Balance In Total Knee Arthroplasty Research Articles

Medial soft tissue release is also related to the anterior stability of cruciate-retaining total knee arthroplasty: a cadaveric study.

Medial soft tissue release is occasionally performed to achieve mediolateral ligament balance in total knee arthroplasty (TKA), whose sequential effect on mediolateral and anteroposterior stability remains unclear. This study aimed to quantitatively evaluate the difference in mediolateral and anteroposterior stability according to a sequential medial soft tissue release in TKA. Cruciate-retaining TKA was performed in six cadaveric knees. Medial and lateral joint gaps, varus-valgus angle, and tibial anterior and posterior translations relative to the femur with pulling and pushing forces, respectively, were measured. All measurements were performed at full extension and 45° and 90° flexion after release of the deep medial collateral ligament (MCL) (stage 1), the posteromedial capsule (stage 2), and the superficial MCL (stage 3). Mediolateral and anteroposterior stability were compared between stages, and correlations between mediolateral and anteroposterior stability were analyzed. Medial joint gap significantly increased from stages 1 to 3 by 3.2mm, 6.8mm, and 7.2mm at extension, 45° flexion, and 90° flexion, respectively, and from stages 2 to 3 by 3.5mm at extension. Varus-valgus angle was varus at stage 2, which turned to valgus at stage 3 (-2.7° to 0.8°, -2.2° to 4.3°, and -5.5° to 2.5° at extension, 45° flexion, and 90° flexion, respectively). Anterior translation at 90° flexion significantly increased from stages 1 and 2 to stage 3 by 11.5mm and 8.2mm, respectively, which was significantly correlated with medial gap (r = 0.681) and varus-valgus angle (r = 0.495). Medial soft tissue release also increased tibial anterior translation as well as medial joint gap, and medial joint gap and tibial anterior translation were significantly correlated. Surgeons should be careful not to create too large medial joint gap and tibial anterior translation in flexion by excessive medial release up to the superficial MCL for achieving an equal mediolateral joint gap in extension.

Soft tissue elasticity in total knee arthroplasty: An in vivo quantitative analysis

BackgroundSoft tissue balance is essential for total knee arthroplasty success. The elastic properties of soft tissues affect knee-joint stability and flexibility. This study proposed a novel methodology for in vivo quantitative analysis of soft tissue elasticity during total knee arthroplasty. In this study, we aimed to (1) establish a mathematical model to depict medial and lateral soft tissue elasticity, (2) report the individual differences and interindividual commonalities in soft tissue elasticity. MethodsA specifically designed knee tensor was used to evaluate soft tissue elasticity by dynamically applying sequential tensions to medial and lateral compartments while measuring knee joint gaps in both compartments. Measurements were performed on ten knees of six cadavers. Bivariate polynomial regression was used for analysis, and the equivalent elastic coefficient (N/mm) was calculated. FindingsSoft-tissue elasticity showed high individual differences. The equivalent elastic coefficient was larger in the medial compartment than in the lateral compartment, and the equivalent elastic coefficient of the lateral compartment gradually decreased while the medial equivalent elastic coefficient remained constant when the knee was flexed. The lateral gaps increased from 0.1 to 3.9 mm, and the medial gaps increased from 0 to 1.5 mm when the tension increased from 60 to 90 N. The shapes and distributions of the silkworm-like lattices in elasticity and balance evaluations are clinically relevant to knee balance. InterpretationSoft-tissue balance in total knee arthroplasty is significantly affected by soft-tissue elasticity. An intraoperative quantitative analysis of elasticity helps to tail an individualized balancing target for total knee arthroplasty.

