Gap Volume Based on CT Measurement Is a Strong Risk Factor for Delayed Gap Healing After Open-wedge High Tibial Osteotomy.

PURPOSE: To identify factors that affect delayed gap healing after open-wedge high tibial osteotomy (OWHTO), and to determine whether large gap volume is a predictor of delayed gap healing. METHODS: This retrospective study analyzed biplane OWHTO performed between 2019 and 2023 for knee osteoarthritis or osteonecrosis. The minimum follow-up was 1 year. Delayed gap healing was defined as when the medial half of the osteotomy gap area had not reached the consolidation phase by 6 months after surgery based on anteroposterior knee radiographs. Gap volume was calculated from computed tomography images. Logistic regression was performed using body height, smoking, correction angle, hinge fracture, flange thickness, and gap volume. A gap volume cutoff value for delayed gap healing was determined with receiver operating characteristic curve analysis. Gap volume was predicted with multiple linear regression. RESULTS: There were 80 knees in 71 patients (36 men and 44 women). The mean gap volume was 7.6 cm3. Gap healing rates at 3, 6, 9, and 12 months after surgery were 26%, 65%, 89%, and 100%, respectively. There were 25 knees with delayed gap healing. Male sex was not a significant risk factor when adjusted for body height. Multivariate logistic regression revealed that only larger gap volume was a significant risk factor (odds ratio, 1.45; P = .006). The gap volume cutoff value was 7.6 cm3, with an area under the curve of 0.74. Tall body height and a large correction angle (both P < .001) were associated with a significantly larger gap volume (R2 = 0.73). CONCLUSIONS: Large gap volume is the most important risk factor for delayed gap healing after OWHTO. Gap volume can be predicted based on body height and correction angle. When OWHTO with substantial correction is planned for a tall man, surgeons should be aware of possibly delayed gap healing.

Anterior Position of the Femoral Condyle During Mid-Flexion Worsens Knee Activity After Cruciate-Retaining Total Knee Arthroplasty.

BACKGROUND: The effects of kinematics on patient-reported outcome measures (PROMs) after cruciate-retaining (CR) total knee arthroplasty (TKA) remain unclear. This study investigated the effects of kinematic patterns after CR-TKA on PROMs. METHODS: We examined 35 knees (27 patients) undergoing primary CR-TKA. Knee kinematics and 2011 Knee Society Score were evaluated at a mean follow-up of 72.4 (± 28.2) months. Knee kinematics was analyzed using fluoroscopy, and the femoral antero-posterior position relative to the tibial component was assessed separately for medial and lateral compartments during a squat. The correlations between kinematics and PROMs were evaluated. RESULTS: The average amount of posterior femoral translation from full extension to maximum flexion was 0.2 (± 2.6) mm for the medial femoral condyle and 4.1 (± 2.9) mm for the lateral condyle. Medial pivot motion was observed in 24 knees (68.6%) with a low rate (14.3%) of paradoxical anterior translation. The anterior position of the medial femoral condyle at 60° had a negative impact on discretionary activities (ρ = -0.37; P = .039), and at maximum flexion, had a negative impact on total functional activities (ρ = -0.46; P = .005), advanced activities (ρ = -0.45; P = .006), and discretionary activities (ρ = -0.63; P < .001). Anterior position of the lateral femoral condyle at 30° had a negative impact on total functional activities (ρ = -0.48; P = .005), walking and standing (ρ = -0.56; P < .001), and advanced activities (ρ = -0.49; P = .004), and at 60° had a negative impact on walking and standing (ρ = -0.45; P = .010). CONCLUSIONS: The anterior positions of the medial and lateral femoral condyles at mid-flexion and maximum flexion had negative impacts on PROMs. Soft tissue conditions should be carefully managed to achieve medial knee joint stability, which can improve PROMs.

Opening-Wedge High Tibial Osteotomy With High Hinge Position Risks Lateral Hinge Fracture in Men With Posterolateral Tibial Condyle Protrusion.

