Introduction. Antibiotic loaded polymethyle methacrylate spacers are commonly used in the management of septic hip replacements. Aim. The aim of this study was to determine wear patterns on the articulating surfaces of these spacers, as well as to determine the extent of PMMA particulate debris generation. Method. We took tissue specimens around the acetabulae in 12 cases at the time of the second stage procedure for septic total hip revisions. These were subjected to histological analysis to determine the extent of PMMA particulate debris contamination. We also performed a basic explant retrieval analysis of the articulating surfaces of the PMMA spacers to determine any specific wear patterns. Results. We found numerous PMMA particles in the acetabular soft tissues biopsied. The particle concentration was highest in the area of the acetabular fovea. We could also demonstrate specific wear patterns on the spacers that could be correlated with the generally mismatched articulating couple between the spacer and the bony acetabulum. We could also demonstrate some boney destruction present in the acetabulum with long-term spacer use. Conclusions. We concluded that significant amounts of PMMA particulate debris are generated by these articulating antibiotic spacers. The total volume of this debris may be determined by specific wear patterns on the spacers’ surfaces. We recommend a thorough debridement to decrease the PMMA particle load generated. Consideration in respect of the bearing surface implanted after the explantation of the PMMA spacer should take into account the effect of the debris on the bearing surfaces. We also make recommendations in respect of the design of these PMMA spacers

Introduction. Total hip prostheses which use a ceramic head within a metal liner are a relatively recent innovation. As such, survivorship rates from independent centres alongside explant analysis are rare. The early clinical experience with this novel ceramic-on-metal (CoM) bearing couple is reported alongside explant analysis of failed devices. Methods and materials. All CoM hips implanted between 2008 and 2009 at a single hospital by a single surgeon were reviewed. Radiographs were analysed using EBRA software to determine acetabular cup inclination and anteversion angles. Blood metal ion concentrations were measured using inductively coupled plasma mass spectroscopy (ICPMS). Explants were measured for bearing surface and taper wear using a high precision co-ordinate measuring machine (Mitutoyo Legex 322, manufacturer's claimed accuracy 0.8µm). The roughness of the articulating surfaces of heads and liners was measured with a non-contact profilometer (ZYGO NewView 5000, 1nm resolution). Results. In 56 patients 56 CoM hips were implanted. Mean (range) age was 64 years (34–87). There were 41 females and 15 males. Patients were followed-up for a mean of 1.5 years. Three hips were revised at mean of 1.2 years (2 female, 1 male) with a further 3 listed for revision under 1.5 years giving an overall failure rate of 10.7%. All these patients reported with pain. X-rays of failed devices showed a characteristic pattern of femoral stem loosening. Serum cobalt and chromium were less than 2 micrograms/L. Explant analysis of the three revised hips showed wear at the liner rim in each case. In two of these cases the wear extended completely around the circumference. The wear volumes were 4.1, 2.0 and 2.3mm. 3. respectively. The ceramic heads were unworn but some transfer of metal could be seen visually. There was no significant wear or deformation at the taper junctions. Typical ceramic head roughness values were 3nm Ra and so most of the surface area of the heads remained in a pristine condition. Discussion. The high early failure rate using a COM articulation is concerning. Explant analysis suggests equatorial contacts with propagation of high frictional forces distally. These forces may have caused early loosening of the femoral stems. Orthopaedic surgeons and bioengineers need to be aware of this new mechanism of failure in this novel biomaterial coupling which is associated with low metal ions

Background. Established hip and knee arthroplasty registers exist in many countries but this is not the case with spinal implants. Moreover, in the case of a rod intended to guide spinal growth in a child and then be removed, the definition of ‘failure’ (revision) used for hip or knee arthroplasty is inappropriate. How can the performance of such spinal implants be judged?. Methods. Ninety-six MAGnetic Expansion Control (MAGEC) spinal rods were obtained from multiple centres after removal from the spines of 52 children with scoliosis. Clinical details were assessed and divided between unplanned revision operations (‘failures’) and those which were planned. Of the explanted rods, 49 were tested for the amount of force they could output, using the manufacturer's supplied test jig. Sixty-five rods were cut apart so that the internal components (bearings, O-ring seals, drive pins) could be assessed, alongside if there was evidence of internal wear. Results. Seventy-four per cent of revision operations were unplanned. Eighty per cent of explanted rods were unable to produce the force expected from a new rod. All rods (100%) that were successfully cut open showed signs of internal wear. Non- functional bearings were seen in 74% of cases, obvious seal damage in 57% of cases and broken drive pins in 47% of cases. Conclusion. Despite potential clinical benefits, explanted MAGEC rods showed consistent and substantial damage. The majority of rods showed zero force output and most revision operations were unplanned. Independent explant analysis allows appraisal of new technology in arthroplasty for patient benefit

