Mechanical Alignment Technique Research Articles

No Difference in Limb Alignment Between Kinematic and Mechanical Alignment Robotic-Assisted Total Knee Arthroplasty

BackgroundIndividualized alignment techniques have gained major interest in an effort to increase satisfaction among total knee arthroplasty patients. This study aimed to compare postoperative alignment between kinematic alignment (KA) and mechanical alignment (MA) and assess whether KA significantly deviates from the principle of aligning the limb as close to neutral alignment as possible. MethodsThere were 234 patients who underwent robotic-assisted total knee arthroplasty using an unrestricted KA and a strict MA technique (KA: 145, MA: 89). The lateral distal femoral angle, medial proximal tibia angle, and the resultant arithmetic hip-knee-ankle angle (aHKA) were measured. The aHKA < 0 indicated varus alignment, while the aHKA > 0 indicated valgus knee alignment. The primary outcome was the frequency of cases that resulted in an aHKA of ± 4° of neutral (0°), as assessed on full-leg standing radiographs obtained at 6 weeks postoperatively. The secondary outcome was the change in coronal plane alignment of the knee classification type from preoperative to postoperative between the MA and KA groups. ResultsThe mean preoperative aHKA was similar between the 2 groups (P = .19). The KA group had a mean postoperative aHKA of −1.4 ± 2.4°, while the MA group had a mean postoperative aHKA of −0.5 ± 2.1°. No significant difference in limb alignment was identified between KA and MA cases that resulted in hip-knee-ankle angle of ± 4° being neutral (91.7 versus 96.6%, P = .14). There were 97.2% of cases in the KA group that fell within the ± 5° range. The MA group was associated with a significantly higher rate of coronal plane alignment of the knee classification type change from preoperatively to postoperatively (P < .001). ConclusionsKinematic alignment achieved similar postoperative aHKA compared to MA, and thus did not significantly deviate from the principle of aligning the limb as close to neutral alignment as possible. Surgeons should feel comfortable starting to introduce individualized alignment techniques. Without being restricted by boundaries, postoperative alignment will be within 5 degrees of neutral 97% of the time.

Kinematic Alignment Technique Outperforms Mechanical Alignment in Simultaneous Bilateral Total Knee Arthroplasty: A Randomized Controlled Trial

BackgroundThe aim of this study was to compare the clinical results of kinematic alignment (KA) with those of mechanical alignment (MA) in single-stage bilateral total knee arthroplasty. MethodsIn this double-blinded randomized controlled trial, 65 patients who had bilateral knee osteoarthritis underwent simultaneous bilateral total knee arthroplasty. One knee was randomly selected to be operated on with the calipered-KA technique and the other with MA. The participants were assessed via the Oxford Knee Score, Western Ontario and McMaster Universities Osteoarthritis Index questionnaire, and visual analog scale before the surgery and the same plus the Forgotten Joint Score at their last follow-up visit, 2 years postoperatively. Maximum knee flexion and the time reaching maximum knee flexion, named the recovery time, were also recorded. Hip-knee-ankle angle, medial proximal tibial angle, and lateral distal femoral angle were measured before and after the surgery using 3-joint-view radiographs. ResultsAt 2 years, there were significant differences between the KA and MA techniques in terms of duration of surgery, recovery time, and final Western Ontario and McMaster Universities Osteoarthritis Index, Forgotten Joint Score, and maximum flexion range in favor of KA (P < .05), but no significant difference in visual analog scale score or Oxford Knee Score. In patients who have a preferred knee, the KA knee was preferred over the MA knee by most patients. No prosthetic failure or revision was reported in either group. ConclusionsThe KA technique yields acceptable functional outcomes compared to the MA technique. The KA technique was associated with a shorter surgery time, a faster recovery time, and higher patient satisfaction in 2-year follow-ups. Larger multicenter studies with longer follow-ups are warranted to confirm these findings. Level of EvidenceI.

Accurate surgical posterior tibial slope alteration can be achieved in total knee arthroplasty regardless of surgeon skill level or local soft tissue thickness-A retrospective radiograph-based study.

