Total knee arthroplasty with a rotating hinge knee with carbon-fibre-reinforced (CFR)-PEEK as an alternative bushing material with enhanced creep, wear and fatigue behaviour has been clinically established [1-4]. The objective of our study was to compare results from in vitro biotribological characterisation to ex vivo findings on a retrievals. A modified in vitro wear simulation based on ISO 14243-1 was performed for 5 million cycles on rotating hinge knee (RHK) designs (EnduRo®) out of cobalt-chromium and ZrN-multilayer ceramic coating. The rotational & flexion axles-bushings and the flanges are made of CFR-PEEK with 30% polyacrylonitrile fibre content. Analysis of 12 retrieved EnduRo® RHK systems in cobalt-chromium and ZrN-multilayer in regard to loosening torques, microscopic surface analysis, distinction between different wear modes and classification with a modified HOOD-score has been performed. For the RHK design with the polyethylene gliding surface and bushings and flanges made out of CFR-PEEK, a cumulative volumetric wear was measured to be 12.9±3.95 mm. 3. in articulation to cobalt-chromium and 1.3±0.21 mm. 3. to ZrN-multilayer coating - a significant 9.9-fold decrease (p=0.0072). For the CFR-PEEK flexion bushing and flanges the volumetric wear rates were 2.3±0.48 mm. 3. /million cycles (cobalt-chromium) and 0.21±0.02 mm. 3. /million cycles (ZrN-multilayer) (p=0.0016). The 5 million cycles of in vitro wear testing reflect a mean in vivo service life of 2.9 years, which is in accordance to the time in vivo of 12–60 months of the retrieved RHK components [5]. The main wear modes were comparable between retrievals and in vitro specimens, whereby the size of affected area on the retrieved components showed a higher variation. For the EnduRo® RHK design the findings on retrieved implants demonstrate the high suitability of CFR-PEEK as a biomaterial for highly loaded bearings, such as RHK bushings and flanges in articulation to cobalt-chromium and to a ZrN-multilayer coating

Objectives. The Precice nail is the latest intramedullary lengthening nail with excellent early outcomes. Implant complications have led to modification of the nail design. The aim of this study was to perform a retrieval study of Precice nails following lower-limb lengthening and to assess macroscopical and microscopical changes to the implants and evaluate differences following design modification, with the aim of identifying potential surgical, implant, and patient risk factors. Methods. A total of 15 nails were retrieved from 13 patients following lower-limb lengthening. Macroscopical and microscopical surface damage to the nails were identified. Further analysis included radiology and micro-CT prior to sectioning. The internal mechanism was then analyzed with scanning electron microscopy and energy dispersive x-ray spectroscopy to identify corrosion. Results. Seven male and three female patients underwent 12 femoral lengthenings. Three female patients underwent tibial lengthening. All patients obtained the desired length with no implant failure. Surface degradation was noted on the telescopic part of every nail design, less on the latest implants. Microscopical analysis confirmed fretting and pitting corrosion. Following sectioning, black debris was noted in all implants. The early designs were found to have fractured actuator pins and the pin and bearings showed evidence of corrosive debris. The latest designs showed evidence of biological deposits suggestive of fluid ingress within the nail but no corrosion. Conclusion. This study confirms less internal corrosion following modification, but evidence of titanium debris remains. We recommend no change to current clinical practice. However, potential reuse of the Precice nail, for secondary limb lengthening in the same patient, should be undertaken with caution. Cite this article: V. C. Panagiotopoulou, K. Davda, H. S. Hothi, J. Henckel, A. Cerquiglini, W. D. Goodier, J. Skinner, A. Hart, P. R. Calder. A retrieval analysis of the Precice intramedullary limb lengthening system. Bone Joint Res 2018;7:476–484. DOI: 10.1302/2046-3758.77.BJR-2017-0359.R1

Hip implant retrieval analysis is the most important source of insight into the performance of new materials and designs of hip arthroplasties. Even the most rigorous in vitro testing will not accurately simulate the behavior of implant materials and new designs of prosthetic arthroplasties. Retrieval analysis has revealed such factors as the effects of gamma-in-air sterilisation of polyethylene, fatigue failure mechanisms of polymethylmethacrylate bone cement, fretting corrosion of Morse taper junctions, third body wear effects of both hard-on-hard and hard-on-soft bearing couples, and the effects of impingement of components on the full spectrum of bearing surfaces, none of which was predicted by pre-implantation in vitro testing of these materials and combinations. The temporal sequence of the retrieval process is approximately six years from first implantation through retrieval analysis, laboratory investigation, and publication of results, and thus, in addition to rigorous clinical evaluation, represents the true development and insight cycle for new designs and materials

This multicentre study analysed 12 alumina ceramic-on-ceramic components retrieved from squeaking total hip replacements after a mean of 23 months in situ (11 to 61). The rates and patterns of wear seen in these squeaking hips were compared with those seen in matched controls using retrieval data from 33 ‘silent’ hip replacements with similar ceramic bearings. All 12 bearings showed evidence characteristic of edge-loading wear. The median rate of volumetric wear was 3.4 mm. 3. /year for the acetabular component, 2.9 mm. 3. /year on the femoral heads and 6.3 mm. 3. /year for head and insert combined. This was up to 45 times greater than that of previously reported silent ceramic-on-ceramic retrievals. The rate of wear seen in ceramic components revised for squeaking hips appears to be much greater than in that seen in retrievals from ‘silent’ hips.

Objectives. The use of ceramic femoral heads in total hip arthroplasty (THA) has increased due to their proven low bearing wear characteristics. Ceramic femoral heads are also thought to reduce wear and corrosion at the head-stem junction with titanium (Ti) stems when compared with metal heads. We sought to evaluate taper damage of ceramic compared with metal heads when paired with cobalt chromium (CoCr) alloy stems in a single stem design. Methods. This retrieval study involved 48 total hip arthroplasties (THAs) with CoCr V40 trunnions paired with either CoCr (n = 21) or ceramic (n = 27) heads. The taper junction of all hips was evaluated for fretting/corrosion damage and volumetric material loss using a roundness-measuring machine. We used linear regression analysis to investigate taper damage differences after adjusting for potential confounding variables. Results. We measured median taper material loss rates of 0.210 mm. 3. /year (0.030 to 0.448) for the metal head group and 0.084 mm. 3. /year (0.059 to 0.108) for the ceramic group. The difference was not significant (p = 0.58). Moreover, no significant correlation between material loss and implant or patient factors (p > 0.05) was found. Conclusions. Metal heads did not increase taper damage on CoCr trunnions compared with ceramic heads from the same hip design. The amount of material released at the taper junctions was very low when compared with available data regarding CoCr/Ti coupling in metal-on-metal bearings. Cite this article: A. Di Laura, H. Hothi, J. Henckel, I. Swiatkowska, M. H. L. Liow, Y-M. Kwon, J. A. Skinner, A. J. Hart. Retrieval analysis of metal and ceramic femoral heads on a single CoCr stem design. Bone Joint Res 2017;6:–350. DOI: 10.1302/2046-3758.65.BJR-2016-0325.R1

Introduction. The use of Additive Manufacturing (AM) to 3D print titanium implants is becoming widespread in orthopaedics, particularly in producing cementless porous acetabular components that are either custom-made or off-the-shelf; the primary design rationale for this is enhanced bony fixation by matching the porosity of bone. Analysis of these retrieved components can help us understand their performance; in this study we introduce a non-destructive method of the retrieval analysis of 3D printed implants. Material and methods. We examined 11 retrieved 3D printed acetabular cups divided into two groups: “custom-made” (n = 4) and “off-the-shelf” (n = 7). A macroscopic visual analysis was initially performed to measure the area of tissue ongrowth. High resolution imaging of each component was captured using a micro-CT scanner and 3D reconstructed models were used to assess clinically relevant morphometric features of the porous structure: porosity, porous structure thickness, pore size and strut thickness. Optical microscopy was also used as a comparison with microCT results. Surface morphology and elemental composition of the implants were investigated with a Scanning Electron Microscope (SEM) coupled with an Energy Dispersive X-ray Spectroscope (EDS). Statistical analysis was performed to evaluate possible differences between the two groups. Results. We found a spread of tissue coverage, median of 81% (23 – 95), with a trend with time in situ. Custom implants showed a higher spread of porosity, with median value of 74.11% (67.94 – 81.01), due to the presence of differently designed porous areas. Off-the-shelf cups had median porosity of 72.49% (66.67 – 73.07), but there was no significant difference between the two groups (p = 0.164). There was a significant difference in the thickness of the porous structure of the two groups, which were 3.918 mm (3.688 – 4.102) and 1.289 mm (1.235 – 1.364), respectively (p = 0.006). SEM output showed specific morphological features of 3D printed object; EDS analysis suggested that no chemical modifications occurred in vivo, with elemental ratios (Ti/Al = 14; Ti/V = 21; Al/V = 1.51) comparable to previously published results. Conclusion. This is one of the first retrieval studies of 3D printed orthopaedic implants. We introduced a method for the investigation of these components and micro-CT scanning enabled the non-destructive assessment of the porous structure. This work represents the first step in understanding the performance of 3D printed implants

Introduction. During revision surgery with a well-fixed stem, a titanium sleeve can be used in conjunction with a ceramic head to achieve better stress distribution across the taper surface. Previous studies have observed that the use of a ceramic head can mitigate the extent of corrosion damage at the taper. Moreover, in vitro testing suggests that corrosion is not a concern in sleeved ceramic heads [1]; however, little is known about the in vivo fretting corrosion of the sleeves. The purpose of this study was to investigate fretting corrosion in sleeved ceramic heads. Materials and Methods. Thirty sleeved ceramic heads (Biolox Option: CeramTec) were collected during revision surgery as part of a multi-center retrieval program. The sleeves were used in conjunction with a zirconia-toughened alumina femoral head. The femoral heads and sleeves were implanted between 0.0 and 3.25 years (0.8±0.9, Figure 1). The implants were revised predominantly for instability (n=14), infection (n=7), and loosening (n=5). Fifty percent of the retrievals were implanted during a primary surgery, while 50% had a history of a prior revision surgery. Fretting corrosion was scored using a previously described 4-point, semi-quantitative scoring system proposed by Higgs [2]. Results. Among the sleeved ceramic heads, mild-to-moderate fretting corrosion scores (Score = 2–3) were observed in 96% of internal tapers, 26% of external tapers, and 82% of the stems. On the internal taper surface, 5 sleeves had moderate fretting corrosion data (Score = 3, Figure 2). None of sleeves had severe (Score = 4) at any taper surface. Fretting corrosion scores were higher at the internal taper surface than the external taper. Implantation time was the main predictor of increased fretting-corrosion of the external sleeve tapers. Discussion. For the sleeved ceramic heads, we found that fretting corrosion can occur in these components, particularly on the internal surface of the sleeve. However, the fretting corrosion scores were predominantly mild, and lower than fretting scores of CoCr heads in metal on polyethylene bearings. Because the sleeves are Ti alloy, the corrosion products are considered to be less cytotoxic than Co and Cr. The primary limitation to this study is the short-term follow-up of these retrievals. As the fretting corrosion process is often associated with in vivo duration, future studies with longer-term implants are necessary to elucidate the long-term performance of these devices

