Utilization of reverse total shoulder arthroplasty (RTSA) has steadily increased since its 2003 introduction in the American market. Although RTSA was originally indicated for elderly, low demand patients, it is now being increasingly used to treat rotator cuff arthropathy, humeral fractures, neoplasms and failed total and hemi shoulder arthroplasty. There is, therefore, a growing interest in bearing surface wear of RTSA polyethylene humeral liners. In the current study, we examined humeral liners retrieved as part of an IRB approved study to determine the amount of bearing surface wear. We hypothesized that wear of the bearing surface by intentional contact with the glenosphere (mode I) would be minor compared to that produced by scapular notching and impingement of the humeral liner (mode II). Twenty-three retrieved humeral liners were retrieved at revision surgery after an average of 1.5 years implantation time. The average age at implantation was 68 years (range 50–85). Shoulders were revised for loosening (7), instability (6), infection (6), pain (2), and other/unknown reasons (2). The liners were scanned using microCT at a resolution of 50 µm and then registered against unworn surfaces to estimate the bearing surface wear depth. The depth of surface penetration due to impingement of the liner with surrounding structures was measured and the location of the deepest penetration was noted. Mode I wear of the bearing surface was detectable for five of the retrieved liners. The penetration depth was 100 µm or less for four of the liners and approximately 250 microns for the fifth liner. It was noted that the liners with discernable mode I wear were those with longer implantation times (average 2.4 years). Material loss and abrasion of the rim due to mode II wear was noted with measurable penetration in 18 of the liners. Mode II wear penetrated to the bearing surface in 11 liners. It was generally noted that volumetric material loss was dominated by mode II wear (Figure 1). In this study of short to medium term retrieved RTSA humeral liners, mode I wear of the bearing surface was a minor source of material loss. Mode II wear due to scapular notching or impingement of the rim was the dominant source of volumetric wear. This is in agreement with a previous study that we have performed on a smaller cohort of seven liners. It is noteworthy that we were able to detect measurable mode I wear for liners with moderate implantation times. The quantity of bearing surface wear that will be seen in long term retrievals remains unknown at this time

Background. Increasing evidence suggests a link between the bearing surface used in total hip arthroplasty (THA) and the occurrence of infection. It is postulated that polyethylene has immunomodulatory effects and may influence bacterial function and survival, thereby impacting the development of periprosthetic joint infection (PJI). This study aimed to investigate the association between polyethylene type and revision surgery for PJI in THA using data from the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR). We hypothesized that the use of XLPE would demonstrate a statistically significant reduction in revision rates due to PJI compared to N-XLPE. Methods. Data from the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) spanning September 1, 1999, to December 31, 2021, were used to compare the infection revision rates between THA using N-XLPE and XLPE. We calculated the Cumulative Percentage Revision rate (CPR) and Hazard Ratio (HR) while controlling for factors like age, sex, body mass index (BMI), American Society of Anesthesiologists’ (ASA) grade, and head size. Results. From the total 361,083 primary THAs, 26,827 used N-XLPE and 334,256 used XLPE. Excluding data from the first 6 months post-surgery, 220 revisions occurred in the N-XLPE group and 1,055 in the XLPE group for PJI. The HR for infection revision was significantly higher in N-XLPE compared to XLPE, at 1.64 (95% CI, 1.41–1.90, p<0.001). Conclusions. This analysis provides evidence of an association between N-XLPE and revision for infection in THA. We suspect that polyethylene wear particles contribute to the susceptibility of THA to PJI, resulting in a significantly higher risk of revision for infection in N-XLPE hips compared to those with XLPE. Level of Evidence. Therapeutic Level III

Purpose. South African arthroplasty surgeons commonly make use of new bearing surface technology. This new technology only has short term, industry funded clinical trials or simulator studies available to prove its performance and motivate its use. These products are being used despite the availability of conventional components with proven long term in vivo efficacy. In the light of the recent Du Puy ASR recall, which also showed initial good clinical results, we reviewed the available data on some of the new available bearing surface technology. Methods. We performed a literature search to identify the best available clinical data regarding duration of follow up and number of patients for a selection of new bearing surfaces and compared it to well known long term clinical follow up studies and joint registry data of conventional products. Results. New bearing surface technologies have no long term clinical supportive data. Short and medium term results are available, however these are limited and mainly industry funded. Simulator data constituts the bulk of research used as motivation for the introduction of new technologies. Conclusion. The currently available data on new bearing surface technology is not adequate to provide the arthroplasty surgeon with a confident opinion on long term safety and efficacy. Surgeons should be careful when recommending new products to their patients, who are usually well informed of new technology but often without the necessary insight. NO DISCLOSURES