To retrospectively report on the impact of local soft tissue thickness and surgeon skill level on the accuracy of surgical posterior tibial slope (PTS) alteration achieved in patients undergoing total knee arthroplasty (TKA) utilising lateral knee radiographs. Pre- and postoperative radiographs of 82 patients undergoing primary TKA using conventional mechanical alignment technique were measured by two observers and subjected to quality criteria for accurate measurement of the PTS. All patients underwent a standardised surgical approach for PTS alteration: cruciate-retaining (CR) cases with preoperative PTS ≤ 10° were set for reconstruction of the preoperative PTS. Cases indicated for posterior-stabilised (PS) design and/or with a preoperative PTS > 10° were set for 3° of postoperative PTS. Pretibial subcutaneous fat (PSF) and surgeon skill level were analysed for their predictive quality regarding the accuracy of surgical PTS alteration achieved. The overall mean postoperative PTS was significantly lower than the preoperative values (6.2°, SD 2.7 vs. 7.7°, SD 3.2; p = 0.002103). Neither local soft tissue thickness, namely PSF, nor surgeon skill level was found to be a predictor of the accuracy of surgical PTS alteration achieved. Among cases set for PTS reconstruction, 25.9% and 42.6% achieved a postoperative PTS within ±1° and ±2° of preoperative values, respectively. In patients with a PTS > 10° or those indicated for PS design, slope reduction was achieved with a mean postoperative PTS of 6.5°. Furthermore, 14.3% and 32.1% of cases were within ±1° and ±2° of 3, respectively. This study demonstrates that accurate surgical alteration of the PTS is possible in TKA regardless of local knee soft tissue thickness or surgeon skill level. This proves the clinical feasibility of both targeted reduction as well as reconstruction of the PTS in TKA. Level III, retrospective cohort study.

Short-term functional outcomes of robotic-assisted TKA are better with functional alignment compared to adjusted mechanical alignment.

Ligament balancing is essential to the functional outcome of total knee arthroplasty (TKA). The optimal method of alignment remains a controversial issue. The primary objective was to compare the clinical outcomes of TKA between functional and adjusted mechanical alignment techniques. The secondary objectives were to compare bone resection, robotic alignment, and radiological assessment. This was a retrospective case-control series comparing TKA performed with functional alignment (FA) and adjusted mechanical alignment (aMA). Sixty-four FA subjects were matched with 64 aMA controls. These two groups were matched for age, gender, body mass index (BMI), surgeon, and type of frontal deformity. Both surgical procedures were performed using the MAKO® haptic robotic system. Functional scores (Forgotten Joint Score (FJS), Knee Society Score (KSS), and Oxford Knee Score (OKS)) were measured at the final postoperative follow-up. A radiographic evaluation was performed at the same time. Mean FJS were respectively 63.4±25.1 [0-100] and 51.2±31.8 [0-100] in FA versus aMA group (p=0.034). Mean OKS were respectively 40.8±6.3 [21-48] and 34.9±11.8 [3-48] in FA versus aMA group (p=0.027). Mean KSS were respectively 184.9±17.0 [126-200] and 175.6±23.1 [102-200] in FA versus aMA group (p=0.02). The main residual symptom was "none" for 73.0% versus 57.8%, "instability" for 6.4% versus 21.9%, "Pain" for 19.1% versus 12.5%, and "effusion" for 1.6% and 7.8% respectively for FA and aMA group (p=0.016). There were 4 complications in the FA group versus 5 in the aMA group (p>0.999). Mean postoperative hip-knee-ankle (HKA) robotic assessment were respectively 177.3°±2.0 [172-180] and 178.2°±2.0 [173-180] for FA and aMA group (p=0.018). The median difference between HKA robotic and HKA radiological was -3.0° (IQR=3.0; p<0.001). With greater residual deformity and without release, functional alignment showed a statistically significantly better short-term clinical outcome than adjusted mechanical alignment. This difference may not be clinically significant.

Functional alignment in total knee arthroplasty best achieves balanced gaps and minimal bone resections: an analysis comparing mechanical, kinematic and functional alignment strategies.

Key concepts in total knee arthroplasty include restoration of limb alignment and soft-tissue balance. Although differences in balance have been reported amongst mechanical alignment (MA), kinematic alignment (KA) and functional alignment (FA) techniques, it remains unclear whether there are differences in gap imbalance or resection thicknesses when comparing different constitutional alignment subgroups. MA (measured resection technique), KA (matched resections technique) and FA (technique based on the restricted KA boundaries) were compared in 116 consecutive patients undergoing 137 robotic-assisted cruciate-retaining total knee arthroplasties. The primary outcome was the proportion of balanced gaps (differential laxities ≤ 2mm) for extension, flexion, medial and lateral gap measurements. Manual pre-resection laxity measurements were obtained for MA and KA and manual post-resection measurements were obtained for FA in 10° and in 90° of knee flexion. Secondary outcomes were resection depths and implant alignment. All outcomes were analysed per constitutional coronal alignment and joint line obliquity subgroups. The proportions of balance in all four gap measurements were 54.7%, 66.4% and 96.5%, with MA, KA and FA, respectively. Across all constitutional alignment types, FA achieved the highest proportion of balance. MA resected the least amount of bone from the medial tibial plateau. KA had femoral components in most valgus and most internally rotated, tibial components in most varus and was the most bone-preserving for the posteromedial femoral condyle. FA had the most externally rotated femoral components and was most bone-preserving for the distal femoral resections. The study shows that implant alignment to the mechanical axis or joint line anatomy (equal resections) alone does not guarantee a balanced total knee arthroplasty. FA resulted in the highest proportion of balanced knees across all analysed subgroups. Future research will consider whether one alignment philosophy leads to superior outcomes for different constitutional alignment subgroups. Level II.

