Clinical StudyFreehand technique for C2 pedicle and pars screw placement: is it safe?
Introduction
Techniques for posterior stabilization of the upper cervical spine that address atlantoaxial instability have been developed over decades. Originally, wiring techniques described by Gallie [1], Brooks and Jenkins [2], and Dickman et al. [3] were used, but they could not provide sufficient biomechanical stability to prevent rotational force and resulted in a high incidence of non-fusion [4]. To address this problem, Jeanneret and Magerl [5] introduced the C1–C2 transarticular screw fixation technique. This technique provides optimal stability and yields an excellent fusion rate, but has some limitations. First, the C1–C2 alignment must be correct before the insertion of the screws. Also, this technique is generally not feasible in patients with thoracic kyphosis as this would require a steep angle of screw trajectory. Finally, anatomical studies of C2 found that up to 22% of patients were not suitable candidates for transarticular screws because of an increased risk of vertebral artery (VA) injury [6], [7], [8].
Compared with transarticular screws, C1 lateral mass screws combined with C2 pedicle or C2 pars screws provide an alternative treatment for atlantoaxial instability. Several studies show that this instrumentation leads to high rates of arthrodesis [9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19]. C2 pedicle and pars screws are also used in occipitocervical and subaxial fixation to provide more rigid stability.
Despite their popularity, C2 pedicle and pars screw misplacement may result in neurovascular complications—especially VA injury. Intraoperative fluoroscopy and other guidance methods have been used to ensure safe placement of screws. However, these methods are time consuming and often expose patients to additional radiation. The aim of the present study was to evaluate the safety of freehand technique for C2 pedicle and pars screw placement as an alternative to intraoperative fluoroscopy or other guidance methods.
Section snippets
Materials and methods
A retrospective study was conducted using data from January 2005 to December 2015 at a single institution. We included patients over 18 years old who underwent posterior cervical fixation, without intraoperative radiographic guidance, with both C2 pedicle and pars screw placement. We excluded any patient with an infection, tumor, or traumatic fracture of the C2 vertebra that interfered with normal screw trajectory. Patients who underwent prior C2 pedicle or pars screw insertion were excluded as
Results
There were 198 cases enrolled in the study, including 90 men and 108 women (Table 1). Ages ranged from 20 to 86 years (mean 59.9 years). The reasons for surgery were degenerative disease in 137 patients (69%), deformity in 51 patients (26%), trauma in 7 patients (3.5%), congenital condition in 2 patients (1%), and inflammation in 1 patient (0.5%). A total of 122 patients (62%) had prior cervical surgery before undergoing C2 instrumented surgery.
The most common procedure was a multilevel
Discussion
Currently, pedicle and pars screws are accepted as the primary posterior C2 constructs for atlantoaxial, occipitocervical, and subaxial fixations [21]. These screws provide immediate stabilization and long-term fusion. Because of the variable anatomy of the C2 vertebra, a preoperative CT scan is generally necessary for surgeons to clearly define bony morphology and to decide on the proper screw trajectory. If a preoperative CT scan is not available, an MRI scan can be used for the same purpose,
Conclusions
The use of the freehand technique for C2 pedicle and pars instrumentation was safe without critical neurovascular complications. Preoperative assessment of anatomy for surgical planning combined with intraoperative tactile feedback ensured accurate screw placement.
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Cited by (25)
The C2 Cortical Screw, an Alternative Fixation Technique for the C2 Segment During High Cervical Spine Surgery: Technical Note
2020, World NeurosurgeryCitation Excerpt :First, it is difficult or impossible to place the PS when there is an inherent narrow pedicle or severe high riding vertebral artery (HRVA). Also, there is a risk of cortical violation of the C2 pedicle, which may cause critical problems such as cord injury from medial cortical violation or vertebral artery injury from lateral or inferior cortical violation.3,6 During C2 PS fixation, cortical violations of the pedicle may be more likely under specific conditions, particularly when there is severe kyphotic alignment of the cervical spine due to blood pooling around the PS entry point.
Freehand C2 Pedicle Screw Placement: Surgical Anatomy and Operative Technique
2019, World Neurosurgery
FDA device/drug status: Not applicable.
Author disclosures: PP: Nothing to disclose. KDR: Royalties: Biomet (B), Medtronic (B), outside the submitted work; Stock Ownership: Osprey (1% of all stock options), Expanding Orthopedics (<1%), Spineology (B, 1%), Nexgen (B, 1%), Amedica (B, 1%), Vertiflex (B, 1%), Benvenue (C, 1%), Spinal Kinetics (E), outside the submitted work; Consulting: Biomet (none), Medtronic (none), outside the submitted work; Speaking and Teaching Arrangements: Zeiss Teaching Webinar (B), outside the submitted work; Trips and Travel: AOSpine (none), outside the submitted work; Board of Directors: AOSpine (E), outside the submitted work; Research Support (Investigator Salary, Staff and Materials): AOSpine (none). BTK: Nothing to disclose. CP: Research Support (Investigator Salary, Staff and Materials): Pacira Pharmaceuticals (C, Paid directly to institution), outside the submitted work. TL: Nothing to disclose. JMB: Royalties: Globus Medical (E), Wolters Kluwer Health, Inc. (A), K2M (D), outside the submitted work; Consulting: Globus Medical (B), Medtronic (B), K2M (A), Stryker (B), outside the submitted work; Speaking and Teaching Arrangements: DePuy (B), Globus Medical (C), outside the submitted work; Fellowship Support: OMeGA (D, Paid directly to institution), AOSpine North America (E, Paid directly to institution), outside the submitted work.
The disclosure key can be found on the Table of Contents and at www.TheSpineJournalOnline.com.
No funds were received in support of this work.
There were no relevant financial activities outside the submitted work.