Hinge point emergence in mammalian spinal neurulation.

Neurulation is the process in early vertebrate embryonic development during which the neural plate folds to form the neural tube. Spinal neural tube folding in the posterior neuropore changes over time, first showing a median hinge point, then both the median hinge point and dorsolateral hinge points, followed by dorsolateral hinge points only. The biomechanical mechanism of hinge point formation in the mammalian neural tube is poorly understood. Here we employ a mechanical finite element model to study neural tube formation. The computational model mimics the mammalian neural tube using microscopy data from mouse and human embryos. While intrinsic curvature at the neural plate midline has been hypothesized to drive neural tube folding, intrinsic curvature was not sufficient for tube closure in our simulations. We achieved neural tube closure with an alternative model combining mesoderm expansion, nonneural ectoderm expansion, and neural plate adhesion to the notochord. Dorsolateral hinge points emerged in simulations with low mesoderm expansion and zippering. We propose that zippering provides the biomechanical force for dorsolateral hinge point formation in settings where the neural plate lateral sides extend above the mesoderm. Together, these results provide a perspective on the biomechanical and molecular mechanism of mammalian spinal neurulation.

Tuning spacer length improves the functionality of the nanobody-based VEGFR2 CAR T cell.

BACKGROUND: The chimeric antigen receptor-expressing T (CAR-T) cells for cancer immunotherapy have obtained considerable clinical importance. CAR T cells need an optimized intracellular signaling domain to get appropriately activated and also for the proper antigen recognition, the length and composition of the extracellular spacer are critical factors. RESULTS: We constructed two third-generation nanobody-based VEGFR2-CARs containing either IgG1 hinge-CH2-CH3 region or hinge-only as long or short extracellular spacers, respectively. Both CARs also contained intracellular activating domains of CD28, OX40, and CD3ζ. The T cells from healthy individuals were transduced efficiently with the two CARs, and showed increased secretion of IL-2 and IFN-γ cytokines, and also CD69 and CD25 activation markers along with cytolytic activity after encountering VEGFR2+ cells. The VEGFR2-CAR T cells harboring the long spacer showed higher cytokine release and CD69 and CD25 expression in addition to a more efficient cytolytic effect on VEGFR2+ target cells. CONCLUSIONS: The results demonstrated that the third-generation anti-VEGFR2 nanobody-based CAR T cell with a long spacer had a superior function and potentially could be a better candidate for solid tumor treatment.

The hinge-1 domain of Flna is not necessary for diverse physiological functions in mice.

INTRODUCTION: The filamins are cytoskeletal binding proteins that dynamically crosslink actin into orthogonal networks or bundle it into stress fibres. The domain structure of filamin proteins is very well characterised, with an N-terminal actin-binding region, followed by 24 immunoglobulin-like repeat units. The repeat domains are separated into distinct segments by two regions of low-complexity known as hinge-1 and hinge-2. The role of hinge-1 especially has been proposed to be essential for protein function as it provides flexibility to the otherwise rigid protein, and is a target for cleavage by calpain. Hinge-1 protects cells from otherwise destructive forces, and the products of calpain cleavage are involved in critical cellular signalling processes, such as survival during hypoxia. Pathogenic variants in FLNA encoding Filamin A, including those that remove the hinge-1 domain, cause a wide range of survivable developmental disorders. In contrast, complete loss of function of this gene is embryonic lethal in human and mouse. METHODS AND RESULTS: In this study, we show that removing filamin A hinge-1 from mouse (FlnaΔH1), while preserving its expression level leads to no obvious developmental phenotype. Detailed characterisation of the skeletons of FlnaΔH1 mice showed no skeletal phenotype reminiscent of that found in the FLNA-causing skeletal dysplasia. Furthermore, nuclear functions of FLNA are maintained with loss of Filamin A hinge-1. CONCLUSION: We conclude that hinge-1 is dispensable for filamin A protein function during development over the murine lifespan.

CD19 CAR T cells for B cell malignancies: a systematic review and meta-analysis focused on clinical impacts of CAR structural domains, manufacturing conditions, cellular product, doses, patient's age, and tumor types.

