Total Knee Arthroplasty Designs Research Articles

Correlation between tibial valgus deformity and aspect ratio of resected tibial surface in female Chinese patients undergoing total knee arthroplasty.

Morphology of the resected tibial surface is the reference for tibial component design, selection, and implantation in total knee arthroplasty (TKA). This comparative study sought to answer whether valgus deformity of the tibia would affect the morphology of the resected tibial surface in TKA. Thirty-one female Chinese patients with valgus tibias were retrospectively and consecutively identified from a single-center registration database. Thirty-one patients with well-aligned tibias were matched in terms of gender, height, and weight. Weight-bearing full-length radiographs and computed tomography images of the whole lower limb were obtained for every case. Tibial resection was mimicked perpendicular to the mechanical axis of the tibia in the frontal plane with 3° of posterior slope and a cut level individualized by the actual intraoperative cut. On the resected surface, mediolateral dimension (MLD), medial anteroposterior dimensions (mAPD), and lateral anteroposterior dimensions (lAPD) were measured, and aspect ratios (AR) were calculated. We compared the AR between the two groups. The aspect ratio of resected tibial surface positively correlated with tibial valgus alignment. Patients with valgus tibias had significantly smaller AR (MLD/mAPD) for the medial plateau (1.50 ± 0.06 vs. 1.54 ± 0.07, P = 0.032). However, the AR for the lateral plateau was similar between the two groups (1.63 ± 0.08 vs. 1.65 ± 0.07, P = 0.328). This difference in morphology of resected tibial surface between valgus and well-aligned tibias should be considered in tibial component design, as well as in the selection and placement of TKA implants for knees with valgus tibias.

Native knee kinematics is not reproduced after sensor guided cruciates substituting total knee arthroplasty

PurposeGait analysis was used to evaluate knee kinematics in patients who underwent successful primary total knee arthroplasty (TKA) using two modern bi-cruciate substituting designs. The knee joint was balanced intraoperatively using real-time sensor technology, developed to provide dynamic feedback regarding stability and tibiofemoral load. The authors hypothesized that major differences exist in gait parameters between healthy controls and post-TKA patients.MethodsTen patients who underwent successful TKA using bi-cruciate substituting designs were evaluated at a minimum of 9 months postoperatively using three-dimensional knee kinematic analysis; a multi-camera optoelectronic system and a force platform were used. Sensor-extracted kinematic data included knee flexion angle at heel-strike (KFH), peak midstance knee flexion angle (MSKFA), maximum and minimum knee adduction angle (KAA) and knee rotational angle at heel-strike. Multiple gait analysis data from the study group were compared to a group of ten healthy controls who were matched by age, sex and BMI. Clinical outcome in the TKA group was also measured using the Knee injury and Osteoarthritis Outcome Score (KOOS).ResultsClinically, at final follow-up, a statistically significant difference in pain, general symptoms, and activities of daily living was seen between the groups. From a gait analysis standpoint, TKA patients had significantly less rotation at heel strike (p = 0.04), lower late stance peak extension moments (p = 0.02), and less Knee Adduction Angle excursion during swing phase (p = 0.04) compared to the control group. No statistically significant difference was observed for knee flexion angle at heel strike, knee adduction moment, or peak knee flexion moment between the groups.ConclusionsModern bi-cruciate substituting TKA designs failed to reproduce normal knee kinematics. The lack of full knee extension during the stance phase, absence of the “screw-home mechanism” typical of an ACL functioning knee, and the reduced fluctuation in knee adduction angle during the swing phase still represent major proprioceptive and muscular recruitment differences between normal and replaced knees.

"Nailable" Does Not Always Mean Reducible in Distal Femur Fractures: Arthroplasty Component and Nail Design Matter.

