Pulmonary cement embolism (PCE) is an underestimated but potentially fatal complication after cement augmentation. Although the treatment and follow-up of PCE have been reported in the literature, the risk factors for PCE are so far less investigated. This study aims to identify the preoperative and intraoperative risk factors for the development of PCE.
A total of 1,373 patients treated with the polymethylmethacrylate (PMMA) augmentation technique were retrospectively included. Patients with PCE were divided into vertebral augmentation group and screw augmentation group. Possible risk factors were collected as follows: age, sex, bone mineral density, body mass index, diagnosis, comorbidity, surgical procedure, type of screw, augmented level, number of augmented vertebrae, fracture severity, presence of intravertebral cleft, cement volume, marked leakage in the paravertebral venous plexus, and periods of surgery. Binary logistic regression analyses were used to analyze independent risk factors for PCE.
PCE was identified in 32 patients, with an incidence rate of 2.33% (32 of 1,373). For patients who had undergone vertebral augmentation, marked leakage in the paravertebral venous plexus (odds ratio [OR], 1.2; 95% confidence interval [CI], 0.1–10.3; p=0.000) and previous surgery (OR, 16.1; 95% CI, 4.2–61.0; p=0.007) were independent risk factors for PCE. Regarding patients who had undergone screw augmentation, the marked leakage in the paravertebral venous plexus (OR, 4.2; 95% CI, 0.5–37.3; p=0.004) was the main risk factor.
Marked leakage in the paravertebral venous plexus and previous surgery were significant risk factors related to PCE. Paravertebral leakage and operator experience should be concerned when performing PMMA augmentation.
Since Galibert and Deramond first described the use of percutaneous vertebroplasty (PVP) for the treatment of symptomatic vertebral hemangioma in 1984 [
PCE is caused by cement leakage into the vertebral venous plexus and reaches the pulmonary arteries through the azygous/hemiazygos system and cava vein. According to previous reports in the literature, PCE was detected in 1.0%–28.6% of patients by postoperative chest radiographs and/or computed tomography (CT) [
Whereas several case reports and case series have investigated the treatment and follow-up of PCE [
The study involving human participants were reviewed and approved by the Ethics Committee of The First Affiliated Hospital of Guangzhou University of Chinese Medicine (No. ZYYECK[2019]186). This study has been performed following the ethical standards in an appropriate version of the 1964 Declaration of Helsinki. Informed consent was waived by the Ethics Committee. Patients who underwent PVP, PKP, or CAPSI between January 2006 and December 2019 were reviewed. A total of 1,838 patients with osteoporotic vertebral fractures, spinal tumors, and degenerative spine diseases were initially retrieved from the hospital database. Patients without postoperative chest radiographs or chest CT were excluded. Finally, a total of 1,373 patients were included for further analyses.
The demographic and clinical information of patients was collected, including sex, age at operation, spinal bone mineral density (BMD), diagnosis, body mass index (BMI), comorbidities, date of surgery, surgical procedure, augmented level, type of screw, cement volume per level, and viscosity of bone cement. Patients with PCE were divided into vertebral augmentation group and screw augmentation group to conduct a subgroup analysis. For no obvious cement leakage occurred in vertebral augmentation level, patients who had undergone CAPSI+PVP were classified as screw augmentation group.
PMMA-based cement materials were used for all patients. Low-viscosity PMMA (Tecres S.P.A., Sommacampagna, Italy) was used in most patients. In contrast, part of patients who received vertebral augmentation was used high-viscosity PMMA (Confidence spinal cement system, Medtronic, Minneapolis, MN, USA) at the discretion of the attending surgery. In general, we injected PMMA with every 0.1-mL increment when it had a toothpaste-like viscosity (Mixing the low-viscosity bone cement for 30 seconds and waiting for 390 seconds, then the consistency of cement will change from liquid to toothpaste-like). The cement volume in the thoracic and lumbar vertebrae was about 2.5–6 mL and 3–8 mL. All vertebral augmentation procedures were performed bilaterally. According to different screw augmentation techniques, cement-augmented pedicle screws were divided into fenestrated and solid screws. The periods of surgery were classified equally into 2 periods. Because vertebral augmentation technique and screw augmentation technique were successively carried out in our department, time division of surgical periods between vertebral augmentation group (2006–2012 and 2013–2019) and screw augmentation group (2008–2013 and 2014–2019) was a little different.
