Artificial Ankle Research Articles

Investigating Material Performance in Artificial Ankle Joints: A Biomechanical Study

This study delves into an in-depth examination of the biomechanical characteristics of various materials commonly utilized in the fabrication of artificial ankle joints. Specifically, this research focuses on the design of an ankle joint resembling the salto-talaris type, aiming to comprehensively understand its performance under different loading conditions. Employing advanced finite element analysis techniques, this investigation rigorously evaluates the stresses and displacements experienced by the designed ankle joint when subjected to varying loads. Furthermore, this study endeavors to identify the vibrating frequencies associated with these displacements, offering valuable insights into the dynamic behavior of the ankle joint. Notably, the analysis extends to studying random frequencies across three axes of motion, enabling a comprehensive assessment of directional deformities that may arise during joint function. To validate the effectiveness of the proposed design, a comparative analysis is conducted against the star ankle design, a widely recognized benchmark in ankle joint prosthetics. This comparative approach serves dual purposes: confirming the accuracy of the findings derived from the salto-talaris design and elucidating the relative efficacy of the proposed design in practical application scenarios.

Effect of novel polyethylene insert configurations on bone-implant micromotion and contact stresses in total ankle replacement prostheses: a finite element analysis.

This study investigates the impact of elastic improvements to the artificial ankle joint insert on prosthesis biomechanics to reduce the risk of prosthesis loosening in TAR patients. CT data of the right ankle was collected from one elderly female volunteer. An original TAR model (Model A) was developed from CT images and the INBONE II implant system. The development of the new inserts adopts an elastic improvement design approach, where different geometric configurations of flexible layers are inserted into the traditional insert. The structure can be divided into continuous flexible layers and intermittent flexible layers. The flexible layers aim to improve the elasticity of the component by absorbing and dispersing more kinetic energy. The newly designed inserts are used to replace the original insert in Model A, resulting in the development of Models B-D. A finite element model of gait analysis was based by gait parameters. Discrepancies in micromotion and contact behaviour were analysed during the gait cycle, along with interface fretting and articular surface stress at 50% of the gait cycle. In terms of micromotion, the improved elastic models showed reduced micromotion at the tibial-implant interfaces compared to the original model. The peak average micromotion decreased by 12.1%, 13.1%, and 14.5% in Models B, C, and D, respectively. The micromotion distribution also improved in the improved models, especially in Model D. Regarding contact areas, all models showed increased contact areas of articular surfaces with axial load, with Models B, C, and D increasing by 26.8%, 23.9%, and 24.4%, respectively. Contact stress on articular surfaces increased with axial load, reaching peak stress during the late stance phase. Models with continuous flexible layer designs exhibited lower stress levels. The insert and the talar prosthetic articular surfaces showed more uniform stress distribution in the improved models. Improving the elasticity of the insert can enhance component flexibility, absorb impact forces, reduce micromotion, and improve contact behavior. The design scheme of continuous flexible layers is more advantageous in transmitting and dispersing stress, providing reference value for insert improvement.