Alternative bearing surfaces has been introduced to reduce wear debris-induced osteolysis after total hip arthroplasty (THA) and offered favorable results. Large population-based data for total joint surgery permit timely recognition of adverse results and prediction of events in the future. The purpose of this study was to present the epidemiology and national trends of bearing surface usage in primary total hip arthroplasty (THA) in Korea using nationwide database. A total of 30,881 THAs were analyzed using the Korean Health Insurance Review and Assessment Service database for 2007 through 2011. Bearing surfaces were sub-grouped according to device code for national health insurance claims and consisted of ceramic-on-ceramic (CoC), metal-on-polyethylene (MoP), ceramic-on-polyethylene (CoP), and metal-on-metal (MoM). The prevalence of each type of bearing surface was calculated and stratified by age, gender, hospital type, primary payer, and procedure volume of each hospital. The number of primary THAs increased by 25.2% from 5,484 in 2007 to 6,866 in 2011. The average age of the entire study population was 58.1 years, and 53.5% were male [Table 1]. CoC was the most commonly used bearing surface (76.7%), followed by MoP (11.9%), CoP (7.3%), and MoM (4.1%). The distribution of bearing surfaces was identical to that in the general population regardless of age, gender, hospital type, and primary payer [Table 2]. The mean age of patients that received hard-on-hard bearing surfaces (CoC and MoM) was significantly younger than that of patients receiving hard-on-soft bearing surfaces (CoP and MoP) (56.9 years vs. 62.6 years). During the study period, 55.1% of THAs that used a hard-on-hard bearing surface were performed in males, while 53.0% of THAs that used a hard-on-soft bearing surface were performed in females. The order of prevalence of bearing surfaces was identical in low- and medium-volume hospitals (CoC was first, MoP was second, CoP was third, and MoM was fourth). The mean hospital charges did not differ according to the bearing surface used, with the exception of CoP, which was associated with a lower mean hospital charge. There were no changes in the distribution of bearing surfaces in each year between 2007 and 2011. Overall, the percentage of THAs that used CoC bearing surfaces increased substantially from 71.6% in 2007 to 81.4% in 2011, while the percentage that used CoP, MoP, and MoM decreased significantly [Fig. 1]. One of the reasons for the dominant usage of hard-on-hard bearing surfaces may be that the principal diagnosis of primary THAs and the patient age group distribution in Korea differ from those in other countries. The most common indication for primary THA is osteonecrosis of the femoral head in Korea. In contrast, the majority of primary THAs are performed for osteoarthritis in Western countries. The choice of bearing surface may be affected by many factors, including the nation's medical delivery system, payment type, disease pattern, and age distribution of patients that undergo THA. In future, the results of a large-scale nationwide study on primary THAs using CoC bearing surfaces in Korea will be reported. For any figures or tables, please contact authors directly (see Info & Metrics tab above).

Purpose Of Study. The study was started in 2004 to determine the best bearing surface in the long term, and to measure the metal ion levels generated by each of the bearing surfaces. We present the latest updated results. Material and methods. A prospective randomised study was started in 2004 to compare the wear characteristics of Ceramic on X linked Polyethylene (C.O.P.), Ceramic on Ceramic (C.O.C), Ceramic on Metal (C.O.M.) and Metal on Metal (M.O.M) bearings. The level of Cobalt and Chrome ions in red blood cells have been documented at serial intervals, using the ICP – MS method. Aside from the bearing surfaces the rest of the implant is standard, using a Pinnacle Cup, Corail Stem and 28mm heads. 256 Cases were enrolled on the study. To date 71 cases have been lost due to death (26), revision (9) and lost to follow up (36), leaving us with 185 for follow-up. An even spread of cases in each bearing surface are still available for follow up, viz. 46 C.O.P, 48 C.O.C., 44 C.O.M. and 47 M.O.M. Average follow up is currently 4.8 years, ranging up to 9 years. Results. To date no difference could be determined on the wear properties, with all bearings being acceptable. The only wear that could be measured was with C.O.P. bearings. Metal ion levels at no stage have been raised in the C.O.P. and C.O.C. bearings. Initially C.O.M. bearings had lower levels than M.O.M. bearings, but by 36 months were virtually the same with the mean below the 2ug/L level. At 60 month follow up values on almost half of the cases show markedly lower metal ions in the C.O.M. group. Outliers in both groups were associated with poorly placed cups, with the C.O.M. bearing being more forgiving that the M.O.M. group. Conclusion. To date the C.O.P. and C.O.M. bearings are performing the best of the 4 bearing combinations. NO DISCLOSURES

