Vertebroplasty and Vertebral Kyphoplasty
Vertebroplasty, originally derived from the use of cement or bone implanted directly into the vertebral body via the pedicle or through open surgery to enhance the biomechanical strength of the vertebral body, prevent collapse, and relieve low back pain, was first reported by French neuroradiologists Galibert and Deramond in 1987, who used percutaneous vertebroplasty to successfully treatment of a cavernous hemangioma of the C2 vertebral body in a case of chronic pain.
In 1994, Reiley et al. in California, USA, designed and developed an expandable balloon (also known as an expandable bone pounder), which was inserted percutaneously into the vertebral body and expanded by the balloon to restore the height of the vertebral body and correct the kyphosis, thus the technique was called kyphoplasty. Kyphoplasty was approved for clinical use by the FDA in 1998.
Kyphoplasty is actually a variation of vertebroplasty and is a development of vertebroplasty. In recent years, scholars have begun to conduct research on vertebroplasty and kyphoplasty for the treatment of traumatic thoracolumbar fractures, actively expanding the clinical application of this technique.
Indications and contraindications
The indications for percutaneous vertebroplasty are: vertebral hemangioma, vertebral osteolytic metastases, decreased spinal stability and low back pain due to myeloma; mild to moderate osteoporotic vertebral compression fractures, etc. With the development of technology, the indications for vertebroplasty and vertebral body kyphoplasty have been extended to the treatment of traumatic thoracolumbar fractures, especially burst fractures.
Contraindications include: severe heart and lung disease and coagulation disorders; severe compression fractures (≥50% compression in the upper thoracic spine and ≥75% in the lumbar spine); severe bone destruction at the posterior edge of the vertebral body; fractures of the vertebral arch; and spinal cord and nerve compression due to collapse of the vertebral body or tumor spread.
Technical points
The patient is placed prone on the operating table, and local or general anesthesia is used. Surgical approach: the middle thoracic spine generally adopts the lateral arch-root approach, the thoracolumbar segment generally adopts the trans-arch-root approach, and the lower lumbar spine generally adopts the lateral arch-root approach. The injection site and the location of the puncture needle need to be observed under the guidance of the C-arm machine during the operation.
Vertebroplasty]
The tip of the puncture needle reaching the anterior 1/3 of the vertebral body is the best position. Inject 10~5ml of iodine contrast agent through the puncture needle and perform intravertebral venography to estimate the integrity of the vertebral body and the location of the vertebral venous plexus in order to avoid or reduce the leakage of bone cement into the vein causing embolism or leakage into the vertebral canal. The filling agent is prone to leakage when it is in a liquid state, so it needs to be injected when it is viscous to a thin paste. Stop when resistance is felt to increase or when the filling agent reaches the posterior wall of the vertebral body, and stop as soon as leakage into the epidural space, intervertebral foramen, or venous plexus is detected.
Belkoff et al. showed that the strength of the vertebral body was restored when 2 ml of bone cement was injected bilaterally through the pedicle, and Liebschner et al. concluded that overfilling does not give the best biomechanical results, but rather that the cement should be filled in small amounts and distributed symmetrically.
Tohmeh et al. conducted a comparative study of the biomechanical effects of vertebroplasty with unilateral and bilateral injections of polymethylmethacrylate (PMMA) bone cement for fracture-sparing vertebral compression fractures and showed that the two were similar in terms of stiffness restoration, and in terms of strength restoration, the unilateral injection was less than the bilateral one but still higher than the pre-fracture level, thus concluding that the two were similar in restoring the mechanical properties of the vertebral body The effect is similar. Generally, unilateral or bilateral injections can be performed according to the distribution of the filling agent in the vertebral body, with an average injection volume of 5~10ml per vertebral body.
Vertebral body kyphoplasty]
After the puncture needle is placed in the appropriate position of the vertebral body, the inner core of the puncture needle is withdrawn and a guide needle is placed. The puncture needle is withdrawn, and the expansion cannula and working cannula are placed in order along the guide needle so that the front end of the working cannula is located 2~3mm in front of the cortex at the posterior edge of the vertebral body, and the fine drill is slowly drilled through the working cannula to the anterior edge of the vertebral body, and then the fine drill is removed and an expandable balloon is placed, with the lateral position showing its ideal position at the anterior 3/4 of the vertebral body, tilted from posterior up to anterior down.
The balloon is injected with contrast and expanded, usually at a pressure of no more than 300 psi, and the vertebral body is repositioned to form a cavity within the vertebral body, whereupon the balloon is removed and the filling agent is injected.