Distal femur fractures above a total knee arthroplasty (TKA) are challenging. These fractures can be fixed with a retrograde intramedullary nail (rIMN), but the design of the femoral component of the TKA influences the starting point for an rIMN. We performed a biomechanical study to evaluate how different TKA components influence the starting point for an rIMN and how that can lead to a deformity in the sagittal plane. We simulated a distal femur fracture with three different arthroplasty components. We used three different implants to simulate fracture reduction and measured the resultant sagittal plane deformity. Low and moderate femoral component ratio (FCR) design components were able to maintain fracture alignment within 5° of anatomic. High FCR component (more posterior starting point) sagittal plane deformities of up to 15° were observed with both the straight and medium Herzog bend nails, which was statistically significant (P<.001). Use of a high Herzog bend nail decreased the deformity by an average of 6°, which was statistically significant (P<.001). There is variability in how the TKA design affects the starting point and thus the sagittal plane alignment after fixation. This study helps quantify the effect of arthroplasty component design on fracture alignment. [Orthopedics. 2023;46(1):35-38.].

Posterior-stabilized total knee arthroplasty kinematics and joint laxity: A hybrid biomechanical study

BackgroundPosterior-stabilized (PS)-total knee arthroplasty (TKA) arose as an alternative to cruciate-retaining (CR)-TKA in the 1970s. Since then, it has become a popularly utilized TKA design with outcomes comparable to CR-TKA. The post-cam mechanism is unique to PS-TKA as it substitutes the function of the posterior cruciate ligament (PCL). The study aimed to understand the kinematic and laxity changes in PS-TKA with under- and overstuffing of the tibiofemoral joint space with the polyethylene (PE) insert.MethodsThis study employed a hybrid computational-experimental joint motion simulation on a VIVO 6 degrees of freedom (6-DoF) joint motion simulator (AMTI, Watertown, MA, USA). Physical prototypes of a virtually-performed TKA in mechanical alignment (MA) and kinematic alignment (KA) based on cadaveric CT scans and a virtual ligament model were utilized. The reference, understuffed (down 2 mm) and overstuffed (up 2 mm) joint spaces were simulated, neutral flexion and laxity testing loads and motions were performed for each configuration.ResultsThe PE insert thickness influenced post-cam engagement, which occurred after 60º in the overstuffed configurations, after 60º–75º in the reference configurations and after 75º in the understuffed configurations. The understuffed configurations, compared to the reference configurations, resulted in a mean 2.0º (28%) and 2.0º (31%) increase in the coronal laxity in MA and KA respectively. The overstuffed configurations, compared to the reference configuration, resulted in an increase in the mean joint compressive forces (JCFs) by 73 N (61%) and 77 N (62%) in MA and KA models, respectively.ConclusionsThe under- and overstuffing in PS-TKA alter the kinematics with variable effects. Understuffing decreases the stability, JCFs and inverse with overstuffing. Subtle changes in the PE insert thickness alter the post-cam mechanics.

Short-Term Surface Damage Mechanisms of Retrieved Highly Cross-Linked Polyethylene Patellar Components

BackgroundPrevious retrieval studies of patellar components for total knee arthroplasty focused on historical designs and polyethylene materials that are no longer clinically relevant. Therefore, this study aimed to compare revision reasons and surface damage mechanisms of conventional, gamma inert sterilized polyethylene and highly cross-linked polyethylene (HXLPE) patellar components in contemporary designs from a single manufacturer. MethodsA total of 114 gamma inert and 76 HXLPE patellar components were gathered in a multicenter orthopaedic implant retrieval program. Patient age and body mass index were similar between cohorts (P = .27 and P = .42, respectively); however, the gamma inert cohort was implanted longer (μdifference = 3.1 years; P = .005). A matched subset was created based on the total knee arthroplasty design, patellar shape, and implantation time. Revision reasons were gathered from revision operating notes, and surface damage was examined via the Hood scoring method. Differences between HXLPE and gamma inert cohorts were evaluated using Mann-Whitney U-tests. ResultsThe most common revision reasons were infection, loosening, and instability, with the most common patellar complication resulting in revision being patellar loosening for both cohorts with similar incidences for both (chi-square; P = .60, P = .59). The most common surface damage modes were burnishing, scratching, and pitting in both cohorts. Total surface damage was significantly higher in the gamma inert components (P = .02), but not in the matched subset (P = .46). ConclusionOverall, the clinical performance of HXLPE was similar to that of conventional polyethylene for patellar components with short implantation times. While this study provides much needed information on the performance of HXLPE patellae in short-term retrievals, long-term studies are still needed.