Mid-Flexion Instability in Total Knee Arthroplasty: Insights from Robotic-Assisted Surgery

Despite technological advancements with robotic-assisted surgery, instability remains a challenge in total knee arthroplasty (TKA). Mid-flexion instability (MFI) has been reported to cause patient dissatisfaction. With no universal diagnostic criteria, the MFI concept is still ambiguous, and no specific treatment algorithm is defined. This study aims to analyze the MFI concept and risk factors and investigate how robotic surgery, compared to manual TKA, could impact the MFI concept. A comprehensive investigation of the current literature regarding MIF, focusing especially on its relationship with robotic surgery TKA, was conducted using the PubMed and Scopus databases. The MIF concept remains poorly understood, so it is crucial to prevent it by recognizing risk factors, which are technique-related, implant-related, and patient-related. Since robotics offers optimal balancing in TKA and reduces causes affecting MFI, it could indirectly impact and prevent this complication. This review suggests that robotics utilization improving TKA balancing has the potential to impact and reduce MFI. However, further research in this area is essential to provide insight regarding the role of robotics in mitigating the MFI risk.

Kinematic Alignment Achieves a More Balanced Total Knee Arthroplasty Than Mechanical Alignment among CPAK Type I Patients: A Simulation Study

Background: There is no consensus on whether mechanical alignment (MA) or kinematic alignment (KA) should be chosen for total knee arthroplasty (TKA) for coronal plane alignment of the knee (CPAK) Type I with a varus arithmetic HKA (aHKA) and apex distal joint line obliquity (JLO). The aim of this study was to investigate whether MA or KA is preferable for soft tissue balancing in TKA for this phenotype. Method: This prospective cohort study included 64 knees with CPAK Type I osteoarthritis that had undergone cruciate-retaining TKA. Using optical tracking software, we simulated implant placement in the Mako system before making the actual bone cut and compared the results between MA and KA. Extension balance (the difference between medial and lateral gaps in extension) and medial balance (the difference in medial gaps in flexion and extension) were examined. These gap differences within 2 mm were defined as good balance. Achievement of overall balance was defined as an attainment of good extension and medial balance. The incidence of balance in each patient was compared with an independent sample ratio test. Results: Compared with the MA group, the KA group achieved better soft tissue balance in extension balance (p < 0.001). A total of 75% of the patients in the KA group achieved overall balance, which was greater than the 38% achieved in the MA group (p < 0.001). Conclusions: In robot-assisted TKA for CPAK Type I osteoarthritis, KA achieved knee balance during extension without soft tissue release in a greater percentage of patients than MA.

Spacer rotation technique allows precise evaluation of gap balance in total knee arthroplasty.

The symmetry of the flexion and extension gap influences the functional and long-term outcome after total knee arthroplasty (TKA). Most surgeons check it by applying varus and valgus stress using spacers. This technique has limited accuracy and could be easily extended by rotational movement of the spacer. The objective was to determine the detection threshold and interobserver reliability of this technique. In an in vitro setting with a human cadaveric knee, gap asymmetries were simulated by different medially and laterally applied forces. Using an optical measurement system, the pivot point of the spacer was calculated as a function of the gap symmetry in the first part of the experiment. In the second part, the detection threshold and interobserver reliability of 4 surgeons were determined. For this purpose, gap asymmetries were adjusted to between 0 and 120N in a blinded trial. With a symmetrical gap, the centre of rotation of the spacer was located in the centre of the tibia. With increasing gap asymmetry, the centre of rotation of the spacer shifted to the tight side. This shift was approximately linearly dependent on the force difference. A perfectly balanced gap was detected by the examiners in 50% of the cases. From a force difference of 40N, all examiners identified the gap asymmetry in all cases (ICC = 1.0). The method of spacer rotation described is suitable for reliably detecting gap differences at ≥ 40N, independently of the examiner.

Functional alignment in robotic-assisted total knee arthroplasty: a systematic review.

The present study systematically reviewed current evidence on functional alignment (FA) in robotic total knee arthroplasty (TKA), discussing advantages and limitations, possible pitfalls, and prospects. This study was conducted according to the 2020 PRISMA statement. In August 2023, the following databases were accessed: PubMed, Web of Science, Google Scholar, and Embase with no additional filters or time constraints. All the clinical studies investigating functional alignment in robotic TKA were accessed. Only studies published in peer-reviewed journals were considered. The risk of bias was evaluated following the guidelines in the Cochrane Handbook for Systematic Reviews of Interventions. Non-randomized controlled trials (non-RCTs) were evaluated using the Risk of Bias in Nonrandomised Studies of Interventions (NRSI) (ROBINS-I) tool. Data from 1198 patients (seven studies) were retrieved. The mean length of the follow-up was 17.1 ± 6.4months. The mean age was 67.2 ± 5.4years, and the mean BMI was 30.9 ± 2.7kg/m2. FA might improve resection accuracy, implant alignment, and gap balancing in TKA, and additional high-quality clinical trials are necessary to properly establish the superiority of FA to other alignment techniques in TKA. Long-term clinical trials are needed to investigate the impact of FA on implant survivorship. Level IV, systematic review and meta-analysis.

