Study Design: This was a prospective case analysis.
Study Time and Institution:A total of 70 cases of thoracolumbar vertebral compression fractures with a symptom of low back pain, who underwent treatment between August 2014 and April 2016 at a hospital， were enrolled in this study(Table 1). These patients underwent PVP, and the bone mineral density (BMD) was measured routinely before operation, in addition to x-ray imaging of the anteroposterior and lateral positions of the thoracolumbar spine and magnetic resonance imaging (MRI). The inclusion criteria were as follows: (1) patients aged more than 60 years, with osteopenia displayed by BMD measurement; (2) patients with fresh fractures confirmed by MRI, which was shown by the x-ray examination as a single vertebral compression fracture, with the degree of vertebral compression no more than 75%; (3) patients whose fracture occurred spontaneously or was caused by minor trauma; (4) patients without any infection within the 15 cm range of the puncture position; (5) patients without cardiac pulmonary, hepatic, or renal failure; and (6) patients without coagulopathy or bleeding tendency. All patients were informed of the treatment modality after admission to hospital, and before surgery, they were informed that their follow-up information would be included in this study. Excluded cases comprised patients with concurrent spinal cord compression or nerve injury; or spinal stenosis exceeding 30%; or concomitant spinal tuberculosis, tumor, and rheumatoid arthritis.
Study Groups: The 70 eligible patients, with totally diseased vertebral bodies, visiting the hospital during this period were randomly allocated into three groups by the computer software based on their hospitalization numbers: group A (injection time duration < 180 s); group B (injection time duration at the range of 180–300 s); groups C (injection time duration > 300 s). The specific baseline information for each group was as follows: group A: 24 patients, 9 males (37.5%) and 15 females (62.5%), aged 62–88 years (mean age, 76.6 ± 7.9 years), with totally 24 diseased vertebral bodies, including T7 in 1 patient, T9 in 1 patient, T11 in 4 patients, T12 in 6 patients, L1 in 7 patients, L2 in 1 patient, L3 in 3 patients, and L4 in 1 patient, and with the time period between disease onset and operation to be 1–7 days (mean 4 days); group B: 23 cases, 7 males (30.4%) and 16 females (69.6%), aged 60–88 years (mean age, 74.7 ± 6.8 years), with totally 23 diseased vertebral bodies, including T9 in 1 patient, T11 in 2 patients, T12 in 7 patients, L1 in 9 patient, L2 in 2 patient, and L3 in 2 patients, and with the time period between disease onset and operation to be 1–6 days (mean 4 days); group C: 23 patients, 6 males (26.1%) and 17 females (73.9%), aged 61–87 years (mean age, 74.2 ± 8.1 years), with totally 24 diseased vertebral bodies, including T7 in 1 patient, T9 in 1 patient, T10 in 2 patients, T11 in 4 patients, T12 in 3 patients, L1 in 5 patients, L2 in 2 patients, L3 in 4 patients, and L4 in 1 patient, and with the time period between disease onset and operation to be 1–10 days (mean 5 days).
Materials:Acrylic resin bone cement was purchased from TEKNIMED S.A., France [specification and model: T040140; product standard number: import product registration standard YZB/FRA3620-2010; registration number: National Food and Drug Administration (enter) 2011 NO. 3650038]; bone cement mixer and vertebroplasty instrument (expansion type) were purchased from ZhongShan ShiYiTang Medical Equipment Co., Ltd. [Specification and model: 15 mL, PKP-I; product standard number: YZB/Guangdong 0574-2010; product registration certificate number: Guangdong Food and Drug Administration (quasi) 2011 NO. 2100306 (more)]; and computed tomography (CT) system was purchased from General Electric Company (Model: Lightspeed VCT).
Vertebroplasty: The diseased vertebral body was located using C arm fluoroscopy, and the point and angle of needle insertion were determined at the lateral position. The needle was inserted from the lateral superior direction to the vertebral pedicle (the left side was at 10 o’clock direction to the vertebral pedicle while the right side was at 2 o’clock direction). An incision was made through which the puncture needle was inserted, followed by the working cannula. High-viscosity bone cement was mixed and prepared by the surgical first assistant, whereas the second assistant started to count time and write records. After the cement was prepared, it was loaded into the rotary pressure pump, followed by slow injection into the vertebral body by the surgeon using C-arm fluoroscopy, a turn of the pump handle was applied appromimately 0.3cc. The injection was immediately stopped and the time was counted when bone cement reached the posterior wall of the vertebral body displayed under fluoroscopy. The injection volume of bone cement was visible via the scale on the filling machine and recorded. After the complete setting of cement, the working cannula was removed, and the wound was pressed for hemostasis and bound up.
Main Outcome Measures: The patients’ vital signs and complications of cement leakage were intensively monitored after surgery. CT inspection was performed for all patients 3 days after surgery. Three dimensional (3D) images of the vertebral body and bone cement were reconstructed on an image workstation by another group of medical staff via 3D imaging and volume rendering of CT data, and the measurement of bone cement and vertebral body was enabled via relevant functions of the workstation.
The diffusion capacity of bone cement injected into the vertebral body was reflected by diffusion coefficient: diffusion coefficient = diffusion volume/injection volume of cement. The postoperative image of the vertebral body was retrieved from the workstation. Subsequently, the boundary of cement diffusion was outlined and other tissues were deleted except for bone cement, prior to the acquisition of the diffusion volume of bone cement after several fractionations.
Analysis of bone cement leakage: Postoperative 3D images of the vertebral body and bone cement rendered on the image workstation were checked to record and analyze the leakage situation of bone cement, including paravertebral, intraspinal, and intervertebral space leakages. Subsequently, the leakage rate of bone cement was calculated for each group.
Statistical Analysis: The statistical analysis was conducted using statistical software SPSS16.0 (SPSS Inc., USA). Enumeration and measurement data were expressed, respectively, with frequency/percentage (n/%) and mean ± standard deviation (x ± s). Specific analysis included the following: (1) the mean and standard deviation of the injection and diffusion volumes were calculated for the three groups, followed by the normal distribution test; (2) the diffusion coefficient of bone cement among the three groups was compared by one-way analysis of variance; (3) the leakage rates among the three groups were compared using the chi-square test; (4) Pearson correlation analysis was used to measure the correlation of bone cement injection time with diffusion coefficient for the three individual groups; and (5) the analysis power was preset (α = 0.05), and a P value <0.05 was designated as statistically significant.