Aims. Loosening of components after total knee arthroplasty (TKA) can be associated with the development of radiolucent lines (RLLs). The aim of this study was to assess the rate of formation of RLLs in the cemented original design of the ATTUNE TKA and their relationship to loosening. Methods. A systematic search was undertaken using the Cochrane methodology in three online databases: MEDLINE, Embase, and CINAHL. Studies were screened against predetermined criteria, and data were extracted. Available National Joint Registries in the Network of Orthopaedic Registries of Europe were also screened. A random effects model meta-analysis was undertaken. Results. Of 263 studies, 12 were included with a total of 3,861 TKAs. Meta-analysis of ten studies showed high rates of overall tibial or femoral RLLs for the cemented original design of the ATTUNE TKA. The overall rate was 21.4% (95% confidence interval (CI) 12.7% to 33.7%) for all types of design but was higher for certain subgroups: 27.4% (95% CI 13.4% to 47.9%) for the cruciate-retaining type, and 29.9% (95% CI 15.6% to 49.6%) for the fixed-bearing type. Meta-analysis of five studies comparing the ATTUNE TKA with other implants showed a significantly higher risk of overall tibial or femoral RLLs (odds ratio (OR) 2.841 (95% CI 1.219 to 6.623); p = 0.016) for the ATTUNE. The rates of loosening or revision for loosening were lower, at 1.2% and 0.9% respectively, but the rates varied from 0% to 16.3%. The registry data did not report specifically on the original ATTUNE TKA or on revision due to loosening, but ‘all-cause’ five-year revision rates for the cemented ATTUNE varied from 2.6% to 5.9%. Conclusion. The original cemented ATTUNE TKA has high rates of RLLs, but their clinical significance is uncertain given the overall low associated rates of loosening and revision. However, in view of the high rates of RLLs and the variation in the rates of loosening and revision between studies and registries, close surveillance of patients who have undergone TKA with the original ATTUNE system is recommended. Cite this article: Bone Joint J 2023;105-B(6):610–621

Aims. Conflicting clinical results are reported for the ATTUNE Total Knee Arthroplasty (TKA). This randomized controlled trial (RCT) evaluated five-year follow-up results comparing cemented ATTUNE and PFC-Sigma cruciate retaining TKAs, analyzing component migration as measured by radiostereometric analysis (RSA), clinical outcomes, patient-reported outcome measures (PROMs), and radiological outcomes. Methods. A total of 74 primary TKAs were included in this single-blind RCT. RSA examinations were performed, and PROMs and clinical outcomes were collected immediate postoperatively, and at three, six, 12, 24, and 60 months’ follow-up. Radiolucent lines (RLLs) were measured in standard anteroposterior radiographs at six weeks, and 12 and 60 months postoperatively. Results. At five-year follow-up, RSA data from 61 patients were available and the mean maximum total point motion (MTPM) of the femoral components were: ATTUNE: 0.96 mm (95% confidence interval (CI) 0.79 to 1.14) and PFC-Sigma 1.37 mm (95% CI 1.18 to 1.59) (p < 0.001). The PFC-Sigma femoral component migrated more in the first postoperative year, but stabilized thereafter. MPTM of the tibial components were comparable at five-year follow-up: ATTUNE 1.12 mm (95% CI 0.95 to 1.31) and PFC-Sigma 1.25 mm (95% CI 1.07 to 1.44) (p = 0.438). RLL at the medial tibial implant-cement interface remained more prevalent for the ATTUNE at five-year follow-up compared to the PFC-Sigma (20% vs 3%). RLL did not progress over time, and varied between patients at different timepoints for both TKA systems. Clinical outcomes and PROMs improved compared with preoperative scores, and were not different between groups. Conclusion. MTPM migration at five-year follow-up of the femoral and tibial component of the ATTUNE were similar and as low as that of the PFC-Sigma. MTPM migration of both knee implants did not significantly change from one year post-surgery, indicating stable fixation. Long-term ATTUNE performance may be expected to be comparable to the clinically well-performing PFC-Sigma. We have not found evidence of increased tibial component migration as measured by RSA to support concerns about cement debonding and a higher risk of aseptic loosening with the ATTUNE TKA. Cite this article: Bone Joint J 2023;105-B(11):1168–1176

