With the aging of the population, osteoporosis has become a common disease and is prone to fractures in various areas, with the vertebral body being the most vulnerable site for fractures. It is estimated that there are about 1.4 million new vertebral compression fractures due to osteoporosis worldwide each year, of which about 1/3 have severe back pain and limited mobility, which seriously affects the quality of life. The traditional treatment for Osteoporotic vertebral compression fractures (OVCFs) is bed rest + medication for pain relief, and about 60-80% of patients can gradually reduce their back pain after 2-3 months, but the back pain lasts for 3-6 months after sitting and walking, and some patients have severe back pain that lasts longer or is difficult to relieve. OVCFs patients will be left with acute or chronic thoracic and low back pain, kyphoscoliosis, reduced thoracoabdominal volume, and restricted visceral function, which, combined with pain, motor impairment, or prolonged bed rest, are prone to various complications, such as deterioration of mental status, infection, deep vein thrombosis, and death from organ failure, thus OVCFs have become one of the common diseases that seriously affect people’s quality of life.
In 1987, Galibert et al. first reported the use of percutaneous vertebral body puncture injection of bone cement (Polymethylmethacrylate, PMMA) to treat seven cases of vertebral hemangioma with significant pain relief, thus pioneering percutaneous vertebroplasty (PVP). 1991 Debussche-Depriester reported five cases of PVP for the treatment of pain in OVCFs, and all patients experienced complete pain relief immediately after surgery. In 1997, Jensen [4] reported PVP in 29 cases with 47 OVCFs, with an immediate pain relief rate of more than 90%. Subsequently, case reports on PVP have been published in the literature, all of which achieved good pain relief, stable long-term efficacy and very few complications. In 2000, Prof. Teng Gaojun and others were the first to perform percutaneous vertebroplasty in China and held the first national course, and then this technique was gradually promoted in China, with more than 1000 Chinese articles available to date.
I. Mechanism of percutaneous vertebroplasty
PVP is performed by injecting PMMA into the diseased vertebral body after puncturing it with a bone puncture needle under fluoroscopic surveillance, so as to achieve therapeutic purposes, the main function of which is to relieve or alleviate pain, strengthen the vertebral body and prevent further compression and collapse of the vertebral body. The pain relief mechanism is as follows: 1. PMMA strengthens the vertebral body, reduces the pressure of the collapsed vertebral body, and stabilizes the microfracture in the compressed vertebral body, reducing the movement of the fracture end, thus reducing the stimulation of the nociceptive nerve endings; 2. PMMA mechanically blocks the blood supply to the local tissues and the heat during polymerization, resulting in the necrosis of the nociceptive nerve endings.
II. Filling materials and their physicochemical properties
At present, the commonly used filling material is bone cement, i.e., polymethyl methacrylate, which is a polymer of acrylic acid (powder) and monomer (liquid) mixed in a certain ratio and then polymerized and cured into a high strength polymer compound, and there is a transient heat production in the polymerization process, and the maximum temperature can reach 74℃. Commercially available PMMA is white powder 40g/bag + 1 20ml blending liquid (monomer). Generally the powder: liquid is 2:1 blending, that is, 20g powder + 10ml blending liquid, its polymerization process is roughly divided into three phases, 1. thin stage: powder and liquid quickly blended, in the beginning of 2 minutes was thin liquid; 2. viscous stage: powder and liquid mixed about 2-3 minutes PMMA began to become viscous, a paste to raw dough-like, about 3-5 minutes, to be injected into the PMMA within this phase vertebrae, beyond this stage it is very difficult to inject; 3. hardening stage: after about 7-10 minutes of powder-liquid mixing, PMMA becomes hard and fixed, and a transient heat production. haas et al [19] proposed the following possible measures to reduce heat production after experiments: ① prior to the PMMA powder at 0°C, the heat production temperature can be significantly reduced during modulation; ② increase the powder:liquid ratio, such as from 2:1 to 3:1 is can be reduced to 10℃. When the ambient temperature is low, the PMMA polymerization time will be prolonged, and vice versa will be shortened. It should be noted that the polymerization process of PMMA produced by different manufacturers is different, and the time division of the above polymerization process is the result measured by Tenggaojun and He Shicheng [16] using UK Corinplasty 3 PMMA at an ambient temperature of 20~25°C. It is recommended that the initial PVP should first master the different blending methods and polymerization process of PMMA before PVP is carried out. The PMMA itself is almost invisible under X-ray.
