Biomechanical effects of stem extension of tibial components for medial tibial bone defects in total knee arthroplasty: A finite element study.

The aim of this study was to investigate the biomechanical effects of stem extension with a medial tibial bone defect in primary total knee arthroplasty on load distribution and stress in the proximal tibia using finite element analysis. Finite element simulations were performed on the tibia bone to evaluate the stress and strain on the tibia bone and bone cement. This was done to investigate the stress-shielding effect, stability of tibia plate, and the biomechanical effects in total knee arthroplasty models with various medial defect and different stem length models. The results showed that in the bone defect model, the longer stem, the lower average von Mises stress on the cortical and trabecular bones. In particular, as the bone defect increased, the average von Mises stress on cortical and trabecular bones increased. The average increase in stress according to the size of the bone defect was smaller in the long stem than in the short stem. The maximal principal strain on the trabecular bone occurred mainly at the contact point on the distal end of stem of the tibial implant. When a short stem was applied, the maximal principal strain on the trabecular bone was approximately 8% and 20% smaller than when a long stem was applied or when no stem was applied, respectively. The findings suggest that a short stem extension of the tibial component could help achieve excellent biomechanical results when performing total knee arthroplasty with a medial tibial bone defect.

The Application of Virtual Reality in Shoulder Surgery Rehabilitation.

To achieve a positive functional prognosis in orthopedic surgery, particularly in shoulder surgeries, effective rehabilitation is essential. Recently, there has been growing interest in the use of virtual reality (VR) in the field of orthopedics, particularly for preoperative education and training, as well as clinical and home-based rehabilitation. This report describes the process of developing an application utilizing Meta Quest 2 VR technology (Meta, CA, USA) for rehabilitation after shoulder surgery. This application assists patients in performing postoperative exercises at home by wearing VR equipment tailored to their postoperative weeks. The advantages of VR rehabilitation lie in overcoming the limitations of traditional rehabilitation methods and providing patients with a better rehabilitation experience. Moreover, automating the rehabilitation process and reducing patients' visits to clinics can lead to cost savings. This report raises expectations for the potential and scalability of VR utilization, extending beyond orthopedics to other fields. In addition, it anticipates that with better feedback and motivation, the rehabilitation effects for patients can be further enhanced.

An Image-Based Augmented Reality System for Achieving Accurate Bone Resection in Total Knee Arthroplasty.

Background and objective With the steady advancement of computer-assisted surgical techniques, the importance of assessing and researching technology related to total knee arthroplasty (TKA) procedures has increased. Augmented reality (AR), a recently proposed next-generation technology, is expected to enhance the precision of orthopedic surgery by providing a more efficient and cost-effective approach. However, the accuracy of image-based AR in TKA surgery has not been established. Therefore, this study aimed to determine whether accurate bone resection can be achieved in TKA surgery using image-based AR. Methods In this study, we replaced traditional CT imaging and reconstructions for creating a bone 3D model by direct 3D scanning of the femur and tibia. The preoperative planning involved identifying anatomical landmarks and determining the surgical details. During surgery, markers were employed to create a local coordinate system for an AR-assisted surgical system using a Polaris camera. This approach helped minimize discrepancies between the 3D model and actual positioning, ensuring accurate alignment. Results The AR-assisted surgery using the image method resulted in fewer errors [average error: 0.32 mm; standard deviation (SD): 0.143] between the bone resection depth of the preoperative surgical plan and the bone model test results. Conclusions Our findings demonstrated the accuracy of bone resectioning by using image-based AR-assisted navigation for TKA surgery. Image-based AR-assisted navigation in TKA surgery is a valuable tool not only for enhancing accuracy by using smart glasses and sensors but also for improving the efficiency of the procedure. Therefore, we anticipate that image-based AR-assisted navigation in TKA surgery will gain wide acceptance in practice.

Reliability and modality analysis of patellar height measurement in pediatric knee.

