Objectives. The Attune total knee arthroplasty (TKA) has been used in over 600 000 patients worldwide. Registry data show good clinical outcome; however, concerns over the cement-tibial interface have been reported. We used retrieval analysis to give further insight into this controversial topic. Methods. We examined 12 titanium (Ti) PFC Sigma implants, eight cobalt-chromium (CoCr) PFC Sigma implants, eight cobalt-chromium PFC Sigma rotating platform (RP) implants, and 11 Attune implants. We used a peer-reviewed digital imaging method to quantify the amount of cement attached to the backside of each tibial tray. We then measured: 1) the size of tibial tray thickness, tray projections, peripheral lips, and undercuts; and 2) surface roughness (Ra) on the backside and keel of the trays. Statistical analyses were performed to investigate differences between the two designs. Results. There was no evidence of cement attachment on any of the 11 Attune trays examined. There were significant differences between Ti and CoCr PFC Sigma implants and Attune designs (p < 0.05); however, there was no significant difference between CoCr PFC Sigma RP and Attune designs (p > 0.05). There were significant differences in the design features between the investigated designs (p < 0.05). Conclusion. The majority of the earliest PFC Sigma designs showed evidence of cement, while all of the retrieved Attune trays and the majority of the RP PFC trays in this study had no cement attached. This may be attributable to the design differences of these implants, in particular in relation to the cement pockets. Our results may help explain a controversial aspect related to cement attachment in a recently introduced TKA design. Cite this article: A. Cerquiglini, J. Henckel, H. Hothi, P. Allen, J. Lewis, A. Eskelinen, J. Skinner, M. T. Hirschmann, A. J. Hart. Analysis of the Attune tibial tray backside: A comparative retrieval study. Bone Joint Res 2019;8:136–145. DOI: 10.1302/2046-3758.83.BJJ-2018-0102.R2

Abstract. Objective. Up to 20% of patients can remain dissatisfied following TKR. A proportion of TKRs will need early revision with aseptic loosening the most common. The ATTUNE TKR was introduced in 2011 as successor to its predicate design The PFC Sigma (DePuy Synthes, Warsaw, In). However, following reports of early failures of the tibial component there have been ongoing concerns of increased loosening rates with the ATTUNE TKR. In 2017 a redesigned tibial baseplate (S+) was introduced, which included cement pockets and an increased surface roughness to improve cement bonding. Given the concerns of early tibial loosening with the ATTUNE knee system, this study aimed to compare revision rates and those specific to aseptic loosening of the ATTUNE implant in comparison to an established predicate as well as other implant designs used in a high-volume arthroplasty centre. Methods. The Attune TKR was introduced to our unit in December 2011. Prior to this we routinely used a predicate design with an excellent long-term track record (PFC Sigma) which remains in use. In addition, other designs were available and used as per surgeon preference. Using a prospectively maintained database, we identified 10,202 patients who underwent primary cemented TKR at our institution between 01/04/2003–31/03/2022 with a minimum of 1 year follow-up (Mean 8.4years, range 1–20years): 1) 2406 with ATTUNE TKR (of which 557 were S+) 2) 4652 with PFC TKR 3) 3154 with other cemented designs. All implants were cemented using high viscosity cement. The primary outcome measures were all-cause revision, revision for aseptic loosening, and revision for tibial loosening. Kaplan-Meier survival analysis and Cox regression models were used to compare the primary outcomes between groups. Matched cohorts were selected from the ATTUNE subsets (original and S+) and PFC groups using the nearest neighbor method for radiographic analysis. Radiographs were assessed to compare the presence of radiolucent lines in the Attune S+, standard Attune, and PFC implants. Results. At a mean of 8.4 years follow-up, 308 implants underwent revision equating to 3.58 revisions per 1000 implant-years. The lowest risk of revision was noted in the ATTUNE cohort with 2.98 per 1000-implant-years where the PFC and All Other Implant groups were 3.15 and 4.4 respectively. Aseptic loosing was the most common cause for revision across all cemented implants with 76% (65/88) of involving loosening of the tibia. Survival analysis comparing the ATTUNE cohort to the PFC and All Other Cemented Implant cohorts showed no significant differences for: all-cause revision, aseptic loosening, or tibial loosening (p=0.15,0.77,0.47). Radiolucent lines were detected in 4.6%, 5.8%, and 5.0% of the ATTUNE S+, standard ATTUNE, and PFC groups respectively. These differences were not significant. Conclusion. This study represents the largest non-registry review of the original and S+ ATTUNE TKR in comparison to its predicate design as well as other cemented implants. There appears to be no significant increased revision rate for all-cause revision or aseptic loosening. Radiographic analysis also showed no significant difference in peri-implant radiolucency. It appears that concerns of early loosening may be unfounded. Declaration of Interest. (a) fully declare any financial or other potential conflict of interest

