Mathematical Modeling and Biomechanical Analysis of a Derotation Plate for Treating Complex Hip Dysplasia

Abstract

Developmental dysplasia of the hip, particularly Crowe type IV, presents significant challenges in orthopedic surgery due to severe anatomical deformities and biomechanical instability. This study focuses on evaluating the biomechanical performance of a prosthesis–femur–derotation plate system designed to address these challenges. Using FEA, a comprehensive assessment of stress distribution, displacement, and safety factors was conducted under physiological loading conditions. The derotation plate was specifically engineered to stabilize the femur and restore the anatomical and biomechanical axis of the limb. Results demonstrated that the derotation plate effectively eliminated rotational and axial displacement, with a peak displacement of 0.08 mm, and maintained sufficient strength reserves, with a minimum safety factor of 3.63. The maximum von Mises stress in the plate was 76 MPa, significantly below the yield strength of the titanium alloy, ensuring long-term durability and reliability. The system as a whole exhibited favorable biomechanical properties, confirming its ability to manage high stress loads without the risk of material failure or instability. These findings underscore the potential of this novel system to improve surgical outcomes in complex cases of hip dysplasia. Future clinical trials will further validate its practical utility, providing valuable insights for advancing orthopedic implant design and patient care.

1. Introduction

DDH is a complex orthopedic condition characterized by a spectrum of anatomical abnormalities, including underdevelopment of the acetabulum, degeneration of the articular lip, changes in the neck-shaft angle, and anteversion of the proximal femur. These structural deformities are often accompanied by alterations in surrounding soft tissues, ligaments, and neurovascular structures, leading to functional impairment and long-term complications if untreated [1].

The global incidence of DDH demonstrates significant variability based on geographical, cultural, and environmental factors. In Sub-Saharan Africa, DDH is rare, with an incidence of 0.06 per 1000 live births, contrasting sharply with rates among Native American populations, where prevalence reaches 76.1 per 1000 live births. Similarly, in developed nations, the incidence rates differ: the United Kingdom reports 5 to 30 per 1000 live births, while Japan and the United States record 4 per 10,000 and 11.5 per 1000 live births, respectively [2,3,4,5]. These disparities underscore the influence of genetic predispositions, swaddling practices, and early screening protocols on the epidemiology of DDH.

The consequences of untreated or late-diagnosed DDH are severe, often culminating in dysplastic coxarthrosis, which severely compromises joint function, mobility, and overall quality of life. Long-term complications may include limb length discrepancies, chronic pain, and early-onset osteoarthritis, necessitating complex surgical interventions [6,7]. Early diagnosis and intervention are therefore critical to mitigating these outcomes. Various classification systems, such as those proposed by Crowe, Hartofilakidis, Eftekhar, and Kerboul, provide a framework for diagnosing and managing DDH. Among these, the Crowe classification is the most widely adopted, especially for addressing severe cases, like Crowe type IV dysplasia [8].

Previous research has explored femoral stem designs, the stress distribution, fixation methods, and the use of modular and custom implants to address the challenges of hip reconstruction [9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24]. Studies have highlighted the importance of prosthetic stability, acetabular defect resolution, and bone grafting in total hip arthroplasty (THA) for DDH. Advances in 3D printing, uncemented arthroplasty, and titanium-based implants have further optimized surgical outcomes by improving the implant fit and load distribution. Additionally, a high hip center of rotation of the femoral head positioning and the use of modular neck prostheses have been evaluated for their long-term efficacy in maintaining joint stability and restoring limb biomechanics [23,24,25,26,27,28,29,30,31,32].