Does Posterior Tibial Slope Influence Knee Kinematics in Medial Stabilized TKA?

During total knee arthroplasty (TKA), one of the key alignment factors to pay attention to is the posterior tibial slope (PTS). The PTS clearly influences the kinematics of the knee joint but must be adapted to the coupling degree of the specific TKA design. So far, there is hardly any literature including clear recommendations for how surgeons should choose the PTS in a medial stabilized (MS) TKA. The aim of the present study is to investigate the effects of different degrees of PTS on femorotibial kinematics in MS TKA. An MS TKA was performed in seven fresh-frozen human specimens successively with 0°, 3°, and 6° of PTS. After each modification, weight-bearing deep knee flexion (30-130°) was performed, and femorotibial kinematics were analyzed. A lateral femoral rollback was observed for all three PTS modifications. With an increasing PTS, the tibia was shifted more anteriorly on the lateral side (0° PTS anterior tibial translation -9.09 (±9.19) mm, 3° PTS anterior tibial translation -11.03 (±6.72) mm, 6° PTS anterior tibial translation 11.86 (±9.35) mm). No difference in the tibial rotation was found for the different PTS variants. All PTS variants resulted in internal rotation of the tibia during flexion. With a 3° PTS, the design-specific medial rotation point was achieved more accurately. According to our findings, we recommend a PTS of 3° when implanting the MS prosthesis used in this study.

What's New in Adult Reconstructive Knee Surgery.

What's New in Adult Reconstructive Knee Surgery.

Asymmetry of Posterior Condyles in Resection Plane and Axial Curvature for Total Knee Arthroplasty.

Understanding the morphology of the distal femur is essential for improving bone-implant match in total knee arthroplasty (TKA) and understanding the mechanisms behind knee kinematics. However, little is known about the asymmetry of the posterior condyles. Thus, this study aimed to thoroughly investigate asymmetries in sizes and shapes between the medial and lateral posterior condyles before and after femoral resections during TKA in osteoarthritic (OA) knees. Three-dimensional femoral models of 74 OA knees were constructed using computed tomography images. The morphologic measurements of the posterior condyle pre- and post-simulated osteotomy for TKA included the radii of the posterior condyles fitted to a circle on the sagittal and axial planes of the femoral coordinate system, the inclination angle of the articular surface and resected surface, and the width and height of the resected surface. Differences in the data were assessed using Student's t-test, and correlations were evaluated using the Pearson product-moment correlation. The radii of the medial posterior condyles fitted to the circle were, on average, 6 mm larger than those of the lateral condyles on the axial plane (p < 0.001) and 0.7 mm smaller than those of the lateral condyles on the sagittal plane (p=0.046). The inclination angles of the medial and lateral posterior condyles on the axial plane were significantly different with both pre-simulated and post-simulated osteotomy, respectively (both p < 0.001). The resected plane of the lateral posterior condyles displaced opposite inclination directions between the distal and proximal portions. Neither heights or widths of the medial posterior condyles were significantly different from those of their lateral counterparts (both p > 0.107). This study found asymmetrical inclination of the resected surface and coronal radii between the medial and lateral posterior condyles, which may relate to the posterolateral overhang of the lateral condyle after TKA and the progression of the knee OA. These findings provides valuable morphological information and may help improve the implant designs for TKA.

