Retrospective interventional study.
To introduce a free-hand pedicle screw (PS) insertion technique without fluoroscopic guidance in the C7 vertebra and evaluate the procedure's feasibility and radiologic outcomes.
Although PS insertion at C7 has been recognized as a critical procedure in posterior cervical fusion surgery, conventional techniques for C7 PS have several limitations.
Thirty two patients (64 screws) who underwent PS insertion in C7 with the novel technique were included in this study. Postoperative clinical and radiological outcomes were evaluated. Special attention was paid to the presence of any problems in the screw position including cortical breaches of the PS and encroachment of the PS into the spinal canal or the vertebral foramen. This novel technique for PS insertion in C7 without fluoroscopy guidance had three key elements. First, the ideal PS entry point was chosen near the C6–7 facet joint using preoperative images. Second, the convergent angle distance was measured at axial computed tomography (CT) imaging, which defined the distance between the tip of C7 spinous process and the extended line passing through the pedicle axis from the ideal entry point. Third, the cranial-caudal angle distance was measured in sagittal CT images, which defined the distance between the tip of the C7 spinous process and the extended line passing through the pedicle axis.
Cortical breach on postoperative CT images was observed in three screws. All violated only the lateral wall of the affected pedicle. The breached screws occurred in the initial five cases. Postoperative neurologic deterioration was not observed in any patient, regardless of cortical breaching.
The novel technique successfully allows for C7 PS to be placed and is associated with a low rate of cortical breach.
Posterior stabilization procedures with screw-rod systems are frequently used to treat various cervical pathologies in the cervical spine including cervical stenosis, segmental instability, and fracture-dislocation [
Since careful positioning of the screw is paramount, almost every surgeon carries out PS placement under fluoroscopic guidance. Unfortunately, fluoroscopic guidance during PS placement in C7 has several drawbacks. The anatomic structures of C7, such as its pedicle and vertebral body, can be concealed by shadowing of the shoulder, which make the checked fluoroscopic image to be bootlessly (
To avoid these risks of fluoroscopy, it is important to develop new fluoroscopy-free methods for better positioning a PS in C7. In this study, we describe the safety and clinical and radiological outcomes of a novel technique in C7 with PS insertion that does not require fluoroscopic guidance.
This study was approved by the Institutional Review Board of corresponding Pohang Semyeng Christianty Hospital, and informed consent was obtained from all study participants. This study was a retrospective review of medical records and radiologic images. Between March 2013 and June 2014, 32 patients (64 screws) who underwent PS insertion in C7 using our technique were enrolled. All operations were performed under a surgical microscope by a single surgeon (the corresponding author), without the aid of fluoroscopy.
This study was conducted only on the patients who complied fully with the following inclusion and exclusion criteria. The inclusion criteria were: (1) patients with compression of cervical spinal cord due to multilevel cervical spondylotic myelopathy or ossification of posterior longitudinal ligament, which were diagnosed using cervical spine radiographs and magnetic resonance imaging (MRI) that corresponded to clinical manifestations and physical examinations; and (2) patients who underwent multilevel posterior cervical fusion with PS fixation at C7 by author's technique. Those who met any of the following criteria were excluded: (1) infection or tumors in the cervical spine; (2) patients with hemorrhagic disorders, such as hemophilia and thrombocytopenia; and (3) patients judged unsuitable by the corresponding author.
All operations were performed with Mayfield tongs, with the patient in the prone position. A typical midline skin incision was made over the affected level of the cervical spine. In general, screw insertion was carried out after the main procedure, which included posterior decompression, decortication, and bone grafting to the facet joint. Prior to preparation and insertion of the PS in C7, careful periosteal dissections were performed to better expose the cortical bone and C6–7 facet joint. To achieve optimal placement of the PS in C7 without fluoroscopy using our technique, three critical elements were determined preoperatively: (1) the determination of the ideal PS entry point; (2) the convergent angle distance (CVAD); and (3) the cranial-caudal angle distance (CCAD), which were preoperatively determined with an Infinitt picture archiving and communication system (Bracknell, Berkshire, UK) and V-works three-dimensional (3D) simulation software (Cybermed Inc., Reston, VA, USA) based on preoperative fine-cut CT images. First, to choose the ideal PS entry point, a bony mark near the C6–7 facet joint, such as a tiny groove or protruded osteophyte, was initially identified at the 3D-simulated images based on preoperative CT images. Most cases had suitable bony marks near the facet joint (
Demographic, clinical, and radiologic data were retrospectively collected from medical records and radiologic images. Radiologic evaluation was performed postoperative cervical radiographs and 1.0-mm interval CT scans using a Mx8000 IDT device (Philips Medical Systems, Best, Netherlands). Special attention was paid to the presence of a cortical breach of the PS, or the encroachment of the PS into the spinal canal or the vertebral foramen (
Of the 32 patients (64 screws) enrolled in this study, 15 were men and 17 were female. The mean patient age was 67.8±13.0 years (range, 38–86 years). Preoperative diagnoses included 18 cervical spondylotic myelopathies, 12 diagnoses of ossification of the posterior longitudinal ligament, and two diagnoses of cervical spondylotic radiculopathy. All patients underwent a posterior fusion operation with a screw-rod system, including PS insertion into C7, by the author's technique.