Rotational position of ligament balancer affects medial and lateral soft tissue balance in total knee arthroplasty

PurposeThe purpose of this study was to clarify the effect on medial and lateral soft tissue balance for different rotational positions of the balancer. MethodsA total of 65 patients who were operated using a rotational mobile bearing total knee arthroplasty (TKA) have been evaluated. A new balancer was made so that the insert trial could be rotated on the paddle. We measured the angle of deviation to varus or valgus and the rotational angle of the insert trial at Akagi's line (group 0), at 20° of internal rotation from the Akagi's line (group IR), and at 20° of external rotation from the Akagi's line (group ER). ResultsThe IR group had a significantly medial tightness than the other two groups. The ER group had a significantly lateral tightness than the other two groups. All cases were divided into three groups by the position of the insert (neutral, internal rotation and external rotation) on the balancer with respect to Akagi's line after range of motion (ROM) technique. In extension, a significant negative correlation was found between mean varus/valgus balance and rotation of the insert. ConclusionIn mobile bearing TKA, it is possible to obtain the optimal medial and lateral soft tissue balance if the misalignment is within the possible range of rotation allowed by the design of the insert. Anatomical landmarks should also be referenced when determining tibial rotational alignment using the ROM technique, as it was easily influenced by medial and lateral soft tissue balance.

Using sequential bone cutting to titrate soft tissue balance in total knee arthroplasty effectively minimizes soft tissue release

BackgroundAchieving soft tissue balance while maintaining limb alignment within acceptable boundaries is crucial for successful total knee arthroplasty (TKA). We proposed a sequential bone cutting (SBC) technique to titrate the soft tissue balance in robot-assisted TKA to achieve the desired balance with minimum soft tissue release.MethodsIn total, 106 robot-assisted TKAs using the SBC technique were included. The preoperative hip-knee-ankle angle (HKA) was < 10° in 76 and ≥ 10° in 30 knees. The gaps were initially balanced with the help of the pre-resection balancing provided by the robotic system. Soft tissue balance and alignment were quantitatively measured after the initial bone cutting and final bone cutting. Additional adjustments (bone recuts and soft tissue releases) required to address soft tissue imbalance after initial bone cutting were recorded. The frequencies of soft tissue releases, soft tissue balance, and resultant alignment ≤ 3° were compared between non-severe (HKA < 10°) and severe deformity (HKA ≥ 10°) groups.ResultsSoft tissue balance was achieved in 45 knees (42.5%) after initial bone cutting and in 93 knees (87.7%) after final balancing. The postoperative alignment was within 3° from neutral in 87 knees (82.1%) and 3–5° in 17 knees (16.0%). For unbalanced knees (n = 61) after initial bone cutting, soft tissue release was avoided by SBC in 37 knees (60.7%) and was deemed necessary in 24 knees (39.3%). Soft tissue release was more likely to be avoided in the non-severe deformity cohort (86.8% [33 of 38]) than in the severe deformity cohort (17.4% [4 of 23]; p < 0.001). The non-severe deformity cohort showed a significantly higher rate of resultant alignment ≤ 3° from neutral than the severe deformity cohort (90.8% vs. 60.0%; p < 0.001).ConclusionPre-resection balancing is inappropriate to ensure soft tissue balance. The SBC technique is effective in minimizing soft tissue release while maintaining overall alignment within acceptable boundaries.

Achieving Correct Balance in Total Knee Arthroplasty with Fixed Varus Deformity.