PURPOSE: The primary aim of this study was to evaluate the 3-dimensional morphology of the proximal tibia around the osteotomy plane in open-wedge high tibial osteotomy, focusing on the posterolateral (PL) and posteromedial (PM) tibial condyles, and to clarify the changes in morphologic parameters due to differences in patient characteristics and hinge position. The secondary aim was to examine whether morphologic features were associated with insufficient osteotomy, which increases the risk of lateral hinge fracture (LHF). METHODS: The PL and PM anteroposterior distance, asymmetry ratio, and discrepancy between PL and PM distances along the tibial osteotomy plane were measured. We investigated changes in the parameters due to differences in patient characteristics and hinge position. Osteotomy configurations and LHFs were evaluated using postoperative computed tomography scans. RESULTS: The 3-dimensional preoperative plans of 117 knees (male, 41 knees; female, 76 knees) were evaluated. PL distances were larger than PM distances in almost all cases. The average asymmetry ratio was 1.35, and the standard deviation was 0.22. Higher hinge position was associated with a larger asymmetry ratio and discrepancy (P < .001). The asymmetry ratio and discrepancy were independently positively correlated with male sex (P = .002 and P = .001, respectively) and gentle posterior tibial slope (P < .001 and P < .001, respectively). Osteotomies with type III LHFs showed lower osteotomy sufficiency than osteotomies without LHFs (P < .001). CONCLUSIONS: PL tibial condyle protrusion was more pronounced in male patients and those with a high hinge position, and may result in insufficient PL osteotomy, which is a risk factor for type III LHF during open-wedge high tibial osteotomy. The optimal hinge position was located approximately 15 mm and 20 mm distal to the lateral tibial plateau in female and male patients, respectively. LEVEL OF EVIDENCE: IV: retrospective case series.

Hinge fractures reaching the tibial plateau can be caused by forcible opening of insufficient posterior osteotomy during open-wedge high tibial osteotomy.

PURPOSE: The purpose of this study was to use the finite element method (FEM) to reproduce fracture lines that reach the lateral tibial plateau during open-wedge high tibial osteotomy (OWHTO) in patients with Type III lateral hinge fracture (LHF). It was hypothesized that the FEM could clarify biomechanical causes of Type III LHF, enabling prevention of adverse complications. METHODS: This study used the nonlinear FEM to analyze the data of eight knees in eight patients (two males and six females) with Type III LHF among 82 patients who underwent OWHTO, as well as the data of eight individuals with no LHF. To predict the onset of Type III LHF, simulation models were also developed in which posterior osteotomy sufficiency varied from 50% to perfect, the latter defined as osteotomy reaching the hinge point. RESULTS: Real-life instances of Type III LHF caused by insufficient posterior osteotomy were reproduced in all patient-specific FEM models, and these models accurately predicted fracture types and locations. During opening of the osteotomy gap, the fracture line reached the lateral tibial plateau, and extended vertically from the end of the insufficient posterior osteotomy, avoiding the rigid proximal tibiofibular joint. In contrast, sufficient posterior osteotomy resulted in a lack of LHF. Posterior osteotomy extension ≥ 70% of the width of the osteotomy plane was the cut-off value to prevent Type III LHF. CONCLUSION: Forced opening of insufficient posterior osteotomy was found to be a biomechanical cause of Type III LHF that extended perpendicularly to the lateral tibial plateau, avoiding the proximal tibiofibular joint. The clinical significance of this study is that sufficient posterior osteotomy during OWHTO, defined as at least 70% of the width of the osteotomy plane, can prevent Type III LHF.

Larger bone marrow lesion volume before medial open-wedge high tibial osteotomy correlates with better improvement of clinical scores in patients with knee osteoarthritis.