Introduction:. Total Hip Replacement (THR) is a proven and effective surgical procedure. One of the main limiting factors of the longevity of THR is the performance of the bearing surface. The optimum bearing surface choice, however, remains controversial. We wanted to understand what influenced the choice of bearing surfaces amongst South African orthopaedic surgeons. We also wanted to know if there was any consensus between surgeons and the orthopaedic trade. Aims, material and methods:. There is no epidemiological registry-based data available in South Africa in respect of bearing surfaces used in hip replacements. We sent out an electronic survey to all members of the South African Orthopaedic Association as well as to trade representatives. Patient parameters influencing the choice of bearing surfaces were surveyed and these included age, gender, level of activity and diagnosis. We used a regressional and tree analysis methodology to interpret the results. Results:. We received 133 responses from orthopaedic surgeons. There were no differences in decision making and bearing surface choices according to the surgeon's experience, type of practice or fellowship training. It was statistically significant that age was the first and most important factor when deciding upon a bearing surface. The patient's activity level then played a secondary role in the final choice. We show that gender and clinical diagnosis played no significant part in decision-making. Ceramic-on-ceramic combinations were used most commonly in younger patients and metal-on-polyethylene in older patients. 73% of surgeons chose metal-on-polyethylene in patients older than 70 years. There were no surgeons who selected metal-on-metal or ceramic-on-metal combinations for any patients. Metal-on-polyethylene was the first choice in 51% of patients with a low-activity level and 23% of those patients with a high level of activity. Ceramic-on-ceramic and ceramic-on-polyethylene was the first choice in patients with a high level of activity by 32% and 34% of surgeons respectively. We received 51 responses from the trade representatives surveyed. There was no difference between the surgeons and the trade representatives in respect of their decision making when advising on bearing surfaces to be used in specific patients. Conclusion:. While each bearing surface combination has advantages and disadvantages we have demonstrated the rationale behind the decision making and the current trends in choices of bearing surfaces by South African orthopaedic surgeons. We note that our surgeon's choices are in line with international trends, especially in respect of metal containing bearing surfaces. We have also shown that the orthopaedic trade representative's guidelines are in keeping with those of the profession

