| Partial resectioning of the fibula is mainly done for using fibula as a graft or for other reasons including osteomyelitis, fibular tumors, or in cases of fibular fracture with severe bone loss. The implications of fibular resection on the ankle joint have been widely debated. It has been shown to cause ankle pain in 10-40% of patients, ankle instability, muscle weakness, and in some cases, functional loss and ankle ectropion malformation in pediatric age groups. Biomechanically, any amount of fibular resection done for any purpose is likely to decrease the contact area of the tibiotalar joint and raise the peak pressure inside the joint. Various research done in this arena have brought forth diverse conclusions on the length of fibula required to preserve ankle function and avoid any clinically significant complaints.It is universally established that the greater the amount of fibula resection and the more proximal it is to lateral malleolus, the greater the chances of clinical symptoms and instability. Traditionally, belief is to preserve at least 5cm of the length of fibula or roughly 7.5 cm of the distal fibula. However there are few clear cut guidelines based on cadaveric biomechanical studies to substantiate the fact. Also, there is lack of data on biomechanical impact of primary fixation of distal tibiofibular joint following resection of the fibula. Comparison of experiments to compare different degrees of resection of the fibula and the implementation of the intervention in a fixed state, the ankle joint biomechanical stability to the fibula for clinical use of resources to provide strong experimental evidence.In this cadaveric study, a biomechanical analysis of the impact of fibular resections at different levels and whether the fixation of distal tibiofibular joint mitigates instability caused by the resection. This study is likely to provide a biomechanical basis for optimal utilization of fibula for graft purposes and also establish guidelines for fixation of distal tibiofibular joint in such cases and hopefully prevent occurrences of secondary ankle osteoarthritis in clinical practice. From the experimental point of view of biomechanics to understand the different degrees of fibular shortening effect on the stability of the ankle, of which the biomechanical mechanism. The fibular resection where appropriate, the use of certain anatomical fixation of the fibula is shortened to improve the instability of the ankle after fibular resection, and further for clinical use of the fibula on the effective removal and provide strong experimental evidence.Six fresh adult cadavers were used to procure lower limb samples for the study. None of them had any obvious trauma or deformities on gross examination. The lower limbs were amputated at the joint and the entire specimen, including intact skin, muscle, and bone, was used for experiment and biomechanical study.Fibula was osteotomised at different levels starting from the fibular head to 6cm above the lateral malleolus. Fibula was divided into three parts:proximal 1/3, middle 1/3, and distal 1/3. Meanwhile, the specimens were assigned to six groups according to amputation degrees:normal conditions (N), cutting the proximal third of fibula (A), cutting the middle third of fibula (B1), B1 with fixation (B2), cutting the distal third of fibula (C1), C1 with fixation (C2). The distal tibiofibular fusion was done using cortical screws and bone grafts. The specimens with the implanted sensors were placed on the material testing machine (ELF-3510AT, Bose,Inc., USA). The horizontal plates were attached to the soles of the feet of the specimens to imitate standing station of an adult, making sure that the ankles were in neutral position at all times.700N axial load was added using material testing machine with the speed of 50N/S and kept for 50s. At the same time, all individual parameters obtained from the ankle specimen were recorded. The above procedure was repeated three times on each specimen, and the average of the dates in each station was recorded as experimental result. The repeated measurements and variance analysis of the dates was completed by SPSS 13.0.Before in loading, the medial malleolus and lateral malleolus were labeled some significant blocks at the osseous prominent parts, then send the specimens in reasonable scanning range for axial loading experiment, in the loading process using 3D Laser Scanning System scanning the specimens surface. The progressive-scan mode was used by the system, through deflection scanning first laser beam, line parallel surface to certain scanning specimens scan scope and spacing (precision 0.01 mm) to record the initial space reversible specimen surface in position, and keep 700N experimental loading to the static space reversible specimen surface position, will the two measurements using spatial data form the point cloud file save, use professional analysis software processing has saved the point cloud files, and work out the lateral malleolus representatives inside, the