A review on flexion angle in high-flexion total knee arthroplasty for indonesian’s need

Total Knee Arthroplasty (TKA) proposed as an alternative treatment for damaged knee joints of humans is reviewed. The commercial application of TKA can help patients to improve their daily normal activities. Here the high-flex type total knee arthroplasty (High-Flex TKA) is typically designed for the patient’s convenience on which the greater range of motion can be adjusted for extreme activities such as Seiza and Muslim praying. However, the present High-Flex TKAs have not fulfilled the needs of Indonesians for religious activities with a flexion angle of 150°–165°. Therefore, this review aims to examine the flexion range of High-Flex TKAs proposed for the needs of Indonesians. This study is a narrative review, all studies published and reviewed are related to the range of flexion angles on the use of products from many manufacturers and various types that have been used by patients, as well as the development of a CAD-based TKA design. It was proposed in the present study that the flexion angle on High-Flex TKAs may be optimized by thickening the posterior femoral condyle, creating a medial pivot system, and applying a single radius system on the femoral component. Whereas, the tibial insert component could be designed by setting up the posterior tibial slope, and creating a post-cam stabilizer mechanism. Many knowledge gaps related to the population of research objects, lack of research on extreme angles, development of TKA components, are discussed. Further needs of extensive research on TKA in Mongoloid races are anticipated to be introduced for extreme angles and most comprehensive product development for optimization of the flexion angle.

Does a Uni "Feel Better" than a Total Knee? Not Necessarily, When Using Modern Implant Designs.

Background: When comparing functional outcomes of patients with unicompartmental knee arthroplasty (UKA) versus total knee arthroplasty (TKA), studies often report the UKA as the preferred procedure; however, recent improvements in the design of modern TKA implants have aimed at narrowing this gap. Purpose: We sought to compare the "feel" of modern TKA implants to that of UKA, using the Forgotten Joint Score (FJS), a validated patient-reported outcome measure. Methods: We performed a retrospective review of patients who underwent TKA and UKA at 2 institutions between 2014 and 2017. All UKA procedures were robotic arm-assisted with a single implant, "traditional TKAs" were performed using traditional posterior-stabilized implants, and "modern TKAs" were performed using posterior-stabilized implants with a modern design. Differences in FJS were assessed using 1-way analysis of variance and independent 2-sample t tests. Results: A total of 600 patients were included in our study, with 200 patients in each surgical subcategory. Mean age was 62.8 ± 10.2 years and mean body mass index was 29.9 ± 4.9. Modern TKA and UKA had similar FJS at 1 year. While modern TKA had a significantly higher FJS than traditional TKA, UKA did not have a significantly higher FJS than traditional TKA. Conclusion: Our retrospective analysis found no significant differences in the FJS of patients who underwent UKA and TKA with a modern design; however, both had superior scores than traditional TKA designs. This finding suggests that modern TKA designs may have the potential to achieve the natural feeling that is typically associated with joint-conserving surgeries such as UKA, although longer follow-up is necessary.

Prospective sequential comparison of femoral roll-back between cruciate-retaining and posterior-stabilized total knee arthroplasty using an intra-operative sensor

BackgroundImplant design and surgical techniques affect postoperative knee kinematics in total knee arthroplasty (TKA). This study aimed to compare femoral roll-back between cruciate-retaining (CR) and posterior-stabilized (PS) TKA in the same knee by objectively quantifying the contact point kinematics of the tibiofemoral joint using a sensor. MethodsIn the present prospective study, we used an intraoperative sensor to compare medial and lateral roll-back during 0-120° knee flexion in 33 knees that underwent CR and PS TKA. We also examined the relationship between mediolateral balance and the lateral-to-medial roll-back ratio. We defined the contact percentage position as the vertical length to the contact point divided by the anteroposterior length of the tibial plate. ResultsThe roll-back percentage following PS TKA (19.8 ± 5.1%) was significantly higher than that after CR TKA in both the medial (19.8 ± 5.1% versus 7.1 ± 2.5%, P < 0.001) and lateral (26.8% ± 3.8% versus 18.7 ± 3.8%, P < 0.001) compartments. The medial contact pressure at 90° was significantly correlated with the increased lateral-to-medial roll-back ratio in both CR and PS TKA (both P < 0.001). ConclusionPS TKA resulted in a higher percentage of femoral roll-back in the medial and lateral compartments than CR TKA. CR TKA caused a higher lateral-to-medial roll-back ratio compared to PS TKA. To reproduce medial pivot knee motion similar to that of a normal knee, the medial soft tissue needed to be balanced more tightly than the lateral soft tissue during TKA. These findings provide some clinical evidence of TKA design selection and proper mediolateral balancing for successful TKA.