Introduction: Various measurement methods and imaging technique are in use to measure patellar height in pediatric patients. However, there is no gold standard as to which measurement method and modality are the most reliable for pediatric patients. Therefore, the aim of this study was to determine the inter-observer reliability, intra-observer reliability, and applicability of various patellar height measurement methods in pediatric knee. Additionaly, we analyzed the reliability across different imaging modalities. Methods: Total 450 pediatric patients (age: 5-18 years) were evaluated using lateral knee radiographs and magnetic resonance imaging (MRI). The patellar height ratios were measured using five methods. Five methods were Insall-Salvati (IS), Koshino-Sugimoto (KS), Blackburne-Peel (BP), modified Insall-Salvati (MIS), and Caton-Deschamps (CD). The patients were categorized into two age groups: P (ages 5-13) and Q (ages 14-18). Each measurement was conducted twice by two raters. The intra-observer reliability, inter-observer reliability and inter-modality reliability were calculated. In addition, applicability was defined as the possibility to apply each measurement method to each age group. Results: The KS method showed the highest inter-observer reliability and intra-observer reliability when using MRI for both age groups. The inter-observer reliability and intra-observer reliability of the IS for lateral knee radiographs was highest among all observers for group Q. The CD method showed the highest inter-observer reliability in group P, while the KS showed the highest intra-observer reliability in group P using lateral radiographs. The KS method showed the highest inter-modality reliability in group P, while the IS showed the highest inter-modality reliability in group Q. The KS method was applicable to all patients when using lateral knee radiography, and the IS method was applicable to all patients when using MRI. Conclusions: Our results show that the reliability of various measurement method and imaging technique differed based on pediatric knee age group when measuring patellar height. Therefore, in the case of pediatric patients, reliability measurement methods and imaging techniques according to the patient's age should be applied.

Preoperative joint line obliquity, a newly identified factor for overcorrection, can be incorporated into a novel preoperative planning method to optimise alignment in high tibial osteotomy.

PURPOSE: The aim of this study was to analyse the factors associated with additional postoperative alignment changes after accurate bony correction by selecting only patients with well-performed bony correction as planned and develop a method of incorporating significant factors into preoperative planning. METHODS: Among 104 consecutive patients who underwent medial open wedge high tibial osteotomy (MOWHTO) between October 2019 and July 2022, 61 with well-performed bony corrections were retrospectively reviewed. The major criterion for well-performed bony correction was a difference of <1° between the simulated medial proximal tibial angle (MPTA) and the actual postoperative MPTA as measured in three dimensions. Radiographic parameters, such as the joint line convergence angle (JLCA) and joint line obliquity (JLO), were measured preoperatively and postoperatively, utilising standing and supine whole lower extremity anteroposterior, valgus and varus stress radiographs. Multiple linear regression analysis identified the factors affecting alignment changes, and a prediction model was developed. A method for applying this prediction model to preoperative planning was proposed. RESULTS: Preoperative JLCA on standing (preJLCAstd ), preoperative JLCA on 0° valgus stress radiograph (vgJLCA0 ), and preoperative JLO (preJLO) were significantly correlated with JLCA change (∆JLCA) (p < 0.001, p < 0.001, p = 0.006). The prediction model was estimated as ∆JLCA = 0.493 × (vgJLCA0 ) - 0.727 × (preJLCAstd ) + 0.189 × (preJLO) - 1.587 in. (R = 0.815, modified R2 = 0.646, p < 0.001). The proposed method resulted in a reduced overcorrection rate (p = 0.003) and an improved proportion of acceptable alignments (p = 0.013). CONCLUSION: PreJLCAstd , vgJLCA0  and preJLO can be used to estimate ∆JLCA. PreJLO was recently identified as a significant factor associated with additional alignment changes. Utilising the proposed preoperative planning and a prediction model with these factors shows promise in calibrating postoperative alignment after MOWHTO. LEVEL OF EVIDENCE: Level III, retrospective cohort study.

Could We Expect Postoperative Cup Anteversion after Total Hip Arthroplasty Using Postoperative Plain Anteroposterior and Lateral Radiograph? A Three-Dimensional Experimental Operation Study.