value of relative displacement between the medial malleolus and lateral malleolus were be measured.After fibular osteotomy, though the tibiotalar joint did not change in anatomic form, the contact area of joints and intersegment pressure changed to some degree. Dynamic loading to 700N in the speed of 50N/S by BOSE materials experiment machine and was maintained at 50s. The sensor's data output was displayed 2-or 3-dimensionally on a computer monitor and analyzed by I-Scan application software. In the normal station, with ankle in neutral position, In all three cases of fibular resection at different levels (proximal, middle, and distal third), the contact area and average pressure of tibiotalar joint had a significant change (P<0.05) with a decreasing tendency, compare with fibular intact, the peak pressure of tibiotalar joint had a significant change (P<0.05), with a increasing tendency. After distal 1/3 fibular resection, the ontact area and peak pressure of tibiotalar joint had a statistical significance compare(P<0.01) with fibular intact. However, comparison between different degrees of resection of the fibula had no statistical significance (P>0.05).6 specimens turn in the middle fibula resection of 1/3 (B1) and distal 1/3 (C1), the next line of fusion between the tibia and fibula and screw fixation, measured after tibiotalar joint contact area were compared preoperative significant difference, but with intact fibula was no statistical difference(P>0.05).Resection of the proximal 1/3 fibula, when the test machine loaded to 700N, It has begun to affect the internal and lateral malleolus displacements. Entire loading process was always in neutral position of ankle state. The lateral malleolus displacement has significant differences (P<0.01) compared with the fibular intact after the fibula resection, And with the increase in the length of the fibular resection of the ankle was get worse. The lateral malleolus displacements at the direction of top or bottom, internal or lateral were compared with the fibula intact, only the fibular middle 1/3, distal 1/3 resection has significant differences (P<0.01). Fibular proximal 1/3 resection compared with the fibular intact, the lateral malleolus displacements only in the direction of anterior and posterior has a significant difference (P<0.01). When the distal tibiofibular syndesmosis fixation, the lateral malleolus displacement in the three directions over the respective state of the fibula resection were statistically significant (P<0.05).When the removal of the distal fibula 1/3 of the tibiofibular syndesmosis fixation, has no significant difference (P>0.05) compared with the fibular intact, and the value close to normal levels.Fibular resection is carried out for a variety of reasons but mainly for using the fibula as bone graft. The studies done in the past have demonstrated that there is biomechanical impact of the procedure on the ankle joint. These studies have suggested that the amount of resection and the distance of resection level from lateral malleolus have a bearing on the function of the ankle joint. The amount and exact degree of the resection have not been quantified in detail in various biomechanical studies that have been conducted. It also remains to be conclusively proven whether the fusion of distal tibiofibular joints have an impact on the functional outcome and any improvement in biomechanics. Few researchers in the past have elucidated the effect of fibular coloboma on the contact characteristics of tibiotalar joint. Fibular coloboma would change the contact area of the tibiotalar joint, whether caused secondary to trauma or from deliberate clinical bone grafting. With improvement in techniques of biomechanical analysis, such as the ones used in this study, it was realized that after resection of fibula there were significant changes in tibiotalar contact area and peak stresses at the joint level. After biomechanical analysis of fibular osteotomy at different degrees in fresh foot static specimens.The contrast studies done above demonstrated that the contact area of the tibiotalar joint presented a reduction tendency and the distance of resection level from lateral malleolus increased at the same time during the process of fibula resectioning from proximal to distal. It was possible because that each specimen were measured with repeated loading experiments at vivo state. The repeated action to tibiofibular joint result laxation of ligament and enlarge activation scope of tibiofibular joint, which induce the phenomenon of anabatic shift.In clinical application, there is no consensus on the impact of the length of fibula after resection on the functional outcome. After resecting a segment of fibula, since contact area of tibiotalar joint deflates and shifts, the mean stress increases and crest value pressure area gets redistributed. Normal weight loading areas shift to the primary, non-weight loading area leading to synovial effusion and thereby depriving joint cartilage of critical nutritional