Dovhan R.R. The effect of physical inactivity on the structure and mineral composition of bone tissue (experimental study) – Qualification scientific work in the form of a manuscript.
Dissertation for the degree of Doctor of Philosophy in the specialty 222 – Medicine (22 – Health Care). – State non-profit enterprise “Danylo Halytsky Lviv National Medical University”, Lviv, 2026.
The dissertation presents a theoretical generalization and a new solution to the current scientific problem, which consists in clarifying the patterns of dynamics of quantitative and qualitative characteristics of bone tissue of the femur and amplitude of movements in the hip joint against the background of prolonged experimental immobilization hypodynamia and after its completion.
The study was conducted on 65 white outbred sexually mature male rats aged 3.0-3.5 months and weighing 180.0-200.0 g. The animals were divided into experimental (60 rats) and control (5 intact rats) groups.
In the process of the study, the following research methods were used: modeling of prolonged forced immobilization; goniometric method; skeletonisation metod; radiographic/radiovisiographic method; atomic absorption spectral analysis method; method of statistical processing of digital data.
The results of the observation of animals that were in a state of forced hypodynamia showed a change in their behavior - the appearance of elements of aggression, changes in appetite, and a decrease in cleanliness. By the end of the fifth week of the experiment, the weight of the animals decreased to the minimum, amounting to 164.67±4.12 g, compared to the norm of 191.33±4.12 g. 2 weeks after the completion of 4-week immobilization, the weight of the animals increased to 197.07±5.01 g, exceeding the norm, 2 weeks after 6-week immobilization it was 180±3.42 g, remaining below the norm.
The results of the goniometric study showed that prolonged immobilization led to a decrease in the amplitude of passive movements in the hip joint, with the decrease in the amplitude of flexion movements being more pronounced than extension movements. It was found that the decrease in the amplitude of movements was proportional to the duration of immobilization. The maximum decrease in the amplitude of both movements was recorded after 6 weeks of forced immobilization, when the angle of flexion of the hind limb in the hip joint decreased by 51-57% compared to the norm, and the angle of extension decreased by 9-10%.
The obtained data showed that after prolonged bilateral immobilization, the amplitude of movements in the hip joints were asymmetric.
It has been established that the decrease in range of motion caused by immobilization lasting up to 6 weeks is reversible, with the duration of the period of recovery of volume and range of motion being proportional to the duration of immobilization.
According to the data of radiovisiographic research, when studying the bone density indicators of different areas of the femur, it was found that in intact animals the bone tissue of the greater trochanter has the highest density - 156.80±8.49 СUG, and the lowest - 131.28±6.25 СUG - of the femoral neck. The bone density in the femoral head area was 143.92±6.06 СUG, in the proximal diaphysis area – 136.32±7.53 СUG.
It was found that in the areas of the head, neck, and greater trochanter of the femur during 6 weeks of immobilization, bone density indicators were lower than normal and reached a minimum value at the end of the 6th week of the experiment. The bone density index of the proximal femoral diaphysis during 5 weeks of immobilization was higher than in animals of the control group and only during the sixth week of the experiment did it drop to values below normal. After 6 weeks of forced immobilization, the bone density of the femoral head was 8.3% lower than normal, the neck was 4.6% lower, the greater trochanter was 6.8% lower, and the proximal diaphysis was 2.1%.
2 weeks after the end of the 4-week immobilization, bone density indicators increased, remaining lower than in intact animals in the greater trochanter area (- 2.3%), and exceeding the norm in the proximal diaphysis (+ 4.7%). The bone density of the femoral head and neck in animals of this experimental group remained below normal by 0.8% and 0.2%, respectively. 2 weeks after the end of the 6-week immobilization, bone density remained lower than in the control group in all studied areas: in the femoral head area – by 6.2%, the neck – by 3.2%, the greater trochanter – by 6.3%, and in the proximal femoral diaphysis – by 0.9%.
Radiologically, it was found that after 6 weeks of immobilization, signs of bone osteophyte growth were visualized in the hip joint area, and the bone tissue of the proximal part of the femur had signs of osteoporosis and osteosclerosis. The detected changes were also preserved on radiographs of the studied area in animals two weeks after the cancellation of the 6-week immobilization.
