Background. Polyethylene wear in both cemented and uncemented total hip arthroplasty (THA) lead to generation of particles with their access to the interface which has been responsible for periprosthetic osteolysis and subsequent loosening of cup and stem. Many studies have been published studying the pattern of polyethylene wear and its relation to the type of implant (cemented/ uncemented cup or ceramic/metal head) used. No study in our knowledge has strictly focused on the effect of cemented versus uncemented stem on the polyethylene wear rates. We tried to compare the polyethylene wear rates reckoned with software (Poly Ware REV 7) of ultra high molecular weight polyethylene (UHMWPE) in hybrid and uncemented THA and its effect on complications of total hip replacements. Method. We retrospectively reviewed pre-matched 56 patients in uncemented group with 112 patients in hybrid group on the basis of polyethylene wear rate, revision rates and clinical issues, with mean follow up of 9.42 and 7.25 years (yrs.) respectively. Results. Mean polyethylene wear rate in uncemented group was 0.048 milli metres per year (mm/yr.) and it was 0.082 mm/yr. in hybrid. Wear rate in hybrid group ceramic head (0.072mm/yr.) was significant when compared to wear rate ceramic head in uncemented group (0.053mm/yr.), also we found significant difference of poly wear in the metallic group as well. There was no difference in stem loosening and cup osteolysis in low wear (<.05 mm/yr.) and high wear group (>.05mm/yr.) in both uncemented and hybrid THA. Conclusion. The revision was significantly higher in uncemented group but when adjusted with the age, it is equivocal. We found significant difference in polyethylene wear rates, but no significant difference in clinical performance and revisions among the two groups of uncemented THA and hybrid THA when compared on a mid-term 8 to 10 yrs. Follow up. Keywords. Total Hip Arthroplasty; Polywear; Uncemented THA; Hybrid THA

Introduction. It has been shown in vitro that human monocytes can phagocytose submicron polyethylene wear particles generated from total hip arthroplasties (THA) with highly cross-linked polyethylene inlays. The aim of our study was to detect the presence and possible phagocytosis of such particles in peripheral blood monocytes of patients with respective THA. Patients and methods. All patients were operated using the same implant, the cementless SL Plus stem; Bicon cup and a cross-linked polyethylene insert Rexpol (Smith and Nephew). Besides clinical and radiographic check-up, blood samples were collected at follow-up and analyzed by flow cytometry. Polyethylene can be identified by its auto fluorescence when stimulated by a laser with the wavelength of fluorescein isothiocyanate (FITC). Presence of wear particles in monocytes was identified by determination of their size and granularity. Some samples were scrutinized by confocal laser scanning microscopy to correlate the intracellular position of the particles. Blood samples of patients without total joint replacement served as controls. Results. 18 samples of patients with THA were compared to 18 controls. Flow cytometry didn't show any difference of size, granularity and auto fluorescence of the investigated cells between the two groups. Furthermore confocal laser scanning microscopy was unable to establish the intracellular position of the auto fluorescence. There were 11 female and 7 male patients with a mean age of 70,4 years at the time of surgery and an average body mass index of 32 (23 – 41). Average follow-up time was 6,5 years (6 – 8 years). 2 patients had been revised, one for a periprosthetic fracture postoperatively, the other for cup loosening at 5 years. Radiographically there were no signs of loosening. Conclusion. Flow cytometry and confocal laser scanning microscopy were unable to detect submicron polyethylene wear particles in human monocytes in vivo following THA. This could be due to a lack of sensitivity or/and specificity although the in vitro study showing phagocytosis of submicron particles in vitro applied the same methods. The analysis could be too early if the number of wear particles hasn't possibly reached a critical mass at 6.5 years. Potentially the conclusion of the in vitro study is inapplicable and human monocytes are unable to phagocytose polyethylene wear particles. In any case further research in this field seems necessary