Summary. Fifteen irradiated, vitamin E-diffused UHMWPE retrievals with up to three years in vivo service showed no appreciable oxidation, nor change in material properties from a never-implanted liner, and showed a 94% decrease in free radical content. Introduction. Radiation cross-linking, used to improve wear resistance of ultra-high molecular weight polyethylene (UHMWPE) bearings used in total joint arthroplasty, generates residual free radicals which are the precursors to oxidative embrittlement. First generation materials adopted thermal treatments to eliminate or reduce free radical content, but came with compromises in reduced mechanical properties or insufficient stabilization. A second generation alternative method infuses an antioxidant, vitamin E, into irradiated UHMWPE to stabilise free radicals while maintaining fatigue strength. In vitro studies predict excellent oxidation and wear resistance in vitamin E-stabilised bearings, but the long-term in vivo oxidation behavior, influenced by lipid absorption and cyclic loading, remains largely unknown. Our aim was to investigate in vivo changes in UHMWPE surgically-retrieved explants that were radiation cross-linked and stabilised by vitamin E. Patients & Methods. Fifteen surgically-retrieved irradiated, vitamin E-diffused and inert-gamma sterilised bearings (E1™, Biomet, Inc., Warsaw IN) with in vivo durations ranging from 3 days to 36.6 months were analyzed at unloaded rim/eminence and the articular surface along with one never-implanted component. Total lifetime of components was summed as shelf storage prior to implantation, in vivo duration and ex vivo duration in air. Fourier Transform Infrared Spectroscopy (FTIR) was used to measure carbonyl index (CI; per ASTM F2102-01ε1) both before and after 16 hour hexane extraction to. Extracted thin films were also reacted with nitric oxide to quantify hydroperoxides, an intermediate oxidation product associated with oxidation potential. Cross-link density was calculated from gravimetric swelling analysis per ASTM F2214. Crystallinity measurements were performed regionally using differential scanning calorimetry (DSC). Free radical content was measured by electron spin resonance (Memphis, TN). Results. Irradiated and vitamin E-diffused retrievals showed scratching at the articular surface, but retained machining marks up to three years in vivo, indicative of no measurable wear. Retrievals showed no significant oxidation at the time of surgical removal with maximum post-hexane carbonyl indices in the barely detectable range (MCI=0.029–0.154), located at the surface of retrievals. Ex vivo oxidation was not observed after 18 months of aging in air at room temperature. There was no increase in hydroperoxides (never-implanted HI=0.62±0.04; retrieval HI= 0.62±0.04), nor change in cross-link density (never-implanted: 0.275±0.015 mol/dm. 3. ; retrieval: 0.295±0.016 mol/dm. 3. ) or crystallinity (never-implanted: 58.3±1.4%; retrievals: 60.0±3.5%). Lipid penetration increased with time, showing a higher rate of diffusion in loaded regions. Free radical content was observed to decay with increasing in vivo duration (R. 2. =0.44; p<0.05), and by one order of magnitude (94%) by 36.6 months. A stronger negative correlation (R. 2. =0.65) was observed between the total lifetime of the liner and free radical content. Discussion/Conclusion. The free-radical scavenging activity of the vitamin E appears to successfully prevent both in vivo and ex vivo oxidation for short durations. Without an increase in hydroperoxides, the oxidation cascade initiated by radiation-induced and lipid-derived free radicals appears to have been halted. Retrievals also gave no indication of wear in this timeframe, similar to improved wear resistance seen in first generation materials. Continued monitoring will be necessary at longer implant durations

Introduction. In an effort to provide a TKA bearing material that balances resistance to wear, mechanical failure and oxidation, manufacturers introduced antioxidant polyethylene. In many designs, this is accomplished through pre-blending the polymer with the antioxidant before consolidation and radiation crosslinking. This study reports the wear performance (in terms of thickness change) of a hindered phenol (PBHP) UHMWPE from analysis of an early series of knee retrievals and explores these questions: 1) What is early-time performance of this new bearing material? 2) Is there a difference in performance between fixed and mobile bearings in this design? 3) How does quantitative surface analysis help understand performance at the insert-tray modular interface?. Methods. A series of 100 consecutive Attune™ knee inserts (DePuy Synthes, Warsaw, IN) received at revision by an IRB approved retrieval laboratory between September 2014 and March 2019 were investigated. In vivo duration was 0–52 months. Both the fixed bearing design (n=74) and the rotating platform mobile bearing design (n=26) were included. Dimensional change was determined by measurement of each insert and compared to the as-manufactured dimensions, provided by the manufacturer. The insert-tray interfaces under the loaded bearing zones were analyzed with light interferometry using an optical surface profiler (NewView™ 7300, Zygo, Middlefield, CT). Statistical analyses to explore relationships between measured variables were conducted using SPSS. Results. Mean total through-thickness change of the inserts was 0.052 mm. Mean rate of thickness change for all inserts having in vivo duration > 12 months was 0.038 mm/year (fixed bearing 0.042, mobile bearing 0.029 mm/year). The rate of thickness change for all inserts showed a decreasing trend with duration that was not statistically significant, (rho -.244, p=.094); however, the mobile bearing cohort alone showed a significant decrease in thickness change rate with duration (rho= −.659; p=.014). Surface roughness (Sa) of the distal surface of the UHMWPE inserts under the bearing areas averaged 1.24 µm (range 0.12 – 8.53) and peak-to-valley height (PV) averaged 27.1 µm (range 4 – 95). Sa and PV both showed a decreasing trend with duration in vivo in the mobile bearing inserts, but that trend did not reach statistical significance (p= 0.05 criterion). Neither Sa nor PV showed correlation with measured thickness change. Discussion. This study indicates that the rate of thickness change of a relatively new antioxidant cross-linked bearing material is very similar to other reported wear rates of crosslinked knee inserts. Lower wear rate of mobile bearing inserts compared to fixed bearings also is consistent with earlier published studies. Direct comparison between quantitative thickness change and objective, quantitative surface metrology on the same series brings new information to the arena of measuring and reporting “wear” of UHMWPE and underscores the importance of the distinction between visual damage and actual thinning of the bearing. The systematic surface analysis of the modular interfaces showing that surface roughness (Sa) and total damage feature topography (PV) trend downward with in vivo duration of mobile bearings supports the hypothesis that relative motion at that interface may ‘polish out’ the surface topography over time. For any figures or tables, please contact authors directly

Objectives . We aimed to determine the effect of surgical approach on the histology of the femoral head following resurfacing of the hip. Methods. We performed a histological assessment of the bone under the femoral component taken from retrieval specimens of patients having revision surgery following resurfacing of the hip. We compared the number of empty lacunae in specimens from patients who had originally had a posterior surgical approach with the number in patients having alternative surgical approaches. Results. We found a statistically significant increase in the percentage of empty lacunae in retrieval specimens from patients who had the posterior approach compared with other surgical approaches (p < 0.001). . Conclusions. This indicates that the vascular compromise that occurs during the posterior surgical approach does have long-term effects on the bone of the femoral head, even if it does not cause overt avascular necrosis. Cite this article: Bone Joint Res 2013;2:200–5

Hemi shoulder arthroplasty is an attractive treatment for shoulder arthritis in particular if the natural glenoid is still intact. However, comparing the clinical results of hemi and total shoulder arthroplasty clearly shows lower survival for the hemi arthroplasty. One of the most common reasons for revision surgery is gleniod erosion, where the cartilage or bone is worn of. Aim of the current study was to analyse if the metallic articular surface of retrieved hemi shoulder arthroplasty is different from new implants. We hypothesized that the surface roughness will increased due the articulation and that metallic wear is detectable on the implants. Twelve retrieved and three brand new hemi shoulder arthroplasty were included. The surface roughness (Ra, Rz, Rmax, Rsk) was measured on different sites of the surface (center of the head and at the edge). The implants were further measured using a coordinate measuring machine to gain information on volumetric wear and geometrical alterations. Compared to new implants the surface roughness on the retrievals was significantly increased (Tab. 1), except for skewness. Although the roughness parameters within the retrieval group were generally higher at the center of the head compared to the edge, this difference was not significant. Apart from form deviations no volumetric wear was detectable on the heads (Fig. 1). The current results indicate that the metallic articular implant surface changes in vivo and that the material is hurt due to the articulation against the softer cartilage or bone. Although it can't be finally clarified by that study, to what extend the higher roughness is taking part in the process of the clinically observed erosion of the gleniod, it can be assumed that an increased roughness is disadvantageous. Possibly, the observed surface alterations won't occur clinically with harder materiel (e.g. ceramic), but this even needs to be validated

Background. One of the potential complications of polyethylene liner (PL) is its dissociation from the metal shell. This is a rare but catastrophic complication of total hip replacement (THR). Objective. was to analyze the retrieved dissociated components (PL and shell) (Depuy Pinnacle, Warsaw, IN, USA) to evaluate the mechanism of failure. All these components were dissociated within four years of implantation. Methods. Components were retrieved from three different centers in Canada over the period from January 2011 to October 2016. The analysis was done at the Orthopaedic Innovation Centre (OIC) in Winnipeg Canada. Nine PLs were retrieved at the time of revision THR. Assessment using optical and scanning electron microscopies at magnification between 25× and 150× was performed. The following questions were asked: 1) were the liners correctly seated at the primary surgery? 2) Are there signs of impingement present which could have caused the liner to become dissociated? 3) Does the wear pattern indicate that the liner was failing prior to dissociation?. Results. All PLs dissociated in the inferior direction. Five PL were believed to have been seated properly at the time of indexed surgery. All PL displayed signs of post dissociation impingement. Only 1 PL had fractured resulting in failure prior to dissociation. Other PL showed signs of wear, however none of them reached thinness that would be a cause for concern. Eight PLs demonstrated shearing of the anti rotation tabs. Assessment of the anti rotation tabs revealed that a couple had sheared off suddenly while remaining anti rotation tabs sheared off in progressive fatigue resulting in the failure of the locking mechanism. Conclusions. Retrieval analysis was useful in identifying common patterns of failure such as anti-rotation tab damage. This was suggestive that the locking mechanism of the acetabular components has probably failed in 8 out of 9 of the retrieved liners

Clinical implantation represents the ultimate experiment of any component and often demonstrates areas of strengths and weaknesses not predicted from in vitro testing. Mobile bearing knees incorporate an additional articulating interface between the flat distal PE insert and a highly polished metal tibial tray. This can allow the proximal interface to retain high conformity whilst leading to reduced stresses at the bone – prosthesis interface by permitting complex distal interface compensatory motion to occur (rotation and/or translation). Retrieval reports on many of the new generation of mobile bearing implants remains scarce. This study presented a retrieval analysis of 9 mobile bearing inserts that had be in situ for less than 24 months. Nine cemented mobile bearing implants (6 AP Glide, 1 LCS, 1 MBK and 1TRAK) were received into our Implant Retrieval Program. The femoral component, tibial tray and PE insert were macroscopically examined under a stereo-zoom microscope for evidence of damage. The PE inserts were graded for wear based on optical and SEM assessments. The proximal and distal surfaces of the PE inserts were subsequently assessed for surface roughness following ISO 97 (Ra and Rp) using a Surfanalyzer 5400 (Federal Products, Providence, RI). Virgin, unused PE inserts were analysed and served as a comparison to the retrieved implants. Time in situ time for these implants ranged from 6 months to 24 months (mean 18.6). The implants were revised for instability and pain (AP glide) or dislocation (TRAK). Damage to the femoral components, in general, was minimal with some evidence of a transfer film of PE. The proximal surface of the tibial trays presented evidence of PE transfer as well as some scratches but in general were intact. The proximal PE and distal PE articulating surfaces demonstrated significant areas of damage due to third body wear which was identified on EDAX to be PMMA. Areas of burnishing were also present at the proximal and distal interface. The damage, in part, correlated with the complex kinematics of each design