Introduction. Previous studies of long-term CoCr alloy femoral components for TKA have identified 3rd body abrasive wear and inflammatory cell induced corrosion (ICIC). The extent of femoral condyle surface damage in contemporary CoCr femoral components is currently unclear. The purpose of this study was to investigate the prevalence and morphology of damage (3rd body scratches and ICIC) at the bearing surface in retrieved TKA femoral components from contemporary designs. Methods. 308 CoCr femoral TKA components were collected as part of an ongoing, multi-institutional orthopedic implant retrieval program. The collection included contemporary designs from Stryker (Triathlon n=48, NRG n=10, Scorpio n=31), Depuy Synthes (PFC n=27) and Zimmer (NexGen n=140, Persona n=1) and Biomet (Vanguard n=51). Hinged knee designs and unicondylar knee designs were excluded. Components were split into groups based on implantation time: short-term (1–3y, n=134), intermediate-term (3–5y, n=73) and long-term (6–15y, n=101). Each grouping was mainly revised for instability, infection and loosening. Third-body abrasive wear of CoCr was evaluated using a semi-quantitative scoring method similar to the Hood method (Figure 1). A score of 1 had minimal damage and a score of 4 corresponded to damage covering more than 50% of the evaluated area. ICIC damage was reported as location of affected area. A white light interferometer (Zygo New View 5000) was also used to analyze the topography of severe damage of the bearing surface. For this analysis, three representative components from each cohort were selected and analyzed in three locations on the apex of the bearing surface. We analyzed the following roughness parameters: Ra, Rsk, and Rku. Results. On the CoCr bearing surface, the primary damage mechanisms were large scratches, small random scratches, and ICIC damage (Figure 2). Mild to severe damage (Damage Score ≥ 2) was observed in 96% of the short-term, 98% intermediate-term and 94% of long-term components. Severe damage (Damage Score = 4) was observed in 43% of the short-term, 50% intermediate-term and 56% of long-term components. ICIC damage observed on a portion of the bearing surface was detected in 43% of the short-term components, 30% of the intermediate-term components and 26% of the long term components. Apparent ICIC damage on the bearing and/or a non-bearing region of the component was observed in 85% of the short-term components, 75% of the intermediate-term components and 80of long-term TKA components. The Ra, Rsk, and Rku were similar between cohorts (Table 1). Discussion. Abrasive wear of the femoral components was frequently observed in retrieved contemporary femoral components for TKA, regardless of their implantation time, and can most likely be attributed to third body damage caused by bone or bone cement debris. The prevalence of severe CoCr damage scores was highest in the long-term cohort, while the appearance of ICIC damage was lowest in the long-term cohort. Surface roughness parameters were similar in all three cohorts suggesting that the mechanism for this damage is comparable throughout the first 15 years of service. Future work is necessary to quantify the in vivo release of CoCr from abrasive wear and corrosion mechanisms, and the effects of increased surface roughness on wear of the polyethylene counter face

The main objective of joint arthroplasty is to improve activities of daily living of the patient. However, normal daily activities may lead to separation of articular surfaces of an artificial joint, possibly as a result of a combined impact and sliding motion. Therefore, the properties of articular surfaces define the durability of implant materials. Modification of bearing surfaces with poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) increases the hydration of the surfaces and decreases the wear of the substrates. Hence, a PMPC layer can potentially cushion the impact and improve the resistance of cross-linked polyethylene (CLPE). This study aimed to explore the fatigue and wear resistance of PMPC-grafted hydrated CLPE under impact-to-wear conditions using a pin-on-disk tester. The surfaces of a CLPE disk (3- or 6-mm thick) were modified with PMPC by photoinduced polymerization and were sterilized using gamma rays. The wear resistance of PMPC-grafted CLPE disks against a Co-Cr-Mo alloy pin was evaluated and compared to that of untreated disks. The disks were fixed to the tester with a metal plate (Ti-6Al-4V alloy) that had a central hole. The test was performed for 2 × 10. 6. cycles of repetitive impact and unidirectional sliding with the maximum load of 150 N, sliding distance of 10 mm, and frequency of 1 Hz [Fig. 1]. Gravimetric wear was determined by weighing the disks, and soak controls were used to compensate for fluid absorption. Volumetric changes in the surfaces of the disks were evaluated using a three-dimensional non-contact optical profiler. The average gravimetric wear (mg) after 2 × 10. 6. cycles was 0.000/0.120 for CLPE (3/6 mm) and −0.073/–0.137 for PMPC-CLPE (3/6 mm). The weight gain of the PMPC-CLPE disks was due to their greater fluid absorption compared to that of the soak controls under the impact-to-wear conditions, as judged from the fact that during the load-soak in the lubricant this gain was observed for all the disks irrespectively of PMPC grafting. PMPC-grafting decreased the gravimetric wear of CLPE (p < 0.01) in the 6-mm group, whereas the thickness of the CLPE disks had no substantial effect on the wear resistance [Fig. 2]. In all cases, three-dimensional measurements detected a remarkable volumetric penetration in the impact-sliding surfaces and an extrusion of CLPE from the backside surfaces into the hole in the metal plate. Both the volumetric penetration and backside extrusion were smaller in the 6-mm group. The PMPC grafting had no discernible effect on these volumetric changes [Fig. 3]. Even after 2 × 10. 6. cycles of impact loads, mechanical fracture or delamination of the impact-sliding or backside surfaces were hardly observed in all the groups. The results of this study revealed that: (1) PMPC-grafting of CLPE surfaces decreased the gravimetric wear irrespectively of the disk thickness; and (2) thinner CLPE increased the risk of volumetric changes, including penetration in the impact-sliding surface and extrusion of the backside surface. In conclusion, PMPC grafting can potentially improve the wear resistance of the bearing surface of biomaterials even under impact-to-wear conditions, increasing the longevity of artificial joints