BACKGROUND: A postoperative radiograph in total hip arthroplasty (THA) is usually obtained to evaluate the inclination and anteversion of the acetabular components. However, there is no gold-standard method for calculating the exact inclination and anteversion of the acetabular components on post-THA radiographs. We aimed to measure the actual anteversion of the acetabular component on postoperative radiographs by obtaining correlation data between the virtual and actual acetabular component positioning using virtual three-dimensional (3D) surgery. METHODS: A total of 64 hip scans of 32 patients who underwent lower-extremity computed tomography (CT) were retrospectively reviewed. We reconstructed 3D models of the 64 hips using customized computer software (Mimics). Furthermore, to identify the safe zone of acetabular component position in THA, we performed virtual 3D surgery simulations for five anteversion (-10°, 0°, 10°, 20°, and 30°) and five inclination (20°, 30°, 40°, 50°, and 60°) types. We analyzed the acetabular anatomy using 3D models to measure the radiographic, anatomical, and operative anteversion (RA, AA, OA) and inclination (RI, AI, OI) angles. Additionally, we used the Woo-Morrey (WM) method to calculate the anteversion angle in the reconstructed cross-table lateral (CL) radiographs and determined the correlation between these measurements. RESULTS: The safe zone of the acetabular component was visualized on post-THA CL radiographs using the WM method of anteversion measurement based on the different anteversions and inclinations of the acetabular component. The AA, RA, OA, OI, and WM differed significantly between males and females (p value < 0.05). As the anatomical inclination or anteversion increased, the WM anteversion measurements also increased. The radiographic anteversion measurement best matched the WM method of measurement, followed by anatomical and operative methods. CONCLUSIONS: The actual anteversion of the acetabular component after THA can be measured on CL radiographs with the WM method using a 3D virtual program, with good reproducibility.

Effect of surface matching mismatch of focal knee articular prosthetic on tibiofemoral contact stress using finite element analysis.

Aims: Focal knee arthroplasty is an attractive alternative to knee arthroplasty for young patients because it allows preservation of a large amount of bone for potential revisions. However, the mechanical behaviour of cartilage has not yet been investigated because it is challenging to evaluate in vivo contact areas, pressure, and deformations from metal implants. Therefore, this study aimed to determine the contact pressure in the tibiofemoral joint with a focal knee arthroplasty using a finite element model. Methods: The mechanical behaviour of the cartilage surrounding a metal implant was evaluated using finite element analysis. We modelled focal knee arthroplasty with placement flush, 0.5 mm deep, or protruding 0.5 mm with regard to the level of the surrounding cartilage. We compared contact stress and pressure for bone, implant, and cartilage under static loading conditions. Results: Contact stress on medial and lateral femoral and tibial cartilages increased and decreased, respectively, the most and the least in the protruding model compared to the intact model. The deep model exhibited the closest tibiofemoral contact stress to the intact model. In addition, the deep model demonstrated load sharing between the bone and the implant, while the protruding and flush model showed stress shielding. The data revealed that resurfacing with a focal knee arthroplasty does not cause increased contact pressure with deep implantation. However, protruding implantation leads to increased contact pressure, decreased bone stress, and biomechanical disadvantage in an in vivo application. Conclusion: These results show that it is preferable to leave an edge slightly deep rather than flush and protruding.

Evaluation of lateral and anterior center-edge angles according to sex and anterior pelvic plane tilt angle: a three-dimensional quantitative analysis.

