Evaluation of the value of pedicle screws for cervicothoracic fracture‐dislocation

Abstract

Objective:  To explore the value of pedicle screw implantation for fracture‐dislocation injuries of the cervicothoracic junction (C₆–T₂).

Methods:  Pedicle screws were implanted into 26 patients (17 male and 9 female) with cervicothoracic fracture‐dislocations from May 2001 to January 2008. Computed tomography (CT) scan was used to evaluate the accuracy of placement of the pedicle screws three days after surgery. Complications and state of neurological recovery were also recorded after the procedures.

Results:  One hundred and four pedicle screws were implanted successfully in our group. Seventy‐four pedicle screws were inserted into cervical vertebrae, 16 at C₅, 16 at C₆, and 42 at C₇, while thirty were implanted in the upper thoracic vertebrae, 22 at T₁ and 8 at T₂. Injury to the spinal cord, nerve roots or vertebral artery did not occur during surgery. Eleven screws (14.9%) perforated pedicles in the cervical spine. Three screws (10%) perforated the pedicle wall in the upper thoracic spine. Fusion was achieved in all cases and no failure of internal fixation was found, except for one screw which broke at C₅. Neurological improvement was found in all patients according to the American Spinal Injury Association (ASIA) score except for eight who suffered from complete paralysis. The Japanese Orthopaedic Association (JOA) score increased from 7.5 ± 2.0 to 14.5 ± 2.3 (t= 6.34, P < 0.05).

Conclusion:  Implantation of pedicle screws is a safe and reliable method for treating fracture‐dislocation injuries at the cervicothoracic junction.

Introduction

Fracture‐dislocation of the cervicothoracic junction presents a serious clinical problem in regard to diagnosis and treatment, because of difficulties in anatomical access to this special region. Although there have been many reports on anterior open reduction and internal fixation (ORIF) procedures for fracture‐dislocations of the cervicothoracic junction, studies on specific pedicle screws in this region have been sparse in the literature. During the period from May 2001 to January 2008, 26 patients with fracture‐dislocation of the cervicothoracic region underwent reduction and fixation by pedicle screws in our department.

Materials and methods

Subjects

Twenty‐six patients with fracture‐dislocation of the cervicothoracic junction were enrolled in our group. There were 17 male and 9 female patients. The age range was 20 to 75 years (average, 48.5 years). Instability of the cervicothoracic junction was caused by traffic accidents in 15 cases, falls in 8, crashes in 2 and an explosion in 1. There were ten burst fractures at C₆, three at C₇ and two at T₁. Dislocation of C₆,₇ and C₇T₁ was found in five and six cases, respectively. According to the ASIA score, there were eight cases in category A, ten in B, five in C, two in D and only one in E (Table 1).

Table 1.

Recovery of neurological status according to ASIA score

Pre‐operation (ASIA)	Cases	Post‐operation (ASIA)
		A	B	C	D	E
A	8	8	0	0	0	0
B	10	0	0	3	4	3
C	5	0	0	0	2	3
D	2	0	0	0	0	2
E	1	0	0	0	0	1
Total	26	8	0	3	6	9

Managements

Pre‐operative evaluation

Computed tomography (CT) scan and 2‐dimensional (2D) reconstruction were used in all cases. The height and declination of the pedicles at the cervicothoracic junction were assessed on sagittal reconstruction views, while the width and introversion of pedicles were evaluated on transverse reconstruction views. Meanwhile, the anatomic relation between the pedicle and the arch of vertebrae at the cervicothoracic junction was studied on CT reconstruction images.

Surgical procedures

Nineteen patients were treated by posterior pedicle screw stabilization only. The other seven underwent pedicle screw fixation combined with anterior decompression and reconstruction. Patients were placed under general anesthesia and positioned prone on a turning frame with skeletal traction through tongs. A standard midline longitudinal exposure was made with dissection of the erector spinae muscles laterally to the lateral edge of the lateral mass and the tip of the transverse process at the cervicothoracic junction. After placement of pedicle screws in this region, reductions of dislocation and interlocked facets were achieved in order to reestablish the correct alignment. Lower anterior cervical approaches were used for those patients who required combined surgery after posterior fixation.