Programming Deformations of 3D Microstructures: Opportunities Enabled by Magnetic Alignment of Liquid Crystalline Elastomers.

Synthetic structures that undergo controlled movement are crucial building blocks for developing new technologies applicable to robotics, healthcare, and sustainable self-regulated materials. Yet, programming motion is nontrivial, and particularly at the microscale it remains a fundamental challenge. At the macroscale, movement can be controlled by conventional electric, pneumatic, or combustion-based machinery. At the nanoscale, chemistry has taken strides in enabling molecularly fueled movement. Yet in between, at the microscale, top-down fabrication becomes cumbersome and expensive, while bottom-up chemical self-assembly and amplified molecular motion does not reach the necessary sophistication. Hence, new approaches that converge top-down and bottom-up methods and enable motional complexity at the microscale are urgently needed. Synthetic anisotropic materials (e.g., liquid crystalline elastomers, LCEs) with encoded molecular anisotropy that are shaped into arbitrary geometries by top-down fabrication promise new opportunities to implement controlled actuation at the microscale. In such materials, motional complexity is directly linked to the built-in molecular anisotropy that can be "activated" by external stimuli. So far, encoding the desired patterns of molecular directionality has relied mostly on either mechanical or surface alignment techniques, which do not allow the decoupling of molecular and geometric features, severely restricting achievable material shapes and thus limiting attainable actuation patterns, unless complex multimaterial constructs are fabricated. Electromagnetic fields have recently emerged as possible alternatives to provide 3D control over local anisotropy, independent of the geometry of a given 3D object. The combination of magnetic alignment and soft lithography, in particular, provides a powerful platform for the rapid, practical, and facile production of microscale soft actuators with field-defined local anisotropy. Recent work has established the feasibility of this approach with low magnetic field strengths (in the lower mT range) and comparably simple setups used for the fabrication of the microactuators, in which magnetic fields can be engineered through arrangement of permanent magnets. This workflow gives access to microstructures with unusual spatial patterning of molecular alignment and has enabled a multitude of nontrivial deformation types that would not be possible to program by any other means at the micron scale. A range of "activating" stimuli can be used to put these structures in motion, and the type of the trigger plays a key role too: directional and dynamic stimuli (such as light) make it possible to activate the patterned anisotropic material locally and transiently, which enables one to achieve and further program motional complexity and communication in microactuators. In this Account, we will discuss recent advances in magnetic alignment of molecular anisotropy and its use in soft lithography and related fabrication approaches to create LCE microactuators. We will examine how design choices-from the molecular to the fabrication and the operational levels-control and define the achievable LCE deformations. We then address the role of stimuli in realizing the motional complexity and how one can engineer feedback within and communication between microactuator arrays fabricated by soft lithography. Overall, we outline emerging strategies that make possible a completely new approach to designing for desired sets of motions of active, microscale objects.

Transition to Robotic Total Knee Arthroplasty With Kinematic Alignment is Associated With a Short Learning Curve and Similar Acute-Period Functional Recoveries.

Background Robotic instruments are increasingly being used in total knee arthroplasty (TKA). The adoption of robotics has allowed surgeons a new level of precision and facilitated the adoption of a kinematic approach in TKA. We sought to examine one surgeon's transition from a traditional mechanical alignment technique to a modified kinematic approach by comparingshort-term recovery outcomes of robotic TKA patients with those who underwent traditionally instrumented TKAs. Methodology We examined six-week and six-month postoperative data from 99 traditionally instrumented, mechanically aligned and 66 kinematically aligned robotic TKA patients between January 2021-October 2021 and October 2021-April 2022, respectively. Robotic surgery was performed with VELYS™ (DePuy Synthes, Warsaw, IN, USA) a semi-active, imageless, table-affixed, robotic TKA solution. Results Robotic and traditionally instrumented TKAs did not differ significantly in any functional outcome measures examined, including pain scores, use of assistive devices, or range of motion at six weeks postoperatively. Robotic TKA patients had a better range of motion in knee flexion than traditional TKA patients at six months postoperatively. There were no differences in surgical complications or rates of manipulation under anesthesia within one year postoperatively. Robotic surgery tourniquet times exhibited a steep drop off and equaled traditional methods after only two robotic surgeries were performed. Conclusions Transition to a kinematic, semi-active, robotic TKA demonstrated encouraging results by demonstrating acute-period recovery of function consistent with the current standard of care, as well as a better range of motion at six months postoperatively. The learning curve of this new-to-market device was shorter than previous research on the transition to robotic TKA. Clear advantages of transitioning to robotic instrumentation by any specific functional measure are yet to be elucidated. Further randomized trials are necessary to characterize long-term outcomes.