In total knee arthroplasty, polyethylene wear has been a major cause of revision surgery. However, it is sometimes difficult to determine the time of revision surgery in elderly people due to their concomitant diseases. Therefore, the brace for measuring polyethylene wear under computed tomography was developed. Methods. The brace works by strapping a femoral component tightly to a polyethylene insert by applying compression force between the sole of the foot and the thigh. Holes of 1, 2, 5, 10 mm in diameter and 0.1, 0.2, 0.5 and 1 mm in depth were created in the posteromedial part of polyethylene inserts. The inserts were provided from Teijin-nakashima Co. ltd. (Jodo, Okayama, Japan). The Hi-tech knee artificial joint (Teijin-nakashima Co. ltd.) was applied to a cadaveric knee and CT images of the knee were taken with a combination of insets with varying diameters and depths holes, using Aquilion ONE (Toshiba Medical Systems Corporation, Ohtawara, Japan). The finding conditions were as follows, Voltage; 120V, Current; 5A, slice thickness; 0.5 mm helical. The patient, who received total knee arthroplasty over 15 years ago, wore the brace and was examined using computed tomography. Afterward, the patient received revision surgery to replace the worn insert into new one. The removed insert was measured with a three-dimensional measuring machine (Cyclon, Mitsutoyo Co. ltd., Kawasaki, Japan). Results. At a 1.0 mm depth, all holes could be detected. At a 0.5 mm depth, holes of 2, 5, 10 mm in diameter could be detected. At a 0.1∼0.2 mm depth, there was no hole detected. After revision surgery, a three-dimensional measuring machine revealed a 1.8 mm thickness of the insert on the medial side. The CT reconstruction image showed a1.84 mm thickness similar to the virtually measured figure. Conclusion. The brace and CT imaging was useful for the detection of polyethylene wear

Introduction. Periprosthetic osteolysis following total hip arthroplasty is caused mainly by polyethylene wear particles and necessitates revision surgery at some stage even in the presence of well-fixed implants. Therefore, methods to estimate the polyethylene wear become important, with manual wear measurement methods as the main outcome measurement even in the presence of computer-assisted measurement methods on account of easy availability and simplicity in their use with reasonable accuracy. The purposes of this study were to quantify the accuracy and reproducibility of the slide presentation software method on clinical radiographs and to compare it with that of the previously described Livermore's method, and to determine the usefulness of the slide presentation software methods for highly cross linked polyethylene wear measurement. Materials and Methods. 81 hips out of 61 patients who underwent primary total hip arthroplasty between October 2000 and January 2006 were retrospectively evaluated for polyethylene wear by two independent observers using the Livermore's and the slide presentation software methods. All the hips were implanted with highly cross linked polyethylene acetabular liners with cementless acetabular components. The 28 mm sized cobalt chrome alloy femoral heads were used in all cases. The mean age of the patients was 50.8 years(range, 27–73 years), and the mean follow-up period was 6.6 years (range, 2–11 years). Paired radiographs were analyzed using the Livermore's and the slide presentation software method. For the Livermore's methods, radiographs were magnified to 200%, printed, and readings taken with digital calipers with an accuracy of 0.01 mm(Figure 1). For the slide presentation software method, we used Microsoft Office PowerPoint software(Microsoft Corp., Redmond, WA, USA) as described in a previous our study(Figure 2). Results. The mean polyethylene wear rate in 81 hips measured by the Livermore's method was found to be 0.071±0.12 and 0.081±0.09 mm/year by observer 1 and 2 respectively. The mean polyethyelene wear rate measured by slide presentation software method was found to be equally 0.069±0.07 mm/year by observer 1 and 2. Interobserver and intraobserver variance were evaluated using Pearson correlation coefficient. Correlation coefficients for interobserver variance were 0.802 for the Livermore's method and 0.979 for the slide presentation software method. Correlation coefficient for intraobserver variance were 0.777 for the Livermore's method and 0.965 for the slide presentation software method in observer 1, 0.303 for the Livermore's method and 0.941 for the slide presentation software method. The mean time consumed in each radiographic measurement with the Livermore's method was 15.52 minutes (range, 10.67–22 minutes) as compared to 9.55 minutes (range, 5.42–13.5 minutes) measured with the slide presentation software method (p < 0.001). Conclusion. The slide presentation software method was more accurate in serial intra-observer measurements and more reproducible in inter-observer readings for polyethylene wear than the traditional Livermore method, and was simple to use and less time consuming. Not all orthopaedic surgeons have access to CT for measuring polyethylene wear, hence the use of this type of manual method becomes a necessity on account of its easy availability and repeatability in serial measurements