Crowe type IV DDH is characterized by high-riding dislocated hips and severe acetabular dysplasia, presenting unique surgical challenges. THA is the treatment of choice for such complex cases, often requiring extensive soft tissue release to address longstanding contractures. Subtrochanteric shortening osteotomy (SSO) is frequently employed in these procedures to restore joint congruency and limb alignment [33,34]. This technique has proven to be effective in repositioning the femoral head within the true acetabulum without endangering the neurovascular structures. However, SSO is associated with risks, including nonunion at the osteotomy site, rotational and axial instability, and loosening of the femoral prosthesis, all of which necessitate the development of advanced fixation methods [35].

Modern fixation techniques, including the use of autogenous bone grafts, wire pins, and plates with screws, have been explored to address these complications. Biomechanical research highlights the superiority of plate and screw fixation, which not only accelerates osteotomy healing but also provides enhanced rotational and axial stability compared to traditional methods, such as cable fixation [36,37]. Recent innovations in implant materials have further contributed to improved outcomes. Titanium, for example, is increasingly favored for its biomechanical properties, including an excellent strength-to-weight ratio, corrosion resistance, and compatibility with biological tissues [38]. Titanium plates have demonstrated superior stress distribution and reduced failure rates, making them a compelling choice for complex orthopedic applications [39].

The growing focus on computational biomechanics has further revolutionized the field of orthopedic surgery. Finite element analysis (FEA) enables detailed modeling of the stress–strain behavior of complex systems, facilitating the optimization of implant design and performance under physiological loading conditions [40,41]. By leveraging these advanced techniques, researchers and clinicians can develop innovative solutions to address the challenges posed by conditions like Crowe type IV DDH [42].

This study hypothesizes that the integration of a derotation plate in primary cementless total hip arthroplasty significantly enhances biomechanical stability, eliminates rotational and axial displacement, and promotes osteotomy fusion. The novelty of this research lies in the development and biomechanical assessment of a custom-designed derotation plate, tailored to the anatomical and functional demands of patients with Crowe type IV DDH. By combining advanced computational modeling with experimental validation, this study aims to bridge the gap between theoretical research and clinical applications.

The primary objectives of this research are as follows:

• To design and manufacture a titanium derotation plate tailored to the anatomical and biomechanical demands of patients with Crowe type IV DDH;
• To evaluate the stress distribution, displacement, and safety factor of the derotation plate using finite element analysis;
• To compare the biomechanical performance of the derotation plate with conventional fixation methods, emphasizing its clinical relevance in reducing complications associated with subtrochanteric shortening osteotomy.

Through these efforts, this research seeks to advance the field of orthopedic biomechanics, providing clinicians with innovative tools and techniques to improve patient outcomes in complex lower-limb deformities.

2. Materials and Methods

2.1. Model Development

The advancement of implant design and surgical treatment methods remains a critical focus in modern orthopedics. A key objective is to create implants that closely replicate the anatomical shape and biomechanical properties of human bones. This approach ensures better functional integration and improved clinical outcomes. Among the materials considered for implant development, titanium has emerged as the optimal choice due to its superior mechanical properties, biocompatibility, and corrosion resistance. Mugnai et al. [39] demonstrated that titanium plates exhibit excellent strength under maximum load conditions compared to alternative materials, further supporting its selection for orthopedic applications [15]. Consequently, titanium was chosen for the design and development of the novel derotation plate used in this study.

The engineering team at D. Serikbayev East Kazakhstan Technical University modeled the derotation plate using the CT scans of patients diagnosed with Crowe type IV dysplastic coxarthrosis. The CT scan data were processed in DICOM format and imported into Materialise Mimics 25.0 software to generate detailed 3D anatomical models. Subsequently, a fragment of the femur was fabricated using a Designer XPRO 3D printer, employing fused deposition modeling (FDM) technology for layer-by-layer material deposition.

The femoral derotation plate was initially conceptualized using Computer-Aided Design (CAD) and Computer-Aided Manufacturing (CAM) tools within the SolidWorks platform. A prototype was then fabricated using Stereolithography (SLA) technology with a Formlabs Form 3 3D printer (Formlabs, Somerville, MA, USA). This preliminary model underwent a meticulous visual inspection to assess its design accuracy and anatomical compatibility with patient-specific femoral structures. Adjustments were incorporated into the design to optimize its fit, functionality, and biomechanical performance.