The Effect of Minor Adjustments to Tibial and Femoral Component Position on Soft Tissue Balance in Robotic Total Knee Arthroplasty

BackgroundIdeal goals for alignment and balance in total knee arthroplasty (TKA) remain controversial. We aimed to compare initial alignment and balance using mechanical alignment (MA) and kinematic alignment (KA) techniques and to analyze the percentage of knees that could achieve balance using limited adjustments to component position. MethodsProspective data on 331 primary robotic TKAs (115 MAs and 216 KAs) were analyzed. Medial and lateral virtual gaps were recorded in both flexion and extension. A computer algorithm was used to calculate potential (theoretical) implant alignment solutions to achieve balance within 1 millimeter (mm) without soft tissue release given an alignment philosophy (MA or KA), angular boundaries (±1, ±2, or ±3°), and gap targets (equal gaps or lateral laxity allowed). The percentage of knees that could theoretically achieve balance was compared. ResultsLess than 5% of TKAs were initially balanced. Limited adjustments to component position increased the percentage of TKAs that could be balanced in a graduated manner, with no difference between MA and KA start points: adjustments of ±1 (10% versus 6%, P = .17), ±2 (42% versus 39%, P = .61), or of ±3 (54% versus 51%, P = .66). A higher percentage of TKAs could be balanced when a greater range for lateral gap laxity was allowed. Balancing from KA resulted in increased joint line obliquity in the final implant alignment. ConclusionA high percentage of TKAs can be balanced without soft tissue release using minor adjustments to component position. Surgeons should consider the relationship between alignment and balance goals when optimizing component positioning in TKA.

Mid-Term Outcomes of Navigation-Assisted Primary Total Knee Arthroplasty Using Adjusted Mechanical Alignment.

The adjusted mechanical alignment (aMA) technique is an extension of conventional mechanical alignment (MA), which has rarely been reported. The purpose of this study was to evaluate mid-term outcomes of navigation-assisted total knee arthroplasty (TKA) using aMA. This retrospective cohort study enrolled 63 consecutive patients (77 knees) who underwent navigation-assisted TKA using aMA between September 2017 and October 2019. Fifty-two consecutive patients (61 knees) who underwent TKA using MA during the same period were assessed as the controlled group. The demographic data and perioperative data were recorded. The parameters of resection and soft tissue balance including tibia resection angle, frontal femoral angle, axial femoral angle, joint line translation, medial and lateral gap in extension and flexion position were recorded. Radiographic parameters and functional scores including the Hospital for Special Surgery (HSS) score, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score, and Forgotten Joint Score-12 (FJS-12) were evaluated. Surgery-related complications were recorded. The average follow-up was 3.5 years, with a minimum of 2.4 years. The frontal femoral angle was 2.55° ± 1.08° in aMA group versus 0.26° ± 0.60° in MA group (p < 0.001). The axial femoral angle was 3.07° ± 2.23° external in aMA group versus 2.30° ± 1.70° in MA group (p=0.027). The lateral flexion gap was wider in the aMA group, with a mean of 0.71 mm more laxity (p=0.001). Postoperative coronal alignment was 177.03° ± 1.82° in aMA group versus 178.14° ± 1.69° in MA group (p < 0.001). The coronal femoral component angle was 92.62° ± 2.78° in aMA group versus 90.85° ± 2.01° in MA group (p < 0.001). Both aMA-TKA and MA-TKA achieved satisfactory mid-term clinical outcomes. However, the HSS scores at 1 month postoperatively were significantly higher using aMA than using MA (p < 0.001). Navigation-assisted TKA using aMA technique obtained satisfactory mid-term clinical outcomes. The aMA technique aims to produce a biomimetic wider lateral flexion-extension gap and minimize releases of soft tissues, which might be associated with better early clinical outcomes than MA technique.

Progress in optical adhesive and lamination process of touch screen in 3C products

AbstractCompared with the traditional keyboard and mouse input method, touch screen technique has high convenience for users. With the development of technology, touch screen is widely application in various electronic products because of their high transmittance, clear images, and convenient operation. This review mainly introduces the optical clear adhesive (OCA), liquid optical clear adhesive (LOCA), and the most commonly used LOCA ultra violet (UV)‐curable adhesives. Preparation and performance of UV‐curable adhesives are deeply explored. The structure of touch screen, such as one glass solution (OGS), on‐cell and in‐cell is discussed. Moreover, lamination process includes full lamination and non‐full lamination is also discussed. This review introduces the alignment technique comprise mechanical alignment technique and non‐mechanical alignment technique (such as machine vision) and laminating equipment. The recent development and existing problems with the touch screen lamination process are discussed. Furthermore, this review describes the latest developments in the adhesive of touch screen lamination process and predicts possible future development trends, which could provide references for subsequent research work.