Generally, the chest x-ray was reviewed routinely after the operation. If the patients complain of pulmonary problems, they will receive additional thoracic CT. To distinguish vascular calcification or calcified granuloma from PCE, a comparison between preoperative and postoperative chest radiographs (or chest CT scans, if possible) was performed. PCE was defined as postoperative emerging, solitary, or multiple branching linear density along the pulmonary vessel. If the distinction between vascular calcification and PCE was sometimes difficult in x-ray, a high-density branching with an attenuation greater than 500 HU in CT was judged as PCE [
In general, PCE and non-PCE cases were matched in a 1:4 ratio to provide sufficient statistical power [
Statistical analyses were performed using IBM SPSS Statistics ver. 19.0 (IBM Co., Armonk, NY, USA). Measurement data were compared by using independent-sample t-tests. For counting data, Fisher exact probability tests were used. Multivariate logistic regression analysis was further analyzed risk factors with a significant difference for multivariate analysis. A p<0.05 was regarded to be significantly different.
Thirty-two patients (3 males, 29 females) with PCE were identified. The overall incidence rate of PCE was 2.33% (32 of 1,373). The PCE sample had an average age of 71.52 years (range, 53–92) and an average T score of -3.75 SD (range, -6.6 to -1.3). The demographics of the PCE and non-PCE patients are shown in
All emboli were found in subsegment pulmonary arteries classified as peripheral PCE. There were no perioperative deaths due to PCE. Most embolisms appeared in the right lung (68.75%, n=22), with some appearing bilaterally in the lungs (31.25%, n=10). Of the 32 patients with PCE, 5 patients (15.63%) experienced transient symptoms or hemodynamic repercussions and received symptomatic or anticoagulation therapy, and the remaining 27 patients (84.38%) did not demonstrate clinical syndromes during the perioperative period. No patient required further surgery to remove the cement emboli. After discharge, 3 patients still took aspirin or warfarin due to cardiovascular disease, while the remaining patients did not receive long-term anticoagulation therapy. Demographic and clinical information of PCE patients is presented in
From non-PCE patients, 88 patients who had undergone vertebral augmentation (PVP or PKP) and 40 patients who had undergone screw augmentation were randomly selected as the control group 1 and 2. For patients who had undergone vertebral augmentation, the incidence of PCE was significantly more frequent in cases with a larger number of augmented vertebrae (p<0.05), marked leakage in the paravertebral venous plexus (p<0.001), and previous surgery (p<0.05) (
PCE after vertebral cement augmentation procedures was first reported in 1999 by Padovani et al. [
This study revealed that marked leakage in the paravertebral venous plexus and previous surgery had a statistically significant relationship with the development of PCE. Anatomically, the vertebral venous plexus consists of 3 interconnected veins: the internal vertebral venous plexuses, the external vertebral venous plexuses, and the basivertebral veins [
Factors related to paravertebral venous plexus leakage have been reported in the literature [
Although the period of surgery was not an independent risk factor in screw augmentation group (probably due to the small sample size), previous surgery bears a significantly higher risk of PCE than subsequent surgery. This result suggests that surgical experience and awareness about PCE have important implications for the occurrence of this complication. With the improvement of surgical techniques and the understanding of PCE, surgeons have been more careful in filling the vertebral body and have paid more attention to paravertebral cement leakage [
Additional risk factors for PCE have also been reported in the literature. Kim et al. [
The primary limitation is that some patients did not undergo postoperative chest radiography or chest CT, which may underestimate asymptomatic patients. A secondary limitation is that although operator variability and their manipulation may play a pivotal role in the development of PCE, we did not analyze the different operators or their operative habits. A final limitation is that some patients underwent PVP twice or more, so these patients were included multiple times.
PCE was not a very rare complication after PMMA augmentation. Significant leakage in paravertebral venous plexus and previous surgery were significant risk factors related to PCE. Paravertebral leakage and operator experience should be concerned when performing PMMA augmentation technique.
The authors have nothing to disclose.
This study was funded by the innovation and strength project of The First Affiliated Hospital of Guangzhou University of Chinese Medicine (2019IIT32).
