Annals of Biomedical Engineering最新文献

Rapid reconstruction of a curved defect model within the allocated surgery time is a critical aspect of intraoperative bioprinting for cranial defect treatment. However, current data acquisition and defect reconstruction methods often involve manual intervention, which is impractical for real-time intraoperative printing due to their intricate and time-intensive nature. To tackle this challenge, this study introduces an online acquisition approach and a real-time automatic reconstruction algorithm for intraoperative defect data. Initially, a surface preprocessing scanning technique is proposed to address bone surface reflections and complex noise from blood and cranial tissues in live defective skulls, ensuring the acquisition of reliable defect data. Subsequently, an integrated reconstruction algorithm is developed for the obtained defect data. This algorithm seamlessly incorporates various techniques, including range filtering-based point cloud denoising, defect edge detection, patch creation utilizing the boundary-center method, and defect surface optimization based on the harmonic function. These components enable the algorithm to autonomously achieve immediate defect surface reconstruction. Finally, the effectiveness of the integrated algorithm is demonstrated through its application in surgical procedures on live rat cranial defects and human cranial defect models, showcasing its feasibility, superior accuracy, and practicality compared to software-based reconstruction methods. The algorithm is user-friendly, catering to both medical professionals and non-professionals, and fulfills the requirements of clinical intraoperative cranial treatment.

Purpose: The 30-second Chair Sit-to-Stand Test (30 s CST) is widely used to assess lower-limb function and reflects complex motor coordination across neural systems. However, conventional scoring methods are often inconsistent and fail to capture variations in compensatory movement strategies or require invasive instrumentation. This study presents a smartphone-based system that automatically detects rising strategies across repeated CST cycles, providing an automated approach to extract cycle-level biomarkers of motor performance.

Methods: Thirty-five adults 10 younger, 20 older, and 5 with Parkinson's disease performed supervised 30-s CST trials while wearing a waist-mounted smartphone that recorded accelerometer and gyroscope data at 400 Hz. Cycle detection used amplitude-adaptive thresholds and dominant-frequency intervals for robust segmentation of CST cycles. Rising strategies were classified with rule-based method that uses trunk pitch dynamics and cycle duration. Agreement with video annotations was assessed using Intraclass Correlation Coefficients (ICC (2, 1)), Bland-Altman analysis, and macro F1 scores.

Results: The algorithm detected 660 CST cycles with 99% accuracy, and the average mean absolute error across participants was under 40 ms. Bland-Altman analysis showed negligible bias (- 0.012 s) and narrow limits of agreement (- 0.134 to 0.110 s). Strategy classification achieved macro F1 = 0.94. Flexion cycles were consistently longer than Momentum Transfer cycles (e.g., older adults: 2.63 vs. 1.45 s).

Conclusion: Automated CST analysis reveals movement signatures not captured by standard timing, offering a richer characterization of mobility patterns. While these findings demonstrate technical feasibility and highlight clinically relevant variations, their application for diagnostic or personalized rehabilitation purposes remains preliminary and requires validation in larger cohorts.

Purpose: Gait analyses are becoming increasingly relevant in digital medicine. For implementation in clinical practice, knowledge on differences between gait patterns of separate bone fracture types is required. The aim of this study was to compare longitudinal changes in gait of patients with proximal tibial, tibial shaft, and malleolar fractures, as well as nonunion.

Methods: Patients with a proximal tibial, tibial shaft, or malleolar fracture requiring surgery were prospectively enrolled in this longitudinal observational study. A healthy control group received one measurement. Optical motion capture was used to obtain spatiotemporal gait parameters and kinematics at 6 weeks, 3 months, and 6 months after surgery.

Results: In total, 73 patients (51.1 ± 16.9 years) and 43 controls (50.5 ± 17.7 years) were included. Only in malleolar fractures, all gait parameters had returned to normal after 6 months. Differences between fracture types at 6 weeks were found in step height (P = 0.01), knee range of motion (ROM, P < 0.001), and its asymmetry (P < 0.001). At 6 months, knee ROM was still lower in proximal tibial than tibial shaft and malleolar fractures (P = 0.04; 0.047). Tibial shaft fractures with and without nonunion differed in stance time (P = 0.007; 0.02) and its asymmetry (P = 0.007; 0.009) after 6 weeks and 6 months, but not at 3 months.

Conclusions: When monitoring fracture healing with motion capture, differences between fracture types and their timely appearance should be considered.

Trial registration: The study was prospectively registered in the German Clinical Trials Register DRKS00025108.

