The effect of posterior bridging of C-1 on craniovertebral junction surgery

C0-C1 joint injection: Anatomical, clinical and technical review

Background

Cervicogenic headaches (CGH) are proven clinical entities. The prevalence of CGH arising from the atlanto-occipital (AO) joint is unknown. The best evidence for treatment of CGH is for third occipital nerve radiofrequency neurotomy. Treatment of CGH includes intra-articular injections into upper cervical spine joints.

Objective

To perform a review of the anatomy and clinical presentation of AO joint (AOJ) pain referral as well as a technical description to safely access the AOJ.

Methods

A literature review was performed to explore the intricacies of the cranio-cervical junction (CCJ) with a focus on the relation between the AOJ and vascular anatomy. Our technical approach is described with complementary images.

Results

The AOJ lies anterior to a venous sinus and slightly superior to the horizontally oriented vertebral artery crossing the joint line.

Conclusion

The authors propose a modified superior needle trajectory that seeks to avoid these vascular structures and to access the AOJ safely.

Low-dose three-dimensional CT angiography for the evaluation of posterolateral protrusion of the vertebral artery over the posterior arch of the atlas: a quantitative anatomical comparison study of the rotational and neutral positions

AIM

To investigate the changes in relevant anatomical parameters of posterolateral protrusion of the vertebral artery (VA) between head-neck rotational and neutral positions using low-dose three-dimensional computed tomography angiography (3D-CTA).

MATERIALS AND METHODS

Low-dose 3D-CTA images obtained for various craniocervical diseases in 36 non-dominant VA side patients with neutral, left and right head-neck rotational positions were evaluated. The relevant parameters from superior and inferior views, including external diameter (ED), internal diameter (ID), transverse diameter (TD), heights and diameters of posterolateral protrusion of the VA over the posterior arch of the atlas in the neutral and rotational positions, were recorded and compared.

RESULTS

There was no significant differences in the rotational angle (left/right: 31.23 ± 6.60/29.94 ± 6.09°, p>0.05). There were no significant differences in heights and diameters of bilateral VA between rotational and neutral positions (all p>0.05). The contralateral ID, ED, and TD of the rotational positions were significantly shorter than those of the neutral position (all p<0.05), while there were no significant differences in the three ipsilateral diameters (all p>0.05).

CONCLUSIONS

Posterolateral protrusion of the VA is not uncommon in the population, and surgeons should be aware of its presence, especially the increased possibility of injury to the VA caused by head-neck rotation, during the operation; thus, preoperative evaluation by low-dose 3D-CTA should be considered.

Morphometric Anatomy of the Posterior Aspect of the Atlas and the Vertebral Artery Groove in Relation to Lateral Mass Screw Placement

BACKGROUND

 Atlantoaxial instability is an important disorder that causes serious symptoms such as difficulties in walking, limited neck mobility, sensory deficits, etc. Atlantal lateral mass screw fixation is a surgical technique that has gained important recognition and popularity. Because accurate drilling area for screw placement is of utmost importance for a successful surgery, we aimed to investigate morphometry of especially the posterior part of C1.

METHODS

 One hundred and fifty-eight human adult C1 dried vertebrae were obtained. Measurements were performed directly on dry atlas vertebrae, and all parameters were measured by using a digital caliper accurate to 0.01 mm for linear measurements.

RESULTS

 The mean distance between the tip of the posterior arch and the medial inner edge of the groove was found to be 10.59 ± 2.26 and 10.49 ± 2.20 mm on the right and left, respectively. The mean distance between the tip of the posterior arch and the anterolateral outer edge of the groove was 21.27 ± 2.28 mm (right: 20.96 ± 2.22 mm; left: 21.32 ± 2.27 mm). The mean height of the screw entry zone on the right and left sides, respectively, were 3.86 ± 0.81 and 3.84 ± 0.77 mm. The mean width of the screw entry zone on both sides was 13.15 ± 1.17 and 13.25 ± 1.3 mm.

CONCLUSION

 Our result provided the literature with a detailed database for the morphometry of C1, especially in relation to the vertebral artery groove. We believe that the data in the present study can help surgeons to adopt a more accurate approach in terms of accurate lateral mass screw placement in atlantoaxial instability.

The Ponticulus Posticus as Risk Factor for Screw Insertion into the First Cervical Lateral Mass

BACKGROUND

Awareness of the osseous anomaly of ponticulus posticus (PP) is crucial in avoiding vertebral artery (VA) injuries during C1 instrumentation. The aim of this study was to investigate PP and its relationship with the VA with three-dimensional computed tomography angiography.

METHODS

PP and the VA were investigated as intraoperative landmarks. The intersection of the VA to the posterior arch of C1 and the medial line and the posterior arch and VA curve around lateral masses were measured as intraoperative references.

