COMPLICATIONS OF THE ANTERIOR APPROACH TO THE CERVICAL SPINE

Objective: To evaluate the complications of anterior approach to the cervical spine in patients who underwent cervical arthrodesis with instrumentation. Methods: Prospective and descriptive study was conducted from January 2009 to April 2010. All patients who underwent arthrodesis of the cervical spine by anterior approach were included, regardless the diagnosis. Access was made by the anterior approach on the right side. We evaluated the number of operated levels (1, 2 or 3 levels) and, the type of procedure performed: discectomy and placement of cage and plate (D+C+P), discectomy with placement of a cage (D+C) or corpectomy with placement of cage and plate (C+C+P). All complications related to surgical approach were reported. Results: We studied 34 patients, 70% male. The average age was 50 years and mean follow-up was 8 months. Eighteen percent of patients had complications, distributed as follows: dysphasia (33%) and dysphonic (67%). Among patients who developed complications, most underwent to D+C+P (83%) and no complications were found in patients where no cervical plate was used. Regarding levels, both complications were identified in patients operated to one or two levels. However, in patients operated on three levels, only dysphonia was identified. Conclusion: The most frequent complication was dysphonia. Patients who presented more complications were those undergoing discectomy and fusion with cage and anterior cervical plate. All cases of dysphonia were in this group. The number of accessible levels does not seem to have affected the incidence of complications.


INTRoDuCTIoN
The anterior approach to the cervical spine can be used as surgical treatment for various diseases, including fractures, degenerative disease, neoplasia, and correction of kyphotic deformities, among others. 1uring the surgical procedure, several structures must be dissected and retracted in order to properly expose the cervical spine.These include the anterior neck muscles, the trachea, the esophagus, and the carotid triangle, among others. 1,2tudies have demonstrated the importance of knowledge of the recurrent laryngeal nerve (RLN) in the anterior approach to the cervical spine. 2,33][4][5] Some authors suggest that there is a greater risk of injury when the approach is performed from the right side, 2 but others have shown that the side of the approach is not correlated with the possibility of nerve injury. 3Retraction of the esophagus is associated with dysphagia, and there are also reports of esophageal perforation as a complication of this approach. 4,6,7he placement of an anterior cervical plate appears to increase surgical time, and can lead to greater damage to the tissue of the retracted structures.It is, therefore, a factor that can contribute to postoperative complications.However, it is used to promote faster arthrodesis and enable earlier recovery. 8hus, it is important to have data that can suggest factors that lead to these complications.The objective of this study was to evaluate the postoperative complications of the anterior approach to the cervical spine in patients who underwent arthrodesis with instrumentation.meTHoDS This is a prospective, cross-sectional study conducted by the Department of Neurosurgery of the Hospital Universitário Evangélico de Curitiba, Paraná, Brazil, during the period January 2009 to April 2010.
The patients included in the study were all those submitted to anterior approach cervical fusion, regardless of the diagnosis of the disease.Preoperative exams included imaging exams of the cervical spine (x-rays, computed tomography, and magnetic resonance imaging).
A prophylactic antibiotic was administered with the anesthesia.The patients were intubated in the conventional way, seeking to keep the neck immobile.
The skin incision was performed obliquely following the neck line when visible.The anatomical points of reference were used to identify the level to be operated, which was confirmed intraoperatively with a fluoroscope.All the procedures were performed from the left side, by teaching neurosurgeons or supervised senior residents.The procedures performed were: 1) discectomy plus placement of an intersomatic device plus anterior cervical plate (D+P+P); 2) discectomy plus placement of an intersomatic device (D+P); and 3) corpectomy plus placement of an intersomatic device plus anterior cervical plate (C+P+P).In all cases, the intersomatic device used was a titanium cage filled with autologous bone graft.A suction drain was left in all patients and removed after 24 hours.
In the immediate postoperative period, patients remained hospitalized for approximately 24 hours in the intensive care unit.Control X-rays of the cervical spine were taken prior to discharge.
The average follow-up period was eight months (1 month to 15 months).
All complications related to the procedure were observed and analyzed.
The data was organized in tables and analyzed descriptively.
Most of the patients (65%) underwent surgery at a single level.The most commonly performed procedure was the D+P+P (71%).D+P+P was performed in all the patients who underwent fusion of three levels.Three patients (37.5%) underwent corpectomies of a single level, which is considered to be fusion of two levels.
Six patients (18% of the cases) had complications related to the surgical approach.(Figure 1) The complications were dysphagia and dysphonia, the latter being more commonly encountered (67%).(Figure 2) The number of complications occurring by groups of patients with fusion of 1, 2, and 3 levels were similar.(Figure 3) Most of the patients who developed complications were those who underwent discectomy using a cage and cervical plate for fusion (D+P+P).In those in whom a cervical plate was not used (D+P), no complications were identified.(Figure 4) In relation to the number of fused levels, (Figure 5) dysphonia was the most common among patients who underwent fusion of three levels, and was also the only complication found in this group.The numbers of instances of dysphagia and dysphonia in the groups with fusion of either one or two levels were similar.
Taking the type of procedure performed into account, (Figure 6) the placement of the plate (D+P+P) presented both types of complications cited above.All the cases of dysphonia also occurred in this group.In the patients who underwent corpectomy, only one complication was reported; that of a patient who developed dysphagia.There were no complications related to the surgical approach in the group of patients where the cervical plate was not used (D+P).

