Alumina–alumina bearings are among the most resistant to wear in total hip replacement. Examination of their surfaces is one way of comparing damage caused by wear of hip joints simulated in vitro to that seen in explanted bearings. The aim of this study was to determine whether second-generation ceramic bearings exhibited a better pattern of wear than those reported in the literature for first-generation bearings. We considered both macro- and microscopic findings.

We found that long-term alumina wear in association with a loose acetabular component could be categorised into three groups. Of 20 specimens, four had ‘low wear’, eight ‘crescent wear’ and eight ‘severe wear’, which was characterised by a change in the physical shape of the bearing and a loss of volume. This suggests that the wear in alumina–alumina bearings in association with a loose acetabular component may be variable in pattern, and may explain, in part, why the wear of a ceramic head in vivo may be greater than that seen after in vitro testing.

Polyethylene wear debris in TKA arises from several sources, including the tibiofemoral articulation and the interface between the backside surface of the tibial insert and the metal tibial tray. In this study we identify a new source of abrasive damage to the polyethylene bearing surface: impingement of resected bony surfaces, osteophytes and overhanging acrylic cement on the tibial bearing surface during joint motion.

One hundred forty-eight tibial components of 24 different designs in a retrieval collection were examined. A digital image of the articular surface of each insert was recorded. The presence, location and projected area of abrasive wear to the non-articulating edges of the insert were assessed using image analysis software.

Significant abrasive wear was observed in 24% of the retrievals with cemented femoral components and 9% from non-cemented components. Of the retrievals exhibiting this abrasive wear mode, 46% experienced multiple site damage. The average damage area for each individual abrasive scar was 78±11mm^2. Within the group of worn inserts, the abrasive scars were seen with a frequency of 69% on the extreme medial edge, 19% on the extreme lateral edge, 38% on the posterior-medial edge and 23% on the posterior-lateral edge. In posterior stabilized components with an open femoral box design, scarring of the superior surface of the tibial post was also observed. This proposed mode of damage was confirmed with several retrieved femoral components containing either fixed cement protruding from the posterior condyles, from the medial and lateral edges or osteophytes embedded in the posterior capsule. The corresponding inserts exhibited significant abrasive scarring at those locations.

We have observed a previously unrecognized source of polyethylene damage resulting in gouging, abrasion and severe localized damage in cemented and uncemented total knee replacement. Clearly, acrylic cement, in bulk or particulate form, often contributes to severe damage of the tibial surface and improvements to instruments and techniques for cementing are needed to prevent this wear mechanism.

Artificial hip joints have been in use for a number of years; various combinations of metals and polymers have been tested both in vitro and in vivo. Modern ceramics have found application as bearings in hip replacement due to the enhanced wear and friction that they offer. It has been hypothesised that during the swing phase of gait it is possible for the Femoral head and the Acetabular cup to dislocate, before relocating during heel contact. Severe loading such as this could cause greater levels of wear to occur in artificial hip joints. This study provides comparative analysis between ceramic-on-ceramic hip joint pairings under both severe and standard loading profiles. Five zirconia-toughened alumina (ZTA) 28mm diameter bearing pairs were tested on a ProSim Hip Simulator for 5.3 million cycles (MC), two under severe loading and three under standard loading conditions. Additionally a Loaded Soak Control, Soak Control and Environmental Control were used. Wear was recorded every 0.5 MC by gravimetric measurement. Surface microscopy images from a Zygo New View 100 and an Atomic Force Microscope (AFM) were taken before testing and then at, 0.5 MC. 2.5 MC, and 5.3 MC. The standard loading profile followed . ISO14242. -1 standard with 2650±50N maximum force, ±10° internal-external rotation and −15–30° flexion-extension. To simulate aggressive wear condition, microseparation inferiorly and micro-lateralisation laterally were applied during the swing phase. Dual acting cylinders were used to apply a constant force of 350±50N in opposition to the standard loading profile to enable separation between the Femoral Head and the Acetabular Cup during the swing phase. This microseparation was measured by means of a Linear Variable Differential Transformer (LVDT) and the setting gave a reading of 1.2mm ± 0.1mm at the start of each 0.5 million run. The value for microlateralisation was 0.9mm whilst the inferior separation was 1.2mm. Wear rates for the ceramic cups under severe wear condition were found to be 0.0356±0.0059mm3/ MC and for the standard wear condition to be 0.0178±0.0049mm3/MC. The femoral heads had wear rates of 0.0164±0.0046mm3/MC for severe wear condition and no wear was detected for the standard wear condition. The results of the present study showed almost no wear under standard gait condition and only a modest increase in wear occurred when using severe wear condition. Thus the resulting wear rates are still significantly lower than those found for alumina-alumina total hip joints [. 1. , . 2. ]

