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Percutaneous vertebroplasty (PVP) is an effective treatment for lesions of the vertebral body that involves a percutaneous injection of polymethylmethacrylate (PMMA). Although PVP is considered to be minimally invasive, complications can occur during the procedure. We encountered a renal embolism of PMMA in a 57-year-old man that occurred during PVP. This rare case of PMMA leakage occurred outside of the anterior cortical fracture site of the L1 vertebral body, and multiple tubular bone cements migrated to the course of the renal vessels via the valveless collateral venous network surrounding the L1 body. Although the authors could not explain the exact cause of the renal cement embolism, we believe that physicians should be aware of the fracture pattern, anatomy of the vertebral venous system, and careful fluoroscopic monitoring to minimize the risks during the PVP.
Percutaneous vertebroplasty (PVP) is an effective, minimally invasive procedure in which polymethylmethacrylate (PMMA) cement is injected into a diseased vertebral body. This technique provides pain relief and strengthens weakened vertebral bodies. Vertebroplasty has gained widespread popularity for the treatment of benign or malignant compression fractures since its initial description 21 years ago . However, complications can still occur during the procedure even though PVP is considered to be minimally invasive. The reported complication rates range from 1 to 10%, but are generally minor . This paper reports our experience of a renal cement embolism during PVP, with a review of the literature.
A 57-year-old man, who had fallen from a 2.4 m ladder 4 months earlier, complained of severe back pain. He had been a healthy farmer prior to the accident. However, since his fall, he had suffered from debilitating back pain refractory to conservative treatment for 2 months. In particular, he complained of activity-related pain corresponding to the level of a compression fracture. The outside computed tomography (CT) scans demonstrated a compression fracture of the L1 body without destruction of the posterior wall and significant vertebral collapse. The magnetic resonance imaging (MRI) showed a slight step-off of the anterior cortical margin of the compressed L1 vertebral body, with lower marrow signal intensity on T1-weighted image (Fig. 1).
It was decided to proceed with PVP of the L1. The patient was placed in the prone position. An 11-gauge needle was advanced into the vertebral body via the left unilateral transpedicular approach using sterile technique and fluoroscopic guidance under local anesthesia. The PMMA (Zimmer Inc., IN, USA) cement has two components: an ampule of liquid and a fine powder of PMMA containing barium sulfate, e.g., 10 ml ampoule of liquid to 20 g of powder. Under careful fluoroscopic visualization, the mixture of PMMA cement and barium sulfate powder having a consistency similar to that of toothpaste was slowly injected into the vertebral body, diffusing throughout the intertrabecular marrow space. Before its injection, the mixture was loaded into several 1 ml syringes. However, when approximately 8 cc of PMMA had been injected unilaterally, multiple bone cement was detected at the bilateral renal fossae. The procedure was immediately stopped. After the procedure, the back pain had improved by more than 50%, but he still complained of severe right flank pain and fever. His renal function was impaired and the BUN to Cr ratio was high (27.2/1.3). On the same day, both kidneys were swollen (13 cm), and were found to contain a large amount of hyperechoic materials on the abdominal ultrasound (Fig. 2). The DMSA (99mTc dimercaptosuccinic acid) scan has been found to be quite useful for examining the bilateral kidney damage in detail, but the patient refused this. The CT scans showed the origin of the leak arising at the level of the vertebroplasty, and showed cement in the left anterior external venous plexus draining into both renal veins. Multiple tubular opacities, which corresponded to the course of the renal vessels, were detected, with some of the cement scattered through the left posterior external venous plexus on the CT scans (Fig. 3). The patient was diagnosed with a renal embolism and was treated conservatively. On the sixth day after the procedure, the BUN to Cr ratio had returned to normal, and the patient was released from hospital without pain. A follow-up ultrasound 8 months later revealed prominent atrophy of the right upper renal cortex with compensatory hypertrophy of the left kidney. However, the patient is currently doing well and has no subjective symptoms.
Image-guided percutaneous vertebral augmentation or PVP, was first performed in France in 1984, when Deramond and Galibert et al.  injected PMMA into the C2 vertebra, which had been partially destroyed by an aggressive hemangioma. Over the next 15 years, many groups advocated expanding the indications for PVP to include osteoporotic compression fractures, traumatic compression fractures, and painful vertebral metastasis [2, 6, 7, 11, 18, 19]. Our case had the anterosuperior fracture of the L1 body without destruction of the posterior wall and significant vertebral collapse so that it might not lead to a technically difficult vertebroplasty procedure; or might not constitute relative contraindications .
Even though PVP has many advantages including its simplicity, easy approach, and minimally invasiveness, many authors have reported several complications. The reported complication rates range from 1 to 10%, with a higher incidence of complications in cases with metastatic lesions . However, complications are rare (1~2%) with osteoporosis, and are generally asymptomatic and transient [2, 11, 19]. The reported complications associated with these procedures include hypotension, rib fractures , dural tear , pulmonary cement embolism [1, 4, 14], adult respiratory distress syndrome , cerebral cement embolism , root compression due to intraforaminal cement leakage , paraplegia due to spinal cord  and cauda equina compression , intravascular extension of cement , infection, and cement toxicity .
The vascular leakage of PMMA, although rare, might have disastrous consequences.
We could not determine the precise cause after a lengthy review of the whole procedure, but it is possible that there might have been some vascular anomaly, such as congenital communication, between the vertebral venous system and renal vessels.
The authors encountered an unexpected renal embolism during PVP. We could not explain the exact cause of the renal cement embolism, but we believe that physicians should be aware of the fracture pattern, anatomy of the vertebral venous system, and careful fluoroscopic monitoring to minimize the risk during the PVP.