Evolution of the Complications of Pedicular Arthrodesis over the Last Two Decades: A Meta-Analysis

Currently, the most widely used screw insertion techniques are: freehand, fluoroscopic guides, CT based navigation. The free hand technique refers to the technique that uses bone markers for screw insertion without the assistance of any intraoperative image [3]. The most used currently is the one that is performed with intraoperative radiological aid. Computed tomography navigation refers to optoelectronic browsers with the use of computerized tomography to create a three-dimensional image of the spine [4].


Introduction
Pedicle screw instrumentation allows better correction of spinal deformities in the thoracic and lumbar regions, such as idiopathic scoliosis, congenital kyphoscoliosis, kyphosis since its introduction by Roy-Camille in the 1980s [1]. The literature mentions the possibilities of better anchoring force compared to other available fastening techniques [2].
Currently, the most widely used screw insertion techniques are: freehand, fluoroscopic guides, CT based navigation. The free hand technique refers to the technique that uses bone markers for screw insertion without the assistance of any intraoperative image [3]. The most used currently is the one that is performed with intraoperative radiological aid. Computed tomography navigation refers to optoelectronic browsers with the use of computerized tomography to create a three-dimensional image of the spine [4].

Objective
The objective of the present review is to explain the main causes of complications in an attempt to avoid such situations as much as possible, as well as to evaluate the possibilities of a decrease in the prevalence of complications secondary to pedicle screws over the last 20 years.

Methods
We considered mainly the meta-analyzes in the English literature, and some prospective clinical studies with a number no inferior Pedicular Arthrodesis over the Last

Literature Review
Chronologically, an analysis was made on the percentages of complications related to poor positioning.
In a study carried out in South Korea with 432 patients submitted to fixation of 4604 thoracic pedicle screws followed prospectively for more than 2 years, poor screw positioning was detected in 67 screws of 48 patients (10.4%), referring to the main complication of the procedure. The neurological complications were related to the screws in 4 patients (0.8%), specified in a transient paraparesis and 3 dural injuries. It was also reported, in mechanical complications, 11 intraoperative fractures of the pedicle, 35 loosening of screws and framed in vascular complications, 9 postoperative infections [5].

Spine Research ISSN 2471-8173
An extensive review analyzed the position of 37,337 total pedicular screws implanted evaluating the presence or not of the positioning violation, concluding that the placement precision was higher in patients with assisted navigation in vivo, with 95.5% accuracy compared when navigation was not used. However, they also reported that in thoracic surgeries, both in vivo and cadaveric populations, there was no advantage with the use of navigation [6]. In the segment, the main complication was loss of correction of deformity, 1.6% of the total complications in the follow-up [7].
A bibliographic review of 23 studies compared the effectiveness of instrumentation guided by navigation techniques (719 patients with 3555 screws) with the ones that were not assisted (569 patients and 2437 screws). There were no neurological complications related to instrumentation in the navigation group, but in the non-guided group there were 13 cases of neurological complications [8,9]. The authors concluded that the complications are rare but severe when happening. They can be avoided by careful planning of the surgery as well using of guided imaging navigation techniques which can assist the surgeon in preventing complication by providing accurate anatomical guidance for the procedure [10].
In a study in USA with a homogeneous population of 208 adolescents with idiopathic scoliosis and a mean age of 14.9 years, a total of 1.123 thoracic pedicular screws were inserted (5,4 thoracic screws/patient). In the defined complications as directly related to the screws, the poor positioning of the screws was mentioned, since the postoperative CT was performed in only 19 of the 208 patients (9.1%). The radiographic evaluation showed possibility of aberrant trajectory in 23 screws, of 219 bolts evaluated. The dural tear was observed in 3 patients (1.4%) evidenced by leakage of cerebrospinal fluid when the screw holes were prepared. Intraoperative pedicular fractures were reported in 2 patients (0.9%) being attributed to attempts to the screw introduction. Three cases demonstrated radiographic evidence of the loosening of the screws due to poor positioning, with no clinical signs presented by the patient. One factor that should be mentioned is that in this study the studied population was of Chinese nationality, since the literature mentions some evidence that the pedicle morphology is unique in Chinese patients.
A meta-analysis that evaluated 21 studies with a total population of 1666 patients and 4570 pedicular screws by adolescent scoliosis (mean of 17.

Results
With regard to 20 articles, only 9 could be selected for analysis. Comparatively In both decades, the most mentioned complication refers to poor positioning of the screws. Considering the period evaluated, a 10.3% decrease in complications secondary to spinal instrumentation could be observed (Table 1).

Discussion
Besides considering the publications that were analyzed and compared, we obtained two articles that concluded that the intraoperative navigation significantly reduced the poor screw positioning, so it is important to point out that the techniques of navigation by CT and other orientation technologies are important factors for better operations.
With the reduction of 10.3% of the complications in the period evaluated, it is clear that as time went on and with the technological advances, complications decreased. However, efforts to improve neurological, vascular and mechanical complications and especially poor positioning, should not be abandoned.
These results should be carefully evaluated, since there are several potential sources of heterogeneity, besides the different population that has been considered in the studies. Pedicular screw insertions are complex interventions and it is difficult to avoid trends in comparison groups, since there are multiple diseases that affect different ages, ethnicities and genres [11].

Conclusion
The different ways of screw positioning may also be related to the surgeon's skills as well as the length and diameter of the pedicle screw that was introduced. We should try to deviate from this line of thought, including only meta-analyzes, prospective in vivo studies, and randomized studies, as they provide stronger evidence for meta-analysis.
Certainly, the complications caused by poor positioning of the pedicle screws are the most common. It is concluded that there is a growing need for a true improvement of methods that allow a safer intraoperative positioning of the screws.