The search for the ideal bearing surface in Total Hip Replacements continues. The current ‘best’ materials are felt to be combinations of metal, ceramics and cross-linked polyethylene. Laboratory studies suggest that ceramic-on-metal articulations may provide distinct advantages. This study aims to identify the best bearing surface combination with the lowest adverse side effect profile. Between February 2004 and September 2007, 164 hips were replaced in 142 patients. 39% were male and 69% were female. The average age at surgery was 53 years (17-72 years). Follow-up assessment included radiographs, the Harris Hip Score and whole blood samples for metal ion levels. Complications to date included 3 hips which needed femoral revision because of surgery related factors, and 3 cases of sepsis of which 1 settled and 2 needed revision. One hip needed revision of head and liner to a larger bearing size for recurrent dislocations, and is no longer being followed up for blood metal ions. Post-operative whole blood metal ion levels were compared to pre-operative levels to determine the increase or decrease in metal ion levels. There were no changes in those patients with ceramic-on-ceramic and ceramic-on-polyethylene articulations. Moderately raised whole blood metal ion levels were noted at 3 months in the ceramic-on-metal group, while the metal-on-metal group show the greatest increase. This study agrees with laboratory bearing surface wear studies demonstrating lower wear rates in the ceramic-on-metal group compared to the metal-on-metal group. With concerns related to high blood metal ion levels in metal-on-metal articulations, ceramic-on-metal bearing surfaces may well become a bearing surface of choice in the future, but progress needs to be monitored in the longer term

The modification of bearing surfaces with poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) is known to increase the hydration of the surfaces and decrease the wear of the substrates. PMPC grafting to acetabular liner of total hip arthroplasty showed a drastic reduction of cross-linked polyethylene (CLPE) wear in a long-term hip simulator test and achieved a good short-term clinical result. To apply this technique to other joint prostheses, the wear resistance under various conditions needs to be evaluated because every joint has a different wear mode. ASTM F732 gives a method that disk shaped polymer specimen is loaded with hemispherical pin using pin-on-disk tester, which is suitable for hydrated polymer because the lubricant is supplied every loading cycle on the surface. The purpose of this study is to evaluate the performance of PMPC-grafted hydrated CLPE under multidirectional wear condition in anticipation of applying PMPC to various prostheses. The CLPE disks of 3 or 6-mm in thickness were machined from a bar stock. The PMPC was grafted onto the CLPE surfaces using a photoinduced polymerization of MPC in aqueous medium. All disks were irradiated with a total amount of 75-kGy gamma-ray. The wear resistance of the CLPE and PMPC-grafted CLPE disks against Co-Cr-Mo alloy pin was evaluated using Ortho-POD pin-on-disk tester. The disks were fixed to the tester with a Ti-6Al-4V alloy plate that has screw hole in the center. The test conditions were a static load of 213 N, sliding shape of 5 mm × 10 mm rectangular, frequency of 1 Hz and maximum cycles of 1.0 × 10. 6. [Fig. 1]. Gravimetric wear was determined by weighing the disks and soak controls were used to compensate for the fluid absorption. After the wear test, volumetric changes of sliding and backside surfaces of disks were evaluated using a noncontact optical three-dimensional profiler. The PMPC-grafted surface showed decrease in the gravimetric wear drastically [Fig. 2]. The thickness of CLPE had no substantial effect on the wear resistance. Three-dimensional profile measurements of sliding surfaces detected a substantial volumetric penetration; the corner of sliding track were deeper than the straight-line portion. Backside extrusion was observed in all disks. The thickness of CLPE affected both volumetric penetration and backside extrusion for both untreated and PMPC-grafted CLPE. The PMPC grafting had no discernible effect on volumetric changes [Fig. 3]. Results of this study revealed: (1) the PMPC-grafted surface decreases wear of CLPE, however, the thickness of disk has no effect, in contrast, (2) thinner thickness of CLPE increases the volumetric changes including penetration in sliding surface and extrusion in back surface but the PMPC-grafted surface has no effect. Gravimetric wear did not correlate with the volumetric penetration in sliding surface because the volumetric penetration might be caused by not only the wear but also the creep deformation. In conclusion, hydrated bearing surface and thickness of bearing substrate are essential for the wear and fatigue resistance properties for an increasing longevity of artificial joint. In addition, PMPC grafting is a promising technique for increasing the longevity of various joint prostheses