Varus knee deformity is one of the most common deformities presenting for total knee arthroplasty (TKA). When present, a varus knee deformity contributes to overload of the medial joint compartment during gait, leading to increased medial compartment forces as well as lateral soft tissue lengthening. Additionally, a fixed varus deformity is associated with medial soft tissue contractures of the deep and superficial medial collateral ligament (MCL) and posteromedial capsule. With a fixed varus deformity, soft tissue releases may be necessary to create equivalent and rectangular flexion and extension gaps. There may also be anteromedial tibial bone defects, medial femoral condyle defects, and occasionally flexion contractures, especially in more severe cases. In cases of severe varus deformity with medial tibial bone loss, bone defects must be addressed to ensure adequate implant support. In many cases, a primary knee implant can be utilized in cases of varus knee deformity, but occasionally prostheses with higher levels of constraint may be required to balance and stabilize the knee. TKA has had a successful track record, with high levels of long-term implant survivorship even in cases of severe varus. Iatrogenic MCL instability and tibial aseptic loosening are complications associated with TKA in cases of severe varus, and multiple methods to avoid complications are presented here.

Does referencing system affect the selection of implant size, position and gap balance in total knee arthroplasty?

Background(1) To evaluate if referencing system affects selection of implant size, position, and gap balance in total knee arthroplasty (TKA) with the use of contemporary implant designs and (2) to describe the authors’ intraoperative sizing strategy using anterior referencing (AR) and posterior referencing (PR) systems. MethodsThis was a retrospective review of 270 consecutive patients (397 knees) who underwent primary TKA with an AR or PR system. Selection of implant size, mediolateral and anteroposterior alignment of the femoral component, as well as gaps were compared between groups. ResultsIn the AR group, more patients had femoral components which were upsized or downsized compared to those in the PR group (29.5% vs 12.0% respectively) and in patients who underwent bilateral TKA, 49.4% of those in the AR group had femur component size asymmetry. The AR group had better medio-lateral (ML) fit over the distal cutting surface area, smaller change in anterior offset but higher incidence of anterior notching when compared to the PR group. Posterior condylar offset (PCO) was restored in both groups and gap differences in flexion–extension and ML were comparable. There was also no difference in clinical scores and ROM between groups at 2-years follow-up. ConclusionIn this study, conventional implications related to referencing system were not observed. In practice, AR systems can restore PCO while PR systems do not result in increased anterior notching or anterior overstuffing. Differences observed in this study are most likely related to implant design specifics and surgical technique.

Virtual assessment of coronal balance prior to bone resection with the MAKO robotic-assisted system accurately predicts final balance in TKA.

Total knee arthroplasty (TKA) has traditionally relied on the surgeon's judgement and manual instruments to determine balance. The MAKO robotic system (Stryker Ltd, Kalamazoo, MI, USA) allows assessment of virtual compartmental gaps from CT-derived bone models intra-operatively as a predictor of soft tissue balance that will be achieved, prior to any bony resection. This study aims to assess the accuracy of this pre-resection balancing technique in determining the resultant final soft tissue balance of the TKA. A consecutive prospective cohort of 2027 Robotic-Assisted TKAs (RATKA) were performed between January'17 and March'22. Osteophytes were removed; initial virtual gaps on the virtual bone model were measured at 10° and 90° of flexion prior to bone resections. Optimization of the virtual component positions was then made and final pre-resection gaps were measured. The gaps were then re-assessed post-implantation and compared to the final pre-resection values. Virtual balancing in extension within 1mm was achieved in 95% of cases. Of those, 98% maintained coronal balance within 1mm after implantation, with 1.5% requiring a coronal plane soft tissue release. Inability to virtually balance a TKA within 2mm prior to bone resection resulted in a soft tissue release in 44.4% of cases. The absolute values of the final gaps achieved were a mean of 1.3mm greater than virtual gaps. The ability to balance a knee on the virtual bone model prior to bone resection, in conjunction with robotic-assisted execution of TKA, consistently achieves a balanced knee after component implantation.

