1. King Edward Medical University, Lahore, Pakistan: digvdty-207nida@gmail.com
2. King Edward Medical University, Lahore, Pakistan: irshadhussain@gmail.com

*             Correspondence: digvdty-207nida@gmail.com

Keywords: vertebral metastasis, surgery, embolization, surgery

1. INTRODUCTION

The quality of life of patients affected by secondary lesions involving the spine is significantly affected by refractory pain, neurological disorders resulting from compression of the spinal cord, and instability of the spine. When conservative treatment is no longer an option for a patient, surgery should be used to improve the patient’s quality of life. Surgery can be performed in many different ways, but the most common method involves a broad laminectomy, minimally invasive percutaneous transpedicular instrumentation, and tumour removal. Annual advancements in orthopaedic methods are evident in the increased life expectancy of these patients and, ultimately, in the rise in the incidence of spinal metastases. Primitive tumours that most frequently and usually spread to vertebrae include cancers of the breast, lung, kidney, and prostate; these metastases mostly affect the arterial vessels; the posterior wall of the vertebral body is affected initially, followed by the anterior section, lamina, and pedicles. Intraoperative blood loss significantly complicates surgical methods, mostly due to the increased vascularization of vertebral metastases compared to normal vertebrae [1]. Transcatheter artery embolisation (TAE) has been utilised in both preoperative and palliative settings for bone tumours, both primitive and secondary, in recent years [2]. The introduction of a material into a blood vessel to block or lessen blood flow to an area or organ—in this case, the spinal metastases—is the general definition of embolisation therapy. Recent research has shown that the TAE technique, when used in conjunction with surgery, can effectively treat primary hypervascular bone tumours as well as secondary bone metastases [3, 4]. Technique-wise, there are no restrictions on where in the vertebral column preoperative embolisation of vertebral metastases can be carried out. According to statistics, the lumbar and thoracic spines include the majority of metastases. When embolising metastases, the goal is to obstruct the feeding artery as close to its proximal end as possible, preventing blood flow into the tumour vessel bed and ultimately leading to cellular death [5]. The less harm we can do to the nearby structures, the more focused the lesion is. It is crucial to use vascular catheterization with extreme selectivity in order to do this. Gelfoam, coils or microcoils, N-butyl-cyanoacrylate, ethylene–vinyl alcohol (Onyx), and polyvinyl alcohol (PVA) are the most commonly employed particles in TAE. The tumour vasculature experiences temporal blockage due to gelatin sponges, or gelfoam; the vessel recanalizes 24 hours following the embolisation. Non-reabsorbable PVA particles come in sizes ranging from 50 to 1200 mm; the most widely utilised size is between 100 and 300 mm. Surgery must be performed within 7 days following PVA embolisation to prevent recanalization. Tumour cell apoptosis is unquestionably caused by intra-arterial ethanol injection, which is linked to a variety of symptoms such as fibrinoid necrosis, intimal sclerosis, angionecrosis, and harm to normal tissue. For spinal metastases, using Onyx by a transarterial route or a direct tumour puncture is a safe and successful treatment. The most popular varieties are Onyx 18 and34, which are made up of 94% and 92% dimethylsulfoxide and 6% and 8% ethylene vinyl alcohol copolymer, respectively. Tumour recanalization is not a significant concern with Onyx because it is linked to permanent occlusion, in contrast to temporal vascular occlusion that occurs with gelatin sponge and PVA. Tumour softening was noticed eight days following embolisation following the surgery. PVA is the most often utilised embolic substance out of all of them, mostly because to its biocompatibility; nevertheless, because of its irregular particle size, PVA tends to agglomerate and might cause catheter obstruction, reducing the amount of penetration into a vascular lesion [6]. Particle embolisation is the recommended method, and during surgery, small-to medium-sized particles should be employed to minimise the blood supply. 150–250 mm diameter polyvinyl alcohol particles would be a common choice. Until complete stasis is achieved, embolism is continued [5]. Most often, the embolisation of vertebral body metastases results in spinal cord ischemia, which induces a cord infarction and neurologic abnormalities. The incidence rates of this condition are unknown due to its extreme rarity. The literature states that if the patient experiences neurologic symptoms during the intervention, if the spinal arterial supply is discovered to originate from the same level as the tumour enhancement, or if stable catheter positioning is not achievable, embolisation should be delayed [7]. The vertebral arteries supply blood to the cervical metastases; hence, vertebral embolisation is linked to a higher risk of ischemic stroke in the brain’s posterior circulation. Analyses, both prospective and retrospective, have been employed to investigate the optimal timing of embolisation before surgery. It has been demonstrated that embolisation works best to minimise intraoperative blood loss when carried out 24 hours after surgery, but not later than 48 hours. Since coils occlude pre-tumoral artery branches without completely filling in the tumour microvascular structures, their effectiveness in treating vertebral metastases is still debatable. Additionally, because some tumours, like renal cell carcinoma, have rich vascularity, using coils to treat them may not be beneficial [8]. Feldman et al. [1] performed two cases of peripheral bone lesions embolisation in 1975 before describing TAE as a helpful method in the management of bone tumours. Preoperative embolisation has demonstrated good outcomes and great efficacy in the years since this groundbreaking study. For hypervascular spinal tumours, particularly for renal cell spinal metastases, it currently serves as the standard of therapy. However, there are no established standards regarding the use of endovascular embolisation and preoperative spinal tumour angiography, and the indications for these procedures differ significantly amongst centres. This thorough analysis of the literature aims to clarify the pre-operative spinal embolisation techniques’ methodology, benefits, and effectiveness.