Aims. The primary objective of this study was to compare migration of the cemented ATTUNE fixed bearing cruciate retaining tibial component with the cemented Press-Fit Condylar (PFC)-sigma fixed bearing cruciate retaining tibial component. The secondary objectives included comparing clinical and radiological outcomes and Patient Reported Outcome Measures (PROMs). Methods. A single blinded randomized, non-inferiority study was conducted including 74 patients. Radiostereometry examinations were made after weight bearing, but before hospital discharge, and at three, six, 12, and 24 months postoperatively. PROMS were collected preoperatively and at three, six, 12, and 24 months postoperatively. Radiographs for measuring radiolucencies were collected at two weeks and two years postoperatively. Results. The overall migration (mean maximum total point motion (MPTM)) at two years was comparable: mean 1.13 mm (95% confidence interval (CI), 0.97 to 1.30) for the ATTUNE and 1.16 mm (95% CI, 0.99 to 1.35) for the PFC-sigma. At two years, the mean backward tilting was -0.43° (95% CI, -0.65 to -0.21) for the ATTUNE and 0.08° (95% CI -0.16 to 0.31), for the PFC-sigma. Overall migration between the first and second postoperative year was negligible for both components. The clinical outcomes and PROMs improved compared with preoperative scores and were not different between groups. Radiolucencies at the implant-cement interface were mainly seen below the medial baseplate: 17% in the ATTUNE and 3% in the PFC-sigma at two weeks, and at two years 42% and 9% respectively (p = 0.001). Conclusion. In the first two postoperative years the initial version of the ATTUNE tibial component was not inferior with respect to overall migration, although it showed relatively more backwards tilting and radiolucent lines at the implant-cement interface than the PFC-sigma. The version of the ATTUNE tibial component examined in this study has subsequently undergone modification by the manufacturer. Level of Evidence: 1 (randomized controlled clinical trial). Cite this article: Bone Joint J 2020;102-B(9):1158–1166

Introduction. Despite improvement in implants and surgical techniques up to 20% of Total Knee Arthroplasty TKA patients continue to report dissatisfaction. The ATTUNE Knee System was designed to provide better patellar tracking and stability through the mid-range of flexion and therefore improve patient outcomes and satisfaction. Aims. The aims of this study were to assess patient outcomes in a consecutive series of ATTUNE TKA and ensure early results were comparable to other TKA systems in Australia. Methods. Between September 2014 and December 2015, 332 ATTUNE TKR's were implanted locally. All patients in our learning curve from case 1 were included. Mean follow-up was 2.6 years (range: 2.0–3.2). Revision, complications and postoperative ROM was collected. Patient reported outcome was measured using the Multi-Attribute Arthritis Prioritization Tool (MAPT) questionnaire. Revision rates were cross checked with an AOANJRR Ad Hoc report. Results. Revision rate of the ATTUNE TKR was lower than national rates, however not statistically different (1.6% vs. 2.1%) (p=0.508). Postoperative MAPT scores were significantly lower after TKR (median 63.4 vs. 0.0) (p<0.001). A total of 86.7% patients had a good outcome postoperative TKR (MAPT≤ 20). Conclusion. Our findings suggest the ATTUNE TKR has comparable revision rates to other TKRs currently available in Australia. Furthermore, patient reported outcome was high 2.8 years postoperatively, with 85% patient satisfaction

Abstract. Introduction. Higher than expected rates of tibial loosening with the ATTUNE® total knee arthroplasty (TKA) implant has been reported. Component loosening can be associated with the development of radiolucency lines (RLL) and our study aim was to systematically assess the reported rates of these. Methodology. A systematic search was undertaken using the Cochrane methodology in four online databases. Identified studies were assessed and screened against predetermined inclusion criteria. Meta-analysis was conducted using a random-effects model. Results. Nine studies (n=2,727 TKAs) from 6,590 titles met the inclusion criteria: 1 Randomised Controlled Trial (n=74), 1 prospective cohort (n=200), 4 retrospective cohort (n=1,639), and 3 case-series (n=814). All used the 2013 ATTUNE® design. In meta-analysis: 8 studies (n=1,440 ATTUNE TKAs) reported an overall prevalence of 11% (95%CI: 6.4-18.3%) for medial tibia RLL; 7 studies (n=940) a 12.3% (95%CI: 4.0-32%) rate of any tibia RLL.; 5 studies (n=736) femoral RLL in 11% (95%CI: 7.2-106.5%) and 7 studies (n=896) any RLL in 20.7% (95%CI: 13.4-30.6%). Meta-analysis of 4 studies (n=1,036) comparing the ATTUNE® with another implant (PFC Sigma®, LCS®, or PERSONA®) showed a higher risk of medial tibia RLL (OR: 2.538; 95%CI: 1.397-4.611, P=0.002) and any RLL (OR: 2.725; 95%CI: 1.302-5.703, P=0.008) in the ATTUNE® group. Conclusions. The 2013 ATTUNE® TKA system is associated with high rates of radiolucency around the tibial and femoral components. Comparative studies suggesting these rates are more than double those of other systems. Radiolucency may be a herald of component loosening, therefore, close surveillance of this implant is recommended

Introduction

In an effort to provide a TKA bearing material that balances resistance to wear, mechanical failure and oxidation, manufacturers introduced antioxidant polyethylene. In many designs, this is accomplished through pre-blending the polymer with the antioxidant before consolidation and radiation crosslinking. This study reports the wear performance (in terms of thickness change) of a hindered phenol (PBHP) UHMWPE from analysis of an early series of knee retrievals and explores these questions: 1) What is early-time performance of this new bearing material? 2) Is there a difference in performance between fixed and mobile bearings in this design? 3) How does quantitative surface analysis help understand performance at the insert-tray modular interface?