CD19-targeted chimeric antigen receptors (CAR) T cells are one of the most remarkable cellular therapies for managing B cell malignancies. However, long-term disease-free survival is still a challenge to overcome. Here, we evaluated the influence of different hinge, transmembrane (TM), and costimulatory CAR domains, as well as manufacturing conditions, cellular product type, doses, patient's age, and tumor types on the clinical outcomes of patients with B cell cancers treated with CD19 CAR T cells. The primary outcome was defined as the best complete response (BCR), and the secondary outcomes were the best objective response (BOR) and 12-month overall survival (OS). The covariates considered were the type of hinge, TM, and costimulatory domains in the CAR, CAR T cell manufacturing conditions, cell population transduced with the CAR, the number of CAR T cell infusions, amount of CAR T cells injected/Kg, CD19 CAR type (name), tumor type, and age. Fifty-six studies (3493 patients) were included in the systematic review and 46 (3421 patients) in the meta-analysis. The overall BCR rate was 56%, with 60% OS and 75% BOR. Younger patients displayed remarkably higher BCR prevalence without differences in OS. The presence of CD28 in the CAR's hinge, TM, and costimulatory domains improved all outcomes evaluated. Doses from one to 4.9 million cells/kg resulted in better clinical outcomes. Our data also suggest that regardless of whether patients have had high objective responses, they might have survival benefits from CD19 CAR T therapy. This meta-analysis is a critical hypothesis-generating instrument, capturing effects in the CD19 CAR T cells literature lacking randomized clinical trials and large observational studies.

Pathogenic FLNA variants affecting the hinge region of filamin A are associated with male survival.

Pathogenic variants in FLNA cause a diversity of X-linked developmental disorders associated with either preserved or diminished levels of filamin A protein and are conceptualized dichotomously as relating to underlying gain- or loss-of-function pathogenic mechanisms. Hemizygosity for germline deletions or truncating variants in FLNA is generally considered to result in embryonic lethality. Structurally, filamin A is composed of an N-terminal actin-binding region, followed by 24 immunoglobulin-like repeat units. The repeat domains are separated into distinct segments by two regions of low-complexity known as hinge-1 and hinge-2. Hinge-1 is proposed to confer flexibility to the otherwise rigid protein and is a target for cleavage by calpain with the resultant filamin fragments mediating crucial cellular signaling processes. Here, three families with pathogenic variants in FLNA that impair the function of hinge-1 in males are described, leading to distinct clinical phenotypes. One large in-frame deletion that includes the hinge leads to frontometaphyseal dysplasia in affected males and females, while two germline truncating variants located within the exon encoding hinge 1 result in phenotypes in males that are explained by exon skipping and under-expression of a transcript that deletes hinge-1 from the resultant protein. These three variants affecting hinge-1 indicate that this domain does not mediate cellular functions that, when deficientresult in embryonic lethality in males and that germline truncating variants in this region of FLNA can result in viable phenotypes in males.

In-stent restenosis caused by a reprotruding calcified nodule and stent fracture in the hinged coronary artery.

Calcified nodules (CNs) cause in-stent restenosis (ISR) frequently. Although reprotrusion of CNs through stent struts is one of the mechanisms of ISR, the process of this phenomenon has not been understood. Furthermore, little is known about stent fracture (SF) occurring at the site of CNs. We are presenting a case of an 82-year-old male who developed early ISR due to the combination of an in-stent CN and SF in the hinged right coronary artery. The process of progression of the in-stent CN was recorded sequentially with angiography and intravascular ultrasound (IVUS). IVUS from the fulcrum of hinge motion revealed the repetitive protruding movement of the CN into the stent lumen.

Cortex2vector: anatomical embedding of cortical folding patterns.

Current brain mapping methods highly depend on the regularity, or commonality, of anatomical structure, by forcing the same atlas to be matched to different brains. As a result, individualized structural information can be overlooked. Recently, we conceptualized a new type of cortical folding pattern called the 3-hinge gyrus (3HG), which is defined as the conjunction of gyri coming from three directions. Many studies have confirmed that 3HGs are not only widely existing on different brains, but also possess both common and individual patterns. In this work, we put further effort, based on the identified 3HGs, to establish the correspondences of individual 3HGs. We developed a learning-based embedding framework to encode individual cortical folding patterns into a group of anatomically meaningful embedding vectors (cortex2vector). Each 3HG can be represented as a combination of these embedding vectors via a set of individual specific combining coefficients. In this way, the regularity of folding pattern is encoded into the embedding vectors, while the individual variations are preserved by the multi-hop combination coefficients. Results show that the learned embeddings can simultaneously encode the commonality and individuality of cortical folding patterns, as well as robustly infer the complicated many-to-many anatomical correspondences among different brains.