Finite element analysis of artificial ankle elastic improved inserts

To discuss the influence of artificial ankle elastic improved inserts (hereinafter referred to as "improved inserts") in reducing prosthesis micromotion and improving joint surface contact mechanics by finite element analysis. Based on the original insert of INBONE Ⅱ implant system (model A), four kinds of improved inserts were constructed by adding arc or platform type flexible layer with thickness of 1.3 or 2.6 mm, respectively. They were Flying goose type_1.3 elastic improved insert (model B), Flying goose type_2.6 elastic improved insert (model C), Platform type_1.3 elastic improved insert (model D), Platform type_2.6 elastic improved insert (model E). Then, the CT data of right ankle at neutral position of a healthy adult male volunteer was collected, and finite element models of total ankle replacement (TAR) was constructed based on model A-E prostheses by software of Mimics 19.0, Geomagic wrap 2017, Creo 6.0, Hypermesh 14.0, and Abaqus 6.14. Finally, the differences of bone-metal prosthesis interface micromotion and articular surface contact behavior between different models were investigated under ISO gait load. The tibia/talus-metal prosthesis interfaces micromotion of the five TAR models gradually increased during the support phase, then gradually fell back after entering the swing phase. The improved models (models B-E) showed lower bone-metal prosthesis interface micromotion when compared with the original model (model A), but there was no significant difference among models A-E ( P>0.05). The maximum micromotion of tibia appeared at the dome of the tibial bone groove, and the ​​micromotion area was the largest in model A and the smallest in model E. The maximum micromotion of talus appeared at the posterior surface of the central bone groove, and there was no difference in the micromotion area among models A-E. The contact area of the articular surface of the insert/talus prosthesis in each group increased in the support phase and decreased in the swing phase during the gait cycle. Compared with model A, the articular surface contact area of models B-E increased, but there was no significant difference among models A-E ( P>0.05). The change trend of the maximum stress on the articular surface of the inserts/talus prosthesis was similar to that of the contact area. Only the maximum contact stress of the insert joint surface of models D and E was lower than that of model A, while the maximum contact stress of the talar prosthesis joint surface of models B-E was lower than that of model A, but there was no significant difference among models A-E ( P>0.05). The high stress area of the lateral articular surface of the improved inserts significantly reduced, and the articular surface stress distribution of the talus prosthesis was more uniform. Adding a flexible layer in the insert can improve the elasticity of the overall component, which is beneficial to absorb the impact force of the artificial ankle joint, thereby reducing interface micromotion and improving contact behavior. The mechanical properties of the inserts designed with the platform type and thicker flexible layer are better.

A Multidimensional Assessment of a Novel Adaptive Versus Traditional Passive Ankle Sprain Protection Systems

Background: Ankle braces aim to reduce lateral ankle sprains. Next to protection, factors influencing user compliance, such as sports performance, motion restriction, and users’ perceptions, are relevant for user compliance and thus injury prevention. Novel adaptive protection systems claim to change their mechanical behavior based on the intensity of motion (eg, the inversion velocity), unlike traditional passive concepts of ankle bracing. Purpose: To compare the performance of a novel adaptive brace with 2 passive ankle braces while considering protection, sports performance, freedom of motion, and subjective perception. Study Design: Controlled laboratory study. Methods: The authors analyzed 1 adaptive and 2 passive (one lace-up and one rigid brace) ankle braces, worn in a low-cut, indoor sports shoe, which was also the no-brace reference condition. We performed material testing using an artificial ankle joint system at high and low inversion velocities. Further, 20 male, young, healthy team sports athletes were analyzed using 3-dimensional motion analysis in sports-related movements to address protection, sports performance, and active range of motion dimensions. Participants rated subjective comfort, stability, and restriction experienced when using the products. Results: Subjective stability rating was not different between the adaptive and passive systems. The rigid brace was superior in restricting peak inversion during the biomechanical testing compared with the passive braces. However, in the material test, the adaptive brace increased its stiffness by approximately 400% during the fast compared with the slow inversion velocities, demonstrating its adaptive behavior and similar stiffness values to passive braces. We identified minor differences in sports performance tasks. The adaptive brace improved active ankle range of motion and subjective comfort and restriction ratings. Conclusion: The adaptive brace offered similar protective effects in high-velocity inversion situations to those of the passive braces while improving range of motion, comfort, and restriction rating during noninjurious motions. Clinical Relevance: Protection systems are only effective when used. Compared with traditional passive ankle brace technologies, the novel adaptive brace might increase user compliance by improving comfort and freedom of movement while offering similar protection in injurious situations.

