Aims. Micromotion of the polyethylene (PE) inlay may contribute to backside PE wear in addition to articulate wear of total knee arthroplasty (TKA). Using radiostereometric analysis (RSA) with tantalum beads in the PE inlay, we evaluated PE micromotion and its relationship to PE wear. Methods. A total of 23 patients with a mean age of 83 years (77 to 91), were available from a RSA study on cemented TKA with Maxim tibial components (Zimmer Biomet). PE inlay migration, PE wear, tibial component migration, and the anatomical knee axis were evaluated on weightbearing stereoradiographs. PE inlay wear was measured as the deepest penetration of the femoral component into the PE inlay. Results. At mean six years’ follow-up, the PE wear rate was 0.08 mm/year (95% confidence interval 0.06 to 0.09 mm/year). PE inlay external rotation was below the precision limit and did not influence PE wear. Varus knee alignment did not influence PE wear (p = 0.874), but increased tibial component total translation (p = 0.041). Conclusion. The PE inlay was well fixed and there was no relationship between PE stability and PE wear. The PE wear rate was low and similar in the medial and lateral compartments. Varus knee alignment did not influence PE wear. Cite this article: Bone Joint Res 2024;13(5):226–236

Abstract. Introduction. At our national explant retrieval unit, we identified an unusual pattern of backside-deformation on polyethylene (PE) inserts of contemporary total-knee-replacements (TKRs). The PE backside's margins were inferiorly deformed in TKRs with central-locking trays. We reported that this backside-deformation appeared to be linked to tray debonding. Moreover, recent studies have shown high-rate of tray debonding in PS NexGen TKRs. Therefore, we hypothesised that backside deformation on PS inserts may be more than on CR inserts. Methodology. We used peer-reviewed techniques to analyse changes in the bearing (wear rate) and backside surfaces (deformation) of PE inserts using coordinate measuring machines [N=61 NexGen (CR-39 and PS-22) TKRs with non-augmented-trays]. Multiple regression was used to determine which variable had the greatest influence on backside-deformation. The amount of cement cover on trays was quantified as a %of the total surface using Image-J software. Results. There was no statistically significant difference (p=0.238) in median (IQR) wear rate of the CR PEs 18 (12–28) mm. 3. /year and PS PEs 14 (8–20) mm. 3. /year. The PE backside-deformation median (IQR) of PS [297(242–333) µm] was significantly higher (p=0.011), when compared with CR [241(161–259) µm]. Multiple regression modelling showed that duration in-vivo (p=0.037), central-clearance between insert and tray (p<0.001) and constraint (p=0.003) were significantly associated with PE backside-deformation. 27(69%) of CR and 20(91%) PS exhibited ≤10% of cement cover on tray. Conclusion. This explant study showed backside-deformation on PS inserts was more than on CR inserts. Therefore, indicating a high-rate of tibial tray debonding in PS compared to CR NexGen TKRs

Abstract. Introduction. Several studies have reported significant cobalt(Co) and chromium(Cr) elevations in the blood of patients with total-knee-replacements (TKRs), and histological signs of metal sensitivity have been reported in up to 44% of patients undergoing revision of their TKRs. We carried out this investigation to determine the source and quantity of metal release in TKRs. Methodology. We identified all TKRs with polished CoCr trays (N=59) [Vanguard=29, Attune=4 and PFC=26]. These were analysed using peer-reviewed [coordinate-measuring-machine (CMM)] methodology to measure the volumetric wear of the polyethylene (PE) bearing surfaces and trays. The trays were analysed using 2D-profilometry (surface roughness-Ra) and 4D-microscopy. Histological and blood metal ion concentration analyses were performed. Results. The median(IQR) PE wear rate was 10(6to20) mm3/year. Microscopic analysis identified pitting on superior surface of 36(49%) trays. Ra [median (IQR)] of superior surface of pitted trays [0.076 (0.060–0.084) µm] showed a statistically significant increase (p<0.001) compared with unpitted trays [0.057(0.049–0.066) µm]. 4D-microscopy and CMM analysis estimated wear volumes of up to 2mm3 secondary to pitting. The median (range) Co and Cr concentrations were 2.5µg/l (0.2–69.4) and 1.7µg/l (0.5–12.5) respectively in 40 patients. Of the tissue samples examined in 30 patients,6 had at-least “mild”-ALVAL infiltrate. All corresponding “ALVAL” explants were found to be pitted and/or show evidence of loosening of the tray. Conclusion. This study provides further evidence that CoCr release in TKR appears to be an under-recognised cause of adverse clinical outcomes. Gross metal ion elevations occurred in association with micromotion/loosening of the tray