Placement of cervicothoracic pedicle screws

After exposure of the lateral mass at the cervicothoracic junction, the lateral part of the upper quadrant was selected as the entry point and the cortical bone there was removed with a high‐speed burr. Then a screw awl was applied to tap the vertebral bodies from the entry point. The trajectories in sagittal and transverse planes were based on pre‐operative radiographic evaluation. A probe was used to palpate the walls and bases of pedicles before pedicle screw insertion. In cases where there was difficulty in identifying anatomic landmarks, a keyhole foraminotomy was performed in the inter‐laminar space so that the superior and medial walls of the pedicle could be palpated by a nerve probe. Screw insertion was guided by the pedicle walls. Three screws were inserted in this manner. For thoracic vertebrae at the cervicothoracic junction, the entry point for pedicle screw placement was 1 mm inferior to the mid‐point of the inferior facet border, the trajectory being 20°–40° introversion and about 20° declination according to preoperative CT measurement.

A screw of appropriate axis was chosen and placed in the pedicle after appropriate bending and placing of the plate. The bone graft was completed before the internal fixation system was put in place. The diameter of the screws inserted was usually 3.5 mm or 4.0 mm.

Evaluation and statistical analysis

Evaluation of accuracy of placement of the pedicle screws was based on CT scan three days after surgery. The numbers and rates of screw perforation were counted. Complications of pedicle screw fixation and the fusion rate were recorded during follow‐up in the current study.

The ASIA classification and JOA scores were used to assess recovery of neurological status after the procedures. SPSS 11.5 software (SPSS, Chicago, IL, USA) was used for statistical analysis. Paired Student's t‐test was performed and statistical significance was defined and accepted as P < 0.05.

Results

All subjects were followed up for 3–74 months, (average, 36.5 months). Four cases died because of cardiopulmonary insufficiency within six months of surgery. One hundred and four pedicle screws were implanted successfully in this group (1, 2).

Figure 1.

A 47‐year‐old man had been subject to a fall injury. (a) CT coronal reconstructive view showing a burst fracture of the C₇ vertebral body. (b) Axial CT view indicating C₇ burst fracture. (c) Sagittal CT views indicating a displaced fracture of the C₇ facet. (d–g) Postoperative anteroposterior (AP), lateral and oblique X‐ray films. A posterior approach was used in this procedure. For reconstruction, pedicle screws were implanted. (h) Axial CT view. The screws are in the pedicle of C₆. No perforation of the medial or lateral walls of the pedicle is apparent. (i) Axial CT view. The screws are in the pedicle of T₁. No perforation of the medial or lateral walls of the pedicle is apparent.

Figure 2.

A 67‐year‐old man with ankylosing spondylitis who was subject to a fall injury. C_6,7 fracture‐dislocation accompanied by incomplete paraplegia was found. (a, b) AP and lateral X‐ray films before surgery. (c) Sagittal CT indicating C_6,7 fracture‐dislocation. (d, e) Postoperative AP and lateral X‐ray films. Combined posterior and anterior approaches were used in this procedure. For reconstruction, pedicle screws and an anterior plate were implanted. (f) Axial CT view. The screw is in the pedicle of C₆ on the right side. No perforation of the medial or lateral walls of the pedicle is apparent. (g) Axial CT view. The screw is in the pedicle of C₆ on the left side. No perforation of the medial or lateral wall of pedicle is apparent. (h) Axial CT view. The screws are in the pedicle of C₇. No perforation of the medial or lateral walls of the pedicle is apparent. (i) Sagittal CT view. The screw is in the pedicle of C₆. No perforation of the superior or inferior walls of the pedicle is apparent. (j) Sagittal CT view. The screw is in the pedicle of C₇. No perforation of the superior or inferior walls of the pedicle is apparent.

Seventy‐four pedicle screws were inserted in the cervical vertebrae. These included 16 at C₅, 16 at C₆, and 42 at C₇. Thirty pedicle screws were implanted in the upper thoracic vertebrae. These included twenty‐two at T₁ and eight at T₂. Injury to the spinal cord, nerve roots or vertebral artery did not occur during surgery. Eleven screws (14.9%) perforated pedicles in the cervical spine, these misplaced screws deviated laterally in 7 screws (9.5%), superiorly in 1 (1.4%) and inferiorly in 3 (4.1%). Three screws (10%) perforated the pedicle wall in the upper thoracic spine, the direction of deviation was lateral (2 screws, 6.7%) and medial (1, 3.3%, within 2 mm). Fusion was achieved in all cases and no failure of internal fixation was found, except for one screw which broke at C₅.

According to the ASIA classification, neurological improvement occurred in all patients except for eight who suffered from complete paralysis (Table 1). The JOA score increased from 7.5 ± 2.0 preoperatively to 14.5 ± 2.3 six months postoperatively (t= 6.34, P < 0.05).

