ZANKO I. Primary arthroplasty of the shoulder joint in multifragmentary fractures of the proximal part of the humerus

The dissertation is devoted to solving the current scientific task of traumatology and orthopedics - to improve the functional results of treatment of patients with multifragmentary fractures of the proximal humerus by improving the technique of unipolar shoulder arthroplasty. To solve the problem, a clinical examination of 83 patients who underwent shoulder arthroplasty due to multifragmentary humerus fractures and their consequences was conducted. Control examinations of the examined patients with an assessment of the effectiveness of surgical treatment were carried out 3 and 12 months after the surgery using two scales, the Constant Shoulder Score and the ASES scale. The patients were divided into three groups according to the treatment methods: group 1 control: patients without tubercle displacement who were treated using traditional treatment methods (31 patients); group 2 control: patients with tubercle displacement who were treated using traditional treatment methods (32 patients: 10 patients – superior from the normal position, 6 patients – inferior from the normal position, 9 patients – anterior from the normal position, 7 patients – posterior from normal position); experimental group: patients with tubercle displacement who were treated using the developed treatment method (20 patients). The clinical study of 63 patients of the control group proved that the location of the tubercle affects the increase in function and the effectiveness of shoulder arthroplasty according to the modern CMS and ASES classifications. When performing shoulder arthroplasty, reinsertion of the tubercle should be done as accurately as possible at the point of its anatomical location. Displacement of the tubercle anteriorly or posteriorly from the norm statistically significantly (p ≤ 0.01) reduces the increase in the volume of movement, muscle strength of the shoulder girdle, and everyday activity of operated patients. Using the Solid Works software package, a simulated 3D model of the shoulder joint was constructed using anatomical and anthropometric data as close to real data as possible. The model consisted of the following elements: scapula, cartilage of the articular cavity with cartilaginous lip, humerus, cartilage of the humeral head, and muscles: m. supraspinatus, m.infraspinatus, m.subscapularis and m.teres min. To optimize and simplify the calculations, the muscles were replaced with standard ANSYS elements, setting the appropriate properties, namely the stiffness characteristic of springs. The 3D models of the shoulder joint were imported into ANSYS. Further calculations of the stress-strain state (SSS) of the model were carried out in the ANSYS software package using the finite element method (FEM). The physical properties of bone and cartilage tissue obtained from the literature were used in the calculations. At the next stage, the stress-strain state of the shoulder joint model was studied under conditions of humeral head arthroplasty. For this purpose, the physical properties of the humeral head were changed in the created model of the shoulder joint, without changing its geometry. The humerus was replaced with a steel endoprosthesis made of medical steel 12X18N10T with appropriate mechanical properties. The assessment of VAT was carried out on the elements of the model that make up the shoulder joint, namely on the cartilage and bone tissue of the glenoid cavity, as well as on the surface of the humeral head endoprosthesis, in the areas contact of articular surfaces. The analysis of stresses according to Misis and total displacements (Total Deformation) was carried out for the model as a whole, aas well as separately for the model elements relative to each other, for which additional coordinate axes were set relative to which the displacements in each of the planes were determined. Biomechanical studies were performed from 5 different positions of the humeral tuberosity. Biomechanical studies show that the highest stresses and deformation, which can lead to instability of the shoulder joint arthroplasty, are observed when the large tubercle is placed anteriorly and posteriorly from the normal position. Based on clinical and biomechanical studies and literature data, a scheme for the differentiated treatment of patients with multifragment fractures of the proximal humerus was developed. It was implemented in 20 patients of the research group. The effectiveness of the proposed treatment was tested by the Constant Shoulder Score and ASES scores 3 and 12 months after surgery. It was determined that the implementation of the proposed treatment increased the number of good and excellent treatment results by 23.8% on the ASES scale and 43.8% on the CMS scale. After rehabilitation measures (12 months later), the difference was 43.7% on the ASES scale and 43.8% on the CMS scale. The data obtained as a result of the study are statistically processed and reliable (p < 0.01).