BACKGROUND: This study aimed to quantitatively evaluate lateral center-edge angle (LCEA) and anterior center-edge angle (ACEA) according to sex and the anterior pelvic plane (APP) tilt angle and analyze the correlation between these measurements and acetabular coverage. METHODS: Computed tomography scans of 71 adults (38 men and 33 women) with normal hip joints were obtained. LCEA, anterior ACEA, and acetabular coverage were measured with APP tilt every 5° from - 30° to + 30° and were compared between the sexes. The correlation between acetabular coverage and LCEA/ACEA was also analyzed. RESULTS: (1) LCEA, ACEA, and acetabular coverage were statistically larger in men than in women at all APP tilt angles (with the exception of acetabular coverage ≥ 25°). (2) LCEA, ACEA, and acetabular coverage differed according to APP tilt angle. LCEA and acetabular coverage showed maximum values at 10°. ACEA showed a tendency to increase by an average of 3.6° for every 5° increase in the APP tilt angle. LCEA demonstrated strong and very strong associations across all APP tilting angles, whereas ACEA showed a moderate association at angles ≥ 15° in men and ≥ 30° in women. CONCLUSIONS: The LCEA and ACEA are adequate measurement methods that reflect actual acetabular coverage unless the pelvis is tilted excessively anteriorly. While pelvic tilting does not need to be considered for LCEA within the physiologic range, it should always be taken into account for ACEA, as it increases by an average of 3.6° for every 5° increase in APP tilt angle. LEVEL OF EVIDENCE: Level III: retrospective cohort study.

Computational analysis of tibial slope adjustment with fixed-bearing medial unicompartmental knee arthroplasty in ACL- and PCL-deficient models.

AIMS: A functional anterior cruciate ligament (ACL) or posterior cruciate ligament (PCL) has been assumed to be required for patients undergoing unicompartmental knee arthroplasty (UKA). However, this assumption has not been thoroughly tested. Therefore, this study aimed to assess the biomechanical effects exerted by cruciate ligament-deficient knees with medial UKAs regarding different posterior tibial slopes. METHODS: ACL- or PCL-deficient models with posterior tibial slopes of 1°, 3°, 5°, 7°, and 9° were developed and compared to intact models. The kinematics and contact stresses on the tibiofemoral joint were evaluated under gait cycle loading conditions. RESULTS: Anterior translation increased in ACL-deficient UKA cases compared with intact models. In contrast, posterior translation increased in PCL-deficient UKA cases compared with intact models. As the posterior tibial slope increased, anterior translation of ACL-deficient UKA increased significantly in the stance phase, and posterior translation of PCL-deficient UKA increased significantly in the swing phase. Furthermore, as the posterior tibial slope increased, contact stress on the other compartment increased in cruciate ligament-deficient UKAs compared with intact UKAs. CONCLUSION: Fixed-bearing medial UKA is a viable treatment option for patients with cruciate ligament deficiency, providing a less invasive procedure and allowing patient-specific kinematics to adjust posterior tibial slope. Patient selection is important, and while AP kinematics can be compensated for by posterior tibial slope adjustment, rotational stability is a prerequisite for this approach. ACL- or PCL-deficient UKA that adjusts the posterior tibial slope might be an alternative treatment option for a skilled surgeon. Cite this article: Bone Joint Res 2022;11(7):494-502.

Finite element analysis of femoral component sagittal alignment in mobile-bearing total knee arthroplasty.

BACKGROUND: Recently, there has been an increasing interest in mobile-bearing total knee arthroplasty (TKA). However, changes in biomechanics for femoral component alignment in mobile-bearing TKA have not been explored in depth. OBJECTIVE: This study aims to evaluate the biomechanical effect of sagittal alignment of the femoral component in mobile-bearing TKA. METHODS: We developed femoral sagittal alignment models with -3°, 0°, 3°, 5°, and 7° flexion. We also examine the kinematics of the tibiofemoral (TF) joint, contact point on the TF joint, contact stress on the patellofemoral (PF) joint, collateral ligament force, and quadriceps force using a validated computational model under a deep-knee-bend condition. RESULTS: Posterior kinematics of the TF joint increases as the femoral component flexes. The contact stress on the PF joint, collateral ligament force, and the quadriceps force decreases as the femoral component flexes. CONCLUSIONS: Our results show that a slight, approximately 0°âˆ¼3°, flexion of the implantation could be an effective substitute technique. However, excessive flexion should be avoided because of the potential loosening of the TF joint.

