Freehand technique for C2 pedicle and pars screw placement: is it safe?

doi:10.1016/j.spinee.2017.11.010

The Spine Journal

Volume 18, Issue 7, July 2018, Pages 1197-1203

https://doi.org/10.1016/j.spinee.2017.11.010 Get rights and content

Abstract

Background Context

During placement of C2 pedicle and pars screws, intraoperative fluoroscopy is used so that neurovascular complications can be avoided, and screws can be placed in the proper position. However, this method is time consuming and increases radiation exposure. Furthermore, it does not guarantee a completely safe and accurate screw placement.

Purpose

The objective of this study was to evaluate the safety of the C2 pedicle and pars screw placement without fluoroscopic or other guidance methods.

Study Design

This is a retrospective comparative study.

Patient Sample

One hundred ninety-eight patients who underwent placement of C2 pedicle or pars screws without any intraoperative radiographic guidance were included in the study.

Outcome Measures

Medical records and postoperative computed tomography (CT) scans were evaluated.

Materials and Methods

Clinical data were reviewed for intraoperative and postoperative complications. The accuracy of screw placement was evaluated with postop CT scans using a previously published cortical-breach grading system (described by the location and the percentage of the screw diameter over the cortical edge [0=none, Grade I≤25% of the screw diameter, Grade II=26%–50%, Grade III=51%–75%, and Grade IV=76%–100%]).

Results

A total of 148 pedicle screws and 219 pars screws were inserted by two experienced surgeons. There were no cases of cerebral spinal fluid leakage and no neurovascular complications during screw placement. Postoperative CT scans were available for 76 patients, which included 52 pedicle screws and 87 pars screws. For cases with C2 pedicle screws, there were 12 breaches (23%); these included 10 screws with a Grade I breach (19%), 1 screw with a Grade II breach (2%), and 1 screw with a Grade IV breach (2%). Lateral breaches occurred in seven screws (13%), inferior breaches occurred in three screws (6%), and superior breaches occurred in two screws (4%). For cases with C2 pars screws, there were 10 breaches (11%); these included 6 screws with a Grade I breach (7%), 2 screws with a Grade II breach (2%), and 2 screws with a Grade IV breach (2%). Medial breaches were found in four (5%), lateral breaches in two (2%), inferior breaches in two (2%), and superior breaches in two (2%). Two of the cases with superior breaches (one for pedicle and one for pars) experienced occipital neuralgia months after surgery. There was no statistically significant difference in the incidence of overall and high-grade breaches between the groups (p=.07 and 1.0, respectively).

Conclusions

Although even in experienced hands up to 23% of C2 pedicle screws and 11% of C2 pars screws placed using a freehand technique without guidance may be malpositioned, a clear majority of malpositioned screws demonstrated a low-grade breach, and only 2 of 198 patients (1%) experienced complications related to screw placement.

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)