Aims. A novel enhanced cement fixation (EF) tibial implant with deeper cement pockets and a more roughened bonding surface was released to market for an existing total knee arthroplasty (TKA) system.This randomized controlled trial assessed fixation of the both the EF (ATTUNE S+) and standard (Std; ATTUNE S) using radiostereometric analysis. Methods. Overall, 50 subjects were randomized (21 EF-TKA and 23 Std-TKA in the final analysis), and had follow-up visits at six weeks, and six, 12, and 24 months to assess migration of the tibial component. Low viscosity bone cement with tobramycin was used in a standardized fashion for all subjects. Patient-reported outcome measure data was captured at preoperative and all postoperative visits. Results. The patient cohort mean age was 66 years (SD seven years), 59% were female, and the mean BMI was 32 kg/m. 2. (SD 6 kg/m. 2. ). Mean two-year subsidence of the EF-TKA was 0.056 mm (95% confidence interval (CI) 0.025 to 0.086) versus 0.006 mm (95% CI -0.029 to 0.040) for the Std-TKA, and the two-year maximum total point motion (MTPM) was 0.285 mm (95% upper confidence limit (UCL) ≤ 0.363) versus 0.346 mm (95% UCL ≤ 0.432), respectively, for a mean difference of -0.061 mm (95% CI -0.196 to 0.074). Inducible displacement also did not differ between groups. The MTPMs between 12 and 24 months for each group was below the published threshold of 0.2 mm for predicting early aseptic loosening (p < 0.001 and p = 0.001, respectively). Conclusion. Both the enhanced fixation and the standard tibial implant design showed fixation with a predicted low risk of long-term aseptic loosening. Cite this article: Bone Jt Open 2024;5(1):20–27

Introduction. Bone mineral density (BMD) is correlated with component migration and aseptic loosening after total knee arthroplasty (TKA). Older implant designs have demonstrated BMD loss up to 23% in the first 6 months after TKA, and continued to BMD decline at an average of 5% per year for as long as 2 years after TKA. The impact of component design and fixation method on BMD loss after TKA in modern implant designs has not been fully elucidated. The purpose of this study is to determine the effect of tibial tray thickness and fixation method (cemented versus cementless) on BMD loss patterns of the proximal tibia in two different modern TKA implant systems. Methods. A prospective, nonrandomized, single center study of patients undergoing primary TKA by one of two surgeons was performed with four study cohorts: cemented DePuy Attune, cementless DePuy Attune, cemented Stryker Triathlon, cementless Stryker Triathlon. Target sample size was 80, with 20 per cohort based on adhoc power analysis. Exclusion criteria included: age over 75, BMI >40, inflammatory arthritis, previous knee surgery involving the femur, tibia or tibial bone, and diagnosis of osteopenia/osteoporosis. Implant fixation type was based on surgeon intraoperative assessment of patient bone quality. Demographic data was collected preoperatively. Dual Energy X-ray Absorptiometry (DEXA) Bone Density Monitoring was performed at 6 weeks and one year postoperatively. Bone mineral density was calculated from the DEXA scans for 4 zones for the tibia relative to the keel or central peg: anterior, posterior, medial and lateral. Results were reported as BMD at 1 year postoperatively as a percentage of BMD at 6 weeks postoperatively. Results. 81 knees with complete DEXA studies at 6 weeks and 1 year postoperatively were available for analysis. The mean (SD) age at the time of surgery was 65.4 years (6.1), with 39 men and 42 women and a mean (SD) BMI of 31.2 kg/m. 2. (4.7). The patients who received cementless implants were significantly younger with a mean (SD) age of 62.1 (6.0) than those who received cemented implants with a mean age of 69.1 (3.7) (p < 0.05). There was no difference in age between implant type (p > 0.05). There was no difference in BMI or gender distribution between implant types or fixation type (p > 0.05). There was no significant difference in mean BMD loss between 6 weeks and 1 year postoperatively between the cemented and cementless Triathlon in any zone, between the cemented Triathlon and Attune in any zone, the cementless Triathlon and Attune in any zone, and the cemented and cementless attune in the lateral, anterior and posterior proximal tibia (p > 0.05). There was significantly more BMD loss seen in the medial tibia in the cemented (BMD at 1 year 88% of BMD at 6 weeks) than cementless (BMD at 1 year 103% of BMD at 6 weeks) Attune (p = 0.043). Conclusion. BMD loss at 1 year postoperatively versus 6 weeks postoperatively after TKA with two modern implant designs is not significantly affected by tibial tray thickness. BMD loss was unaffected by fixation type for the Stryker Triathlon, but was significant less for the cementless DePuy Attune than the cemented version

Aims. One of the main causes of tibial revision surgery for total knee arthroplasty is aseptic loosening. Therefore, stable fixation between the tibial component and the cement, and between the tibial component and the bone, is essential. A factor that could influence the implant stability is the implant design, with its different variations. In an existing implant system, the tibial component was modified by adding cement pockets. The aim of this experimental in vitro study was to investigate whether additional cement pockets on the underside of the tibial component could improve implant stability. The relative motion between implant and bone, the maximum pull-out force, the tibial cement mantle, and a possible path from the bone marrow to the metal-cement interface were determined. Methods. A tibial component with (group S: Attune S+) and without (group A: Attune) additional cement pockets was implanted in 15 fresh-frozen human leg pairs. The relative motion was determined under dynamic loading (extension-flexion 20° to 50°, load-level 1,200 to 2,100 N) with subsequent determination of the maximum pull-out force. In addition, the cement mantle was analyzed radiologically for possible defects, the tibia base cement adhesion, and preoperative bone mineral density (BMD). Results. The BMD showed no statistically significant difference between both groups. Group A showed for all load levels significantly higher maximum relative motion compared to group S for 20° and 50° flexion. Group S improved the maximum failure load significantly compared to group A without additional cement pockets. Group S showed a significantly increased cement adhesion compared to group A. The cement penetration and cement mantle defect analysis showed no significant differences between both groups. Conclusion. From a biomechanical point of view, the additional cement pockets of the component have improved the fixation performance of the implant. Cite this article: Bone Joint Res 2022;11(4):229–238

