Three-dimensional finite element analysis used to compare six different methods of syndesmosis fixation with 3.5- or 4.5-mm titanium screws: a biomechanical study

Fatigue Behavior of the Auxetic Porous Bone Screw Under the Multiaxial Cyclic Loads in Tibiotalocalcaneal Arthrodesis

PURPOSE

The auxetic porous bone screw (AS) has favorable anti-pullout and osseointegration performance, demonstrating application potential in orthopedic surgeries. The uniaxial fatigue behavior of AS has been well understood. Considering that AS will withstand complex physiological loads in practical application, this study aims to investigate the fatigue behavior of AS under the multiaxial loads in tibiotalocalcaneal arthrodesis.

METHODS

AS and nonauxetic bone screw (NS) with the same porosity were designed based on re-entrant and hexagonal units, respectively. Finite element models of tibiotalocalcaneal arthrodesis implanted with AS and NS were established. Based on the curves of ground reaction forces borne by foot during normal gait cycle, the multiaxial loading spectrums were created and applied to the models. The multiaxial fatigue simulations were conducted to calculate the fatigue life and principal stress distributions of bone screws.

RESULTS

Under the multiaxial loads in tibiotalocalcaneal arthrodesis, fatigue fracture was prone to occur in the AS and NS implanted in medial calcaneus. The minimum fatigue life and maximum principal stress of AS and NS were all located near the screw caps connected with the fixation plate. The tensile stress concentration of AS was significantly higher. The estimated fatigue life of AS and NS was approximately 46400 and 1820000 cycles, respectively.

CONCLUSION

The fatigue life of AS was significantly lower than that of NS, which could not meet the fatigue resistance requirement during the recovery period of tibiotalocalcaneal arthrodesis. Local optimization should be conducted near the screw cap of AS to improve its multiaxial fatigue resistance.

Biomechanical Sequelae of Syndesmosis Injury and Repair

This review characterizes fibula mechanics in the context of syndesmosis injury and repair. Through detailed understanding of fibula kinematics (the study of motion) and kinetics (the study of forces that cause motion), the full complexity of fibula motion can be appreciated. Although the magnitudes of fibula rotation and translation are inherently small, even slight alterations of fibula position or movement can substantially impact force propagation through the ankle and hindfoot joints. Accordingly, implications for clinical care are discussed.

Disease-Specific Finite element Analysis of the Foot and Ankle

Finite-element analysis is a computational modeling technique that can be used to quantify parameters that are difficult or impossible to measure externally in a geometrically complex structure such as the foot and ankle. It has been used to improve our understanding of pathomechanics and to evaluate proposed treatments for several disorders, including progressive collapsing foot deformity, ankle arthritis, syndesmotic injury, ankle fracture, plantar fasciitis, diabetic foot ulceration, hallux valgus, and lesser toe deformities. Parameters calculated from finite-element models have been widely used to make predictions about their biomechanical correlates.

Is Advanced Imaging a Must in the Assessment of Progressive Collapsing Foot Deformity?

Advanced imaging modalities have, in very recent years, enabled a considerable leap in understanding progressive collapsing foot deformity, evolving from a simple confirmation of clinical diagnostic using basic measurements to minute understanding of soft tissue and bone involvements. MRI and weight-bearing cone-beam computed tomography are enabling the development of new 3-dimensional measurement modalities. The identification of key articular and joint markers of advanced collapse will allow surgeons to better indicate treatments and assess chances of success with conservative therapies and less invasive surgical procedures, with the hope of improving patient outcomes.

Biomechanical evaluation of syndesmotic fixation techniques via finite element analysis: Screw vs. suture button

BACKGROUND AND OBJECTIVE

Tibiofibular syndesmotic injuries may cause degenerative changes, reduction in ankle function and compromising ankle stability. Different fixation techniques try to restore its functionality. Screw-fixation is the gold-standard. Recently, suture-button fixation has aroused the attention because it allows for physiologic micromotion while maintaining an accurate reduction. The aim of this study is to compare the biomechanical behaviour of both fixation techniques using the finite element method.

METHODS

A three-dimensional finite element model of the tibiofibular joint was reconstructed simulating the intact ankle and the injured syndesmosis. Then, different methods of syndesmosis fixation were analysed: screws (number of cortices, number of screws and distance between screws) and suture buttons (single, double parallel and double divergent with a sensitivity analysis on the pretension forces) configuration. Ligaments and cartilages were included and simulated as spring elements. Physiological loads during stance phase were simulated.

RESULTS

Syndesmosis widening and von Mises stresses were computed. Syndesmosis widening in the injured configuration compromised joint stability (2.06 mm), whereas using a single quadricortical screw (0.18 mm) stiffened the joint. Syndesmosis widening using suture-buttons were closer to syndesmosis widening of the intact ankle configuration (0.97 mm). Von Mises stresses were higher for the titanium screws than for the suture buttons.

CONCLUSIONS

A detailed biomechanical comparison among different syndesmotic fixation was performed. Suture buttons have advantages with regard to syndesmosis widening in comparison to screw fixation. This fact supports the good long-term clinical results obtained with suture buttons fixation. The proposed methodology could be an efficient tool for preoperative planning.

Acute and Chronic Syndesmotic Instability: Role of Surgical Stabilization

Acute and chronic syndesmotic injuries significantly impact athletic function and activities of daily living. Patient history, examination, and judicious use of imaging modalities aid diagnosis. Surgical management should be used when frank diastasis, instability, and/or chronic pain and disability ensue. Screw and suture-button fixation remain the mainstay of treatment of acute injuries, but novel syndesmotic reconstruction techniques hold promise for treatment of acute and chronic injuries, especially for athletes. This article focuses on anatomy, mechanisms of injury, diagnosis, and surgical reduction and stabilization of acute and chronic syndesmotic instability. Fixation methods with a focus on considerations for athletes are discussed.

Identification of Surgical Plan for Syndesmotic Fixation Procedure Based on Finite Element Method

Syndesmosis injuries account for approximately 20% of ankle fractures that require surgery. Although multiple surgical options are available, all of them are based on metal screws. Serious complications that arise when applying metal screws include screw loosening or breakage. To prevent such complications, we applied a simulation method using a finite element (FE) analysis. We created a 3D FE model of an ankle joint and conducted an FE analysis focusing on syndesmosis in terms of the level, material, and diameter of the syndesmotic screw and the number of penetrated cortical bones. The magnitude and direction of the force applied to the tibia in the midstance state were considered for simulating the model. The maximum von-Mises stress and syndesmosis widening were analyzed in terms of different biomechanical parameters. We identified the characteristics of the most biomechanically stable syndesmotic screw and its fixation point on the basis of the two parameters. We demonstrated that the ideal syndesmotic screw fixation should be fixed at a level 20 to 25 mm above the ankle using a 4.5 mm titanium screw.