Friction between bearing surfaces in Total Hip Arthroplasty has been a main target of applied tribology. MPC (2-Methacryloyloxyethyl phosphorylcholine) has a similar properties to those of cell membranes, and can reduce friction with fluid lubrication in wet environment. We have used crosslink polyethylene with MPC polymer coating for primary and revision THA since 2011. We have examined 19 cases which were followed for more than two years. Sixteen cases for primary THA and three for revision THA, and 3 were male and 16 were female. Sixteen cases were osteoarthritis, one osteonecrosis of femoral head and two rheumatoid arthritis. Average age of patients at THA was 60.1 years old. In the OR, we have experienced a very wet and slippery feeling on the bearing surface of polyethylene liner. Surface touch is similar to hard surface with oil or lotions. No PE wear were measured on the X-ray display and no infections and no fractures were occurred during follow up. MPC polymer coating in THA can be useful for reduction of friction and generation of wear debris

Reducion of friction between bearing surfaces in Total Hip Arthroplasty is a main target of biological tribology. MPC (2-Methacryloyloxyethyl phosphorylcholine) has a similar properties to those of cell membranes, and can reduce friction with fluid luburication. We have used crosslink polyethylene with MPC polymer coating for primary and revision THA since 2011. Eighty one cementless THA were performed with closslink polyethlene liner with MPC polymer in our hospital. We have examined 21 cases which were followed for more than one year. Eighteen cases for primary THA and three for revision THA, and 3 were male and 18 were female. Seventeen cases were osteoarthritis, two osteonecrosis of femoral head and two rheumatoid arthritis. Average age of patients at THA was 60.4 years old. In the OR, we have experienced a very wet and slippery feeling on the bearing surface of polyethylene liner every time. Surface touch is similar to skin with lotions. No wear were measured on the X-ray display and no infections and no fractures were occurred during follow up. MPC polymer coating in THA can be useful for reduction of friction and generation of wear debris

Introduction. Dislocation is one of the most important complications after primary total hip replacement (THR). The low incidence of this finding makes it difficult to analyse the possible risk factors. The surgical technique can also influence this rate through cup position or an adequate reconstruction of the hip. We assessed the demographic data and radiological reconstruction of the hip related to the appearance of dislocation after primary THR. Material and Methods. 1414 uncemented THRs were recorded from our Local Joint Registry. The mean age of the patients was 60.1 years old (range, 14 to 95), and the mean weight was 73.3 kg (42 to 121). There were 733 men and 974 patients were classified with an activity level of 4 or 5 according to Devane. The most frequent diagnosis was primary osteoarthritis, 795 hips, followed by avascular necrosis 207 hips. An alumina-on-alumina THR was implanted in 703 hips and a metal-on-polyethylene THR in 711 hips. A femoral head size of 28 mm was used in 708 hips and 32 mm in 704. Radiological cup position was assessed using the acetabular abduction angle, the height of the center of the hip, and the horizontal distance of the cup. Cup anteversion was measured according to Widmer and the reconstruction of the center of rotation of the hip according to Ranawat. The radiographic reconstruction of the abductor mechanism was measured using two variables: the lever arm and the height of the greater trochanter. Results. There were 38 dislocations (2.6%) and 11 hips were revised for recurrent instability (0.8%). The probability of not having a dislocation at 20 years was 97.3%. 22 hips that had dislocated were within a box for a cup position of a version between 10º to 25º and an acetabular abduction angle between 35º to 55º (p<0.001). The probability of not having a dislocation at 20 years was 98.48% for the cups within the box and 93.9% for cups outside the box (p<0.001, Log Rank test). 21 hips that had dislocated were within a box for a height of the greater trochanter between −2 mm to 5 mm and a lever arm between 56 to 64 mm (p<0.001). The probability of not having a dislocation at 20 years was 98.33% for the hips within the box and 94.6% for hips outside the box (p<0.001, Log Rank test). Adjusted Cox regression analysis showed that alumina-on alumina THR tended to dislocate less than metal-on-polyethylene THRs (p=0.061, Hazard Ratio: 2.238, Confidence Interval 95% 0.964–5.195), and hips outside the box evaluated for cup position and outside the lever arm and height of the greater trochanter box) had a higher risk for dislocation (p<0.001, HR: 3.418, CI 95% 1.784–6.549, and, p<0.001, HR:2.613, CI 95% 1.357–5.032, respectively). Conclusions. A proper reconstruction of the hip is essential to decrease the risk for dislocation after primary THR. The choice of the bearing surface may affect this risk. The weakness of the abductor muscles of the hip may be one of the most important causes for dislocation