PURPOSE: This study evaluated the clinical outcomes of medial open-wedge high tibial osteotomy (MOWHTO) and bone marrow lesion (BML) scores and volumes. The hypotheses were that quantitative BML volume is more associated with clinical outcomes of MOWHTO than qualitative BML evaluations, and pre-operative BML volume is associated with the improvement of clinical outcomes. METHODS: Patients who underwent MOWHTO were retrospectively enrolled. The Knee Injury and Osteoarthritis Outcome Score (KOOS) was recorded before the initial surgery and at plate removal surgery. Using pre-operative short-time inversion recovery magnetic resonance imaging, BMLs were evaluated using three qualitative scores, reflecting the maximum length, proportion, and intensity of BML. For quantification, BMLs of the femur and tibia were separately defined as lesions with a threshold greater than the mean signal intensity plus two standard deviations, using the corresponding lateral condyles as controls. The association between the KOOS scales and BML scores/volume was evaluated using Spearman's correlation coefficient. Multivariate linear regression analyses for post-operative KOOS scales were performed using the tibial BML volume as one of the four independent variables. RESULTS: The final analysis included 40 MOWHTO cases. Two qualitative BML scores correlated only with pre-operative KOOS sports. Femoral and tibial BML volumes were correlated with post-operative KOOS QOL (ρ = 0.40, p = 0.01) and sports (ρ = 0.36, p = 0.02), respectively. Tibial BML volume was significantly correlated with all five delta KOOS scales (ρ = 0.39-0.51, p = 0.01-0.001), however, femoral BML volume was only correlated with delta KOOS QOL (ρ = 0.41, p = 0.01). In multivariate analyses, tibial BML volume was a significant positive predictor for every post-operative KOOS scale, while post-operative % mechanical axis was also a positive significant variable, except post-operative KOOS pain. CONCLUSION: Tibial BML volume was positively correlated with one post-operative KOOS scale and all delta KOOS scales. A larger pre-operative tibial BML and appropriate alignment correction were associated with a better post-operative KOOS scales. Pre-operative large BML had no negative influence on post-operative clinical outcomes; hence, surgeons need not hesitate to perform MOWHTO in patients with large BMLs in the medial condyles. LEVEL OF EVIDENCE: Retrospective case series, Level IV.

Systemic chronic diseases coexist with and affect locomotive syndrome: The Nagahama Study.

OBJECTIVES: The concept of locomotive syndrome was proposed to highlight older adults who require nursing care services due to the malfunctioning of their locomotive organs. With the coming of a super-ageing society, there is a growing need to understand the relation between systemic chronic diseases and locomotive syndrome. METHODS: We analysed the second-visit dataset of the Nagahama Study. The association analysis was performed to identify the chronic diseases that were risk factors associated with the occurrence and the progression of locomotive syndrome in both the cross-sectional and longitudinal studies. RESULTS: Hypertension, stroke, coronary heart disease, rheumatoid arthritis, chronic renal failure, osteoporosis, anaemia, and gastroesophageal reflux disease were independently correlated with locomotive syndrome through the deterioration of body pain, social activity, and cognitive function in the cross-sectional study. Multiple chronic diseases had additive effects and significantly increased the risk of locomotive syndrome. In the longitudinal study, osteoporosis and kidney disease were significantly correlated with the worsening of the total GLFS-25 score. CONCLUSIONS: Locomotive syndrome coexisted with various systemic chronic diseases, especially cardiovascular diseases. Osteoporosis and kidney disease were significantly correlated with the progression of locomotive dysfunction. The management of various chronic diseases may be useful to prevent locomotive syndrome and vice versa.

Physical and financial impacts caused by the COVID-19 pandemic exacerbate knee pain: A longitudinal study of a large-scale general population.