From 1985 metal-on-metal (MOM) designs of resurfacing (RSA) and total hip arthroplasties (THR) have been available over a large diameter range (28–60mm). In-vitro studies indicated satisfactory low wear performance for all designs and diameters tested (wear = 0.1 to 7 mm3). While reports from many centers have been encouraging, some have reported adverse effects. We reviewed clinical and metal ion studies in large diameter retrievals and compared these to 28mm MOM cases. Patients with the latter THR ranged 36–76 years of age and were followed 9–11 years. Main finding in our revisions was osteolysis and pain. The 28mm ball was represented 86% of cases; 71% balls had stripe wear. For liners, 25% had circumferential stripe wear and impingement was evident in 64% cases. Seven cemented stems were recovered with impingement marks; 26 stems were undamaged and therefore not revised. Using the concept of ‘damage modes’ from McKellop, normal wear mode #1 was evident in only 14% of 28mm retrievals whereas incidence of ‘abnormal’ modes #2-4 approached 30% each. Thus the 28mm MOM appeared susceptible to impingement risks with CoCr liners. Summarizing MOM retrievals, damage modes 2–4 were most likely implicated in revisions. The performance of such ‘small diameter’ THRs will be contrasted to our large diameter THR and RSA experience. The questions to be reviewed include, how much of the reported MOM adversity was predictable and how much risk was due to. wear of small diameter MOM,. adverse cup positioning and hip instability,. cup-stem impingement issues or. design conformity issues?

Introduction. Previous studies of retrieved CoCr alloy femoral heads have identified imprinting of the stem taper surface features onto the interior head bore, leading researchers to hypothesize that stem taper microgrooves may influence taper corrosion. However, little is known about the role of stem taper surface morphology on the magnitude of in vivo corrosion damage. We designed a matched cohort retrieval study to examine this issue. Methods. From a multi-institutional retrieval collection of over 3,000 THAs, 120 femoral head-stem pairs were analyzed for evidence of fretting and corrosion using a visual scoring technique based on the severity and extent of fretting and corrosion damage observed at the taper. A matched cohort design was used in which 60 CoCr head-stem pairs with a smooth stem taper were matched with 60 CoCr head-stem pairs having a micro-grooved surface, based on implantation time, flexural rigidity, apparent length of taper engagement, and head size. This study was adequately powered to detect a difference of 0.5 in corrosion scores between the two cohorts, with a power of 82% and 95% confidence. Both cohorts included CoCr and Ti-6-4 alloy femoral stems. A high precision roundness machine (Talyrond 585, Taylor Hobson, UK) was used to measure surface morphology and categorize the stem tapers into smooth vs. micro-grooved categories. Fretting and corrosion damage at the head/neck junction was characterized using a modified semi-quantitative adapted from the Goldberg method by three independent observers. This method separated corrosion damage into four visually determined categories: minimal, mild, moderate and severe damage. Results. Mild to severe damage (Fretting Corrosion Score ≥ 2) was observed in 75% of the 120 CoCr femoral heads (78% of the heads mated with micro-grooved stems (47/60), Fig. 1A) and 72% of the heads mated with smooth stems (43/60, Fig 1B). Fretting and corrosion damage was not significantly different between the two cohorts when evaluated at the CoCr femoral head bore (p =0.105, Mann Whitney test, Fig. 2A) or the male stem tapers (p =0.428, Fig. 2B). No implant or patient factors were associated with fretting corrosion; corrosion scores were not significantly associated with stem alloy in the two cohorts (p=0.669, Mann-Whitney test). Discussion. The results of this matched cohort retrieval study do not support the hypothesis that taper surfaces with micro-grooved stems exhibit increased in vivo fretting corrosion. We accounted for implant, patient, and clinical factors that may influence in vivo taper corrosion with the matched cohort design and by post hoc statistical analyses. However, this study is limited by the semi-quantitative method used for evaluating damage in these components. Therefore, additional research will be necessary to quantify the volume of metal release from these two cohorts. To view tables/figures, please contact authors directly

The poor outcome of large head metal on metal total hip replacements (LHMOMTHR) in the absence of abnormal wear at the articulating surfaces has focussed attention on the trunnion / taper interface. The RedLux ultra-precision 3D form profiler provides a novel indirect optical method to detect small changes in the form and surface finish of the head taper as well as a quantitative assessment of wear volume. This study aimed to assess and compare qualitatively the tapers from well functioning small diameter, with poorly functioning LHMOMTHR's using the above technique. Method. 3 groups of retrieval tapers were analysed (Group 1: 28 mm CoCr heads from well functioning MOMTHRs (n=5); Group 2: Large diameter CoCr heads from LHMOMTHRs revised for failure secondary to adverse reaction to metal debris (n=5); Gp 3 (control): 28 mm heads from well functioning metal on Polyethylene (MOP) THRs; n=3). Clinical data on the retrievals was collated. The Redlux profiling of modular head tapers involves a non direct method whereby an imprint of the inside surface of a modular head is taken, and this is subsequently scanned by an optical non contact sensor using dedicated equipment [1]. The wear was also measured on the bearing surface [1]. RedLux profiling of the tapers produced a taper angle and 3D surface maps. The taper angles obtained with the Redlux method were compared to those obtained using CMM measurement on 3 parts. The Redlux profiling, including imprints, was also repeated 3 times to gauge potential errors. Results. There was no difference in mean 12/14 taper angles between groups. There was no difference in volumetric and linear wear at the bearing surface between groups. Only the LHMOMs showed transfer of pattern from the stem to the internal head taper, with clear demarcation of the contact and damaged area between head taper and stem trunnion (see figure 1 – interpretation of head taper surface features demonstrated using Redlux optical imaging). 3D surface mapping demonstrated wear patterns compatible with motion or deformations between taper and trunnion in the LHMOM group. These appearances were not seen in tapers from small diameter MOM and MOP THRs (see Figure 2). Discussion. Differences in appearance of the taper surface between poorly functioning LHMOMTHRs and well functioning MOP or MOM small diameter devices highlight an area of concern and potential contributor to the mode of early failure. Further work is required to fully qualify the Redlux method capabilities, and to understand the origin of the damage seen on those tapers, and the possible partial contribution of damage caused during retrieval

Arthroplasty registries are important for the surveillance of joint replacements and the evaluation of outcome. Independent validation of registry data ensures high quality. The ability for orthopaedic implant retrieval centres to validate registry data is not known. We analysed data from the National Joint Registry for England, Wales and Northern Ireland (NJR) for primary metal-on-metal hip arthroplasties performed between 2003 and 2013. Records were linked to the London Implant Retrieval Centre (RC) for validation. A total of 67 045 procedures on the NJR and 782 revised pairs of components from the RC were included. We were able to link 476 procedures (60.9%) recorded with the RC to the NJR successfully. However, 306 procedures (39.1%) could not be linked. The outcome recorded by the NJR (as either revised, unrevised or death) for a primary procedure was incorrect in 79 linked cases (16.6%). The rate of registry-retrieval linkage and correct assignment of outcome code improved over time. The rates of error for component reference numbers on the NJR were as follows: femoral head category number 14/229 (5.0%); femoral head batch number 13/232 (5.3%); acetabular component category number 2/293 (0.7%) and acetabular component batch number 24/347 (6.5%). . Registry-retrieval linkage provided a novel means for the validation of data, particularly for component fields. This study suggests that NJR reports may underestimate rates of revision for many types of metal-on-metal hip replacement. This is topical given the increasing scope for NJR data. We recommend a system for continuous independent evaluation of the quality and validity of NJR data. Cite this article: Bone Joint J 2015;97-B:10–18

Objective. We explanted NeuFlex metacarpophalangeal (MP) joint prostheses to identify common features, such as position of fracture, and thus better understand the reasons for implant failure. Methods. Explanted NeuFlex MP joint prostheses were retrieved as part of an-ongoing implant retrieval programme. Following revision MP joint surgery the implants were cleaned and sent for assessment. Ethical advice was sought but not required. The explants were photographed. The position of fracture, if any, was noted. Patient demographics were recorded. Results. Thirty NeuFlex MP explants were available. Seven (23%) were not fractured. Eleven explants (37%) had fractured at the hinge; nine (30%) had fractured at the junction of the distal stem and hinge; and three (10%) had fractured at both the hinge and distal stem. NeuFlex MP joint explants ranged in size from 0 to 40. Smaller sizes were retrieved from smaller fingers; larger implants came from the middle and index fingers. The age at revision ranged from 43 to 81 (median 58) years. Time in vivo ranged from 6 to 120 (median 58.5) months. All but two implants were obtained from rheumatoid joints, the remainder had osteoarthritis. Discolouration of some explants had occurred; other explants appeared to show no colour change. Conclusions. This is the first report of the position of fracture of NeuFlex explants. It is also the largest report of silicone arthroplasty explants. The majority (77%) had fractured. Nine (30%) NeuFlex explants had fractured at the junction of the distal stem and hinge; the typical position seen with Swanson and Sutter/Avanta MP joint explants. Eleven (37%) fractured across the hinge; this has not previously been reported although has been seen in in vitro testing. The hinge is thinner than the hinge-stem junction so may be at risk of more rapid failure, however the median time in vivo for hinge fractures was 63 months as opposed to 54 months for fractures at the distal stem. Intriguingly, 3 (10%) NeuFlex explants suffered fractures both at the hinge and at the junction of the distal stem and hinge which has also never been reported previously. Fracture at the junction of the distal stem and hinge shows the importance of subluxing forces in rheumatoid MP joints and therefore suggests these need to be mitigated as much as possible. Fracture across the hinge could indicate this as a position which could be increased in thickness, to increase the time taken to fracture, although there may be a concomitant increase in stiffness of the implant. With improved designs, patients might suffer fewer or later failures. The latest Norwegian Arthroplasty Registry report shows that revision MP joint arthroplasties accounted for 42% of all MP joint replacement operations in 2015. Therefore, this is an important area where opportunities exist to reduce revision rates

Introduction. Contemporary total knee systems accommodate for differential sizing between femoral and tibial components to allow surgeons to control soft tissue balancing and optimize rotation. One method some manufacturers use to allow differential sizing involves maintaining coronal articular congruency with a single radius of curvature throughout sizes while clipping the medial-lateral width, called a single coronal geometry system. Registry data show a 20% higher revision rate when the tibial component is smaller than the femur (downsizing) in the DePuy PFC system, a single coronal system, possibly from increased stresses from edge loading or varying articular congruency. We examined a different single coronal geometry knee system, Smith & Nephew Genesis II, to determine if edge loading is present in downsized tibial components by measuring area and location of deviation of the polyethylene articular surface damage. Methods. 45 Genesis II posterior-stabilized polyethylene inserts (12 matched and 33 downsized tibial components) were CT scanned. 3D reconstructions were registered to corresponding pristine component reconstructions, and 3D deviation maps of the retrieved articular surfaces relative to the pristine surfaces were created. Each map was exported as a point cloud to a custom MATLAB code to calculate the area and weighted center of deviation of the articular surfaces. An iterative k-means clustering algorithm was used to isolate regions of deviation, and a shrink-wrap algorithm was applied to calculate their areas. The area of deviation was calculated as the sum of all regions of deviation and was normalized to the area of the articular surface. The location of deviation was described using the weighted center of deviation and the location of maximum deviation on the articular surfaces relative to the center of the post (Fig. 1). Pearson product moment correlations were conducted to examine the correlation between length of implantation (LOI) and the medial and lateral areas of deviation for all specimens, matched components, and downsized components. Results. The mean LOIs for downsized and matched tibial components were not different (36±28 months vs 46±26 months, p=0.24). Areas of deviation for the medial and lateral sides for both downsized and matched components increased with LOI (p<0.001). Medial and lateral sides of matched retrievals were not different in location of maximum deviation, maximum deviation, and weighted center of deviation (p>0.4). The matched and downsized retrievals did not have different centers of deviation in the medial-lateral direction, maximum deviations, or locations of maximum deviations (p>0.1). Discussion. Our results suggest that downsizing the tibial component in the Genesis II system, a single coronal geometry system, did not affect the area or location of deviation on the articular surface. Overall, the weighted center of deviation remained close to the dwell point and did not change as a function of tibial downsizing. However, we saw deviation patterns biased peripherally for inserts with low LOI in both matched and downsized cohorts. With increasing LOI, the deviation expanded to cover the majority of the available articular surface. Our results suggest the need to further examine this and other systems determine the effects of differential sizing. For figures/tables, please contact authors directly.

