Background: Complex bone plateau fractures have been treated with bilateral plate fixation, but previous research has overemphasized evaluating the effects of internal fixation design, plate position, and screw orientation on fracture fixation stability, neglecting the internal fixation system’s biomechanical properties in postoperative rehabilitation exercises. This study aimed to investigate the mechanical properties of tibial plateau fractures after internal fixation, explore the biomechanical mechanism of the interaction between internal fixation and bone, and make suggestions for early postoperative rehabilitation and postoperative weight-bearing rehabilitation.Methods: By establishing the postoperative tibia model, the standing, walking and running conditions were simulated under three axial loads of 500 N, 1000 N, and 1500 N. Accordingly, finite element analysis (FEA) was performed to analyze the model stiffness, displacement of fractured bone fragments, titanium alloy plate, screw stress distribution, and fatigue properties of the tibia and the internal fixation system under various conditions.Results: The stiffness of the model increased significantly after internal fixation. The anteromedial plate was the most stressed, followed by the posteromedial plate. The screws at the distal end of the lateral plate, the screws at the anteromedial plate platform and the screws at the distal end of the posteromedial plate are under greater stress, but at a safe stress level. The relative displacement of the two medial condylar fracture fragments varied from 0.002–0.072 mm. Fatigue damage does not occur in the internal fixation system. Fatigue injuries develop in the tibia when subjected to cyclic loading, especially when running.Conclusion: The results of this study indicate that the internal fixation system tolerates some of the body’s typical actions and may sustain all or part of the weight early in the postoperative period. In other words, early rehabilitative exercise is recommended, but avoid strenuous exercise such as running.

Early onset scoliosis (EOS) is emerging as a serious threat to children’s health and is the third largest threat to their health after myopia and obesity. At present, the growing rod technique (GRT), which allows patients to regain a well-balanced sagittal profile, is commonly considered as an invasive surgical procedure for the treatment of EOS. However, the risk of postoperative complications and instrumentation breakage remains high, which is mainly related to the choice of fixed mode. Several authors have studied primary stability and instrumentation loads, neglecting the mechanical transmission of the spinal long-segment model in different growth phases, which is fundamental to building a complete biomechanical environment. The present study aimed to investigate the kinematic and biomechanical properties that occur after GRT, across the long spinal structure and the posterior instrumentation, which are affected by unilateral or bilateral fixation. Accordingly, spinal segments (C6-S1) were loaded under flexion (Flex), extension (Ext), left lateral bending (LB), right lateral bending (RB), left torsion (LT), and right torsion (RT) using 11 established spinal models, which were from three growth phases. The stress distribution, spinal and intervertebral range of motion (ROM), counter torque of the vertebra, and bracing force on the rods were measured. The results showed that bilateral posterior fixation (BPF) is more stable than unilateral posterior fixation (UPF), at the expense of more compensations for the superior adjacent segment (SAS), especially when the superior fixed segment is closer to the head. Additionally, the bracing force of the instrumentation on the spine increases as the Cobb angle decreases. Accordingly, this biomechanical analysis provides theoretical suggestions for the selection of BPF or UPF and fixed segments in different growing phases.

Aims: Growth rods are the gold standard for treating early-onset scoliosis (EOS), but current treatments often fail to optimally promote spinal growth and require frequent distraction surgeries, leading to complications and significant burdens on patients.Methods: We designed a novel growth rod (NGR) with unidirectional sliding and external regulation capabilities. Using a 3D model, we simulated the implantation of traditional growth rod (TGR) and NGR, applying a 400 N compressive load and a 1 Nm moment to test stiffness. We assessed spinal joint range of motion and growth rod stress distribution, and calculated axial force, moment, and fatigue life.Results: The axial compressive and torsional stiffness of the NGR were higher than those of the TGR and the intact group. The Von Mises stress values of the NGR under all conditions were higher than those of the TGR. Additionally, the fatigue life of the NGR met basic daily living requirements. Overall, the NGR demonstrated superior stiffness and stress distribution, with stress primarily concentrated near the screw fixation points and distributed along the titanium rods.Conclusion: The NGR, based on a distraction implant, includes a unidirectional sliding component and a spring-driven component, providing dynamic correction functionality. Additionally, it features a novel non-invasive lengthening mechanism that reduces the risk of infection. Compared to the current market-leading EOS implants, it offers enhanced stability. The novel device can potentially improve clinical outcomes in the surgical treatment of EOS.Cite this article: Bone Joint Res 2025;14(9):747–759.

Background: Chronic obstructive pulmonary disease (COPD) is a heterogeneous disorder involving varying contributions from airway abnormalities and emphysematous destruction. However, structural airway alterations in patients with airflow limitation but minimal emphysema remain incompletely characterized. Quantitative CT (QCT)-based airway morphology analysis may capture additional aspects of airway geometry associated with airway-predominant structural patterns. Objectives: This study aimed to evaluate lobar airway inter-tapering abnormalities on quantitative CT in patients with non-emphysematous COPD (NE-COPD) and investigate whether incorporation of inter-tapering features improves discrimination within the studied cohort. Methods: This retrospective cross-sectional study included 173 participants who underwent inspiratory thin-section chest CT and post-bronchodilator pulmonary function testing between January 2023 and March 2025. NE-COPD was defined as airflow limitation with minimal emphysema quantified by low-attenuation area percentage below −950 HU (LAA%-950 < 5%). Automated airway segmentation and centerline-based analysis were used to quantify fourth-generation lobar inter-tapering indices. A clinical model incorporating age, sex, and smoking exposure was constructed. An imaging-augmented model was subsequently developed using LASSO-selected lobar inter-tapering features together with global airway branching complexity. Model performance was evaluated using receiver operating characteristic analysis, bootstrap validation, calibration assessment, decision curve analysis, and SHAP interpretation. Results: Among the 173 participants, 87 had NE-COPD and 86 were Non-COPD controls. Compared with Non-COPD controls, patients with NE-COPD demonstrated altered fourth-generation lobar inter-tapering patterns in multiple lobes. The clinical model achieved an area under the curve (AUC) of 0.717. After incorporation of quantitative airway features, the imaging-augmented model demonstrated improved discrimination, with an AUC of 0.851. Bootstrap validation demonstrated stable model performance. SHAP analysis indicated that four lobar fourth-generation inter-tapering indices accounted for a substantial proportion of feature contribution within the fitted model. Decision curve analysis suggested higher theoretical net benefit of the imaging-augmented model within the evaluated threshold probability range. Conclusion: Quantitative CT-derived lobar inter-tapering was associated with pulmonary function-defined non-emphysematous COPD. These findings suggest that lobar inter-tapering represents a candidate geometric CT descriptor for characterizing airway-predominant structural patterns. Further multicenter studies with external validation and integration of complementary quantitative CT descriptors are required to determine its broader clinical utility.