We present minimum 20 year results of a randomized, prospective double blinded trial (RCT) of cross-linked versus conventional polyethylene (PE), using a computer assisted method of PE wear measurement. After Ethics Committee approval, 122 patients were enrolled into an RCT comparing Enduron (non cross-linked PE) and highly cross-linked Marathon PE (DePuy, Leeds, UK). Other than the PE liners, identical components were used, a Duraloc 300 metal shell with one screw, a 28mm CoCr femoral head and a cemented Charnley Elite femoral stem. All patients were followed with anteroposterior (A∼P) and lateral radiographs at 3 days, 6 weeks, 3 months, 6 months, 1, 2, 3, 4, 5, 10 and 20 years. PE wear was measured with PolyMig, which has a phantom validated accuracy of ± 0.09mm. At minimum 20 year follow-up, 47 patients had died, 5 of which had been revised prior to their death. Another 32 patients were revised and alive, leaving 43 patients unrevised and alive (15 Enduron, 28 Marathon). No patients were lost to follow-up, but 2 were not able to be radiographed (dementia), leaving 41 patients (15 Enduron, 26 Marathon) available for PE wear measurement. After the bedding-in period, Enduron liners had a wear rate of 0.182 mm/year, and Marathon liners had a wear rate of 0.028 mm/year. At 20 years follow-up, 37 patients had required revision. Patients with conventional PE had three times the revision rate (28/37) of those who received XLPE (9/37). This is the longest term RCT showing substantially improved clinical and radiological results when XLPE is used as the bearing surface

Objectives. Unicompartmental knee replacement (UKR) is a conservative option for degenerative disease, with mobile (Oxford UKR) and fixed bearing (Physica ZUK) the most commonly used devices. The primary reasons for revising UKRs include disease progression (36.9%), loosening (31.7%), and pain (7.5%). Loosening typically occurs due to osteolysis caused by wear particles from the polyethylene (PE) inserts. There is limited published literature which has quantified volumetric material loss from the PE inserts of cemented fixed-bearing UKRs. This study aimed to quantify bearing wear and backside deformation of these PE components. Design and Methods. At our national retrieval centre, we measured changes volumetric bearing wear and backside deformation of 31 explanted fixed-bearing Physica ZUK UKR PE inserts using a peer-reviewed methodology based on coordinate measuring machine analysis. These explants had been revised for any indication [Females (19) and Males (12)]. The location of the wear scars was identified and mapped. We compared the volumetric wear from the bearing surface with contemporary total knee replacement (TKR) inserts. Results. The median (IQR) total volumetric wear of the UKR PEs [96(50-152) mm. 3. ] was significantly higher (p<0.001) than contemporary TKR PEs [40 (24-83) mm. 3. ]. The median (IQR) total volumetric wear of the PEs in males [148(122-200) mm. 3. ] was significantly higher(p=0.016) than in females [56(61-119) mm. 3. ]. The wear scars were situated in the anterior third in 61% of cases, with 26% located posteriorly. Examination of the PE backside surfaces exhibited damage in the area directly inferior to the bearing surface wear scar in the majority of cases. Conclusion. In conclusion, this study highlights significant PE wear of Physica ZUK UKR inserts, with higher wear rates compared to contemporary TKR inserts, particularly in males