Introduction. The Precice nail is the latest intramedullary lengthening nail with excellent early outcomes. Implant complications have led to modification of the nail design. The aim of this study was to perform a retrieval study of Precice nails following lower limb lengthening. To assess macroscopic and microscopic changes to the implants and assess differences following design modification, with identification of potential surgical, implant and patient risk factors. Method. 15 nails were retrieved from 13 patients following lower limb lengthening. Macroscopic and microscopic surface damage to the nails were identified. Further analysis included radiology and micro-CT prior to sectioning. The internal mechanism was then analysed with Scanning Electron Microscopy and Energy Dispersive X-ray Spectroscopy to identify corrosion. Results. 7 male and 3 females underwent 12 femoral lengthenings, 9 antegrade and 3 retrograde. 3 females underwent tibial lengthening. All patients obtained the desired length with no implant failure and full regenerate consolidation. Surface degradation was noted on the telescopic part of every nail design, less on the latest implants. Microscopic analysis confirmed fretting and pitting corrosion. Following sectioning black debris was noted in all implants. The early designs were found to have fractured actuator pins and the pin and bearings had evidence of corrosive debris. The latest designs had evidence of biological deposits suggestive of fluid ingress within the nail. Conclusion. This study suggests fluid ingress occurs with every generation of Precice nail despite modifications. The presence of biological fluid could be an early warning sign of potential corrosion. This in theory could lead to actuator pin fracture and implant failure. The clinical relevance is the potential re-use of a “dormant” nail in patients requiring secondary limb segment lengthening. Retraction of the nail in-situ and re-use for further lengthening requires careful consent for potential implant failure

While there are many variation laboratory and clinical studies using metal-on-metal (MOM) bearings after introduction of the 28mm MOM THR in 1988, the mapping of wear phenomena in such retrieval cases has been mimimal. In laboratory study, 28mm MOM bearing’s wear-rate was low with “run-in” and “steady-state” than large diameter MOM without theory of fluid-filum lubrication. In clinical results were not superior to the same way of laboratory study. We present a detailed analysis of 33 retrieved MOM hip bearings with 1–11 years follow-up,. We compiled 33 retrieval cases (MetasulTM: Zimmer/CenterPulse Inc., Austin, TX) including clinical information, ion concentrations from ball diameters, cup designs and stripe wear damage. The bearing surfaces were mapped using reflected light microscope (RLM), white light interferometer (Zygo Newview 600, Zygo.) and SEM(XL-30 FEG). Wear maps were constructed according to types of surface wear identified. Patients ranged from 36 to 76 years of age (Means: 56.9 years); 54% were males. Main causes for revision were progressive radiographic lines around the cups, osteolysis and pain. The 28mm ball diameter was used in 86% of cases (largest = 52mm ball). The CoCr liner incorporated a polyethylene adaptor in 75% of cases. Cup diameter > 50mm was present in 75% of cases. Eight femoral stems were recovered and all showed major impingement marks around the neck and five also had a metallosis (Mode-4A). Stripe wear was evident on 71% of CoCr balls with medial stripes twice as common as lateral. Stripe wear was identified in 25% of CoCr liners and extended 25–160° circumference around the liners. Clear liner rim damage was present in 10 (30%) and 3 demostrated severe damage of polyethelene adaptors. There are many limitations to such retrieval studies. These data are biased to cases that failed due to hip pain, radiographic signs of progressive osteolysis and some with high levels of metal ions. There was also the bias of having predominantly a CoCr sandwich design (polyethylene adaptor in 75% of cases). In early 1980s, the thin walled UHMWPE cup was introduced and used larger diameter balls for decreased risk of dislocation. However, unfortunally these big-ball cups produced significant PE wear debris, and diameter trends were returned to the Chanley’s small-ball paradigm again. In the same time (late of 1980’s), these second-generation MOM (28,32mm) was introduced for low wear characteristics alternate THR bearings, with sacrificing of joint stability and motion range. However, use of the small ball added well-known risks of impingement, subluxation and dislocation with rigid cups. In this study, using the ‘damage modes’ from McKellop, normal mode-1 wear occurred in only 14% of cases whereas modes 2–4 had an incidence approaching 30% each and signs of cup impingement were evident in 64% of cases. Thus summarizing MOM wear phenomena in “small” 28mm sandwich cup designs, there was retrieval evidence showing that damage modes 2–4 likely placed these patients at risk for adverse wear effects

The poor outcome of large head metal on metal total hip replacements (LHMOMTHR) in the absence of abnormal wear at the articulating surfaces has focussed attention on the trunnion/taper interface. The RedLux ultra-precision 3D form profiler provides a novel indirect optical method to detect small changes in form and surface finish of the head taper as well as a quantitative assessment of wear volume. This study aimed to assess and compare qualitatively the tapers from small diameter with LHMOMTHR's. 3 groups of retrieval tapers were analysed (Group 1: 28mm CoCr heads from MOMTHRs (n=5); Group 2: Large diameter CoCr heads from LHMOMTHRs (n=5); Group 3: 28mm heads from metal on polyethylene (MOP) THRs; n=3). Clinical data on the retrievals was collated. Both bearing surfaces and head tapers were measured for wear using the Redlux profiling non contact measurement system. Measurements included taper angle and 3D surface maps. Taper angles obtained with the Redlux method were compared to those obtained using CMM measurement on 3 parts. The Redlux profiling, including imprints, was also repeated 3 times to gauge potential errors. There was no difference in mean 12/14 taper angles between groups. There was no difference in volumetric and linear wear at the bearing surface between groups. Only the LHMOMs showed transfer of pattern from the stem to the internal head taper, with clear demarcation of the contact and damaged area between head taper and stem trunnion. 3D surface mapping demonstrated wear patterns compatible with motion or deformations between taper and trunnion in the LHMOM group alone. Discussion: Differences in appearance of the taper surface between LHMOMTHRs and MOP or MOM small diameter devices highlight an area of concern and potential contributor to the mode of early failure. Further work is required to fully qualify the Redlux method capabilities

Four low-cost hip prostheses, explanted because of clinical failure within three years, were subjected to a retrieval analysis study to determine the cause of the early failure. The study aimed to determine whether the low-cost prosthesis was substandard and had consequently contributed to the need for early revision. The retrieval analysis included a photographic record, a fractographic examination, an analysis of the material composition of the components, and a mechanical property analysis. These investigations were done in accordance with the ASTM F561 standards. Results demonstrated substandard qualities in respect of all parameters analysed. We conclude that the inferior quality of these low-cost hip prostheses contributed appreciably to their early failure and revision

Introduction. Three-dimensional (3D) printing of porous titanium implants marks a revolution in orthopaedics, promising enhanced bony fixation whilst maintaining design equivalence with conventionally manufactured components. No retrieval study has investigated differences between implants manufactured using these two methods. Our study was the first to compare these two groups using novel non-destructive methods. Materials and methods. We investigated 16 retrieved acetabular cups divided into ‘3D printed’ (n = 6; Delta TT) and ‘conventional’ (n = 10; Pinnacle Porocoat). The groups were matched for age, time to revision, size and gender (Table 1). Reasons for revision included unexplained pain, aseptic loosening, infection and ARMD. Visual inspection was performed to evaluate tissue attachment. Micro-CT was used to assess clinically relevant morphometric features of the porous structure, such as porosity, depth of the porous layer, pore size and strut thickness. Scanning electron microscopy (SEM) was applied to evaluate the surface morphology. Results. Significant differences (p = 0.0002) were found for all morphometric parameters (Table 2). Microscopic analysis revealed uniform beads over the backside of conventional implants, due to the manufacturing technique (Figure 1a). Conversely, beads of random size were found on 3D printed implants, representing a by-product of the manufacturing process, where some starting powder particles are not completely fused together (Figure 1b). The two groups showed similar tissue attachment (3D printed 76.9 ± 27.1%; conventional 73.8 ± 12.2%; p = 0.2635). Conclusion. This was the first study to analyse retrieved 3D printed orthopaedic implants. Differences were found between these and conventional implants, but both literature and registry data do not suggest a short-mid-term clinical issue with 3D printed components. Similar tissue on growth suggested a comparable behaviour with bone in situ. The key difference is the presence of the particles on 3D printed implants, whose clinical significance needs to be investigated. For any figures or tables, please contact the authors directly

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

Ceramic-on-ceramic alumina bearings (ALX) have demonstrated low wear with minimal biological consequences for almost four decades. An alumina-zirconia composite (BIOLOX-DELTATM) was introduced in 2000 as an alternative ceramic. This contains well-distributed zirconia grains that can undergo some surface phase transformations from tetragonal to monoclinic. We analyzed 5 cases revised at 1–7 years to compare to our simulator wear studies. For the retrieved DELTA bearings, two important questions were. how much tetragonal to monoclinic transformation was there in the zirconia phase and. how much did the articular surfaces roughen, either as a result of this transformation or from formation of stripe wear zones?. The retrieval cases were photographed and logged with respect to clinical and revision details. The DELTA balls varied from 22mm to 36mm diameters. These had been mated with liner inserts varying by UHMWPE, BIOLOX-FORTE and BIOLOX-DELTA materials. Bearing features were analyzed for roughness by white-light interferometry, for wear by SEM, for dimensions by CMM and for transfer layers by EDS technique. Surface transformations on DELTA retrievals were mapped by XRD. The four combinations of 36mm diameter BIOLOX-FORTE and BIOLOX-DELTA were studied in a hip simulator, which was run in ‘severe’ micro-separation test mode to 5 million cycles. Wear rates, wear stripes, bearing roughness and wear debris were compared to the retrieval data. In two DELTA ball cases, there were conspicuous impingement signs, stripe wear and black metallic smears. It is to be noted that the metal transfer sites (EDS) appeared to be from the revision procedures. The retrieved balls run with alumina liners showed monoclinic phase peaking at 32% on the particular surface and internal bore. On the fracture surface of case 1, the monoclinic content had increased to 40%. Various surface roughness indices were assessed on the bearings. The polished articular surfaces averaged roughness (Sa) of the order 3 nm, representing extremely smooth surfaces. The main wear zone was only marginally rougher (5 nm). In contrast the stripe wear zones had roughness of the order 55–140 nm. In the laboratory, the DELTA bearings provided a 3–6 fold wear reduction compared to FORTE controls. Roughness of stripes increased to maximum 113nm on controls. Roughness of wear stripes showed FORTE with the highest and DELTA with the lowest values. DELTA bearings also revealed much milder wear by SEM imaging. Phase transformations showed peaks at < 30% for both main wear zone and stripe wear sites. It is hypothesized that the concentration of monoclinic phase reached a certain level due to compression contraint imposed by the alumina matrix. With implant wear, additional tetragonal grains of zirconia are exposed and these will also transform to tetragonal. This consistency between laboratory and retrieval studies confirmed the stable nature of the bearings. The BIOLOX-DELTA combination provides optimal potential for a clinically relevant reduction in stripe wear