INTRODUCTION. Implant wear testing is traditionally undertaken using standardized inputs set out by ISO or ASTM. These inputs are based on a single individual performing a single activity with a specific implant. Standardization helps ensure that implants are tested to a known set of parameters from which comparisons may be drawn but it has limitations as patients perform varied activities, with different implant sizes and designs that produce different kinematics/kinetics. In this study, wear performance has been evaluated using gait implant specific loading/kinematics and comparing to a combination deep knee bend (DKB), step down (SD) and gait implant specific loading on cruciate retaining (CR) rotating platform (RP) total knee replacements (TKR). This combination activity profile better replicates patient activities of daily living (ADL). METHODS. Two sets of three ATTUNE. ®. size 5 right leg CR RP TKRs (DePuy Synthes, Warsaw, IN) were used in a study to evaluate ADL implant wear. Implant specific loading profiles were produced via a validated finite element lower limb model [1] that uses activity data such as gait (K1L_110108_1_86p), SD (K1L_240309_2_144p), and DKB (K9P_2239_0_9_I1) from the Orthoload database [2] to produce external boundary conditions. Each set of components were tested using a VIVO joint simulator (AMTI, Watertown, MA, Figure 1) for a total of 4.5 million cycles (Mcyc). All cycles were conducted at 0.8Hz in force-control with flexion driven in displacement control. Bovine calf serum lubricant was prepared to a total protein concentration of 18g/L and maintained at 37°±2°C. Wear of the tibial inserts was quantified via gravimetric methods per ISO14243–2:2009(E). Polyethylene tibial insert weights were taken prior to testing and every 0.5Mcyc there after which corresponded to serum exchange intervals. The multi-activity test intervals were split into10 loops of 1,250 DKB, 3,000 SD, and 45,750 gait cycles in series. Based on activity data presented by Wimmer et al. the number of cycles per activity and activities used is sufficient for a person that is considered active [3]. A loaded soak control was used to compensate for fluid absorption in wear rate calculations. Wear rates were calculated using linear regression. RESULTS SECTION. The wear rate for the gait-only activity test was calculated to be 0.20±0.04mg/Mcyc conversely the wear rate for the multi-activity test was 2.65±0.67mg/Mcyc (Figure 2). Wear scars can be found in Figure 3. Using a two-sided t-test of unequal variance, it was found that there was a significant difference between the two wear rates (p=0.004). DISCUSSION. Adding activities to the wear simulation test significantly increased the average wear rate of the test samples, confirming that changes in cross shear from different activities will tend to increase the wear of an implant. The results of this study prove that single activity wear testing may not be the most clinically severe wear testing that can be used for pre-clinical wear assessment. For any figures or tables, please contact the authors directly

Posterior stabilized (PS) total knee arthroplasty (TKA), wherein mechanical engagement of the femoral cam and tibial post prevents abnormal anterior sliding of the knee, is a proven surgical technique. However, many patients complain about abnormal clicking sensation, and several reports of severe wear and catastrophic failure of the tibial post have been published. In addition to posterior cam-post engagement during flexion, anterior engagement with femoral intercondylar notch can also occur during extension. The goal of this study was to use dynamic simulations to explore sensitivity of tibial post loading to implant design and alignment, across different activities. LifeModeler KneeSIM software was used to calculate tibial post contact forces for four contemporary PS implants (Triathlon PS, Stryker; Journey BCS and Legion PS, Smith & Nephew; LPS Flex, Zimmer Biomet). An average model of the knee, including cartilage and soft tissue insertion locations, created from MRI data of 40 knees was used to mount and align the component. The Triathlon femoral component was mounted with posterior and distal condylar tangency at: a) both medial and lateral condylar cartilage (anatomic alignment), b) at the medial condylar cartilage and perpendicular to mechanical axis (mechanical alignment with medial tangency), and c) at lateral condylar cartilage and perpendicular to mechanical axis (mechanical alignment with lateral tangency). The influence of implant design was assessed via simulations for the other implant systems with the femoral components aligned perpendicular to mechanical axis with lateral tangency. Five different activities were simulated. The anterior contact force was significantly smaller than the posterior contact force, but it varied noticeably with tibial insert slope and implant design. For Triathlon PS, during most activities anatomic alignment of the femoral component resulted in greater anterior contact force compared to mechanical alignment, but absolute magnitude of forces remained small (<100N). Mechanical alignment with medial tangency resulted in greater posterior contact force for deep knee bend and greater anterior force for chair sit activity. For all implants, peak posterior contact forces were greater for activities with greater peak knee flexion. The magnitude of posterior contact forces for the various implants was comparable to other reports in literature. Overall activity type, implant design and slope had greater impact on post loading than alignment method. Tibial insert slope was shown to be important for anterior post loading, but not for posterior post loading. Anatomic alignment could increase post loading with contemporary TKA systems. In the case of the specific design for which effect of alignment was evaluated, the changes in force magnitude with alignment were modest (<200N). Nonetheless, results of this study highlight the importance of evaluating the effect of different alignment approaches on tibial post loading