A 56-year-old female developed postoperative pulmonary cement embolism after vertebroplasty at the T8, T11, and L1 levels (case No. 17). (A) Chest radiography findings were normal before surgery. (B) Postoperative x-ray showed significant leakage of the paravertebral venous plexus (black arrow) at the T8 level and a tubular-shaped, high-density embolism in the right lung (red box: zoomed region). (C) The 3-dimensional computed tomography reconstruction provided more accurate and clearer views of cement leaks.
A 73-year-old female developed postoperative pulmonary cement embolism after cement-augmented pedicle screw instrumentation at the L2–5 level (case No. 28). (A) Anteroposterior and lateral digital radiographs showed curvilinear cement in the paravertebral venous plexus (black arrow). (B) Postoperative chest x-rays showed a linear-like, hyperdense cement embolism in the right lung (red arrow). (C) The zoomed region of the red box shows cement leakage into the paravertebral venous plexus at the L5 level. In addition, a cement embolism was found in the right pulmonary vascular tree (red arrows).
Baseline characteristics of total sample and patients who developed pulmonary cement embolism
Characteristic | PCE | Non-PCE |
---|---|---|
No. of patients | 32 (2.33) | 1,341 (97.67) |
Age (yr) | 71.52 ± 11.22 (53–92) | 71.63 ± 10.17 (41–110) |
Sex | ||
Male | 3 (9.38) | 252 (18.79) |
Female | 29 (90.63) | 1,089 (81.21) |
Diagnosis | ||
OVCF | 25 (78.13) | 1,068 (79.64) |
ST | 0 (0) | 31 (2.31) |
LDD | 7 (21.88) | 242 (18.05) |
Surgical procedure | ||
PVP | 18 (56.25) | 851 (63.46) |
PKP | 4 (12.5) | 204 (15.21) |
CAPSI | 9 (28.13) | 269 (20.06) |
CAPSI+PVP | 1 (3.13) | 17 (1.27) |
Values are presented as number (%) or mean±standard deviation (range).
PCE, pulmonary cement embolism; OVCF, osteoporotic vertebral compression fractures; ST, spinal tumors; LDD, lumbar degenerative disease; PVP, percutaneous vertebroplasty; PKP, percutaneous kyphoplasty, CAPSI, cement‑augmented pedicle screw instrumentation.
Characteristics of patients who developed pulmonary cement embolisms
Case No. | Sex/age (yr) | BMD | Diagnosis | Surgical procedure | Type of screws | Augmented level | Location of PCE | Symptoms |
---|---|---|---|---|---|---|---|---|
1 | F/56 | -3.6 | OVCF | PVP | - | L1 | Bilateral lungs | None |
2 | F/60 | -3.0 | OVCF | PVP | - | T12, L3, L4 | Right lung | None |
3 | F/78 | -3.5 | OVCF | PKP | - | L3 | Bilateral lungs | None |
4 | F/71 | -3.1 | OVCF | PKP | - | T6, T8 | Right lung | None |
5 | F/80 | -4.9 | OVCF | PVP | - | T7, T10 | Bilateral lungs | None |
6 | F/85 | -4.1 | OVCF | PKP | - | L1 | Right lung | None |
7 | F/73 | -4.2 | OVCF | PKP | - | T12 | Bilateral lungs | None |
8 | F/58 | -2.8 | OVCF | PVP | - | L4 | Right lung | None |
9 | F/81 | -6.6 | OVCF | PVP | - | T11 | Right lung | None |
10 | F/77 | -3.7 | OVCF | PVP | - | T10, T11 | Right lung | None |
11 | F/76 | -2.2 | OVCF | PVP | - | L4 | Bilateral lungs | Chest tightness, chest pain |
12 | F/67 | -2.8 | OVCF | PVP | - | L4 | Bilateral lungs | None |
13 | F/72 | -3.3 | OVCF | PVP | - | T4, T5, T7 | Bilateral lungs | None |
14 | F/88 | -4.0 | OVCF | PVP | - | L2 | Right lung | None |
15 | F/78 | -4.7 | OVCF | PVP | - | T4 | Right lung | None |
16 | F/92 | -4.0 | OVCF | PVP | - | T12, L1, L5 | Right lung | None |
17 | F/56 | -5.3 | OVCF | PVP | - | T8, T11, L1 | Bilateral lungs | None |
