Patient samples
We retrospectively reviewed 108 cases of single-segment, neurologically intact thoracolumbar (T11-L2) fractures from January 2012 to August 2016. All of the patients were treated in the Orthopaedics Department of our hospital. The fracture type was classified as type A according to the new AO thoracolumbar fracture classification system [18]. All of the patients received operations within two weeks following the injury. The indications for operation were as follows: (a) type A1 and CA>15°, (b) dynamic fracture, and (c) kyphotic deformity getting larger after admission. These patients were divided into 3 groups based on the surgical approach and method in this study: a COPSF group (36 patients who received conventional open approach pedicle screw fixation), a PPSF group (38 patients who underwent percutaneous pedicle screw fixation), and a POPSF group (34 patients who were treated with paraspinal posterior open approach pedicle screw fixation). Before the surgery, we introduced the characteristics of three surgical approaches and methods to the patients and their family. According to patients’ conditions and permissions, we performed operations by different surgical approaches and methods. All operations were performed by the same group of doctors, and the chief surgeon was the corresponding author. All of the patients received a 4-pedicle screw fixation. We did not analyze patients who received a pedicle screw in the fractured vertebra. Procedures were performed in accordance with the Declaration of Helsinki and were approved by the Ethics Committee of Human Experimentation of our hospital. The prove reg. number was 2011030. All of the patients signed corresponding informed consents before the study. The exclusion criteria were as follows: (1) pregnancy or pathologic and osteoporotic fractures, (2) younger than 18 years old or old than 60 years old, (3) an earlier surgery had been performed at the fracture site, (4) adjacent vertebral fracture, and (5) the initial fractures were combined with other diseases that could significantly influence daily life. For patients over 50 years old, we routinely measured bone mineral density to exclude osteoporosis.
Reduction system
In the COPSF group and POPSF group, the EXPEDIUM Spine System (DePuy Synthes, Raynham, MA, USA) was used; however, the VIPER MIS Spine System (DePuy Synthes, Raynham, MA, USA) was used in the PPSF group. All the pedicles in three groups were monoaxial. All the instrumentations in three groups were routinely removed 12 to 18 months after operation.
Surgical procedure
PPSF group
After the general anesthesia but before the operation, the patient was place in a prone position for several minutes and the kyphosis of the injured vertebral body was partly corrected by hyperextension. We used a preoperative locator to aid in locating the pedicle projection [19]. The preoperative locator was made of stainless steel. The locator consisted of several horizontal and longitudinal rods. Different marks were made on the rods, and there were 1-cm spaces between each horizontal rod. The patient was placed into a prone position after receiving general endotracheal anesthesia, and silicone pads were used to support the chest, abdomen, and pelvis. The preoperative locator was placed on the back of each of the patients, back with the central part (Fig. 1a). The correct pedicle projection and incision were obtained according to the different markers on the locator after observing the AP fluoroscopic image (Fig. 1b). An approximately 1.5-cm incision was performed, and the underlying fascia was bluntly dissected. A puncture catheter was positioned on the outer and lower edges of the pedicle and was slowly advanced into the pedicle and posterior half of the vertebral body. The guide wire was then inserted into the catheter, and the needle was carefully removed (Fig. 1c, d). The fascia and soft tissue were separated by using a series of sequential dilators. A self-tapping, cannulated pedicle screw with an appropriate length and diameter was inserted into the vertebra through the guide wire under the protection of the outside catheter (Fig. 1e), and then, the rod was installed (Fig. 1f). The rods were fixed using screws. At first, we only tightened the screws at one end, and then lever of the screw towers of the other end to generate additional lordosis to correct the kyphosis. After the reduction, all the screws were tightened. During tapping, wire tapping, and screw implantation, the wire tapping and other instruments should be coaxial to the guide wire; otherwise, the guide wire may break through the anterior vertebral wall or pull out as the instrument enters and leaves. All of the procedures were performed with the use of G-arm fluoroscopic image guidance.
COPSF group
The patients in the COPSF group were treated with conventional open pedicle screw fixation surgery according to the previous study [7]. The reduction technique was the same as PPSF group.
POPSF group
The positions of the fractured vertebrae were ascertained by using the G-arm. After routine sterilization and placement of the drapes, an approximate 8- to 10-cm midline incision was performed in the target segment. Subsequently, the thoracolumbar fascia, multifidus, and longissimus were separated in order to reach the pedicle entry point. The next procedure was the same as the traditional method (Fig. 2).
Observation index
Three groups were compared in terms of operating time, intraoperative blood loss, intraoperative fluoroscopy, hospital stay, hospitalization cost, and postoperative complications. The vertebral body angle (VBA) and Cobb’s angle (CA) were evaluated at pre-operation, the third day after surgery, and the final follow-up. The VBA and CA were measured by conventional radiograph (X-ray). The visual analog scores (VAS) was evaluated at pre-operation, the seventh day after surgery, and the final follow-up. Oswestry disability index (ODI) scores were evaluated at pre-operation and the final follow-up. Levels of serum creatine kinase (CK) were measured at pre-operation, 1 day, and 1 week after the operation.
Statistical analysis
All of the statistical analyses in this study were performed by using SPSS 17.0 statistical software (IL, USA). The variables with continuous data were reported as means and standard deviations. Statistical analyses were conducted by using one-way ANOVA to compare the means if they were accord with normal distribution. Where the normal distribution was not met, the Wilcoxon rank sum test was used. The categorical variables that were demonstrated as counted data were compared by using the χ2 test. P < 0.05 indicated statistical significance.