Biomechanical effect of anatomical tibial component design on load distribution of medial proximal tibial bone in total knee arthroplasty : finite element analysis indicating anatomical design prevents stress-shielding.

AIMS: This study aimed to identify the effect of anatomical tibial component (ATC) design on load distribution in the periprosthetic tibial bone of Koreans using finite element analysis (FEA). METHODS: 3D finite element models of 30 tibiae in Korean women were created. A symmetric tibial component (STC, NexGen LPS-Flex) and an ATC (Persona) were used in surgical simulation. We compared the FEA measurements (von Mises stress and principal strains) around the stem tip and in the medial half of the proximal tibial bone, as well as the distance from the distal stem tip to the shortest anteromedial cortical bone. Correlations between this distance and FEA measurements were then analyzed. RESULTS: The distance from the distal stem tip to the shortest cortical bone showed no statistically significant difference between implants. However, the peak von Mises stress around the distal stem tip was higher with STC than with ATC. In the medial half of the proximal tibial bone: 1) the mean von Mises stress, maximum principal strain, and minimum principal strain were higher with ATC; 2) ATC showed a positive correlation between the distance and mean von Mises stress; 3) ATC showed a negative correlation between the distance and mean minimum principal strain; and 4) STC showed no correlation between the distance and mean measurements. CONCLUSION: Implant design affects the load distribution on the periprosthetic tibial bone, and ATC can be more advantageous in preventing stress-shielding than STC. However, under certain circumstances with short distances, the advantage of ATC may be offset. Cite this article: Bone Joint Res 2022;11(5):252-259.

Effects of the Anterolateral Ligament and Anterior Cruciate Ligament on Knee Joint Mechanics: A Biomechanical Study Using Computational Modeling.

Background: Recent studies on lateral knee anatomy have reported the presence of a true ligament structure, the anterolateral ligament (ALL), in the anterolateral region of the knee joint. However, its biomechanical effects have not been fully elucidated. Purpose: To investigate, by using computer simulation, the association between the ALL and anterior cruciate ligament (ACL) under dynamic loading conditions. Study Design: Descriptive laboratory study; Level of evidence, 5. Methods: The authors combined medical imaging from 5 healthy participants with motion capture to create participant-specific knee models that simulated the entire 12 degrees of freedom of tibiofemoral (TF) and patellofemoral (PF) joint behaviors. These dynamic computational models were validated using electromyographic data, muscle activation data, and data from previous experimental studies. Forces exerted on the ALL with ACL deficiency and on the ACL with ALL deficiency, as well as TF and PF contact forces with deficiencies of the ACL, ALL, and the entire ligament structure, were evaluated under gait and squat loading. A single gait cycle and squat cycle were divided into 11 time points (periods 0.0-1.0). Simulated ligament forces and contact forces were compared using nonparametric repeated-measures Friedman tests. Results: Force exerted on the ALL significantly increased with ACL deficiency under both gait- and squat-loading conditions. With ACL deficiency, the mean force on the ALL increased by 129.7% under gait loading in the 0.4 period (P < .05) and increased by 189% under high flexion during the entire cycle of squat loading (P < .05). A similar trend of significantly increased force on the ACL was observed with ALL deficiency. Contact forces on the TF and PF joints with deficiencies of the ACL, ALL, and entire ligament structure showed a complicated pattern. However, contact force exerted on TF and PF joints with respect to deficiencies of ACL and ALL significantly increased under both gait- and squat-loading conditions. Conclusion: The results of this computer simulation study indicate that the ACL and the ALL of the lateral knee joint act as secondary stabilizers to each other under dynamic load conditions.

Evaluation of age group and sex differences in the measurement of patellar height of pediatric knee in a Korean population.