A prospective randomised controlled trial of mechanical axis with soft tissue release balancing vs functional alignment with bony resection balancing in total knee replacement—a study using Stryker Mako robotic arm-assisted technology

BackgroundImproving the functional outcome following total knee arthroplasty (TKA) by using different alignment techniques remains controversial. The surgical techniques and technologies used so far to obtain these alignments have all suffered from inaccuracies. The use of robotic technology to plan and execute the bony resection provides increased accuracy for these various alignment techniques and may determine which will deliver superior function. Functional alignment (FA) is a newer surgical technique that aims to position the prosthesis with respect to each patients’ specific bony anatomy whilst minimising disruption to the soft tissue envelope. This trial aims to compare the patient and surgical outcomes of FA to the current gold standard surgical technique, mechanical alignment (MA), under randomised and blinded conditions.MethodsPatients with symptomatic knee osteoarthritis will be prospectively recruited. Following informed consent, 240 patients will be randomised to either a MA surgical technique (the control group) or a FA surgical technique (the intervention group) at a ratio of 4:1 using a random number generator. All patients will undergo computer tomography (CT) based robotic arm-assisted surgery to execute planned implant positioning and alignment with high levels of accuracy. The primary outcome is the forgotten joint score (FJS) at 2 years post-operation. Secondary outcome measures include patient reported outcome measures of post-operative rehabilitation, pain, function and satisfaction, as well as limb alignment, implant revisions and adverse events. Intention-to-treat and per-protocol population analysis will also be conducted. Standardisation of the surgical system and care pathways will minimise variation and assist in both patient and physiotherapist blinding. Ethical approval was obtained from the Northern B Health and Disability Ethics Committee (20/NTB/10).DiscussionCurrently, MA remains the gold standard in knee replacement due to proven outcomes and excellent long-term survivorship. There are many alternative alignment techniques in the literature, all with the goal of improving patient outcomes. This study is unique in that it leverages an advanced analytics tool to assist the surgeon in achieving balance. Both alignment techniques will be executed with high precision using the CT-based robotic arm-assisted surgery system which will minimise surgical variation. This trial design will help determine if FA delivers superior outcomes for patients.Trial registrationAustralia and New Zealand Clinical Trials Registry (ANZCTR), ACTRN12620000009910. Registered on 9 January 2020. ClinicalTrials.gov, NCT04600583. Registered on 29 September 2020.

Varus morphology and its surgical implication in osteoarthritic knee and total knee arthroplasty

BackgroundKnee varus alignment represents a notorious cause of knee osteoarthritis. It can be caused by tibial deformity, combined tibial–femoral deformity and/or ligament imbalance. Understanding malalignment is crucial in total knee arthroplasty to restore frontal plane neutral mechanical axis. The aim of this study was to determine which factor contributes the most to varus osteoarthritic knee and its related surgical implications in performing a total knee arthroplasty.MethodsWe retrospectively evaluated 140 patients operated for total knee arthroplasty due to a varus knee. Full-leg hip to ankle preoperative X-rays were taken. Radiological parameters recorded were: mechanical axis deviation, hip–knee–ankle, anatomical–mechanical angle, medial neck shaft angle, mechanical lateral distal femoral angle (mLDFA), medial proximal tibial angle (MPTA), joint line convergence angle (JLCA), lateral proximal femoral angle, lateral distal tibial angle (LDTA), femoral bowing, and length of tibia and femur. We also determined ideals tibial and femoral cuts in mm according to mechanical alignment technique. A R2 was calculated based on the linear regression between the predicted values and the observed data.ResultsThe greatest contributor to arthritic varus (R = 0.444) was MPTA. Minor contributors were mLDFA (R = 0.076), JLCA (R = 0.1554), LDTA (R = 0.065), and femoral bowing (R = 0.049). We recorded an average of 7.6 mm in lateral tibial cut thickness to restore neutral alignment.ConclusionsThe radiological major contributor to osteoarthritic varus knee alignment is related to proximal tibia deformity. As a surgical consequence, during performing total knee arthroplasty, the majority of the correction should therefore be made on tibial cut.

An anatomo-functional implant positioning technique with robotic assistance for primary TKA allows the restoration of the native knee alignment and a natural functional ligament pattern, with a faster recovery at 6months compared to an adjusted mechanical technique.