PMMA itself almost does not develop under X-ray, most manufacturers have added 10% barium powder in the powder, but the PVP intraoperative fluoroscopic development is still not good. In order to enhance the development, in Europe more molybdenum powder or tungsten powder, such as 20g PMMA powder + 1.5g tantalum powder. In the United States, barium powder is mostly used, and the general amount of barium powder added is about 30%. He Shicheng et al [17] added sterilized pure barium powder to Corinplasty 3 PMMA, and blended it according to PMMA 15g + barium powder 3g + monomer 10ml, that is, the barium powder content reaches 30%, which makes it stronger under fluoroscopy, and the clinical application of more than 400 cases confirmed that it has no effect on the efficacy.
Third, the indications and contraindications of PVP for the treatment of OVCF
Early scholars who engaged in PVP believed that OVCF patients must have pain that cannot be relieved after 4 weeks of conservative treatment or to prevent complications that may arise from long-term bed rest, and that PVP can be performed only if other causes of pain, such as lumbar disc herniation, are excluded by MRI or CT examination, or to prevent decubitus ulcers and physical condition failure, which can be performed as soon as possible in patients over 80 years of age with severe back pain lasting 1 to 2 weeks. In the past 10 years, more and more scholars believe that once OVCF is clearly identified, there is no need to wait for conservative treatment and PVP can be performed as early as possible, which not only can rapidly relieve patients with severe back pain, but also can significantly shorten bed rest time, improve quality of life and prevent further collapse of the vertebral body. For osteoporosis without low back pain, prophylactic PVP is not currently advocated. because fresh compression fractures of the vertebral body and fractures that are difficult to heal are the cause and site of low back pain, there are obvious signs of bone marrow edema on MRI, showing T1W low signal and T2W high signal, which can accurately identify old and new fractures and determine the degree of compression of the vertebral body. For multiple compression fractures of adjacent vertebrae, previous history of vertebral compression fracture and clinical signs are difficult to clarify painful vertebrae, MRI should be performed because old compression is painless without PVP. CT can understand whether the bone cortex is intact at the edge of the compressed vertebral body, whether there is bone destruction, and can observe the anatomy of the puncture pathway, etc. In recent years, CT sagittal and coronal two-dimensional reconstruction can accurately display the vertebral body X-ray plain films can show osteoporosis, compression and collapse of the vertebral body, etc. However, both CT and X-ray plain films can show the degree of compression of the vertebral body and the presence of free bone fragments in the spinal canal. However, both CT and radiographs cannot distinguish between fresh and old compression, so it is difficult to accurately identify the painful vertebrae and their locations, which may lead to missed diagnosis and treatment. Nuclear scan shows that there is nucleus accretion in fresh compression of the vertebral body, but there is no accretion in normal and old compression, so fresh and old compression can be distinguished, but it is easy to misdiagnose as vertebral metastases. Therefore, MRI and CT are mandatory imaging examinations before PVP for OVCFs.
Absolute contraindications include vertebral tuberculosis or other infections, dyspnea with difficulty in prone positioning, and expected survival <2 months. Those with vertebral compression of more than 75% and those with bleeding tendency due to bleeding disorders can be considered as present contraindications.
IV. POV operation
To ensure intraoperative bi-directional positioning, a C-arm X-ray machine is a necessary image-guided device. PMMA syringes include Murphy Quick 1.0ml syringes from Cook, and rotary pressure syringes from Optimed and Crown Dragon. The author has been using Murphy Quick 1.0ml syringe for a long time and believes that it is easy to use, easy to inject and inexpensive, but the disadvantage is that the operator is too close to the bulb and the amount of radiation is high. The rotary syringe, on the other hand, is expensive and single-use. When the puncture needle penetrates into the cortex of the vertebral arch, it is easy to control the needle direction, force and depth of penetration by tapping with a surgical hammer.