Background. Distal femoral replacements (DFR) are used in children for limb-salvage procedures after bone tumor surgery. These are typically modular devices involving a hinged knee axle that has peripheral metal-on-polyethylene (MoP) and central metal-on-metal (M-M) articulations. While modular connections and M-M surfaces in hip devices have been extensively studied, little is known about long-term wear or corrosion mechanisms of DFRs. Retrieved axles were examined to identify common features and patterns of surface damage, wear and corrosion. Methods. The cobalt chromium alloy axle components from 13 retrieved DFRs were cleaned and examined by eye and with a stereo microscope up to 1000× magnification. Each axle was marked into 6 zones for visual inspection: the proximal and distal views, and the middle (M-M) and 2 peripheral (MoP) zones. The approximate percentage of the following features were recorded per zone: polishing, abrasion or scratching, gouges or detectable wear, impingement wear (i.e. from non- intentional articulation), discoloration and pitting. Results. In each case, the middle M-M zones showed more damage features compared with peripheral MoP zones. Brown discoloration, presumably due to tribofilm deposits, was the predominant M-M area feature, particularly at the junction between the MoP and M-M zones. Higher magnification showed areas of polishing underlying the discoloration, suggesting repetitive removal of the surface metal and re-deposition of tribofilms (Fig 2B). 9 cases demonstrated reflective patches resembling “thumbprint” or “fish scale” markings, which, under higher magnification, showed signs of scratching and grooving in a radial pattern (Figs 2D, 3A). Pits were occasionally present but appeared to be from third-body damage as signs of corrosion were absent. Features that resembled carbides, sometimes with associated “comet” patterns of scratching were apparent under higher magnification in some areas. The MoP zones showed variable scratching, abrasion and wear polishing. The MoP to M-M junctional areas were demarcated by a distinct band corresponding, in some cases, to a narrow wear groove or gouge. 3 axles showed evidence of severe impingement wear on one proximal end. Discussion. This study of retrieved axle components demonstrated varying types of surface wear damage but no clear evidence of corrosion. This is presumably because these parts are in nearly constant motion during gait. Third-body damage may have resulted from the breakdown of surface carbides, leading to scratching, abrasion and wear polishing under high contact stress. Severe impingement wear presumably occurred after catastrophic damage to the polyethylene bushings, allowing eccentric loading and extensive metal wear. The components were revised for a range of clinical reasons including aseptic loosening and the need to expand the prosthesis during growth. With the exception of the few cases with severe impingement, it is unlikely that the wear features seen here contributed to the need for revision. While it was reassuring that corrosion was not a prominent feature of these modular M-M articulations, retrieval analysis of DFR components should be continued to confirm this finding, better document the in vivo wear processes and point to design features that might be improved for future patients. For any figures or tables, please contact the authors directly