The derotation plate was specifically engineered to enhance biomechanical stability during total hip arthroplasty (THA) with subtrochanteric shortening osteotomy in patients with Crowe type IV dysplastic coxarthrosis. Its design focuses on several key principles. Firstly, the plate ensures rigid fixation of the osteotomy site, stabilizing the femoral fragments postoperatively and reducing the risk of nonunion. Secondly, the plate effectively prevents rotational and axial instability by incorporating angled side wings in both the proximal and distal regions, significantly limiting femoral fragment displacement. Additionally, unlike conventional plates that often interfere with the femoral prosthesis, this derotation plate features screw holes oriented in the sagittal plane, preventing intersections with the implanted femoral stem. The carefully selected screw angles (20°, 16°, 8°, and 4°) allow for optimal placement while maintaining strong and reliable fixation.

A critical aspect of the design is its role in minimizing complications by optimizing the load distribution and reducing the stress-shielding effect. This approach enhances postoperative healing and mitigates risks, such as implant instability and delayed bone consolidation. The plate dimensions (length: 92 mm, width: 18 mm, thickness: 3.5 mm) and the use of titanium alloy (BT-6) were carefully selected to balance strength and flexibility, thereby supporting effective osseointegration.

For final manufacturing, a titanium alloy (BT-6) was chosen due to its high strength-to-weight ratio, corrosion resistance, and durability, making it ideal for orthopedic applications. The alloy was precisely cut using an air plasma cutter to achieve the required dimensions. The machining process was meticulously programmed using MasterCAM 2018 (v20.0), ensuring sub-millimeter precision. The plate was then fabricated on a DMU50 (DMGMORI) universal CNC milling machine, which is widely recognized for its high precision in medical device production, guaranteeing consistency and reliability in the final product.

Quality assurance was an integral part of the manufacturing process. The finished femoral derotation plate underwent rigorous inspection using advanced measuring instruments, including calipers and TESA micrometers (HAHN + KOLB GmbH, Stuttgart, Germany). These evaluations ensured that the dimensional accuracy, structural integrity, and surface finish of the implant met predefined standards. The meticulous quality control process guaranteed that the manufactured plate adhered to clinical and biomechanical requirements for optimal patient outcomes.

This comprehensive approach to model development combines advanced imaging technologies, precision engineering, and rigorous quality assurance, laying the groundwork for the successful application of the derotation plate in clinical settings.

2.2. Mathematical Modeling

Mathematical modeling plays a critical role in understanding the SSS and mechanical behavior of complex, multicomponent systems with heterogeneous structures. The FEM is widely regarded as the most reliable and effective numerical approach for these analyses. FEM divides a 3D geometric model into discrete finite elements of simple shapes, which collectively form a continuous finite element mesh. The iterative nature of FEM ensures that solutions—such as stresses, deformations, and deformation rates—calculated at each step serve as the basis for subsequent computations, providing a dynamic and precise understanding of the system’s behavior under applied loads.

For this study, the FEM analysis was implemented using software platforms, such as KOMPAS-3D (APM FEM), Autodesk Inventor PRO, and SolidWorks. These tools were employed to construct and evaluate a detailed model of the biotechnical system, comprising the prosthesis, femur, and derotation plate. The physical and mechanical properties of the system components were sourced from established literature to ensure accurate simulations.

Table 1. Physical–mechanical parameters of the modeled systems.

Material	Elasticity Modulus (MPa)	Poisson Ratio
Cortical bone	15,000	0.3
Spongy bone	1000	0.3
Plate, prosthesis, screws (titanium)	110,000	0.3

presents the physical–mechanical parameters of the modeled system’s components. The properties included the elasticity modulus and Poisson ratio, which are critical for accurately representing the behavior of cortical bone, spongy bone, and titanium components under loads.