Introduction. Total ankle replacement (TAR) is less successful than other joint replacements with a 77% survivorship at 10 years. Predominant indications for revision include: Insert dislocation, soft tissue impingement and pain/stiffness. Insert edge-loading may be both a product and cause of these indications and was reported to affect 22% of patients with the, now withdrawn from market, Ankle Evolutive System (AES) TAR (Transysteme, Nimes, France). Compressive forces up to seven times body weight over a relatively small contact area (∼6.0 to 9.2 cm. 2. ), in combination with multi-directional motion potentially causes significant polyethylene wear and deformation in mobile-bearing TAR designs. Direct methods of measuring component volume (e.g. pycnometer) use Archimedes' principle but cannot identify spatial changes in volume or form indicative of wear/deformation. Quantitative methods for surface analysis bridge this limitation and may advance methods for analysing the edge loading phenomena in TAR. Aim. Determine the frequency of edge loading in a cohort of explanted total ankle replacements and compare the quantitative surface characteristics using a novel explant analysis method. Methods. Thirty-two AES TAR devices were implanted and retrieved by the same surgeon (UK Health Research Authority approval: 09/H1307/60). Mean implantation time was 7.8 years (1.5 to 12.1 range). Pain and/or loosening were the primary indications for revision. An Alicona Infinite microscope measured the entire superior surface of each insert (10× mag; 1.76µm lateral resolution). Abbott-Firestone curves were produced per insert to quantify the deviation of the insert surface from flat. Peak material volume (Vmp), core material volume (Vmc), core void volume (Vvc) and dale void volume (Vvv) were measured. Edge loading was identified visually by a depressed area in the insert surface indicative of articulation with the edge of the tibial component. Inserts were identified as either edge-loaded or not edge-loaded and the above analyses compared. Results. Seventeen inserts (53%) showed edge loading. Peak material volume (Vmp) was significantly increased for the edge loaded inserts 5.64 ± 5.42µm compared to the normal inserts 1.29 ± 0.954µm (Independent T-Test, P=0.005). No difference was found for the other volume parameters (Figure 2). A progressive change in insert form, beginning at the edges of the superior insert surface, was evident (Figure 1). Machining marks identified at the centre of several components supported this observation. Discussion. Insert edge loading affected 53% of TAR explants. The volume parameters showed a statistically significant inflection of material at the inserts' edge for the affected ankles. Spatial changes to insert form progressed over time in-vivo. Machining marks at the centre of several inserts remained which indicated the deformation/wear process commenced at the periphery of the insert. Normal ranges of volume change/redistribution are not established for TAR devices and the implications of insert form change are not yet understood. However, edge-loaded components composed over half of this cohort, which reflects the conflict between design simplicity and kinematic complexity. For any figures or tables, please contact authors directly (see Info & Metrics tab above).

Background. The failure and subsequent withdrawal of the ASR device in both its resurfacing and THR form has been well documented. The National Joint Registry report of 2010 quoted figures of 12–13% failure at five years. Adverse reaction to metal debris (ARMD) is a poorly understood condition and patients developing severe metal reactions may go unrecognised for sometime. Patients and Methods. In 2004 a single surgeons prospective study of the ASR bearing surface was undertaken. We present the ARMD failure rates of the ASR resurfacing and ASR THR systems. The diagnosis of ARMD was made by the senior author and was based on clinical history, examination, ultrasound findings, metal ion analysis of blood and joint fluid, operative findings and histopathological analysis of tissues retrieved at revision. Mean follow up was 52 months (24–81) and 70 patients were beyond 6 years of the procedure at the time of writing. Kaplan Meier survival analysis was carried out firstly with joints designated “failure” if the patient had undergone revision surgery or if the patient had been listed. A second survival analysis was carried out with a failure defined as a serum cobalt > 7µg/L. Full explant analysis was carried out for retrieved prostheses. Results. There were 505 ASR patients in total. 657 metal ion samples were available at the time of writing (152 repeats). Survival analysis using revision/listed as end point (at 6 years):. ASR resurfacing: 26.1% failure. ASR THR: 55.5% failure. Survival using ion analysis (at 5 years):. ASR resurfacing: 50.1% failure. ASR THR: 66.5% failure. The median (range) volumetric wear rate of failed prosthesis was 8.23mm. 3. /year (0.51–95.5). Conclusion. A number of design flaws in the ASR has led to excessive wear of the bearing & taper leading to catastrophic failure secondary to ARMD