OBJECTIVES: This study aimed to evaluate the changes in knee pain, a dominant cause of physical disability, following the coronavirus disease (COVID-19) pandemic, and to identify factors affecting the changes in knee pain. METHODS: We analysed the pre- and post-COVID-19 longitudinal data set of the Nagahama Study. Knee pain was assessed using the Knee Society Score (KSS). The estimated KSS from the age and sex using regression model in the pre- and post-COVID-19 data set was compared. Factors including the activity score, educational level, and various impacts of COVID-19 were analysed for correlation analyses with changes in KSS. RESULTS: Data collected from 6409 participants showed statistically significant differences in KSS, pre- (mean = 22.0; SD = 4.4) and post-COVID-19 (mean = 19.5; SD = 6.4). Low activity score (p = .008), low educational level (p < .001), and undesirable financial impact (p = .030) were independently associated with knee pain exacerbation. CONCLUSION: The harmful effects of the COVID-19 pandemic on knee pain were suggested. People should be encouraged to engage in physical activities, such as walking, despite the state of emergency. Furthermore, social support for economically disadvantaged groups may improve healthcare access, preventing the acute exacerbations of knee pain.

Association between quantitative lower limb arterial calcification and bilateral severe knee osteoarthritis.

OBJECTIVES: To investigate whether lower limb arterial calcification (LLAC) quantified using computed tomography (CT) was a risk factor for bilateral severe knee osteoarthritis (OA). METHODS: This cross-sectional study included patients who were scheduled for surgical treatment of primary varus knee OA. Knee OA was evaluated using the Kellgren-Lawrence (KL) classification, KL grades 3 and 4 were defined as severe OA. The LLAC score in the bilateral whole leg CT was quantitatively measured and categorized into low or high groups based on the median value. A modified Poisson regression model was used to examine the relationship between the categorized LLAC score and the presence of bilateral severe knee OA with adjustment for possible confounders. RESULTS: Of a total of 252 patients examined, multivariable modified Poisson regression analysis showed a significant association between higher LLAC score and the presence of bilateral severe knee OA (adjusted risk ratio = 1.28; 95% confidence interval [CI], 1.12-1.48; p < .001). A substantial interaction was observed between male sex and high LLAC (p for interaction = .03). CONCLUSION: LLAC was associated with bilateral severe knee OA, and the LLAC score may be a useful measurement to identify patients at risk of bilateral severe knee OA.

Soluble Lectin-like Oxidized Low-Density Lipoprotein Receptor 1 Predicts the Changes of Rheumatoid Factor Titers in Rheumatoid Arthritis.

OBJECTIVE: The aim of this longitudinal study was to examine the clinical significance of soluble lectin-like oxidized low-density lipoprotein receptor 1 (sLOX-1) in patients with rheumatoid arthritis. METHODS: We gathered demographic and clinical data for a large rheumatoid arthritis cohort at 3 time points. Blood samples were collected at each time point; the number of samples was 282 cases in 2012, 431 cases in 2013, and 500 cases in 2014. Plasma sLOX-1 was measured by enzyme-linked immunosorbent assay. Correlations between sLOX-1 and clinical data were analyzed. Predictive factors associated with changes in sLOX-1 and rheumatoid factor (RF) were analyzed by multivariate linear regression. RESULTS: Plasma sLOX-1 level was significantly correlated with RF titer and other clinical parameters. The longitudinal analyses showed that changes in sLOX-1 were significantly correlated with changes in RF titers and with those at baseline. Multivariate linear regression analysis revealed that changes in RF and baseline RF were predictive factors for changes in sLOX-1. Conversely, the changes in RF were significantly correlated with the changes in sLOX-1 in all years. A stepwise regression analysis showed that the change in sLOX-1 was a predictive factor for the change in RF. CONCLUSIONS: The change in sLOX-1 has predictive value for assessing the change in RF, indicating the usefulness of sLOX-1 in clinical practice.

Valgus position of the femoral component causes abnormal kinematics in the presence of medial looseness in total knee arthroplasty: a computer simulation model of TKA for valgus knee osteoarthritis.