Anatomic ankle implant can provide better tibiotalar joint kinematics and loading

Restoration of ankle kinematic functions is the major objective following total ankle arthroplasty (TAA). However, the clinical results of traditional ankle implants are still unsatisfactory. Anatomic ankle implant may provide better ankle kinematic functions and load distribution. In this study, the biomechanical performances between two potential anatomic ankle implants and a commercial INBONE II implant were compared using a previously developed patient-specific musculoskeletal multibody dynamics model during walking. Furthermore, the effects of the different height differences between the medial and lateral borders on the ankle biomechanics and kinematics were also investigated. Significant improvements in kinematic functions especially in internal-external rotation and inversion-eversion, and in load balance between the medial and lateral contacts of the two anatomic ankle implants were observed, as compared to the INBONE II ankle implant. The design of anatomic ankle implant with the medial peak higher than the lateral peak had better performance in restoring the internal-external rotation and balancing the medial and lateral contact forces. The kinematics and loads were not sensitive to the height difference for the anatomic ankle implant with medial border higher than lateral border. The anatomic articular surface design of artificial ankle implant can provide better tibiotalar joint kinematics and loading, therefore, anatomic ankle implant should be considered in the future implant design and surgical procedures.

Biomechanical evaluation of a novel 3D printing tibiotalocalcaneus nail with trilobular cross-sectional design and self-compression effect

The current tibiotalocalcaneal (TTC) nails used in ankle arthrodesis surgery have shortcomings leading to unfavorable clinical failures. This study proposes a novel nail design and fabricated by metal 3D printing that can enhance the global implant stability through finite element (FE) analysis and fatigue testing. A novel titanium nail was designed with trilobular cross-sectional design for increasing anti-rotation stability. This nail has three leads with different, increasing pitches that increase the self-compression effect in the fusion sites. Between the leads, there are two porous diamond microstructure regions that act as a bone ingrowth scaffold. The nail was fabricated by metal 3D printing and implanted into artificial ankle joint to evaluate the self-compression effects. The nonlinear FE analysis was performed models to compare the anti-rotation stability between trilobular nail (Tri-nail) and the conventional circular nail. The static and fatigue four-point bending tests were done to understand the mechanical strength of the novel nail. The experiment of self-compression effect showed that the three lead design provides two stages of significant compression effect, with a pressurization rate as high as 40%. FE simulated results indicated that the Tri-nail group provides significant tangent displacement reduction as well as reduction in the surrounding bone stress value and the stress distribution is more even in the Tri-nail group. Four-point test found that the Tri-nail yielding strength is 12,957 ± 577 N, which is much higher than the approved FDA reference (1026 N). One million cycles using 8% of the yielding strength (1036 N) were accomplished without Tri-nail failure. The proposed novel metal 3D printing Tri-nail can provide enough mechanical strength and is mechanically stable with superior anti-rotation ability and excellent fusion site self-compression effect.

Design and Analysis of a Novel Artificial Ankle-Foot Joint Mechanism

Globally, more than one million limbs are amputated annually. Theoretical and experimental studies thus been undertaken in many countries to develop prosthetics to help alleviate the suffering of people with amputated limbs. This study aimed to design and simulate an artificial ankle joint to mimic huma walking on sloped surfaces efficiently. The new design also attempts to mimic the shape, the size and the range of angle motion of the human ankle joint while simultaneously reducing the cost and weight of the prototype prosthetic ankle unit and increasing durability and responsiveness. The weight of the individual user is the main factor controlling the engagement and disengagement of the artificial ankle joint during the gait cycle, and the new design for the artificial ankle joint was prepared and tested using CATIA and ANSYS software. The suggested model was shown to be effective and reliable and able to adapt to multiple different surfaces. It also achieved high flexibility under various weights of users.