The numbers of anatomic total shoulder joint replacements (ATSR) is increasing during the past years with encouraging clinical results. However, the survivorship of ATSR is lower as compared to total knee and hip replacements. Although the reasons for revision surgery are multifactorial, wear-associated problems like loosening are well-known causes for long-term failure of ATSR. Furthermore there is lack of valid experimental wear tests for ATSR. Therefore the purpose of this study was to define experimental wear testing parameters for ATSR and to perform a wear study comparing ceramic and metallic humeral heads. Kinetic and kinematic data were adopted from in-vivo loading measurements of the shoulder joint (. orthoload.com. ) and from several clinical studies on shoulder joint kinematics. As activity an ab/adduction motion of 0 to 90° in combination with an ante/retroversion while lifting a load of 2 kg has been chosen. Also a superior-inferior translation of the humeral head has been considered. The wear assessment was performed using a force controlled AMTI joint simulator for 3×10. 6. cycles (Fig. 1) and polyethylene wear has been assed gravimetrically. The studied ATSR (Turon. TM. , DJO Surgical, USA) resulted in a polyethylene wear rate of 62.75 ± 1.60 mg/10. 6. cycles in combination with metallic heads. The ceramic heads significantly reduced the wear rate by 26.7 % to 45.99 ± 1.31 mg/10. 6. (p<0.01). The wear scars dimensions were in good agreement to clinical retrievals. This study is the first that experimentally studied the wear behavior of ATSR based on clinical and biomechanical data under load controlled conditions. In term of wear the analyzed ATSR could clearly benefit from ceramic humeral heads. However, in comparison to experimental wear studies of total knee and hip replacements the wear rate of the studied ATSR was relatively high. Therefore further research may focus on optimized wear conditions of ATSR and the hereby described method may serve as a tool to evaluate a wear optimization process

Introduction. Durable bone fixation of uncemented porous-coated acetabular cups can be observed at a long-term, however, polyethylene (PE) wear and osteolysis may affect survivorship. Accurate wear measurements correlated with clinical data may offer unique research information of clinical interest about this highly debated issue. Objetive. We assessed the clinical and radiological outcome of a single uncemented total hip replacement (THR) after twenty years analysing polyethylene wear and the appearance of osteolysis. Materials and Methods. 82 hips implanted between 1992 and 1995 were prospectively evaluated with a mean follow-up of 20.6 years (range, 18 to 23). A hemispherical porous-coated acetabular cup matched to a proximally hydroxyapatite-coated anatomic stem and a 28 mm standard PE liner, sterilised by gamma irradiation in air, was used in all hips. Radiological position and the possible appearance of loosening and osteolysis were recorded over time. Penetration of the prosthetic head into the liner was measured by the Roentgen Monographic Analysis (ROMAN) Tool at 6 weeks, 6 months, one year and yearly thereafter. Results. Six cups were revised due to wear and four due to late dislocation. All cups were radiographically well-fixed and all stems showed radiographic ingrowth. Six un-revised hips showed osteolysis on the acetabular side and two on the proximal femoral side. Creep at one year was 0.30 (±0.23) mm. Mean total femoral head penetration was 1.23 mm at 10 years, 1.52 mm at 15 years and 1.92 mm at 23 years. Overall mean wear was 0.12 (± 0.1) mm/year and 0.09 (±0.06) mm/year after the creep period. Mean wear was 0.08 (± 0.06) mm/year in hips without osteolysis and 0.14 (±0.03) mm/year in revised hips or with osteolysis (p<0.001). Conclusions. Although continued durable fixation can be observed with a porous-coated cups and a proximally hydroxyapatite-coated anatomic stem, true wear continues to increase at a constant level over time. PE wear remains as the main reason for revision surgery and osteolysis in uncemented THR after twenty years