DISCuSSIoN
Anterior approach cervical fusion is a widely used surgical technique for the treatment of various comorbidities that affect the cervical spine. 1 The different types of complications that can result from an anterior approach to the cervical spine include vascular, esophageal, and tracheal damage, infection, and injury to the recurrent laryngeal nerve. 3-5,9,10 Dysphonia is the result of damage to this nerve which can be caused not only by section of the nerve, but also by stretching during retraction of the muscle from the vertebra.Arantes et al 2 suggest that the RLN is more susceptible to injury when access is from the right side, because of the anatomy of the nerve.Kilburg et al 3 studied 418 patients who underwent anterior cervical fusion of one or two levels, and found RLN injuries in 1.9% of cases, with no statistically significant difference between the sides of approach.
In our study, only six patients had complications related to surgical access and these were only dysphonia and dysphagia.Dysphonia was the more common complication among these six cases (67%) and all of the patients underwent an approach from the right side.
Dysphagia can be caused by the excessive retraction of the esophagus and larynx resulting in swelling and, later, possibly presenting areas of fibrosis. 4,9Dysphagia can also be caused by the displacement of the fixation plate and the screws.
In our study, dysphagia was only found in patients with placement of a plate and screws, but displacement of this material was not observed in any of these patients, suggesting that the mere presence of the plate and screws can cause symptoms.Another important factor is that for placement of the plate and screw, the esophagus and the larynx remain moved to the side and/or retracted for a longer period of time, leaving the patient more susceptible to postoperative dysphagia.
However, when the number of levels operated is considered, dysphagia was not observed in patients with surgery to three levels.Bazaz et al 9 evaluated the incidence of dysphagia in patients who underwent anterior cervical fusion and showed that there was no relationship between the postoperative presence of dysphagia and the number of levels treated or the type of procedure performed.Jagannathan et al 10 observed dysphagia in 9% of their patients who underwent anterior cervical discectomy of only one level without the use of a plate.
Both complications were temporary and 14 days following the surgery, when the patients returned to the clinic for reevaluation, none of them reported any symptoms.
The complications encountered do not appear to be associated with the number of levels treated, but they do seem to be related to the use of anterior fixation material (plate and screw).Randomized studies with larger samples need to be conducted to evaluate the real impact of these variables in complications resulting from an anterior approach to the cervical spine.

CoNCLuSIoN
The most common complication was dysphonia.The patients who presented the most complications were those who underwent arthrodesis with discectomy using a cage and an anterior cervical plate.The number of levels does not seem to impact the incidence of complications, but in patients who underwent fusion of three levels, dysphonia was the only complication.

Figure 6 .
Figure 6.Percentage of complications by type of procedure performed.