Bicruciate-Retaining Total Knee Arthroplasty: State of the Art for the Younger and Active Population? A Systematic Review and Future Prospective

(1) Background: Total knee arthroplasty (TKA) is a well-established surgical treatment for end-stage osteoarthritis. While no leading factor can be identified, the high frequency of patient dissatisfaction (20%) pertains to several key features such as preoperative expectations and postoperative improvement in knee function. Bicruciate-retaining total knee arthroplasty (BCR-TKA) may improve kinematics and lead to improved clinical outcome in the higher-demanding patients. (2) Methods: A systematic review of the literature was performed to assess the best available preclinical and clinical literature on BCR-TKA for kinematics and clinical outcome and adverse events such as implant loosening. Articles were screened using predefined in- and exclusion criteria. The guidelines for Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) were used. (3) Results: The literature search resulted in 352 articles which were screened for title and abstract. After application of the in- and exclusion criteria, 13 preclinical and 30 clinical articles were included. The methodological quality of studies was low, including mainly level IV studies. (4) Conclusions: This is the first report that provides a systematic description of the broad available preclinical and clinical literature on BCR-TKA. It underlines the current interest in improving kinematics and clinical outcome based on a more anatomical TKA design. The current review demonstrates the low methodological quality of clinical trials that have investigated BCR-TKA. Currently, there are insufficient data to support broad (“state of the art”) implantation of BCR-TKA. Preclinical and clinical research suggest, however, that the design has a potential benefit to achieve improved kinematics in the young and active arthroplasty patient and warrants future research for new-generation designs with optimal (tibial) fixation and reproducible (robot or navigated) surgical placement.

Selective Patella Resurfacing in Contemporary Cruciate Retaining and Substituting Total Knee Arthroplasty: A Matched Cohort Analysis

BackgroundLeaving the patella unresurfaced in total knee arthroplasty (TKA) is increasing due to modern patella-friendly implants, awareness that complications are not uncommon with resurfacing, and knowledge that historical studies were scientifically confounded. This study examined the effect of selective patellar resurfacing on patient-reported outcome measures (PROMs) using modern implants and techniques in cohorts rigorously matched for demographics and osteoarthritis severity. MethodsA total of 166 TKAs performed without patellar resurfacing were case-control matched to 166 TKAs with patella resurfacing. Case-control matching was based on demographics, American Society of Anesthesiology Physical Status, comorbidities, and osteoarthritis severity. No significant differences were observed between cohorts for demographics (P ≥ .347), comorbidities (P ≥ .443), or radiographic osteoarthritis severity (P ≥ .078). Radiographic alignment and prospectively collected PROMs were evaluated preoperatively and at latest clinical follow-up. ResultsPreoperatively, patellar tilt was less for the unresurfaced patella group (3 versus 4°, P = .003); however, postoperative patellar tilt was not different (3 versus 3°, P = .225). At a mean of 2.1 years follow-up (range, 1 to 7), University of California Los Angeles Activity Level was significantly higher for the unresurfaced patella group (6.3 versus 5.5, P = .002), but the mean group difference did not reach a minimal clinically important difference. There were no other significant differences in PROMs or reoperation rates between cohorts (P ≥ .135). ConclusionIn contemporary cruciate retaining and substituting TKA designs, not resurfacing the patella in select patients may achieve comparable PROMs and re-operation rates; and potentially greater activity level compared to patella resurfacing at early follow-up. Level of EvidenceIII.