Isolated liner and head exchange procedure has been an established treatment method for polyethylene wear and osteolysis when the acetabular component remains well-fixed. In this study, its mid-term results were evaluated retrospectively in 34 hips. Among the consecutive patients operated upon from September 1995, 2 patients (3 hips) were excluded because of inadequate follow-up and the results of remaining 34 hips of 34 patients were evaluated. They were 20 men and 14 women with a mean age of 49 years at the time of index surgery. Conventional polyethylene liner was used in 26 cases and highly cross-linked polyethylene liner was used in 8 cases. In 3 cases, liner was cemented in the metal shell because compatible liner could not be used. After a minimum follow-up of 5 years (range, 5∼20.2), re-revision surgery was necessary in 10 cases (29.4%); 8 for wear and osteolysis, 2 for acetabular loosening. In all re-revision cases, conventional polyethylene was used. There was no failure in the cases in which highly cross-linked polyethylene was used. There was no case complicated with dislocation. The results of this study suggest more promising results with the use of highly cross-linked polyethylene in isolated liner exchange

Introduction. Large-scale retrieval studies have shown backside wear in tibial inserts is dependent on the surface roughness of the tibial tray. Manufacturers acknowledge this design factor and have responded with the marketing of mirror-finished trays, which are clinically proven to have lower wear rates in comparison to historically “rough” (e.g. grit blasted) trays. While the relationship between wear and surface roughness has been explored in other polymer applications, the quantitative dependence of backside wear rate on quantitative surface finish has not yet been established for modern devices. The present study evaluates small-excursion polyethylene wear on pucks of a variety of surface roughnesses. The objective of this study is to determine where inflection points exist in the relationship between surface roughness and wear rate. Materials and Methods. An AMTI Orthopod, 6-station pin on disk tribotest was designed to mimic worst-case in vivo backside wear conditions based on published retrieval analyses. Titanium (Ti6Al4V) pucks with six different surface roughness preparations (Sa ranges from 0.06 um to 1.06 um) were characterized with white light profilometry. Never implanted polyethylene tibial inserts (never irradiated, EtO sterilized) were machined into 6 mm diameter cylindrical pins. Fretting-type motion was conducted in a 2mm square pattern at 2Hz under 100 N constant force in 25% bovine serum lubricant for 1.35 million cycles in triplicate. Mass measurements were taken every 225 thousand cycles. Results. Over the range of surface roughness studied (Sa = 0.06 – 1.06 µm), wear rate grew logistically. The wear rate for highly polished titanium (Sa = 0.06 µm) was not statistically different from less-polished titanium with Sa of 0.14 µm (p > 0.1). Titanium pucks having the highest surface roughness (Sa > 0.5µm), removed material significantly faster than those with roughness less than 0.3µm. The results of these tests suggest that Ti trays with Sa less than 0.15µm may yield equivalent clinical backside wear results, while pucks with Sa greater than 0.15µm begin to have increased wear rates that may be clinically significant. The two pucks with Sa greater than 0.5 µm yielded wear rates failing to be statistically differentiable (p = 0.059), corresponding with the flattening of the logistic curve. Discussion. These results suggest that baseplates with Sa less than 0.15 µm may ultimately yield clinically equivalent outcomes. The wear rate curve changes slope between Sa 0.14 and 0.22 µm and continues to increase across the range of surface roughnesses studied. The wear rates on rough pucks (Sa > 0.5 µm) showed high variation, reducing the ability to distinguish the two statistically (p = 0.059). Further study will better distinguish wear properties at higher surface roughnesses. Conclusion. These findings demonstrate that there may be a range of finishes between a mirror polish and grit blast that may produce clinically equivalent wear rates. This work provides justification for further study into the relationship between backside wear, baseplate tray roughness, and material choices. For any figures or tables, please contact authors directly

Frontal and lateral plain radiographs are the first choice for follow-up observations of the osteotomy boundary that faces the femoral and tibial components of a TKA. However, as plain radiographs provide no information in the image depth direction, it is difficult to determine the exact position of early-stage bone radiolucent lines. A new tomosynthesis technique, which uses both iterative reconstruction and metal extraction methods, has recently attracted attention. We report that this technique provides multi-slice images of the boundary between the metallic implant and the osteotomy surface, which is difficult to observe using conventional multi-slice imaging methods such as CT and MRI, and permits semi-three-dimensional evaluations of polyethylene wear