Aims: The goal was to determine if young patients respect the instructions for medical supervision control instructions after a total hip arthroplasty (THA). Methods:We performed 50 THA (Harris cups and ABG I stems) in 39 patients, mean age 38 years ± 11 (15–58). There were thirty-eight 28mm femoral heads (30 zirconia, 8 chromium-cobalt) and 12 chromium-cobalt heads in 22mm. Each patient was told how necessary a regular medical supervision was with the following schedule: controls at 2 months, 1 year then every two years. In 2000, all the patients were evaluated (no lost for follow-up). Wear was measured according to Livermore with a digitizer. Results: At 72 ± 14 months of follow-up (5–9 years), 51% of the patients (20/39) did not come back for the intermediate controls. No factor could be accounted for that, except being a male (p=0.04). Wear was rather severe (average 0.23 mm/year). 37% of the patients with a severe wear (> 0.2 mm/year) did not come back for intermediate controls and were all free of symptoms. There were 3 revisions because of wear (> 2 mm) and 3 others hips are awaiting revision because of wear. Three of these 6 patients did not come back for intermediate examination. The 28mm heads induced more wear than the 22mm heads (p=0.008). No other factor was related to how severe wear was (age, sex, activity or thickness of polyethylene inserts). Moreover the zirconia did not reduce wear. Conclusion: In spite of the recommendations, half of the patients did not respect the medical supervision schedule and that was unpredictable. We recommend a careful follow-up of young patients after a THA in order to detect wear (usually free of symptoms). Moreover our study underlined that the zirconia wasn’t so efficient to prevent wear phenomena

Aims

The purpose of this study was to assess mid-term survivorship following primary total knee arthroplasty (TKA) with Optetrak Logic components and identify the most common revision indications at a single institution.

Aims

The aim of this study was to longitudinally compare the clinical and radiological outcomes of anatomical total shoulder arthroplasty (aTSA) up to long-term follow-up, when using cemented keel, cemented peg, and hybrid cage peg glenoid components and the same humeral system.

Retrieved alumina-on-alumina hip joints frequently exhibit a localised region of high wear, commonly called ‘stripe wear’. This ‘stripe wear’ can be replicated in vitro by the introduction of micro-separation, where the joint contact shifts laterally reproducing edge loading during the simulated walking cycle. While the origin of stripe wear is clearly associated with the micro-scale impact resulting from micro-separation, the wear processes leading to its formation and the wear mechanisms elsewhere on the joint are not so well understood. The purpose of this study was to compare the surface microstructure of in vivo and in vitro alumina hip prostheses, and investigate the origins of the damage accumulation mechanisms that lead to prosthetic failure. The in vivo alumina hip prosthesis was Biolox (Ceram-Tec, AG, Plochingen, Gemany) implanted for 11 years [. 1. ]. The in vitro alumina hip prosthesis was Biolox-forte (CeramTec, AG, Plochingen, Gemany), which had been tested in a hip joint simulator under micro-separation at Leeds University using the procedures given in [2]. The worn surfaces of the alumina hip prostheses were investigated using a Scanning Electron Microscopy (SEM). Similar worn surfaces were seen for both in vivo and in vitro samples. Focused ion beam (FIB) microscopy was used to determine the sub-surface damage across the stripe wear. Samples were subsequently removed for Transmission Electron Microscopy (TEM). Sub-surface damage was found to be limited to a few μm beneath the surface; ~ 2μm for in vivo samples and ~1μm for in vitro samples. The transition from mild wear to more severe (stripe) wear was entirely triggered by intergranular fracture. The first stages of fracture lead to the liberation of surface grains which act as 3rd body abrasives. The TEM showed that abrasive grooves are associated with extensive surface dislocation activity, which leads to further grain boundary fracture. This allows the cycle to be repeated and accelerated, thus yielding the stripe wear region. The conclusions are: 1. In vitro hip simulation with micro-separation can produce similar microstructure to in vivo alumina hip prostheses; 2. To extend the life of the joint through the avoidance of severe wear, material and design solutions can be investigated using ceramic materials that have an increased surface inter-granular fracture toughness and component designs with reduced contact stress under edge loading

Wear of the underside of modular tibial inserts (“backside wear”) has been reported by several authors. However, the actual volume of material lost through wear of the backside surface has not been quantified. This study reports the results of computerized measurements of tibial inserts of one design known to have a high incidence of backside wear in situ. A series of retrieved TKA components of one design (AMK, Depuy) with evidence of severe backside wear and extrusions of the polyethylene insert were examined. The three-dimensional surface profile of the backside of each insert was digitized and reconstructed with CAD software (UniGraphics). The volume of material removed was calculated from the volume between the worn backside surface and an “initial” surface defined by unworn areas. Computer reconstructions showed that in all retrievals, the unworn surface of the remaining pegs, the rim of material extruded over the medial edge and unworn surfaces on the anterior-lateral edge all lie in a single plane. This demonstrates that the “pegs” present on the backside of these inserts correspond to residual, unworn protrusions remaining on each retrieved component and do not represent cold flow extrusions through the base plate holes. The average volume of material lost due to backside wear was 608mm^3 ± 339mm^3 (range:80–1599 mm^3). This corresponds to an average loss of 569mg and an average linear wear rate of 103mg/year, based on the time in situ for each implant. The volume of material removed due to backside wear is significant and is of a magnitude large enough to generate osteolysis. Our results indicate that the appearance of pegs on the underside of components with screw holes on the baseplate are not due to creep, but instead are due to severe wear of the insert. The mechanisms of material removed due to pitting and burnishing actually produce debris of a size more damaging in terms of osteolysis than wear at the articulating surface making it clear that significant improvements in implant design are needed to prevent backside wear and osteolysis

