PERCUTANEOUS PEDICLE FIXATION OF THORACOLUMBAR VERTEBRAL FRACTURES WITHOUT NEUROLOGICAL DEFICITS

Objective: To evaluate the efficacy and safety of percutaneous pedicle fixation in thoracolumbar fractures without neurologic compromise. Methods: The study included patients aged between 18 and 70 with AO thoracolumbar fracture type (A.3) and kyphosis >30° or reduction of vertebral body height >50% or >50% of spinal canal compromise, who underwent surgery with percutaneous pedicle fixation in the first ten days after fracture. Radiological parameters were evaluated: Cobb angle, vertebral collapse, anterior wedging and spinal canal compromise preoperatively, postoperatively and at the end of follow-up. The clinical and functional outcome was assessed by the Oswestry Disability Index (ODI). Results: Mean operative time was 81 minutes (Min 69, Max 95 min). The mean volume of intraoperative blood loss was 85ml (75 Min and Max 155 ml). The mean follow-up was seven months (3 months Min, Max, 14 months) with an average ODI of 18% (excellent). Conclusions: The clinical results suggest that the pedicle fixation percutaneous technique may be an alternative to surgical treatment of thoracolumbar fractures type (A.3), without neurological deficits. This technique has proved to be safe and effective, with the advantages of a minimally invasive approach.


INTRODUCTION
Burst fractures are relatively common injuries in the thoracolumbar spine.
However, treatment of AO type (A3) unstable thoracolumbar fractures is still controversial, especially for patients with no neurological deficits. Although nonsurgical treatment has been described in several articles with good results, it is also well known that this type of treatment has several complications, including the worsening of kyphosis, consequences of prolonged bed rest, long period of recovery, and possible worsening/development of neurological deficits. 1,2 Surgical treatment has demonstrated better clinical and radiological results. It allows for immediate stabilization of the spine, restoration of sagittal alignment, and the possibility of spinal canal decompression. 3,4 However, the classical (open) surgical approach with pedicle fixation (short or long segment) involves extensive exposure and dissection, which is generally associated with a high rate of morbidity: high intraoperative blood loss, and significant infection and muscle injury rates. 5,6 Minimally invasive surgery, in particular percutaneous pedicle fixation, has become increasingly popular in spinal surgery.
The technique of placing pedicle screws percutaneously was initially introduced by Magerl in 1977. 7 Kim et al. 8 proved that percutaneous pedicle fixation causes less muscle damage than open pedicle fixation techniques.
The aim of this prospective study was to evaluate the efficacy and safety of percutaneous pedicle fixation using a minimally invasive technique for AO type (A.3) thoracolumbar fractures.

MATERIAL AND METHODS
Inclusion criteria were: AO type (A.3) thoracolumbar fracture; kyphosis > 30° and/or reduction of vertebral body height > 50% and/or compression of the spinal canal > 50%. 9 Exclusion criteria were: age less than 18 years or over 70 years, impossibility of surgical treatment in the first ten days after the injury, and the presence of neurological deficits. The study took place between December 2010 and December 2011. Twenty-three adult patients were included in this study, 12 were male and 11 female. The average age was 49.4 years (minimum of 24 and maximum of 68). As for the distribution of fractures by vertebral level, we obtained three cases affecting T8, one T9, one T11, four cases T12, ten L1, two L2, one L3, and one L4. The mechanism of injury included: 20 cases of falling from heights, two pedestrians being run over and one car crash. (Table 1) The pre-and postoperative evaluation during follow-up was performed using radiography ( Figure 1) and CAT of the thoracolumbar spine. (Figure 2) The radiological parameters evaluated were the Cobb angle, reduction of the height of the vertebral body, anterior wedging of the fractured vertebra, and compression of the spinal canal. The sagittal curvature was measured by the Cobb angle (defined as the angle between the upper surface of the vertebral body above the fracture and the bottom surface of the vertebral body at the level below the fracture). 10 Patients were evaluated at one, three, six, and 12 months postoperatively, clinically, the Oswestry Disability Index was collected, and radiographically and with CAT at three or six months.

