The aim of the study was to improve the results of treatment of patients with dysplastic coxarthrosis by developing, launching into production and practical usage a system of modular hip arthroplasty of national origin. In addition, the aim was to provide clinical and biomechanical substantiation of differentiated arthroplasty in patients with this pathology.
The comparison of the fixation stability of hip endoprosthesis components in conditions typical for dysplastic coxarthrosis, in the presence of femoral deformation, segmental and central defects of the acetabulum, the stress-strain state investigation with using mathematical modeling of the system «bone - structural elements of the hip arthroplasty».
There was carried out a comparative evaluation of two types of cementless cups, which are installed by pressing or screwing in the conditions of the preserved spherical shape of the acetabulum and the presence of segmental defects in the range from 30º to 90º, and central defects associated with medialization of the cup position.
It was found that in the conditions of the preserved spherical shape of the acetabulum, the indicators of pelvic bone tension of both pressed and screwed cups do not differ significantly from the indicators of a healthy joint. If exploring a segmental defect with an angle of 30º, the stress state of the bone tissue for both types of cups is comparable to the previous indicators, but there is a tendency to increase the mobility of the pressed cup. In the conditions of segmental defect 60º when using screwed cups there are increased local values and stress concentrator in bone tissue, which do not significantly affect the stability of the cup and the bearing capacity of the pelvis, but while using a pressed cup under these conditions it is not possible to obtain primary stability. In cases of medialization of the position of the screw cup, by deepening the bottom of the acetabulum, with the output of its bottom by 2.5 - 5 mm outside the Kohler line, their stress levels remain the same as when installing this type of cups in the acetabulum with a segmental defect 30º and 60º respectively. When mediating the position of the pressed cup outside the inner locking plate and the Kohler line, its total movement increases 2.4 times compared to the screw cup, with a high risk of instability and protrusion.
While researching the comparative assessment of the stability of fixation of the developed types of legs of the hip arthroplasty depending on the type of fixation and contact area of the leg of the endoprosthesis in the femur and studying the stress-strain state «bone - leg of endoprosthesis» it was found that in cases of diaphyseal fixation there is a concentration of stresses in the distal femur when using different types of legs that have a risk of stress shielding syndrome and endoprosthesis instability and in cases of metaphyseal and metadiaphyseal fixation using conical and shortened legs, the stresses are distributed evenly over the femur, which eliminates the excessive concentration of loads and prevents the risk of aseptic loosening of the endoprosthesis.
Taking into account the two-plane anatomical features of the hip joint, a system of modular hip joint endoprostheses with different variants of acetabular components and legs of the endoprosthesis has been developed, certified, and launched into industrial production. Taking into account the peculiarities of deformation and destruction of the hip joint, the algorithm of differentiated hip arthroplasty in the conditions of dysplastic coxarthrosis was substantiated
There were treated 322 patients with dysplastic coxarthrosis, who underwent hip arthroplasty in 394 cases. The cementless hip arthroplasty was performed in 375 (95.2%) cases, cement in 19 (4.8%), endoprosthesis for DC II-IV types according to Crowe was performed in 340 (86.3%) cases, including 72 (36.5%) bilateral and 68 cases as a result of reconstructive operations on the hip joint. Different types of bone autoplasty were performed in 312 (78.2%) cases, including in 136 cases the medialization of the position of the cup and cotyloplastik was performed.
The results of hip arthroplasty in 283 (87.9%) patients with dysplastic coxarthrosis in the period from 2 to 10 years were studied according to the method of W. Harris and showed - 144 (50.9%) excellent results; 108 (38.2 %) – good; 29 (10.2%) - satisfactory and - 2 (0.7%) unsatisfactory.
