Patient Female, 78, osteoporotic L3 vertebral compression fracture, history of lumbar pain for 3 months with no significant effect of medication, was treated with percutaneous balloon-split cemented vertebroplasty, and the pain resolved the day after the procedure by sitting up and getting out of bed. In 2002, 38,000 percutaneous vertebroplasty and 16,000 percutaneous kyphoplasty procedures were performed in the United States, mainly for the treatment of osteoporotic vertebral compression fractures, with reported pain relief rates exceeding 90% and few serious complications. Their good efficacy and high safety have been recognized by the majority of doctors and patients. Mechanism of action Enhancement of vertebral body strength Change of vertebral body stability Relief of spinal pain Enhancement of vertebral body strength Biomechanical testing of vertebral specimens from 40 fresh osteoporotic patients by Bo et al. showed that the axial compression strength and stiffness of the vertebral body after compression fracture were 527.43 N and 84.11 N/mm, respectively; while the test results after intravertebral injection of calcium phosphate or PMMA showed that the calcium phosphate group was 1063.127N and 157.21N/mm, respectively, and 1036.100N and 156.8N/mm, respectively, in the PMMA group. CT examination showed good filling of the bone cement in the vertebral body, except for the posterior part of the vertebral body, which was 85-95% filled in the calcium phosphate group and 79-90% filled in the PMMA group. It has been shown that intravertebral injection of self-curing calcium phosphate cement (CPC) can significantly restore the mechanical properties of the fractured vertebral body, and the degree of restoration is related to the amount of injected bone cement, and its strength can reach up to two times of the normal condition, while the stiffness can exceed about 15% of the original; after vertebral fracture, the fracture is filled with CPC via the pedicle. The strength and stiffness of the vertebral body can also be restored by filling the fracture space and the intravertebral space with CPC after vertebral fracture, with an increase of 16.67% (P < 0.05) and 11.05% (P < 0.05), respectively. Modification of vertebral stability Mermelstein found that after vertebroplasty for compression fractures in osteoporotic patients, the compliance of the vertebral motion segment was significantly reduced compared to the preoperative period, with a 23% and 26% reduction in flexion-extension and lateral bending compliance, respectively, but Kifune's study showed a 34% increase in flexion-extension and lateral bending compliance after a vertebral compression fracture compared to the pre-fracture period. Biomechanical experiments on cadaveric specimens have shown that self-curing artificial bone cement injected into the diseased vertebrae via the pedicle immediately reduces the stress on the pedicle screws.Mermelstein found a 40% increase in flexion-extension stiffness after internal fixation of the pedicle and calcium phosphate vertebroplasty for burst fractures.Calcium phosphate significantly increases the stability of the anterior column and reduces the stress acting on the pedicle, ultimately causing osteoporotic, burst fractures and enhanced stability after internal arch fixation. Although the results of the studies vary, they all show that vertebroplasty has a significant effect on the stability of the spinal segments in patients with vertebral compression fractures. An additional problem that may occur with increased strength and altered rigidity of the vertebral body after vertebroplasty is the increased loading of the upper and lower discs (more pronounced in the upper disc), which can lead to disc degeneration or fracture of the adjacent vertebral body. Studies have shown that excessive stiffness following a change in vertebral body strength can, to some extent, cause a redistribution of the spinal stress and displacement fields, but strengthening of the vertebral body with CPC has no significant effect on the stresses in the adjacent vertebral body and has less effect on the adjacent discs. Pain relief in the spine Minute fractures of the vertebral body and micro-movement of the fracture line cause irritation of the nerve endings in the vertebral body causing pain, and percutaneous vertebroplasty can produce excellent pain relief in this case, in the sense that percutaneous vertebroplasty is a fracture repair technique and not just a mere filling of the vertebral body. Almost all clinical results show a pain relief rate of more than 90% in patients with either osteoporotic compression fractures or old thoracolumbar fractures, for reasons that have not yet been definitely explained and may lie in: (1) microfractures within the vertebral body are stabilized after vertebroplasty; (2) the bone cement takes up a significant portion of the axial stress, thus reducing the irritation of the nerves within the vertebral body by micromovements of the fracture line; (3) The sensory nerve endings within the vertebral body are destroyed. Because of the exothermic and toxic effects of PMMA, which may damage the nerve endings in the bone, many people initially thought that the pain relief after PMMA vertebroplasty was mainly due to this last factor, but later it was found that calcium phosphate vertebroplasty could also achieve the same pain-relieving effect, so it can be seen that the damage effect on the nerve endings is not the only factor, and the previously thought explanation of pain caused by wedge compression of the vertebral body with osteoporosis causing the posterior branch of the spinal nerve The explanation of pain caused by distension of the posterior branch of the spinal nerve due to wedge compression of the vertebral body cannot be ruled out either. In China, Po et al. found a large distribution of posterior spinal nerve fibers in vertebrae, intervertebral discs and small joints of osteoporotic rats, which may be related to instability. In vertebral tumors, after injecting bone cement, its mechanical effect can interrupt local blood flow, and its chemical toxic effect and polymerization heat can also cause necrosis of nerve endings in tumor tissues and their surrounding tissues to achieve the effect of pain relief, and it even has the effect of killing tumor cells to some extent in a sense. Indications: 1. vertebral compression fracture low back pain posterior protrusion deformity, especially suitable for elderly patients with osteoporosis vertebral compression fracture, with the advantages of minimally invasive, small side injury. 2. vertebral tumor is the earliest use of percutaneous vertebroplasty objects, achieved very good results. The main targets are: vertebral body hemangioma myeloma vertebral body primary and metastatic malignant tumors some benign vertebral body tumors benign vertebral body tumors are indicated by benign tumors causing pain due to fracture collapse of the vertebral body, including eosinophilic granuloma, vertebral body lymphoma, etc. Malignant tumors of the vertebral body, mainly osteolytic, can be stabilized by intravertebral injection of PMMA, in addition to simultaneous biopsy of the tumor tissue for a definitive diagnosis.