Introduction. Wear debris from polyethylene tibial inserts has been associated with limited longevity of total knee replacements (TKRs). While material factors were studied extensively and considerable progress has been made, there is little knowledge about surgical factors, particularly on how the wear rate is related to implant positioning. It was the purpose of this study to determine the combined effect of patient and implant positioning factors on the volumetric wear rate of TKRs. Our hypothesis was that implant alignment has a significant impact on the wear rate when controlled for other patient factors. Methods. This study included 59 tibial inserts of a cruciate retaining TKR design (Nexgen, Zimmer Inc.). The patients' age, sex, weight, height, and implant size were obtained. All implants were scanned with a coordinate measuring machine. Volumetric wear was determined using an autonomous mathematical reconstruction method (Figure 1). Radiographs were used to determine the anatomic lateral distal femoral angle (aLDFA), anatomic medial proximal tibial angle (aMPTA), femoral tilt angle (FTA) and posterior tibial slope (PTS). Also, the patella position was assessed using the Blackburne-Peel Index (BPI) and the Insall-Salvati Ratio (Figure 2). General linear modeling (SPSS) was conducted in order to determine the most significant patient and implant positioning factors on wear rate. Results. After adjustment for creep, the mean volumetric wear rate was 11.6 mm. 3. /yr (Figure 2). According to the linear regression model wear increased with younger age (p=0.0014) and male sex (p<0.001). The wear rate was independent of patient weight (p=0.17). From the multiple positioning factors only BPI and tibial slope were significant and inversely correlated with wear (p=0.009 and 0.026, respectively). The average ISR was normal before and after surgery, whereas the BPI was only in the normal range prior to surgery, and dropped postop into pseudo-baja (p<0.001, Figure 3). Discussion. The effect of male sex on wear volume can partially be explained by a larger average implant size; however, other unknown confounding factors may play a role too. The effect of younger age is likely related to higher patient activity. Based on previous gait analysis, we speculate that increasing tibial slope results in larger AP translations of the knee joint and thus more wear. Interestingly, BPI remained a highly significant factor when controlled for all other factors. The average BPI clearly dropped post-operatively, whereas the average ISR did not, indicating that not true patella baja, but a joint line elevation occurred due to the reconstruction. Joint line elevation may affect the quadriceps mechanism leading to higher contact forces and subsequent higher wear. Post-operative joint line elevation can be explained by the intention to keep bone loss at a minimum, while using thick polyethylene inserts. Further studies are needed to determine the trade-offs between bone conservation and reduction of wear rate. However, this study has revealed the importance of surgical factors regarding polyethylene wear reduction in TKR. Acknowledgements. This study was funded by NIH grant R01AR059843. For figures/tables, please contact authors directly.

Introduction. Coronal plane alignment is one of the contributing factors to polyethylene wear in total knee arthroplasty (TKA). The goal of this study was to evaluate the wear and damage patterns of retrieved tibial polyethylene inserts in relationship to the overall mechanical alignment and to the position of the tibial component. Materials and methods. Based on full-length radiographs, ninety-five polyethylene inserts retrieved from primary TKA's with a minimum time in-vivo of five years were analysed for wear and damage. Four alignment groups were compared: valgus, neutral, mild varus and moderate varus. Varus and valgus positioning of the tibial component was analysed for damage score for the neutral and varus aligned groups. Results. A progression in the angle of wear was observed with progressively mechanical varus alignment. The valgus group was thinner laterally and the neutral, mild varus, and moderate varus groups were progressively thinner medially. The lateral compartment had greater damage in the mild and moderate varus group compared to the valgus group. There was a progression of increased lateral damage with increasingly varus HKA. No difference in damage was seen between groups for tibial component positioning. Conclusion. While greater wear of the lateral compartment in valgus aligned implants and progressively greater medial compartment wear in varus aligned implants was observed, greater damage scores were observed in the lateral compartment in the mild and moderate varus aligned TKAs compared to the valgus group. This observation is unique and might by explained by lateral condylar lift-off inducing impact and shear loading in the varus group