These parameters serve as the foundation for the finite element model, ensuring that the biomechanical properties of each material are accurately represented in the simulations.

To replicate physiological conditions, the main functional load was modeled as a vertical force (F1 = 1000 N) applied to the center of the femoral head (or prosthetic head). Additionally, a horizontal force (F2 = 200 N) was included to analyze rotational displacements. These forces were selected to simulate typical biomechanical stresses experienced by the hip joint during weight-bearing activities.

Using the finite element method, the stress–strain state and biomechanical behavior of the system—comprising the prosthesis, femur, and derotation plate—were evaluated under these loading conditions. The simulation provided insights into the load distribution, stress concentrations, and overall mechanical performance of the system.

In this study, a safety factor analysis was performed to assess the mechanical reliability of the prosthesis–femur–derotation plate system under physiological loading conditions. The safety factor (SF) was determined using the von Mises stress criterion, where the yield strength of each material was compared to the maximum stress observed in the finite element (FE) analysis.

The SF was calculated using the following Equation (1):

$$SF={\displaystyle \frac{{\sigma }_{yield}}{{\sigma }_{max}}}$$

(1)

The SF was calculated using the von Mises stress criterion, where ${\sigma }_{yield}$ represents the yield strength of the material and ${\sigma }_{max}$ denotes the maximum von Mises stress obtained in the simulation. For this study, the following yield strength values were used: titanium (plate, screws, prosthesis)—900 MPa, cortical bone—130 MPa, spongy bone—5 MPa. The SF distribution was mapped across the implant system to identify potential failure zones. Regions with SF > 1 indicate safe stress levels, whereas SF < 1 suggests areas at risk of mechanical failure under loading conditions. This analysis is essential to confirm that the implant design meets the mechanical safety requirements for clinical applications.

The table underscores the distinct mechanical behaviors of the materials involved in the system. The high elasticity modulus of titanium ensures stability and durability for the derotation plate, while the lower modulus values for cortical and spongy bone reflect their respective flexibility and load-absorbing properties. These distinctions are critical for ensuring the compatibility of the implant with the surrounding biological structures and minimizing stress shielding. The insights from this modeling approach are crucial for optimizing the design and application of the derotation plate, ensuring that it provides the required biomechanical support while minimizing the risk of complications, such as stress shielding, loosening, or fatigue failure.

In the finite element model used in this study, the interactions between the bone, prosthesis, and plate/screws were carefully defined to ensure realistic biomechanical behavior. A frictional contact with a coefficient of 0.3 was applied at the bone–prosthesis interface, allowing limited movement to simulate micromotion during the early postoperative period before full osseointegration. The bone–plate interface was modeled with a surface-to-surface contact using a friction coefficient of 0.42, ensuring realistic load transmission while securing the osteotomized segment with screws to prevent displacement. The screw–bone interface was defined as frictional contact with a coefficient of 0.4, with locking screws modeled as interlocking constraints to eliminate micromotion. At the screw–plate interface, a fully bonded contact was applied to simulate the rigid engagement of locking screws within the plate holes, preventing displacement or loosening under loading conditions. These interface conditions allowed for accurate modeling of the stress distribution, load transfer, and mechanical stability within the finite element analysis framework, aligning with validated biomechanical models commonly used in orthopedic research.

This mathematical modeling lays the groundwork for further experimental validation and clinical applications, emphasizing the importance of integrating computational methods in the development of advanced orthopedic implants. Computer 3D models are shown in Figure 1.