2. MATERIALS AND METHODS

The following keywords were used by two radiologists conducting independent research using MEDLINE databases, including PubMed and Web of Science: “spinal tumours,” “spinal hypervascular tumours,” “spinal metastases,” “preoperative endovascular embolisation,” “preoperative transarterial embolisation,” “preoperative embolisation,” “endovascular embolisation,” and “transarterial embolisation.” Furthermore, a manual screening of the qualified studies’ references was conducted to find further eligible studies. The following were the inclusion criteria: (1) Research in which preoperative TAE treatment of spinal metastases was conducted; (2) Research assessing intraoperative blood loss, transfusion need, and duration of surgery, overall survival, and rate of complications. English was the only language allowed for publication. The following were the exclusion criteria: (1) Studies with duplicate data were removed; (2) studies using TAE to treat non-primitive bone diseases; and (3) studies using TAE following surgical intervention.

3. RESULTS AND DISCUSSION

According to Barton et al. [5], surgery should ideally be carried out as soon as possible following embolisation to avoid revascularization, but if not, it should be done no later than three days later. According to Tan et al. [3], although the differences were not statistically significant, the patients who had surgery between 13 and 24 hours had the lowest median EBL (Estimated Blood Loss), at 1000 mL. It is in fact advised to do surgery as soon as possible after TAE in order to take advantage of the tumours’ blood supply devascularization impact. Even though there was no statistically significant difference between the groups that got “gelfoam only,” “gelfoam + PVA,” and “coil + particles,” Tan et al. [3] stated that the median EBL was 1000 mL in those groups and 1500 mL in the other. There was a trend towards a lower median blood loss in embolised patients with primary spine tumours, thyroid metastases, and spinal metastases from HCC, but the difference was not statistically significant. In univariate analysis, preoperative haemoglobin, kind of surgery, tumour type, and length of operation were all found to be significant predictors of blood loss or transfusion requirement. Multivariate linear regression, after accounting for pertinent variables, showed no statistically significant differences in blood loss or transfusion units between the embolised and non-embolized groups. According to Barton et al. [17], patients who underwent preoperative embolisation experienced an intraoperative EBL of 500–1500 mL, whereas those who did not have TAE experienced an intraoperative EBL of 2000–18,500 mL. Sun et al. [9] found an average intraoperative blood loss of 533 mL among 16 patients with renal cell carcinoma metastases (of whom only 2 were vertebral); a significant reduction in extravascular lung lysis (EBL) was noted when more than 70% of the tumour vascularity was embolised (460 vs. 750 mL). For 21 spinal lesions, Wirbel et al. [11] found an average postoperative post-TAE EBL of 1650 mL. The two groups’ combined survival times did not vary: 12.2 months for the embolisation group and 12.0 months for the non-embolization group (ranges: 4-34 months and 3-36 months, respectively). Following radical surgery for RCC spinal metastases, Rehak et al. [12] retrospectively examined 15 patients. EBL was greater in the eight embolised patients (4750 mL) than in the seven non-embolized participants (1786 mL). Notwithstanding these findings, a meaningful comparison could not be established due to the substantial variations in the tumor’s size and the complexity of the treatment between the embolised and non-embolized groups. They ultimately deduced that the amount of EBL is influenced by the size of the metastasis, the tumor’s extension, the technical difficulty