Decompressive craniotomy in split-technique (DCST) for TBI in infants: introducing a new surgical technique to prevent long-term complications.

INTRODUCTION: Decompressive craniectomy (DC) is rarely required in infants. These youngest patients are vulnerable to blood loss, and cranial reconstruction can be challenging due to skull growth and bone flap resorption. On the other hand, infants have thin and flexible bone and osteogenic potential. MATERIAL AND METHODS: We propose a new technique called DCST, which makes use of these unique aspects by achieving decompression using the circumstance of the thin and flexible bone. We describe the surgical technique and the follow-up course over a period of 13 months. RESULTS AND CONCLUSION: In our study, DCST achieved adequate decompression and no  further repeated surgeries in accordance with decompressive craniectomy were needed afterwards.

Effectiveness of hinge craniotomy as an alternative to decompressive craniectomy for acute subdural hematoma.

BACKGROUND: Acute subdural hematoma (ASDH) is a life-threatening condition, and hematoma removal is necessary as a lifesaving procedure when the intracranial pressure is highly elevated. However, whether decompressive craniectomy (DC) or conventional craniotomy (CC) is adequate remains unclear. Hinge craniotomy (HC) is a technique that provides expansion potential for decompression while retaining the bone flap. At our institution, HC is the first-line operation instead of DC for traumatic ASDH, and we present the surgical outcomes. METHODS: From January 1, 2017, to December 31, 2022, 372 patients with traumatic ASDH were admitted to our institution, among whom 48 underwent hematoma evacuation during the acute phase. HC was performed in cases where brain swelling was observed intraoperatively. If brain swelling was not observed, CC was selected. DC was performed only when the brain was too swollen to allow replacement of the bone flap. We conducted a retrospective analysis of patient demographics, prognosis, and subsequent cranial procedures for each technique. RESULTS: Of the 48 patients, 2 underwent DC, 23 underwent HC, and 23 underwent CC. The overall mortality rate was 20.8% (10/48) at discharge and 30.0% (12/40) at 6 months. The in-hospital mortality rates for DC, HC, and CC were 100% (2/2), 21.7% (5/23), and 13.0% (3/23), respectively. Primary brain injury was the cause of death in five patients whose brainstem function was lost immediately after surgery. No fatalities were attributed to the progression of postoperative brain herniation. In only one case, the cerebral contusion worsened after the initial surgery, leading to brain herniation and necessitating secondary DC. CONCLUSIONS: The strategy of performing HC as the first-line operation for ASDH did not increase the mortality rate compared with past surgical reports and required secondary DC in only one case.

Hinge screw or no hinge stabilization provides decreased stability compared to hinge plate in a biomechanical evaluation of distal femoral derotational osteotomies.

PURPOSE: Derotational distal femoral osteotomy (DFO) is the causal treatment for patients with femoral torsional deformity. The fixation is achieved by a unilateral angle-stable plate. Delayed- or non-unions are one of the main risks of the procedure. An additional contralateral fixation may benefit the outcome. Therefore, we hypothesize that primary stability in DFO can be improved by an additional fixation with a hinge screw or an internal plate. METHODS: Derotational DFO was performed in 15 knees and fixed either with an angle-stable plate only (group 'None'), with an additional lateral screw (group 'Screw') or with an additional lateral plate (group 'Plate'). Biomechanical evaluation was carried out under axial loading of 150 N (partial weight bearing) and 800 N (full weight bearing), followed by internal and external rotation. After linear axial loading in step 1, a cyclic torsional load of 5 Nm was applied under constant axial load in step 2. In step 3, the specimens were unloaded. Micromovements between the distal and proximal parts of the osteotomy were recorded at each step for all specimens. RESULTS: In step 1, the extent of micromovements was highest in group 'None' and lowest in group 'Plate' without being significantly different. In step 2, group 'Plate' showed significantly higher stability, reflected by less rotation and lower micromovements. Increasing the axial load from 150 to 800 N at step 2 resulted in increased stability in all groups but only reached significance in group 'None'. CONCLUSION: An additional contralateral plate significantly increased stability in derotational DFO compared to the unilateral angle-stable plate only. Contrary, a contralateral hinge screw did not provide improved stability. STUDY DESIGN: Experimental study. LEVEL OF EVIDENCE: IV.

