Percutaneous vertebroplasty and percutaneous balloon kyphoplasty are widely performed worldwide. 38,000 percutaneous vertebroplasties and 16,000 percutaneous kyphoplasties were performed in the United States in 2002, mainly for the treatment of osteoporotic vertebral compression fractures, with reported pain relief rates of more than 90%, few serious complications, and their good efficacy and high safety. 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 tests on 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 527.43N and 84.11N/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 the PMMA group was 1036.100N, 156.8N/mm, and CT examination showed good filling of 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 body 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 situation, while the stiffness can exceed about 15% of the original; after the vertebral body fracture, the fracture is filled by the arch root CPC 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, increasing by 16.67% (P<0.05) and 11.05% (P<0.05), respectively.
Altered 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 vertebral compression fractures 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 pedicle screws. mermelstein found a 40% increase in flexion-extension stiffness after internal fixation of the pedicle in burst fractures, calcium phosphate vertebroplasty, and calcium phosphate significantly increased the stability of the anterior column and reduced 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 bodies and has less effect on the adjacent discs.
Relief of spinal pain
In this sense, percutaneous vertebroplasty is a fracture repair technique, not just a simple 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 the following: (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 in 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 the effect of the last factor, but later it was found that calcium phosphate vertebroplasty could 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 the posterior branch of the spinal nerve due to wedge compression of the vertebral body with osteoporosis 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 terms of 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 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 osteoporotic vertebral compression fracture, with the advantages of minimally invasive and little side injury.
2, vertebral body tumor is the earliest use of percutaneous vertebroplasty objects, achieved very good results. Its applicable objects are: vertebral body hemangioma myeloma vertebral body primary and metastatic malignant tumors some benign vertebral body tumors
Benign tumors of the vertebral body are indicated by benign tumors causing pain due to fracture collapse of the vertebral body, including eosinophilic granuloma and vertebral body lymphoma. Malignant tumors of the vertebral body, mainly osteolytic in nature, can be stabilized by intravertebral injection of PMMA in addition to simultaneous biopsy of the tumor tissue for definitive diagnosis.
For vertebral hemangioma, percutaneous vertebroplasty can increase the strength of the vertebral body and provide pain relief and embolization of the tumor; if necessary, posterior decompression of the vertebral plate can be performed without vertebral body resection, which simplifies the surgery. Laredo et al. classified hemangiomas into two categories, invasive and potentially invasive, based on imaging. The main imaging manifestations of hemangioma are irregular fenestrations of vertebral trabeculae, which may involve the entire vertebral body and the vertebral arch, with well-defined or ill-defined margins, which may break through the bone cortex and extend into the epidural space.
Vertebral hemangiomas are divided into the following groups according to clinical and imaging manifestations: (1) hemangiomas with negative invasive signs but painful symptoms; (2) hemangiomas with invasive imaging signs but no clinical symptoms; (3) hemangiomas with both invasive imaging signs and clinical symptoms; and (4) hemangiomas with invasive imaging features and spinal nerve compression symptoms. The first group is the selective indication for PVP, and Deramond et al. reported that 90% of the cases were relieved and no recurrence of the hemangioma was found; the second group is the best indication for PVP; the third group of hemangiomas should be injected with anhydrous alcohol instead of bone cement to harden the hemangioma and strengthen the weight-bearing capacity of the vertebral body, and most of the patients’ neurological symptoms gradually disappeared, and some cases can be found on imaging follow-up The epidural mass disappears in some cases; PVP for group IV hemangiomas is only an adjunct. Intra-lesional injection of N-butyl cyanoacrylate resin into the PVP lesion one day before the conventional surgery embolizes the hemangioma, reduces intraoperative bleeding, and makes the surgical operation easy to perform.
Metastases and myeloma are the most common osteolytic malignancies of the spine, often causing severe back pain and loss of mobility. Treatment depends on the number and location of affected vertebrae, the degree of intradural involvement, the presence of neurological symptoms, the general condition of the patient, the degree of pain, and the degree of mobility restriction. The best indications for PVP in spinal malignancies are severe localized pain caused by malignant tumors, restriction of movement requiring bed rest, relief by pain medication, and absence of intradural dural structure invasion. In case of compression fracture of the vertebral body, the vertebral body should be at least 1/3 of its normal height and the posterior cortex of the vertebral body should not be intact. Because of the tendency of vertebral malignancies to develop compression fractures, PVP therapy is a better approach even if the patient is asymptomatic. According to the data, more than 80% of the patients with PVP treatment had obvious relief of symptoms and improved quality of life. The application of PVP for vertebral malignancies can be followed by adjuvant radiotherapy to consolidate the efficacy, because radiotherapy does not affect the physical and chemical properties of bone cement.
Myeloma is often multifocal and multi-segmental resection and fusion is not possible. 90% of patients have pain relief or elimination only 10-14 days after the start of radiotherapy, and radiotherapy weakens bone reconstruction, which often starts only 2-4 months after radiotherapy, and patients with myeloma have an increased risk of nerve compression due to easy collapse of the vertebral body after radiotherapy. PVP provides immediate pain relief and increases the strength and stability of the spine, while PVP can immediately relieve pain, increase the strength and stability of the spine, and at the same time correct the posterior convexity deformity caused by vertebral collapse, which greatly improves the quality of life of tumor patients and facilitates further chemotherapy and radiotherapy.
Absolute contraindications.
(1) Uncorrected coagulation disorder and bleeding body.
(2) Allergy to any items required for the procedure.
Relative contraindications.
(1) pain that is radicular and significantly exceeds that of the vertebral body, caused by a compression syndrome unrelated to vertebral body collapse; (2) tumor extension into the epidural space and causing significant spinal canal compression
(3) Difficulty in vertebroplasty operation when there is extensive destruction of the vertebral body or severe vertebral body collapse (vertebral body height is less than 1/3 of the original height).
(4) Osteogenic tumors.
(5) simultaneous treatment of 3 or more segments at a time.
In the United States, percutaneous vertebroplasty and kyphoplasty are more commonly used in patients with osteoporotic vertebral fractures. They are described in detail below.
Indications.
(1) Painful osteoporotic vertebral compression fractures that have failed to respond to pharmacologic therapy.
(2) Painful vertebral fractures associated with osteonecrosis.
(3) Unstable compression fractures.
(4) multiple osteoporotic vertebral compression fractures resulting in posterior convexity deformity and causing effects on pulmonary function, gastrointestinal function and altered center of gravity
(5) chronic traumatic fractures with nonunion or internal cystic changes
(6) Acute traumatic fractures without neurological symptoms.
Absolute contraindications.
(1) Asymptomatic stable fractures.
(2) Patients with significant improvement after pharmacologic treatment.
(3) Prophylactic treatment in patients without evidence of acute fracture.
(4) Uncorrected coagulation disorder and bleeding body.
(5) Target vertebrae with osteomyelitis.
(6) Hypersensitivity to any of the items required for the procedure.
Relative contraindications.
(1) Pain that is radicular and significantly exceeds that of the vertebral body, caused by a compression syndrome unrelated to vertebral body collapse.
(2) Retraction of the fracture mass causing significant spinal canal compression.
(3) Severe vertebral collapse.
(4) Stable fractures without pain and with a duration of more than 2 years.
(5) Three or more segments treated simultaneously at one time.