Surgical technique
All patients were treated with the CD Horizon Longitude TM system (Medtronic -2600 Sofamor Danek Drive, Memphis, TN 38132).
The patient was under general anesthesia in the prone position with the abdomen uncovered. Identification of the entry point was made with fluoroscopic control. An incision of approximately 2 cm was made in the skin, slightly lateral to the pedicle entry point. We used a dilation tube (smaller diameter) to move soft tissues away from the entry point. The needle/punch, guide wire, and cannulated auger with the appropriate diameter and length (transpedicular) were successively placed under fluoroscopic control. Subsequently, the cannulated screw was placed through the dilator. This sequence of steps was repeated for each screw. Rods of suitable lengths were placed and shaped, as necessary, by a cranial incision, with the help of a guide. (Figure 3) Subsequent to the placement of the rods, we proceeded to distract and lock them. A control image was performed to check A B the positioning of screws, rods, and the restoration of the sagittal alignment. The dilators were removed, and the skin was closed. Postoperatively, the patients received antibiotic prophylaxis for 48 hours. The patient was allowed to stand after 24 hours and return to daily activities within two weeks.
The average clinical evaluation with the Oswestry disability index was 18% (excellent). Of the 23 patients treated, 19 showed no disabilities (0-20%), and four had moderate disability (21-40%). None showed a worsening of neurological status, infection, or fixation failure.    A B A C B D (Roland-Morris Disability Questionnaire): nine for conservative treatment, three for surgical treatment, by which they conclude that surgically treated patients also showed better clinical outcomes. At the end of the treatment, 85% of surgically treated patients returned to work, whereas only 38% of the conservatively treated patients returned to work. Percutaneous pedicle fixation has been widely used as a complementary technique for lumbar fusion in degenerative pathology. 11 In this study, the percutaneous pedicle fixation technique was used as a single fixation system of the AO type (A.3) thoracolumbar fracture.
In clinical evaluation, we used the Oswestry Disability Index and obtained a final average of 18% (minimal disability), better than the results published by Wei et al. 12 with a reported average of 34.1% (moderate disability).
The time of surgery (81 minutes) and blood loss (85 ml) were also lower than those reported in open pedicle fixation surgery, with a mean of 153 minutes and 828 ml, respectively, in the study by Verlaan et al. 13 The average correction of the Cobb angle was 8.2°, very similar to results published by Wen-Fei et al. 14 in a study of percutaneous pedicle fixation of thoracolumbar fractures without neurological deficits (with a mean Cobb angle correction of 8.9°) and the results published by Verlaan et al. 13 in a review of the surgical treatment of thoracolumbar fractures by classical transpedicular fixation (with a mean Cobb angle correction of 8.1°).
We can also see in our study that the results for the recovery of the vertebral body height (29.5%), recovery of the anterior wedging (17.1%), and of the spinal canal (14.6%) are identical to those published Wei et al. 12 in a study on thoracolumbar burst fractures with classical transpedicular fixation.
Regarding instrumentation without fusion, a prospective, randomized study compared pedicle instrumentation with and without fusion, 15,16 and demonstrated better results in the group without fusion.
However, some studies show that in AO type (A.3) fractures with a high degree of comminution of the vertebral body and high percentage of anterior vertebral wedging, pedicle fixation with fusion seems to have better results. Even in the absence of scientific evidence of the absolute necessity of fusion, specific instruments currently exist for percutaneous fixation that make fusion possible.

CONCLUSION
The percutaneous pedicle fixation technique presents radiological, clinical, and functional results that are significantly better than the published results with conservative treatment. This intervention, assisted by fluoroscopy, proved to be a technique with a high accuracy and reliability, with results similar to those reported in studies with the classical transpedicular fixation regarding the deformity correction, but superior with regard to blood loss, postoperative rehabilitation, and return to the activities of daily living.
The results of this study show that this is a valid, safe, and effective treatment for (A3) thoracolumbar burst fractures without neurological deficits.