Percutaneous technique of pedicle screw insertion was initially introduced by Magerl in 1977 as a temporary external fixation for the spinal fracture and spondylodiscitis. Different studies[6–8, 18] have shown that this technique improved the perioperative outcomes by reducing the blood loss and transfusion. Furthermore, it improved the postoperative outcomes by reducing the back pain and hospital stays, with similar surgical efficacy compared with the traditional open pedicle screw fixation. More importantly, the rate of the neurological injury risk had been shown to be as less as open techniques.
The percutaneous pedicle screw placement had significant potential limitations as well. These limitations included[1, 3, 10, 20]: longer operation time and greater fluoroscopy frequencies for both medical staffs and the patients. The traditional percutaneous methods showed a high incidence of erroneous placement of the pedicle screws and a steep learning curve. In the traditional method, the accurate percutaneous pedicle screw placement relies heavily on fluoroscopy in order to obtain a proper screw trajectory. The insertion of guide-wire into the vertebral pedicle required numerous radiographic images in a trial-and-error fashion. In recent years, a lot of systems or equipment[11, 24, 25] were introduced to facilitate the placement of percutaneous pedicle screw. These systems might improve the safely and decrease the radiation exposure, but added a significant amount of time to the operative procedure at the same time, what’s more, most hospitals cannot afford the purchase cost of these systems. Compared with these complicated systems, our novel retractor was relatively simple and practical, and affordable for every patient. The exposure of the entry point was facile with the help of our novel retractor. The feasibility and practicability of our novel retractor significantly reduce the operation time and radiation exposure in comparison with the traditional fluoroscopic method, in our study, the operation time in novel retractor group was 81.5% of that of traditional group, the fluoroscopic shot times was 43.8% less compared with traditional group.
VAS scores were significantly different between group A and B. The results showed that our novel retractor method was advantageous in this aspect over the traditional method. In our novel retractor method, we can set the percutaneous pedicle screw through the paraspinal sacrospinalis-splitting approach between the multifidus and the longissimus, from which the transverse process and facet joint could be easily exposed, making a good operative field and the pedicle screws could be inserted precisely. But in the traditional group, repeated punctures were always needed before the needle passing through the pedicle into the vertebral body in satisfactory position and direction, which was associated with facet joint capsule damage, it was a common cause of low back pain in adults and may lead to chronic pain and disability. In the traditional group, in the dilation tubes expanding and screw-in process of the percutaneous pedicle screw, it may not pass through the intermuscular space between the multifidus and the longissimus accurately, causing extensive stripping of paraspinal muscle, resulting in severe back pain and longer hospitalization time.
The novel percutaneous placement tool was particularly suitable for an accurate percutaneous pedicle screw placement in the obese patients. The intraoperative fluoroscopic or radiographic identification of the anatomical landmarks were frequently blurred in the obese patients and the quantity of the multifidus muscle was a significant risk factor for the pedicle screw misplacement[28, 29]. These results inferred that the fluoroscopic images were frequently blurred in bulky patients and the procedures were more difficult to be performed in a deeper space. In our novel retractor method, the longest head was 10 cm, it was long enough to reach the facet joint directly. The novel technique could be very demanding as it providing gross visualization and tactile feel, by using the novel retractor, we could expose the entry point effectively and thus the percutaneous pedicle screws could be accurately placed.
What’s more, no difference was found in correcting rate of Cobb’s angle and vertebral body height percentage between the two groups, suggesting that novel retractor method was similar to the traditional method in radiographic outcomes. Currently the major limitation of the novel retractor is that it is not suitable for posterior laminectomy and posterolateral fusion. Therefore, our inclusion criteria were strictly limited to cases of single segment thoracolumbar vertebral fractures.