Application of novel self-designed surgical tools for the safe C2 pedicle screw placement in 12 patients with Hangman fracture
2023, Asian Journal of Surgery
Preliminary experience with a novel facet-based lateral mass drill guide for the placement of lateral mass screws compared to freehand technique: a cadaveric study
2023, Spine Journal
Lateral mass screw fixation is the standard for posterior subaxial cervical fixation. Several freehand surgical techniques for placing lateral mass screws have been described which rely on anatomical landmarks and surgeon mastery of the technique to safely place screws. The accuracy of these freehand techniques is inherently variable and can be influenced by a surgeon's level of clinical experience. A novel technique was developed that utilizes the plane of the facet joint to create lateral mass screw pilot holes parallel with the joint line to improve the safety and accuracy of lateral mass screw placement regardless of experience.
To assess the safety and accuracy of lateral mass screw placement using a novel lateral mass drill guide instrument (LM Guide), compared to standard freehand technique.
Randomized cadaveric study utilizing multiple surgeon evaluators to compare the safety and accuracy of guided cervical lateral mass placement compared to traditional freehand techniques.
Lateral mass screws were placed from C3 to C7 in 20 cadaver specimens by 8 spine surgeons of varying levels of clinical experience (4 attendings, 4 fellows). Screws were placed bilaterally using standard anatomic landmarks (“freehand”) randomly allocated on one side and using the LM Guide on the other. Cadaveric specimens were imaged with high-resolution CT to assess screw placement. Zone grading for safety was conducted based on screw tip position and clinical severity of screw breach was based on proximity to surrounding neurovascular anatomy. Screws were graded as safe, at-risk, or critical, with at-risk and critical screws considered malpositioned. To assess the accuracy of screw trajectory placed using the LM Guide compared to freehand, sagittal screw angle was measured and compared to an “ideal” screw path parallel to the facet joint line. Freehand and LM Guide groups were compared using Pearson's chi-square correlation.
Screw placement using the LM guide yielded a significantly lower rate of screw malpositioning, with 7 of 91 (7.7%) compared with 18 of 99 (18.2%) screws placed in the At-Risk or Critical Zones, p<.05. Of the 91 screws inserted using the LM Guide, 84 (92.3%) were in the Safe Zone, 7 (7.7%) were At-Risk, and 0 were in Critical zones. There was no incidence of neural or transverse foramen breaches with the LM Guide. In comparison, for the 99 screws inserted freehand, 81 (81.8%) were Safe, 14 (14.1%) were At-Risk, and 4 (4.1%) were in Critical zones. The 4 Critical zone freehand screw breaches included 1 neural foramen breach, 2 transverse foramen breaches, and 1 facet breach. The LM Guide also resulted in higher accuracy of screw trajectory, as indicated by a significant reduction in sagittal screw angle compared with freehand, p<.01. Notably, in the less-experienced surgeon cohort, the LM Guide significantly reduced the sagittal screw angle and resulted in no critical screw breaches compared to 3 critical breaches with freehand technique suggesting there might be a benefit in decreasing the learning curve associated with lateral mass screw placement.
Lateral mass screw placement with a novel LM Guide that uses the facet joint to control screw trajectory improved the accuracy and reproducibility of screw placement with a significant reduction in screw breach rate and sagittal screw angle compared to freehand techniques regardless of surgeon experience level.
The inherent variability of freehand lateral mass screw placement can increase the risk of clinical complications associated with screw malpositioning. The technique presented in this cadaveric study may be a viable alternative to standard freehand technique that can improve the overall safety of lateral mass screw placement.
The C2 Cortical Screw, an Alternative Fixation Technique for the C2 Segment During High Cervical Spine Surgery: Technical Note
2020, World Neurosurgery
Citation 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.
For posterior fixation of C2 vertebra (the axis), several fixation techniques such as pedicle screw, laminar screw, and pars screw have been reported. A pedicle screw (PS) is considered the strongest among the techniques, but certain situations make PS fixation impossible or difficult. These include patients with a narrow C2 pedicle or high-riding vertebral artery. We introduced an alternative screw technique for C2 that addressed the aforementioned problems with safely placing it, which we termed a cortical screw (CS) for C2.
Among a total of 28 cases using C2 CS for high cervical spine surgery, 2 cases using C2 CS were described. One patient was a 76-year old woman with a gait disturbance and myelopathic symptoms and diagnosed with C1-C2 myelopathy and translational instability. The other case was 54-year old man with posterior neck pain after traffic accident and diagnosed with C1-C2 fracture-dislocation. We used the C2 CS as an alternative technique for high cervical spine surgery in these patients and describe the ideal entry point and trajectory.
A postoperative computed tomography scan confirmed proper positioning of the C1 posterior arch screw and C2 CS, with satisfactory reduction of the C2 dens and adequate restoration of the C1-C2 spinal canal. The patient experienced no screw-related postoperative complications, and postoperative 1-year computed tomography images showed that solid union and good alignment of C1-2 segment was achieved.
C2 CS can be suitable alternative for C2 screw fixation technique in posterior high cervical spine fusion surgery.
Freehand C2 Pedicle Screw Placement: Surgical Anatomy and Operative Technique
2019, World Neurosurgery
We present a surgical video demonstrating the anatomy and technique of freehand C2 pedicle screw placement using a cadaveric specimen and 3-dimensional simulation software. C2 pedicle screws have been shown to augment cervical constructs and provide increased biomechanical stability compared with pars screws due to the increased length and bony purchase of pedicle screws within the pedicle and vertebral body.¹ The presence of vertebral artery variations within the transverse foramen may preclude pedicle screw placement, and these should be identified on preoperative imaging. The C2 pedicle can be directly palpated at the time of screw placement, which aids screw placement in cases of deformity or trauma. A freehand technique without the use of computed tomography scan guidance or intraoperative fluoroscopy decreases radiation exposure for the operator and patient and has been shown to be safe for patient-related outcomes.2, 3, 4, 5 Complete exposure of the C2 posterior elements is key to identifying the pedicle. The trajectory is based on direct visualization of the medial and superior pedicle borders to avoid lateral or inferior breaches into the transverse foramen. A curved probe is used for access into the vertebral body, respecting the outer cortical walls of the pedicle. The intraosseous position is confirmed with a ball-tipped probe. Fluoroscopy should be performed after screw placement to confirm proper position. By accomplishing proper exposure and understanding the anatomy of the C2 pedicle, the placement of C2 pedicle screws using a freehand technique is a safe and efficient technique for high cervical fixation.
Comparison of the S8 navigation system and the TINAVI orthopaedic robot in the treatment of upper cervical instability
2024, Scientific Reports
Effect of High-Riding Vertebral Artery on the Accuracy and Safety of C2 Pedicle Screw Placement in Basilar Invagination and Related Risk Factors
2024, Global Spine Journal

View all citing articles on Scopus

: 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.

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Clinical StudyFreehand technique for C2 pedicle and pars screw placement: is it safe?

Abstract

Background Context

Purpose

Study Design

Patient Sample

Outcome Measures

Materials and Methods

Results

Conclusions

Introduction

Section snippets

Materials and methods

Results

Discussion

Conclusions

Am J Surg

Chin J Traumatol

World Neurosurg

Spine J

Atlanto-axial arthrodesis by the wedge compression method

J Bone Joint Surg Am

The interspinous method of posterior atlantoaxial arthrodesis

J Neurosurg

Modified Gallie technique versus transarticular screw fixation in C1-C2 fusion

Clin Orthop Relat Res

Primary posterior fusion C1/2 in odontoid fractures: indications, technique, and results of transarticular screw fixation

J Spinal Disord

Morphologic considerations of C2 isthmus dimensions for the placement of transarticular screws

Spine

Variation of the groove in the axis vertebra for the vertebral artery. Implications for instrumentation

J Bone Joint Surg Br

Preoperative determination of safe superior transarticular screw trajectory through the lateral mass

Spine

Posterior C1-C2 fusion with polyaxial screw and rod fixation

Spine

Atlantoaxial fixation using plate and screw method: a report of 160 treated patients

Neurosurgery

Clinical Study
Freehand technique for C2 pedicle and pars screw placement: is it safe?