Thoracic endovascular aortic repair (TEVAR) is the standard of care for thoracic aortic pathologies, and its clinical success is related to the choice of stent-grafts (SGs). In this study, we conducted a comprehensive assessment of four commercial SGs (Valiant Captivia (VC), Terumo RelayPro Bare Stent (TBS), Cook Zenith Alpha (CZA), and Gore CTAG (CTAG)) to evaluate their mechanical performance in idealised and patient-specific conditions. High-fidelity finite element models were developed and validated against experimental tests and in vitro TEVAR procedures in 3D-printed rigid phantoms. The validation showed strong agreement between simulations and experiments (average error < 5%).Then, the SGs were virtually deployed in two aortic models to investigate device-wall interaction through geometrical and mechanical parameters. A greater metal density led to increased graft apposition (up to 94%) and increased radial forces (up to 354 N vs 116N). Conversely, sparser metal structures produced lower but more localised stress regions: maximum values of 0.25 MPa versus 0.49 MPa with denser metal. Higher stresses may contribute to improved device fixation and, when associated with greater apposition, may reduce the risk of endoleak. Nevertheless, high stresses could potentially induce long-term vascular remodelling.These results underscore the influence of SG's design on TEVAR outcomes and support the integration of validated computational simulations into pre-operative planning. The SG performance varied across patient anatomies: this study highlights the importance of personalized device selection and establishes a foundation for using in silico methods to optimize TEVAR strategies and mitigate procedural risks.

Purpose: To study the biomechanical effects of tilting titanium cages on internal fixation devices in TES surgery.

Methods: We used finite element analysis to simulate lumbar total en bloc spondylectomy (TES). Five models were constructed: (a) the intact model (L1-S); (b) the TES model after L3 removal; and the TES model with a titanium cage tilted at (c) 5°, (d) 10°, or (e) 15° in the sagittal plane. The sacrum was fixed to simulate the stress during lumbar flexion, extension, lateral bending to the left and right, and rotation to the left and right, and measured the biomechanical response of the internal fixation system.

Results: The range of motion (ROM) in segments L1-5 of the TES surgical model was significantly reduced compared to the intact model, with a decrease of 66.87-96.49%. The maximum von Mises stress (VMS) in the pedicle screw system occurred during left lateral bending, reaching 283.9 MPa, while the minimum VMS occurred during flexion, at 114.7 MPa; during rotation, the maximum endplate stress was observed at L2 and L4, with values of 30.8 MPa and 22.7 MPa, respectively. When comparing the tilted cage models c-e to the neutral cage model b , the ROM of the lumbar spine most notably increased during left and right rotations, with an increase of 166.5%-227.6%. The VMS in the pedicle screw-rod system significantly increased during rotation, with a peak value of 421.3 MPa, and the VMS in the titanium cage also showed a marked increase, with a maximum value of 733.5 MPa. The VMS of the lower endplate at L2 increased to a range of 21.6 MPa to 113.0 MPa, and the VMS of the upper endplate at L4 increased to a range of 12.0 MPa to 66.9 MPa.

Conclusion: After the titanium cage is tilted, the pedicle screw-rod system, the titanium cage, and the upper and lower endplates of the adjacent vertebrae all experience an increase in stress. This stress elevation is most critical during rotational movements. Although the stress values fluctuated across different tilt angles (5°, 10°, 15°), no consistent dose-response relationship was observed in this model. This suggests that the presence of sagittal tilt itself may be a more critical factor influencing stress than the exact degree of tilt within the 5°-15° range.

Growth plate injuries account for up to 30% of pediatric fractures, with a substantial number leading to complications such as bony bar formation that can impair longitudinal growth, resulting in limb length discrepancies, angular deformities, or premature growth arrest. Conventional treatments focus on surgical resection of the bone bridge and interpositional grafting, but these approaches often fail to restore the native architecture or biological function of the physis, and recurrence is common. Recent advances in regenerative medicine offer promising alternatives that move beyond mechanical barriers toward biologically active repair. This review examines the biology and pathophysiology of the growth plate, emphasizing the cellular and molecular mechanisms involved in pathological repair, including inflammation, fibrogenesis, osteogenesis, and remodeling. It highlights the roles of mesenchymal stem cells (MSCs), signaling pathways, and immune responses in regulating both normal and aberrant healing. Emerging strategies such as cell-based therapies, tissue engineering scaffolds, gene therapies, growth factor delivery, and exosome-based therapies are discussed for their potential to promote cartilage regeneration and prevent bone bridge formation. The review also addresses key translational challenges and future directions for advancing personalized regenerative therapies in orthopedic and pediatric practice. A comprehensive understanding of current and emerging regenerative strategies, along with the underlying healing mechanisms, is essential to guide the development of targeted therapies that restore growth plate function, minimize complications, and improve long-term outcomes in pediatric patients.