QUANTITATIVE EVALUATION METHOD FOR TIBIOFIBULAR JOINT ALIGNMENT IN ANKLE OSTEOARTHRITIS BASED ON 3D BONE SIZE

Purpose: A remedy for ankle osteoarthritis is artificial joint replacement surgery. By estimating the relative positional difference (alignment) between the bone before and after deformation, precise artificial joint replacement surgery can be performed. By using the estimated alignment, an artificial ankle joint can ensure high satisfaction with less pain and can perform necessary functions. Although bone alignment is currently estimated from X-rays and computed tomography (CT) images, it is difficult to measure three-dimensional (3D) data from two-dimensional (2D) images. Although 3D data can be estimated using a 2D–3D registration method, it requires capturing the bone images multiple times and imposing considerable burden on the patient. In this paper, we propose a method to estimate the 3D bone alignment based on the size of the bone using principal component analysis (PCA), which requires scanning only one data. Method: In the proposed method, PCA is used to create a 3D bone model based on the bone thickness, and the bone alignment is estimated by the Go-ICP algorithm. In this study, the images of the foot were captured using a CT device, and the 3D bone model was created by stacking CT images. For improving the accuracy of the alignment, a reference model based on the bone thickness was created using PCA. Subsequently, the bone was overlapped and the alignment was estimated. Result: For the evaluation of the accuracy of alignment in the proposed method, three types of methods were used to create a bone model. The proposed method was found to be the most accurate with respect to the true value in five of the six evaluation criteria. In addition, the alignment of the tibiofibular joint was evaluated using the proposed method. Regarding the displacement in the [Formula: see text]-axis direction, there were significant differences in both Stage 3B and Stage 4 compared with the healthy subjects. In addition, the magnitude of rotation in the [Formula: see text]-axis direction showed a significant difference in stage 3B as compared with a healthy subject. Conclusion: Using the proposed method, we have shown that bone alignment can be estimated three-dimensionally by scanning the bone data once only. In addition, by comparing with the reference model using PCA based on the thickness of the bone, the accuracy of alignment is improved as compared with the reference model, which is not based on the bone thickness.

Evaluation of Tibiofibular Joint Alignment in Ankle Osteoarthritis Based on 3D Bone Thickness.

A lot of elderly people need to care for joint disease, and one of the treatments for ankle osteoarthritis is artificial joint replacement surgery. Estimating the relative positional difference (alignment) between the bone before the deformation and the deformed bone, artificial joint replacement surgery can be performed precisely. By using the estimated alignment, the artificial ankle joint can obtain high satisfaction with less pain and enough function as an alternative. Although the bone alignment is currently estimated from X-rays and CT images, it is difficult to measure three-dimensional relationships because it is a two-dimensional image. We evaluate a 3D bone alignment based on Principal Components Analysis (PCA) using image deformation. In the proposed method, the PCA is used to create a three-dimensional bone model based on bone thickness, the bone alignment is estimated by Go-ICP algorithm. In this study, the images of the foot were captured using a CT device and the three-dimensional bone model is created by stacking the CT images. For improving the accuracy of overlap, a reference model is created based on bone thickness using the PCA. then, the bone is overlapped using the Go-ICP algorithm and estimated alignment. Using the proposed method, the amount of the displacement in the Z-axis showed a significant difference in Stage 3B compared to healthy subjects. In addition, it also showed a significant difference in Stage 4 compared to healthy subjects. The amount of the rotation in the Z-axis direction showed a significant difference in Stage 3B compared to healthy subjects.

Composite active disturbance rejection robust control for a prototype of an active damping artificial ankle prosthesis

AbstractThe problem of robust control applied to adjust the configuration of an ankle prosthesis based on disturbance estimation has been addressed in this study. Active disturbance rejection control was the paradigm used for controlling the robotic prosthesis by means of a direct active estimation. Based on this active estimation, the robust controller implemented the disturbance cancellation providing a fast converge to the origin of the tracking error. The uncertainties affecting the prosthesis dynamics were identified by a high‐order extended state high gain observer. This identification was used to force the tracking between the actual position and force needed in the ankle prosthesis and some reference values obtained by a biomechanical gait cycle analysis. Therefore, the estimated states were used to implement a robust output feedback controller that was effective to reject actively the perturbations. This rejection implemented within the controller forced the trajectory tracking to a small vicinity of the origin. A strategy based on composite Lyapunov function served to prove that tracking problem for the prosthesis was successfully solved despite the switching nature of the gait cycle. The controller was implemented in numerical simulations for showing the convergence of the tracking error. The convergence of this tracking error to the region around the origin was obtained within the first second of simulation.

Design and simulation of a cable-pulley-based transmission for artificial ankle joints

In this paper, a mechanical transmission based on cable pulley is proposed for human-like actuation in the artificial ankle joints of human-scale. The anatomy articular characteristics of the human ankle is discussed for proper biomimetic inspiration in designing an accurate, efficient, and robust motion control of artificial ankle joint devices. The design procedure is presented through the inclusion of conceptual considerations and design details for an interactive solution of the transmission system. A mechanical design is elaborated for the ankle joint angular with pitch motion. A multi-body dynamic simulation model is elaborated accordingly and evaluated numerically in the ADAMS environment. Results of the numerical simulations are discussed to evaluate the dynamic performance of the proposed design solution and to investigate the feasibility of the proposed design in future applications for humanoid robots.