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

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

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

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. The primary aim of this study was to compare the migration of the femoral and tibial components of the cementless rotating platform Attune and Low Contact Stress (LCS) total knee arthroplasty (TKA) designs, two years postoperatively, using radiostereometric analysis (RSA) in order to assess the risk of the development of aseptic loosening. A secondary aim was to compare clinical and patient-reported outcome measures (PROMs) between the designs. Methods. A total of 61 TKAs were analyzed in this randomized clinical RSA trial. RSA examinations were performed one day and three, six, 12, and 24 months postoperatively. The maximal total point motion (MPTM), translations, and rotations of the components were analyzed. PROMs and clinical data were collected preoperatively and at six weeks and three, six, 12, and 24 months postoperatively. Linear mixed effect modelling was used for statistical analyses. Results. The mean MTPM two years postoperatively (95% confidence interval (CI)) of the Attune femoral component (0.92 mm (0.75 to 1.11)) differed significantly from that of the LCS TKA (1.72 mm (1.47 to 2.00), p < 0.001). The Attune femoral component subsided, tilted (anteroposteriorly), and rotated (internal-external) significantly less. The mean tibial MTPM two years postoperatively did not differ significantly, being 1.11 mm (0.94 to 1.30) and 1.17 mm (0.99 to 1.36, p = 0.447) for the Attune and LCS components, respectively. The rate of migration in the second postoperative year was negligible for the femoral and tibial components of both designs. The mean pain-at-rest (numerical rating scale (NRS)-rest) in the Attune group was significantly less compared with that in the LCS group during the entire follow-up period. At three months postoperatively, the Knee injury and Osteoarthritis Outcome Physical Function Shortform score, the Oxford Knee Score, and the NRS-activity scores were significantly better in the Attune group. Conclusion. The mean MTPM of the femoral components of the cementless rotating platform Attune was significantly less compared with that of the LCS design. This was reflected mainly in significantly less subsidence, posterior tilting, and internal rotation. The mean tibial MTPMs were not significantly different. During the second postoperative year, the components of both designs stabilized and low risks for the development of aseptic loosening are expected. Cite this article: Bone Joint J 2023;105-B(2):148–157

Aims. The aim of this study was to investigate whether wear and backside deformation of polyethylene (PE) tibial inserts may influence the cement cover of tibial trays of explanted total knee arthroplasties (TKAs). Methods. At our retrieval centre, we measured changes in the wear and deformation of PE inserts using coordinate measuring machines and light microscopy. The amount of cement cover on the backside of tibial trays was quantified as a percentage of the total surface. The study involved data from the explanted fixed-bearing components of four widely used contemporary designs of TKA (Attune, NexGen, Press Fit Condylar (PFC), and Triathlon), revised for any indication, and we compared them with components that used previous generations of PE. Regression modelling was used to identify variables related to the amount of cement cover on the retrieved trays. Results. A total of 114 explanted fixed-bearing TKAs were examined. This included 76 used with contemporary PE inserts which were compared with 15 used with older generation PEs. The Attune and NexGen (central locking) trays were found to have significantly less cement cover than Triathlon and PFC trays (peripheral locking group) (p = 0.001). The median planicity values of the PE inserts used with central locking trays were significantly greater than of those with peripheral locking inserts (205 vs 85 microns; p < 0.001). Attune and NexGen inserts had a characteristic pattern of backside deformation, with the outer edges of the PE deviating inferiorly, leaving the PE margins as the primary areas of articulation. Conclusion. Explanted TKAs with central locking mechanisms were significantly more likely to debond from the cement mantle. The PE inserts of these designs showed characteristic patterns of deformation, which appeared to relate to the manufacturing process and may be exacerbated in vivo. This pattern of deformation was associated with PE wear occurring at the outer edges of the articulation, potentially increasing the frictional torque generated at this interface. Cite this article: Bone Joint J 2021;103-B(12):1791–1801

Aims. To establish our early clinical results of a new total knee arthroplasty (TKA) tibial component introduced in 2013 and compare it to other designs in use at our hospital during the same period. Methods. This is a retrospective study of 166 (154 patients) consecutive cemented, fixed bearing, posterior-stabilized (PS) TKAs (ATTUNE) at one hospital performed by five surgeons. These were compared with a reference cohort of 511 knees (470 patients) of other designs (seven manufacturers) performed at the same hospital by the same surgeons. There were no significant differences in age, sex, BMI, or follow-up times between the two cohorts. The primary outcome was revision performed or pending. Results. In total, 19 (11.5%) ATTUNE study TKAs have been revised at a mean 30.3 months (SD 15), and loosening of the tibial component was seen in 17 of these (90%). Revision is pending in 12 (7%) knees. There was no difference between the 31 knees revised or with revision pending and the remaining 135 study knees in terms of patient characteristics, type of bone cement (p = 0.988), or individual surgeon (p = 0.550). In the reference cohort, there were significantly fewer knees revised (n = 13, 2.6%) and with revision pending (n = 8, 1.5%) (both p < 0.001), and only two had loosening of the tibial component as the reason for revision. Conclusion. This new TKA design had an unexpectedly high early rate of revision compared with our reference cohort of TKAs. Debonding of the tibial component was the most common reason for failure. Additional longer-term follow-up studies of this specific component and techniques for implantation are warranted. The version of the ATTUNE tibial component implanted in this study has undergone modifications by the manufacturer. Cite this article: Bone Joint J 2021;103-B(6 Supple A):137–144

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

The June 2023 Knee Roundup. 360. looks at: Cementless total knee arthroplasty is associated with early aseptic loosening in a large national database; Is cementless total knee arthroplasty safe in females aged over 75 years?; Could novel radiological findings help identify aseptic tibial loosening?; The Attune cementless versus LCS arthroplasty at introduction; Return to work following total knee arthroplasty and unicompartmental knee arthroplasty; Complications and downsides of the robotic total knee arthroplasty; Mid-flexion instability in kinematic alignment better with posterior-stabilized and medial-stabilized implants?; Patellar resurfacing does not improve outcomes in modern knees

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