Establishment of finite element model of varus-type ankle arthritis and biomechanical analysis of different correction models for tibial anterior surface angle / 中国修复重建外科杂志

OBJECTIVE@#To establish the finite element model of varus-type ankle arthritis and to implement the finite element mechanical analysis of different correction models for tibial anterior surface angle (TAS) in supramalleolar osteotomy.@*METHODS@#A female patient with left varus-type ankle arthritis (Takakura stage Ⅱ, TAS 78°) was taken as the study object. Based on the CT data, the three-dimensional model of varus-type ankle arthritis (TAS 78°) and different TAS correction models [normal (TAS 89°), 5° valgus (TAS 94°), and 10° valgus (TAS 99°)] were created by software Mimics 21.0, Geomagic Wrap 2021, Solidworks 2017, and Workbench 17.0. The 290 N vertical downward force was applied to the upper surface of the tibia and 60 N vertical downward force to the upper surface of the fibula. Von Mises stress distribution and stress peak were calculated.@*RESULTS@#The finite element model of normal TAS was basically consistent with biomechanics of the foot. According to biomechanical analysis, the maximum stress of the varus model appeared in the medial tibiotalar joint surface and the medial part of the top tibiotalar joint surface. The stress distribution of talofibular joint surface and the lateral part of the top tibiotalar joint surface were uniform. In the normal model, the stress distributions of the talofibular joint surface and the tibiotalar joint surface were uniform, and no obvious stress concentration was observed. The maximum stress in the 5° valgus model appeared at the posterior part of the talofibular joint surface and the lateral part of the top tibiotalar joint surface. The stress distribution of medial tibiotalar joint surface was uniform. The maximum stress of the 10° valgus model appeared at the posterior part of the talofibular joint surface and the lateral part of the top tibiotalar joint surface. The stress on the medial tibiotalar joint surface increased.@*CONCLUSION@#With the increase of valgus, the stress of ankle joint gradually shift outwards, and the stress concentration tends to appear. There was no obvious obstruction of fibula with 10° TAS correction. However, when TAS correction exceeds 10° and continues to increase, the obstruction effect of fibula becomes increasingly significant.

Early effectiveness of a new minimally invasive plate in treatment of varus-type ankle arthritis / 中国修复重建外科杂志

OBJECTIVE@#To evaluate the early effectiveness of a new minimally invasive plate in the treatment of varus-type ankle arthritis.@*METHODS@#A clinical data of 15 patients with varus-type ankle arthritis who met the selection criteria between March 2021 and October 2021 were retrospectively analyzed. All the patients were treated with medial open-wedge supramalleolar osteotomy and fibular osteotomy. The osteotomies were fixed with the new minimally invasive plate. There were 7 males and 8 females with an average age of 49.8 years (range, 16-71 years). The causes of ankle arthritis included post-fracture deformity in 1 case, sprain in 8 cases, and acquired clubfoot in 1 case; and 5 cases were without obvious factors. The disease duration ranged from 1 to 12 years, with an average of 4.1 years. Comparisons were made between pre-operation and the last follow-up in the Takakura staging, the American Orthopedic Foot and Ankle Society (AOFAS) ankle-hindfoot score, foot function index (FFI), visual analogue scale (VAS) score, tibial anterior surface angle (TAS), tibial lateral surface angle (TLS), and talar tilt (TT).@*RESULTS@#All incisions healed by first intention. All patients were followed up 7-18 months (mean, 12.8 months). At last follow-up, the AOFAS ankle-hindfoot score, FFI, VAS score, and Takakura staging significantly improved when compared with the preoperative ones ( P<0.05). X-ray films showed that the osteotomy healed at 3 months after operation. At last follow-up, TAS significantly increased and TT decreased when compared with the preoperative ones ( P<0.05), and the difference in TLS between pre- and post-operation was not significant ( P>0.05). Complications included 1 case of intraoperative screw breakage and 2 cases of nerve injury of the affected foot. None of the patients complained of significant discomfort at the plate placement during follow-up, and no loosening of the internal fixator occurred. Eleven patients were very satisfied with the effeectiveness, while 4 were relatively satisfied.@*CONCLUSION@#The new minimally invasive plate for the varus-type ankle arthritis has good early effectiveness in relieving ankle pain, correcting deformity, improving limb alignment and ankle function, and reducing the incidence of postoperative incisional complications.