Can the Current Thresholds for Synovial Cell Count and Neutrophil Percentage to Diagnose Prosthetic Joint Infection be Applied to Metal-on-Metal Rotating Hinge Total Knee Arthroplasty?

BACKGROUND: Synovial leukocyte count analysis is an important tool in the diagnosis of PJI. However, results can be poor if metallosis is present. The issue of metallosis was established for some rotating hinge knee arthroplasty designs. METHODS: This was a retrospective single-center analysis that included 108 patients who had a single-design metal-on-metal rotating hinge knee arthroplasty who underwent revision surgery and had prior synovial fluid analysis performed. The diagnostic accuracy of leukocyte count and the percentage of polymorphonuclear neutrophiles (% PMN) were investigated. RESULTS: Patients who had a PJI had a higher median leukocyte count and % PMN compared to aseptic revisions (7,905/µL (interquartile range (IQR) 2,419 to 37,400) and 85% (IQR 70.3 to 93.8) versus 450 (IQR 167 to 1,215) and 46% (IQR 28.5 to 67.4%), P < .001). The respective areas under the curves were 0.916 (95% confidence interval 0.862 to 0.970) for leukocyte count and 0.821 (95% confidence interval 0.739 to 0.902) for % PMN. We calculated an optimal cut-off value of 1,200 leukocytes/µL (Sensitivity 94.5%/specificity 75.5%) and 63% PMN (Sensitivity 85.5%/specificity 73.6%) to define PJI. Established thresholds were less sensitive, but more specific. The "infection likely" scenario of the European Bone and Joint Infection Society (EBJIS) definition was closest to the calculated thresholds. CONCLUSION: Currently used thresholds for leukocyte cell count and %PMN to define PJI were less sensitive and specific in the diagnosis of PJI in metal-on-metal RHK knees. Surgeons must consider lower cut-off values when evaluating such implants for PJI.

Tips and Tricks to Save You During Revision Total Knee Arthroplasty.

The number of revision total knee arthroplasties (TKAs) performed annually continues to rise. This article is a summary of a symposium on revision TKAs presented at the 2023 American Association of Hip and Knee Surgeons annual meeting. It will provide an overview of the surgical tips and tricks for exposure and component removal, use of metaphyseal fixation and stems to manage bone loss and optimize fixation, constraint in TKA, as well as how to manage extensor mechanism disruptions with a synthetic mesh reconstruction. LEVEL OF EVIDENCE: V.

High Rates of Early Septic Failure, but Low Rates of Aseptic Loosening After Revision Total Knee Arthroplasty With Contemporary Rotating-Hinge Prostheses.

BACKGROUND: The purpose of this study was to determine implant survivorship and functional outcomes for revision total knee arthroplasty (rTKA) with contemporary rotating-hinge knee implants. METHODS: A retrospective review identified 115 rTKAs using contemporary rotating-hinge implants from 2014 to 2018 for the treatment of instability (34, 30%), reimplantation after periprosthetic joint infection (PJI) (33, 29%), aseptic loosening (25, 22%), arthrofibrosis (14, 12%), periprosthetic fracture (4, 3%), osteolysis (4, 3%), and femoral component fracture (1, 1%). There were 70 women (61%), and the mean age was 67 years (range, 27 to 94). The mean follow-up was 3 years (range, 2 to 6). Kaplan-Meier analysis and Cox proportional hazard models estimated survivorship. RESULTS: The re-revision rate was 20% (23 of 115) at an average of 18 months postoperatively. Re-revision indications included PJI (n = 14), aseptic loosening (n = 4), arthrofibrosis (n = 2), instability/malalignment (n = 1), femoral stem fracture (n = 1), and hinge mechanism disruption (n = 1). At 2 and 5 years, survivorship free from all-cause re-revision was 86 and 64%, and survivorship free from re-revision for aseptic loosening was 100 and 87%, respectively. Use of a rotating-hinge implant in reimplantation after PJI was a risk factor for subsequent re-revision (hazard ratio = 2.4, P = 0.046). On a radiographic review of unrevised rotating-hinges, there were major radiolucent lines around 2 femoral and 5 tibial components. The mean Knee Injury and Osteoarthritis Outcomes Score for Joint Replacement increased from 43 preoperatively to 60 at 1 year (P < 0.001). CONCLUSIONS: In patients treated with a rotating-hinge implant for rTKA, there were relatively poor 2-year (86%) and 5-year (64%) survivorship free from all-cause re-revision, most commonly due to PJI. Midterm survivorship free from re-revision for aseptic loosening was modest (87%). There should be a goal to mitigate complications in complex rTKAs with rotating-hinge implants, namely PJI.