Introduction. With the introduction of new technology in orthopaedics, surgeons must balance anticipated benefits in patient outcomes with challenges or complications associated with surgical learning curve for the technology. The purpose of this study was to determine whether the surgeon learning curve with a new multi-radius primary TKA system (primary TKA implant and instruments) designed for surgical team ease would impact clinical outcomes, surgical time and complications. Materials & Methods. From November 2012 to July 2015, 2369 primary TKAs were prospectively enrolled in two multicenter studies across 50 sites in 14 countries with a new knee system (ATTUNE®) evenly balanced across four configurations: cruciate retaining or posterior stabilised with either fixed bearing or rotating platform (CRFB, CRRP, PSFB, PSRP). 2261 knees had a <1 year visit and 1628 had a greater than 1 year visit. These knees were compared to a reference dataset of 845 primary TKAs from three manufacturers in the same four configurations with currently available products (CURRENT-TKA). Demographics for ATTUNE and CURRENT-TKA were similar and typical for primary TKA. Operative times, clinical outcomes and a series of five patient reported outcomes were compared for ATTUNE vs. CURRENT-TKA. The first 10 ATTUNE subjects for each surgeon were defined as learning curve cases (N=520) and were compared to all later subjects (N=1849) and also with the CURRENT-TKA cases (N=845). Patient reported outcome measures and clinical outcome analyses were adjusted for covariates including patient demographics, pre-op assessment and days post-op. Results. Mean (SD) surgical time for ATTUNE learning curve cases was 79.3 (24.7) minutes, which reduced thereafter to 73.6 (24.3) (p<0.001). Beyond 10 cases, there was a continued reduction in ATTUNE surgical time (R-Squared = 0.031). After 10 cases, surgical time was on par with the mean (SD) 72.0 (21.7) for CURRENT-TKA (p=0.097). PROM outcomes of the first 10 learning curve cases for ATTUNE were not statistically different from later cases at less than 1 year or later when adjusted for relevant covariates including configuration, patient demographics, pre-op functional status, and time post-op (p-values > 0.01). PROM outcomes for ATTUNE vs. CURRENT-TKA under the same covariate adjustments showed a trend favoring KOOS ADL, Symptoms, and Sport and Recreation subscores at minimum 1 year (p-values < 0.05). The incidence of intraoperative operative site (knee) complications was 1.3% (7/520) for the ATTUNE learning curve cases which was similar to both the 0.6% (5/845) rate for historical CURRENT-TKA (p=0.230) and the 0.8% (14/1849) intraoperative complication rate for the ATTUNE later cases (p=0.195). Discussion. The introduction of new implants into the market place needs to have adequate data to support that they are safe and effective. Except for a minor increase in surgical time during the first 10 patients, this study found that surgeon learning curve with the new ATTUNE primary TKA system does not adversely affect patient short term outcomes and complication rates

To achieve a long-lasting fixation of uncemented femoral knee implants, an adequate primary stability is required. Several factors, including the applied load, bone quality, surgical preparation, and implant characteristics affect the primary fixation. Recently, novel Attune® cementless femoral component has been proposed by DePuy Synthes (Warsaw, IN, USA). We aimed to compare the primary stability of this novel high-flex design against the conventional LCS® under different loading conditions (gait, deep knee bend (DKB), and high-flex loading), while accounting for the effect of bone quality and cut accuracy. Six pairs of femora were prepared following the normal surgical procedure. Calibrated CT-scans and 3D-optical scans of the bones were obtained to measure bone mineral density (BMD) and bone cut accuracy, respectively. After implantation of the appropriate size implants (Left legs: Attune; right: LCS), a black-and-white speckle pattern was applied to each specimen (Fig.1B). The micromotion measurement was repeated three times in nine regions of interest (ROIs): the medial and lateral condyles from the posterior view; anterior, distal, and posterior regions from the medial and lateral views; the proximal tip of the anterior flange. The reconstructions were subjected to a gait load and a portion (around 50%) of the peak force of a DKB to prevent fracture of the proximal femur (Fig. 1A and Table. 1). The loads were derived from the Orthoload database using implant-specific inverse dynamics [1]. In addition, a sequence of DIC-images synchronized with the applied load was captured to find the relationship between micromotion and load. Afterwards, implants were pushed-off simulating 150° of flexion, while force-displacement graph was recorded. BMD and bone cut accuracy were not significantly different between the groups. Under both loading conditions, Attune had a significantly lower micromotion (Table. 1). Cut accuracy was not a significant factor, and BMD was only significant for the comparison under the gait loading (not under DKB conditions). High-flex push-off force was not significantly different. However, Attune required a significantly higher load to reach a micromotion of 50 or 150 µm during the push-off test. Different relations between micromotion and applied load, depending on the loading configuration and implant design, were found (Fig. 2). Our study has shown a clearly lower range of micromotion for the novel implant. Potential factors to explain the higher micromotion of LCS are parallel anterior and posterior bone cuts in the LCS versus the tapered bone cuts of the Attune. In addition, LCS has a less surface area in contact with bone due to the presence of a rim at the borders of the implant, which may have resulted in lower pre-stresses at the bone-implant interface. Taking to account, the promising clinical outcome of LCS and also the lower range of micromotion of Attune, we suggest that the Attune has a potential to be at least as successful as the LCS system from a bone fixation point of view. However, further clinical evaluation of the Attune is necessary to assess its performance on the longer term

