Finite element analysis of artificial ankle elastic improved inserts / 中国修复重建外科杂志

OBJECTIVE@#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.@*METHODS@#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.@*RESULTS@#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.@*CONCLUSION@#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.

Design and application status of three-component total ankle replacement prosthesis / 中国组织工程研究

BACKGROUND: The early total ankle replacement has been abandoned for long times due to the insufficient understanding of the ankle joint biomechanics, higher implant failure rates and complications. With the updating of the design concept about ankle prosthesis, total ankle replacement surgery is now more and more popular among surgeons. At present, the three-component total ankle replacement prosthesis is considered to be more in line with the normal biomechanical requirements of the ankle joint, and has been gradually promoted for clinical application. OBJECTIVE: To understand the biomechanics of the ankle joint, summarize the design features of the three-component total ankle joint replacement prostheses, and summarize experience for further prosthetic design. METHODS: The first author used a computer to search CNKI and PubMed for the literature on total ankle replacement prostheses from inception to February 2020. The key words were “total ankle replacement prosthesis design, STAR prosthesis, HINTEGRA prosthesis, BOX prosthesis”. RESULTS AND CONCLUSION: (1) The STAR, HINTEGRA, and BOX prostheses have shown acceptable survival rates and clinical results in clinical applications; however, a large number of cases and long-term follow-up were also required. (2) The designs of the three kinds of total ankle replacement prostheses all focus on restoring the anatomy of the physiological ankle joint, reproducing the axis of motion of the ankle joint, being compatible with the geometry of the ligament, and reducing the mechanical alignment of the tissue around the ankle joint. (3) To achieve maximum ligament compatibility, the articular surface design of the prosthetic component must be two physiological anatomic shapes or two non-physiological anatomic shapes. (4) There is a significant difference between the shape of the Chinese ankle and that of Caucasian. We are looking forward to design and develop a more suitable prosthesis for Chinese peoples.

Design and 3D finite element analysis of personalized ankle prosthesis / 医用生物力学

Objective To propose a personalized design of anatomic ankle prosthesis that can avoid and reduce the high failure rate and risk of ankle prosthesis in clinic. Methods The 3D finite element non-linear model of normal human ankle system was established and verified. The anatomic ankle prosthesis was then designed to simulate total ankle replacement, and the 3D finite element model with both the prosthesis and ankle system was established. The biomechanical characteristics of this prosthesis were calculated and analyzed after gait loads were applied. Results For the normal ankle system, the maximum plantar contact stress was 214.6 kPa and the maximum Von Mises stress of foot bone was 8.96 MPa. The reliability of the normal ankle system model was verified by comparing the simulated results with those reported by literature. After the prosthesis implantation, the simulated maximum Von Mises stresses of talus prosthesis, tibial UHMWPE liner, tibial prosthesis were 23.88, 19.24 and 73.01 MPa, respectively. The stress of the ankle prosthesis increased drastically compared with that of normal ankle system. Conclusions The comparison results by finite element analysis examine the feasibility of the personalized ankle prosthesis, and provide references for optimization of prosthesis design and its clinical application.

Short-Term Results of the Total Ankle Arthroplasty with Mobility Total Ankle Prostheis / 대한정형외과학회잡지

PURPOSE: Recently, minimally constrained 3-component total ankle systems have been often performed to address painful ankle arthritis. We report early clinical and radiographic outcome of the total ankle arthroplasty with Mobility system for end-stage ankle arthritis. MATERIALS AND METHODS: Total ankle arthroplasty was performed with Mobility total ankle system in 40 ankles (39 patients) from November 2008 to January 2013. The mean age at surgery was 63.7 years (range, 50-78 years). The mean follow-up duration was 20.8 months (range, 12-56 months). The primary etiology for ankle arthritis was post-traumatic arthritis (26 ankles, 65%). The outcome was assessed based on visual analogue scale (VAS), American Orthopaedic Foot and Ankle Society (AOFAS) ankle-hindfoot function score, patient satisfaction and radiographic measurements. RESULTS: There was a significant reduction in VAS pain score from an initial average of 7.7 points (range, 5-10 points) to 2.8 points at the final follow-up (range, 0-7) (p<0.05). The mean AOFAS score improved significantly from 46.8 (range, 15-68) preoperatively to postoperatively 82.4 (range, 63-100) (p<0.05). Eighty-one percent of patients were satisfied with the result. Combined surgeries, such as Achilles tendon percutaneous lengthening, were performed in twenty-one cases of 40 ankles. CONCLUSION: The current short term results of Mobility total ankle arthroplasty showed a quite favorable functional and radiographical outcome with few major complications. However, the long term follow-up study with larger number of cases is needed in the future.

Ankle Salvage Procedure without Internal Fixation for Large Bone Defect after Failed Total Ankle Arthroplasty: A Case Report / 대한족부족관절학회지

In treatment of failure in ankle joint replacement therapy, talar avascular necrosis with massive bone defect, talus fracture with severe comminution and bone defect and ankle dislocation, treatment of large bone defects is considerably important for ankle joint stability and union, therefore, the choice of treatment for large bone defects is use of femoral head or iliac crest bone graft and rigid internal fixation. Because first generation total ankle arthroplasty performed for the first time using a cemented fixation technique requires a large amount of bone resection during re-surgery and there is some possibility of a larger bone defect after removal of implants, in cases where prosthesis for the defect is needed, performance of palliative femoral head or iliac crest bone graft and rigid internal fixation can be difficult. We report on a case of a 48-year-old woman who had experienced ankle pain for 25 years since undergoing total ankle arthroplasty. Because the patient had little ankle motion and rigid soft tissue despite a large bone defect caused by aseptic loosening, a good outcome was obtained only for the femoral cancellous bone graft using allo femoral head without internal fixation.

Total Ankle Replacement in Pigmented Villonodular Synovitis of Ankle Joint (A Case Report) / 대한족부족관절학회지

Pigmented villonodular synovitis (PVNS) is a rare proliferative disease affecting joint synovium, tendon sheaths, bursae. The usual treatment for PVNS is a surgical excision. If destructive joint lesions have occurred, complete resections must be performed followed by arthrodesis or arthroplasty. We report a case of a pigmented villonodular synovitis involving an ankle joint which was treated by total ankle replacement for recurrence after simple synovectomy.

Change regulatives of bone mineral density after total ankle arthroplasty:six cases results in connective three years / 中国矫形外科杂志

[Objective] To study the change regulatives of BMD(bone mineral density)in after total ankle arthroplasty.[Methods]From Oct.1997 to Dec.2004,the BMD of the subjects were measured to involve in the study.There were 6 cases(5 male,1 female)with an average of 54.4 years old.Their BMD of the subjects was measured by DEX-A(Lunar)at the tibia and talus of the ankle post-arthroplasty in 6 months,12 months,2 years and 3 years postoperatively.All data were saved in computer and all statistical analyses were performed uaing SPSS 8.0 system in personal computer.[Results]The bone trabecula growing into micropore coated of the prosthesis has been showed on radiograth post-surgeryat average period of 1.5 years to 2 years.In the third year itreached bone mass at the distal tibia and talus of the total ankle replacement,which mean BMD 0.854?0.217 at post operative 6 months,BMD 0.975?0.142 at post operative 12 months,BMD 0.956?0.213 at post operative 2 years,and 1.155?0.210 at 3 years(P