Outcomes of Metaphyseal Cones and Stem Fixation Following Rotating Hinge in Complex Primary and Revision Total Knee Arthroplasty.

BACKGROUND: Although hinged prostheses have been used successfully in complex revision total knee arthroplasty (TKA), concerns exist regarding early failure due to aseptic loosening and other mechanical complications. The use of metaphyseal cones and hybrid cement fixation have been studied in unlinked constrained primary or revision TKA, but their impact on the survivorship of hinged prostheses has yet to be investigated. METHODS: We identified a consecutive series of 164 hinged prostheses and collected data on demographics, indications, complications, and re-revisions in patients who had fully cemented versus hybrid stems, with and without metaphyseal cones. A multivariate analysis was performed to identify independent variables associated with re-revision as the primary end point. RESULTS: In total, 84 patients (51.2%) had fully cemented stems, and 80 patients (48.8%) had hybrid stems. Cones were used in 73 patients (44.5%). At a mean follow-up of 3.4 ± 2.2 years, 42 patients underwent re-revision (25.8%), most commonly for infection (12.2%), followed by loosening (6.7%) and periprosthetic fracture (3.7%). Patients who had fully cemented stems had lower re-revision rates than hybrid fixation constructs (19 versus 26%, P = .043). Using multivariable regression, a construct with hybrid fixation with cones (odds ratio = 2.39; P = .037) was an independent risk factor for failure. Utilization of cones alone did not have an effect on re-revision rates at 3.4-year follow-up. CONCLUSIONS: While we found no difference with the use of cones, patients undergoing revision TKA with a hinge prosthesis and fully cemented stems had better overall survivorship than hybrid stems.

Use of Hinged Implants for Multistage Revision Knee Arthroplasty for Severe Periprosthetic Joint Infection: Remission Rate and Outcomes After a Minimum Follow-Up of 5 Years.

BACKGROUND: In severe periprosthetic joint infection after total knee arthroplasty (TKA), multistage procedures are indicated for ongoing signs of infection after implant removal during the spacer interval of an intended 2-stage exchange. In these cases, several additional debridement and spacer exchange surgeries may be necessary. Herein, we analyzed the complications, remission rates, and functional outcomes after multistage revision arthroplasty using hinged TKAs. METHODS: Patients (n = 79) treated with multistage revision arthroplasty after chronic periprosthetic joint infection of the knee were included (2010 to 2018). During the prosthesis-free interval, a static spacer containing antibiotic-loaded bone cement was implanted. The mean number of surgeries, including implant removal and revision arthroplasty, was 3.8 (range, 3 to 8). The mean duration from implant removal to revision arthroplasty was 83 days (range, 49 to 318). Complications, remission, and mortality were analyzed after a minimum follow-up of 5 years. Outcomes were assessed based on the Knee Society Score (KSS) and the Western Ontario McMasters University Osteoarthritis Index. RESULTS: During follow-up, 24 (30.4%) patients underwent revision surgery, with a mean time to surgical revision of 99 weeks (range, 1 to 261). After follow-up, the infection-free remission rate and overall mortality were 87.3 and 11.4%, respectively. The mean KSS was 74.3 (range, 24 to 99), the KSS Function Score was 60.8 (range, 5 to 100), and the Western Ontario McMasters University Osteoarthritis Index 30.2 (range, 5 to 83). CONCLUSIONS: In difficult-to-treat cases, multistage revision arthroplasty showed high remission rates and low mortality after a follow-up of 5 years. The overall revision rate was comparably high, accounting for early and late reinfections most of the time. In cases of implant survival, functional outcomes comparable to those of revision hinge TKA reported in the literature can be achieved. Therefore, multistage procedures with additional debridement steps should be performed in cases of ongoing infections in intended 2-stage procedures.