Thicker polyethylene inserts (≥ 13 mm) increase the risk for early failure after primary cruciate-retaining total knee arthroplasty (TKA): a single-centre study of 7643 TKAs

PurposeThis study investigates whether thicker (PE) inserts lead to a greater risk for revision after TKA. The differences between the TKA designs of three manufacturers (NexGen, PFC Sigma, Triathlon) are also compared.MethodsA total of 7643 primary TKA surgeries were included. PE inserts were divided into two groups—“thick PE inserts” with a thickness of 13 mm (mm) or more and “standard PE inserts” with a thickness of less than 13 mm. Three cruciate-retaining (CR) TKA designs (NexGen, PFC Sigma, Triathlon) were included in the study. The differences in failure rates between groups were investigated using Kaplan–Meier survival curves and Cox regression model with hazard ratios (HR). Failure rates were investigated short-term (< 2 years) and long-term (the whole follow-up period). The TKA designs were analysed both together and separately.ResultsDuring the whole follow-up period, there were 184 (2.4%) aseptic revisions. The thick PE insert group showed an increased risk for revision compared to the standard PE insert group in both short-term (< 2 years; HR 2.0, CI 1.3 to 3.2) and long term (> 2 years; HR 1.6, CI 1.1 to 2.3) follow-up. The highest revision rate was observed in patients who received the Triathlon TKA with a thicker PE insert (HR 2.6, CI 1.2 to 5.7).ConclusionThe results indicate that thicker PE inserts are associated with increased risk for revision in primary TKA. Further research is required to ascertain whether more conformed PE inserts or constrained knee designs instead of thick CR inserts will ultimately lead to better clinical outcomes.Level of evidenceIII.

Measurement of Tibial Orientation Helps Select the Optimal Insert Thickness to Personalize PCL Tension in a Medial Ball-in-Socket TKA.

As the conformity of a medial ball-in-socket total knee arthroplasty (TKA) provides intrinsic anterior-posterior (A-P) stability, surgeons cannot rely on the manual examination of sagittal laxity to identify the optimal insert thickness. Instead, the present study determined whether measuring tibial axial orientation in extension and 90° flexion with an insert goniometer could identify the optimal thickness that, when implanted, provides high postoperative function. In twenty-two patients that underwent unrestricted caliper-verified kinematic alignment (KA) with a PCL retaining implant, two surgeons measured tibial orientation in extension and 90° flexion with 10, 11, 12, and 13 mm thick insert goniometers. Each TKA had one insert thickness that restored either the maximum external tibial orientation in extension, the maximum internal tibial orientation at 90° flexion, or both relative to 1 mm thinner and thicker inserts. In addition, the 6-month median [interquartile range] Forgotten Joint Score of 73 (54–87) and Oxford Knee Score of 42 (38–45) indicated high satisfaction and function. In conclusion, surgeons using a medial ball-in-socket TKA design can measure external tibial orientation in extension and internal tibial orientation at 90° flexion with an insert goniometer. Furthermore, implanting an insert with the thickness that provided the maximum orientation values resulted in high postoperative function, thereby personalizing PCL tension.

The Impact of Component Design and Fixation on Stress Shielding After Modern Total Knee Arthroplasty.