An anatomo-functional implant positioning (AFIP) technique in total knee arthroplasty (TKA) could restore physiological ligament balance (symmetric gap in extension, asymmetric gap in flexion). The purposes were to compare (1) ligament balancing in extension and flexion after TKA in the AFIP group, (2) TKA alignment, implant positioning and patellar tracking between AFIP and adjusted mechanical alignment (aMA) techniques, (3) clinical outcomes between both groups at 12months. All robotic-assisted TKA with an AFIP technique were included (n = 40). Exclusion criteria were genu valgum (HKA angle > 183°), extra-articular deformity more than 10°, and patellar maltracking (high-grade J-sign). One control patient with a TKA implanted by an aMA technique was matched for each case, based on age, body mass index, sex, and knee alignment. Ligament balancing (medial and lateral gaps in millimeters) in full extension and at 90° of flexion after TKA in the AFIP group was assessed with the robotic system. TKA alignment (HKA angle), implants positioning (femoral and tibial coronal axis, tibial slope, joint-line orientation), patellar tracking (patellar tilt and translation) and the Knee Society Score (KSS) at 6 and 12months were compared between both groups. The ligament balancing was compared using a t test for paired samples in the AFIP group. The radiographic measurements and KSS scores were compared between groups using a t test for independent samples. In the AFIP group, there was no significant difference between the medial and lateral gap laxity in extension (NS). A significant opening of the lateral gap was observed in flexion compared to extension (mean: + 2.9mm; p < 0.0001). The mean postoperative HKA angle was comparable between both groups (177.3° ± 2.1 in the AFIP group vs 176.8° ± 3.2; NS). In the AFIP group, the femoral anatomy was restored (90.9° ± 1.6) and the tibial varus was partially corrected (87.4° ± 1.8). The improvement of Knee and Function KSS at 6months was better in the AFIP group (59.3 ± 11.9 and 51.7 ± 20, respectively, versus 49.3 ± 9.7 and 20.8 ± 13; p < 0.001). The AFIP concept allowed the restoration of the native knee alignment and a natural functional ligament pattern. With a more physiological target for ligament balancing, the AFIP technique had equivalent clinical outcomes at 12months compared to aMA, with a faster recovery. III retrospective therapeutic case control series.

Head-to-Head Comparison of Kinematic Alignment Versus Mechanical Alignment for Total Knee Arthroplasty

BackgroundSeeing as there are many alignment strategies for total knee arthroplasty (TKA), we need to determine differences between them in a rigorous scientific way. Therefore, we sought to compare perioperative and postoperative functional outcomes in patients undergoing TKA for varus osteoarthritis with a mechanical alignment target vs a kinematic alignment target, both executed with the same implant and same technological guidance. MethodsOne hundred consecutive patients who underwent TKA using a mechanical alignment technique were 1:1 matched to 100 patients who underwent TKA using a kinematic alignment (KA) technique, using the same implant and robotic technology. Patient-reported outcomes were measured postoperatively at 1 and 2 years. Power analysis revealed 94 patients to detect a significant difference. ResultsMean Visual Analog Scale scores were higher in the mechanical alignment group during the first 6 weeks (P = .04), but statistically similar at 1 year. Six-week Veterans RAND 12 Item Health Survey mental and physical components were statistically similar (P = .1). Patients did not differ in 6-week or 1-year knee range of motion (P > .43). Knee Injury and Osteoarthritis Outcome Score Joint Replacement was significantly better in the KA group at 6 weeks, 1 year, and 2 years (P = .09). Forgotten Joint Score at 1 and 2 years postoperatively were significantly higher in the KA group (P < .001). ConclusionPatients undergoing TKA with KA experienced less pain in 6 weeks after surgery, and higher Forgotten Joint Scores at 1 and 2 years postoperatively. Alternative TKA alignment and balancing strategies should be considered to increase patient satisfaction.

Biomechanical Comparison of Kinematic and Mechanical Knee Alignment Techniques in a Computer Simulation Medial Pivot Total Knee Arthroplasty Model.

Several concepts may be used to restore normal knee kinematics after total knee arthroplasty. One is a kinematically aligned (KA) technique, which restores the native joint line and limb alignment, and the other is the use of a medial pivot knee (MPK) design, with a ball and socket joint in the medial compartment. This study aimed to compare motions, contact forces, and contact stress between mechanically aligned (MA) and KA (medial tilt 3° [KA3] and 5° [KA5]) models in MPK. An MPK design was virtually implanted with MA, KA3, and KA5 in a validated musculoskeletal computer model of a healthy knee, and the simulation of motion and contact forces was implemented. Anteroposterior (AP) positions, mediolateral positions, external rotation angles of the femoral component relative to the tibial insert, and tibiofemoral contact forces were evaluated at different knee flexion angles. Contact stresses on the tibial insert were calculated using finite element analysis. The AP position at the medial compartment was consistent for all models. From 0° to 120°, the femoral component in KA models showed larger posterior movement at the lateral compartment (0.3, 6.8, and 17.7 mm in MA, KA3, and KA5 models, respectively) and larger external rotation (4.2°, 12.0°, and 16.8° in the MA, KA3, and KA5 models, respectively) relative to the tibial component. Concerning the mediolateral position of the femoral component, the KA5 model was positioned more medially. The contact forces at the lateral compartment of all models were larger than those at the medial compartment at >60° of knee flexion. The peak contact stresses on the tibiofemoral joint at 90° and 120° of knee flexion were higher in the KA models. However, the peak contact stresses of the KA models at every flexion angle were <20 MPa. The KA technique in MPK can successfully achieve near-normal knee kinematics; however, there may be a concern for higher contact stresses on the tibial insert.