PURPOSE: Total knee arthroplasty (TKA) for valgus knee osteoarthritis is challenging. Although overcorrection in TKA for valgus knee osteoarthritis is recommended, supportive data based on biomechanics have rarely been reported. The purpose of this study was to elucidate whether coronal rotation of the femoral compartment causes abnormal kinematics with or without medial looseness. METHODS: Multi- and single-radius posterior-stabilised TKA implants were utilised in a computer simulation. A total of 4 mm of slack were provided in the medial collateral ligament (MCL) with varus or valgus position of the femoral component to simulate the context of valgus knee osteoarthritis. Kinematics during gait and squatting activities were evaluated in each condition. RESULTS: During squatting, medial looseness and valgus replacement caused anterior translation of the medial femoral component in mid-flexion in the multi-radius implant. In the worst condition (7° valgus replacement with MCL looseness), there was rapid anterior translation in the multi-radius implant, and moderate anterior translation in the single-radius implant. Although medial looseness alone did not cause abnormal kinematics during gait, the worst condition exhibited an anterior translation to 4.9 mm in the multi-radius implant. This worst condition also exhibited a marked lift-off of 8.0 and 2.9 mm in the multi- and single-radius implants, respectively. Varus position caused little abnormal kinematics even with MCL looseness. CONCLUSION: Valgus, not varus position of the femoral component caused abnormal kinematics with MCL looseness. To avoid valgus position, the safety target angle of femoral component would be slight varus rather than neutral in valgus knee OA.

Intraoperative medial joint laxity in flexion decreases patient satisfaction after total knee arthroplasty.

INTRODUCTION: The relationship between postoperative tibiofemoral ligament balance and patient satisfaction in total knee arthroplasty (TKA) has been explored previously. However, the optimal intraoperative medial-lateral ligament balance during knee flexion in terms of postoperative patient satisfaction remains unknown. We evaluated the effect of intraoperative flexion instability on patient satisfaction after TKA. MATERIALS AND METHODS: This study consisted of 46 knees with varus osteoarthritis undergoing TKA. Medial-lateral component gaps at 0° knee extension and 90° flexion were measured intraoperatively using a knee balancer. Differences in postoperative patient outcomes at 3 weeks and 1 year were compared between medially tight knees in 90° flexion with a medial component gap of < 4 mm and medially loose knees in 90° flexion with a gap of ≥ 4 mm. Outcomes were measured using the 2011 Knee Society Scoring System (2011 KS). RESULTS: The median total 2011 KS score at 1 year postoperatively in the medially loose knees [median 97; interquartile range (IQR) 75-117] was significantly lower than that in the medially tight knees (median 128; IQR 104-139, P < 0.01), while preoperative and 3-week postoperative scores were similar. In addition, medial flexion gaps were not significantly associated with total 2011 KS scores before surgery or at 3 weeks postoperatively. However, at 1 year after surgery, medial component flexion gaps were negatively associated with the total 2011 KS score (R = - 0.42; P < 0.01) and the 2011 KS satisfaction subscale score (R = - 0.36; P = 0.01). CONCLUSIONS: Excessive intraoperative medial joint laxity of ≥ 4 mm at 90° flexion progressively decreased patient satisfaction for 1 year. Since intraoperative medial laxity in flexion is likely to interfere with functional recovery after TKA, medial stabilization during TKA is important throughout knee flexion. LEVEL OF EVIDENCE: Therapeutic study, Level III.

Morphology of the Proximal Tibia at Different Levels of Bone Resection in Japanese Knees.

The purpose was to measure the morphology of the proximal tibia at different levels for consideration of tibial tray design and placement. The morphology was analysed in 51 knees at 10, 15, 20, and 25 mm below the centre of the lateral tibial plateau. Surface rotation was measured by fitting an ellipse on the resection surface. The anteroposterior (AP), mediolateral (ML), medial AP (MAP) and lateral AP (LAP) dimensions were also measured. The resection surface showed internal rotation of 22.9° from the 10 mm level to the 25 mm level. More distally, the ML/AP and MAP/LAP ratios showed significant changes. Surgeons should pay attention to morphological changes for patients with gross tibial bone defects in primary and revision total knee arthroplasty.