Full Scale 3D Preoperative Planning System of the Ankle Joint Replacement Surgery with Multimedia System

This study is intended to develop a computer-aided pre-surgical planning and simulating system in a multimedia environment for ankle joint replacement surgery. This system uses full-scale 3D reverse engineering techniques in design and development of the pre-surgical planning modules for ankle joint replacement surgery. This planning system not only develops the real-scale 3D image of the artificial ankle joint but also provides a detailed interior measurement of the ankle joint from various cutting planes. In this study, we apply the multimedia user interface to integrate different software functions into a surgical planning system with integrated functions. The functions include 3D model image acquisition, cutting, horizontal shifting and rotation of related bones (tibia and talus) of the ankle joint in the predetermined time. For related bones of the ankle joint, it can also be used to design artificial ankle joints for adults in Taiwan. Those planning procedures can be recorded in this system for further research and investigation. Furthermore, since this system is a multimedia user interface, surgeons can use this system to plan and find a better and more efficient surgical approach before surgery. A database is available for this system to update and expand, which can provide different users with clinical cases as per their experience and learning.

Full Scale 3D Preoperative Planning System of the Ankle Joint Replacement Surgery with Multimedia System

This study is intended to develop a computer-aided pre-surgical planning and simulating system in a multimedia environment for ankle joint replacement surgery. This system uses full-scale 3D reverse engineering techniques in design and development of the pre-surgical planning modules for ankle joint replacement surgery. This planning system not only develops the real-scale 3D image of the artificial ankle joint but also provides a detailed interior measurement of the ankle joint from various cutting planes. In this study, we apply the multimedia user interface to integrate different software functions into a surgical planning system with integrated functions. The functions include 3D model image acquisition, cutting, horizontal shifting and rotation of related bones (tibia and talus) of the ankle joint in the predetermined time. For related bones of the ankle joint, it can also be used to design artificial ankle joints for adults in Taiwan. Those planning procedures can be recorded in this system for further research and investigation. Furthermore, since this system is a multimedia user interface, surgeons can use this system to plan and find a better and more efficient surgical approach before surgery. A database is available for this system to update and expand, which can provide different users with clinical cases as per their experience and learning.

Wearable acceleration sensor application in unilateral trans-tibial amputation prostheses

The availability of human walking gait data collected from the wearable acceleration sensors for trajectory control of an active artificial ankle joint in the unilateral trans-tibial prosthesis was investigated in this study. It is observed that the collected acceleration data can be used in the rulebased control of the prosthetic leg. A portable microprocessor-based data acquisition system, and data transfer module were designed for capturing the acceleration signals during walking. Flexionextension angle pattern of ankle joint was determined from acceleration signals of two tri-axial wearable accelerometers placed on the shank and foot segments. This pattern was utilized for control of the active artificial ankle joint in the trans-tibial prosthesis. This approach may have the potential of contributing the development of better prostheses.

1A2-B14 2視点X線画像を用いた人工足関節の位置姿勢推定(医療ロボティクス・メカトロニクス(2))

1A2-B14 2視点X線画像を用いた人工足関節の位置姿勢推定(医療ロボティクス・メカトロニクス(2))

Active Weight Bearing Tibio-talar Motion and Meniscal Translation in the S.T.A.R Prosthesis-A Radiographic Comparative Study of the S.T.A.R. Toward the Opposite Normal Ankle Joint