The FEA model of the femur with the installed prosthesis and derotation plate represents a critical step in evaluating the biomechanical performance of the system. Using advanced software tools, such as SolidWorks 2023, Autodesk Inventor Professional 2023, and KOMPAS-3D v19.0 (APM FEM), the 3D geometric structure was discretized into a finite element mesh, enabling a detailed stress–strain analysis. The model consists of 52,704 linear tetrahedral elements, providing an accurate representation of the complex geometry and material properties of the system. A total of 86,463 nodes were defined in the mesh, ensuring sufficient resolution for precise calculations. The incorporation of high-resolution meshing facilitates the simulation of load transfer, stress distribution, and displacement behavior under applied physiological forces.

This comprehensive modeling approach is particularly important for understanding the interaction among the prosthesis, the femur, and the derotation plate. Such insights are crucial for optimizing the implant design, minimizing mechanical complications, and improving clinical outcomes. The finite element mesh for the prosthesis–femur–plate system is illustrated in Figure 2.

The finite element mesh serves as the foundation for subsequent simulations, enabling the evaluation of the biomechanical stability and performance of the implant system under realistic loading conditions. By capturing the intricate details of the system’s geometry and material properties, this modeling framework ensures that the results are both accurate and clinically relevant.

2.3. Surgical Technique

The surgical field was prepared with four applications of a 70% alcohol solution according to aseptic standards. A linear skin incision measuring 16 cm was made along the lateral surface of the upper third of the femur, followed by layer-by-layer dissection of the soft tissues to expose the greater trochanter.

Through an anterior approach, the hip joint capsule was opened. Pathologically altered areas of the capsule were partially excised to ensure optimal visualization and access. Osteotomy of the femoral neck was performed, followed by the removal of the aplastic femoral head.

A subtrochanteric transverse osteotomy of the femur was executed. The true acetabulum was prepared using spherical reamers, sequentially increasing the diameter to 44 mm, as shown in Figure A1, which illustrates the precise location and preparation of the acetabulum. An acetabular cup with a 44 mm diameter was press-fitted with complete immersion, and a polyethylene liner (44 mm) compatible with a 28 mm femoral head was implanted.

The medullary canal of the proximal femoral fragment was prepared using a rasp No. 16. A trial prosthesis stem and head were placed, followed by a reduction into the acetabulum. An assessment indicated the need for additional shortening of the femur. Using an electrocautery knife, a second osteotomy line was marked on the distal femoral fragment, and a shortening of 4 cm was performed using a saw. After alignment, the distal fragment was further refined with rasp No. 16. The prosthesis stem was press-fitted, and stability tests confirmed no pathological movement at the osteotomy site.

To stabilize the osteotomy, a custom-designed derotation plate was applied in accordance with the scientific and technical program. The fixation technique is depicted in Figure A2, showing the placement of the plate and locking screws. Fixation was achieved using three locking screws in each fragment of the femur. Stability tests confirmed the absence of rotational or axial instability, and the synthesis was deemed stable.

The osteotomized femoral fragment, prepared and aligned for final fixation, is presented in Figure A3, highlighting the precision of the surgical steps and the application of the custom plate. The femoral head (size −3.5, 28 mm) was inserted and reduced into the acetabulum without significant force. No dislocation was observed under a maximum range of motion, and no mobility was detected at the osteotomy site.

The wound was stitched in layers with the placement of a paraosseous silicone drain. Intraoperative blood loss amounted to 300 mL.

3. Results

The FEA provided an in-depth evaluation of the biomechanical performance of the prosthesis–femur–derotation plate system under physiological loading conditions. The analysis revealed key insights into stress distribution, displacement, and safety factors, confirming the mechanical reliability and robustness of the system components.

The von Mises stress analysis highlighted the stress distribution across the system, focusing on critical load-bearing areas. The results of this analysis are visualized in Figure 3, which demonstrates stress concentrations at the femoral head, the prosthesis–bone interface, and the derotation plate. The maximum stress of 167.2 MPa was observed at the femoral head due to the concentration of vertical and horizontal forces. The prosthesis–bone interface experienced a stress value of 122 MPa, while the derotation plate showed a peak stress of 76 MPa. These values are well below the yield strength of their respective materials, ensuring safe operation under normal and extreme loading conditions. The uniform stress distribution across the derotation plate further demonstrated its capability to handle biomechanical loads effectively without the risk of mechanical failure.