Introduction. A common phenomenon occurring as a result of reverse total shoulder arthroplasties (RSA) is scapular notching. While bone loss of the scapula may be quantified using radiographic techniques,[1] the material loss on the humeral bearing has not been quantified. Depending on their functional biological activity, a high volume of polyethylene wear particles has been shown to be related to osteolysis, bone loss and ultimately, loosening of implants in other joints.[2] In order to understand the threshold for osteolysis in the shoulder, it is important to have a method that can accurately quantify the amount of material loss. The aim of this research was to (I) create and validate a method for quantifying material loss from a single humeral implant design which can then (II) be used to measure retrieved devices. Methods. Measurement of the surface topography of the implant was completed using coordinate measurement machine (CMM). The resulting point cloud was then imported into MATLAB and run through a custom algorithm to determine the volumetric wear of the humeral liner. Two never implanted humeral liners with an artificially damaged material loss were used for validation purposes. Each component was scanned three times, analyzed using the custom MATLAB program, and compared to gravimetric analysis (Figure 1). Following validation, an IRB-approved database was queried to identify 10 retrieved components of the same design which were then analyzed using the validated method. Results. All average measurements of the never implanted components were within +/- 5 mm. 3. of the gravimetrically determined values, providing a reasonable estimate of the volumetric wear (Figure 1). Ten retrieved components of a single design were analyzed using the same method and material loss ranged from immeasurable (within the accuracy limits) to approximately 90 mm. 3. (Figure 3). One short term duration implant (1.8 mos) exhibited approximately 78 mm. 3. of wear, resulting in a polyethylene dosage of more than 500 mm. 3. /yr. Discussion. The posterior-inferior wear pattern on the rim of these reverse shoulders appears consistent with repetitive scapular impingement. The significant wear of short duration implants indicates that wear associated with scapular notching may progress very quickly, resulting in large dose rates of debris in the joint space. However, the impingement may result in a more abrasive wear mechanism as opposed to an adhesive wear mechanism as seen in other joint wear environments. This may result in different size and shaped polyethylene particles with different biological activity. The algorithms presented in this work can be used to establish a dose-response relationship for scapular notching in RSA

Introduction. Highly cross-linked polyethylene (HXLPE) was developed to reduce the wear of articular-bearing surfaces in total hip arthroplasty (THA). This study aimed to compare the mean linear wear of HXLPE with a 22.225 mm diameter zirconia head with that of conventional polyethylene (CPE) with a 22.225 mm diameter ortron head. Materials and Methods. A prospective cohort study performed on 93 patients (113 hips) who had undergone primary cemented THAs at our hospital between January 2001 and December 2003. The subject population included 85 females and 8 males with a mean age of 58.0 years (22 to 78) at the time of surgery. The mean follow-up period was 10.2 years (9 to 12). We randomly used two types of implants: the HXLPE cup with a 22.225 mm diameter zirconia head (Kyocera Medical, Osaka, Japan) in 60 hips (HXLPE group), and the CPE cup with a 22.225 mm diameter ortron head (DePuy International, Leeds, UK) in 53 hips (CPE group). Linear wear (penatration) by computer-assisted method with PolyWare software (Draftware Inc, Indiana, USA) was measured at 10 years. Anteroposterior radiographs were evaluated for osteolysis or component loosening defined by the criteria of Hodgkinson et al. Analysis of covariance using the general linear models procedure was carried out to determine the linear wear rate difference between the groups after adjusting for variables (age at surgery, sex, body mass index, vertical distance, horizontal distance, cup inclination, and cup anteversion) as covariates. The differences were considered significant when the p value was <0.05. Results. The mean linear wear rate of HXLPE was 0.043 mm/year, compared with 0.109 mm/year for CPE (p<0.05). The incidence of osteolysis was 1 hip in the CPE group, compared with none in the HXLPE group. No evidence of revision for any reasons was noted. Statistical analysis revealed no significant differences among any variables. Conclusions. Polyethylene wear of HXLPE with a 22.225 mm zirconia head remains significantly lower than that of CPE with a 22.225 mm ortron head at 10 years after operation. HXLPE has a great advantage but careful continued follow-up will be required