NHS Greater Glasgow & Clyde has six hospitals that provide an inpatient trauma service, but only two have facilities to receive patients by helicopter. The Southern General Hospital contains regional Neurosurgical and Spinal Injuries services and attracts the majority of major trauma delivered by helicopter. This study explores the impact that Emergency Medical Retrieval (EMRS) and Air Ambulance services have on the Trauma & Orthopaedic department at our Hospital. We examined the period 1. st. January 2010 to 31. st. December 2010 identifying Trauma & Orthopaedic admissions brought to our hospital by the Emergency Medical Retrieval and Air Ambulance services. These patients were identified from records kept by our Trauma Nurse Practitioner and an additional search of the hospital admissions database. Details of the admissions were extracted from this database, clinical records and various electronic patient records. Patients admitted to other departments were excluded from the study. 48 admissions (30 male, 18 female) were identified. Age ranged from 16-87 years. 16 patients had multiple injuries. 8 required High-Dependency or Intensive Care admission and there was 1 death in our cohort. 21 patients required surgery. In total, these patients required approximately 52.5 hours of operative time. These patients accounted for 373 inpatient days with an average hospital stay of 7.7 days (1-36 days). In addition, 25 patients have required a total of 35 outpatient appointments to date. This study quantifies the significant impact on inpatient and outpatient Trauma & Orthopaedic services from helicopter derived admissions. Some patients admitted under Neurosurgery and Spinal Injuries also undergo surgery, but were not included in the study, representing an additional workload. We believe this study supports an argument for additional investment in this growing trauma service, especially given the recent expansion of EMRS to cover the whole of Scotland

Dual Mobility (DM) Total Hip Replacements (THRs) were introduced to reduce dislocation risk, which is the most common cause of early revision. The in-vivo mechanics of these implants is not well understood, despite their increased use in both elective and trauma settings. Therefore, the aim of this study was to comprehensively assess retrieved DM polyethylene liners for signs of damage using visual inspection and semi-quantitative geometric assessment techniques.

Retrieved DM liners (n=20) were visually inspected for the presence of seven established modes of polyethylene damage. If embedded debris was identified on the external surface, its material composition was characterised using energy-dispersive x-ray analysis (EDX). Additionally, each liner was geometrically assessed for signs of wear/deformation using a validated methodology.

Visual inspection of the liners revealed that scratching and pitting were the most common damage modes on either surface. Burnishing was observed on 50% and 15% of the internal and external surfaces, respectively. In addition, embedded debris was identified on 25% of the internal and 65% of the external surfaces. EDX analysis of the debris identified several materials including iron, titanium, cobalt-chrome, and tantalum. Geometric analysis demonstrated highly variable damage patterns across the liners.

The results of this study provide insight into the in-vivo mechanics of DM bearings. For example, the results suggest that the internal bearing (i.e., between the head and liner) acts as the primary articulation site for DM-THRs as evidenced by a higher incidence of burnishing and larger, more concentrated regions of penetration across the liners’ internal surfaces. Furthermore, circumferential, and crescent-shaped damage patterns were identified on the articulating surfaces of the liners thus providing evidence that these components can rotate within the acetabular shell with varying degrees of mobility. The mechanics of DM bearings are complex and may be influenced by several factors (e.g., soft tissue fibrosis, patient activities) and thus further investigation is warranted.

Finally, the results of this study suggest that DM liners may be susceptible to ex-vivo surface damage and thus caution is advised when handling and/or assessing these types of components.

Dual mobility (DM) total hip replacements (THRs) were introduced to reduce dislocation risk, which is the most common cause of early revision. Although DM THRs have shown good overall survivorship and low dislocation rates, the mechanisms which describe how these bearings function in-vivo are not fully understood. Therefore, the study aim was to comprehensively assess retrieved DM polyethylene liners for signs of damage using visual inspection and semi-quantitative geometric assessment methods.

Retrieved DM liners (n=18) were visually inspected for the presence of surface damage, whereby the internal and external surfaces were independently assigned a score of one (present) or zero (not present) for seven damage modes. The severity of damage was not assessed. The material composition of embedded debris was characterised using energy-dispersive x-ray analysis (EDX). Additionally, each liner was geometrically assessed for signs of wear/deformation [1].

Scratching and pitting were the most common damage modes on either surface. Additionally, burnishing was observed on 50% of the internal surfaces and embedded debris was identified on 67% of the external surfaces. EDX analysis of the debris identified several materials including titanium, cobalt-chrome, iron, and tantalum. Geometric analysis demonstrated highly variable damage patterns across the liners.

The incidence of burnishing was three times greater for the internal surfaces, suggesting that this acts as the primary articulation site. The external surfaces sustained more observable damage as evidenced by a higher incidence of embedded debris, abrasion, delamination, and deformation. In conjunction with the highly variable damage patterns observed, these results suggest that DM kinematics are complex and may be influenced by several factors (e.g., soft tissue fibrosis, patient activities) and thus further investigation is warranted.

3D printing acetabular cups offers the theoretical advantage of enhanced bony fixation due to greater design control of the porous implant surfaces. Analysing retrieved 3D printed implants can help determine whether this design intent has been achieved.

We sectioned 14 off-the-shelf retrieved acetabular cups for histological analysis; 7 cups had been 3D printed and 7 had been conventionally manufactured. Some of the most commonly used contemporary designs were represented in both groups, which were removed due to either aseptic loosening, unexplained pain, infection or dislocation. Clinical data was collected for all implants, including their age, gender, and time to revision.

Bone ingrowth was evaluated using microscopic assessment and two primary outcome measures: 1) bone area fraction and 2) extent of bone ingrowth.

The additively manufactured cups were revised after a median (IQR) time of 24.9 months (20.5 to 45.6) from patients with a median (IQR) age of 61.1 years (48.4 to 71.9), while the conventional cups had a median (IQR) time to revision of 46.3 months (34.7 to 49.1, p = 0.366) and had been retrieved from patients with a median age of 66.0 years (56.9 to 68.9, p = 0.999).

The additively and conventionally manufactured implants had a median (IQR) bone area fraction of 65.7% (36.4 to 90.6) and 33.9% (21.9 to 50.0), respectively (p < 0.001).

A significantly greater amount of bone ingrowth was measured into the backside of the additively manufactured acetabular cups, compared to their conventional counterparts (p < 0.001). Bone occupied a median of 60.0% and 5.7% of the porous depth in the additively manufactured and conventional cups, respectively.

3D printed components were found to achieve a greater amount of bone ingrowth than their conventionally manufactured counterparts, suggesting that the complex porous structures generated through this manufacturing technique may encourage greater osteointegration.

Aseptic loosening of the glenoid after total shoulder replacement is a challenging problem to manage clinically. In the right circumstances, arthroscopic retrieval of loose polyethylene glenoids can be a valuable tool in the shoulder surgeon's repertoire for dealing with this uncommon problem. The purpose of this talk is to demonstrate the technique for arthroscopic removal of a loose glenoid and review the clinical circumstances where this procedure may play a valuable role

Introduction. This study was performed to investigate the failure mechanism of one specific hip arthroplasty cup design that has shown a high clinical failure rate. The aim of this study was to identify general design problems of this polyethylene inlay. Material and Methods. 55 consecutive retrievals of a cementless screw ring (Mecron) were collected. In any case a 32 mm ceramic head was used. All implants failed due to aseptic loosening. The follow-up of the implants was 3 to 16 years. We recorded backside wear, fatigue of the polyethylene at the flanges on the outer rim and at the cup opening (32 mm inner diameter). To assess the deformation of the inlay, the smallest and the median diameter of the cup opening were measured using a 3 dimensional coordinate measuring machine (Multisensor, Mahr, Germany). Results. 90% of the explants showed signs of wear on the backside of the inlay. Another typical and so far not described alteration was collar fatigue in 68%. 38% of the inlays showed rim creep: Examples for Backside wear, collar fatigue and rim creep are illustrated in Fig. 1. 90% had a diameter of 32.1 mm or less, and even 46% had a diameter less than 32 mm. Discussion. The investigated design is at the lower limit of the allowed machining tolerance of the cup opening (32 + 0.1 mm) and has no additional clearance (which some manufacturers add). It seems that the inlays yield at the dome because of the viscoelastic properties of polyethylene and the open dome area of the attached screw ring. This leads to excessive wear at the dome area and it triggers a “brake drum” effect at the cup opening. Thereby torsional stresses at the implant bone interface increase which lead to failure of the implant. To avoid this type of failure, PE inlays should have enough clearance at the cup opening and the inlay should have dome contact to the closed metal shell

FDA approval of metal-on-metal (MOM: 28, 32mm) bearings has provided 10 years of clinical experiences in USA. However there has been no detailed mapping of wear phenomena in retrieval cases. We present an analysis of 28 cases, MOM retrievals with 1 to 10 years follow-up, radiographic reviews and metal ion studies. Ball diameters ranged from 28mm to 42mm. Two balls were the early design with skirts. Main indicators for revision were the progressive radiographic changes indicative of osteolysis, with associated hip pain. Approximately 54% of patients were males and ages ranged from 36 to 76 years of age. Only 7 femoral stems were recovered but all had impingement marks. Only three cases lacked any evidence of stripe wear and these were in very elderly patients. Approximately 85% of these cases showed some evidence of stripe wear and multiple stripes were clearly visible on 50% of the femoral balls. The medial ball stripes were twice as common as lateral. Stripe wear was identified in 25% of CoCr liners. In the hip simulator studies generally show ‘run-in’ wear rates of 1–7mm3 per million cycles (Mc). We noted that above the 5mm3/Mc threshold, the serum generally appeared black. In contrast, the ‘steady-state’ wear rates of 0.1–1.6 mm3/Mc showed the true potential of MOM bearings. However there were often examples of higher wear (7–20 mm3/Mc), which gave confounding trends in published studies. Our studies of metal ions in the simulator lubricant provided a very accurate representation of MOM wear. There are many limitations in comparing in-vitro to in-vivo wear performance. Our retrieval data are biased to cases that failed due to hip pain, had radiographic signs of progressive osteolysis and some showed high levels of metal ions. There was also the bias of having predominantly a CoCr sandwich design (polyethylene adaptor). Use of the small ball added the well-known risks of impingement, subluxation and dislocation with rigid cups. Using the ‘damage modes’ from McKellop, we found only normal Mode-1 wear to be rare in these cases, whereas Modes# 2–4 had an incidence approaching 30% each. Signs of impingement were evident in 85% of our cases. Thus summarizing these MOM wear phenomena in retrieved 28mm sandwich cups, the evidence implicated impingement and 3rd-body wear modes (#2–4) as the clinical risk for adverse wear effects at 10 years follow-up. The in-vitro wear studies have not yet simulated such adverse clinical effects