ingredients from synovial fluid. This can result in cartilage cells becoming pyknotic, and in this circumstance, necrosis tends to ensue due to lack of materials and water. The end result of this cascade is deterioration in joint function and eventual arthritis.This study has demonstrated that cutting equal length bone block in different parts of the fibula has different consequences on contact area and crest value stress of tibiotalar joint. When osteotomised at the distal third portion of the fibula, there are significant differences in tibiotalar joint contact area and crest value stress compared with the complete fibula. When the proximal 2/3 of fibula is cut, the relevant data of tibiotalar joint also has similar differences. However, when the distal 1/3 is cut, although the result still significantly differs from normal test values, the effect is less than the former two.Accordingly, the results suggestted that preserving as much of the length of the fibula as possible, at least proximal 1/3 during fibular grafting or osteotomy, would prevent adverse effects on functional outcome. If doing bone grafting and more than 1/3 of the fibula needs resecting, we should further consider to recover a fine contact area of tibiotalar joint and avoid the destroy of excessive crest value stress on tibiotalar joint, then contact characteristics would return to normal levels postoperatively. We took fixation on ibiotalar joint after cutting distal fibula by terms, followed by repeated loading experiment. Our study suggested that after fixation, contact area and crest value stress on tibiotalar joint have significant changes, and contact area on tibiotalar joint get close to the lever of complete fibula. Bone graft fusion and pinning after fibula defect could effectively partly improved contact characteristics of ankle. Fixing the fibula stump could not just recover the stable mechanics in the distal tibiofibular syndesmosis, but also improved contact characteristics the in gravity conduction process of tibiotalar joint. Therefore, Bone graft fusion and pinning on the distal of tibiotalar joint are feasible and significant fixation methods. We suggest that in clinical application, we could adopt proper methods to make necessary fixation on defect tibiofibula, and to decrease harmful effects on ankle.Fibula has certain motor functions, especially that the position of distal fibula will change by the motion of ankle. When ankle has lability changes, the range of movement of distal fibula will change significantly. When fibula cutting length exceed middle 1/3 of fibula, ankle will be in neutral position. The movement of ankle in different directions all have significant changes, which possible because that the tibiofibula membrane and surrounding soft tissue have great influence on movement of fibula. Along with the increase of cutting length of fibula, interaction effect of the tibiofibula membrane and surrounding soft tissue to fibula become more and more small, which will induce abnormal movement of fibula more and more obviously. Therefore, fibula should be treatment appropriately after fibula cutting to avoid complication. The current study proved that increasing the length of resection directly correlates with a decrease in the articular surface of tibiotalar joint, and inversely correlates with the joint crest value stress. Distal fibula plays a significant role in the inferior tibiofibular syndesmosis, which participates in stress distribution in the articular surface of lateral malleolus and tibiotalar joint through hand spike principle. Fibular length decreases after partial osteotomy, which changes continuity of tibia stress distribution, and as a result, affects stability of tibiofibula combination as well as the abnormal stress and function in the ankle. Therefore, we performed clinical bone graft fusion-stabilization to improve the ankle stability. Contact area and crest value pressure of tibiotalar joint were measured with repeated loading experiments, which revealed notable changes in specimens after intervention compared with those before intervention. Fixing the fibula stump could not just recover the stable mechanics in the distal tibiofibular syndesmosis, but also improved contact characteristics the in gravity conduction process of tibiotalar joint. In summary, surgical intervention in the form of stabilization of distal tibiofibular joint to fibular osteotomy has certain clinical applications.Finally, graft fusion and pinning after fibula defect could not only improved contact characteristics of ankle and recover the stable mechanics in the distal tibiofibular syndesmosis, but also repair the support effect of distal fibula on ankle stability changes. Bone graft fusion and pinning can effectively improved the contact characteristics of tibiotalar joint and location relationship between medial malleolus and lateral malleolus, thereby have positive effect on ankle stability after fibular restection.
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