Introduction. Tibiofemoral constraint in patients with total knee replacements (TKR) is dependent on both implant geometry and the surrounding soft tissue structures. Choosing more highly constrained geometries can reduce the contribution of soft tissue necessary to maintain joint stability [1]. Often when knee revision surgeries are required, the soft tissue and bone are compromised leading to the use of more constrained implants to ensure knee stability [2]. The current study quantifies the differences in varus-valgus (VV) and internal-external (IE) constraint between two types of total knee revision systems: SIGMA® TC3© and ATTUNE® REVISION. Methods. Nine cadaveric knees (7 male, age 64.0 ± 9.8 years, BMI 26.28 ± 4.92) were implanted with both fixed-bearing SIGMA TC3 and ATTUNE REVISION knee systems. Five knees received the TC3 implant first, while the remaining 4 received the ATTUNE implant first. The knees were mounted in an inverted position, and a six degree-of-freedom force-torque sensor (JR3, Woodland, CA) was rigidly secured to the distal tibia (Fig. 1). A series of manual manipulations applying IE and VV torques was performed through the flexion range [3]. Each specimen was then revised to the alternate revision system, and the manual manipulations were repeated. Joint loads were calculated, and tibiofemoral kinematics were described according to the Grood-Suntay definition [4]. VV and IE kinematics were calculated as a function of flexion angle, VV torque, and IE torque as has been described previously [3]. The knees were analysed at ±6 Nm VV and ±4 Nm IE, and the kinematics were normalized to the zero load path. A paired t-test (p < .05) was employed to identify significant differences between the kinematics of the two knee systems at 10º flexion increments. Results. Less VV motion was observed in the ATTUNE REVISION system compared to the TC3 system reaching statistical significance in mid-flexion. (Fig. 2). No significant differences were observed in IE rotation between the two designs, except in full extension where the SIGMA TC3 provided increased constraint (Fig. 3). Discussion. The ATTUNE REVISION System provided increased VV constraint compared to the TC3 design. The ATTUNE tibial post was more conforming to the femoral box throughout flexion, which contributed to the increased constraint. However, this increase was not concurrent with a reduction in IE rotational freedom as has been common with more constrained revision systems [5]. ATTUNE REVISION provides additional VV stability while retaining knee IE freedom and, therefore, may enable more natural knee kinematics for patients with MCL deficiency in need of a revision TKR. Future work will focus on how the increased levels of VV constraint affect weight-bearing knee kinematics in the presence of ligament deficiency. Acknowledgements. This work was supported by DePuy Synthes Joint Reconstruction, Warsaw, Indiana, a Johnson and Johnson Company. For figures and references – please contact authors directly

Introduction. Aseptic loosening of total knee replacements is a leading cause for revision. It is known that micromotion has an influence on the loosening of cemented implants though it is not yet well understood what the effect of repeated physiological loading has on the micromotion between implants and cement mantle. This study aims to investigate effect of physiological loading on the stability of tibial implants previously subjected to simulated intra-operative lipid/marrow infiltration. Methods. Three commercially available fixed bearing tibial implant designs were investigated in this study: ATTUNE. ®. , PFC SIGMA. ®. CoCr, ATTUNE. ®. S+. The implant designs were first prepared using a LMI implantation process. Following the method described by Maag et al tibial implants were cemented in a bone analog with 2 mL of bone marrow in the distal cavity and an additional reservoir of lipid adjacent to the posterior edge of the implant. The samples were subjected to intra- operative range of motion (ROM)/stability evaluation using an AMTI VIVO simulator, then a hyperextension activity until 15 minutes of cement cure time, and finally 3 additional ROM/stability evaluations were performed. Implant specific physiological loading was determined using telemetric tibial implant data from Orthoload and applying it to a validated FE lower limb model developed by the University of Denver. Two high demand activities were selected for the loading section of this study: step down (SD) and deep knee bend (DKB). Using the above model, 6 degree of freedom kinetics and kinematics for each activity was determined for each posterior stabilized implant design. Prior to loading, the 3-D motion between tibial implant and bone analog (micromotion) was measured using an ARAMIS Digital Image Correlation (DIC) system. Measurement was taken during the simulated DKB at 0.25Hz using an AMTI VIVO simulator while the DIC system captured images at a frame rate of 10Hz. The GOM software calculated the distance between reference point markers applied to the posterior implant and foam bone. A Matlab program calculated maximum micromotion within each DKB cycle and averaged that value across five cycles. The implant specific loading parameters were then applied to the three tibial implant designs. Using an AMTI VIVO simulator each sample was subjected to 50,000 DKB and 120,000 SD cycles at 0.8Hz in series; equating to approximately 2 years of physiological activity. Following loading, micromotion was measured using the same method as above. Results. Initial micomotion measurements during DKB activity for ATTUNE. ®. , PFC SIGMA. ®. CoCr, ATTUNE. ®. S+ were 155µm, 246µm, and 104µm, respectively, and following physiological loading were 159µm, 264µm, and 112µm, respectively. While there was statistical significance between the micromotion of implant designs (p<0.05), there was no significance between before and after loading. Conclusion. This study shows there is no significant change in micromotion after approximately 2 years of physiological loading. However, there is a significant difference in micromotion between implant designs