The displacement analysis provided further insights into the relative movement of the system elements under loading conditions. Figure 4 highlights the displacement distribution within the system. The maximum displacement of 0.1451 mm occurred at the prosthetic head, while the derotation plate exhibited minimal displacement, with a value of 0.08 mm. This underscored the plate’s stabilizing role in the system and its ability to control rotational and axial movements effectively. These results highlight the plate’s contribution to maintaining the mechanical integrity of the osteotomy site and ensuring the long-term stability of the system.

The safety factor evaluation provided a comprehensive assessment of the mechanical reliability of the system. The distribution of safety factors across the system components is visualized in Figure 5, which emphasizes the robustness of the derotation plate. The minimum safety factor of 3.63 was observed in the plate, while the bone and endoprosthesis exhibited safety factors of 1.24 and 2.26, respectively. These results underscore the importance of precise screw placement and material selection in minimizing stress concentrations and ensuring the long-term durability of the implant.

A focused analysis of the derotation plate revealed its stress concentrations under load. Figure 6—von Mises stress on the derotation plate (MPa)—shows the highest stress, 76.02 MPa, localized around the screw holes. This value is significantly lower than the yield strength of 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. Comparative results of SSS calculations.

Indicators	Plate	Bone	Endoprosthesis
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

. 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 subtrochanteric 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 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.

4. Discussion

The results of this study provide critical insights into the biomechanical performance of the prosthesis–femur–derotation plate system, specifically its ability to withstand physiological loading conditions while maintaining structural stability. The findings confirm the robustness and reliability of the derotation plate, validating its role in addressing the challenges associated with subtrochanteric shortening osteotomy in complex cases of hip dysplasia, particularly Crowe type IV. Previous studies have highlighted the importance of proper implant design in achieving optimal biomechanical stability in total hip arthroplasty for severe hip dysplasia [43,44].

The von Mises stress distribution analysis highlighted critical stress concentrations at the femoral head, prosthesis–bone interface, and locking screw holes of the derotation plate. The maximum stress values remained significantly below the yield strength of the materials used, particularly the titanium alloy of the plate. This demonstrates the mechanical efficiency of the design in managing high loads without the risk of failure. The uniform stress distribution observed in the plate further supports its durability and suitability for long-term clinical use. Similar findings have been reported in finite element studies analyzing osteotomy fixation and implant stability [45,46].

A displacement analysis revealed that the derotation plate exhibited minimal displacement under applied loads, with values considerably lower than those at the prosthetic head. This underscores its role in stabilizing the femur and mitigating rotational and axial displacements. The minimal displacement not only ensures mechanical stability but also contributes to promoting osteotomy healing by reducing micro-movements that could otherwise delay bone union. These findings align with previous research that emphasized the importance of displacement control in osteotomy fixation [47,48].

The safety factor evaluation demonstrated that all components of the system, including the derotation plate, maintained a sufficient margin of mechanical safety. The minimum safety factor for the plate, at 3.63, reflects its ability to handle peak stress loads without the risk of material failure. However, the lower safety factor values observed in the bone (1.24) warrant attention, as they indicate areas of potential vulnerability, particularly under extreme loading conditions. Future studies could explore methods to enhance bone strength in these regions, possibly through preoperative planning or additional fixation techniques. Similar biomechanical assessments of orthopedic implants have stressed the need for careful safety factor evaluations to minimize implant-related complications [49].