Objectives. Several studies have reported elevated blood cobalt (Co) and chromium (Cr) concentrations in patients with total knee replacements (TKRs). Up to 44% of tissue samples taken from patients with failed TKRs exhibit histological evidence of metal sensitivity/ALVAL. In simulated conditions, metal particles contribute approximately 12% of total wear debris in TKR. We carried out this investigation to determine the source and quantity of metal release in TKRs. Design and Methods. We analysed 225 explanted fixed-bearing TKRs (Attune, Genesis II, NexGen, PFC, and Vanguard) revised for any indication. These were analysed using peer-reviewed [coordinate measuring machine (CMM)] methodology to measure the volumetric wear of the polyethylene (PE) bearing surfaces and trays. The trays were analysed using 2D profilometry (surface roughness-Ra) and light microscopy. Histological and blood metal ion concentration analyses were performed in a sub-sample of patients. Results. The median (IQR) PE wear rate was 14 (6 to 20) mm. 3. /year. Microscopic examination of the superior surface of trays exhibited pitting on 132 (59%) of trays. There was a statistically significant (p<0.05) increase in Rvk on the pitted area of trays for each design, indicating material removal from the pits compared to the unpitted area. The inferior surface of 116(51%) of trays displayed polishing, indicative of abrasive wear. The median(range) Co and Cr concentrations were 2.5µg/l (0.2–69.4) and 1.7µg/l (0.5-12.5) respectively in 40 patients. Of the tissue samples examined in 30 patients, 6 had at least “mild”-ALVAL infiltrate. All corresponding “ALVAL” explants were found to be pitted and/or show evidence of loosening of the tray. Conclusion. This study provides further evidence that CoCr release in TKR appears to be an under-appreciated cause of adverse clinical outcomes. The generation of metal particles was predominantly from the metal tray, which may explain elevated metal ions after TKRs, despite no direct metal-on-metal contact

Objectives. We identified an unusual pattern of backside deformation on polyethylene (PE) inserts of contemporary total knee replacements (TKRs). The PE backside's margins were inferiorly deformed in TKRs with NexGen central-locking trays. This backside deformation was significantly associated with tray debonding. Furthermore, recent studies have shown high rate of tray debonding in PS NexGen TKRs. Subsequently, a field safety notice was issued regarding the performance of this particular device combination and the Option tray has been withdrawn from use. Therefore, we hypothesised that the backside deformation of PS inserts may be greater than that of CR inserts. Design and Methods. At our national implant retrieval centre, we used peer-reviewed techniques to analyse changes in the bearing wear rate and backside surface deformation of NexGen PE inserts using coordinate measuring machines [N=84 (CR-43 and PS-41) TKRs with non-augmented-trays]. Multiple regression was used to determine which variable had the greatest influence on backside deformation. The amount of cement cover on trays was quantified as a %of the total surface using Image-J software. Results. The median (IQR) bearing wear rate of the PS PEs [14(8-22) mm. 3. /year] was not significantly different(p=0.154) to that of the CR PEs [18(8-27)mm. 3. /year]. The median (IQR) backside deformation of the PS inserts [294(239-361) µm] was significantly greater (p<0.001) than that of the CR inserts [212(158-258)µm]. Multiple regression modelling showed that duration in-vivo (p=0.037), central-clearance between insert and tray (p<0.001) and constraint (p=0.003) were significantly associated with PE backside-deformation. 38(93%) PS and 31(72%) of CR trays exhibited ≤10% of cement cover. Non-contacting profilometry and microscopy revealed marked pitting and abrasive changes to the superior surface of the tray. Conclusion. This explant study showed the PE backside deformation was significantly higher in PS than in CR inserts and this may be one explanation for the unsatisfactory clinical performance reported with this device combination

In total hip arthroplasty (THA), cementless cup without screw holes has the putative benefits of maximizing host bone contact and reducing osteolysis by eliminating channels to backside wear particles. However, supplemental trans-acetabular screws cannot be used. 74 hips in 60 patients receiving same model of cementless cup without screw holes (Depuy Duraloc 100 HA cup) from 6/1999 to 3/2003 were prospectively followed up. All patients were allowed to have immediate full weight bearing. Age at THA was 53 ± 13 (range 24–74) years. Osteonecrosis was the leading hip disease (45% of hips). Survivorship was assessed using revision of the cup as the end point. Radiological parameters, including lateral opening angle, vertical and horizontal migration distances of the cups were measured. Paired t-test was used to compare between the measurements in early postoperative period and at final follow up. 51 hips were assessed at minimum 20 years follow-up. The mean follow-up was 22.6 (range 21 – 25) years. All the cups were well fixed. There were two cup revisions. Conventional polyethylene (PE) was used in both hips; osteolysis occurred 17 and 18 years later. Both cups were well fixed but were revised, one due to cup mal-positioning, one due to need in upsizing the articulation. 14 other hips were revised but these cups were well fixed and not revised; 9 loosened stems (most were cemented Elite plus stems), 5 PE wear and osteolysis (all were conventional PE). At 20 years, the survivorship of cups was 96.1%. Changes in lateral opening angle, vertical and horizontal migration distances were 0.44±1.59°, 0.01±1.52mm and -0.32±1.47mm respectively, without statistical significance. This study provided evidence of excellent long-term survivorship of cementless cup without screw holes. Immediate postoperative weight-bearing also did not lead to cup migration in the long-term