Introduction. Aseptic loosening is one of the highest causes for revision in total knee arthroplasty (TKA). With growing interest in anatomically aligned (AA) TKA, it is important to understand if this surgical technique affects cemented tibial fixation any differently than mechanical alignment (MA). Previous studies have shown that lipid/marrow infiltration (LMI) during implantation may significantly reduce fixation of tibial implants to bone analogs [1]. This study aims to investigate the effect of surgical alignment on fixation failure load after physiological loading. Methods. Alignment specific physiological loading was determined using telemetric tibial implant data from Orthoload [2] and applying it to a validated finite element lower limb model developed by the University of Denver [3]. Two high demand activities were selected for the loading section of this study: step down (SD) and deep knee bend (DKB). Using the lower limb model, hip and ankle external boundary conditions were applied to the ATTUNE. ®. knee system for both MA and AA techniques. The 6 degree of freedom kinetics and kinematics for each activity were then extracted from the model for each alignment type. Mechanical alignment (MA) was considered to be neutral alignment (0° Hip Knee Ankle Angle (HKA), 0° Joint Line (JL)) and AA was chosen to be 3° varus HKA, 5° JL. It is important not to exceed the limits of safety when using AA as such it is noted that DePuy Synthes recommends staying within 3º varus HKA and 3º JL. The use of 5º JL was used in this study to account for surgical variation [Depuy-Synthes surgical technique DSUS/JRC/0617/2179]. Following a similar method described by Maag et al [1] ATTUNE tibial implants were cemented into a bone analog with 2 mL of bone marrow in the distal cavity and an additional reservoir of lipid adjacent to the posterior edge of the implant. Tibial implant constructs were then subjected to intra-operative ROM/stability evaluation, followed by a hyperextension activity until 15 minutes of cement curing time, and finally 3 additional ROM/stability evaluations were performed using an AMTI VIVO simulator. The alignment specific loading parameters were then applied to the tibial implants using an AMTI VIVO simulator. Each sample was subjected to 50,000 DKB cycles and 120,000 SD cycles at 0.8 Hz in series; approximating 2 years of physiological activity. After physiological loading the samples were tested for fixation failure load by axial pull off. Results. Following alignment specific physiological loading the average fixation pull-off load for MA was 3289 ± 400 N and for AA was 3378 ± 133 N (Figure 1). There was no statistically significant difference fixation failure load by axial pull-off between the two alignment types (p=0.740). Conclusion. This study indicated that anatomic alignment, as defined with the alignment limits of this study, does not adversely affect the fixation failure load of ATTUNE tibial implants. For any figures or tables, please contact the authors directly

Introduction. Patella implant research is often overlooked despite its importance as the third compartment in a total knee replacement. Wear and fracture of resurfaced patellae can lead to implant failure and revision surgeries. New simulation techniques have been developed to analyze the performance of patella designs as they interact with the trochlear groove in total knee components, and clinical validation is sought to ensure that these simulations are appropriate. The objective of this work was to subject several patellar designs to patient-derived deep knee bend (DKB) inputs on a 6 degree of freedom (DOF) simulator and compare the resultant wear scars to clinical retrievals. Materials and Methods. Previously reported DKB profiles were developed based on in vivo patellofemoral data and include a wide range of patient variability. The profiles chosen for this body of work were based on the stress in the patellar lateral facet; maximizing this stress whilst maintaining the ability to run the profile stably on the simulator. Load/kinematic profiles were run on three patellar designs (n=3 per group) for 220,000 cycles at 0.8Hz on an AMTI VIVO joint simulator. A comparison cohort of clinically retrieved devices of the same design was identified in an IRB-approved database. Exclusion criteria included gross delamination, cracking secondary to oxidation, and surgeon-reported evidence of malalignment leading to mal-tracking. 29 Patellae were included for analysis: PFC. ®. All Poly (n=14), ATTUNE. ®. Anatomic (n=6), and ATTUNE. ®. Medialized Dome (n=9). Mean in vivo duration was 70.1 months. Patellae were analyzed under optical microscope in large-depth-of-field mode to map the surface damage profile. Burnishing ‘heat-maps’ were generated for retrievals and simulated patellae by normalizing the patellar size and overlaying silhouettes from each component of the same type using a custom-developed MatLAB code. Results. Burnishing heat-map comparisons between retrievals and simulator specimens for each of the three designs were compared. Retrievals show more variation than simulator devices, however the general loci and relative area of burnished regions is closely aligned for each of the three designs. The retrieved and simulated burnishing scar heat-maps on all-poly PFC. ®. patellae are centered medio-laterally with a wider profile on the lateral aspect. The burnishing marks are continuous. A similar observation may be made of the ATTUNE. ®. medialized dome, retrievals and simulator specimens, though the contact areas appear to be more concentrated away from the apex. The anatomic patellae show two primary regions of contact, and minimal burnishing at the apex. The simulator specimens likewise show two principal regions of contact. Discussion. Wear scar analysis shows that joint simulation on AMTI VIVO yields clinically relevant wear patterns across a variety of device types. Clinically relevant damage provides insight that load and motion inputs to the simulator deliver results that may be used to interpret in vivo performance or analyze future designs and/or materials. This qualitative surface contact analysis will help to inform future quantitative mass loss and fatigue failure studies. For any figures or tables, please contact authors directly