Of 64 screws, cortical breach was observed in three screws, including two screws in the right PS and one screw in the left PS. The three breaches occurred in the first five patients. Outside of the initial placements, there was no cortical breach in any cases. The three breached screws violated only the lateral cortex of the pedicle. Postoperative neurologic deterioration was not observed in any of enrolled patients, including the three screws with a cortical breach.
Here, we describe a new technique for free-had PS insertion in C7 without the aid of fluoroscopy. Cortical breach of the pedicle was observed on the postoperative CT scans of three (4.7%) out of total of 64 PS screws performed by our technique, and all of the three breached screws violated the lateral cortex of the affected pedicle. No postoperative neurologic deterioration was found to be associated with a PS cortical breach. The cortical breaches occurred in the first five patients. Thereafter, no breach occurred in 27 patients (54 screws). The data presented here indicated that this technique can allows for successful PS insertion in C7. Moreover, the technique is associated with low rates of cortical breach and postoperative neurologic complications, and with a short learning-curve period. In addition, since the technique presented here was performed only under a surgical microscope, in the absence of fluoroscopic guidance, PS placement in C7 may be achieved with minimal risk of radiation exposure and minimal risk of contamination from an intraoperative medical imaging machine, such as a C-arm.
Accurate PS placement in C7 is critical for stabilizing the vertebral segments. Among the three screw types (lateral mass screw, laminar screw, and PS), PS has been recognized as a superior option for posterior stabilization due to its high degree of strength, which can endure segmental motion [
A critical drawback regarding the use of a PS in C7 is that it is extremely difficult to position accurately. Moreover, cortical breach can occur during insertion, which may result in serious complications such as spinal cord injury. Since placement of a PS in C7 requires careful screw positioning, the majority of surgeons carry out PS placement under fluoroscopic guidance.
PS insertion in C7 has been recognized as a reasonable option for posterior stabilization; however, this procedure also has several drawbacks. Most importantly, intraoperative fluoroscopic lateral images of C7 bony structures, such as the pedicle and the vertebral body, are sometimes obscured by shoulder shadows, even when the patient is positioning properly (
The present study has some limitations. First, this is a retrospective study with a relatively small sample size. To better establish the feasibility of our technique for PS placement in C7, more studies with larger sample sizes and a prospective study design should be performed. Second, the distance measurement (CCAD or CVAD) during surgery should be verified to confirm the better radiological and clinical outcomes compared to conventional technique with angle measurement, although after surgery using our technique we were convinced that the measurement of CCAD or CVAD can be associated with more simple and precisely placement at C7 PS placement than conventional technique using angle. Thus, further studies of thoroughly comparing conventional technique and novel our technique for inserting C7 PS should be necessary. Finally, the determination of the ideal entry point for C7 PS was performed based on the preoperative data from 3D-simulation software. The utilization of 3D-simulation software may be a limitation because the software has not been widely utilized. However, due to the paucity of articles describing PS insertion techniques without fluoroscopic guidance, this study can be considered to be a cornerstone for further research of free-hand techniques that do not require fluoroscopic guidance for insertion of a PS into the cervical spine.
Here, the authors introduce a new free-hand technique for PS insertion in C7. The data indicate that this technique allows safe and feasible PS placement in C7. Moreover, this technique has low rates of cortical breach and no postoperative neurologic complications, as well as a short learning-curve. In addition, since this technique was performed only under a surgical microscope without fluoroscopic guidance, it is associated with a reduced risk of radiation exposure and contamination by intraoperative imaging machines. Further studies with larger sample sizes and longer follow-up times are needed to validate the feasibility and availability of the technique.
This study was presented at Cervical Spine Research Society, Asia-Pacific section (CSRS-AP) in 2015.