Two big problems exist with the all polyethylene cemented tibial component; the polyethylene and the cement. The polyethylene is too weak and flexible to bear high tibial load, so it deforms and loosens. The interface stresses are too high when two flexible structures are poorly bonded and heavily loaded. Modularity between the polyethylene tibial component and the metal-backed tray was introduced in the mid-80's for versatility and to facilitate screw fixation for cementless implants. These designs allow exchange of various polyethylene thicknesses, and aids the addition of stems and wedges. Other advantages include the reduction of inventory, and the potential for isolated tibial polyethylene exchanges as a simpler revision procedure. Several studies have documented the high failure rate of isolated polyethylene exchange procedures, because technical problems related to the original components are left uncorrected. However, revision for wear is the simplest revision ever!. Since the late 1980's the phenomena of polyethylene wear and osteolysis have been observed much more frequently when compared with earlier eras. The reasons for this increased prevalence of synovitis, progressive osteolysis, and severe polyethylene wear remain unclear. There is some association with the widespread use of both cementless and cemented modular tibial designs. Improved polyethylene attachment is the answer even if a screw, a wire, or a pin is needed. Do not abandon the modular tibia

Introduction. Titanium nitride (TiN) coatings are used in total hip arthroplasty to reduce friction of bearing couples or to decrease the allergic potential of orthopaedic alloys. Little is known about performance of currently manufactured implants, since only few retrieval studies were performed, furthermore they included a small number of implants manufactured over 15 years ago. Aim of study. To examine wear and degradation of retrieved TiN coated femoral heads articulating with ultra-high molecular weight polyethylene (UHMWPE). Methods. We included eight femoral heads with a made od TiAl6V4 alloy and coated with TiN using Physical Vapour Deposition (PVD). All heads (28 and 32 mm) were retrieved after at least 12 months of use (range 12–56). The reason for revision was aseptic loosening in 6 cases, septic loosening in one case and recurrent dislocations (five episodes) in one uncemented prosthesis. One unused head was included as reference sample. All implants were evaluated with light microscopy, Scanning Electron Microscopy (SEM) with Energy-Dispersive X-ray Spectroscopy (EDS). 30 SEM images from each implant were digitally analysed using ImageJ software to compare damage in loaded and non weight-bearing parts of the heads. Results. Studies with light microscopy revealed severe damage to the dislocated femoral head, with multiple metallic scratches. SEM studies indicated presence of multiple scratches and pinholes with a diameter of 1–10 µm (Fig1a,b,). Residue from the manufacturing process was present in all implants in form of pure Ti droplets found in round voids. In all implants we found irregular areas (diam. 20–50 µm, Fig 1c,d) where the coating was delaminated from the substrate metal with cracks arising from coating defects (Fig1e-h). Some of these debonded fragments were embedded into the PVD layer in weight-bearing parts of all heads. In one head, which was subjected to dislocations we observed deposits of titanium alloy from the acetabular shell (Fig 2a,b). The deposits were accompanied by large patches of delaminated coating as well as multiple cracks (Fig 2c,d). Small fragments of the acetabular titanium alloy damaged the coating in third body mechanism. Surprisingly in three implants we EDS analysis revealed similar spheres (diam. 1–10 µm) containing Niobium (Nb), although this element is not a part of any of the components used in the implants(Fig 2e,f). Interestingly presence of Nb droplets were associated with a higher number of other defect in these heads both in weight-baring and non weight-bearing parts of the heads suggesting inferior coating quality in these cases (Fig 2 g,h; Fig3, cases H2,H5,H8). Conclusions. Compared to previous studies we did not observe severe wear or the coating, however we observed some degradation of the film in vivo. Our results indicate that dislocation can lead to severe failure of the coating in vivo. Moreover presence of Nb residues and coexisting defects in some implants suggests inferior coating quality in these implants and indicates the need for strict monitoring of the production process. This study was funded by a grant from the National Science Centre nr 2012/05/D/NZ5/01840