The focused analysis of the derotation plate revealed that the highest stress concentrations occurred at the screw holes, a finding that highlights the importance of precise screw placement to minimize localized stress peaks. The observed stress levels in this study, however, remained well within safe limits, reaffirming the reliability of the plate’s design and material selection. Compared to traditional fixation methods, such as cable fixation or less rigid plate designs, the derotation plate used in this study demonstrated superior biomechanical performance. Its ability to uniformly distribute stress and control displacement offers a significant advantage in reducing complications, like nonunion, rotational instability, and implant loosening. Studies analyzing osteosynthesis techniques in hip arthroplasty have similarly reported that rigid fixation systems provide improved mechanical outcomes compared to conventional methods [43,46].

The implications of this research extend beyond the specific case of Crowe type IV hip dysplasia. The use of FEA to optimize implant design highlights the potential for computational modeling to inform the development of more effective orthopedic solutions. By providing a detailed understanding of stress–strain behavior and mechanical performance, FEA enables the iterative improvement of implant designs, reducing the need for extensive experimental trials and enhancing clinical outcomes [48,49].

While this study provides robust evidence for the effectiveness of the derotation plate, certain limitations must be acknowledged. The analysis was conducted under idealized loading conditions, which may not fully replicate the complex biomechanical environment of the human hip during dynamic activities. Future studies should incorporate more realistic loading scenarios, including cyclic loading and varying patient anatomies, to further validate the findings. Additionally, experimental validation through in vitro or in vivo testing would strengthen the conclusions drawn from the computational models. These recommendations align with recent studies emphasizing the importance of integrating experimental validation with computational modeling in orthopedic biomechanics.

In conclusion, the results of this study support the working hypothesis that the derotation plate enhances biomechanical stability, reduces displacement, and promotes bone healing in complex hip dysplasia cases. The findings contribute to the growing body of evidence supporting the use of advanced titanium-based fixation systems in orthopedic surgery. By addressing critical factors, such as the stress distribution, displacement control, and safety margins, this study provides a foundation for further research and clinical applications, ultimately improving patient outcomes in challenging orthopedic cases [50,51].

5. Conclusions

This study demonstrated the biomechanical efficiency and reliability of the prosthesis–femur–derotation plate system in treating Crowe type IV dysplastic coxarthrosis. Through finite element analysis, the derotation plate proved to be an effective solution for stabilizing the femur, maintaining axial alignment, and preventing rotational movement during subtrochanteric shortening osteotomy. By restoring the anatomical and biomechanical axis of the limb, the system addresses critical challenges in complex hip reconstruction. The von Mises stress analysis confirmed that all components of the system, including the derotation plate, remained well within their respective material strength limits. With a maximum stress of 76 MPa localized at the screw holes, the titanium plate demonstrated superior load-carrying capacity, significantly below its yield strength (900–1100 MPa). Additionally, the prosthesis and bone experienced maximum stresses of 122 MPa and 167.2 MPa, respectively, further verifying the system’s resilience under physiological loading conditions.

A displacement analysis revealed that the prosthetic head had the highest movement at 0.1451 mm, while the derotation plate exhibited minimal displacement of 0.08 mm, ensuring stability and effective load distribution. This result underscores the plate’s capacity to minimize micro-movements at the osteotomy site, which is crucial for promoting bone healing and maintaining structural integrity during early postoperative recovery. The safety factor evaluation highlighted the robustness of the system, with the derotation plate maintaining a minimum safety factor of 3.63, indicating sufficient strength reserves. Although the bone exhibited a lower safety factor of 1.24, the overall system stability remained uncompromised, ensuring reliable performance under clinical conditions.

The findings validate the system’s superior biomechanical performance compared to traditional fixation methods, offering an optimized solution for treating complex hip dysplasia. By evenly distributing stress, reducing displacement, and providing enhanced fixation stability, the derotation plate improves surgical outcomes while mitigating risks, such as rotational instability and nonunion. This research emphasizes the importance of advanced computational modeling, such as finite element analysis, in optimizing implant design and improving clinical efficacy. The quantitative data provided by this study serve as a foundation for further clinical investigations and experimental validation under dynamic and cyclic loading scenarios.