of the surgery, and the effectiveness of preoperative embolisation. The effectiveness of transcatheter arterial embolisation (TAE) of hypervascular metastatic lesions of the bone before orthopaedic excision and stabilisation was to be assessed in relation to intraoperative estimated blood loss (EBL) in work by Kickuth et al. (2008) [10]. They divided the TAE devascularization of 22 vertebral lesions into three grades: grade 1 (tumour blush reduced by more than 75%), grade 2 (tumour blush reduced by 50–75%), and grade 3 (tumour blush reduced by less than 50%). The degree of devascularization was correlated with TAE efficacy: patients in grade 1 had a median EBL of 500 mL, those in grade 2 had a median EBL of 1475 mL, and those in grade 3 had a median EBL of 2500 mL. There was no association discovered between average maximal tumour size and EBL, nor between EBL and operating time. 4.5% and 9%, respectively, of patients experienced minor and serious problems during and after TAE. A statistically significant difference in EBL was observed in 2012 by Kato et al. [13] between the embolisation group (520 mL) and the non-embolization group (1128 mL). There was no discernible relationship between the EBL and the timing of surgery following embolisation, the extent of tumour vascularization, or the completeness of embolisation in the embolisation group. In a case-control research including 54 patients, Zaborovskii et al. [16] retrospectively assessed the effectiveness of various bleeding control techniques and their impact on surgical outcomes and survival rates following decompression of RCC spinal metastases. Additionally, the first group consisted of 32 patients who underwent preoperative tumour embolisation (EMB). Furthermore, 22 patients in the second group (HEM) underwent surgery while intraoperatively receiving local hemostatic agents. Without any discernible changes, the EMB group’s median EBL (1275 mL) was lower than the HEM group’s (1400 mL). Compared to the EMB group (500 mL), the postoperative drainage loss in the HEM group (250 mL) was significantly lower. All groups experienced almost identical rates of complications, including infections, hematomas, and neurological deficits. They concluded that while there are alternative methods of limiting bleeding, such as the use of modern hemostatic medicines, not all patients with MRCC need preoperative embolisation. 2015’s Clausen et al. [18] demonstrated that there were no discernible variations in EBL between the embolisation group (618 mL) and the control group (735 mL). In the subanalysis of hypervascular metastases, blood loss in the embolisation group was considerably reduced (p = 0.041) from 902 mL (SD, 416 mL) to 645 mL (SD, 289 mL). Furthermore, the operation for the embolisation group was completed significantly faster than for the control group. There was a 27% decrease from a median of 124 minutes (range: 80–183 minutes) to 90 minutes (range: 54–252 minutes). Following surgery, there were three mild problems noted, including pleural exudates and atrial fibrillation. One significant consequence was a right common femoral artery thrombosis that occurred during angiography. 52 patients with spinal metastases of renal carcinomas who underwent palliative decompression were examined by Hong et al. [15]. Twenty-three (44%) of the fifty-two patients had hypervascular tumours. There was greater intraoperative blood loss in the individuals with hypervascular tumours. In cases of hypervascular tumours, EBL was higher in the non-embolization group (1988 mL) than in the embolisation group (1095 mL). There were no statistically significant findings regarding the clinical outcomes based on the primitive tumour or the metastatic site. Pulmonary (7/52, 13.5%) and wound problems (6/52, 11.5%) were the most frequent. Wound dehiscence, recurrent debridement, and advancement flap