Trunnionosis is an important failure mechanism of total hip arthroplasties as has recently been reported by the England and Wales national joint registry. Adverse local tissue reaction has also recently been associated with total hip arthroplasty (THA) with metal on polyethylene and ceramic on polyethylene articulations. The contributing factors in the mechanism of this failure pattern have not been elucidated, however they are likely multifactorial to include corrosion, fretting, taper design, implantation time, metal particulate debris, and wear at the metal on metal interface. Furthermore, dissimilar metallic combinations have been shown to exacerbate tribocorrosion. Authors have also reported on the use of ceramic heads to reduce trunniononis, however, tribocorrosion is still present. The majority of the literature regarding modular head neck taper fretting and corrosion involves cobalt chrome (CoCr) alloy. Little is known about head neck fretting corrosion with Oxinium femoral heads. To measure fretting, corrosion, and wear on the female tapers of retrieved Oxinium femoral heads and to determine how demographic and device factors affect these measurements. Ninety-two (92) retrieved 12/14 Oxinium heads were graded using the modified Goldberg score for subjectively grading corrosion and fretting on the taper surface. A novel silicone molding technique was validated, then applied to the female tapers of the retrievals and of two pristine Oxinium femoral heads, sizes 32+0 and 32+4. The molds were scanned using a Konica Minolta 3D laser scanner for reconstruction of the topography, dimensions, and surface features of the tapers. Geomagic software was used to align the retrieved to the pristine 3D models, allowing measurement of surface deviations (from wear) that had occurred while the heads were implanted. Patient demographic and implant data were correlated with Goldberg scores and wear deviations. The mean Goldberg score was 1.6. Goldberg scores of 1 (minimal), 2 (mild), and 3 (moderate) were present in 41 of the 92 heads (45%), 43 heads (47%), and 8 heads (8%) respectively. No implants received a score of 4 (severe). A positive significant correlation was found between length of implantation and increased female taper fretting (R = 0.436, p < 0.01). Wear deviations were significantly greater with 36mm heads compared to 32mm heads (p < 0.01) and with +4 offsets compared to 0 offsets (p = 0.013). Similar to previous work analyzing ceramic heads, Oxinium heads demonstrated predominately mild tribocorrosion grades, however do not eliminate tribocorrosion. Tribocorrosion was increased with large heads and increased offsets. This finding is consistent perhaps with greater mechanical burden that larger implants with increased offsets experience. Further investigation is needed to elucidate if Oxinium femoral heads reduce fretting and corrosion when compared to CoCr femoral heads

Increased modularity of total hip arthroplasty components has occurred, with theoretical advantages and disadvantages. Recent literature indicates the potential for elevated revision rates of modular neck systems and the potential for metallosis and ALVAL (Aseptic Lymphocyte dominated Vasculitis Associated Lesion) formation at the modular neck/stem site. Retrieval analysis of one modular neck implant design including SEM (Scanning Electron Microscopy) assessment was done and correlated to FEA (Finite Element Analysis) as well as clinical features of patient demographics, implant and laboratory analysis. Correlation of the consistent corrosion locations to FEA indicates that the material and design features of this system may result in a biomechanical reason for failure. The stem aspect of the modular neck/stem junction may be at particular risk

Introduction. Wear debris generation in metal-on-metal (MOM) total hip arthroplasty (THA) has emerged as a compelling issue. In the UK, clinically significant fretting corrosion was reported at head-taper junctions of MOM hip prostheses from a single manufacturer (Langton 2011). This study characterizes the prevalence of fretting and corrosion at various modular interfaces in retrieved MOM THA systems used in the United States. Methods and Materials. 106 MOM bearing systems were collected between 2003 and 2012 in an NIH-supported, multi-institutional retrieval program. From this collection, 88 modular MOM THA devices were identified, yielding 76 heads and 31 stems (22 modular necks) of 7 different bearing designs (5 manufacturers) for analysis. 10 modular CoCr acetabular liners and 5 corresponding acetabular shells were also examined. Mean age at implantation was 58 years (range, 30–85 years) and implantation time averaged 2.2 ± 1.8 years (range, 0–11.0 years). The predominant revision reason was loosening (n=52). Explants were cleaned and scored at the head taper, stem taper, proximal and distal neck tapers (for modular necks), liner, and shell interfaces in accordance with the semi-quantitative method of Goldberg et al. (2002). Results. Fretting and corrosion were observed on 68/76 (89%) head tapers, 21/31 (68%) stem tapers, 15/22 (68%) proximal modular neck tapers, 20/22 (91%) distal modular neck tapers, 10/10 (100%) modular liners and 5/5 (100%) modular shells. Scores were lower at proximal stem tapers than within the head tapers (p = 0.001) but were positively correlated (ρ = 0.56, p = 0.001). At the head-neck interface, significantly more damage was noted on head tapers of devices with modular necks (p<0.001). At the neck-stem interface, damage to modular necks was localized at the curved medial and lateral surfaces. A significant correlation was observed between implantation time and corrosion/fretting score at this region (ρ = 0.78, p < 0.001). Damage was noted at all shell-liner interfaces, manifested primarily as scratching with discoloration on the backside rim of liners and circular fretting patterns on shells. Discussion. These results support the inclusion of fretting and corrosion evaluation in standardized MOM retrieval inspection protocols. Adaptation of the method developed by Goldberg and colleagues is suitable for the variety of modular connections in contemporary MOM THA implants, which may incorporate modular femoral and/or acetabular components. Further quantitative assessment of wear at modular interfaces of retrieved MOM devices is therefore warranted

Introduction. Detailed analysis of retrieved total hip replacements (THRs) is valuable for assessing implant and material successes and failures. Reduction of bearing wear and corrosion and fretting of the head-neck trunnion is essential to implant durability and patient health. This research quantifies and characterizes taper and bearing surface damage on retrieved oxidized zirconium THRs. Methods. Initially, 11 retrieved oxidized zirconium femoral heads were examined along with their associated femoral stems. Relevant patient and retrieval data was collected from clinical charts and radiographs. Taper corrosion (Figure 1) and fretting damage (Figure 2) scoring was performed following the Dyrkacz [1] method. A coordinate measuring machine was used to obtain a detailed surface map of the male and female taper surfaces. Taper surface maps were best-fit with an idealized cone followed by volume subtraction to quantify the amount of material removed as a result of fretting and corrosion processes. Scanning electron microscopy was performed on select samples to identify specific damage modes. Unique surface bumps were noted on the articular surface of select femoral heads (Figure 3). Seventeen femoral heads were added to the analysis specifically for identification of these bumps. Articular surfaces were searched under SEM magnification and bumps were identified and counted. Parametric statistical correlations were performed with SAS v9.3. Results. Mean patient age was 61 years (Range: 35–95) with mean implantation period being 2.0 years (Range: 0.1–11.4) and mean body mass index of 29 kg/m. 2. (Range: 22–46). Revision for infection (n=11), peri-prosthetic fracture (n=5) and dislocation (n=5) were the main reasons for revision. Mean corrosion damage scores were 2.0 and 3.6 (head, neck) while mean fretting damage scores were 8.5 and 5.8 (head, neck). Fretting damage score was weakly correlated with implantation period (p=0.07) while corrosion damage score was not. Mean corrosion and fretting volume measured 0.40 mm. 3. and 0.87 mm. 3. (head, neck). Volume of corrosion and fretting damage did not correlate with implantation period; however neck volume correlated with inclination angle of the acetabular cup (p<0.01). Bearing diameter was not found to correlate with corrosion and fretting damage score or volume. The unique surface bumps were identified in 12 of 28 samples, with 3 samples having <10 bumps. Presence of these bumps did not appear to be related to bearing diameter, implantation period, or any damage metrics. Conclusion. Fretting damage was found to correlate with implantation period, suggesting that is a continuous in vivo process; however, this was not found for corrosion damage. Fretting damage volume correlated with acetabular cup angle; however, this may be coincidence as only 8 samples were included in the analysis. Overall, our corrosion damage scores (2.0–3.6) were lower than previously published values for 28mm & 36mm cobalt-chrome heads (4.5–13.1) [1]. However, our fretting damage scores (5.8–8.5) were higher than previously published (2.8–4.4) [1]. Greater fretting damage on the oxidized zirconium heads may be explained by the softer zirconium alloy compared to that of cobalt-chromium. Further subsurface investigation of the surface bumps is underway using a focused ion beam mill

Introduction. There is considerable interest in the orthopaedic community in understanding the multifactorial process of taper fretting corrosion in total hip arthroplasty (THA). Previous studies have identified some patient and device factors associated with taper damage, including length of implantation, stem flexural rigidity, and head offset. Due to the complexity of this phenomenon, we approached the topic by developing a series of matched cohort studies, each attempting to isolate a single implant design variable, while controlling for confounding factors to the extent possible. We also developed a validated method for measuring material loss in retrieved orthopaedic tapers, which contributed to the creation of a new international standard (ASTM F3129-16). Methods. Based on our implant retrieval collection of over 3,000 THAs, we developed independent matched cohort studies to examine (1) the effect of femoral head material (metal vs. ceramic, n=50 per cohort) and (2) stem taper surface finish (smooth vs. microgrooved, n=60 per cohort). Within each individual study, we adjusted for confounding factors by balancing implantation time, stem taper flexural rigidity, offset, and, when possible, head size. We evaluated fretting and corrosion using a four-point semiquantitative score. We also used an out-of-roundness machine (Talyrond 585) to quantify the material loss from the tapers. This method was validated in a series of experiments of controlled material removal on never-implanted components. Results. In the first study, the ceramic cohort exhibited a 92% reduction in cumulative volumetric loss from both the head and neck taper surfaces compared to the CoCr cohort (p < 0.001). In the CoCr cohort, there was greater material loss from femoral head tapers as compared with stem tapers (p < 0.0001). There was also a correlation between visual scoring and volumetric material loss (ρ = 0.67, p < 0.01). In the second study, taper damage was not different between the smooth and microgrooved taper cohorts when evaluated at the head bore (p=0.14) or the stem tapers (p=0.35). There was also no difference in material loss between the most damaged CoCr heads in the two cohorts (p>0.05). Conclusions. Our findings suggest that fretting and corrosion damage and material loss from the stem taper are mitigated, and on the head taper, eliminated with the use of a ceramic vs. metal femoral head. We also found that fretting and corrosion damage was insensitive to differences in stem taper surface finish and the presence of microgrooves. Although visual scoring was effective for preliminary screening to separate tapers with no or mild damage from tapers with moderate to severe damage, it was not capable of discriminating within the large range of material loss observed at the taper surfaces with high fretting-corrosion scores. Thus, for moderate to severely damaged conical tapers, direct measurement is necessary. A drawback of a matched cohort approach is that a large retrieval collection is necessary to effectively match an investigational group of implants with an appropriate control cohort. Notwithstanding this limitation, the matched cohort approach has been an effective approach to study the complex multifactorial problem of taper fretting and corrosion