Total knee arthroplasty (TKA) tibial baseplate thickness, metallurgy, and implant fixation with cement may influence stress shielding. The purpose of the present study is to compare bone mineral density of 2 cemented and press-fit TKA designs with differing tibial baseplate thicknesses and metallurgy over a 2-year period to assess for changes in stress shielding. One-hundred one TKAs were performed in this Institutional Review Board-approved, prospective study. There were 4 cohorts: DePuy Attune cemented and press-fit, and Stryker Triathlon cemented and press-fit. The Attune tibial baseplate was thicker; both cemented tibial and femoral components were cobalt-chromium. The DePuy Attune press-fit had a cobalt-chromium sintered bead porous coating while the Stryker Triathlon was 3-dimensional printed highly porous titanium alloy. All patients had quantitative dual-energy X-ray absorptiometry scans performed at baseline (4-6 weeks postoperatively) and at 1 and 2 years postoperatively. Stress shielding was evaluated by comparing percent change in bone mineral density in 11 radiographic zones over 2 years. Over a 2-year period, there were no differences in stress shielding on the tibial side in either cemented or press-fit between Stryker Triathlon and DePuy Attune; however, there were differences on the femoral side. The press-fit tibial components of the Stryker Triathlon and DePuy Attune had either similar or less stress shielding over a 2-year period compared to their cemented counterparts. This study comparing 2 TKA implants with differing tibial tray thickness did not find significant differences in tibial stress shielding between designs. There was a difference in stress shielding on the femoral side between designs, suggesting that longer term follow-up is warranted.

Chitranjan S. Ranawat Award: Motion During Total Knee Cementing Significantly Decreases Tibial Implant Fixation Strength.

Aseptic tibial loosening following primary total knee arthroplasty persists despite technique and device-related advancements. The mechanisms for this mode of failure are not well understood. We hypothesized that knee movement while the cement was curing dispersed lipids at the implant-cement interface and would result in decreased tibial fixation strength. A cadaveric study was performed utilizing 32 torso-to-toe specimens (64 knees). Four contemporary total knee arthroplasty designs were evaluated. Each implant design was randomly assigned to a cadaveric specimen pair with side-to-side randomization. Specimen densitometry was recorded. Each tibial implant was cemented using a standard technique. On one side, the tibial component was held without motion following impaction until complete cement polymerization. The contralateral knee tibial implant was taken through gentle range of motion and stability assessment 7 minutes after cement mixing. Axial tibial pull-out strength and interface failure examination was performed on each specimen. The average pull-out strength for the no motion cohort (5,462 N) exceeded the motion cohort (4,473 N) (P= .001). The mean pull-out strength between implant designs in the no motion cohort varied significantly (implant A: 7,230 N, B: 5,806 N, C: 5,325 N, D 3,486 N; P= .007). Similarly, the motion cohort inter-implant variance was significant (P ≤ .001). Intra-implant pull-out strength was significantly higher in implant A than D. The average pull-out strength was significantly lower in specimens that failed at the implant-cement interface vs bone failures (4,089±2,158 N vs 5,960±2,010 N, P < .0025). Knee motion during cement polymerization is associated with significant decreases in tibial implant fixational strength. Reduction in implant pull-out strength was identified with each implant design with motion and varied between designs. Across all tested designs, we recommend limiting motion while cementing the tibial implant to improve fixation strength.

Finite Element Analysis of Contact Stress Distribution on Insert Conformity Design of Total Knee Arthroplasty

The tibial insert conformity is one of the essential parameters concerned with the contact stress distribution of biomechanics characteristics in total knee arthroplasty (TKA). This study aimed to evaluate the effect of tibial insert conformity design on contact stress distribution using Finite Element (FE) analysis. The three-dimensional (3D) FE model of the posterior stabilized type of TKA was analyzed according to the standard knee implant loading. The 3k factorial experimental design was performed for the response surface of different insert curvatures consisting of the curve, partial flat, and flat insert conformity in sagittal and coronal planes. According to the result, the coronal and sagittal plane conformity displayed the effect of the change on the contact stress, including the contact area for the flexion angle of the knee joint. The maximum contact stress increased while the contact area value decreased during the flexion angle of the knee joints raised. The changing insert conformity value in the sagittal plane displayed higher sensitivity to contact stress than the changing conformity in the coronal plane. The relationship between the contact stress and tibial insert conformity under knee flexion angle indicates highly regression suitable for the prediction. In addition, the FE simulation result was then verified by compared to mechanical testing using the Fujifilm technique. The result of FE analysis exhibited similar to that of the mechanical test. The study indicated that the different geometric designs of the insert conformity played a crucial role that influenced and relationship to the contact stress of TKA