procedures were performed on four patients (7.7%). A total of 221 patients were investigated by Tan et al. [3], 48 (22%) of whom had embolizations while 173 (78%) did not. Sixty-one percent of the embolised patients achieved entire embolisation, meaning that the tumour blush was reduced by more than eighty percent. The median embolisation volume (EBL) for patients was 900 mL, significantly (p = 0.05) less than the EBLs of patients with partial (50%) and subtotal (50–80%) embolisation (1600 mL and 1350 mL, respectively). Since the proximal embolisation may obstruct small calibre collateral arteries supplying the tumour, the median EBL was significantly lower in the proximally embolised group compared to the distally embolised group (800 vs. 1200 mL). They discovered that in embolised cases of breast metastases, there was a statistically significant rise in median EBL. The median EBL is unaffected by the type of operation. Interestingly, EBL rose statistically considerably in embolised patients of thoracolumbar posterior instrumentation and decompression. In two-thirds of their instances, their entire embolisation rate was achieved, and these patients have noticeably lower EBL. Consequently, they recommend that complete embolisation be the aim in every case involving pre-operative embolisation. The EBL of patients who were embolised against those who were not was studied by Robial et al. [14] based on the type of tumour and the degree of resection. The 28 breast cancers (30.1%), 19 lung tumours (20.4%), 16 renal cell carcinomas (17.2%), and 30 other cancers (32.3%) were the primitive malignancies. The following surgical operations were performed: 12 cervical corpectomies, 29 thoraco-lumbar corpectomies or vertebrectomies, and 52 thoraco-lumbar laminectomies with instrumentation. There was no discernible statistical difference between the several primitive cancers in EBL. Depending on the type of surgery (corpectomy/vertebrectomy versus thoracolumbar instrumentation and cervical corpectomy), all histology samples demonstrated statistically significant increases in bleeding: breast (1775 mL vs. 778 mL), pulmonary (2500 mL vs. 430 mL), renal (3346 mL vs. 1175 mL), and others (1550 mL versus 474 mL). The current standard of care for all patients with RCC spine metastases when surgical resection is planned is to do a diagnostic spinal angiography and, if feasible, embolisation. Even partial embolisation of RCC metastatic lesions seems to reduce blood loss when compared to non-embolized tumours. Our review methodically examines the literature on preoperative vertebral embolisation, delving deeply into the details of postoperative blood loss, complication rates, and their relationship to the primary technical features of the procedure. This review contains a few significant flaws. Firstly, the majority of the included studies were retrospective case-control studies, which raises the possibility of bias in the original data. Secondly, research not available and research produced in languages other than English were removed. Third, there could be a bias risk in the aggregated results due to the different surgical and embolisation techniques used in the trials. Fourth, there was a chance that the studies’ inclusion of various types of metastasis would skew the findings.

4. CONCLUSION

Let us sum up by saying that preoperative arterial embolisation of vertebral lesions is a safe, well-tolerated procedure that makes surgical tumour excision easier and minimises surgical blood loss. To assess whether of the several embolising agents is the suitable indication, more research on bigger samples is required. To ascertain standardised indications and assess the efficacy of these treatments on various pathologies, longitudinal studies involving particular populations are necessary.

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