a light microscope and the size of thickening of connective tissue on the implant surface and the presence or absence of a liquid filled void was observed. Results showed no voids present on the CpTi samples. The standard EPSS had 3/6 plates with a void. The experimental EPSS surfaces were in-between these results. There was no relationship between quantitative measurements of average roughness (Ra) and the presence or absence of a void. There was a relationship between lack of fine microroughness of a surface (as seen with the SEM) and the presence of a void. The size of capsular thickening was not related to the Ra of the surface. These results support that void formation is mainly due to lack of microtopography on the plates

Summary Statement

Innovative nanocomposite carbon coating doped with Si can significantly improve the osseintegration of orthopaedics implants. Additionally, this kind of coating increases the mechanical resistance of the implants, what is especially important on case of joints (frictional pairs).

Cobalt chrome-on-cobalt chrome bearing surfaces have been re-introduced despite some concerns regarding potential risks posed by soluble metallic by-products. We have investigated whether there are metal-selective differences between the levels of genetic damage caused to a human cell line when cultured with synovial fluids retrieved from various designs of orthopaedic joint replacement prostheses at the time of revision arthroplasty.

Synovial fluids were retrieved from revision hip and knee arthroplasty patients with bearings made from cobalt chrome-on-cobalt chrome, cobalt chrome-on-polyethylene and stainless steel-on-polyethylene. Control synovial fluids were retrieved from primary arthroplasty cases with osteoarthritis. Synovial fluid was cultured with human primary fibroblasts for 48 hours in a cell culture system under standardised conditions. The “Comet” assay was used with an image analysis system to measure levels of DNA damage caused by the various synovial fluid samples.

Synovial fluids from cobalt chrome-on-cobalt chrome and cobalt chrome-on-polyethylene joint replacements both caused substantial levels of genetic damage as detected by the Comet assay. Synovial fluids retrieved from stainless steel-on-polyethylene joints caused low levels of damage. The difference between these groups was highly statistically significant (p< 0.001). Control synovial fluids from osteoarthritic joints caused minimal changes. Atomic absorption spectroscopy demonstrated that the metal-on-metal synovial fluids contained the highest levels of cobalt and chromium. Different alloys used in orthopaedic implants are associated with different levels of DNA damage to cultured human cells in vitro. We are able to demonstrate that this damage is attributable at least in part to the metal content of the synovial fluid samples. We have no evidence for any long-term health risk to patients with such implants.

Aims: To study the levels of genetic damage caused to a cultured human cell line when cultured with synovial ßuid retrieved from revision arthroplasty joints. Methods: Synovial ßuids were retrieved from revision hip and knee arthroplasty patients with bearings made from Cobalt chrome-on-Cobalt chrome, Cobalt chrome-on-polyethylene, Stainless Steel-on-polyethylene and Titanium-onpolyethylene. Control synovial ßuid was retrieved from primary arthroplasty cases. Synovial ßuid was cultured with human primary þbroblasts for 48 hours in a cell culture system under standardised conditions. The ÔCometñ assay was used with an image analysis system to measure levels of DNA damage caused by the various synovial ßu id samples. Results: Synovial ßuids from Cobalt Chrome-on-Cobalt Chrome and Cobalt Chrome-on-polyethylene joint replacements caused signiþcantly (p< 0.05) more genetic damage than synovial ßuids from Stainless Steel-on-polyethylene and Titanium-on-polyethylene cases. Control synovial ßuid caused minimal change. Conclusions: Different alloys used in Orthopaedic implants are associated with different levels of DNA damage to human cells in vitro. We have no evidence for any long-term health risk to patients with such implants. Further research is needed in this þeld.

Metal-on-metal joint replacements have been reintroduced despite some concerns regarding the potential risks posed by soluble metallic by-products. We have investigated whether there are metal selective differences between the levels of genetic damage caused to a human cell line when cultured with synovial fluids retrieved from orthopaedic joint replacement prostheses at the time of revision arthroplasty.

Methods: Synovial fluids were retrieved from revision hip and knee arthroplasty patients with bearings made from Cobalt chrome-on-Cobalt chrome, Cobalt chrome-on-polyethylene and Stainless Steel-on-polyethylene. Control synovial fluids were retrieved from primary arthroplasty cases with osteoarthritis and no implant in situ. Synovial fluid was cultured with human primary fibroblasts for 48 hours in a cell culture system under standardised conditions. The ‘Comet’ assay was used with an image analysis system to measure levels of DNA damage caused by the various synovial fluid samples. Metal levels were measured in the synovial fluid samples using atomic absorption spectroscopy.

Results: Synovial fluids from Cobalt Chrome-on-Cobalt Chrome and Cobalt Chrome-on-polyethylene joint replacements both caused substantial levels of genetic damage as detected by the Comet assay. Synovial fluids retrieved from Stainless Steel-on-polyethylene joints caused low levels of damage. The difference between these groups was highly statistically significant (p< 0.001). Control synovial fluids from osteoarthritic joints caused minimal changes. Atomic absorption spectroscopy demonstrated that the metal-on-metal synovial fluids contained substantially more cobalt and chromium than the fluids retrieved from cobalt chrome-on-polyethylene joints. Stainless steel-on-polyethylene synovial fluids contained the least metal.

Conclusions: Different alloys used in Orthopaedic implants are associated with different levels of DNA damage to cultured human cells in vitro. We are able to demonstrate that this damage is attributable at least in part to the metal content of the synovial fluid samples. We have no evidence for any long-term health risk to patients with such implants. Further research is needed in this field.