Total Knee Arthroplasty (TKA) is an effective surgery performed for knee osteoarthritis. Despite this success up to 20% of patients are less than fully satisfied. Rotating platform (RP) bearings have demonstrated significant reduction in rates of wear in laboratory studies but thus far have failed to demonstrate a clinical difference compared to fixed bearing (FB) arthroplasty in patients. This may be due to studies limited by small sample size and single centre design. Additionally, no studies have utilised modern patient-reported outcome measures (PROMs) such as PKIP to investigate differences between these bearings. A non-randomised, prospective, multi-centre study was conducted across centres in Australia, United Kingdom and the United States from November 2012 to May 2015. Knee prosthesis included were the RP and FB models of the PFC Sigma Knee (Depuy, Synthes) and the ATTUNE Knee (Depuy, Synthes). Data was collected on pre-arthroplasty interventions, demographics and PROMs. PROMs included were the KOOS, OKS, EQ53DL and PKIP. Participants were followed-up for 2 years. A total of 1,718 patients were recruited across 27 centres. 959 participants underwent a FB TKA, 759 participants underwent a RP TKA. No significant difference was found between RP and FB in change from baseline at 2 years across any parameter in all PROMs investigated at 2 years. Body Mass Index pre-operatively was the biggest indicator of change from baseline at 2 years. Our data demonstrates similar improvements in the short-term in both RP and TKA across all PROMs. Patients reported similar scores in satisfaction, confidence, mobility and stability in the PKIP PROM for both RP and FB groups. We have not found any evidence to suggest that RP TKA is disadvantageous at 2 years, and this is reassuring for any surgeon looking to utilise this bearing type in practice. Our data does not demonstrate a clinical advantage in RP TKA over FB TKA at 2 years in any PROM

Abstract. Objectives. Obesity is prevalent with nearly one third of the world's population being classified as obese. Total knee arthroplasty (TKA) is an effective treatment option for high BMI patients achieving similar outcomes to non-obese patients. However, increased rates of aseptic loosening in patients with a high BMI have been reported. In patients with high BMI/body mass there is an increase in strain placed on the implant fixation interfaces. As such component fixation is a potential concern when performing TKA in the obese patient. To address this concern the use of extended tibial stems in cemented implants or cementless fixation have been advocated. Extend tibial stems are thought to improve implant stability reducing the micromotion between interfaces and consequently the risk of aseptic loosening. Cementless implants, once biologic fixation is achieved, effectively integrate into bone eliminating an interface. This retrospective study compared the use of extended tibial stems and cementless implants to conventional cemented implants in high BMI patients. Methods. From a prospectively maintained database of 3239 primary Attune TKA (Depuy, Warsaw, Indiana), obese patients (body mass index (BMI) >30 kg/m²) were retrospectively reviewed. Two groups of patients 1) using a tibial stem extension [n=162] and 2) cementless fixation [n=163] were compared to 3) a control group (n=1426) with a standard tibial stem cemented implant. All operations were performed by or under the direct supervision of specialist arthroplasty surgeons. Analysis compared the groups with respect to class I, II, and III (BMI >30kg/m², >35 kg/m², >40 kg/m²) obesity. The primary outcome measures were all-cause revision, revision for aseptic loosening, and revision for tibial loosening. Kaplan-Meier survival analysis and Cox regression models were used to compare the primary outcomes between groups. Where radiographic images at greater than 3 months post-operatively were available, radiographs were examined to compare the presence of peri-implant radiolucent lines. Results. The mean follow-up of 4.8, 3.4, and 2.5 years for cemented, stemmed, and cementless groups respectively. In total there were 34 all-cause revisions across all the groups with revision rates of 4.55, 5.50, and 0.00 per 1000-implant-years for cemented, stemmed, and cementless groups respectively. Survival Analysis did not show any significant differences between the three groups for all-all cause revision. There were 6 revisions for aseptic loosening (5 tibial and 1 femoral); all of which were in the standard cemented implant group. In contrast there were no revisions in the stemmed or cementless implant groups, however, this was not significant on survival analysis. Analysis looking at class I, II, and III obesity also did not show any significant differences in survival for all cause revision or aseptic loosening. Conclusion. This retrospective analysis showed that there were no revisions required for aseptic loosening when either a cemented stemmed or cementless implant were used in obese patients. These findings are in line with other studies showing that cementless fixation or extended stem implants are a reasonable option in obese patients who represent an increasing cohort of patients requiring TKR. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Introduction. Wear of polyethylene continues to be a significant factor in the longevity of total knee replacement (TKR). Moderately cross-linked polyethylene has been employed to reduce the wear of knee prostheses, and more recently anti-oxidants have been introduced to improve the long-term stability of the polyethylene material. This is the initial study of the wear of a new anti-oxidant polyethylene and a new TKR design, which has modified femoral condylar geometry. Materials and Methods. The wear of a new TKR the Attune knee was investigated using a physiological six station Prosim knee wear simulator (Simulator Solutions, UK). Six mid-size Attune fixed bearing cruciate retaining TKRs (DePuy Inc, Warsaw, USA) were tested for a period of 6 million cycles. The inserts were manufactured from AOX™, a compression moulded GUR1020 polyethylene incorporating Covernox™ solid anti-oxidant. The AOX polymer was irradiated to 8M Rad, to give a moderately cross-linked material. High and intermediate kinematics, under anterior-posterior displacement control were used for this study (McEwen et al 2005). The maximum femoral axial loading was 2600N, with flexion-extension of 0 to 58°, an anterior-posterior displacement of 0–10 mm for high kinematics and 0–5 mm for intermediate, and an internal-external rotation of ±5°. The lubricant was 25% (v/v) calf serum supplemented with 0.03% (v/v) sodium azide solution in deionised water, as an antibacterial agent, and was changed approximately every 0.33 Mc. Wear was assessed gravimetrically and moisture uptake was assessed using unloaded soak controls. Volumetric wear was calculated using a density of 0.94 mg/mm. 3. , and compared with a previous study examining the Sigma XLK TKR design which uses moderately crosslinked polyethylene which is in current clinical use (Brockett et al 2012). Results. The mean wear as a function of cycles, under high and intermediate kinematics is indicated in Figure 1. There was a significant reduction in wear rate with intermediate kinematics. The mean wear rate for the Attune TKR under high kinematics (0–3 Mc) was 6.27±1.03 mm. 3. /Mc, and during the intermediate kinematics (3–6 Mc) was 4.63 ±1.01 mm. 3. /Mc. These wear rates were comparable to previously reported data for a moderately cross-linked UHMWPE Sigma TKR (Figure 2, Brockett et al 2012) under high kinematics. Under intermediate kinematics there was a small but significant difference between the wear rates (ANOVA, p<0.05). Discussion. A new Attune design TKR has a new bearing material and a new femoral geometry was examined through experimental wear simulator studies, and compared with a previously reported study conducted under the same test conditions. The wear performance of the new Attune TKR was comparable with the Sigma XLK bearing under high kinematics, but higher under intermediate kinematics. This study has examined the short term wear performance of the implant, and found it to be a low wear option for TKR. The longer-term potential advantages offered by a more oxidatively stable material will be investigated in the future

