I. Basic concept
PVP is the injection of bone cement by percutaneous vertebral puncture under the surveillance of imaging equipment to increase the strength of the vertebral body, stabilize the diseased vertebral body, and prevent the collapse of the vertebral body, thus serving to reduce pain and other effects. Due to the rapid development of interventional equipment in recent years, PKP has been newly developed on the basis of PVP. PKP is based on PVP, in which a balloon is used to expand the collapsed vertebral body and push out the adjacent bone to create a space in the vertebral body, and then bone cement is injected to restore the height of the vertebral body and increase the strength of the vertebral body, thus relieving or alleviating pain and other effects.
Second, the treatment mechanism
Most people believe that the pain-relieving effects of PVP and PKP are related to the following aspects.
1.Bone cement has obvious thermogenic effect in the polymerization stage, especially in the sclerosis stage, up to 82℃, and this thermogenic effect can cause necrosis of some adjacent nerve endings, thus producing analgesic effect.
2.It increases the strength of the vertebral body, especially PKP obviously restores the height of the vertebral body, improves the stability of the vertebral body, reduces the compression symptoms and avoids the appearance of new subtle fractures.
3.The mechanical compression effect produced by the injection of bone cement partially or completely cut off the blood supply to the tumor, thus accelerating the necrosis of the tumor tissue.
4.The simple toxic effect damages the nerve endings, thus reducing the sensitivity of nerve endings and relieving pain.
Indications and contraindications
Currently PVP and PKP are overwhelmingly used for the treatment of vertebral compression fractures caused by various reasons, with the following common primary diseases.
1, osteoporosis: as more than half of the elderly people over 60 years of age have different degrees of osteoporosis, in recent years PVP and PKP treatment is mainly applied to VCF caused by osteoporosis.
2, metastatic tumors.
3, myeloma.
4, invasive hemangioma.
It is worth noting that with the increased analysis of the causes of their clinical efficacy and complications, many authors have proposed more stringent criteria for indications, among which Watts et al. concluded, based on a review of the literature, that the best results are achieved by selecting pain that is limited, significant, and confirmed by X-ray, CT, and MR to be recent or progressive VCF.
It is generally accepted that there are no absolute contraindications to PVP and PKP, while the relative contraindications are.
1, vertebral compression exceeding 75%.
2, burst fractures or involvement of the posterior border of the vertebral body
3, osteogenic metastases.
4, those with coagulation disorders.
5.Severe cardiovascular disease or poor physical condition cannot tolerate the operation.
IV. Sclerotomy materials and equipment
Currently, there are two types of bone cement used for sclerosis: the first type of non-degradable bone cement is the most commonly used, with the advantages of relatively low viscosity, relatively easy injection and good strength recovery, but the heat production effect is more obvious after injection, and the histocompatibility is still not very clear; the second type of degradable bone cement is more used, with the advantages of weaker heat production effect after injection and better biocompatibility, but due to the large viscosity, it is more difficult to inject. However, due to the high viscosity, it is difficult to inject and is less used especially in PVP.
PMMA, which has the most clinical application at present, is not strong due to its impermeability to X-rays, so a certain amount of barium, tantalum or tungsten powder is added in order to develop more clearly in the imaging equipment; the polymerization of PMMA can be divided into: thin stage, viscous stage, hardening stage and heat generation stage. Injections are generally chosen to be rapidly injected into the vertebral body during the viscous phase, and it is difficult to inject too late, especially for PVP, which can be injected slightly later because of the lower resistance of PKP to injection.
The former mainly includes “C” arm X-ray machine or “C” arm X-ray machine + CT, while the latter includes puncture guide needle, cannula, manual drill, balloon expansion tube, pressure gauge, etc.
V. Operation technique
1, preoperative preparation: In addition to the general routine of interventional surgery, detailed X-ray, CT and MRI should be performed before surgery in order to clarify the diagnosis of VCF, and CT can understand the degree of vertebral body collapse and vertebral body edge, while MRI can estimate the fracture time by showing the edema in the lesion area in order to grasp the strict indications for surgery, improve the efficacy and reduce complications.