Results in patients undergoing total hip arthroplasty (THA) for femoral head osteonecrosis (ON) when compared with primary osteoarthritis (OA) are controversial. Different factors like age, THA type or surgical technique may affect outcome. We hypothesized that patients with ON had an increased revision rate compared with OA. We analysed clinical outcome, estimated the survival rate for revision surgery, and their possible risk factors, in two groups of patients. In this retrospective cohort analysis of our prospective database, we assessed 2464 primary THAs implanted between 1989 and 2017. Patients with OA were included in group 1, 2090 hips; and patients with ON in group 2, 374 hips. In group 2 there were more men (p<0.001), patients younger than 60 years old (p<0.001) and with greater physical activity (p<0.001). Patients with lumbar OA (p<0.001) and a radiological acetabular shape type B according to Dorr (p<0.001) were more frequent in group 1. Clinical outcome was assessed according to the Harris Hip Score and radiological analysis included postoperative acetabular and femoral component position and hip reconstruction. Kaplan-Meier survivorship analysis was used to estimate the cumulative probability of not having revision surgery for different reasons. Univariate and multivariate Cox regression models were used to assess risk factors for revision surgery. Clinical improvement was better in the ON at all intervals. There were 90 hips revised, 68 due to loosening or wear, 52 (2.5%) in group 1, and 16 (4.3%) in group 2. Overall, the survival rate for revision surgery for any cause at 22 years was 88.0 % (95% CI, 82-94) in group 1 and 84.1% (95% CI, 69 – 99) in group 2 (p=0.019). Multivariate regression analysis showed that hips with conventional polyethylene (PE), compared with highly-cross linked PEs or ceramic-on-ceramic bearings, (p=0.01, Hazard Ratio (HR): 2.12, 95% CI 1.15-3.92), and cups outside the Lewinnek´s safe zone had a higher risk for revision surgery (p<0.001, HR: 2.57, 95% CI 1.69-3.91). Modern highly-cross linked PEs and ceramic-on-ceramic bearings use, and a proper surgical technique improved revision rate in patients undergoing THA due to ON compared with OA

Special acetabular polyethylene (PE) liners are intended to increase the stability of the artificial hip joint, yet registry studies on them are limited. The pupose of this study was to investigate differences in revision rates for mechanical complications in primary cementless total hip arthroplasty (THA) with standard and special PE acetabular liners in patients with ostheoarthritis. Data from the German Arthroplasty Registry (EPRD) between 2012 until 2020 were analysed. Patients with diagnosed ostheoarthritis of the hip without relevant prior surgeries, who received a primary cementless THA with a ceramic/PE bearing articulation were included. Cumulative incidences of revision for mechanical complications for Standard and 4 special PE liners (Lipped, Increased Offset, Angulated, Angulated|Increased Offset) were determined using the Kaplan-Meier Estimator. Confounding factors were investigated with a Cox proportional-hazards model. In total 151.104 cases were included. 7-year unadjusted revision-free survival for mechanical complications compared to Standard liners (97.7%) was lower for Angulated (97.4%), Lipped (97.2%) and Angulated|Increased Offset liners (94.7%), but higher for Increased Offset liners (98.1%). Risk of revision for mechanical complications was not significantly different between Standard, Lipped and Angulated liners. Increased Offset liners (HR=0.68; 95% CI=0.5–0.92) reduced, while Angulated|Increased Offset liners (HR= 1.81; 95% CI=1.38–2.36) increased the risk. Higher age at admission and an Elixhauser comorbidity index greater zero increased the risk, whereas a larger liner share slightly reduced the risk. Only the use of Increased Offset liners reduced the risk of revision for mechanical complications compared to Standard liners — other special liners did not