Thoracic and lumbar puncture are advocated to use the needle through the arch, and cardiac monitoring should be done throughout. The specific procedure is: ① the patient is in a prone position, routinely disinfected and toweled® ② under standard orthoptic fluoroscopy, the outer edge of the vertebral arch is selected 1~2 cm lateral to the body projection as the puncture point® ③ with 2% lidocaine in the skin of the puncture point in the direction of the vertebral arch as a puncture channel full layer infiltration anesthesia® ④ take the bone puncture along the vertebral arch, under lateral fluoroscopy the puncture needle direction as much as possible to adjust with the When the head end of the puncture needle reaches the posterior edge of the vertebral body, the orthoptic fluoroscopy shows that the puncture needle just crosses the inner edge of the vertebral arch, which is the ideal state of puncture, and the puncture needle is advanced to the junction of the anterior 1/3 of the vertebral body under the lateral fluoroscopy, at which time the head end of the puncture needle can be seen in the center of the vertebral body in the orthoptic position®⑤ Reconciliation of bone cement to The injection volume is generally about 3.7 ml in the thoracic spine and 4.8 ml in the lumbar spine.®⑥Place the needle core to push the PMMA remaining in the puncture needle tube into the vertebral body and then rotate the needle to withdraw the puncture needle.
V. Efficacy evaluation
Most of the literature reports that the efficacy evaluation of PVP is mainly to observe the pain relief, and the visual analogue scale (VAS) is commonly used to evaluate the pain relief, by drawing a 10 cm long straight line and dividing it into 10 equal points, with “no pain” and “severe pain” at the two ends of the line respectively. Perez-Higueras et al [21] reported a 5-year prospective follow-up study of 13 cases, which showed that the VAS score decreased significantly from 7.8 to -8.0 within 24 hours after PVP. -8.0 significantly decreased to 2.7-3.0 postoperatively, with no statistical difference between time points at 3 days, 3 months, and 5 years postoperatively.Tanigwa et al [22] reported 80 cases of OVCF, in which edema was significant in 44 cases VAS scores decreased rapidly from 7.5 pre-PVP to 2.9 1-3 days postoperatively, an In 72 cases prospectively evaluated by He Shicheng et al, the mean VAS score decreased rapidly from 8.53 before PVP to 3.22 at 24 hours postoperatively, an improvement of 5.31, and the VAS values at 1 month, 3 months, 6 months and >1 year postoperatively were 3.06, 2.06, 1.61 and 1.24, respectively, indicating that PVP can rapidly relieve pain, and the decrease in VAS values at 24 hours postoperatively was The most significant decrease in VAS values was observed after 3 months, and remained stable after 6 months and 1 year.
The quality of life scales such as Activity of Daily Life (ADL) and Oswestry disability index (ODI) have been reported in the literature to evaluate the improvement of mobility, symptoms, recovery of function and prevention of disability after PVP. Diamond et al [15] reported 88 cases treated with PVP and 38 cases treated conservatively, and the mobility of the PVP group improved by 29% at 1 year after surgery, which was significantly higher than that of the conservative treatment group, and the length of hospital stay was significantly shorter in the PVP group. He Shicheng et al [23] reported that the total ADL score in 72 cases increased from 40.5 before PVP to 69.4 at 1 week after surgery, an improvement of 71%, with a significant difference, and the total ADL score still improved significantly at 1 month, 3 months, 6 months and more than 1 year after surgery (P<0.01), while the total mean ODI score decreased from 33.81 before surgery to 20.9 at 1 week after surgery, an improvement of 38%, and the postoperative 1 Winking et al [24] reported 38 cases in which the ODI pain index decreased significantly from 3.7 before PVP to 1.7 2 days after surgery, and remained at 1.6 6 6 weeks after surgery, with no significant difference from 2 days after surgery. After 1 year, the ODI index of about 92% of the patients was still significantly lower than that before the operation, indicating that PVP not only has a quick effect, but also has a long-lasting effect.