However, Steinmann et al. conducted a comparative study of the biomechanics of unilateral and bilateral vertebral kyphoplasty and found that both significantly restored the strength and stiffness of the vertebral body with no significant difference between them, and taking into account the risk of arch root placement, operative time, radiation exposure, and cost, it is recommended that in the treatment of osteoporotic vertebral compression fractures In the treatment of osteoporotic vertebral compression fractures, retrobulbar kyphoplasty via the lateral pedicle route can be used.
A retrospective analysis of recent clinical data suggests that vertebral kyphoplasty is effective in relieving pain, restoring vertebral height, and improving kyphotic deformity in patients with compression fractures, and that unilateral versus bilateral approaches are equally effective in achieving better repositioning of the vertebral body in compression fractures.
Application of vertebroplasty and kyphoplasty in thoracolumbar fractures
[Treatment of osteoporotic vertebral compression fractures].
Osteoporosis is a systemic disease characterized by low bone mass and destruction of bone tissue microstructure, resulting in increased bone fragility, and compression fractures can occur in patients’ vertebrae under the influence of minor external forces. For osteoporotic vertebral compression fractures, traditional treatment is mainly by palliative means, i.e. bed rest, painkillers with calcium, physical therapy, brace support, etc., which is very likely to lead to further bone decalcification and osteoporosis, forming a vicious circle.
The open surgical treatment is also limited by the patient’s osteoporosis and poor general condition. Percutaneous vertebroplasty and vertebral body kyphoplasty, as new minimally invasive procedures for the treatment of osteoporotic thoracolumbar compression fractures, provide rapid pain relief and early functional exercise, making surgical treatment of localized osteoporosis possible and providing time and opportunity for subsequent pharmacological counter-causal treatment of osteoporosis.
In a group of 30 patients treated with vertebroplasty for 44 vertebral compression fractures, Zoarski et al. were followed up for 15 to 18 months in 23 cases, and 22 (96%) were very satisfied with the results, with 21 of these patients indicating that she (he) would like to continue this treatment if another vertebral compression fracture occurs in the future.
McGraw et al. used vertebroplasty to treat 100 cases156 of vertebral compression fractures caused by osteoporosis, and 97 (97%) of them felt a significant reduction in pain 24 h after surgery, and 99 patients were followed up for an average of 21.5 months, with 92 (93%) having satisfactory results and no worsening of symptoms in one case. However, because percutaneous vertebroplasty cannot move the endplate of the fractured vertebral body, it is difficult to restore the height of the vertebral body and improve the kyphosis, and because the injection of low viscosity bone cement into the compressed vertebral body requires high pressure, which may cause risks such as leakage of bone cement.
In contrast, kyphoplasty is a newer and safer treatment method, but it is more expensive than vertebroplasty. Garfin et al. reported that from October 1998 to March 2000, 340 patients with 603 vertebral compression fractures in the United States underwent kyphoplasty within 3 months of onset, and the patients not only experienced pain relief, but also recovered vertebral height, corrected kyphosis, and significantly reduced complications such as cement leakage.
Lieberman et al. performed kyphoplasty on 70 vertebrae in 30 patients with osteoporotic vertebral compression fractures with a mean disease duration of 5.9 months, excluding burst fractures on preoperative MRI, using PMMA as a filling agent, observing changes in vertebral body height on lateral radiographs, and evaluating vertebral body height according to the SF-36 scale (including physical function, functional function, physical pain, general health status, vitality , social function, emotional and mental status, and other 8 items) were scored.
The results showed that cement leakage occurred in 6 vertebral planes, but no major complications related to this technique occurred, and 70% of vertebral body heights were restored at a rate of 47%, with a significant improvement in SF-36 scores after treatment. the study by phillips et al. also showed that vertebral kyphoplasty was effective in improving physiological function, relieving pain, and correcting the The posterior convexity deformity of the spine due to vertebral compression fracture was corrected.
Treatment of traumatic thoracolumbar fractures]
The thoracolumbar spine is the most mobile segment of the spine and most prone to fracture. Due to the short fixed segment, low surgical trauma, satisfactory repositioning, secure fixation, and relatively safe operation, the transperineal internal fixation technique is still considered one of the ideal methods for thoracolumbar fractures. However, posterior surgery fails to restore the height of the injured vertebral body while restoring the compression-damaged trabeculae to their original trabecular structure, resulting in an “eggshell-like” change in the vertebral body.
Especially in burst fractures, endplate rupture often occurs, and the disc and fractured endplate are squeezed into the vertebral body, causing the anterior middle column to lose its structural integrity. The injection of cancellous bone into the vertebral body via the pedicle was once promoted, but some recent studies by Knop and Alanay et al. have shown that this method does not rebuild vertebral strength and stability and does not reduce the incidence of internal fixation failure and loss of correction.