Introduction. Due to the predictability of outcomes achieved with reverse shoulder arthroplasty (rTSA), rTSA is increasingly being used in patients where glenoid fixation is compromised due to presence of glenoid wear. There are various methods to achieve glenoid fixation in patients with glenoid wear, including the use of bone grafting behind the glenoid baseplate or the use of augmented glenoid baseplates. This clinical study quantifies clinical outcomes achieved using both techniques in patients with severe glenoid wear at 2 years minimum follow-up. Methods. 80 patients (mean age: 71.6yrs) with 2 years minimum follow-up were treated by 7 fellowship trained orthopaedic surgeons using rTSA with bone graft behind the baseplate or rTSA with an augmented glenoid baseplate in patients with severe posterior glenoid wear. 39 rTSA patients (14 female, avg: 73.1 yrs; 25 male, avg: 71.5 yrs) received an augmented glenoid (cohort composed of 24 patients with an 8° posterior augment baseplate and 15 patients with a 10° superior augment baseplate) for treatment of CTA, RCT, and OA with a medially eroded scapula. 41 rTSA patients (27 female, avg: 73.0 yrs; 14 male, avg: 66.9 yrs) received glenoid bone graft (cohort composed of 5 patients with allograft and 36 patients with autograft) for treatment of CTA, RCT, and OA with a medially eroded scapula. Outcomes were scored using SST, UCLA, ASES, Constant, and SPADI metrics; active abduction, forward flexion, and internal/external rotation were also measured to quantify function. Average follow-up was 31.2 months (augment 28.3; graft 34.1). A two-tailed, unpaired t-test identified differences (p<0.05) in pre-operative, post-operative, and pre-to-post improvements. Results. A comparison of pre-operative, post-operative, and pre-to-post improvement in outcomes are presented in Tables 1–3, respectively. No difference was noted in pre-operative, post-operative, and pre-to-post improvement in outcomes between cohorts. The augmented glenoid baseplate rTSA cohort had 0 complications for a complication rate of 0%; whereas, the rTSA glenoid bone graft cohort had 6 complications (including 2 glenoid loosenings/graft failures) for a complication rate of 14.6%. Additionally, radiographic follow-up information was available for 30 of 39 augmented baseplate patients (76.9%) and 27 of 41 bone graft patients (65.9%); where the augmented baseplate rTSA cohort had a scapular notching rate of 10.0% with an average scapular notching grade of 0.1; whereas, the rTSA glenoid bone graft cohort had a scapular notching rate of 18.5% with an average scapular notching grade of 0.19. Conclusions. These results demonstrate positive outcomes can be achieved at 2 years minimum follow-up in patients with severe glenoid wear using either augmented glenoid baseplates or bone graft behind the glenoid baseplate with rTSA. While no statistical difference was noted between pre-operative, post-operative, and pre-to-post improvement in outcomes between rTSA cohorts, a substantial difference in the complication rate was noted between cohorts which may factor into the surgeon's decision of the choice of treatment technique for these patients. Additional and longer-term follow-up is needed to confirm these outcomes and trends