Artificial knee joints are continuously loaded by higher contact stress than artificial hip joints due to a less conformity and much smaller contact area between the femoral and tibial surfaces. The higher contact stress causes severe surface damage such as pitting or delamination of polyethylene (PE) tibial inserts. To decrease the risks of these surface damages, the oxidation degradation of cross-linked polyethylene (PE) induced by residual free radicals resulting from gamma-ray irradiation for cross-linking or sterilization should be prevented. Vitamin E (VE), as an antioxidant, blended PE (PE(VE)) has been used to solve the problems. In addition, osteolysis induced by PE wear particles, bone cement and metallic debris is recognized as one of the important problems for total knee arthroplasty (TKA). To decrease the generation of PE wear particles, we have developed the bearing surface mimicking the articular cartilage; grafting a biocompatible polymer, poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC), onto the PE surface having high wear resistance. In this study, we have evaluated the surface, mechanical under severe oxidative condition, and wear properties of PMPC-grafted cross-linked PE(VE) (PMPC-CLPE(VE)) material for artificial knee joints. Untreated and PMPC-grafted 0.1 mass% VE-blended PE (GUR1020E resin) with a gamma-ray irradiation of 100 kGy for cross-linking and 25 kGy for sterilization were prepared (CLPE(VE) and PMPC-CLPE(VE), respectively). Surface properties were evaluated by Fourier-transform infrared (FT-IR) spectroscopy and transmission electron microscope (TEM) observations. Surface wettability and frictional property were measured by static water contact angle measurement and ball-on-plate friction test. To evaluate the oxidation degradation resistance, mechanical and physical properties such tensile test, izod impact test, small punch test and cross-link density measurement before and after accelerated aging were measured. Wear properties of the tibial inserts were examined by using knee simulator in the combination of Co-Cr-Mo femoral components according to ISO14243-3. Gravimetric wear, volumetric penetration and the number of generated wear particles were measured. By the FT-IR measurements and TEM observation, P–O peaks attributed to MPC unit and uniform PMPC layer with 100–200 nm thick was observed only on PMPC-CLPE(VE) surface. Static water contact angle of CLPE(VE) was almost 100 degree, while that of PMPC-CLPE(VE) decreased significantly to almost 35 degree. There was no significant difference in the mechanical and physical properties between CLPE(VE) and PMPC-CLPE(VE). Moreover, both the CLPE(VE) and PMPC-CLPE(VE) maintained these properties even after the accelerated aging of 12 weeks [Fig. 1]. Blended VE in CLPE would act as radical scavengers to prevent oxidation degradation. In the knee simulator wear test, the PMPC-CLPE(VE) tibial inserts showed about a half gravimetric wear compared to the CLPE(VE) tibial inserts [Fig. 2]. This would be due to the significant differences observed in wettability of the surface. Water thin film formed on the hydrated PMPC graft layer, would act as significantly efficient lubricant. From these results, the PMPC-CLPE(VE) is expected to be one of the great bearing materials not only preventing surface damages due to higher contact stress and oxidation degradation but also improving wear resistance, and to provide much more lifelong artificial knee joints. For any figures or tables, please contact authors directly (see Info & Metrics tab above).

Objectives. Patient-specific (PS) implantation surgical technology has been introduced in recent years and a gradual increase in the associated number of surgical cases has been observed. PS technology uses a patient’s own geometry in designing a medical device to provide minimal bone resection with improvement in the prosthetic bone coverage. However, whether PS unicompartmental knee arthroplasty (UKA) provides a better biomechanical effect than standard off-the-shelf prostheses for UKA has not yet been determined, and still remains controversial in both biomechanical and clinical fields. Therefore, the aim of this study was to compare the biomechanical effect between PS and standard off-the-shelf prostheses for UKA. Methods. The contact stresses on the polyethylene (PE) insert, articular cartilage and lateral meniscus were evaluated in PS and standard off-the-shelf prostheses for UKA using a validated finite element model. Gait cycle loading was applied to evaluate the biomechanical effect in the PS and standard UKAs. Results. The contact stresses on the PE insert were similar for both the PS and standard UKAs. Compared with the standard UKA, the PS UKA did not show any biomechanical effect on the medial PE insert. However, the contact stresses on the articular cartilage and the meniscus in the lateral compartment following the PS UKA exhibited closer values to the healthy knee joint compared with the standard UKA. Conclusion. The PS UKA provided mechanics closer to those of the normal knee joint. The decreased contact stress on the opposite compartment may reduce the overall risk of progressive osteoarthritis. Cite this article: K-T. Kang, J. Son, D-S. Suh, S. K. Kwon, O-R. Kwon, Y-G. Koh. Patient-specific medial unicompartmental knee arthroplasty has a greater protective effect on articular cartilage in the lateral compartment: A Finite Element Analysis. Bone Joint Res 2018;7:20–27. DOI: 10.1302/2046-3758.71.BJR-2017-0115.R2

