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To date, only 34 cases of primary pulmonary rhabdomyosarcoma (PPRMS) in the middle-aged and elderly population have been published. However, analyses of the clinicopathological characteristics and prognosis of PPRMS in this population have not been performed. A 75-year-old man visited our hospital because of abdominal pain and discomfort. His serum lactate dehydrogenase, neuron specific enolase, and progastrin-releasing peptide levels were elevated. Positron emission tomography-computed tomography revealed a lobulated mass of 7.6 × 5.5 cm 2 in the lower lobe of the left lung with abnormally high fluoro-2-deoxy-d-glucose metabolism. Histologically, the tumor cells were small with little cytoplasm, deep nuclear staining, and heavily stained nuclear chromatin. Immunohistochemically, the tumor cells were positive for desmin, MyoD1 myogenin, synaptophysin, and CD56. Cytogenetic analysis for FOXO1A translocation was negative. Finally, the patient was diagnosed with PPRMS. He received combined chemotherapy with vincristine 1 mg, actinomycin 0.4 mg, cyclophosphamide 0.8 mg; however, only one course of chemotherapy was completed, and the patient died 2 months after diagnosis. PPRMS in middle-aged and elderly people is a highly malignant soft tissue tumor with significant clinicopathological characteristics.

Objectives: To extend the quantitative prediction of the external shape of bone structure to the simulation of osteophyte formation on the edge of vertebral body., Methods: The high-order nonlinear equation of bone remodeling was used to control osteophyte formation process. The idea of topology optimization in engineering was imported to allow the outgrowth of osteophyte. Osteophyte on the edge of a vertebral body in its mid-sagittal plane was simulated numerically., Results: Osteophyte formation is an adaptive bone remodeling process in response to the progressive changes of mechanical environment, which were mainly caused by intervertebral disc degeneration., Conclusion: The numerical simulation in this paper extended the structural simulation based on the quantitative bone remodeling theory to bone morphological abnormity in orthopaedics, which can help to better understand the relationship between bone morphological abnormity and the mechanical environment.

The aim of this paper was to introduce the idea of topology optimization in engineering to the simulation of bone morphology. The external shape of bone structure was predicted with the quantitative bone functional adaptation theory. The high-order nonlinear equation of bone remodeling proposed by Zhu et al. (J. Biomech. 35(7)(2002)951) combining with the finite element method was adopted to a rectangular design domain, which occupies a larger space than the external shape of bone structure. It was at this point we imported the idea of topology optimization in engineering. The proximal femur was used here as an example, whose external shape and internal density distribution were simultaneously simulated quantitatively to validate that the external shape of bone structure could be successfully predicted in this way. Then the growth of vertebral body from young to old was simulated numerically in its coronal section to discuss the significance of the prediction of external shape. The study in this paper provides computational basis for further studies on osteophyte formation, osteoporosis, osteoarthritis, bone growth and even bone evolution, etc.

In this paper, we introduced a high-order non-linear equation of bone remodeling to combine with FEM by introducing two non-linearities, i.e. the remodeling coefficient B(t) and the order of non-linear remodeling equation. The influence of each non-linearity was tested based on its mechanical and physiological implications discussed. We use two finite element models to investigate the influences of non-linearities in this equation: a plate subjected to a ramp load, and a 2D model of the cross-section of a vertebra. By importing the idea of topology optimization in engineering, their external shapes and internal density distributions were simulated from unfixed configurations. To a certain extent, the high-order non-linear equation of bone remodeling we suggested here can control the remodeling processes of bones in different stages of growth or at different anatomic sites more effectively, and make it more consistent with physiological reality, i.e. express the remodeling characteristic that bone's best morphology is adapted to its mechanical environment. Furthermore, it is likely to describe the process of bone growth and evolution.