Introduction. Anterior knee pain (AKP) is a recognized cause of patient's dissatisfaction after total knee arthroplasty. Potential implant/technique related contributors to AKP are patellofemoral maltracking, trochlear geometry, femoral malrotation, patellar tilt and overstuffing. The primary aim of this prospective, matched pair study was to assess the safety, efficacy and performance of an anatomic patella and its effect on AKP in in a matched pair analysis. Material and Methods. Between July 2012 and May 2013, 55 consecutive posterior stabilized cemented Attune TKAs (Depuy) were matched to the PFC Sigma group based on age, gender, and body mass index (BMI). All surgeries were performed via medial parapatellar approach with patellar resurfacing. Clinical and radiographic analysis was performed prospectively with minimum 6 month follow-up. Radiographic measurements included overall limb alignment, anterior offset, posterior offset, joint line, patellar thickness, patellar tilt and patellar displacement by two independent observers. Results. The mean functional outcomes were similar in both groups. AKP incidence between Attune and PFC was statistically insignificant (3.6% and 3.8%). Radiographic analysis revealed no mal-alignment, or osteolysis. No complications such as infection, patellar fracture, subluxation or dislocations were observed. Discussion. Attune knee design demonstrates excellent short-term safety and efficacy. At minimum 6-month follow-up, anatomical patella with shows less AKP than single radius patella design. Longer follow-up is required to assess functional outcome this design

Introduction. For many patients, total knee replacement (TKR) provides pain relief and restores motion for many years [1]. Some patients, however, experience early failures and require revision surgery. One of the suggested contributors to early failure has been excessive wear due to malalignment [2]. Previous work has shown that varus-valgus malalignment results in extreme condylar loading and could lead to high wear [3]. The purpose of this experiment, therefore, was to evaluate medial/lateral load sharing in an in vitro wear simulation. Methods. Wear testing was conducted on midsized Attune and Sigma fixed bearing cruciate substituting TKR components (DePuy Synthes). The two systems differ in many aspects; notably, Attune employs antioxidant-stabilized moderately-crosslinked polyethylene and a gradually changing sagittal femoral curvature while Sigma uses remelted moderately-crosslinked polyethylene and a mulit-radius femoral design. Wear was evaluated across a wide range of medial/lateral (M/L) load splits: 10/90, 60/40, and 90/10 using an AMTI six-station knee simulator (Figure 1). Simulation was conducted for 3 million cycles using at 1 Hz using previously described methods [4] with ‘High Kinematic’ displacement controlled inputs in 25% bovine calf serum (Hyclone) at 37 ± 2°C supplemented with sodium azide and EDTA. Polyethylene wear was determined gravimetrically with load soak compensation every 0.5 Mcyc. Results. The wear of Attune and Sigma components were consistently low across all load splits (Figure 2). The standard 60/40 load split was the lowest wearing condition for both designs, but the extreme lateralized and medialized loadings were not appreciably higher (Figure 3). No statistics are available due to the small sample size. Conclusion. The medial/lateral load sharing did not affect wear for Attune and Sigma designs in this displacement controlled in vitro wear simulation. For each group, the inserts subjected to extreme load splits wore comparably to those with a standard 60/40 load split. It is important to note that all samples experienced similar motions with similar cross-shear and differed primarily in the condylar load sharing. With this in mind, the relationship of the results is supported by research in fundamental polyethylene behavior that suggests cross-shear may dominate loading effects [5]. Clinically, however, patients will likely experience altered motions and other effects due to malalignment that were not investigated in this study. While this study showed limited variation in wear across a wide range of condylar load ratios, surgeons and device manufacturers should continue to explore the full implications of malalignment