In 2003, Hiwatashi et al [25] reported a total of 85 vertebral body heights after PVP in 37 cases. 33 vertebral body heights increased (1 to 3 mm) and 39 increased by more than 3 mm, with a maximum height recovery of 15 mm and average increases of 2.7, 2.8, and 1.4 mm at the anterior, central, and posterior margins, respectively. Teng et al. measured the anterior, middle, and posterior vertebral body heights in 53 cases before and after PVP using digital lateral films in the standing position, and the results showed that the degree of recovery of anterior, central, and posterior edge heights after PVP was 16.7%, 14.5%, and 7.2.0%, respectively. Pitton et al. used CT reconstruction to measure the height of the vertebral body before and after PVP, and the results showed that the anterior and posterior edge heights increased by an average of 1.1, 0.5mm, respectively. Liu Qingwen et al. reported 40 cases of 68-segment OVCF with an average increase of 2.01, 1.78, and 0.44 mm in the height of the anterior, central, and posterior margins of the vertebral body after PVP. The mechanism by which PVP restores the height of the vertebral body in osteoporotic compression fractures may be related to the following two aspects: 1. The spine is in a weight-bearing state in the standing position, especially the anterior 1/2 of the vertebral body is significantly weight-bearing, while the prone position eliminates the In the prone position, weight-bearing is eliminated, and due to the stretching and pulling of the anterior longitudinal ligament, the freshly compressed vertebral body can be restored to different degrees of height, i.e., postural repositioning; 2. PVP injects high-viscosity bone cement into the fractured vertebral body by high pressure and diffusely distributes it in the trabeculae and fracture gap, which widens and reinforces the gap, allowing further height restoration based on postural repositioning.
However, the results of two randomized controlled trials (RCT) in the New England Journal in 2009 showed that OVCF pain did not benefit after PVP over the control group, causing the efficacy of PVP for OVCF to be questioned for a time. In 2010, Klazen et al. reported the results of an RCT of 202 cases of OVCF with PVP and conservative treatment showing that PVP rapidly relieved acute OVCF pain, and the efficacy remained stable over 1 year, significantly better than the conservative treatment group.
VI. Complications
The complications of PVP are mainly due to the leakage of PMMA around the vertebral body and the corresponding compression, and the common leakage sites include the extradural sac in the spinal canal, nerve root canal, paravertebral soft tissue, adjacent intravertebral disc and paravertebral venous plexus, with an incidence of 1-10%, and fortunately, most of them have no clinical symptoms. The leakage rate of early PVP for vertebral tumors is high, mainly due to the unskilled timing of PMMA injection and the incomplete vertebral bone cortex. Weill et al. reported 37 cases of 52 vertebral tumors with post-operative CT confirmation of leakage in 20 segments (39%), and only one case of leakage into the nerve root canal with severe sciatica, which was relieved by surgical removal of the leaking cement. In recent years, the incidence of leakage in OVCF treated with PVP is significantly lower at 1-6%. The rare complications include pulmonary embolism, most of which do not have obvious clinical symptoms, but Monticelli et al. reported one case of severe pulmonary embolism of bone cement and death after PVP. Combined with the literature and the author’s experience, the main measures to prevent PMMA leakage are: (1) injection under close monitoring by lateral fluoroscopy, and stop injection immediately once leakage is detected; (2) injection in the viscous phase; (3) avoiding damage to the endplate of vertebral cartilage at the end of the puncture needle as much as possible.
VII. Comparison of percutaneous vertebroplasty and retroconvex plasty
Percutaneous kyphoplasty (PKP) is a technique developed in the late 1990s on the basis of PVP. Its basic method is the same as PVP, except that after successful puncture, a special balloon tamp is placed into the compressed vertebral body to expand and form a cavity, and then bone cement is injected, which can also achieve more than 90% pain relief in the treatment of OVCF. Rhyne et al. reported that the height of the vertebral body before and after PKP was measured on standing lateral radiographs in 52 cases of osteoporotic vertebral compression fractures with a total of 82 segments. In 2009, Wardlaw et al. reported an RCT study of PKP versus conservative treatment in 300 cases of OVCF, which showed that PKP provided rapid relief of acute OVCF pain and maintained stable efficacy over 1 year, significantly better than the conservative treatment group. In 2004, Nussbaum et al. collected data published in the US FDA online database and reviewed all reports related to PVP and PKP procedures from June 1999 to 2003. 58 reports, and the analysis showed that complications such as PKP leakage and compressed spinal canal paralysis were significantly higher than PVP. Currently, orthopedic surgeons tend to promote the PKP technique, but interventionalists tend to recommend the less invasive, more effective, and less expensive PVP.