Investigational regenerative medicine for non-traumatic osteonecrosis of the femoral head: a survey of registered clinical trials.

INTRODUCTION: Osteonecrosis of the femoral head (ONFH) is a refractory disease requiring joint replacement in young patients. Regenerative therapies have been developed. AREAS COVERED: This study surveyed clinical trials on regenerative medicine for ONFH. We extracted clinical trials on non-traumatic ONFH from the websites of five publicly available major registries (EuropeanUnion Clinical Trials Register ([EU-CTR],ClinicalTrials.gov, Chinese ClinicalTrial Registry [ChiCTR], University Hospital Medical InformationNetwork - Clinical Trial Registry [UMIN-CTR] and Australian New Zealand Clinical Trials Registry [ANZCTR]).The trials were classified into six categories based on purpose: surgical treatment, non-drug conservative treatment, conservative drug treatment, therapeutic strategy, diagnosis and pathogenesis, and regenerative therapy.) We extracted 169 clinical trials on ONFH. Of these, 37 were on regenerative medicine, including 29 on cell therapy. Surgical treatment was the most common treatment, followed by regenerative therapy.There were 9 clinical trials registered in the EU-CTR, with 5 on regenerative medicine; 79 trials registered on ClinicalTrials.gov, with 24 on regenerativemedicine; 54 trials registered in the ChiCTR, with 6 on regenerative medicine. EXPERT OPINION: The focus of the joint-preserving surgery has shifted to regenerative therapy based on using cell therapy in early-stage ONFH. The global standardisation of regenerative therapy is still ongoing.

Morphological Changes and Concentricity of the Hip Joint During Gradual Reduction in Infants with Late-Detected Developmental Dysplasia of the Hip: A Retrospective Study.

Background: The relationship between hip morphological changes and joint concentricity in infants with late-detected developmental dysplasia of the hip (DDH) treated with gradual reduction remains unclear. Therefore, we investigated hip morphological changes and concentricity in infants with late-detected unilateral DDH using magnetic resonance imaging (MRI) during gradual reduction. Methods: We enrolled 20 infants aged ≥ 12 months with unilateral DDH. Treatment comprised continuous traction, a hip-spica cast, and an abduction brace. MRI was performed before treatment, immediately after hip-spica cast placement, after cast removal, and at the end of the brace. We evaluated the acetabulum and femoral head morphology and joint concentricity. Results: The mean age was 25 months, and female sex and the left side were predominant. Before treatment, the acetabulum was small and shallow and the femoral head was spherically flat on the affected side. Immediately after the continuous traction, the affected acetabulum and femoral head were still smaller than the healthy/contralateral one. However, they improved to a deeper acetabulum and round femoral head. Intra-articular soft tissue (IAST) and femoral-acetabular distance (FAD) continuously decreased, indicating gradual improvement in joint concentricity. Deeper formation of the acetabulum and round shaping of the femoral head had occurred even in non-concentric reduction. Conclusion: The shape and concentricity of the hip joint improved after treatment; however, the acetabulum and femoral head remained small. The deeper acetabulum and round femoral head were observed the non-concentric reduction before the concentric reduction was achieved. The continuous decrease in IAST and FAD indicates effective post-traction therapy.

Excessive flexed position of the femoral component causes abnormal kinematics and joint contact/ ligament forces in total knee arthroplasty.