RESULTS

PP was identified in 14.3% of samples. The anomaly was more common in women and on the right side. Of cases, 48.2% had PP bilaterally. In PP cases, the VA had variable courses through C2 before it passed under its bony bridges on the posterior arch of C1. Mean distances were found at the intersection of the VA to the posterior arch of C1 and the medial line to be larger and the posterior arch of C1 and the VA curve around lateral masses to be narrower than normal cases. Dual computed tomography scan data from C1 with PP were used to create three-dimensional patient-specific life-sized cervical spine models. Models revealed how the bone bridge affected the VA. The feasibility (>4 mm) of a safe lateral mass screw fixation was not influenced by PP anomalies.

CONCLUSIONS

The presence of the PP loop can limit space available for placement of the screw through the bony elements of C1. Standard screw techniques are contraindicated owing to the unacceptable high risk of VA injury.

Prevalence of foramen arcuale and its clinical significance: a meta-analysis of 55,985 subjects

OBJECTIVE

The foramen arcuale (FA) is a bony bridge located over the vertebral artery on the posterior arch of the atlas. The presence of an FA can pose a risk during neurosurgery by providing a false impression of a broader posterior arch. The aim of this study was to provide the most comprehensive investigation on the prevalence of the FA and its clinically important anatomical features.

METHODS

Major electronic databases were searched to identify all studies that reported relevant data on the FA and the data were pooled into a meta-analysis.

RESULTS

A total of 127 studies (involving 55,985 subjects) were included. The overall pooled prevalence of a complete FA was 9.1% (95% CI 8.2%–10.1%) versus an incomplete FA, which was 13.6% (95% CI 11.2%–16.2%). The complete FA was found to be most prevalent in North Americans (11.3%) and Europeans (11.2%), and least prevalent among Asians (7.5%). In males (10.4%) the complete FA was more common than in females (7.3%) but an incomplete FA was more commonly seen in females (18.5%) than in males (16.7%). In the presence of a complete FA, a contralateral FA (complete or incomplete) was found in 53.1% of cases.

CONCLUSIONS

Surgeons should consider the risk for the presence of an FA prior to procedures on the atlas in each patient according to sex and ethnic group. We suggest preoperative screening with computerized tomography as the gold standard for detecting the presence of an FA.

Minimally invasive surgical treatment for Kimmerle anomaly

Introduction:

Kimmerle anomaly is the bony ridge between the lateral mass of atlas and its posterior arch or transverse process. This bony tunnel may include the V3 segment of the vertebral artery, vertebral vein, posterior branch of the C1 spinal nerve, and the sympathetic nerves, which results in the clinical symptoms of this disease. Reports on the surgical treatment of Kimmerle anomaly are rare. There are no reports on minimally invasive surgical treatment of this pathology.

Materials and Methods:

Six patients with Kimmerle anomaly were treated from 2015 until 2016. Three patients underwent routine surgery through the posterior midline (posterior midline approach [PMA] group). The other three patients underwent decompression with a paravertebral transmuscular approach (PTMA group). The operation time, intraoperative blood loss, clinical symptoms before and after surgery as well as intra- and post-operative complications were compared between the PTMA and PMA groups.

Results:

The results of the surgical treatments were assessed at discharge and 1 year later. Blood loss, operation time, and intensity of pain at the postoperative wound area were lower in the PTMA group. There were no postoperative complications. The delayed surgical treatment outcomes did not depend on the method of artery decompression.

Conclusions:

Surgical treatment of vertebral artery compression in patients with Kimmerle anomaly is preferable in cases where conservative treatment is inefficient. A minimally invasive PTMA is an alternative to the routine midline posterior approach, providing direct visualization of the compressed V3 segment of the vertebral artery and minimizing postoperative pain.

The feasibility of inserting a C1 pedicle screw in patients with ponticulus posticus: a retrospective analysis of eleven patients

BACKGROUND

Ponticulus posticus is a common anatomic variation that can be mistaken for a broad posterior arch during C1 pedicle screw placement. When the atlas lateral mass screws are placed via the posterior arch, injury to the vertebral artery may result. To our knowledge, there are few clinical studies that have analyzed the feasibility of C1 pedicle screw fixation in patients with ponticulus posticus, in clinical practice.

PURPOSE

To evaluate the feasibility of inserting a C1 pedicle screw in patients with ponticulus posticus.

METHODS

Between January 2008 and January 2012, 11 consecutive patients with atlantoaxial instability, and with a ponticulus posticus at C1, underwent posterior fusion surgery in our institution. According to preoperative computed tomography (CT) reconstruction, a complete ponticulus posticus was found unilaterally in nine patients and bilaterally in two. Postoperative CT reconstructive imaging was performed to assess whether C1 pedicle screw placement was successful. Patients were followed up at regular intervals and evaluated for symptoms of ponticulus posticus syndrome.