18 | M/87 | -4.2 | OVCF | PVP | - | L2 | Right lung | None |
19 | F/62 | -4.9 | OVCF | PVP | - | T10, T11, L1 | Right lung | None |
20 | M/83 | -3.9 | OVCF | PVP | - | T10 | Right lung | None |
21 | F/83 | -4.7 | OVCF | PVP | - | T7 | Right lung | None |
22 | M/62 | -1.3 | OVCF | PVP | - | T12 | Bilateral lungs | Hypoxemia |
23 | F/84 | -2.6 | OVCF+KD | CAPSI+PVP | Solid | T11– L1 | Bilateral lungs | Blood pressure fluctuations |
24 | F/84 | -4.1 | LS+LSS | CAPSI | Solid | L4, L5 | Right lung | Fever, dyspnea, expectoration |
25 | F/67 | -4.1 | LSS | CAPSI | Fenestrated | L4–S1 | Right lung | None |
26 | F/62 | -4.0 | LS+LSS | CAPSI | Fenestrated | L4 | Right lung | None |
27 | F/78 | -3.5 | LSS | CAPSI | Fenestrated | L3–L5 | Right lung | Dyspnea, hypoxemia |
28 | F/73 | -4.3 | OVCF | CAPSI | Fenestrated | L2–L5 | Right lung | None |
29 | F/53 | -3.1 | OVCF+KD | CAPSI | Fenestrated | T10, T11, L1, L2 | Right lung | None |
30 | F/54 | -3.2 | LSS | CAPSI | Fenestrated | L4, L5 | Right lung | None |
31 | F/65 | -3.5 | LS+LSS | CAPSI | Solid | L4, L5 | Right lung | None |
32 | F/65 | -2.9 | DS+LSS | CAPSI | Solid | L1–5 | Right lung | None |
BMD, bone mineral density; PCE, pulmonary cement embolism; OVCF, osteoporotic vertebral compression fractures; PVP, percutaneous vertebroplasty; PKP, percutaneous kyphoplasty; KD, kyphotic deformity; CAPSI, cement-augmented pedicle screw instrumentation; LS, lumbar spondylolisthesis; LSS, lumbar spinal stenosis; DS, degenerative scoliosis.
Comparison of risk factors for the occurrence of PCE in vertebral augmentation group
Factor | Vertebral augmentation group (n = 22) | Control group 1 (n = 88) | p-value |
---|---|---|---|
Age (yr) | 73.86 ± 11.03 (56–92) | 73.39 ± 9.80 (53–90) | 0.846 |
Female sex | 19 (86.36) | 67 (76.14) | 0.394 |
BMI (kg/m2) | 21.43 ± 3.15 (14.95–27.27) | 21.78 ± 4.06 (14.69–37.11) | 0.641 |
BMD | -3.85 ± 1.13 (-6.6 to -1.3) | -3.71 ± 1.33 (-6.2 to -0.2) | 0.709 |
Diagnosis | > 0.99 | ||
OVCF | 22 (100) | 86 (97.27) | |
ST | 0 (0) | 2 (2.27) | |
Comorbidity | |||
Diabetes | 3 (13.64) | 10 (11.36) | 0.721 |
Hypertension | 9 (40.91) | 30 (34.09) | 0.621 |
Chronic pulmonary disease | 2 (9.09) | 3 (3.41) | 0.261 |
Coronary heart disease | 3 (13.64) | 8 (9.09) | 0.458 |
Surgical procedure | 0.755 | ||
PVP | 18 (81.82) | 74 (84.09) | |
PKP | 4 (18.18) | 14 (15.91) | |
No. of augmented vertebrae | 0.041 |
||
1 or 2 | 17 (77.27) | 82 (93.18) | |
3 | 5 (22.73) | 6 (6.82) | |
Augmented level | 0.256 | ||
Thoracic vertebra | 21 (60.00) | 58 (48.74) | |
Lumbar vertebra | 14 (40.00) | 61 (51.26) | |
Fracture severity | 0.327 | ||
Mild-moderate | 24 (65.79) | 69 (57.98) | |
Severe | 11 (34.21) | 50 (42.02) | |
Presence of intravertebral cleft | 0.068 | ||
Yes | 1 (4.55) | 20 (22.73) | |
No | 21 (95.45) | 68 (77.27) | |
Viscosity of bone cement | 0.261 | ||
Low | 20 (90.91) | 85 (96.59) | |
High | 2 (9.09) | 3 (3.41) | |
Cement volume per level (mL) | |||
PVP | 4.56 ± 1.81 | 5.04 ± 1.60 | 0.376 |
PKP | 4.10 ± 0.98 | 5.28 ± 1.69 | 0.199 |
Marked leakage in the paravertebral venous plexus | 0.000 |
||
Yes | 21 (95.45) | 19 (21.59) | |
No | 1 (4.55) | 69 (78.41) | |
Periods of surgery | 0.003 |
||
2006–2012 | 16 (72.73) | 32 (36.36) | |
2013–2019 | 6 (27.27) | 56 (63.64) |
Values are presented as number (%) or mean±standard deviation (range).