Rotating-Hinge Revision Total Knee Arthroplasty Provides Greater Arc of Motion Gains for Patients Who Have Severe Arthrofibrosis.

INTRODUCTION: Arthrofibrosis is a common postoperative total knee arthroplasty (TKA) complication that results in limited range of motion (ROM). There is limited literature on outcomes after revision TKA (rTKA) for arthrofibrosis based on preoperative ROM restriction. The aims of this study were to: (1) examine ROM trajectory after rTKA for arthrofibrosis patients who have severe versus non-severe limitations; (2) compare ROM gains and final arc of motion (AOM) between severe and non-severe cohorts; (2a) compare ROM gain in a severe cohort treated with a rotating hinge (RH) versus a non-rotating hinge (non-RH) construct; and (3) assess the impact of arthrofibrosis severity on patient-reported outcome measures (PROMs). METHODS: Patients were divided into 2 groups: Group A had preoperative ROM < 70o (severe), and Group B had preoperative ROM > 70o (non-severe). Patients were assessed clinically using AOM gain, absolute ROM, Knee injury and Osteoarthritis Outcomes Score for Joint Replacement (KOOS, JR), Lower Extremity Activity Scale (LEAS), and pain scores. Postoperative gains in AOM were compared between both groups. RESULTS: A total of 56 rTKAs (Group A (severe): n = 36, Group B (non-severe): n = 20) were performed for patients who have postoperative fibrosis. Group B had better ROM at the one-year timepoint (Group B: 95.9 ± 22.5 versus Group A: 83.2 ± 25.7). Group A had significantly better improvement in absolute AOM than Group B (31.1 ± 20.9 versus 11.4 ± 25.0, P < 0.01). The RH group demonstrated significantly better absolute AOM gain than the non-RH group (41.3 ± 19.4 versus 18.3 ± 15.2, P < 0.001). However, there were no significant differences in PROMs between Groups A and B or between RH and NRH groups at the final follow-up. DISCUSSION: Final ROM achieved between severe and non-severe arthrofibrosis groups were similar, and patients who have severe arthrofibrosis can expect greater absolute ROM gains and similar functional outcomes than non-severe arthrofibrosis patients. The RH rTKAs provided greater AOM gains for patients who have severe arthrofibrosis, with equivalent functional outcomes to non-RH implants. For severe arthrofibrosis patients, RH designs provided twice the overall ROM gain, however, longer follow-up is necessary to determine whether RH designs have inferior overall implant survivorship.

A Low-Frequency Fiber Bragg Grating Acceleration Sensor Based on Spring Support and Symmetric Compensation Structure with Flexible Hinges.

To measure vibration signals, a low-frequency fiber Bragg grating (FBG) acceleration sensor featuring a flexible hinge with a spring support and symmetric compensation structure has been designed. Based on the mechanical model of the sensor's structure, the expressions for sensitivity and resonant frequency of the sensor are derived. The structural parameters of the sensor are optimized, and a simulation analysis is conducted using ANSYS 19.2 software. According to the results of simulation analysis and size optimization, the sensor prototype is constructed. Subsequently, its amplitude-frequency response, sensitivity, and temperature characteristics are investigated through vibration experiments. The experimental results show that the resonant frequency of the sensor is 73 Hz, the operating frequency range is 0~60 Hz, and the sensitivity measures 24.24 pm/g. This design meets the requirements for measuring vibration signals at low frequencies.

Stiffness-Based Evaluation of Hinge Joints in Prefabricated Assembled Multi-Girder Bridges under Operational Conditions.