Poor clinical outcomes are reported in excessive flexion of the femoral component in total knee arthroplasty (TKA), but their mechanisms have not yet been elucidated. This study aimed to investigate the biomechanical effect of flexion of the femoral component. Cruciate-substituting (CS) and posterior-stabilised (PS) TKA were reproduced in a computer simulation. The femoral component was then flexed from 0° to 10° with anterior reference, keeping the implant size and the extension gap. Knee kinematics, joint contact, and ligament forces were evaluated in deep-knee-bend activity. When the femoral component was flexed 10° in CS TKA, paradoxical anterior translation of the medial compartment was observed at mid-flexion. The PS implant was best stabilised with a 4° flexion model in mid-flexion range. The medial compartment contact force and the medial collateral ligament (MCL) force increased with the flexion of the implant. There were no remarkable changes in the patellofemoral contact force or quadriceps in either implant. In conclusions, excessive flexion of the femoral component yielded abnormal kinematics and contact/ligament forces. Avoiding excessive flexion and maintaining mild flexion of the femoral component would provide better kinematics and biomechanical effects in CS and PS TKA.

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.

Static Mediolateral Tilt of the Joint Line after Total Knee Arthroplasty Does Not Reflect Dynamic Tilt during a Stair Ascent Activity.

The correlation between static and dynamic mediolateral (ML) tilts of the joint line in the coronal plane remains unknown after total knee arthroplasty (TKA). The purpose was to evaluate the ML tilt as measured by two-dimensional to three-dimensional registration during stair ascent in TKA patients, and to examine the correlation between the dynamic ML tilt and radiographic measurements of static indices. Thirty-two knees that underwent TKA using the mechanical alignment method were included. Continuous sagittal fluoroscopy was taken from before initial contact (IC) until after the toe-off (TO) phase during the stair ascent. The ML tilt of the tibial component relative to the ground was analyzed in terms of dynamic alignment using image-matching techniques, whereas static alignment was measured using standing long-leg radiographs. The correlation between static and dynamic ML tilts was evaluated. In the fluoroscopic analysis, the joint line was neutral (0.0 degree, standard deviation [SD] = 3.4 degrees) around IC phases, then was tilted valgus (5.5° valgus, SD = 2.6 degrees) in the mid-stance (MS) phase. After the TO phase, the joint line became almost neutral (0.4 degrees valgus, SD = 3.1 degrees). The dynamic ML tilt was significantly more varus during the IC phase and significantly more valgus in MS and TO phases than the static ML tilt (1.4 degrees valgus, SD = 2.0 degrees). No correlation was found between static and dynamic ML tilts in weight-bearing phases. During stair ascent, the static tilt had no correlation with the dynamic tilt in weight-bearing phases despite being in the same range. Static lower limb alignment does not reflect coronal alignment during motion. Further research should be conducted to determine whether the horizontal dynamic ML tilt can improve long-term durability and clinical outcomes after TKA.

Comparison of knee kinematics and ligament forces in single and multi-radius cruciate-retaining total knee arthroplasty: A computer simulation study.

BACKGROUND: The single-radius design in total knee arthroplasty has been designed to develop a more fixed flexion-extension axis without mid-flexion instability compared with the multi-radius design. It remains unclear whether differences between the multi-radius and single-radius designs can affect kinematics and collateral ligament forces. This study aimed to simulate knee kinematics and kinetics between single-radius and multi-radius models using a musculoskeletal computer model. METHODS: The single-radius and multi-radius femoral components were virtually implanted in a computer simulation using the same tibial insert. The effects of implant design on kinematics and medial collateral ligament forces during squatting and gait activities were analyzed. RESULTS: During squatting, the multi-radius model exhibited paradoxical anterior translation on both the medial and lateral flexion facet center where peak anterior translation was 2.4 mm for medial flexion facet center and 2.2 mm for the lateral flexion facet center, while the peak anterior translation of the single-radius model was less than 1 mm at early flexion. A rapid decrease in medial collateral ligament tension was observed in the early flexion phase in the multi-radius model, which occurred simultaneously with paradoxical anterior translation, whereas the relatively constant medial collateral ligament tension was observed in the single-radius model. During gait activity, the single-radius model exhibited a more posterior position than the multi-radius model. CONCLUSION: These suggest that abrupt changes in the medial collateral ligament force influence anterior sliding of the femur, and that the single-radius design is a reasonable choice for prevention of mid-flexion instability.