Mermelstein et al. demonstrated through experimental studies that vertebroplasty combined with posterior pedicle screw system repositioning internal fixation and intravertebral injection of calcium phosphate bone cement into the injured vertebral body via the pedicle can effectively enhance the stability of the anterior column of the injured vertebral body. A study by Baoshan Xu and Tianjie Tang in China also showed that the application of calcium phosphate cement for vertebroplasty helped to reconstruct the injured spine, and the biomechanical properties of the postoperative spine were close to the pre-fracture level.
In a group of preliminary clinical application reports, Verlaan et al. reported that in 20 patients with thoracolumbar burst fractures without neurological injury, the injured spine endplates were repositioned via bilateral arch expansion via balloons within 1 week after posterior pedicle screw system repositioning and fixation, and calcium phosphate bone cement was injected afterwards.
The results showed that the calcium phosphate cement was well distributed in the injured vertebral body, and the central and anterior heights of the injured vertebrae were restored by 78% and 91%, respectively, and cement leakage occurred in five cases, but did not cause clinical discomfort. It is a safe and reliable method to restore the height of the vertebral body and reconstruct the boundaries of the intervertebral space without any surgical technical difficulties.
Complications
Vertebroplasty and kyphoplasty are relatively safe procedures, and post-injection leakage is the most common complication. It is generally believed that leakage is caused by the puncture needle breaking through the inner edge of the pedicle or the posterior edge of the vertebral body, over-injecting the amount of bone cement, or the bone cement being too dilute, and the higher the site, the more it occurs. The destination of bone cement leakage is related to the anatomy of the spine, including leakage to the paravertebral soft tissue, intervertebral space, epidural space, intervertebral foramen and vertebral venous plexus.
Leakage of bone cement into the paravertebral soft tissues, although more common, is generally not clinically significant. Leakage of bone cement into the intervertebral space, although not acutely symptomatic, has a mechanical effect on the adjacent vertebral body, potentially increasing its fracture incidence. Leakage into the epidural and intervertebral foramina may produce symptoms of spinal cord and nerve root compression; leakage into the vertebral body or paravertebral veins may cause pulmonary embolism. For leakage of PMMA bone cement, not only compression may occur, but permanent damage to the spinal cord and nerve roots can result due to the exotherm of the bone cement as it polymerizes.
Garfin et al. reviewed the literature that bone cement leakage occurs most frequently in vertebroplasty, ranging from 30% to 67%, and in the treatment of osteoporotic compression fractures, causing nerve root damage in 4% and spinal cord compression in approximately 0.5%. Phillips et al. performed a comparative study of bone cement leakage between vertebroplasty and posterior convexity vertebroplasty for osteoporotic vertebral compression fractures and showed that posterior convexity vertebroplasty The rate of cement leakage was significantly lower with posterior convex plasty.
However, Nussbaum et al. reviewed the complications of vertebroplasty and kyphoplasty reported on the FDA medical device website and found that the thicker trocar used in kyphoplasty could easily damage the vertebral arch and even rupture it, and concluded that kyphoplasty is no less severe than vertebroplasty in terms of complication rate and severity due to cement leakage.
Problems and prospects
Scholars at home and abroad have conducted extensive basic theoretical research and clinical application exploration on vertebroplasty and vertebral body kyphoplasty, showing that they can not only effectively relieve the pain caused by vertebral compression fractures complicated by osteoporosis that is difficult to control by conventional treatment, but also have unique advantages for traumatic thoracolumbar fractures, especially burst fractures, i.e., they are less traumatic and can immediately play a role in stabilizing the spine, so they have a very good application prospects.
However, PMMA bone cement, which is the earliest and most widely used in clinical practice, has the potential to burn the adjacent tissues, especially the spinal cord and nerve roots, due to the high local temperature generated during polymerization, and the monomer is cytotoxic and cannot be replaced by normal bone tissue, which will become a permanent foreign body once injected. Therefore, biodegradable calcium phosphate bone cement with osteoconductivity and histocompatibility is the most studied and considered the most promising, and is a good alternative to PMMA bone cement.
However, animal experiments on long-term biomechanics and biology of calcium phosphate bone cement in vivo and further clinical applications are yet to be observed; it takes a long time to form and will fall off and move due to external forces before forming in body fluids, therefore, further modification studies on it are still needed.
Vertebral body kyphoplasty can restore not only the biomechanical strength of the vertebral body, but also the height of the vertebral body and correct the kyphotic deformity than vertebroplasty. However, the expandable balloon is disposable and expensive, and it is difficult to be popularized in China. It is believed that with the progress and development of science and technology, absorbable and reasonably priced biological balloons and other surgical instruments to restore the height of the vertebral body and prevent leakage of the filling agent will definitely come into being, which will simplify the operation of vertebroplasty for the treatment of thoracolumbar fractures and further promote its application.