Presently, the prevailing approaches to assessing hinge joint damage predominantly rely on predefined damage indicators or updating finite element models (FEMs). However, these methods possess certain limitations. The damage indicator method requires high-quality monitoring data and demonstrates variable sensitivities of distinct indicators to damage. On the other hand, the FEM approach mandates a convoluted FEM update procedure. Hinge joint damage represents a major kind of defect in prefabricated assembled multi-girder bridges (AMGBs). Therefore, effective damage detection methods are imperative to identify the damage state of hinge joints. To this end, a stiffness-based method for the performance evaluation of hinge joints of AMGBs is proposed in this paper. The proposed method estimates hinge joint stiffness by solving the characteristic equations of the multi-beam system. In addition, this study introduces a method for determining baseline joint stiffness using design data and FEM. Subsequently, a comprehensive evaluation framework for hinge joints is formulated, coupling a finite element model with the baseline stiffness, thereby introducing a damage indicator rooted in stiffness ratios. To verify the effectiveness of the proposed method, strain and displacement correlations are analyzed using actual bridge monitoring data, and articulation joint stiffness is identified. The results underscore the capability of the proposed method to accurately pinpoint the location and extent of hinge joint damage.

Osseous factors influencing distal tibial rotation in biplane medial opening wedge high tibial osteotomy.

PURPOSE: There is a lack of studies investigating the distal tibial rotation (DTR) during medial opening wedge high tibial osteotomy (MOWHTO). This study was designed to evaluate osseous factors influencing DTR in patients who underwent biplane MOWHTO. METHODS: A total of 106 knee joints in 69 patients who underwent surgery for varus malalignment of knee were reviewed. Based on several software, standard and actual hinge positions were defined in pre-operative and post-operative CT data. Pearson's correlation and Spearman's correlation analysis were performed with DTR change as the dependent variable. Independent variables included angles between standard and actual hinge in the sagittal (ASAHS) and axial (ASAHA) planes, pre-operative and post-operative medial proximal tibial angle, opening width (OW), tuberosity osteotomy angle, flange angle (FA), gap ratio, and hinge fracture. RESULTS: The distal tibia rotated approximately 0.35° internally. Pearson's and Spearman's correlation analysis showed that DTR change was associated with ASAHS, OW, and FA. Larger OW and FA resulted in higher external rotation angles. CONCLUSIONS: DTR change was significantly associated with ASAHS, followed by OW and FA rather than ASAHA if only considering osseous factors in biplane MOWHTO. The distal tibia tended to rotate externally when the actual hinge was inclined posteriorly to the standard hinge in the sagittal planes, but rotate externally or internally when the actual hinge was inclined anteriorly.

Outcomes of rotating versus pure hinge knee arthroplasty in the setting of one-stage exchange for periprosthetic joint infection.

PURPOSE: Rotating or pure hinge knee prostheses are often used in case of periprosthetic joint infection (PJI). Five-year survival data of rotating hinge implants ranging from 52 to 90%, whereas pure hinge data are sparse. This study describes the results of both hinge knee prostheses after one-stage septic exchange. METHODS: One hundred sixty-seven one-stage septic exchanges of a primary unconstrained total knee arthroplasty (TKA) to a cemented hinge prosthesis (117 rotating and 50 pure hinge TKAs) performed between 2008 and 2017 were retrospectively reviewed. Exclusion criteria were stem extensions or augments used in primary TKA, history of extensor mechanism reconstruction, and a follow-up less than two years after surgery. Rates of reinfection, mechanical failures, and all-cause revision-free survival data were documented. RESULTS: At five years, the all-cause revision-free survival was 77% (95% CI 69 to 82). Thirty-one patients (19%) had further revision for aseptic reasons. In the rotating hinge group, the mechanical failure rate was more than twice as high as in the pure hinge group (13% vs 6%), significantly influenced by higher body weight. At a mean follow-up of 6.7 years, 21 (13%) patients had a reinfection and underwent a further surgery. Reinfection rates did not differ between the two groups. CONCLUSION: The use of hinge TKA in the revision of PJI shows favourable five year infection-free and all-cause revision-free survival rates of 91% and 77%, respectively. Our study showed poorer results of the rotating hinge design. These results may help surgeons to choose proper implants in case of septic knee revision.