A BIOMECHANICAL STUDY OF THE EFFECTS OF FLEXION ANGLE ON THE INDUCTION MECHANISM OF CERVICAL SPONDYLOSIS

Lesions in facet joints such as bone hyperplasia and degenerative changes in the intervertebral discs, can compress nerve roots and the spinal cord, leading to cervical spondylosis (CS). Lesions in these parts of the spine are commonly related to abnormal loads caused by bad posture of the cervical spine. This study aimed to understand the potential mechanical effects of load amplitude on cervical spine motion to provide a theoretical basis for the biomechanical causes of CS, and to provide a reference for preventing of the condition. In this study, a finite element model of the normal human cervical spine (C1-C7) was established and validated using an infrared motion capture system to analyze the effects of flexion angle on the stresses experienced by intervertebral discs, the anterior edge of the vertebral body, the pedicle, uncinate and facet joints. Our analysis indicated that the intervertebral disc load increased by at least 70% during the 20∘ to 45∘ flexion of the neck with 121% load increase in the vertebrae. In the intervertebral discs, the stress was largest at C4-C5, and the stress was moderate at C5-C6. These results are consistent with clinical CS prone site research. According to Wolff’s law, when bones are placed under large stresses, hyperplasia can result to allow adaptation to large loads. Increased cervical spine flexion angles caused the proliferation of bone in the above-mentioned parts of the spine and can accelerate accelerating the appearance of CS.

MATHEMATICAL MODELING OF CANCELLOUS BONE TISSUE ADAPTATION APPLIED TO THE HUMAN MAXILLODENTAL SYSTEM

The bone tissue in different parts of the skeleton conforms to Wolff’s law: it aims to become optimal for the loading which acts on the corresponding bone; the bone is remodelling by means of osteosynthesis and resorption mechanisms. The modern problems of biomechanics demand research on the history of formation of bone structures in the course of time at both physiological and pathological loadings. Ever changing loadings of different nature have influence on development and functioning of the trabecular bone tissue. The mandible is one of the most liable to external and internal changes bones. Very often one has to deal with pathological changes caused by incorrect loading of different regions of bone tissue due to dysfunction of a dentition, a temporomandibular joint and so on. For example, the Popov-Godon’s syndrome which connects with tooth loss is accompanied by pathological remodelling of the surrounding bone tissue. Thus, the mathematical modeling of the cancellous bone tissue behavior in the human maxillodental system is one of the most topical problems of biomechanics and medicine. Trabecular bone tissue is a heterogeneous, porous, anisotropic material. Heterogeneity of spongy structure can be described by methods of quantitative stereology. At the same time, structural features of the trabecular bone can be described by means of the fabric tensor. This is possible to implement if there is both a constitutive relation which connects the stress tensor, the fabric tensor, and the strain tensor, and kinetic equations which describe the evolution of the fabric tensor and bone density. An initial boundary value problem on the trabecular bone tissue remodelling is stated. The effective numerical algorithm allowing to solve the problem is developed. This algorithm is implemented as a complex of problem-oriented programs. Verification of the model and identification of its parameters are carried out. All numerical calculations are performed using the ANSYS software. Trabecular bone tissue evolution is demonstrated on the set of model examples when the stress–strain state is changed. The results demonstrate different character of influence of changes of loading conditions on process of structure formation which follows from Wolff’s law.

Stress Fractures of the Foot and Ankle in Athletes

Stress fractures of the foot and ankle are common injuries in athletes. Management differs considerably based on fracture location and predisposing factors. Repetitive loading of the foot and ankle in athletes should result in physiologic bone remodeling in accordance with Wolff’s law. However, when there is not sufficient time for complete healing to occur before additional loads are incurred, this process can instead lead to stress fracture. Assessment of the athlete’s training regimen and overall bone health is paramount to both the discovery and treatment of these injuries, although diagnosis is often delayed in the setting of normal-appearing initial radiographs. While most stress fractures of the foot or ankle can usually be treated nonoperatively with a period of activity modification, fractures in certain locations are considered “high risk” due to poor intrinsic healing and may warrant more proactive operative management.

Postawa dziecka w wieku przedszkolnym i wczesnoszkolnym

Developmental processes in ontogenesis are divided into consecutive processes. The thesis presents man’s ontogenesis according to A. Malinowski. Man’s posture changes with age and is characterized by certain features in every period. External factors have a great influence on the correct development of the posture: nutrition and physical factors, particularly, the type of strain. The following laws influence the growing organism: Kölker’s and Pomner’s law, Delpech-Wolff’s law and the principles of bone structure development according to P. Lesgartt. To facilitate the proper development of the child it is important to provide them with satisfactory exercise on a daily basis. The thesis does not discuss hereditary factors influencing child’s development. It discusses the development of healthy children who are not burdened with genetic factors. The knowledge of the correct posture of the child is constantly growing due to the work of scientist and therapists working with children. The evaluation of the correct posture depends on the child’s age, and requires the knowledge of human ontogenesis. The ontogenesis is the basis for every kind of therapy of faulty posture. Zukunft-Hubert’s therapy constitutes a good example; in a non-invasive way, it cures faulty feet even in the first year of life, which was treated only surgically before.