Improved genetic prediction of the risk of knee osteoarthritis using the risk factor-based polygenic score.

BACKGROUND: Polygenic risk score (PRS) analysis is used to predict disease risk. Although PRS has been shown to have great potential in improving clinical care, PRS accuracy assessment has been mainly focused on European ancestry. This study aimed to develop an accurate genetic risk score for knee osteoarthritis (OA) using a multi-population PRS and leveraging a multi-trait PRS in the Japanese population. METHODS: We calculated PRS using PRS-CS-auto, derived from genome-wide association study (GWAS) summary statistics for knee OA in the Japanese population (same ancestry) and multi-population. We further identified risk factor traits for which PRS could predict knee OA and subsequently developed an integrated PRS based on multi-trait analysis of GWAS (MTAG), including genetically correlated risk traits. PRS performance was evaluated in participants of the Nagahama cohort study who underwent radiographic evaluation of the knees (n = 3,279). PRSs were incorporated into knee OA integrated risk models along with clinical risk factors. RESULTS: A total of 2,852 genotyped individuals were included in the PRS analysis. The PRS based on Japanese knee OA GWAS was not associated with knee OA (p = 0.228). In contrast, PRS based on multi-population knee OA GWAS showed a significant association with knee OA (p = 6.7 × 10-5, odds ratio (OR) per standard deviation = 1.19), whereas PRS based on MTAG of multi-population knee OA, along with risk factor traits such as body mass index GWAS, displayed an even stronger association with knee OA (p = 5.4 × 10-7, OR = 1.24). Incorporating this PRS into traditional risk factors improved the predictive ability of knee OA (area under the curve, 74.4% to 74.7%; p = 0.029). CONCLUSIONS: This study showed that multi-trait PRS based on MTAG, combined with traditional risk factors, and using large sample size multi-population GWAS, significantly improved predictive accuracy for knee OA in the Japanese population, even when the sample size of GWAS of the same ancestry was small. To the best of our knowledge, this is the first study to show a statistically significant association between the PRS and knee OA in a non-European population. TRIAL REGISTRATION: No. C278.

Reduced angiogenesis and delayed endochondral ossification in CD163-/- mice highlights a role of M2 macrophages during bone fracture repair.

While recent studies showed that macrophages are critical for bone fracture healing, and lack of M2 macrophages have been implicated in models of delayed union, functional roles for specific M2 receptors have yet to be defined. Moreover, the M2 scavenger receptor CD163 has been identified as a target to inhibit sepsis following implant-associated osteomyelitis, but potential adverse effects on bone healing during blockage therapy have yet to be explored. Thus, we investigated fracture healing in C57BL/6 versus CD163-/- mice using a well-established closed, stabilized, mid-diaphyseal femur fracture model. While gross fracture healing in CD163-/- mice was similar to that of C57BL/6, plain radiographs revealed persistent fracture gaps in the mutant mice on Day 14, which resolved by Day 21. Consistently, 3D vascular micro-CT demonstrated delayed union on Day 21, with reduced bone volume (74%, 61%, and 49%) and vasculature (40%, 40%, and 18%) compared to C57BL/6 on Days 10, 14, and 21 postfracture, respectively (p < 0.01). Histology confirmed large amounts of persistent cartilage in CD163-/- versus C57BL/6 fracture callus on Days 7 and 10 that resolves over time, and immunohistochemistry demonstrated deficiencies in CD206+ M2 macrophages. Torsion testing of the fractures confirmed the delayed early union in CD163-/- femurs, which display decreased yield torque on Day 21, and a decreased rigidity with a commensurate increase in rotation at yield on Day 28 (p < 0.01). Collectively, these results demonstrate that CD163 is required for normal angiogenesis, callus formation, and bone remodeling during fracture healing, and raise potential concerns about CD163 blockade therapy.