Abstract

Adverse reaction to metal debris (ARMD) is well recognised as a complication of large head metal on metal total hip replacement (THR) leading to pain, bone and tissue loss and the need for revision surgery. An emerging problem of trunnionosis in metal on polyethylene total hip replacements leading to ARMD has been reported in a few cases. Increased metal ion levels have been reported in THR's with a titanium stem and a cobalt chrome head such as the Accolade-Trident THR (Stryker). We present 3 cases of ARMD with Accloade-Trident THR's with 36mm cobalt chrome head and a polyethylene liner. Metal ion levels were elevated in all three patients (cobalt 10.3 – 161nmol/l). Intraoperative tissue samples were negative for infection and inflammatory markers were normal. Abnormal fluid collections were seen in all three cases and bone loss was severe in one patient leading to a proximal femoral replacement. Histology demonstrated either a non-specific inflammatory reaction in a case which presented early or a granulomatous reaction in a more advanced case suggesting a local foreign body reaction. All patients had improved symptoms post-operatively. 1 patient who had staged bilateral Accolade-Trident THR's required revision of both THR's. ARMD in metal on polyethylene THR's with a titanium stem represents a potential emerging problem. Further studies are required to assess whether these occurrences are rare or represent the tip of an iceberg

Introduction. The National Joint Registry has recently identified failure of large head metal on metal hip replacements. This failure is associated with the high torque at the interface of standard modular taper junction leading to fretting and corrosion. A number of manufacturers produce mini spigots, which in theory, provide a greater range of motion as the neck head junction is reduced. However, the relative torque to interface ratio at this junction is also increased. In this study we investigated hypothesis that the use of small spigots (minispigots) will increase wear and corrosion on modular tapers. Methods. Wear and corrosion of spigots were compared in-vitro when loaded with a force representative of the resultant force passing through the hip. The heads (female tapers) were made of cobalt-chrome-molybdenum (CoCrMo) and the stems (male tapers) of titanium alloy (Ti). Commercially available tapers and heads were used. The surface parameters & profiles were measured before & after testing. Electrochemical static and dynamic corrosion (pitting) tests were performed on minispigots under loaded and non-loaded conditions. Results. Post-testing the surface parameters Ra, Ry & Rz on the head taper associated with the minispigots had become greater compared with standard spigots. In all instances the profile of the titanium male tapers was unchanged. SEM showed the corroded region of the head was similar to the profile on the Ti male taper, with evidence of pitting in the cobalt chrome. In the CoCrMo/ Ti combinations, wear and corrosion were increased in minispigots compared with standard spigots. On minispigots the rough surface finishes were affected more severely than those with a smoother surface. Static corrosion tests showed evidence of fretting in the rough but not the smooth minispigots. Pitting scans showed a greater hysteresis with the rough surface finishes on the minispogot indicating potentially greater corrosion in the former. Conclusion. The relative size of the taper in comparison to the head combined with the surface finish was crucial. As the relative torque to interface ratio at this junction increased corrosion of the cobalt chrome head increases and is further enhanced if the surface finish on the tapers is rough

Finger arthroplasty lacks the success seen with hip and knee joint replacements. The Van Straten Leuwen Poeschmann Metal (LPM) prosthesis was intended for the proximal interphalangeal (PIP) joints. However revision rates of 30% after 19 months were reported alongside massive osteolysis. Three failed LPM titanium niobium (TiNb) coated cobalt chrome (CoCr) components were obtained- two distal and one proximal. All three components were analysed using an environmental scanning electron microscope (ESEM). This gave the chemical composition of the surface to determine if the TiNb surface coating was still intact. The distal components were analysed using a ZYGO non-contact profilometer (1nm resolution) with the proximal component unable to be analysed due to its shape. ZYGO analysis gave the roughness average (Ra) of the surface and determined the presence of scratches, pitting and other damage. Images obtained from both the ZYGO and the ESEM indicated that the surfaces of all components were heavily worn. On the articulating surfaces of both distal components unidirectional scratching was dominant, while the non-articulating surface showed multidirectional scratching. The presence of unidirectional scratching suggested two-body wear, whilst the multidirectional scratching on the non-articulating surface of the distal component suggested that trapped debris may have caused three-body wear. The ESEM chemical analysis showed that in some regions on the distal component the TiNb coating had been removed completely and in other areas it had been scratched or penetrated. On the proximal component the TiNb coating had been almost completely removed from the articulating surfaces and was only present in small amounts on the non-articulating surfaces. There was little evidence of bone attachment to the titanium coating which was intended to help provide fixation. ESEM images showed the coating had been removed in some sections where there was minimal scratching, suggesting this scratching did not impact significantly in the coating removal. Therefore here the main cause of coating removal may have been corrosion, although scratching may have also have played a part. The osteolysis reported clinically may have been linked to the wear debris from the failed coating