Introduction: Various methods based on bony landmarks are used to determine patellar height. This study analyzed five methods for patellar height measurement on lateral knee radiographs, namely, the Insall-Salvati, Koshino-Sugimoto, Blackburne-Peel, modified Insall-Salvati, and Caton-Deschamps methods. Methods: Overall, 425 pediatric participants (221 males, 204 females; age range 5-18 years) were included and were divided equally into three age groups (A, 5-10 years; B, 11-13 years; and C, 13-18 years). For the comparison of the applicability of each method, the applicable probabilities for each age group and sex-based differences were analyzed using logistic regression techniques. Intra-rater reliability and inter-rater variability were analyzed by two trained raters. Results: The Koshino-Sugimoto method was applicable to all patients. The 80% applicable age of female patients was lower than that of male patients for the Blackburne-Peel (male = 11.9, female = 11) and Caton-Deschamps (male = 11.9, female = 11.1) methods. However, in the Insall-Salvati (male = 12, female = 12.1) and modified Insall-Salvati (male = 12.6, female = 13.1) methods, the 80% applicable age in male patients was lower than that in female patients. The Koshino-Sugimoto method showed the highest variability in group B, while the Insall-Salvati showed the highest variability in group C. In terms of intra-observer reliability, the Caton-Deschamps method showed the same reliability as the Insall-Salvati method, in group C. Conclusions: Our results demonstrated differences in the reliability, variability, and applicability of patellar height measurement methods according to age group. The applicability of patellar height measurement methods also differed according to sex. Therefore, based on age group and sex, different methods should be used for patellar height measurement in pediatric patients.

Existence of Gender-Based Difference in Morphology of Convex Lateral Tibial Plateau in Korean Population Primary Knee Joint Osteoarthritis.

PURPOSE: Morphological differences in the knee joints of females and males have been reported in a previous study. These differences have realized the need of developing a gender-specific prosthesis. However, anatomical studies on gender-based differences in the proximal tibial plateau's sagittal curvature have rarely been conducted. Therefore, this study is aimed at evaluating the geometry of the sagittal curvature of the proximal tibial plateau in the Korean population. METHODS: Three-dimensional data for the sagittal curvature of the tibial plateau morphology from 1976 patients (i.e., 299 male and 1677 female) were assessed using magnetic resonance imaging. The sagittal profiles of the tibial plateaus were also evaluated. The independent t-test and paired t-test were used for statistical analysis. RESULTS: The proximal tibia had concave and convex surfaces in the medial and lateral plateaus, respectively, for both genders. In addition, the medial diameter of the tibial plateau was significantly greater than the lateral diameter for both genders. Gender-based difference was not found in the medial diameter of the tibial plateau but was observed in the lateral diameter. CONCLUSION: These results may provide guidelines for a suitable knee implant design for the Korean patients. The incorporation of this shape information in the medial and lateral sides in the prosthetics for a total knee arthroplasty and a lateral unicompartmental knee arthroplasty can improve knee range motion.

Correlation of Femoral Trochlear Dysplasia With Anterior Cruciate Ligament Injury in Skeletally Immature Patients.

BACKGROUND: Reports of anterior cruciate ligament (ACL) injury in patients with skeletal immaturity have been increasing. Variations in knee joint anatomy have been linked to ACL injury risk factors. PURPOSE: To identify associations between ACL injury, patella alta, and femoral trochlear dysplasia in patients with skeletal immaturity by using magnetic resonance imaging (MRI). STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: This retrospective study included 231 patients with skeletal immaturity-116 with acute complete noncontact ACL injury and 115 without ACL injury (controls)-who underwent knee MRI. Cases of femoral trochlear dysplasia were divided into 4 types according to the Dejour classification scheme. Patellar height and patellar tendon length were measured via sagittal MRI, and the Insall-Salvati ratio (ISR) was calculated. RESULTS: In the ACL injury group, 56 (48.3%) knees exhibited trochlear dysplasia, including 51 (91.1%) that were Dejour type A; and in the control group, 12 (10.4%) knees exhibited trochlear dysplasia, 12 (100%) Dejour type A. The prevalence of femoral trochlear dysplasia was significantly higher in the ACL injury group than in the control group (P < .001). The ISR was not significantly different between the ACL injury and control groups (0.9 ± 0.2 vs 1 ± 0.2 mm; P = .16). The correlation between ISR >1.2 and presence of ACL injury was not significant. CONCLUSION: Femoral trochlear dysplasia was associated with ACL injury in patients with skeletal immaturity. In particular, Dejour type A femoral trochlear dysplasia was correlated with ACL injury patients with skeletal immaturity. Also, the possibility of ACL damage exists in patients with skeletal immaturity and femoral trochlear dysplasia.