Gap Pattern in Valgus Knee: An Assessment with TKA Navigation

Background: Valgus knee is a challenge of ligament balance in total knee arthroplasty (TKA). A lateral release is often recommended to achieve symmetric extension gaps in valgus deformity, due to the traditional requirements of tight lateral gap. However, the gap pattern valgus osteoarthritis knee has not been studied. Materials and Methods: The present study was a retrospective study on navigated TKA with 89 valgus osteoarthritis knees. The gap measurement, bone cut, and component rotation values were collected from navigation and the data were analyzed. Results: Only 6.70% of valgus knees in the present series had a narrower lateral flexion gap than medial flexion gap and 7.90% had narrower lateral extension gap than medial extension gap. Conversely, most of valgus cases were seen in bigger lateral flexion gaps than medial flexion gaps at 76.4%. This was consistent with the extension gap patterns of 80.9%. The degree of valgus deformity positively correlated with all gaps, except for flexion lateral gap. The present study demonstrated a mean external rotation of 2.25±2.09° in the femoral component rotation and the degree of valgus deformity had no significant correlation with femoral rotation. Conclusion: The lateral distal femoral condyle hypoplasia might have more important role in the extension gap than the ligament tension. The lateral ligament might influence the lateral flexion gap more than the lateral femoral condyle deficiency. Lateral structural release for correction of valgus deformity during extension could lead to instability in flexion especially for gap patterns with a lateral flexion gap that is wider than the medial flexion gap. Keywords: Valgus knee; Navigated TKA; Gap pattern

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.

Ligament Tension and Balance before and after Robotic-Assisted Total Knee Arthroplasty - Dynamic Changes with Increasing Applied Force.

The optimal force applied during ligament balancing in total knee arthroplasty (TKA) is not well understood. We quantified the effect of increasing distraction force on medial and lateral gaps throughout the range of knee motion, both prior to and after femoral resections in tibial-first gap-balancing TKA. Twenty-five consecutive knees in 21 patients underwent robotic-assisted TKA. The posterior cruciate ligament was resected, and the tibia was cut neutral to the mechanical axis. A digital ligament tensioning tool recorded gaps and applied equal mediolateral loads of 70 N (baseline), 90 N, and 110 N from 90 degrees to full extension. A gap-balancing algorithm planned the femoral implant position to achieve a balanced knee throughout flexion. After femoral resections, gap measurements were repeated under the same conditions. Paired t-tests identified gap differences between load levels, medial/lateral compartments, and flexion angle. Gaps increased from 0 to 20 degrees in flexion, then remain consistent through 90 degrees of flexion. Baseline medial gap was significantly smaller than lateral gap throughout flexion (p <0.05). Increasing load had a larger effect on the lateral versus medial gaps (p <0.05) and on flexion versus extension gaps. Increasing distraction force resulted in non-linear and asymmetric gap changes mediolaterally and from flexion to extension. Digital ligament tensioning devices can give better understanding of the relationship between joint distraction, ligament tension, and knee stiffness throughout the range of flexion. This can aid in informed surgical decision making and optimal soft tissue tensioning during TKA.

Effects of Severe Varus Deformity on Soft Tissue Balancing in Total Knee Arthroplasty.

This study aimed to establish the effect of severe varus deformity on soft tissue balance in total knee arthroplasty (TKA), which is not yet well established. We retrospectively enrolled 205 patients (270 knees) who underwent primary TKA using the measured resection technique. Four intraoperatively measured TKA gaps and gap differences were compared between the severe varus deformity group (Hip-knee-ankle [HKA] varus angle ≥ 10°) and the mild varus deformity group (HKA varus angle < 10°). Pearson’s correlation analysis and multiple linear regression analysis were used to investigate the factors affecting flexion and extension gap differences (FGD and EGD). A receiver operating characteristic curve was applied to assess the cut-off value of the HKA varus angle to discriminate the rectangular gap. The FGD (1.42 ± 1.35 mm vs. 1.05 ± 1.16 mm, p = 0.019) and the EGD (1.45 ± 1.32 mm vs. 0.97 ± 1.53 mm, p = 0.006) were significantly larger in severe varus deformity group than in mild varus deformity group. The HKA varus angle was positively correlated with both FGD (r = 0.264, p < 0.001) and EGD (r = 0.319, p < 0.001) and was an influencing factor for FGD (β = 0.232, p = 0.040) and EGD (β = 0.229, p = 0.037). A preoperative HKA angle of 12.4° was selected as the cutoff value to discriminate between rectangular and trapezoidal gaps. Thus, the severity of varus deformity (HKA varus angle) was found to be a significant factor affecting the mediolateral gap difference in TKA. When performing TKA in a knee with an HKA varus angle ≥ 12.4°, a trapezoidal gap is more likely to be expected. Level of evidence III, case−control study.