Purpose: Distal femoral osteotomy (DFO) is an effective surgical procedure to correct valgus knee deformities. However, in lateral opening-wedge DFO (LOW-DFO), medial hinge fracture is a common complication that can lead to instability, correction loss, and delayed healing. This study aims to develop and validate a finite element (FE) model to investigate the mechanical effect of a protective Kirschner wire (K-wire) inserted in the medial hinge on the risk of hinge fracture.

Methods: A 3D finite element model of the opening stage in LOW-DFO was developed based on a prior experimental study on 3D-printed femurs. Crack initiation and propagation leading to fracture were simulated using the extended finite element method (XFEM). Two scenarios were compared: one with a protective K-wire and one without. Characterization tests were performed to obtain the necessary mechanical properties.

Results: The model was validated against data from previous mechanical experiments. The results showed that, while the protective K-wire had minimal effect on the location or onset of crack initiation, it increased the hinge stiffness and stabilized crack propagation. Compared to the configuration without the wire, the K-wire reduced the severity of unstable crack growth, thereby limiting abrupt failure.

Conclusions: The use of a protective K-wire improves the mechanical stability of the medial hinge by moderating crack propagation without affecting the initiation threshold. This study highlights the importance of modeling crack propagation and not only initiation when evaluating fracture risk in DFO. The findings support the potential clinical benefit of K-wire insertion for preventing hinge-related complications.

Purpose: This study investigated the formation of fracture repair tissue in response to 2.5-25% strain magnitudes under immediate and delayed loading in a large animal model with monotonically increasing interfragmentary strain.

Methods: Experimental osteotomies were created in ten sheep and were instrumented with an active fixator that generated a gradient (2.5-25%) of interfragmentary strain across the osteotomy. Sheep were randomly assigned to an immediate-loading (from day 1 post-surgery) group or a delayed-loading (from day 22 post-surgery) group. Five weeks post-surgery, the tibiae were scanned using high-resolution computed tomography (CT). CT images were subsequently sliced at different strain levels. For each two-dimensional slice, we evaluated the area and density of fracture repair tissue within the osteotomy and the radial span of the periosteal tissue. Repeated-measures ANOVA tested the effects of strain magnitude and loading protocol on these parameters.

Results: The area and density of osteotomy repair tissue were highest at 2.5% of strain for both groups and significantly decreased when strain increased (p ≤ 0.015). In contrast, periosteal tissue span increased with strain (p < 0.001) and was significantly larger in the immediate-loading group (p < 0.01).

Conclusion: Our study demonstrates the combined effect of strain (2.5-25%) and the timing of loading on bone healing. We observed two strain-related healing responses: up to ~ 7.5% strain, callus formed between the cortices, while higher strain shifted calcified repair tissue toward external callus. In this experimental model, strains below 25% provided a potent healing environment when stimulation was applied during the early healing stage.

Purpose: The goal of this study was to quantify the effect of initial head posture on neck muscle activity and head/neck kinematics during rear impacts.

Methods: Twelve seated participants experienced rear impacts on a sled with their head in five initial driving postures: left shoulder check, left mirror check, neutral head-forward, rear-view mirror check, or looking at their front-seat passenger. Electromyographic activity in four neck muscles was recorded bilaterally with indwelling electrodes and normalized to maximum voluntary contraction (MVC) levels. Head and torso kinematics were measured.

Results: Pre-impact muscle activity increased in 6 of the 8 muscles for non-neutral postures compared to the neutral posture (Δ = 0.6-7.5% MVC). During impact, only the peak left multifidus activity significantly changed (Δ = - 12% MVC) during left mirror check compared to neutral posture. Compared to the neutral posture, we observed larger absolute head acceleration (Δ = 0.7-2.6 g) out of the sagittal plane for all non-neutral postures and smaller fore-aft head-torso displacement (Δ = 5.2-7.8 mm) in the left shoulder check and look-at-passenger postures, but only minimal changes in torso kinematics.

Conclusion: Despite minimal changes to peak neck muscle activity during impact, we observed widespread changes in the head kinematics in non-neutral postures. This work provides data to inform injury prevention methods and simulate drivers with non-neutral head postures in computational models.