Analysis of Gender Differences in the Rotational Alignment of the Distal Femur in Kinematically Aligned and Mechanically Aligned Total Knee Arthroplasty.

To compare the angle between the external rotation references of the femoral components in the axial plane by gender and lower limb alignment in Korean patients with osteoarthritis (OA). Magnetic resonance (MR) images of 1273 patients were imported into a modeling software and segmented to develop three-dimensional femoral bony and cartilaginous models. The surgical transepicondylar axis (sTEA), posterior condylar axis (PCA), the kinematically aligned axis (KAA), and anteroposterior axis were used as rotational references in the axial plane for mechanically aligned (MA) TKA. The relationship among axes were investigated. Among 1273 patients, 942 were female and 331 were male. According to lower limb alignment, the varus and valgus knee groups comprised 848 and 425 patients, respectively. All measurements, except PCA-sTEA, differed significantly between men and women; all measurements, except PCA-sTEA, did not differ significantly between the varus and valgus knee groups. In elderly Korean patients with OA, rotational alignment of the distal femur showed gender differences, but no differences were seen according to lower limb alignment. The concern for malrotation of femoral components during kinematically aligned TKA is less in Koreans than in Caucasians and relatively less in women than in men. In MA TKA, malrotation of the femoral components can be avoided by setting different rotational alignments for the genders.

Gender-Based Quantitative Analysis of the Grand Piano Sign in Mechanically Aligned Total Knee Arthroplasty in Asians.

In mechanically aligned (MA) total knee arthroplasty (TKA), the grand piano sign helps surgeons to further ensure the proper external rotation of the femoral component. The goal of this study was to determine the sex-related differences in the shape of the anterior resection surface using 3D magnetic resonance imaging (MRI) models. MRI scans were performed on 267 consecutive patients (202 women and 65 men) with osteoarthritis who underwent TKA in order to reconstruct a 3D model. Virtual anterior condylar resection was performed based on the surgical transepicondylar axis (sTEA), Whiteside's line (WSL), and flexion-extension axis (FEA). On the anterior resection surface, both lateral length (LatL) and medial length (MedL) were measured, and the ratio between the two (MedL/LatL) was calculated. The mediolateral width of the distal femur (ML) and anterior resection surface (M'L') were measured, and the ratio between the M'L' and ML (M'L'/ML) was calculated. Both the lateral deviation (LD) and the ratio between LD and ML (LD/ML) were also determined. Morphological classification of the anterior resection surface was conducted based on the presence of a definite medial peak. When based on the sTEA or WSL, the MedL/LatL of female subjects was significantly greater than that of male subjects (p < 0.001 and p < 0.05, respectively). The MedL/LatL of the FEA was consistently larger than that obtained using the sTEA or WSL. Among female subjects, the MedL/LatL of the sTEA was significantly greater than that of the WSL, although this was not the case in either the total study population or the male subjects alone. When based on the sTEA, the M'L'/ML was statistically greater in the female subjects (p < 0.01). The LD was greater in the male subjects (p < 0.01), but there was no difference between the male and female subjects when comparing the LD/ML (p = 0.93). The proportion of double- and single-peak types was not significantly different between the sexes (p = 0.196). Surgeons should be aware that the shape of the anterior resection surface may differ depending on the sex of the patient. The results of this study provide more consistent surgical outcomes as well as fundamental anatomical data for designing suitable prostheses applicable to the Korean population.

Effect of post-cam design on the kinematics and contact stress of posterior-stabilized total knee arthroplasty.