Squeaking is a rare complication of hard-on-hard hip bearings. Occasionally the noise is troublesome enough to warrant revision surgery. The purpose of this study is to contribute to the understanding of the mechanism(s) underlying squeaking. We analyzed 10 alumina ceramic-on-ceramic bearings from squeaking hips collected at revision surgery. The reason for revision was given as squeaking (6 cases) or squeaking and pain (4 cases). Six of the 10 patients were male, average patient age was 48. Bearings were retrieved after an average of 23 months in service (11 to 61 months). There were 4 different designs of acetabular component from 2 different manufacturers. Nine have an elevated metal rim which is proud of the ceramic and one does not. Two bearings were 36mm in diameter, 6 were 32mm and 2 were 28mm. All 10 bearings showed evidence of edge loading wear. Mean dimensions of the wear patch were 37mm by 12mm on the acetabular component and 32mm by 13mm on the femoral heads. Wear dimension was not related to bearing diameter. Seven of the 10 implants also had evidence of impingement of the femoral neck against the elevated metallic rim or the ceramic insert or both. There was no chipping or fracture of any of the ceramic components. Squeaking is a recently recognized complication of hard on hard bearing surface. This retrieval study is the first of its kind, to our knowledge attempting to unravel the mechanism of this undesirable complication. Although impingement seems to be present in majority of cases, the latter does not seem to be necessary. Edge loading wear was the common factor in all cases and this may prove to be a critical mechanism

Good short-term results with Mt Blanc uncemented acetabular cups have been previously reported. However, in the medium term, we have observed acetabular loosening related to large granulomatous lytic lesions. To determine the cause of the polyethylene load causing the granulomatous lytic lesions, we subjected six explanted Mt Blanc acetabular cups to retrieval analysis. We also reviewed the literature on polyethylene locking mechanisms in uncemented metal-backed cups and on the deformability of metal-backed cups. We subjected the retrieved cups to stereo-photographic analysis and to dye penetration and surface scanning electron microscopy techniques. We demonstrated severe polyethylene wear and particle generation on the back surface of the polyethylene insert. This was due both to two-body sliding wear, as characterised by surface deformation and delamination of the polyethylene, and to three-body abrasive wear, as characterised by surface roughness and embedded titanium particles. The literature confirmed that the locking mechanism of the Mt Blanc cup was particularly poor and the deformability greater than in other cups tested. This confirmed the wear patterns on the back-surface of the polyethylene liner. We caution against the use of uncemented cups that have poor locking mechanisms for the polyethylene liners and those that deform excessively. The combination of poor locking mechanisms and titanium shells is especially dangerous

Introduction. Thermally treated 1st generation highly crosslinked polyethylenes (HXLPE) have demonstrated reduced penetration and osteolysis rates, however, concerns still remain with respect to oxidative stability and mechanical properties of these materials. To address these concerns, manufacturers have introduced the use of antioxidants to quench free radicals while maintaining the mechanical properties of the HXLPE. Two common antioxidants are α-tocopherol (Vitamin-E) and pentaerythritol tetrakis (PBHP). These may be either mixed prior to consolidation, or diffused throughout the polymer after consolidation and irradiation. In vitrostudies have shown that these materials are oxidatively stable and have improved mechanical properties compared to 1st generation HXLPEs; however, few studies have investigated the in vivo performance of anti-oxidant stabilized HXLPE. The purpose of this study was to investigate the revision reasons, oxidation, and mechanical properties of retrieved short-term anti-oxidant HXLPE. Methods. Between 2010 and 2015, 73 anti-oxidant HXLPE components were collected as a part of an IRB approved, multi-institutional retrieval analysis program during routine revision surgery. Of the seventy-three components, 30 (41%) were acetabular liners, whereas, 43 were tibial inserts. The components were fabricated from three different materials: Vitamin-E Diffused HXLPE (n=30; E1, Biomet), Vitamin-E Blended (n = 41; Vivacit-E, Zimmer) and PBHP blended (n = 2, AOX, DePuy). The hip and knee components were implanted for 0.7 ± 0.8 years (Range: 0.0–2.25 years) and 0.8 ± 1.1 years (Range: 0.0–4.5 years), respectively. Implantation time, patient weight, age, gender, and activity levels were similar between hip and knee components (Table 1). For oxidation analysis, thin slices (∼200μm) were taken from medial condyle and central eminence of the tibial inserts or the superior/inferior axis from hip components. The slices were boiled in heptane for six hours to extract lipids absorbed in vivo. 3-millimeter FTIR line scans were taken perpendicular to the surface of interest, according to the ASTM F2102. Mechanical properties were assessed using the small punch test (ASTM F2183). Forty-three explants were available for destructive testing. Results. The predominant revision reasons were loosening, instability, and infection (Figure 1). Oxidation was low in both the hip and knee components (Mean OI≤0.1; Figure 2). For both tibial inserts and acetabular liners, there was no correlation between implantation time and oxidation indices (p>0.05). In the tibial inserts, the AP face had slightly higher oxidation indices than the articulating surface (Mean difference = 0.04; p=0.03). There was no difference in ultimate load between hips and knees at the surface (p=0.14) or the subsurface (p=0.38). Discussion. This study analyzed the revision reasons, oxidative stability, and mechanical properties of short-term retrieved 2nd generation HXLPE. The observations of this study show that anti-oxidant infused HXLPE exhibited low oxidative indices (Mean OI<0.1). There was no difference observed in the mechanical properties of these materials between hip and knee applications. However, this study is limited by short implantation times. This is unavoidable because the materials have only recently become clinically available. The data presented serves as a benchmark for future studies when longer-term retrieved implants become available

Background. Skeletal stem cells can be combined with human allograft, and impacted to produce a mechanically stable living bone composite. This strategy has been used for the treatment of femoral head avascular necrosis, and has been translated to four patients, of which three remain asymptomatic at up to three year follow-up. In one patient collapse occurred in both hips due to widely distributed and advanced AVN disease, necessitating bilateral hip arthroplasty. However this has provided the opportunity to retrieve the femoral heads and analyse human tissue engineered bone. Aims. Analysis of retrieved human tissue-engineered bone in conjunction with clinical follow-up of this translational case series. Methods. A parallel in vitro culture of the implanted cell-graft constructs was set up at the time of surgery, with serial cell viability stains performed up to six weeks. Patient follow-up was by serial clinical and radiological examination. Tissue engineered bone from the two retrieved femoral heads was analysed histologically by Alcian blue & Sirius red stain and bi-refringence, by micro computed tomography (microCT) for both bone density and morphology, and by compression testing for mechanical strength. Normal trabecular and cortical bone from the femoral heads was used as controls. Results. Parallel in vitro analysis demonstrated sustained cell growth and viability on the allograft. Histologically, the retrieved tissue engineered specimens demonstrated a mature trabecular micro-architecture and organization identical to normal trabecular bone. MicroCT revealed trabecular morphology within the tissue-engineered bone, with bone density of 1400 Grey scale units (compared to 1200 for natural trabecular bone and 1800 for cortical bone). Axial compression testing showed no difference in strength between engineered and trabecular bone. Conclusions. Widespread residual necrosis in the femoral heads of one patient resulted in collapse requiring hip arthroplasty, but analysis of the tissue engineered bone sections has demonstrated the translational potential of a living bone composite to restore both the biological and mechanical characteristics of bone defects. Clinical follow-up shows this to be an effective new treatment for focal early stage avascular necrosis of the femoral head, and this unique retrieval analysis data confirms the potential of cell-based strategies for clinical treatment of bone defects

Summary Statement. This study assesses oxidation, mechanical behavior and revision reasons of 2. nd. generation HXLPE used in total hip and knee arthroplasty. While oxidation was low for both X3 and E1 HXLPEs, oxidative regional variations were detected in the sequentially annealed cohort. Introduction. First generation highly crosslinked polyethylenes (HXPLEs) have proven successful in lowering both penetration and osteolysis rates. However, 1. st. generation annealing and remelting thermal stabilization have been associated with in vivo oxidation or reduced mechanical properties. Thus, 2. nd. generation HXLPEs were developed to improve oxidative stability while still maintaining material properties. Little is known about the in vivo clinical failure modes of these 2. nd. generation HLXPEs. The purpose of this study was to assess the revision reasons, wear, oxidative stability, and mechanical behavior of retrieved sequentially annealed Vitamin E diffused HXLPE in THA and TKA. Methods. 251 2. nd. Generation HXLPE hip and knee components were consecutively retrieved during revision surgeries and continuously analyzed in a prospective, IRB approved, multicenter study. 123 acetabular liners (Implanted 1.2y; Range 0–5.0y) and 117 tibial inserts (Implanted 1.6y; Range 0–5.8y) were highly crosslinked and annealed in 3 sequential steps (X3). Five acetabular liners (Implanted 0.6y; Range 0–2.0y) and six tibial inserts (Implanted 1.3y; Range 0.5–1.8y) were diffused with Vitamin E (E1). Patient information was collected from medical records. Linear penetration of liners was measured using a calibrated digital micrometer (accuracy: 0.001 mm). Surface damage of tibial components was assessed using the Hood method. Thin sections were taken from the acetabular liners (along the superior/inferior axis) and the tibial components (along the medial condyle and central spine) for oxidation analysis and analyzed according to ASTM 2102. Mechanical behavior was assessed via the small punch test (ASTM 2183). Results. The liners and tibial components fabricated from both HXLPEs were revised predominantly for loosening, instability, and infection. The average penetration rate for the Sequentially Annealed group was low (PR=0.045mm/yr). Pitting, scratching and burnishing were the predominant damage mechanisms of the tibial inserts within both material groups, with no evidence of delamination. Oxidation indices were low (Mean OI≤0.3) and similar between liners and inserts of the Sequentially Annealed components at the bearing and backside surface (p≥0.15). Oxidation was positively correlated with implantation time at the bearing surface of the Sequentially Annealed groups (Rho>0.29, p<0.005). The Ultimate Load of the Sequentially Annealed acetabular liners was statistically higher than the tibial components (p<0.001), however the mean difference was minimal (∼6N). Discussion. This study evaluated the properties of 2. nd. generation HXLPEs used in THA and TKA. Sequentially Annealed liners had penetration rates comparable with 1. st. generation HXLPEs. While oxidation was low for both sequentially annealed and Vitamin E HXLPEs, we were able to detect regional variations in the oxidative in the sequentially annealed cohort. Longer-term retrievals are necessary to fully assess the oxidative stability of Vitamin E diffused HXLPE used in TKA and THA