PCE, pulmonary cement embolism; BMI, body mass index; BMD, bone mineral density; OVCF, osteoporotic vertebral compression fractures; ST, spinal tumors; PVP, percutaneous vertebroplasty; PKP, percutaneous kyphoplasty.
p<0.05.
p<0.01.
Comparison of risk factors for the occurrence of PCE in screw augmentation group
Factor | Screw augmentation group (n = 10) | Control group 2 (n = 40) | p-value |
---|---|---|---|
Age (yr) | 68.50 ± 11.11 (53–84) | 68.10 ± 7.44 (53–90) | 0.892 |
Female | 10 (100) | 35 (80.00) | 0.569 |
BMI (kg/m2) | 22.20 ± 5.35 (14.67–30.70) | 23.11 ± 4.22 (15.94–33.05) | 0.531 |
BMD | -3.53 ± 0.58 (-4.3 to -2.6) | -3.30 ± 1.11 (-5.9 to 0) | 0.566 |
Diagnosis | |||
OVCF+KD | 3 (30.00) | 10 (25.00) | 0.707 |
LSS | 3 (30.00) | 18 (45.00) | 0.148 |
LS+LSS | 3 (30.00) | 7 (17.50) | 0.397 |
DS+LSS | 1 (10.00) | 5 (12.50) | > 0.99 |
Comorbidity | |||
Diabetes | 3 (30.00) | 8 (20.00) | 0.671 |
Hypertension | 3 (30.00) | 13 (32.50) | > 0.99 |
Chronic pulmonary disease | 0 (0.00) | 3 (7.50) | > 0.99 |
Coronary heart disease | 1 (10.00) | 1 (2.50) | 0.363 |
Number of augmented vertebrae | 0.474 | ||
<3 | 5 (50.00) | 26 (65.00) | |
≥3 | 5 (50.00) | 14 (35.00) | |
Augmented level | 0.174 | ||
Thoracolumbar spine | 2 (20.00) | 2 (5.00) | |
Lumbosacral spine | 8 (80.00) | 38 (95.00) | |
Type of screw | > 0.99 | ||
Fenestrated screws | 6 (60.00) | 23 (57.50) | |
Solid screws | 4 (40.00) | 17 (42.50) | |
Cement volume per level (mL) | 3.73 ± 1.68 (1–6.3) | 3.87 ± 1.36 (2–8) | 0.775 |
Marked leakage in the paravertebral venous plexus | 0.001 |
||
Yes | 9 (90.00) | 11 (27.50) | |
No | 1 (10.00) | 29 (72.50) | |
Periods of surgery | 0.150 | ||
2008–2013 | 6 (60.00) | 13 (17.50) | |
2014–2019 | 4 (40.00) | 27 (82.50) |
Values are presented as number (%) or mean±standard deviation (range).
PCE, pulmonary cement embolism; BMI, body mass index; BMD, bone mineral density; OVCF, osteoporotic vertebral compression fractures; KD, kyphotic deformity; LSS, Lumbar spinal stenosis; LS, lumbar spondylolisthesis; DS, degenerative scoliosis.
p<0.05.
p<0.01.
Multivariate logistic regression analysis of the risk factors for pulmonary cement embolism
Factor | OR | 95% CI | p-value |
---|---|---|---|
Vertebral augmentation group | |||
Number of augmented vertebrae | 68.7 | 13.4–351.4 | 0.652 |
Marked leakage in paravertebral venous plexus | 1.2 | 0.1–10.3 | 0.000 |
Periods of surgery | 16.1 | 4.2-61.0 | 0.007 |
Screw augmentation group | |||
Marked leakage in paravertebral venous plexus | 4.2 | 0.5–37.3 | 0.004 |
OR, odds ratio; CI, confidence interval.
p<0.01.