Discussion

The complex anatomy of the cervicothoracic junction region makes a reliable assessment of plain radiographs in the lateral projection difficult or even impossible, which may result in failure to detect fracture or other diseases in this region ¹ . There are many reports of missed diagnoses in the cervicothoracic junction in the literature ² , ³ . To avoid misdiagnosis, the authors suggest that CT scan, including sagittal and transverse reconstruction, should be performed as a routine in addition to conventional X‐ray examination. With magnetic resonance imaging, soft tissue injuries in the cervicothoracic region can also be detected immediately.

The treatment of fracture‐dislocation in the cervicothoracic junction is also special. Although there have been many reports of anterior ORIF procedures for fracture‐dislocation in this region, studies on specific pedicle screws in this region are sparse. The cervicothoracic junction, being at the transition point from cervical lordosis to thoracic kyphosis, is subject to high shearing forces. Therefore rigid internal fixation should be performed for cervicothoracic fracture‐dislocations. Pedicle screws, which have been certified by biomechanical tests as the strongest internal fixation both for the cervical and thoracic spines, have obvious advantages compared to other types of internal fixation (for instance, lateral mass, transarticular and thoracic complex screw fixation) ⁴ , ⁵ , ⁶ . As for their clinical application, according to literature pedicle screws have also been confirmed to be satisfactory for management of injuries in the cervicothoracic junction ⁷ , ⁸ .

Fracture‐dislocations that occur in the cervicothoracic junction are usually accompanied by interlocking facets. A posterior approach is convenient for reducing fracture‐dislocations and achieving rigid internal fixation in one stage. Brute force should be avoided during reduction in order to prevent neurological deterioration. Partial facet resection can be performed if reduction is difficult or impossible. For patients in whom the spinal canal is occupied by retropulsed bony fragments, a lower cervical anterior approach ought to be performed for anterior decompression and reconstruction; seven cases underwent combined approaches in this study. Although the anterior approach to the cervicothoracic junction is generally considered to be difficult because the operative field is narrow and is limited by the sternum, clavicles, and vascular and neural structures of the superior mediastinum, no complications occurred in our group.

Pedicle screws are rarely used in the cervicothoracic junction as compared to the lumbar and thoracic spine. The main reason may be the potential high risk of iatrogenic damage to the spinal cord, nerve roots, or vertebral artery caused by screw misplacement in this region. Meanwhile, clear lateral views to monitor the trajectories of pedicle screws during surgery are not available by fluoroscopy due to interference by the shoulders. Thus, the technique of pedicle screw placement in the cervicothoracic junction seems to be more demanding than in other regions. Abumi et al. implanted 669 screws in the lower cervical spine ⁹ . Forty‐five screws (6.7%) breached the pedicles, two of them causing neurological injuries. There was no difference between pedicle and lateral mass screws in respect of neurovascular injuries. However, failure of the hardware was significantly less with pedicle screws. Lee et al. found that, although pedicle screw accuracy was significantly improved with computer‐assisted techniques, 17 of 108 screws breached the pedicle by a margin of less than 2 mm and 1 screw by 2–4 mm ¹⁰ . All breaches were in a lateral direction and none of the perforations by the screws required revision. In the current study, 14.9% of screws perforated the pedicles in the cervical spine at the cervicothoracic junction, most of them breaching the lateral wall of the pedicles and entering the transverse foramen, while no vertebral artery injury occurred. The reason may lie in the relative ‘abundance space’ for the vertebral artery in the transverse foramen according to Zhao et al.'s study ¹¹ .

The complex anatomy of the cervicothoracic junction requires perfect surgical procedures, which should be performed only by a highly qualified and specialized team with appropriate facilities. In order to individualize the procedure and thus avoid serious problems during implantation of pedicle screws, it is necessary in all cases to get preoperative detailed radiographic data, especially CT sagittal and transverse reconstructions. In Lenoir et al.'s study, thirty patients underwent surgeries for unstable fractures at the cervicothoracic junction ¹² . Seven of them died of cardiopulmonary insufficiency within the first four postoperative months. In our group, four cases with total paralysis died within six months for the same reason as in Lenoir et al.'s report. Despite early diagnosis and surgical treatment, the presence of neurological or pulmonary lesions resulted in increased mortality for our operated patients. Thus, we believe that the limited surgery of posterior decompression and fixation is appropriate for cases with complete paralysis, in order to avoid a high death rate coupled with a low incidence of neurological recovery.