Objectives. Malrotation of the femoral component can result in post-operative complications in total knee arthroplasty (TKA), including patellar maltracking. Therefore, we used computational simulation to investigate the influence of femoral malrotation on contact stresses on the polyethylene (PE) insert and on the patellar button as well as on the forces on the collateral ligaments. Materials and Methods. Validated finite element (FE) models, for internal and external malrotations from 0° to 10° with regard to the neutral position, were developed to evaluate the effect of malrotation on the femoral component in TKA. Femoral malrotation in TKA on the knee joint was simulated in walking stance-phase gait and squat loading conditions. Results. Contact stress on the medial side of the PE insert increased with internal femoral malrotation and decreased with external femoral malrotation in both stance-phase gait and squat loading conditions. There was an opposite trend in the lateral side of the PE insert case. Contact stress on the patellar button increased with internal femoral malrotation and decreased with external femoral malrotation in both stance-phase gait and squat loading conditions. In particular, contact stress on the patellar button increased by 98% with internal malrotation of 10° in the squat loading condition. The force on the medial collateral ligament (MCL) and the lateral collateral ligament (LCL) increased with internal and external femoral malrotations, respectively. Conclusions. These findings provide support for orthopaedic surgeons to determine a more accurate femoral component alignment in order to reduce post-operative PE problems. Cite this article: K-T. Kang, Y-G. Koh, J. Son, O-R. Kwon, C. Baek, S. H. Jung, K. K. Park. Measuring the effect of femoral malrotation on knee joint biomechanics for total knee arthroplasty using computational simulation. Bone Joint Res 2016;5:552–559. DOI: 10.1302/2046-3758.511.BJR-2016-0107.R1

Background. Reduced dislocation rates using lipped polyethylene (PE) liners in modular uncemented acetabular components has been shown, yet there may be increased wear because of impingement, which may lead to aseptic loosening. We used New Zealand Joint Registry (NZJR) data to compare survival rates, revision rates for dislocation and aseptic loosening between lipped and neutral liners. Methods. 31,247 primary THAs using the four commonly used uncemented modular cups were identified (January 1, 1999 to December 31, 2018). The lipped liner group comprised 49% males vs 42% in the neutral group (p < 0.001); 96% had OA vs 95% in the neutral group (p < 0.001). There was no difference in other patient characteristics. Mean follow-up was 5.1 years (SD 3.9); longest follow-up 19.3 years. Kaplan Meier survival rates were compared (20,240 lipped and 11,007 neutral PE liners). Highly cross-linked PE was used in 99% of lipped liner cups vs 85% of neutral liner cups. Associated hazard ratios were calculated using a Cox regression analysis. Results. KM survival at 10 years for lipped PE liners was 96% for lipped (95%CI 95.4%-96.2%) and 95% for neutral liners (95%CI 94.7%-95.9%). Controlling for age, gender approach, head size, image guidance, the all-cause revision risk was greater for neutral liner (HR 1.17 [95% CI 1.06 to 1.36]; p = 0.032). There was a higher risk of revision for dislocation in those with neutral liners (HR 1.84 [95%CI 1.41–2.41]; p < 0.001) but no difference in the revision rate for aseptic acetabular loosening (HR 0.85 [95%CI 0.52–1.38]; p = 0.511). Conclusions. Using lipped PE liners is not associated with a higher rate of aseptic loosening in patients who undergo primary THA. Lipped PE liners are associated with lower rates of dislocation and lower all-cause revision rates without any increased association with revision rates for wear and aseptic loosening