Although bovine serum is the lubricant recommended by several international standards for the wear testing of orthopedic biomaterials there are issues over its use. The inherent batch variation in protein content means that two bovine serum lubricants can give different wear rates. Due to degradation, the lubricant needs to be changed regularly, so that any third body wear particles are removed, thus potentially influencing wear regimes. There are also cost and safety issues with the use of bovine serum. For these reasons, alternative lubricants were investigated. A 50-station wear test rig was used, which applied multi-directional motion to each ultra-high molecular weight polyethylene (UHMWPE) test pin. Each pin articulated against a cobalt chrome plate polished to better than 0.05 microns Ra. The following lubricants were used: 50% dilute bovine serum; soy protein; olive oil; wheatgerm oil; soya oil; albumin and globulin (AG) mix; albumin, globulin and chondroitin sulphate (AGC) mix; whole milk; Channel Island milk; 11 mg/ml protein egg white; 20 mg/ml egg white; and 40 mg/ml egg white. A minimum of 6 UHMWPE pins per lubricant were wear tested and the tests ran to 2.5 million cycles. Gravimetric measurements were taken throughout the test to determine the volume of wear and at the end of the test the samples were examined using a SEM. The lubricants giving the closest results to bovine serum were 20 and 40 mg/ml egg white, with mean UHMWPE total wear volumes of 17.4 mm3 and 17.8 mm3 compared to bovine serum which gave 20.7 mm3. Surface topographies showed similar features too. The 11 mg/ml egg white lubricant and the AG and AGC lubricants were next closest in terms of wear. An UV absorbance assay found that all the protein based lubricants suffered from a high degradation rate, and the rate increased with increasing protein content. Egg white may offer a less expensive alternative to dilute bovine serum as a test lubricant although it is likely that it too would need to be changed as regularly as bovine serum

Objectives

Taper junctions between modular hip arthroplasty femoral heads and stems fail by wear or corrosion which can be caused by relative motion at their interface. Increasing the assembly force can reduce relative motion and corrosion but may also damage surrounding tissues. The purpose of this study was to determine the effects of increasing the impaction energy and the stiffness of the impactor tool on the stability of the taper junction and on the forces transmitted through the patient’s surrounding tissues.

Objectives

This study reports on a secondary exploratory analysis of the early clinical outcomes of a randomised clinical trial comparing robotic arm-assisted unicompartmental knee arthroplasty (UKA) for medial compartment osteoarthritis of the knee with manual UKA performed using traditional surgical jigs. This follows reporting of the primary outcomes of implant accuracy and gait analysis that showed significant advantages in the robotic arm-assisted group.

Objectives

The cytotoxicity induced by cobalt ions (Co²⁺) and cobalt nanoparticles (Co-NPs) which released following the insertion of a total hip prosthesis, has been reported. However, little is known about the underlying mechanisms. In this study, we investigate the toxic effect of Co²⁺ and Co-NPs on liver cells, and explain further the potential mechanisms.

Objectives

Rotator cuff tears are among the most frequent upper extremity injuries. Current treatment strategies do not address the poor quality of the muscle and tendon following chronic rotator cuff tears. Hypoxia-inducible factor-1 alpha (HIF-1α) is a transcription factor that activates many genes that are important in skeletal muscle regeneration. HIF-1α is inhibited under normal physiological conditions by the HIF prolyl 4-hydroxylases (PHDs). In this study, we used a pharmacological PHD inhibitor, GSK1120360A, to enhance the activity of HIF-1α following the repair of a chronic cuff tear, and measured muscle fibre contractility, fibrosis, gene expression, and enthesis mechanics.

Hip simulators have been used for ten years to determine the tribological performance of large-head metal-on-metal devices using traditional test conditions. However, the hip simulator protocols were originally developed to test metal-on-polyethylene devices. We have used patient activity data to develop a more physiologically relevant test protocol for metal-on-metal devices. This includes stop/start motion, a more appropriate walking frequency, and alternating kinetic and kinematic profiles.

There has been considerable discussion about the effect of heat treatments on the wear of metal-on-metal cobalt chromium molybdenum (CoCrMo) devices. Clinical studies have shown a higher rate of wear, levels of metal ions and rates of failure for the heat-treated metal compared to the as-cast metal CoCrMo devices. However, hip simulator studies in vitro under traditional testing conditions have thus far not been able to demonstrate a difference between the wear performance of these implants.

Using a physiologically relevant test protocol, we have shown that heat treatment of metal-on-metal CoCrMo devices adversely affects their wear performance and generates significantly higher wear rates and levels of metal ions than in as-cast metal implants.

Ciprofloxacin hydrochloride-loaded microspheres were prepared by a spray-drying method using pectin and chitosan. The effects of different polymers and drug ratios were investigated.

The most appropriate carriers were selected by in vitro testing. A rat methicillin-resistant Staphylococcus aureus osteomyelitis model was used to evaluate the effects of the loaded microspheres.

The drug was released rapidly from the pectin carrier but this was more sustained in the chitosan formulation.

Chitosan microspheres loaded with ciprofloxacin hydrochloride were more effective for the treatment of osteomyelitis than equivalent intramuscular antibiotics.