Individualized Functional Knee Alignment in Total Knee Arthroplasty: A Robotic-assisted Technique

Introduction: The use of robotic technology is becoming a well-recognized alternative to conventional total knee arthroplasty (TKA). The quantitative soft tissue information generated in robotic surgery can be used to balance the knee and achieve functional alignment (FA) of the components. This paper describes a novel FA technique using an individualized preoperative plan that is then adjusted to achieve soft tissue balance. Materials and Methods: We report on surgical technique, indications, considerations, and complications after our experience of performing 650 functionally aligned TKAs. We collected 2-year patient reported outcomes on 165 TKAs in this series (165 of 193 TKAs have reached 2 years follow-up in the series of 650 TKAs; 85% follow-up rate). Results: We found significant postoperative improvements with few infections and no revisions for mechanical reasons 2 years after surgery with this technique. Patients had improved knee range-of-motion (105 degrees° flexion preoperatively vs. 125 degrees flexion postoperatively; P&lt;0.001), higher Forgotten Joint Scores (17 preoperatively vs. 77 postoperatively; P&lt;0.001), improved Oxford Knee Scores (22 preoperatively vs. 43 postoperatively; P&lt;0.001), higher KOOS Jr scores (48 preoperatively vs. 88 postoperatively; P&lt;0.001) and lower visual analogue score pain scores (70 preoperatively vs. 12 postoperatively; P&lt;0.001) 2 years postoperatively. Discussion: The described surgical technique is a promising method for conducting a robotic TKA. Benefits of FA include improved efficiency with preresection balancing, reduced soft tissue releases compared with a mechanical alignment technique, and accurate bony cuts with robotic assistance. Further studies are required to compare this technique with established methods to determine any differences in outcomes.

Seven phenotypes of varus osteoarthritic knees can be identified in the coronal plane.

Recommendations for resecting distal femur and proximal tibia in mechanical and anatomical alignment techniques are standardized. Kinematic alignment propagates individualizing resection planes. Whether significant variation exists, to warrant departure from standardized resection planes, has not been shown thus far in a large cohort of knees and with a wide range of varus deformity. The null hypothesis of this study was that there was no phenotypic variation in varus osteoarthritic knees. The aim of this paper was to determine whether distinct phenotypes could be identified, based on variations in coronal femoral and tibial morphology, which could aid in surgical planning and categorizing varus knees for future studies. 2129 full-leg weightbearing radiographs were analyzed (1704 preoperative; 425 of contralateral arthritic knee). Measurements made were of HKA (hip-knee-ankle angle), VCA (valgus correction angle), mLDFA (lateral mechanical distal femoral angle), aLDFA (lateral anatomical distal femoral angle), MPTA (medial proximal tibial angle), MNSA (medial neck shaft angle), TAMA (angle between tibial mechanical and anatomical axes), and TPDR (percentage length of tibia proximal to extra-articular deformity). Seven distinct types were identified covering 2021 knees, reducible to 4 broad phenotypes: 11% were Type 1 'Neutral' knees showing values close to reported normal knees (mean VCA 5.5°, mLDFA 87°, aLDFA 81°). 38% were Type 2 'Intra-articular varus' with medial intra-articular bone loss (mean mLDFA 90.9°, MPTA 85.4°, VCA of 5.7°). 41% were Type 3 'Extra-articular varus' with extra-articular deformity (EAD). Type 3a had proximal tibial EAD; Type 3b had tibial diaphyseal EAD; Type 3c had femoral EAD (mean VCA 8.7°, HKA 166°), and severe medial bone loss (mean mLDFA 92°, MPTA 83°). 9% were Type 4 'Valgoid type' with features of valgus knees: Type 4a had medial femoral bowing (mean VCA 2.9°); Type 4b had significant distal femoral valgus (mean mLDFA 85.3°, aLDFA 78.6°). The null hypothesis that there was no phenotypic variation in varus osteoarthritic knees was rejected as considerable variation was found in coronal morphology of femur and tibia. Four broad phenotypic groups could be identified. Plane of the knee joint articular surface was quite variable. This has relevance to planning and performance of corrective osteotomies, unicompartmental and total knee arthroplasty. III, retrospective cohort study.

Amine-Acrylate Liquid Single Crystal Elastomers Reinforced by Hydrogen Bonding.