Background. Previous studies have suggested that the modular junction of metal on metal (MoM) total hip replacements (THR) is an important source of metallic debris. Methods. We carried out a prospective study using custom techniques to analyse one of the largest collections of failed contemporary MoM devices in the world. All explants from patients who had suffered adverse reactions to metal debris (ARMD) were included in this study. These explants included: 82 36mm THRs, and 147 resurfacing head THRs and 140 resurfacing arthroplasties from several manufactures. Volumetric wear analysis of the bearing surfaces and taper junctions was carried out using a coordinate measuring machine. The relationships between total metallic loss and metal ion concentrations and the macroscopic and histological tissue appearance of THR patients were compared to those in resurfacing patients. Mann Whitney test for non-parametric data was used to assess significant differences between groups. Results. Resurfacing explants retrieved from patients who had suffered ARMD were found to have significantly higher median rates of volumetric wear than the THRs (10.16 versus 2.25mm. 3. /yr (p < 0.001)). Total volumetric material loss from taper junctions ranged from 0.01 to 21.55mm. 3. When volumetric taper wear was combined with bearing surface wear in the THR patients this total rate of material loss was still significantly less than in the resurfacing patients 2.52 versus 10.16mm. 3. /yr (p < 0.001)). Despite this, macroscopic tissue destruction and extent of ALVAL infiltration was found to be significantly greater in the THR patients. Conclusion. Taper debris appears to more readily stimulate a destructive immune cascade than debris from primary bearing surfaces. This cascade can culminate in catastrophic tissue necrosis when blood metal ion concentrations appear normal. MHRA guidance should distinguish clearly between MOM THRs and resurfacings

The purpose of this study was to evaluate the Mid-term results (minimum 5 year) of the use of 36 mm metallic femoral head coupled with 1st generation HXLPE in patients with the age of less than or equal to 50 years-old. This retrospective study included 31 cases sustained hip pain needed Total Hip Replace Arthroplasty. We used cementless stem(FMT, Zimmer, Warsaw, Indiana) at 28 cases and cement stem(Versys, Zimmer, Warsaw, Indiana) at 3 cases. We used Trilogy (Zimmer, Warsaw, Indiana) in all cases as an acetabular cup and Longevity (Zimmer, Warsaw, Indiana) in all cases as a HXLPE. Mean acetabular cup size was 52.88mm. Mean HXLPE liner thickness at 45o was 6.18mm [Fig.1]. Mean Harris hip score was 91(86–96) and all cases obtained more than 15 scores in Merle d'Aubigne and postel method at recent follow ups. All femoral stem showed stable fixation status. Mean acetabular cup Inclination was 50.6o and Anteversion was 23.1o. During follow ups, there was no complication including dislocation, osteolysis, infection and plastic fracture. Bedding-in wear rate was 0.079±0.034mm/yr. And Steady- state was 0.043±0.016mm/yr. In vitro study, 1stgeneration HXLPE showed negative mechanical property changes due to high dose radiation and remelting. So, concerns remained in using HXLPE to active patients. But we checked a good results in terms of functional scores and wear rates. And, there was no major complication during minimal 5 years check ups. So, the authors thought THRA with 36mm- metallic heads on 1st-Generation Highly Cross-linked Polyethylene as a bearing surface could be a good option in less than or equal to 50 years patients