Higher use of fixed-bearing over mobile-bearing and posterior-stabilized over medial pivot designs in total knee arthroplasty (TKA): a systematic comparative analysis using worldwide arthroplasty registers from England and Wales, Australia, Norway, New Zealand, Germany and Switzerland

IntroductionThe aim of this study was to compare the use of mobile-bearing, fixed-bearing, posterior-stabilized (PS) and medial pivot design to describe epidemiological differences and subsequent outcomes.Materials and methodsA systematic literature search was performed using the NORE website to identify the relevant arthroplasty registers. Inclusion criteria were the following: (1) reports had to be publicly available, (2) reports had to be written in German or English language, (3) differentiation between mobile- and fixed-bearing, posterior-stabilized, and if possible, medial pivot designs had to be possible from the present reports, and (4) data had to be reported for at least three consecutive years and the latest report had to be from the year 2020 to retrieve recent data.ResultsSix registries (England and Wales, Australia, Norway, New Zealand, Germany, Switzerland) offered sufficient data according to the inclusion criteria. In all countries, the dominant type of bearing used for total knee arthroplasty (TKA) was fixed-bearing, with percentages ranging from 60.8% to 84.1% in 2018, 63.6% to 85.7% in 2019 and 66.2% to 87.4% in 2020. A large variation was observed concerning mobile-bearing design, which showed a range from 2.8% to 39.2% in 2018, 2.6% to 36.4% in 2019 and 2.9% to 33.8% in 2020. Some variation was found regarding the use of PS TKA, as its percentage frequency ranged from 9.7% to 29.2% in 2018, 9.8% to 29.4% in 2019 and 10.1% to 28.5% in 2020. Medial pivot design had a share of 9.1% in 2018, 8.6% in 2019 and 8.4% in 2020 in Australia, while it only accounted for 1.4% in 2018, 2.1% in 2019 and 2.5% in 2020 in Germany.ConclusionThe comparison of arthroplasty registers from England and Wales, Australia, Norway, New Zealand, Germany and Switzerland revealed large differences regarding the application of posterior-stabilized designs, but also common ground considering the overwhelming use of fixed-bearing inserts, which, when inserted correctly, eradicate the potential complication of bearing dislocation. Arthroplasty registers offer a real-world clinical perspective with the aim to improve quality and patient safety.

The Morphology of a Kinematically Aligned Distal Femoral Osteotomy Is Different from That Obtained with Mechanical Alignment and Could Have Implications for the Design of Total Knee Arthroplasty.

Background: Kinematically aligned total knee arthroplasty (KA-TKA) may lead to a different pattern of osteotomy from mechanically aligned total knee arthroplasty (MA-TKA). This paper aims to analyze the effects of KA and MA on the morphology of the distal femoral osteotomy surface. Methods: Computed tomography scans of 80 TKA candidates were reconstructed into 3D models. The measurement of bone morphology was performed after the distal femur cut according to two different alignment techniques. The aspect ratio, trapezoidicity ratio, and asymmetry ratio of the distal femur were assessed. Results: The aspect ratio and the asymmetry ratio in the KA group was significantly lower than that in the MA group in the general population (p < 0.001). The trapezoidicity ratio in the KA group was significantly higher than that in the MA group in the general population (p < 0.001). Conclusions: It was found that KA-TKA and MA-TKA presented different morphologies of the distal femoral osteotomy surface, and this difference was also influenced by gender. The surgery pattern of KA-TKA and MA-TKA and gender should be considered when surgeons choose femoral prostheses.