Percutaneous vertebroplasty
Percutaneous vertebroplasty is a minimally invasive spine surgery technique that involves the percutaneous injection of bone cement into the vertebral body through the pedicle or external pedicle to increase strength and stability, prevent collapse, relieve pain, and even partially restore the height of the vertebral body.
History and Current Status
Percutaneous vertebroplasty (PVP) is a minimally invasive spine surgery technique in which cement is injected percutaneously into the vertebral body through the pedicle or externally into the vertebral body to increase strength and stability, prevent collapse, relieve pain, and even partially restore the height of the vertebral body.
Vertebroplasty has been used for decades as an open procedure to augment the pedicle screw and to fill the defect left after tumor removal. The procedure involves injecting bone tissue or bone cement into the vertebral body to mechanically strengthen its structure. In some cases, the risks of open surgery were too great and stopped the doctor and patient in their tracks, thus the emergence of percutaneous vertebroplasty (PVP). Percutaneous vertebroplasty inherits the advantages of vertebroplasty without the complications associated with open surgery. This procedure was first performed by Galibert and Deramond at the Department of Medical Radiology, University of Amiens, France, in 1984, where percutaneous injection of cemented polymethyl-methacrylate PMMA successfully treated a patient with a cervical 2 vertebral hemangioma, pioneering percutaneous vertebroplasty. Using a slightly modified technique (18G), neuroradiologists and neurosurgeons at the University Hospital of Lyon, France, injected bone cement into the vertebral bodies of seven patients, two of whom had vertebral hemangiomas (VHs), one had a metastatic spinal tumor, and four had osteoporotic vertebral compression fractures. In 1989, Kaemmerlen et al. reported the use of this technique for the treatment of vertebral metastases. 16 of 20 patients with vertebral metastases achieved significant results, 2 were ineffective, and 2 had complications. The authors concluded that painful osteolytic metastases without periprosthetic invasion are one of the best indications for percutaneous vertebroplasty.
PVP (applying Deramond’s method) was first introduced to the United States by the University of Virginia in 1994. Since then, PVP has become a common treatment for painful vertebral disorders. In recent years the use of percutaneous vertebroplasty has gradually spread and is more commonly used in patients with osteoporotic vertebral compression fractures with intractable pain, in addition to spinal hemangiomas, myeloma, and osteolytic metastases. As the survival time of patients with tumor metastases increases, so does their quality of life and the requirement to be able to be active in the final stages of the disease. In patients with spinal metastases, PVP has been reported to relieve pain and structurally strengthen the osteolytically damaged vertebrae, allowing patients to experience less pain and to continue daily weight-bearing activities. European experience has focused on the treatment of tumor-related pain (both benign and malignant), while American experience has focused on the treatment of pain associated with osteoporotic compression fractures. Percutaneous kyphoplasty (PKP) is a modification and development of percutaneous kyphoplasty. In 1999, Mark Reiley, a Berkeley orthopaedic surgeon, developed an expandable expansion balloon (KyphXTM , Inflatable Bone Tamp), which This technique uses a percutaneous puncture of the vertebral body to reposition the vertebral body and create a space inside the vertebral body, which reduces the pushing force required to inject the bone cement and makes it less likely to flow when placed inside. Compared with conventional methods, there is no difference in biomechanical properties between the two, and clinical application shows that it not only relieves or alleviates pain symptoms, but also significantly restores the height of the compressed vertebral body, increases the stiffness and strength of the vertebral body, restores the physiological curvature of the spine, and increases the volume of the thoracoabdominal cavity and improves the function of the organs, thus improving the quality of life of patients.
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. safety have been recognized by the majority of physicians and patients.
Mechanisms
1, enhance the strength of the vertebral body: Bo et al.’s biomechanical tests on vertebral specimens from 40 fresh osteoporotic patients 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. The PMMA group was 1036±100N and 156±8N/mm, respectively, and CT examination showed good intravertebral cement filling, 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, with the strength reaching up to twice the normal level and the stiffness exceeding about 15% of the original level; filling the fracture gap and intravertebral space with CPC after vertebral fracture can also restore the strength and stiffness of the vertebral body, increasing the strength and stiffness of the vertebral body, respectively. The strength and stiffness of the vertebral body can be restored by 16.67% (±0.05) and 11.05% (±0.05), respectively.
2. Alteration of vertebral stability: Mermelstein found that after vertebroplasty for compression fractures in osteoporotic patients, the compliance of the vertebral motion segments in which they were located was significantly reduced compared to the preoperative period, with flexion-extension and lateral bending compliance decreasing by 23% and 26%, respectively, but Kifune’s study showed that after a vertebral compression fracture, flexion-extension and lateral bending compliance increased by 34% 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 in burst fractures, calcium phosphate vertebroplasty, and calcium phosphate significantly increased the stability of the anterior column, reduced the stress acting on the pedicle, and ultimately resulted in 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 may lead to disc degeneration or fracture of the adjacent vertebral body. Studies have shown that after a change in vertebral body strength, excessive stiffness can, to a certain extent, cause redistribution of the spinal stress and displacement fields, but strengthening the vertebral body with CPC has no significant effect on the stress of the adjacent vertebral body, and the effect on the adjacent discs is also small.
3. Relief of spinal pain: Minute fractures of the vertebral body and micro-movement of the fracture line cause stimulation of the nerve endings in the vertebral body causing pain, and percutaneous vertebroplasty can produce excellent pain relief in this case. In this sense, percutaneous vertebroplasty is a fracture repair technique, not just a simple filling of the vertebral body. Almost all clinical results show pain relief rates of more than 90% in patients with either osteoporotic compression fractures or old thoracolumbar fractures, for reasons for which there is no definite explanation, probably because (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 micromovement of the fracture line on the nerves within the vertebral body (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 last factor, but later it was found that calcium phosphate vertebroplasty could also achieve the same pain relief effect, so the damage to the nerve endings was not the only factor. 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.
4.Indications and contraindications.
(1) Indications: Vertebral body tumor is the earliest target of percutaneous vertebroplasty and has achieved very good results. Its applicable objects are mainly
vertebral hemangioma
bone marrow tumors
primary and metastatic malignant tumors of the vertebral body
Partial benign vertebral tumors
Benign tumors of the vertebral body are indicated by benign tumors that cause 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 malignant tumors of the spine 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 to 14 days after the start of radiation therapy, and radiation therapy weakens bone reconstruction, which often starts only 2 to 4 months after radiation therapy, and patients with myeloma have an increased risk of nerve compression due to easy collapse of the vertebral body after radiation therapy. PVP can immediately relieve the pain, increase the strength and stability of the spine, and at the same time correct the posterior convexity deformity caused by the collapse of the vertebral body, which greatly improves the quality of life of tumor patients and is conducive to further chemotherapy and radiotherapy.
(2) Absolute contraindications.
a. Uncorrected coagulation disorder and bleeding body.
b. Allergy to any items required for surgery.
(3) Relative contraindications.
a, pain of a radicular nature and significantly exceeding the vertebral body, caused by a compression syndrome unrelated to vertebral body collapse.
b, tumor extension into the epidural space and causing significant spinal canal compression.
c, 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).
d, osteogenic tumors.
e, 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 as follows.
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.