Background: The kinematics of meniscal bearing artificial ankle joints is not well documented after the implantation of the prosthesis. Purpose of the study To investigate the active weight-bearing tibio-talar motion and the translation of the meniscus radiographically after mean 36 months in patients with unilateral traumatic ankle osteoarthritis. Methods: Straight lateral radiographic views under image intensification of the replaced ankle and the opposite normal ankle were performed during active weight-bearing. The tibio-talar motion of both ankles, as well as the translation/rotation of the meniscus in the replaced ankles was measured. Results: The total range of motion in normal ankles was mean 59° (33.7–68.7). The motion in the replaced ankles was mean 37.2° (16.7–53.3), p<0.02. Normal extension was mean 24° (3.7–37.7). Replaced ankle extension was mean 14.7° (2-26.7), p<0.02. Normal plantarflexion was mean 31° (19.7–51), in replaced ankles plantar flexion was mean 22.3° (12.3–34), p<0.02. The translation of the meniscus was 0.7 mm (-1.5 to 1.2). This could also be calculated to be a rotation of 3.9°. The translation of the meniscus is most probably a combination of gliding and rotation. Conclusions: The active weight-bearing motion of the replaced ankle is about 2/3 of the normal ankle motion. Functionally this is a satisfactory result. After 36 months the translation of the meniscus is rather small suggestion that the replaced ankle has reached a steady state of conformity.

Full-scale 3D multimedia preoperative planning system for total ankle joint replacement

This study presents a "Full-Scale 3D Multimedia Preoperative Planning System for Total Ankle Joint Replacement" that evaluation and verifies the usability of artificial ankle joint replacement operation. The system uses a full-scale computer-assisted engineering technique for designing and developing preoperative planning modules. The multimedia user interface integrates the function of different software programs in order to plan and simulate the operation. These functions include 3D image model capturing, sectioning, translocation, rotating, and measuring relevant foot anatomy, all of which can be integrated and used for surgical planning, as well as for future study and discussion. Furthermore, because the system is computer based with a multimedia user interface, surgeons can use it to explore the optimal operative procedure. The system also has a databank that can update and expand, and can be used to provide clinical cases to different users for education and training.

Operative matching for One patient with artificial ankle joint transplantation

随着对踝关节运动学及动力学特点的深入了解和假体设计的改进,全踝关节置换术已成为缓解疼痛、改善步态、重建踝关节功能的有效手段[1].由于踝关节置换的手术指征严格,目前临床上仍未广泛开展,其相关的报告及护理配合极少见.我院于2003年9月应用Link Star人工关节假体实施踝关节置换术治疗创伤性踝关节炎1例,术后疗效肯定,随访18个月疗效满意,现报道如下。

An artificial ankle joint.

Ankle fusion has been the time-honored treatment for painful debilitating conditions of the ankle due to osteoarthritis and rheumatoid arthritis. It is not a uniformly successful operation and has a high complication rate. If there is pre-existing disease in the knee or midtarsal joints, the pain is frequently made worse by ankle fusion. If there is no pre-existing disease, then painful degenerative changes frequently occur in the midtarsal joints subsequently. An artificial ankle joint has been used successfully since 1973 in patients who otherwise would require ankle fusion. The design of the prosthesis allows unrestricted motion in all planes. It also allows imperfect placement of the device without compromising results. The dome of the talus is not resected during insertion of the prosthesis. Only 1 cm of distal tibia is resected, thus allowing fusion without difficulty should it later become necessary. The superior position of the polyethylene device decreases wear from particulate matter which might settle by gravity. Study of 50 total ankle arthroplasty cases shows that predictably good results can be obtained in ankles with good stability, reasonably normal anatomy, and rheumatoids who are not on long-term steroid therapy.

F-0902 3次元挙動を考慮した人工足関節の力学的検討(J21-1 骨格構造のバイオメカニクス)(J21 生体構造と組織のバイオメカニクス)

Total ankle replacement is one of the effective treatments for osteoarthritis and rheumatoid arthritis in orthopedics. In this filed, loosening that occurs between an artificial ankle joint and the bones several years after operation has been becoming a problem recently. Design of the artificial ankle joint, which is based on experience of doctors, has not been analyzed sufficiently in dynamic field yet. Then, The authors studied dynamic behavior around the artificial ankle joint using Finite Element Method, and optimized the design of the artificial ankle joint with 2-dementional model and 3'dementional model targeting on lengthening the life of the artificial ankle joint.