## 3 Results
The arrows in the figure represent the applied loading directions in the finite element analysis. the titanium alloy (900-1100 MPa), demonstrating the plate's ability to manage high-stress concentrations without compromising its structural integrity. Moderate stress levels ranging from 4.63 MPa to 10.71 MPa were observed along the plate, confirming a uniform stress distribution that enhances its durability and reliability under load-bearing conditions. The overall performance of the system components was summarized in the comparative results of stress-strain state (SSS) calculations, presented in Table 2. The Table 2 highlights the derotation plate's maximum von Mises stress of 76 MPa, displacement of 0.08 mm, and a minimum safety factor of 3.63. These values confirm the plate's compatibility with the prosthesis and bone while ensuring satisfactory performance of the other components under physiological conditions. These findings underline the importance of advanced computational modeling in optimizing the implant design. The derotation plate's performance highlights its effectiveness in mitigating complications associated with subtrochanter shortening osteotomy, such as instability and excessive dislocations. Its ability to uniformly distribute stresses and maintain structural integrity ensures its suitability for clinical use in complex cases of hip dysplasia. This study validates the derotation plate as a reliable component of the prosthesis-femur system, offering significant potential for improving patient outcomes in orthopedic surgery. By addressing critical factors, such as the stress distribution, displacement control, and safety margins, this analysis paves the way for further experimental validation and clinical implementation of the system. The radiographs shown in Figure 7 illustrate the clinical application of the prosthesis-femur-derotation plate system in a patient with Crowe type IV dysplasia of the left hip joint. Before surgery (Figure 7a), the preoperative radiograph reveals severe anatomical \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Indictors** & **Plate** & **Bone** & **Endoprosthesis** \\ \hline Maximum equivalent von Mises stress, MPa & 76 & 167.2 & 122 \\ Maximum linear displacement, mm & 0.08 & 0.094 & 0.145 \\ Minimum safety factor & 3.63 & 1.24 & 2.26 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Comparative results of SSS calculations. Figure 6: von Mises stress on the derotation plate, ranging from 0 to 20 MPa. abnormalities characteristic of Crowe type IV dysplasia. The femoral head is dislocated superiorly, with a severely underdeveloped acetabulum. These structural deformities result in joint instability and impaired biomechanics, necessitating surgical intervention. Three months after surgery (Figure 7b), the postoperative radiograph demonstrates successful restoration of the hip joint anatomy following total hip arthroplasty with the use of a derotation plate. The endoprosthesis head is repositioned into the true acetabulum, and the prosthesis was securely fixed. The derotation plate provides additional stabilization of the femur, ensuring proper alignment and load distribution during the early postoperative period. The imaging confirms the absence of significant displacement or loosening, indicating satisfactory initial outcomes of the surgical procedure. The radiographs in Figure 7 provide visual evidence of the system's clinical efficacy in treating Crowe type IV dysplasia. The successful correction of hip joint deformities, combined with the biomechanical stability demonstrated in the finite element analysis, highlights the reliability of the prosthesis-femur-derotation plate system. These findings reinforce the system's potential to improve surgical outcomes and patient quality of life in complex hip dysplasia cases.