Introduction. The combined incidence of anatomic (aTSA) and reverse total shoulder arthroplasties (rTSA) in the US is 90,000 per annum and rising. There has been little attention given to potential long-term complications due to periprosthetic tissue reactions to implant debris. The shoulder has been felt to be relatively immune to these complications due to lower acting loads compared to other joint arthroplasties. In this study, retrieved aTSAs and rTSAs were examined to determine the extent of implant damage and to characterize the nature of the corresponding periprosthetic tissue responses. Methods. TSA components and periprosthetic tissues were retrieved from 23 (eleven aTSA, twelve rTSA). Damage to the implants was characterized using light microscopy. Head/stem taper junction damage was graded 1–4 as minimal, mild, moderate or marked. Damage on polyethylene (PE) and metal bearing surfaces was graded 1–3 (mild, moderate, marked). H&E stained sections of periprosthetic soft tissues were evaluated for the extent and type of cellular response. A semi-quantitative system was used to score (1=rare to 4=marked) the overall number of particle-laden macrophages, foreign body giant cells, lymphocytes, plasma cells, eosinophils, and neutrophils. Implant damage and histopathological patterns were compared between the two TSA groups using the Mann-Whitney and Spearman tests. Results. The PE bearing surfaces of aTSAs were dominated by three-body wear and plastic deformation, whereas the rTSA PE components exhibited mainly polishing and scratching. Metal surface damage occurred in a few cases of both groups. Only one aTSA case exhibited marked taper corrosion. In both groups the primary nature of the inflammatory response was a moderate to marked macrophage response to wear particles (78% of cases). The particle-laden macrophages tended to occur in broad sheets and contained metal, PE, bone cement and suture debris. The extent of macrophage and foreign body giant cell responses was greater in the aTSA group (p≤0.001). Metal particles were seen in 63% of aTSAs and 83% of rTSAs. In the aTSA group, bone cement was seen in all cases and suture was observed in 9 cases, and their presence was larger compared to the rTSA group (p≤0.022). There was no difference in the number of other cell types between the groups. A mild lymphocyte response and chromium-phosphate debris was present within the tissue of the aTSA case with marked corrosion, which may be indicative of an early stage adverse local tissue reaction (ALTR) analog to total hip replacements with taper corrosion. Conclusion. Both groups exhibited a strong macrophage response to a combination of different types of implant debris—PE, metal, bone cement and suture. The prevalence of a marked macrophage response was larger in the aTSA group which may be explained by the larger overall presence of cement and suture within this group. PE particles may differ in size between groups due to different acting wear mechanisms which may also affect the extent of the macrophage response. Although corrosion within modular junctions was overall rare, the presence of one case with marked corrosion shows that taper corrosion and subsequent ALTRs are possible in TSAs. For any figures or tables, please contact authors directly

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 mm. 3. /million cycles (MC) to 126 mm. 3. /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. Methods. To date, seven patients with a self-reported well-functioning Aequalis Reversed II (Wright Medical Group, Edina, MN, USA) RTSA implant system have been imaged (mean years from surgery = 7.0, range = 6.2 to 9). Using stereo radiographs, patients were imaged at the extents of their range of motion in internal and external rotation, lateral abduction, forward flexion, and with their arm at the side. Multiple arm positions were used to account for the multiple wear vectors associated with activities of daily living and the shoulder's six degrees of motion. Using proprietary software, the position and orientation of the polyethylene and glenosphere components were identified and their transformation matrices recorded. These transformation matrices were then applied to the CAD models of each component, respectively, and the apparent intersection of the glenosphere into the PE recorded. Using previously validated in-house software, volumetric and maximum linear wear depth measurements were obtained. Linear regression was used to identify wear rates. Results. The volumetric and linear wear rates for the 36 mm PE liners (n = 5) were 39 mm. 3. /y (r. 2. = 0.86, range = 24 to 42 mm. 3. /y) and 0.09 mm/y (r. 2. = 0.96, range = 0.08 to 0.11 mm/y), respectively. Only two patients with 42 mm PE liners were evaluated. For these, volumetric and linear wear rates were 110 mm. 3. /y (r. 2. = 0.81, range = 83 to 145 mm. 3. /y) and 0.17 mm/y (r. 2. = 0.99, range = 1.12 to 1.15 mm/y), respectively. Conclusion. For the first time, PE wear was evaluated in the reverse shoulder in vivo. More patients are required for conclusive statements, but preliminary results suggest first order volumetric and linear wear rates within those predicted by simulation studies. It is interesting to note the increased wear with larger PE size, likely due to the increased contact area between congruent faces and the potential for increased sliding distance during arm motion

