Study on the mechanism of biomechanical stress rebalancing at the bone tissue-bone cement interface after reinforcement of osteoporotic vertebral compression fracture based on finite element method

English Keywords:Osteoporotic vertebral compression fracture  Finite element analysis  Vertebral reinforcement  Bone interface  Biomechanical balance

English Abstract:

  【Abstract】 Objectives: To clarify the biomechanical stress rebalancing mechanism at the bone tissue-cement interface and the dynamic stability reconstruction effect on the spine after cement reinforcement treatment of osteoporotic vertebral compression fractures(OVCF). Methods: An OVCF patient(injured vertebrae, T12 and L1) treated in the Department of Spine Surgery of the Affiliated Hospital of Gansu University of Traditional Chinese Medicine was selected as the object of study, and thin-layer, high-precision thoracic and lumbar vertebral CT imaging data of the patient was extracted. A 3D digitally simulated biomechanical model was established through the finite-element biomechanical modeling platforms of Mimics, Geomagic, Solidworks, and Ansys Workbench, in order to quantitatively study the equivalent stress at bone tissue-cement interface of motion segment of the injured vertebral body under different motion conditions such as axial, flexion, extension, lateral bending, and rotation. Results: The extreme value and distribution range of equivalent stress at the bone tissue-bone cement interface after spinal OVCF were significantly optimized compared with those before surgery. Under the motion conditions of axial, forward flexion, posterior extension, lateral bending and rotation conditions, the maximum principal stress after spinal cement reinforcement for T12 vertebra decreased significantly compared with that before surgery, which was 33.002MPa, 35.639MPa, 35.98MPa, 60.458MPa, 65.396MPa, 60.177MPa, and 42.249MPa under the same working conditions, especially under the forward flexion working conditions, the maximum principal stress of T12 decreased from 77.995MPa before surgery to 35.639MPa after surgery; Under the same motion conditions, the maximum principal stress of L1 vertebra after reinforcement treatment was 24.911MPa, 34.705MPa, 26.514MPa, 60.144MPa, 32.797MPa, 30.259MPa, and 32.894MPa, respectively, and under axial and forward flexion conditions, the maximum principal stress of L1 vertebra decreased from 74.798MPa and 99.232MPa before surgery to 24.911MPa and 34.705MPa after surgery. The maximum principal stress at T12 and L1 bone cement interface distributed evenly. The extreme value of principal stress at T12 cancellous bone was 1.004MPa to 3.0758MPa, which at L1 cancellous bone was 1.8075MPa to 2.3355MPa. The stress distribution cloud map showed that the stress distribution at bone interface shifted to the middle and posterior columns after the reinforcement treatment, and the stress concentration was corrected. The stress distribution at the bone tissue-bone cement interface tended to be balanced and stabilized. Conclusions: The dynamic biomechanical stability of the spine is reconstructed after cemented reinforcement of the injured vertebrae in the thoracolumbar segment, and the biomechanical stress-strain stimulus at the bone tissue-cement interface is significantly decreased compared with the preoperative period, and the stresses are distributed evenly, which reconstruct the stress rebalancing at the bone tissue-cement interface.