RESULTS

Thirteen C1 pedicles (atlas vertebral artery groove), each with a complete ponticulus posticus, were successfully inserted with thirteen 3.5- or 4.0-mm diameter pedicle screws, without resection of the bony anomaly. No intraoperative complications (venous plexus, vertebral artery, or spinal cord injury) occurred. The mean follow-up period was 21 (range 14-30) months. Postoperative CT reconstructive images showed that all 13 pedicle screws were inserted in the C1 pedicles without destruction of the atlas pedicle cortical bone. In the follow-up period, none of the patients demonstrated clinical symptoms of ponticulus posticus syndrome or developed bone fusion.

CONCLUSION

Three-dimensional CT imaging should be considered prior to C1 pedicle screw fixation in patients with ponticulus posticus, to avoid mistaking the ponticulus posticus for a widened dorsal arch of the atlas. If there is no ponticulus posticus syndrome preoperatively, C1 pedicle screw fixation can be successfully performed without removing the bony anomaly.

Normal anatomy and anatomic variants of vascular foramens in the cervical vertebrae: a paleo-osteological study and review of the literature

We investigated 923 cervical vertebrae belonging to late-antiquity and medieval skeletal remains and assessed the qualitative and quantitative structural characteristics of transverse foramens (TF) and additional vascular canals. We also reviewed the pertinent literature. Double TF were chiefly observed in C6 (with a right/left side prevalence of 35.7 and 44.4%, respectively) and C5 vertebrae (23.6 and 23.9%, right/left side, respectively), while unclosed TF were mainly documented in C1 vertebrae (8.4%). Retrotransverse canal and retrotransverse groove were present in 8.5 and 17.8%, respectively, of C1 vertebrae examined, while arcuate foramens and supertransverse foramens were found in 7.3 and 3.7% of specimens, respectively. TF diameter decreased from C6 to C2 vertebrae, being smallest in C7 and greatest in C1 vertebrae, with no left/right significant difference. There was a significant correlation between TF diameter and stature, but only on the right side. The mean area of the arcuate foramen was lower than the mean area of the ipsilateral TF (24.5 ± 5.7 vs 28.5 ± 7.7 mm(2), respectively; p = 0.048), possibly causing compression of the vertebral artery within the arcuate foramen. The study of human vertebrae excavated from archaeological sites is a simple and effective way to analyze the morphology and quantitative anatomy of vascular foramens.

The prevalence of posticus ponticus: retrospective analysis of radiographs from a chiropractic health center

OBJECTIVE

The potential clinical significance of posticus ponticus is controversial because the majority of patients with this finding are asymptomatic. This study sought to estimate the prevalence of posticus ponticus in a chiropractic college clinic patient population.

METHODS

From the archived records in the College Health Center, 304 lateral cervical spine radiographs were randomly selected and assessed by 2 independent examiners for the presence of posticus ponticus in any of its forms. The number of radiographs showing posticus ponticus, as well as analysis of agreement between examiners, was obtained.

RESULTS

There were 60 radiographs where the examiners disagreed as to the presence or absence of posticus ponticus. These 60 were not counted for prevalence of posticus ponticus but were included in the κ analysis. Among the remaining 246 radiographs, 112 (46%) showed some type of posticus ponticus, whereas 132 (54%) did not show any posticus ponticus finding. Examiners A and B showed a κ score agreement of 0.72, and examiners C and D showed a κ score agreement of 0.51.

DISCUSSION

The κ scores for both sets of examiners show acceptable agreement. Within this population, the finding of 45.9% prevalence of some type of posticus ponticus was determined. Compared with other studies, the prevalence of posticus ponticus was found to range between 9% and 72%.

CONCLUSION

Within this sample, 45.9% of radiographs showed some type of posticus ponticus.