One of serious issues in total hip arthroplasty (THA) is the osteolysis which results in aseptic loosening caused by the wear particles from a polyethylene (PE) acetabular cup. In addition, oxidation degradation of PE cup resulting in the fracture or the severe wear caused by the reduction of mechanical properties in vivo is also the issue. The oxidation degradation is considered to be induced by residual free radicals generated by gamma-ray irradiation for cross-linking to reduce wear or for sterilization. In this study, (1) wear property, (2) oxidation degradation of retrieved PE and highly cross-linked PE (CLPE) cups against alumina ceramic femoral heads, and (3) the correlation between those properties were evaluated. The radiographic wear of six conventional PE cups with the mean follow-up of 19.1–23.3 years and 60 CLPE cups with the mean follow-up of 3.1–9.1 years were measured by a non-radiostereometric analysis method (Vectorworks. ®. 10.5 software package). As a retrieval analysis, 26 retrieved acetabular cups were evaluated; 16 cups were ethylene oxide gas-sterilized conventional PE cups with clinical use for 16.0–24.9 years and 10 cups were gamma-ray-sterilized CLPE cups with clinical use for 0.9–6.7 years. The linear and the volumetric wear were measured using a three-dimensional (3D) coordinate measurement machine. The shapes of unworn and worn surfaces with 15- and 30-point intervals, respectively, were measured. Oxidation degradation of the surface, sub-surface and inner for both worn and unworn parts of the retrieved cups was measured using a Fourier-transform infrared (FT-IR) spectroscopy. Oxidation indices were calculated using the peak at 1740 cm. −1. and 1370 cm. −1. according to ASTM F2012. In the radiographic analysis, the linear wear rate of CLPE cups was significantly lower than that of conventional PE cups [Fig. 1]. In the retrieval analysis, the linear wear rate of CLPE cups (mean: 0.07 mm/year) showed a 51% reduction (p = 0.002) compared to conventional PE cups (mean: 0.14 mm/year) [Fig. 2]. The retrieval and the radiographic analysis for both conventional PE and CLPE cups showed similar results (p = 0.7 and 0.1, respectively). Maximum oxidation indices for CLPE cups were similar to those of conventional PE cups regardless of the difference of clinical duration [Fig. 3]. This result is different from in vivo wear, which increases as the clinical duration. For both conventional PE and CLPE cups, the oxidation indices of subsurface were higher than those for surface. The worn parts showed higher oxidation indices than those for unworn parts. From the results, even when the free radicals were so few or absent, the oxidation degradation would be induced in vivo. In conclusion, the wear resistance for CLPE cups was greater than that for conventional PE cups from both radiographic and retrieval analyses. The in vivo oxidation degradation might not be caused by only residual free radicals. It was found that oxidation degradation of PE cups when used with alumina ceramic femoral heads is not correlated to their wear properties

The issues surrounding raised levels of metal ions in the blood following large head metal-on-metal total hip replacement (THR), such as cobalt and chromium, have been well documented. Despite the national popularity of uncemented metal-on-polyethylene (MoP) THR using a large-diameter femoral head, few papers have reported the levels of metal ions in the blood following this combination. Following an isolated failure of a 44 mm Trident–Accolade uncemented THR associated with severe wear between the femoral head and the trunnion in the presence of markedly elevated levels of cobalt ions in the blood, we investigated the relationship between modular femoral head diameter and the levels of cobalt and chromium ions in the blood following this THR. A total of 69 patients received an uncemented Trident–Accolade MoP THR in 2009. Of these, 43 patients (23 men and 20 women, mean age 67.0 years) were recruited and had levels of cobalt and chromium ions in the blood measured between May and June 2012. The patients were then divided into three groups according to the diameter of the femoral head used: 12 patients in the 28 mm group (controls), 18 patients in the 36 mm group and 13 patients in the 40 mm group. A total of four patients had identical bilateral prostheses in situ at phlebotomy: one each in the 28 mm and 36 mm groups and two in the 40 mm group. There was a significant increase in the mean levels of cobalt ions in the blood in those with a 36 mm diameter femoral head compared with those with a 28 mm diameter head (p = 0.013). The levels of cobalt ions in the blood were raised in those with a 40 mm diameter head but there was no statistically significant difference between this group and the control group (p = 0.152). The levels of chromium ions in the blood were normal in all patients. The clinical significance of this finding is unclear, but we have stopped using femoral heads with a diameter of ≤ 36 mm, and await further larger studies to clarify whether, for instance, this issue particularly affects this combination of components. Cite this article: Bone Joint J 2014;96-B:43–7