2.Puncture site: Routinely, the lumbar spine is punctured in the prone position via the root or paravertebral arch, the thoracic spine via the intervertebral arch of the head of the rib, the second cervical vertebra below the anterior vertebral body, and the cervical 1-2 via the mouth.
3.Surgical procedure: In the lumbar spine, for example, after local infiltration anesthesia, PVP is guided by imaging surveillance equipment, and a 10-14G puncture needle is used to perform a unilateral arch root puncture to the vertebral cortex, and the vertebral body is penetrated with the aid of a surgical hammer, and the puncture needle is confirmed to be located in the vertebral body by fluoroscopy or fluoroscopy + CT scan, and then a contrast agent is injected to understand the venous return, and then the prepared bone cement is rapidly injected into the vertebral body under close surveillance The bone cement is then injected rapidly into the vertebral body under close supervision, within 2-3 minutes, and the needle is removed before the cement hardens. Accurate positioning-the puncture needle is best located in the anterior 1/3 of the vertebral body and cannot break through the inner edge of the pedicle and the posterior edge of the vertebral body-is the key to improving outcomes and reducing complications. In contrast, after a successful puncture, PKP uses a manual drill to create a channel to place a dilating balloon tube, which expands the balloon under the monitoring of imaging equipment, and injects bone cement into the space created by the removal of the balloon as the collapsed vertebral body is close to returning to normal height. It is proposed that intraoperative monitoring of blood pressure and other vital indicators should also be performed.
4. Postoperative management: CT scan should be performed to assess cement filling and leakage, in addition to routine anti-infection treatment, wound protection, and observation for more than 2 hours, and for more than 24 hours if leakage is suspected.
VI. Clinical efficacy
The efficacy of PVP and PKP is mainly reflected in the following aspects.
1.Relieve or alleviate pain and improve patients’ quality of life.
2.Restoration of vertebral body height to different degrees.
3.Correcting the posterior convexity deformity.
4.Relieve or alleviate the compression.
5.Cure most of the hemangiomas.
VII. Complications
The complication rate of PVP and PKP is 0-10% and varies with different etiologies, among which osteoporosis is the least common, about 1.3%. It is mainly seen in the following areas.
1. Leakage of bone cement, which occurs most frequently. Strict operating procedures, proper injection dosage and timely detection by high definition surveillance equipment or CT scan at the time of injection are the keys to avoid bone cement leakage.
2.Nerve root thermal injury, mostly caused by bone cement leakage, occurs less frequently and mainly causes short-term pain aggravation, which can generally be relieved by appropriate drug treatment.
3.Pulmonary embolism is rare, one case is reported in the literature, mostly caused by leakage of bone cement vein, therefore, before injection, we should take an image to understand whether the vein is pierced and grasp the appropriate timing of injection, avoid excessive pressure, etc.
4.Rib fracture, rare, 2 cases reported in the literature, mostly caused by improper operation or serious osteoporosis.
5.Infection is rare.
VIII. Outlook
Since the clinical efficacy of PVP and PKP are obtained through medium and short-term follow-up analysis of cases in actual work, without strict scientific design and long-term systematic follow-up, thus their clinical efficacy is still unreliable. The therapeutic mechanism of scleroplasty bone cement is still not fully understood, and the biological response of bone cement to the bony junction and whether PVP and PKP increase the incidence of potential fractures in the adjacent vertebral body have not been systematically studied. Current interventional equipment such as imaging surveillance and puncture and balloon dilatation tubes do not yet fully meet the needs of PVP versus PKP development. Thus, the future of PVP and PKP depends to some extent on the progress of research in each of these areas, especially the development of new biocompatible bone cements, the progress of related basic research, and the availability of advanced equipment such as fluoroscopic CT.