Anomalous vertebral artery in craniovertebral junction with occipitalization of the atlas

STUDY DESIGN.: Observational study with 3-dimensional computed tomography angiography analysis. OBJECTIVE.: To examine the course of the vertebral artery (VA) at the craniovertebral junction (CVJ) in individuals with occipitalization of the atlas. SUMMARY OF BACKGROUND DATA.: The anatomy of the VA at the CVJ should be completely understood to decrease the risk of iatrogenic injury. Although quantitative anatomic studies have focused on the normal VA, the anomalous VA with occipitalization of the atlas has not been fully explored. METHODS.: A consecutive series of 36 cases with occipitalization of the atlas underwent 3-dimensional computed tomography angiography. Seventy-two vertebral arteries were analyzed. In this setting, the safety of placing lateral mass screws (LMS) was studied. RESULTS.: Four different pathways of the VA at the CVJ with occipitalization of the atlas were found. Type I, wherein the VA enters the spinal canal below the C1 posterior arch, and the course of the VA is below the occipitalized C1 lateral mass (8.3% of 72 vertebral arteries); Type II, the VA enters the spinal canal below the C1 posterior arch, and the course of the VA is on the posterior surface of the occipitalized C1 lateral mass, or makes a curve on it (25%); Type III, wherein the VA ascends externally laterally after leaving the axis transverse foramen, enters an osseous foramen created between the atlas and occipital bone, then into the cranium (61.1%); and Type IV, in which the VA is absent (5.6%). CONCLUSION.: Four types of VA with occipitalization of the atlas are confirmed. Type-I and type-IV VA have relatively low risks for C1 LMS perforation. Type-II and type-III anomalies will probably increase the risk of VA injury during C1 LMS placement. Definite caution should also be taken during the procedure on the contralateral side of a type-IV VA.

Posterolateral protrusion of the vertebral artery over the posterior arch of the atlas: quantitative anatomical study using three-dimensional computed tomography angiography

Object

The vertebral artery (VA) often takes a protrusive course posterolaterally over the posterior arch of the atlas. In this study, the authors attempted to quantify this posterolateral protrusion of the VA.

Methods

Three-dimensional CT angiography images obtained for various cranial or cervical diseases in 140 patients were reviewed and evaluated. Seven patients were excluded for various reasons. To quantify the protrusive course of the VA, the diameter of the VA and 4 parameters were measured in images of the C1–VA complex obtained in the remaining 133 patients. The authors also checked for anomalies and anatomical variations.

Results

When there was no dominant side, mean distances from the most protrusive part of the VA to the posterior arch of the atlas were 6.73 ± 2.35 mm (right) and 6.8 ± 2.15 mm (left). When the left side of the VA was dominant, the distance on the left side (8.46 ± 2.00 mm) was significantly larger than that of the right side (6.64 ± 2.0 mm). When compared by age group (≤ 30 years, 31–60 years, and ≥ 61 years), there were no significant differences in the extent of the protrusion. When there was no dominant side, the mean distances from the most protrusive part of the VA to the midline were 30.73 ± 2.51 mm (right side) and 30.79 ± 2.47 mm (left side). When the left side of the VA was dominant, the distance on the left side (32.68 ± 2.03 mm) was significantly larger than that on the right side (29.87 ± 2.53 mm). The distance from the midline to the intersection of the VA and inner cortex of the posterior arch of the atlas was ~ 12 mm, irrespective of the side of VA dominance. The distance from the midline to the intersection of the VA and outer cortex of the posterior arch was ~ 20 mm on both sides. Anatomical variations and anomalies were found as follows: bony bridge formation over the groove for the VA on the posterior arch of C-1 (9.3%), an extracranial origin of the posterior inferior cerebellar artery (8.2%), and a VA passing beneath the posterior arch of the atlas (1.8%).

Conclusions

There may be significant variation in the location and branches of the VA that may place the vessel at risk during surgical intervention. If concern is noted about the vulnerability of the VA or its branches during surgery, preoperative evaluation by CT angiography should be considered.

The frequency and clinical significance of congenital defects of the posterior and anterior arch of the atlas

OBJECT

In this study the authors investigated the anatomical, clinical, and imaging features as well as incidence of congenital defects of the C-1 arch.

METHODS

The records of 1104 patients who presented with various medical problems during the time between January 2006 and December 2006 were reviewed retrospectively. The craniocervical computed tomography (CT) scans obtained in these patients were evaluated to define the incidence of congenital defects of the posterior arch of C-1. In addition, 166 dried C-1 specimens and 84 fresh human cadaveric cervical spine segments were evaluated for anomalies of the C-1 arch.

RESULTS

Altogether, 40 anomalies (2.95%) were found in 1354 evaluated cases. Of the 1104 patients in whom CT scans were acquired, 37 (3.35%) had congenital defects of the posterior arch of the atlas. The incidence of each anomaly was as follows: Type A, 29 (2.6%); Type B, six (0.54%); and Type E, two (0.18%). There were no Type C or D defects. One patient (0.09%) had an anterior arch cleft. None of the reviewed patients had neurological deficits or required surgical intervention for their anomalies. Three cases of Type A posterior arch anomalies were present in the cadaveric specimens.

CONCLUSIONS

Most congenital anomalies of the atlantal arch are found incidentally in asymptomatic patients. Congenital defects of the posterior arch are more common than defects of the anterior arch.