Multiaxial rotation of femoral component is generated in a wide range against UHMWPE tibial insert during ambulation or deep bending activities. Simultaneously, microscopic oscillation and twisting might accompany with such a wide-range motion. Such a combined in-vivo kinetics is expected to bring more severe wear to the sliding surface of knee joint prostheses than that in a case of single macro-kinetics (i.e., that commonly reproduced by conventional wear simulators). In order to reproduce clinical surface degradation correctly and quantitatively in simulator tests, we have to consider microscopic motions at the joint bearing surfaces. The purpose of this study is to analyze the influence of the composite knee motion on wear using a non-destructive spectroscopic approach. The crystalline phase in UHMWPE is pre-oriented in the tibial insert from the manufacturing process, but the orientation of crystalline lamellae is sensitive to mechanical loading. Therefore, the orientation of the crystalline lamellae on the surface of retrieved UHMWPE tibial inserts could reflect the local motions in vivo generated in the joint during ambulation. The visualization of (orthorhombic) crystalline lamellae might ultimately lead to the possibility of tracking back the wear history of the joint. In this study, polarized Raman spectroscopy was employed in order to non-destructively visualize the lamellar orientation in UHMWPE tibial inserts, which were retrieved after exposures in human body elapsing several years. According to this Raman analysis and in comparison with an unused insert, the orientation of surface lamellae was found to have been clearly changed due to wear in accordance to the local motion of the femoral component. Additionally, we could obtain information about the origin of delamination from the in-depth profile for lamellae orientation angle. This study not only shows the possibility of optimizing the UHMWPE structure to minimize wear but also gives a hint for the development of knee simulators of the next generation

We examined 86 polyethylene inserts, retrieved from total and unicompartmental knee prostheses after an average of 39.5 months in situ, grading them from 0 to 3 for seven modes of polyethylene degradation. Severe wear, with delamination or deformation, was observed in 51% of the implants, and was associated with time in situ, lack of congruency, thin polyethylene, third-body wear debris, and heat-pressed polyethylene. Significant under-surface cold flow was identified in some areas of unsupported polyethylene, and was associated with delamination in the load-bearing areas of thin inserts above screw holes in the underlying metal tray. We recommend the use of thicker polyethylene inserts, particularly in young, active patients and in designs with screw holes in the tibial baseplate. Thin polyethylene inserts which are at risk for accelerated wear and premature failure should be monitored radiographically at annual intervals

We removed 23 Charité artificial discs in 19 patients due to severe back-and legpain and performed an anterior as well posterior fusion. Mean interval between insertion and retrieval is 8,4 years (3,0–16,0 years). The mean age at retrieval is 49,4 years (40–72 years). The cause of persistent or recurrent pain was one or more of several problems thought to be related to the pain: subsidence, migration, wear with or without breakage of the metal marker ring, facetjoint or adjacent degeneration. In all cases wear of the polyethylene core was seen in major or minor degree. The wear was related to posterior impingement possibly due to hyperlordosis and extension instability and was subsequently more pronounced in the peripheral rim than in the central dome. Also a relationship was noted to in vivo oxidation of the polyethylene, especially in the rim. In the periprosthetic tissue an inflammatory reaction was found, more in the severe wear cases. Polyethylene loaded macrophages were seen, also polyethylene particles lying freely in the tissue. The macrophages proved positive for Interleukin 6. The wear pattern and the inflammatory reaction resembles the pattern seen in total hips and knees. Probably a substantial number of patients will exhibit these wear changes some years after insertion. It is questionable whether changes in sterilization and packaging and better insertion and sizing techniques will prevent wear development in the future

Ceramic-on-ceramic bearing is an attractive alternative to metal-on-polyethylene bearing due to the unique tri-bological advantages of alumina. However, despite the long-term satisfactory results obtained so far in the vast majority of patients, failure may occur in a few cases. Clinical, radiographic, laboratory and microbiological data of 30 consecutive subjects with failed alumina-on-alumina total hip arthroplasties (THA) were analyzed to define if foreign body reaction to wear debris may be responsible for periprosthetic bone resorption, as in conventional metal-to-polyethylene bearings. In all cases, clinical and radiographical material was reviewed, retrieved implants were examined, and histology of periprosthetic tissues was analyzed. Massive osteolysis was never observed. Apart from 5 five patients for which revision surgery was necessary due to the occurrence of late infection, in all other cases failure had occurred due to secondary implant instability (as in the case of screwed sockets, 19 cases) or to malpositioning of the implant (5 cases). One patient suffered from chronic dislocation. In the vast majority of cases, ceramic wear debris was absent or scarce, and did not induce any tissue reaction. In a few cases with severe wear, debris was evident in clusters of perivascular macrophages, notably in the absence of foreign body multinucleated cells, confirming the excellent biocompatibility of ceramics. These findings indicate that wear debris and peri-prostetic bone resorption were the effect rather than the cause of failure, differently from revised metal-on-polyethylene bearings, in which foreign body cell reaction is the main pathogenetic mechanism of failure. On the contrary, mechanical problems, due to incorrect surgical technique or to inadequate prosthetic design, may cause instability of the implant, in turn resulting in wear debris production and moderate if any biological reaction