BACKGROUND: The post-cam mechanism in the posterior-stabilized (PS) implant plays an important role, such as durability and kinematic performances, in total knee arthroplasty (TKA). OBJECTIVE: The purpose of this study was to evaluate the difference in the kinematics and contact stress of five post-cam designs, which are flat-and-flat, curve-and-curve (concave), curve-and-curve (concave and convex), helical, and asymmetrical post-cam designs, using three-dimensional finite element models. METHODS: We designed the post-cam model with five different geometries. The kinematics, contact stress, and contact area were evaluated in the five post-cam designs under gait cycle loading conditions using the finite element method. RESULTS: There were no differences in the contact stress and area on the tibial insert in all designs. The largest internal rotation was shown in the swing phase for the helical design, and the largest tibial posterior translation was observed for the curve-and-curve (concave) design. The curve-and-curve (concave) design showed the lowest contact stress and the largest posterior tibial translation during the gait cycle. CONCLUSIONS: Considering the kinematics and contact stress, we found that the curve-and-curve (concave) design was more stable than other designs. From the results, we found the important factors of TKA implant considering stability and kinematics.

Anatomic Differences in the Sagittal Knee Joint Are Associated With ACL Injury: Results From a Skeletally Immature Korean Population.

BACKGROUND: Differences in tibiofemoral articular morphology are associated with risks of anterior cruciate ligament (ACL) injury. PURPOSE: To determine whether bony and cartilaginous morphological characteristics are related to ACL injury in pediatric patients and to investigate any differences according to sex. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: A total of 200 skeletally immature Korean patients from a single institution were included in this study; 100 patients had an ACL injury, and 100 had an intact ACL. Condylar morphology and tibial slopes were evaluated and compared between the groups, and differences between sexes were evaluated in the ACL-injured group. RESULTS: The lateral femoral curvature was significantly greater and the lateral and medial tibial curvatures were significantly smaller in the ACL-injured group than in the intact group (P < .01 for all). In addition, the lateral and medial femoral curvatures as well as the lateral tibial curvature were significantly smaller in female than in male patients (P < .01 for all). Both the medial and lateral tibial slopes were greater in the ACL-injured versus intact group (medial slope, 5.5° vs 5.0°; lateral slope, 3.0° vs 1.3°, respectively); this difference was statistically significant for lateral tibial slope (P = .026). No sex-based differences were found for medial or lateral tibial slope. CONCLUSION: Femoral and tibial curvatures as well as lateral tibial slope were significantly different between the ACL-injured and ACL-intact patients, and the lateral tibial curvature was significantly smaller in female than in male patients. Medial and lateral tibial slopes were not associated with a significant difference in ACL injury between male and female patients.

Biomechanical Difference between Conventional Transtibial Single-Bundle and Anatomical Transportal Double-Bundle Anterior Cruciate Ligament Reconstruction Using Three-Dimensional Finite Element Model Analysis.

The purpose of our study was to analyze the graft contact stress at the tunnel after transtibial single-bundle (SB) and transportal double-bundle (DB) anterior cruciate ligament (ACL) reconstruction. After transtibial SB (20 cases) and transportal DB (29 cases) ACL reconstruction, the three-dimensional image of each patient made by postoperative computed tomography was adjusted to the validation model of a normal knee and simulated SB and DB ACL reconstructions were created based on the average tunnel position and direction of each group. We also measured graft and contact stresses at the tunnel after a 134 N anterior load from 0° to 90° flexion. The graft and contact stresses became the greatest at 30° and 0° flexion, respectively. The total graft and contact stresses after DB ACL reconstruction were greater than those after SB ACL reconstruction from 0° to 30° and 0° to 90° knee flexion, respectively. However, the graft and contact stresses of each graft after DB ACL reconstruction were less than those after SB ACL reconstruction. In conclusion, the total graft and total contact stresses after DB ACL reconstruction are higher than those after SB ACL reconstruction from 0° to 30° and 0° to 90° knee flexion, respectively. However, the stresses of each graft after DB ACL reconstruction are about half of those after SB ACL reconstruction.