Sensor Assessment of Gap Balance in Mobile-Bearing Unicompartmental Knee Arthroplasty.

The most important procedure of mobile-bearing unicompartmental knee arthroplasty (UKA) is to balance the knee flexion and extension gap. Conventionally, the balance was determined by the subjective assessment of plugging out the feeling gauge. Since it mainly depended on the surgeons' experience, the accuracy was always in doubt. In the past 10 years, pressure sensors have been introduced to guide the gap balance in total knee arthroplasty (TKA). However, the sensor technique was introduced to UKA very recently. Herein is our sensor assessment of the gap balance in 20 cases UKA by one experienced surgeon. The sensor was a custom-designed force sensor matrix according to the shape of the tibial trial of mobile-bearing UKA. The postoperative clinical outcomes and radiographic results were recorded for future comparison. We aim to use this method to assess more than 200 cases of UKA by various surgeons to ultimately standardize the gap-balance result.

Shear wave tensiometry tracks reductions in collateral ligament tension due to incremental releases.

Surgeons routinely perform incremental releases on overly tight ligaments during total knee arthroplasty (TKA) to reduce ligament tension and achieve their desired implant alignment. However, current methods to assess whether the surgeon achieved their desired reduction in the tension of a released ligament are subjective and/or do not provide a quantitative metric of tension in an individual ligament. Accordingly, the purpose of this study was to determine whether shear wave tensiometry, a novel method to assess tension in individual ligaments based on the speed of shear wave propagation, can detect changes in ligament tension following incremental releases. In seven medial and eight lateral collateral porcine ligaments (MCL and LCL, respectively), we measured shear wave speeds and ligament tensions before and after incremental releases consisting of punctures with an 18-gauge needle. We found that shear wave speed squared decreased linearly with decreasing tension in both the MCL (average coefficient of determination(R2 avg ) = 0.76) and LCL (R2 avg = 0.94). We determined that errors in predicting tension following incremental releases were 26.2 and 14.2 N in the MCL and LCL, respectively, using ligament-specific calibrations. These results suggest shear wave tensiometry is a promising method to objectively measure the tension reduction in released structures.Clinical Significance: Direct, objective measurements of the tension changes in individual ligaments following release could enhance surgical precision during soft tissue balancing in total knee arthroplasty. Thus, shear wave tensiometry could help surgeons reduce the risk of poor outcomes associated with overly tight ligaments, including residual knee pain and stiffness.

Effect of Posterior Osteophytes on Total Knee Arthroplasty Coronal Soft Tissue Balance: Do They Matter?

Achieving coronal plane balance in total knee arthroplasty (TKA) is of paramount importance. There is concern that obtaining balancing before removal of posterior osteophytes may lead to asymmetrical extension balance once removed. We hypothesized that there is a particular posterior osteophyte size and location that does not result in significant change in coronal gap balancing. In this study of 245 robotic arm-assisted TKAs, the size and location of posterior osteophytes were obtained from preoperative computer tomography scans. Gap measurements at 10°-25° and 90° flexion after removal of medial and lateral osteophytes, before and after posterior osteophyte removal and bone resection were compared with respect to the size and location of posterior osteophytes. The largest size posterior osteophytes measured >10mm in 8.2% of cases, 5-10mm in 34.7%, <5mm in 23.7%, and 23.7% had no osteophytes. The mean osteophyte size was 5.7mm. The cohorts with and without posterior osteophytes were both found to have significant but similar changes in all gaps after osteophyte removal and bone resection (mean 0.8-1.4mm, P < .0001 and mean 0.7-1.7mm, P < .0001, respectively). Osteophyte size and location had no significant effect on the change in postresection gaps. This included osteophytes greater than 10mm, but their incidence was small. There is a small significant change in gaps between initial assessment and subsequent TKA bone resections, with or without posterior osteophytes. Our study found that where the surgeon thoroughly removes the medial and lateral osteophytes on initial exposure, posterior osteophytes <10mm can be ignored during initial knee coronal balancing.