Background. There has been a trend in the evolution of total hip arthroplasty towards increased modularity, with this increase in modularity come some potentially harmful consequences. Modularity at the neck shaft junction has been linked to corrosion, adverse reaction to metal debris and pseudotumor formation. The aim of this retrieval study is to assess whether the surface integrity of the polyethylene (PE) liner is affected by metal wear debris in a single implant design series of THA revised for trunnionosis. Method. A retrieval analysis of thirty dual-taper modular neck hip prostheses was performed, the mean time from implantation to revision was 2.7 years (1.02–6.2). The PE liners were analysed using a scanning electron microscope with an energy dispersive spectrometer to assess for metal particles embedded on the liner surface. Serum metal ion levels and inflammatory markers were also analysed. Results. There were small numbers of metal particles present on the PE liners. The mean number of metal particles per liner was 4 and the particles varied in size from 0.5–122μm mean 16μm. All patients had elevated metal ion levels: cobalt 6.02μg/l, chromium 1.22μg/l, titanium 3.11μg/l. The cobalt:chromium ratio was 7.55:1. The inflammatory markers were also marginally raised (ESR 17 CRP 10). Conclusion. These results suggest that retention of the PE liners may be reasonable when performing isolated revision of the femoral component in cases of failure at the modular neck stem junction; especially when the inner diameter of the liner is already optimized for head size and stability

Total knee arthroplasty has been the main treatment method among advanced osteoarthritis (OA) patients. The main post-operative evaluation considers the level of pain, stability and range of motion (ROM). The knee flexion level is one of the most important categories in the total knee arthroplasty patient's satisfaction in Asian countries due to consistent habits of floor-sitting, squating, kneeling and cross legged sitting. In this study, we discovered that the posterior capsular release enabled the further flexion angles by 14 degrees compared to the average ROM without posterior release group. Our objective was to increase the ROM using the conventional total knee arthroplasty by the posterior capsular release. Posterior capsular release is being used in order to manage the flexion contraction. Although the high flexion method extends the contact area during flexion by extending the posterior condyle by 2mm, the main problem has been the early femoral loosening. We searched for the method to get the deep knee flexion with the conventional knee prosthesis. 122 OA patients with less than preoperative 130 flexion that underwent conventional TKAs using Nexgen from January, 2014 to September, 2016 were reviewed. Posterior femoral osteophytes were removed as much as possible, but 74 cases were performed posterior capsular release, while 48 cases were not performed. After checking postoperative ROM after 6 months of operation, we compared 74 knees with a posterior capsular release and 48 knees without posterior capsular release. As a result, the average ROM in the posterior capsular release group was 132 degrees, but the average ROM without posterior release group is 118 degrees. No postoperative hyperextension was found when the adequate size of polyethylene (PE) thickness was utilized. Hence, the conventional TKA with a posterior capsular release showed satisfactory clinical outcomes in the deep knee flexion of Asians

Uncemented component retention with polyethylene (PE) liner and femoral head exchange is commonly used to treat periprosthetic osteolysis. The purpose was to determine long-term implant survivorship, risk factors for aseptic failures, clinical outcomes, and complications following PE liner and head exchange. We identified 116 hips in 110 patients treated with PE liner and head exchange for osteolysis from 1993 to 2004. The mean age was 58, 64 were women, and mean follow-up was 11 years. Implant survivorship free from all-cause revisions was 91% at 5-years, 81% at 10-years, and 69% at 15-years. Reasons for re-revision included subsequent conventional PE wear and osteolysis in 7 (6%), aseptic acetabular loosening in 5 (4%), and instability in 5 hips (4%). Mean time to revision for aseptic acetabular loosening was 4 years (range 1 – 7 years). Risk factors for aseptic acetabular loosening included acetabular zones of pre-revision osteolysis, percentage of cup involvement, and size of osteolytic defects. Absolute risk of acetabular loosening was 23% for three zones of osteolysis (Relative Risk (RR) 12, p<0.01), 40% if osteolysis involved more than half the cup circumference (RR 14, p<0.01), and 21% for defects greater than 600 mm. 2. (RR 11, p<0.01). Harris hip scores improved from 77 to 87 (p<0.01). The most common complication was dislocation (16%). These data quantify risk of subsequent component loosening when well fixed, uncemented implants are retained during operations for osteolysis, and may inform operative decisions regarding shell retention versus revision

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