Liquid crystalline elastomers (LCEs) have been considered one of the most promising material concepts for artificial muscles. However, accomplishing actuation of LCEs requires macroscopic alignment of the liquid-crystalline orientation in the rubbery network, which imposes challenges in the materials chemistry and processing. A two-stage curing strategy has been the dominating approach during last three decades. Despite its many successes, the method is difficult in practice and requires delicate experiential skills, dealing with intrinsic fragility of intermediate gels after the first crosslinking stage. Here, a robust fabrication method for monodomain LCE based on the amine-acrylate aza-Michael addition is developed, involving two readily commercially available components with no catalyst. The method is based on the large kinetic difference of hydrogen addition in primary amines to acrylates, which offers a sufficient gap separating two stages of curing and enabling versatile mechanical alignment techniques for manufacturing monodomain LCE in both liquid and gel states. Importantly, the mechanically robust network, helping processability at a partial-crosslinking stage, is facilitated by the chemically generated hydrogen bonding all through the process, as a by-product of hydrogen addition. Such a facile two-component kit-like fabrication should aid researchers from various fields in the search for a practical and reliable process of making soft actuators.

Kinematic alignment of medial UKA is safe: a systematic review

Owing to the improved understanding of knee kinematics and the successful introduction of the kinematic alignment (KA) technique for implanting total knee arthroplasty (TKA), it was recently understood that the “Cartier angle technique” corresponds to a kinematic implantation of the uni-compartmental knee arthroplasty (UKA) components. When compared to the universally spread mechanical alignment (MA) technique for implanting UKA, the KA method generates a more anatomic prosthetic knee that may be clinically advantageous. The aims of this study are to determine if KA UKAs are associated with acceptable functional performance and patient satisfaction (question 1), rates of residual pain and tibia plateau fracture (question 2), and rates of reoperation and revision (question 3), and to define the component orientation and limb alignment as measured on radiograph (question 4), and the stress shielding related bone loss in the proximal tibia (question 5) with KA UKA, and where possible to compare with MA UKA. KA UKA generates good clinical outcomes, similar or superior to the ones of MA UKA. Systematic review of literature databases were primarily searched using Healthcare Databases Advanced Search (HDAS). Two primary searches were conducted using the electronic databases MEDLINE, EMBASE, and PubMed, and a secondary search was conducted using review articles and bibliography of obtained papers in order to ascertain more material. Nine eligible non-comparative prospective (3) or retrospective (6) cohort studies, which cumulated 593 KA UKAs with follow-up between 3.2 and 12 years, fulfilled the inclusion criteria for this systematic review. The findings demonstrated high Knee Society Score (KSS) (from 87 to 95) and function scores (from 81 to above 91) in addition to patient satisfaction scores of 88%. There was no revision for tibia plateau fracture, 0.8% (5 cases) for unexplained pain tibia, 2.0% (12 cases) for component loosening, and 5.6% (33 cases) for any causes of aseptic failures reported for KA UKA. The prosthetic lower limb and tibia implant alignments were both found to be in slight varus (means between 3 and 5°), and the postoperative joint line and tibia component was shown to be parallel to the floor when standing. The KA UKA components migration, as measured on radiostereometry, was acceptable. The KA technique is an alternative, personalised, more physiological method for implanting UKA, which could be clinically advantageous when compared to the MA technique. The literature supports the good mid- to long-term clinical safety and good efficacy of KA UKA; however, comparison between KA and MA techniques for UKA was not performed due to limited literature. Further investigations are needed to better define the clinical impact of KA UKA, and the acceptable limits for KA of the UKA tibial component. Level 4; systematic review of level 4 studies.

Arthroplasty of the Knee: Current Techniques for Implant Alignment.

When a total knee arthroplasty (TKA) is implanted using the traditional mechanical alignment technique, this typically results in a straight leg, independently of pre-operative or even pre-arthrotic varus or valgus alignment. With mechanical alignment, we distinguish between 2 different alignment techniques: ligament balancing and bony referencing according to bony skeletal landmarks. In ligament balanced technique beside the straight mechanical axis, the prosthesis is implanted at 90° to the latter. The rotational alignment of the femur is set according to the ligament tension. In the skeletal referenced technique, the rotation of the femur is also set according to bony skeletal landmarks. As a variation of this technique, the prosthesis can be implanted with anatomical alignment. In this technique, the medial slope of the joint line of 3° in the frontal plane is respected during the implantation of TKA. Both techniques result in comparable long-term results with survival rates of almost 80% after 25 years. On the other hand, 15 – 20% of TKA patients report dissatisfaction with their clinical result. For more than 10 years now, the kinematic TKA alignment concept has been developed with the goal to achieve implantation that is adapted to the individual anatomy of the patient. The advocates of this technique expect better function of TKA. This strategy aims to reconstruct the pre-arthrotic anatomy of a given patient while preserving the existing joint line and the mechanical axis without performing ligamentary release. Studies have shown that the function of the prothesis is at least that good as in the conventional techniques. Long-term results are still sparse, but initial studies show that TKA implanted using the kinematic alignment technique exhibit comparable 10-year-survival rates to those implanted using the traditional mechanical alignment technique. Future studies need to show the limitations of this new technique and to identify patients who will or will not significantly benefit from this technique.