Osseous Morphological Differences in Knee Osteoarthritis.

Improved understanding of the morphological characteristics of knees with osteoarthritis (OA) and various deformities can enable personalized implant positioning and balancing in total knee arthroplasty in an effort to continue improving clinical outcomes and optimizing procedural value. Therefore, the purpose of this study was to outline morphological differences in the medial and lateral distal femur and proximal tibia associated with varus and valgus deformities in knee OA. A large computed tomography (CT) database was used to identify 1,158 knees, which were divided into normal and osteoarthritic groups; the latter was further divided on the basis of deformity into neutral, varus, and valgus subgroups. Morphological measurements included the non-weight-bearing hip-knee-ankle angle (nwHKA), mechanical lateral distal femoral angle (mLDFA), medial proximal tibial angle (MPTA), rotation of the posterior condylar axis (PCA) relative to the surgical transepicondylar axis (sTEA), ratio of medial to lateral posterior condylar offset, ratio of medial to lateral condylar radius, medial posterior slope (MPS), lateral posterior slope (LPS), medial coronal slope (MCS), and lateral coronal slope (LCS). Compared with the normal group, the OA group was in overall varus (nwHKA, -2.2° ± 5.0° compared with -0.2° ± 2.4°) and had a significantly smaller MPS (8.4° ± 4.0° compared with 9.2° ± 4.0°), larger LPS (9.2° ± 3.6° compared with 7.2° ± 3.3°), and smaller MCS (82.1° ± 4.3° compared with 83.9° ± 3.3°). Differences among the OA subgroups were also observed for the MCS and LCS. Compared with the normal group, the sTEA of the OA group was less externally rotated relative to the PCA (0.3° ± 1.5° compared with 1.2° ± 1.9°), and both the condylar offset ratio (1.01 ± 0.06 compared with 1.04 ± 0.07) and the condylar radius ratio (0.98 ± 0.07 compared with 1.03 ± 0.07) were smaller. Only the condylar radius ratio showed differences among the OA subgroups, with valgus deformity associated with a larger ratio. An analysis of CT scans of 965 healthy and 193 osteoarthritic knees revealed significant differences in PCA, condylar offset, and condylar radius as well as tibial slope in both the sagittal and coronal planes. There is a strong need to evolve toward a more personalized treatment for osteoarthritic knees that utilizes implants and technology to help tailor total knee arthroplasty on the basis of the patient's morphologic characteristics.

Novel Force Measurement System for Soft Tissue Balance in Total Knee Arthroplasty Based on Flexible Pressure Sensor Arrays

Total knee arthroplasty (TKA) is a common treatment for terminal knee arthropathy. Soft tissue balance is one of the key factors affecting the success rate of TKA. However, current measurement systems still face great challenges in terms of accuracy and timeliness. Herein, a novel force measurement system based on a smart spacer is proposed to measure soft tissue balance in a timely and accurate manner. The smart spacer is designed according to the simulated results, where six flexible pressure sensors with a high sensitivity of 99.56 N−1 and a wide detection range of 50 N are attached to the spacer base to directly detect the soft tissue balance force. Moreover, a soft tissue balance measurement system is constructed, which can measure the force at different positions, such as the extension position (0°), the middle position (45°), and the flexion position (90°), and display them on the computer in a timely manner. This novel real‐time knee soft tissue balance measurement system provides a way for surgeons or knee joint replacement surgery robots to accurately evaluate soft tissue balance and paves the way for improving the success rate of TKA and the patient's postoperative rehabilitation.