Vol. 20 No. 1 (2023)

Open Access

Article

Anatomical Feature Segmentation of Femur Point Cloud Based on Medical Semantics

Xiaozhong Chen

Molecular & Cellular Biomechanics, Vol.20, No.1, 20(1), 1-14 , 2023, DOI:

Abstract：

Feature segmentation is an essential phase for geometric modeling and shape processing in anatomical study of human skeleton and clinical digital treatment of orthopedics. Due to various degrees of freedom of bone surface, the existing segmentation algorithms can hardly meet specific medical need. To address this, a novel segmentation methodology for anatomical features of femur model based on medical semantics is put forward. First, anatomical reference objects (ARO) are created to represent typical characteristics of femur anatomy by 3D point fitting in combination with medical priori knowledge. Then, local point clouds between adjacent anatomies are selected according to the AROs to extract boundary feature point (BFP)s. Finally, the complete model of femur is divided into anatomical regions by executing the enhanced watershed algorithm guided with BFPs. Experimental results show that the proposed method has the advantages of automatic segmentation of femoral head, neck and other complex areas, and the segmentation results have better medical semantics. In addition, the slight modification of segmentation results can be achieved by adjusting a few threshold parameter values, which improves the convenience of modification for ordinary users.

Open Access

Article

Computational Fluid Dynamics Analysis of Upper Airway Changes after Protraction Headgear and Rapid Maxillary Expansion Treatment

Haoran Xu

Molecular & Cellular Biomechanics, Vol.20, No.1, 20(1), 15-22 , 2023, DOI:

Abstract：

Clinically, it is common for Class III patients with maxillary skeletal deficiency, which may result in a variety of adverse consequences. Protraction headgear and rapid maxillary expansion (PE) is an effective treatment, but its effect on upper airway hydrodynamics has not been reported. The main purpose of this study was to evaluate the changes of the flow in the upper airway after PE by computational fluid dynamics (CFD). The sample includes fifteen patients (6 males, 9 females, age 11.00 ± 1.00) and the paired T-test was used to analyze the differences between the measured data before and after treatment. The maximum flow velocity decreased from 8.42 ± 0.16 m/s to 6.98 ± 0.36 m/s ( p  < 0.05), and the maximum shear force decreased from 3.72 ± 1.48 Pa to 2.13 ± 0.18 Pa. The maximum negative pressure decreased from −101.78 ± 33.60 Pa to 58.15 ± 9.16 Pa, only the changes of velopharynx and glossopharynx were statistically significant; while the maximum resistance decreased from 140.88 ± 68.68 Pa/mL/s to 45.95 ± 22.96 Pa/mL/s. PE can effectively reduce the airflow resistance of the upper airway and the probability of airway collapse, thus improving the patient’s ventilation function.

Open Access

Article

Reliability of Foot Intrinsic Muscle Strength Testing and Correlation with Corresponding Muscle Morphology in Elderly Adults

Lulu Yin, Kun Dong, Zhangqi Lai, Lin Wang

Molecular & Cellular Biomechanics, Vol.20, No.1, 20(1), 23-33 , 2023, DOI:

Abstract：

Age-related loss of foot intrinsic muscle (FIM) strength may be associated with disability, falls, and inability to perform daily activities. Previous studies have determined the reliability of FIM strength testing and evaluated the relationship between FIM strength and corresponding muscle morphology in young adults. However, few studies have measured FIM strength in the older. Therefore, this study aimed to assess the intra- and inter-reliability of FIM strength tests and the relationship between FIM strength and FIM size in the older. A total of 61 participants aged 60–75 years were recruited, and 18 of them were selected randomly for the verification of FIM strength test reliability. A portable dynamometer was used in evaluating FIM strength, particularly the 1st (FT1), 2nd–3rd (FT2-3), and 2nd–5th (FT2-5) toes flexion, and doming. A portable musculoskeletal ultrasound device was used in measuring the cross-sectional area (CSA) and thickness of FIMs, namely, flexor digitorum brevis (FDB), abductor hallucis (AbH), flexor hallucis brevis, quadratus plantae (QP), and abductor digiti minimi (AbDM). Intra- and interclass correlation coefficients (ICCs) were used in evaluating the reliability of the FIM strength tests, and Pearson’s correlation coefficients were used in determining the relationship between FIM strength and FIM size. All FIM strength tests showed good to excellent intratester reliability (ICCs: 0.793–0.920). Doming, FT2-3, and FT2-5 tests exhibited good intertester reliability (ICCs: 0.809–0.861). Doming strength was only correlated positively significantly with the thickness of AbH ( r  = 0.257,  p  = 0.046), FT1 strength was correlated negatively with AbDM thickness ( r  = −0.375,  p  = 0.003), FT2-3 strength was significantly positively correlated with the CSA of FDB ( r  = 0.359,  p  = 0.004) and the thickness ( r  = 0.273,  p  = 0.033) and CSA ( r  = 0.287,  p  = 0.025) of QP. FT2-5 strength was positively correlated with the CSA of FDB ( r  = 0.297,  p  = 0.020) and the thickness ( r  = 0.258,  p  = 0.045) and CSA ( r  = 0.319,  p  = 0.012) of QP but negatively correlated with the thickness of AbDM ( r  = −0.296,  p  = 0.020). The correlation between FIM strength and FIM size was weak. The findings suggested that foot muscle size should be cautiously used as a surrogate in evaluating FIM strength in the older.

Open Access

Article

Effect of a Double Helical Spring Decompression Structure Backpack on the Lumbar Spine Biomechanics of School-Age Children: A Finite Element Study

Fengping Li, Dong Sun, Qiaolin Zhang, Hairong Chen, István Bíró, Zhiyi Zheng, Yaodong Gu

Molecular & Cellular Biomechanics, Vol.20, No.1, 20(1), 35-47 , 2023, DOI:

Abstract：

Background:  A children’s backpack is one of the important school supplies for school-age children. Long-term excessive weight can cause spinal deformity that cannot be reversed. This study compared a double helical spring decompression structure backpack (DHSB) with a traditional backpack (TB) to explore the optimization of decompression devices on upper body pressure. The finite element (FE) method was then used to explore the simulation of lumbar stress with different backpacks, in order to prove that DHSB can reduce the influence of backpack weight on lumbar vertebrae, avoid the occurrence of muscle discomfort and spinal deformity in children;  Methods:  18 male children subjects (age: 12.5 ± 0.6 years; height: 145.5 ± 1.9 cm; bodyweight: 40.8 ± 3.1 kg) ran with DHSB and TB at a speed of 3.3 ± 0.2 m/s. Flexible pressure sensors were used to measure the pressure on the shoulder, back, and waist during running. The pressure data was then inputted into the FE model to simulate the effect of carrying different backpacks on the stress of the lumbar intervertebral disc (IVD);  Result:  There was a significant difference in shoulder and waist peak pressure between the DHSB and TB during the running posture. At a speed of 3.3 ± 0.2 m/s, the peak pressure of the shoulder and waist decreased. After finite element analysis, it was found that carrying DHSB on the back could effectively reduce the intervertebral disc pressure between L4-5 and L5-S1 by 27.9% and 34.1%, respectively;  Conclusion:  DHSB can effectively reduce the pressure on the shoulder and waist when children are running and can reduce the influence of backpacks on children’s posture to a certain extent. By finite element analysis, it is found that carrying DHSB can effectively reduce the stress of the lumbar intervertebral disc, and the damage to lumbar vertebrae is lower than with a TB.