Introduction. RSA is widely accepted as a precise method to asses wear and migration early in the postoperative period. In traditional RSA, one segment defines both the acetabular shell and the polyethylene liner. However, inserting beads into the liner permits employment of the shell and liner as two separate segments, thus enabling distinct analysis of the precision of three measurement methods in determining wear and acetabular shell migration. The purpose of this in vivo follow-up study was to determine if assigning the shell and liner as one combined, or two individual segments affected the precision of RSA measurements of wear and shell stability. Methods. The UmRSA program was used to analyze the double examinations of 51 hips to determine if there was a difference in precision among 3 measurement methods: the shell only, the liner only, and the shell + liner combined segment. Tantalum beads were inserted into the liner and pelvic bone surrounding the shell intraoperatively for the purpose of RSA. Polyethylene wear was measured using point motion of the center of the head with respect to 3 different segments: 1) liner only, 2) the shell only and, 3) shell + liner segment. Cup stability was measured by segment motion comparing the stable pelvic segment to 1) the liner segment, 2) the shell only segment, and 3) the shell + liner segment. The Wilcoxon paired signed-ranks test was used to determine differences in condition number and bead counts among the 3 measurement methods (p ≤0.05). Results. The 95% confidence interval, calculated from double examinations, established the precision of each method. The shell + liner and liner only methods had a precision of 0.03mm when measuring both wear and shell migration. The shell only method precision was 0.07mm when measuring wear and 0.08mm when measuring shell migration, making it the least desirable method. In both the wear and migration analyses, the shell + liner condition number was significantly lower and the bead count was significantly higher than those of the shell only and liner only methods, indicating a superior RSA analysis on all counts compared to the shell only and liner only methods. Discussion. Insertion of beads in the polyethylene improves the precision of wear and shell migration measurements. A greater dispersion and number of beads when combining the liner with the shell generated more reliable results in both analyses by engaging a larger portion of the radiograph. The liner beads also allow measurement of cup rotation of the shell + liner segment, which is not possible when using the shell segment alone, due to the 2D nature of the program's algorithm to detect the edge of the cup. As the prediction of implant survivorship in the early postoperative period relies heavily upon RSA, it is crucial to use the most precise system to monitor these implants and the shell+ liner method meets that standard

The authors entered patients into a randomised trial to compare the results of the use of cemented and cementless acetabular prostheses between 1993 and 1995. The results of mid-term wear studies at average follow up of eight years were reported in the journal in 2004. We now present long-term results to show the eventual fate of the hip replacements under study. The initial study group of 162 patients was randomly assigned to a modular titanium cup with a polyethylene liner or an all polyethylene cemented cup. All patients received a cemented stem with a 26 mm head and a standardised surgical technique. The polyethylene wear was estimated via head penetration measurement and the mid-term results showed a significantly higher wear rate in the cementless cups compared to the cemented cups (0.15mm/yr vs. 0.07mm/yr p<0.0001). The prediction was that this would lead to a higher rate of aseptic loosening in the cementless group. Patients have now been re-examined at an average of 15 years with the main emphasis on prosthesis survival. Wear studies were also performed. There were exclusions from the initial study because of death and reoperation for reasons other than aseptic loosening. The number of patients in this longer-term study had decreased as a result of death and loss to follow up. Revisions for aseptic loosening did not follow the path as suggested by the mid term wear studies. There were five cup revisions in the cemented group and one cup revision in the cementless group for aseptic loosening. No femoral stem was revised for aseptic loosening. Details of the long-term wear studies will be presented and osteolysis rates and extent documented. Despite the statistically significant difference in wear rates at the mid term, an incorrect prediction of eventual loosening rates was made. The authors believe that there are many factors other than wear rates involved in longevity of fixation. We also believe there are many weaknesses in long term prospective, randomised trials in joint replacement and question whether they are, in fact, level 1 evidence in the age of evidence based medicine