INTRODUCTION

The intact, healthy human knee joint is stable under anterior-posterior (AP) loading but allows for substantial internal-external (IE) laxity. In vivo clinical studies of the intact knee consistently demonstrate femoral rollback with flexion (Hill et al., 2000, Dennis et al., 2005). A tri-condylar, posterior stabilized (PS) total knee arthroplasty (TKA) with a rotating platform bearing (TKA-A) has been designed to address these characteristics of the intact knee. The third condyle is designed to guide the femoral component throughout the entire flexion arc (AP stability and femoral rollback with flexion), while the rotating platform bearing allows for IE rotation.

This study used a computer model to compare the AP and IE laxity of a new TKA-A to that of two clinically established TKAs (TKA-B: rotating PS TKA, TKA-C: fixed PS TKA) and to demonstrate improvements in AP stability, IE rotation, and femoral rollback.

Introduction

Metal-on-polyethylene (MoP) is the most commonly used bearing couple in total hip replacements (THRs). Retrieval studies (Cooper et al, 2012, JBJS, Lindgren et al, 2011, JBJS) report adverse reactions to metal debris (ARMD) due to debris produced from the taper-trunnion junction of the modular MoP THRs. A recent retrospective observational study (Matharu et al, 2016, BMC Musc Dis) showed that the risk of ARMD revision surgery is increasing in MoP THRs. To the authors' best knowledge, no hip simulator tests have investigated material loss from the taper-trunnion junction of contemporary MoP THRs.

Introduction

Dislocation of an uncemented total hip replacement (THR) can cause damage to the femoral hear, when it passes through the rim of metal acetabular shell. This can lead to metal transfer on the surface of the head or chipping of bulk head material. Although dislocation is one of most common complications in total hip arthroplasty (THA), little is known if causes any further damage to the articulating surface of ceramic heads in long term observations.

Metal-on-metal hip resurfacing prostheses are a relatively recent intervention for relieving the symptoms of common musculoskeletal diseases such as osteoarthritis. While some short term clinical studies have offered positive results, in a minority of cases there is a recognised issue of femoral fracture, which commonly occurs in the first few months following the operation. This problem has been explained by a surgeon's learning curve and notching of the femur but, to date, studies of explanted early fracture components have been limited.

Tribological analysis was carried out on fourteen retrieved femoral components of which twelve were revised after femoral fracture and two for avascular necrosis (AVN). Eight samples were Durom (Zimmer, Indiana, USA) devices and six were Articular Surface Replacements (ASR, DePuy, Leeds, United Kingdom). One AVN retrieval was a Durom, the other an ASR. The mean time to fracture was 3.4 months. The AVNs were retrieved after 16 months (Durom) and 38 months (ASR).

Volumetric wear rates were determined using a Mitutoyo Legex 322 co-ordinate measuring machine (scanning accuracy within 1 micron) and a bespoke computer program. The method was validated against gravimetric calculations for volumetric wear using a sample femoral head that was artificially worn in vitro. At 5mm³, 10mm³, and 15mm³ of material removal, the method was accurate to within 0.5mm³. Surface roughness data was collected using a Zygo NewView500 interferometer (resolution 1nm).

Mean wear rates of 17.74mm³/year were measured from the fracture components. Wear rates for the AVN retrievals were 0.43mm³/year and 3.45mm³/year. Mean roughness values of the fracture retrievals (PV = 0.754, RMS = 0.027) were similar to the AVNs (PV = 0.621, RMS = 0.030), though the AVNs had been in vivo for significantly longer.

Theoretical lubrication calculations were carried out which found that in both AVN retrievals and in seven of the twelve cases of femoral fracture the roughening was sufficient to change the lubrication regime from fluid film to mixed. Three of these surfaces were bordering on the boundary lubrication regime. The results show that even before the femoral fracture, wear rates and roughness values were high and the implants were performing poorly.

Background

We have previously described the relationship between wear rates of MOM components and soft tissue necrosis. In this study we investigated the link between wear rates, metal ion concentrations and osteolysis.