Purpose: This study was designed to establish the poly-ethylene wear rates in the Oxford medial unicompert-mental knee replacement. Introduction: The Oxford meniscal bearing knee was introduced as a design to reduce polyethylene wear. There has been one previous retrieval study of the Oxford UKA, which reported very low wear rates in some specimens, but abnormal patterns of wear in others, including impingement. There has been no further investigation of these abnormal wear patterns. Methods: Forty-seven bearings were retrieved from patients who had received a medial Oxford UKA for anteromedial osteoarthritis of the knee, none of which had previously been studied. Mean time to revision was 8.4 years (SD 4.1) and 20 had been implanted for over 10 years. The macroscopic pattern of polyethylene wear and the linear penetration (dial gauge measurement) was recorded for each bearing. Results: The mean linear penetration rate (LPR) was 0.07mm/year. The patterns of wear fell into 4 categories, each with a different LPR; 1) No abnormal macroscopic appearance, n=16 (LPR = 0.01mm/year), 2) Abnormal macroscopic wear with extra-articular impingement, n=16 (LPR = 0.05mm/year), 3) Abnormal macroscopic wear with intra-articular impingement, n=6 (LPR = 0.10mm/year), 4) Abnormal macroscopic wear with impingement and signs of incongruous articulation, n=9 (LPR = 0.14mm/year). The differences in LPR were statistically significant (p< 0.05). Conclusion: The results show that very low polyethylene wear rates are possible if the device functions normally. However if the bearing displays abnormal function (extra-articular, intra-articular impingement or incongruous articulation) wear rates increase significantly

Background:. Polyethylene wear in total knee arthroplasty (TKA) is influenced by patient, surgeon and implant factors. The objective of this study is to assess the effect of limb alignment, implant position and joint line position on the pattern of wear in posterior stabilized (PS) tibial inserts. Methods:. This was a retrieval analysis of 83 PS liners collected from patients who underwent revision surgery from 1999 to 2011. Inserts were divided into 16 zones and a microscopic analysis of surface damage was carried out. We determined overall damage with a scoring system. Pre-revisions radiographs were reviewed and analyzed for correlation with the wear profile. Results:. The mean age was 73 years old (range 45 to 96 years old) and the mean duration of implantation was 3.5 years (range 0.1 to 10.6 years). The most common reason for revision was infection (71%, 59 of 83 liners), followed by aseptic loosening (6%, 5 of 83 liners) and instability (6%, 5 of 83 liners). The most common mode of wear was burnishing, followed by abrasion and pitting. The total damage score was significantly higher in knees with postoperative varus alignment more than 3 degrees (p = 0.03). Postoperative varus alignment was associated with significantly more wear in the medial compartment (p = 0.03). The total damage score to the post was significantly more in knees with joint line elevation more than 5 mm (9.7 ± 3.9, compared to 6.5 ± 3.7 in knees with less joint line elevation) (p = 0.05). The most commonly affected compartment was the medial compartment. Conclusion:. Limb malalignment and implant malposition resulted in more wear in PS TKA

Introduction. The National Joint Registry (NJR) for England, Wales and Northern Ireland contributes important information on the performance of implants and surgeons. However, the quality of this data is not known. This study aimed to perform an independent validation of primary metal-on-metal hip procedures recorded on the NJR through linkage to the London Implant Retrieval Centre (LIRC). Patients/Materials & Methods. Primary, metal-on-metal hip arthroplasties performed between 1st April 2003 and 5th November 2013 were recruited from the NJR (n=67045). Retrieved, metal-on-metal components were recruited from the LIRC (n=782). Data linkage and validation checks were performed. Results. 476 procedures (60.9%) on the LIRC were successfully linked to the NJR. However, 306 procedures (39.1%) could not be linked. The outcome recorded by the NJR (as either revised, unrevised or death) for a primary procedure was incorrect in 79 linked cases (16.6%). The rate of registry-retrieval linkage and correct assignment of outcome code improved over time. The rates of error for component reference numbers on the NJR were: femoral head category number 14/229 (5.0%); femoral head batch number 13/232 (5.3%); acetabular component category number 2/293 (0.7%) and acetabular component batch number 24/347 (6.5%). Discussion. Registry-Retrieval linkage provided a novel means for data validation, particularly for component fields. This study suggests that NJR reports may underestimate revision rates for many types of metal-on-metal hip. This is topical given the increasing scope for NJR data. We recommend a system for continuous, independent evaluation of NJR data quality and validity

The early failure and revision of bimodular primary total hip arthroplasty prostheses requires the identification of the risk factors for material loss and wear at the taper junctions through taper wear analysis. Deviations in taper geometries between revised and pristine modular neck tapers were determined using high resolution tactile measurements. A new algorithm was developed and validated to allow the quantitative analysis of material loss, complementing the standard visual inspection currently used. The algorithm was applied to a sample of 27 retrievals (in situ from 2.9 to 38.1 months) of the withdrawn Rejuvenate modular prosthesis. The mean wear volumes on the flat distal neck piece taper was 3.35 mm. 3. (0.55 to 7.57), mainly occurring in a characteristic pattern in areas with high mechanical loading. Wear volume tended to increase with time to revision (r² = 0.423, p = 0.001). Implant and patient specific data (offset, stem size, patient’s mass, age and body mass index) did not correlate with the amount of material loss observed (p >  0.078). Bilaterally revised implants showed higher amounts of combined total material loss and similar wear patterns on both sides. The consistent wear pattern found in this study has not been reported previously, suggesting that the device design and materials are associated with the failure of this prosthesis. Cite this article: Bone Joint J 2015;97-B:1350–7

Purpose: A porous tantalum cylindrical shaped implant (Osteonecrosis Intervention Implant, Zimmer, Warsaw, IN) has been designed to provide subchondral bony support of the subchondral plate, be osteoconductive and allow revascularization of an osteonecrotic femoral head. This study evaluates retrieved implants obtained at the time of conversion to total hip arthroplasty to determine the ability of this device to fulfill its objectives. |. Methods: Eighteen femoral heads with the tantalum implant still in situ were evaluated with contact radiographs and scanning electron microscopy to assess femoral head and bony anatomy, bone growth into the implant and femoral head revascularization. Retrievals from 12 males and 6 females with an average age of 46 years old (range, 31–61) and Stage I or II osteonecrosis were evaluated. |. Results: At a mean of 13.4 months (range, 3–36) postoperatively, all femoral heads demonstrated subchondral collapse. The bone surrounding the implant remained necrotic with no evidence of revascularization or healing. Ingrowth was marginal and averaged less than 5%. Conclusions: This tantalum implant in its present design and surgical technique does not appear to uniformly provide structural support and promote healing of early osteonecrosis of the femoral head. This retrieval study suggests that successful results with this implant in certain cases of early osteonecrosis may be more attributable to the surgical technique requiring a core decompression, rather than the implant itself. |

Introduction:. First generation highly crosslinked polyethylenes (HXPLEs) have proven successful in lowering both penetration and osteolysis rates. However, 1. st. generation annealing and remelting thermal stabilization have been associated with in vivo oxidation or reduced mechanical properties. Thus, 2. nd. generation HXLPEs were developed to improve oxidative stability while still maintaining material properties. Little is known about the in vivo clinical failure modes of these 2. nd. generation HLXPEs. The purpose of this study was to assess the revision reasons, wear, oxidative stability, and mechanical behavior of retrieved sequentially annealed Vitamin E diffused HXLPE in THA and TKA. Methods:. 251 2. nd. Generation HXLPE hip and knee components were consecutively retrieved during revision surgeries and continuously analyzed in a prospective, IRB approved, multicenter study. 123 acetabular liners (Implanted 1.2y; Range 0–5.0y) and 117 tibial inserts (Implanted 1.6y; Range 0–5.8y) were highly crosslinked and annealed in 3 sequential steps (X3). Five acetabular liners (Implanted 0.6y; Range 0–2.0y) and six tibial inserts (Implanted 1.3y; Range 0.5–1.8y) were diffused with Vitamin E (E1). Patient information was collected from medical records (Table 1). Linear penetration of liners was measured using a calibrated digital micrometer (accuracy: 0.001 mm). Surface damage of tibial components was assessed using the Hood method. Thin sections were taken from the acetabular liners (along the superior/inferior axis) and the tibial components (along the medial condyle and central spine) for oxidation analysis and analyzed according to ASTM 2102. Mechanical behavior was assessed via the small punch test (ASTM 2183). Results:. The liners and tibial components fabricated from both HXLPEs were revised predominantly for loosening, instability, and infection (Figure 1). The average penetration rate for the Sequentially Annealed group was low (PR = 0.045 mm/yr). Pitting, scratching and burnishing were the predominant damage mechanisms of the tibial inserts within both material groups, with no evidence of delamination. Oxidation indices were low (Mean OI≤0.3) and similar between liners and inserts of the Sequentially Annealed components at the bearing and backside surface (Figure 2, p ≥ 0.15). Oxidation was positively correlated with implantation time at the bearing surface of the Sequentially Annealed groups (Rho > 0.29, p < 0.005). The Ultimate Load of the Sequentially Annealed acetabular liners was statistically higher than the tibial components (p < 0.001), however the mean difference was minimal (∼6N). Discussion:. This study evaluated the properties of 2. nd. generation HXLPEs used in THA and TKA. Sequentially Annealed liners had penetration rates comparable with 1. st. generation HXLPEs. While oxidation was low for both sequentially annealed and Vitamin E HXLPEs, we were able to detect regional variations in the oxidative in the sequentially annealed cohort. Longer-term retrievals are necessary to fully assess the oxidative stability of Vitamin E diffused HXLPE used in TKA and THA

Controversy has existed for decades over the role of fretting-corrosion in modular CoCr heads used with stems of CoCr vs Ti6Al4V. Since retrieval data on taper performance remains scant, we report here an18-year survivorship of a Ti6Al4V: CoCr combination (APR design; Intermedics Inc). Unique to this study were the threaded profiles present on both stem and head tapers (Fig. 1). This female patient was revised for pain, osteolysis and recurrent hip dislocation at 17 years, 10 months. A prior MPE hip replacement performed for her severely dysplastic right hip had lasted 11 years. At this 2nd revision, the 28 mm CoCr head was found dislocated posteriorly and superiorly. Metallosis was evident in the tissues. The polyethylene liner showed extensive rim damage on both anterior and posterior aspects. The neck of her APR Revision stem (Intermedics Inc) had worn through the polyethylene rim and impinged on the metal cage. The cage was found loose, the liner had disassociated, and the peri-trochanteric areas were compromised by massive osteolysis. The femoral stem and head were removed together without disassembly. The femoral stem and acetabular construct were replaced by an ARCOS revision system using 36 mm head with a Freedom cup (cemented to Max-Ti cage; Biomet Inc.). The complete femoral neck and head were bi-valved assembled in horizontal plane for direct imaging by interferometry and SEM (Fig. 1a). After sectioning the head separated from the stem. Quantitative imaging used 1 to 5 regions with 6-replicate measurements per region and differentiation into contact and non-contact zones (Fig. 1b). Visual corrosion mapping (3) was recorded digitally in 4 anatomical views (Figs 1b–f). The thread profile on contact zone inside the head (Fig. 2a) had a pitch of approximately 40 μm and a peak-to-valley depth of 4 μm overall (Fig. 2b profile section of thread: PV = 2 μm). The thread profile on stem trunnion (Fig. 3a) had a pitch of approximately 125 μm and a peak-to-valley depth of 3.5 μm overall (Fig. 2b profile section of thread: PV = 1 μm). Thus the stem trunnion thread was much coarser than the head. Overall corrosion grading was judged very mild. Overall we were satisfied that this Ti6Al4V: CoCr combination taper junction with threaded interfaces had performed very well for 18 years. Nevertheless, our visual grading was subject to opinion and thus unrewarding. The continuing project will quantify the contacting and non-contacting regions of head and stem (Fig. 1b)