Introduction. In vitro studies showed that the anti-oxidative properties of vitamin E stabilize free radicals while retaining the mechanical strength of UHMWPE. The purpose was to evaluate vitamin E diffused polyethylene (VEPE) wear and stability of femoral components using RSA. Patient reported outcome measures (PROMs) were evaluated to determine the clinical outcome at 5 years. Methods. 48 patients (52 hips), with osteoarthritis, participated in a 5 year RSA study. Each patient received a VEPE liner, a porous titanium coated shell, and an uncemented stem with a 32mm head. Tantalum beads were inserted into the VEPE and the femur to measure head wear and stem stability using RSA. RSA and PROM follow-up was obtained postoperatively, 6 months, 1, 2, 3, and 5 years after surgery. The Wilcoxon signed-ranks test determined if changes in penetration or migration were significant (p≤0.05). Results. 47 hips were followed at 3 years, and 35 at 5 years. The median± standard error (SE) superior head penetration into the polyethylene was 0.05±0.01mm at 3 years and 0.06±0.01 mm at 5 years. There was no difference after 2 years. The median± SE distal stem migration was 0.06±0.21mm at 3 years, and 0.06±0.29mm at 5 years with no significant differences over time. All PROMs improved significantly from the preoperative to all other intervals (p<0.001 for all). Discussion. The VEPE liners show low head penetration at 5 years. The early head penetration, probably due to creep, is lower relative to that reported for non-VEPE measured by RSA. While most stems were stable, the high standard error results from one stem that migrated substantially by 6 months (9.4mm), which has since stabilized. This study documents the longest-term evaluation of in vivo wear performance of vitamin E stabilized UHMWPE. The low wear and the stability of the femoral stem shows promise for long-term survivorship

Objective

Clinical wear depends on several factors such as implant specific factors (material, design, and sterilization), surgical factors/techniques, and patient-specific factors (weights and activities). The load magnitude for wear testing in the standard protocols (i.e., 2 kN as per ASTM F1714 or 3 kN as per ISO 14243-3) represent an average patient weight and does not address the other “what-if”’ scenarios (i.e., wear vs. patient weights, activities, duration, etc.,). The results from in-vitro testing report the data in wear (mg) or wear rate (mg/Mc) and are only applicable to the parameters (i.e., loads, bearing diameter, thickness, etc.,) used for the testing and not suitable to the variations seen in clinical scenarios. Therefore, it is essential to present the wear summary that can normalize the parameters and which is relevant in both in-vitro and in-vivo conditions. The goal of the current study is an attempt to present wear as a parameter (i.e., wear factor that combines the wear test data and established- theoretical relationship) and is thus applicable in both in-vivo and in-vitro scenarios.

INTRODUCTION

The specific factors affecting wear of the ultrahigh molecular weight polyethylene (UHMWPE) tibial component of total knee replacements (TKR) are poorly understood. One recent study demonstrated that lower conforming inserts produced less wear in knee simulators. The purpose of this study is to investigate the effect of insert conformity and design on articular surface wear of postmortem retrieved UHMWPE tibial inserts.

Introduction

Total Hip Arthroplasty (THA) devices are now increasingly subjected to a progressively greater range of kinematic and loading regimes from substantially younger and more active patients. In the interest of ensuring adequate THA solutions for all patient groups, THA polyethylene acetabular liner (PE Liner) wear representative of younger, heavier, and more active patients (referred to as HA in this study) warrants further understanding.

Previous studies have investigated HA joint related morbidity [1]. Current or past rugby players are more likely to report osteoarthritis, osteoporosis, and joint replacement than a general population.

This investigation aimed to provide a preliminary understanding of HA patient specific PE liner tribological performance during Standard Walking (SW) gait in comparison to IS0:14242-1:2014 standardized testing.

Introduction

Reverse total shoulder arthroplasty (RTSA) is a semi-constrained joint replacement with an articulating cobalt-chromium glenosphere and ultra-high molecular weight polyethylene (PE). Because of its limited load bearing, surgeons and implant manufacturers have not elicited the use of highly cross-linked PE in the shoulder, and to date have not considered excessive PE wear in the reverse shoulder a primary concern. As the number of shoulder procedures is expected to grow exponentially in the next decade, however, it is important to evaluate how new designs and bearing materials interact and to have an understanding of what is normal in well-functioning joint replacements. Currently, no in vivo investigation into RTSA PE wear has been conducted, with limited retrieval and simulation studies. In vitro and in silico studies demonstrate a large range in expected wear rates, from 14.3 mm³/million cycles (MC) to 126 mm³/MC, with no obvious relationship between wear rate and polyethylene diameter. The purpose of this study is to evaluate, for the first time, both volumetric and linear wear rates in reverse shoulder patients, with a minimum six-year follow-up using stereo radiographic techniques.