Finite element analysis of different pedicle screw internal fixations for first lumbar vertebral fracture in different sports conditions.

OBJECTIVE: Lumbar fractures are the most common spinal injuries, and surgery is required for severe fracture. This study aimed to investigate the variations in motion and stress in varying states of activity after minimally invasive and traditional open pedicle screw placement for L1 vertebral fracture stabilization. METHODS: We studied a male volunteer (26 years old) with no history of chronic back pain or lumbar spine trauma. We used the finite element method for this investigation. Using finite element software, we created a three-dimensional model of L1 vertebral compression fracture. We also constructed models for four percutaneous pedicle screws spanning the fractured vertebra and four screws traversing the damaged vertebra with transverse fixation. RESULTS: In all three-dimensional movement directions, the open pedicle fixation system experienced maximum stress higher than its percutaneous counterpart. With axial spinal rotation, von Mises stress on the traditional open pedicle screw was considerably lower than that with percutaneous pedicle fixation, but peak stress was elevated at the transverse connection. Traditional open pedicle fixation displayed less maximum displacement than percutaneous pedicle internal fixation. CONCLUSIONS: During axial spinal movements, high peak stress is observed at the transverse connection. Patients should avoid excessive axial rotation of the spine during recovery.

Complications analysis of Ilizarov bone transport technique in the treatment of tibial bone defects-a retrospective study of 199 cases.

BACKGROUND: The clinical treatment of long bone defets in the extremities caused by trauma, infection, tumours, and nonunion has been a challenge for orthopaedic surgeons. Bone transport techniques have become the only way to treat such bone defects. However, inevitable difficulties and complications related to bone transport techniques have been reported in many studies. AIM: The purpose of this study was to investigate the risk factors for complications and the effectiveness of the Ilizarov bone transport technique in the treatment of tibial bone defects. METHODS: The study was conducted in 199 patients who underwent treatment with the Ilizarov bone transport technique at our institution from May 2012 to September 2019. Patient demographic data, complications and clinical outcomes after a minimum of 2 years of follow-up were collected and retrospectively analysed. Additionally, a risk factor analysis was performed for the top three major complications. The clinical outcomes were evaluated using the Association for the Study and Application of the Method of Ilizarov (ASAMI) criteria at the last clinical follow-up. RESULTS: A total of 199 patients underwent follow-up for 12-40 months, with an average of 23.5 months, and all achieved bone healing. A total of 310 complications occurred, with an average of 1.04 minor complications and 0.48 major complications per patient. The top three complications were pin tract infection in 48 cases (61.3%), axial deviation in 86 cases (43.2%), and delayed union in 50 cases (25.13%). Multivariate analysis showed that the bone defect length (P = 0.02, OR = 5.489), the number of previous surgeries (P = 0.003, OR = 2.204), and the external fixation index (P = 0.01, OR = 1.202) were significantly correlated with pin tract infection. Bone defects of the middle 1/3 (P < 0.001, OR = 23.769), the bone defect length (P < 0.001, OR = 2.776), and the external fixation index (P < 0.001, OR = 1.154) were significantly correlated with axial deviation. The bone defect length (P = 0.003, OR = 1.242), soft tissue defects (P = 0.013, OR = 0.312) and bone defects of the distal 1/3 (P = 0.023, OR = 4.257) were significantly correlated with delayed healing. The ASAMI bone score at the last follow-up showed a rate of excellent and good bone results of 95.48% and a rate of excellent functional results of 87.94%. CONCLUSION: The Ilizarov bone transfer technique is an effective method for treating tibial bone defects, and shortening the treatment period can reduce the incidence of complications. Older patients and those with longer bone defects, a higher external fixation index, more previous operations, and defects of the middle and distal 1/3 had a higher incidence of complications.

Finite element analysis of minimally invasive nail placement and traditional nail placement in the treatment of lumbar 1 vertebral compression fracture.

Using the finite element analysis method to help us better understand the biomechanical changes of the spine after surgery and the changes in the stress distribution around the screw implantation area. The finite element model of L1 vertebral compression fracture was constructed by using a large number of finite element programs. On the fracture model, 2 kinds of internal fixation devices are set up, namely: the first type of 4 screws across the injured vertebra through the adjacent upper and lower vertebrae + transverse connector; the second type of 4 screws crosses the injured vertebra through the adjacent upper and lower vertebrae + non-transverse connector. To study the distribution of the maximum displacement and von Mises stress of the intramedullary pedicle screws and rods of the 2 types of internal fixation devices after implantation in the spine under certain loading conditions. In traditional open pedicle screw fixation, the maximum stress in the pedicle screw fixation system in the direction of 3D movement is higher than in percutaneous pedicle screw fixation. There is no significant difference in the Von Mises stress of the pedicle screw between the 2 procedures when the spine performs flexion-extension and lateral flexion activities. When the spine is rotating axially, the Von Mises stress of the pedicle screw in conventional open surgery is significantly less than that of the screw in percutaneous pedicle screw fixation. Traditional open internal fixation produces stress peaks of 891.7 MPa and 886.34 MPa at the transverse joint during axial rotation. Only when the spine is rotating in the axial direction, the maximum displacement of traditional open pedicle screw fixation is smaller than that of percutaneous pedicle screw fixation. There is no significant difference in the maximum displacement between the 2 procedures when the spine is moving in other directions. Traditional open pedicle screw fixation can strengthen the stability of the spine in the direction of axial rotation, and can also be greater to reduce the maximum stress of the pedicle screw axial rotation, so the clinical treatment of unstable fractures of the thoracolumbar spine instability is of great significance.