Imaging anatomy and variation of vertebral artery and bone structure at craniocervical junction

Exploring the atlantic part of the vertebral artery in the South Indian population and its implications in spine surgery

STUDY DESIGN

A descriptive, quantitative cross-sectional study of the atlantic part (V3) of the vertebral artery (VA).

PURPOSE

This study aimed to bridge the research gap in the morphometry of the V3 segment of the VA in the South Indian population.

OVERVIEW OF LITERATURE

The microsurgical anatomy of this segment of the VA has been explored in various populations, and a thorough understanding of the anatomy and course of the VA, particularly the V3 segment, is essential to prevent iatrogenic complications. Several computed tomography studies but a few cadaveric studies have explored the V3 segment of the VA in the South Indian population.

METHODS

This study examined 40 VAs from 20 embalmed cadavers that were obtained from the voluntary donation program, and Institutional Ethical Clearance was obtained before the study. The length, diameter, and angle of the vertical, horizontal, and exit parts of the V3 segment of the VA were documented after its exposure.

RESULTS

The mean lengths of the right and left VAs on each part were nearly similar, except for the mean length of the horizontal part (right: 38.937 mm, left: 40.237 mm) and total length of the V3 segment (right: 66.870 mm, left: 70.350 mm).

CONCLUSIONS

These morphometric parameters are essential to spine surgeons who intend to operate on a small part (vertical, horizontal, or exit part) of the V3 segment of the VA. The mean values of the parameters obtained in this study give average measurements or safe limits to surgeons for safe surgical procedures such as the occipital condyle screw technique and C1 laminectomy.

Spectral computed tomography with inorganic nanomaterials: State-of-the-art

Recently, spectral computed tomography (CT) technology has received great interest in the field of radiology. Spectral CT imaging utilizes the distinct, energy-dependent X-ray absorption properties of substances in order to provide additional imaging information. Dual-energy CT and multi-energy CT (Spectral CT) are capable of constructing monochromatic energy images, material separation images, energy spectrum curves, constructing effective atomic number maps, and more. However, poor contrast, due to neighboring X-ray attenuation of organs and tissues, is still a challenge to spectral CT. Hence, contrast agents (CAs) are applied for better differentiation of a given region of interest (ROI). Currently, many different kinds of inorganic nanoparticulate CAs for spectral CT have been developed due to the limitations of clinical iodine (I)-based contrast media, leading to the conclusion that inorganic nanomedicine applied to spectral CT will be a powerful collaboration both in basic research and in clinics. In this review, the underlying principles and types of spectral CT techniques are discussed, and some evolving clinical diagnosis applications of spectral CT techniques are introduced. In particular, recent developments in inorganic CAs used for spectral CT are summarized. Finally, the challenges and future developments of inorganic nanomedicine in spectral CT are briefly discussed.

Treatment of Reducible Atlantoaxial Dislocation and Basilar Invagination Using the Head Frame Reduction Technique and Atlantoaxial Arthrodesis

STUDY DESIGN

Retrospective case series.

OBJECT

To evaluate the outcomes of a head frame reduction and atlantoaxial arthrodesis technique for the treatment of reducible basilar invagination (BI) and atlantoaxial dislocation (AAD).

METHODS

Seventy-two reducible BI and AAD cases who were treated with the head frame reduction and atlantoaxial arthrodesis technique from June 2015 to December 2018 were retrospectively analyzed. Radiological measurements including the atlantodental interval (ADI), the height of odontoid process above Chamberlain line, Wackenheim line, clivus-canal angle (CCA) and JOA score were evaluated.

RESULTS

There was no death in this series. The follow-up period ranged from 6 to 32 months (mean: 21.2 months). Radiological, complete or 90% reduction was attained and complete decompression was demonstrated in all patients. The CCA increased from 123.22 ± 8.36 preoperatively to 143.05 ± 8.79 postoperatively (P < 0.01). There was no patient found postoperative dysphagia. Neurological improvement was observed in all patients, with the JOA scores increasing from 12.53 ± 1.93 preoperatively to 16.13 ± 1.23 postoperatively (P < 0.01). Solid bony fusion was demonstrated in 69 patients at follow-up (95.8%).

CONCLUSION

Head frame reduction technique is a simple and effective treatment which could relief neurologic compression and adjust the CCA in patients with reducible AAD and BI with lower potential risks. Atlantoaxial fixation with short segmental fixation, strong purchase and low shearing force could maintain superior stabilization. The safety and long-term efficacy of such fixation and reduction technique were favorable, which illustrated that it could be a promising treatment algorithm for such kind of disease.

Three-Dimensional Evaluation and Classification of the Anatomy Variations of Vertebral Artery at the Craniovertebral Junction in 120 Patients of Basilar Invagination and Atlas Occipitalization

BACKGROUND

Patients with basilar invagination and atlas occipitalization usually present abnormal anatomy of the vertebral arteries (VAs) at the craniovertebral junction (CVJ).

OBJECTIVE

To describe and further classify different types of VA variations at the CVJ with 3D visualization technology.

METHODS

One hundred twenty patients with basilar invagination and atlas occipitalization who had undergone 3-dimensional computed tomographic angiography (3D-CTA) were retrospectively studied. Imaging data were processed via the separating, fusing, opacifying, and false-coloring-volume rendering technique. Abnormal anatomy of the VA at the CVJ was categorized and related anatomic parameters were measured.

RESULTS

Seven different types were classified. Type I, VAs enter the cranium after leaving VA groove on the posterior arch of atlas (26.7% of 240 sides); Type II, VAs enter an extraosseous canal created in the assimilated atlas lateral mass-occipital condyle complex before reaching the cranium (53.3%); Type III, VA courses above the axis facet or curves below the atlas lateral mass then enter the cranium (11.7%); Type IV, VAs enter the spinal canal under the axis lamina (1.3%); Type V, high-riding VA (31.3%); Type VI, fenestrated VA (2.9%); Type VII, absent VA (4.2%). Distance from the canal of Type II VA to the posterior facet surface of atlas lateral mass (5.51 ± 2.17 mm) means a 3.5-mm screw can be safely inserted usually. Shorter distance from the midline (13.50 ± 4.35) illustrates potential Type III VA injury during exposure. Decreased height and width of axis isthmus in Type V indicate increased VA injury risks.

CONCLUSION

Seven types of VA variations were described, together with valuable information helpful to minimize VA injury risk intraoperatively.

C2 medial pedicle screw: a novel "in-out-in" technique as an alternative option for posterior C2 fixation in cases with a narrow C2 isthmus

OBJECTIVE

The authors describe a novel "in-out-in" technique as an alternative option for posterior C2 screw fixation in cases that involve narrow C2 isthmus. Here, they report the preliminary radiological and clinical outcomes in 12 patients who had a minimum 12-month follow-up period.

METHODS

Twelve patients with basilar invagination and atlantoaxial dislocation underwent atlantoaxial reduction and fixation. All patients had unilateral hypoplasia of the C2 isthmus that prohibited insertion of pedicle screws. A new method, the C2 medial pedicle screw (C2MPS) fixation, was used as an alternative. In this technique, the inner cortex of the narrow C2 isthmus was drilled to obtain space for screw insertion, such that the lateral cortex could be well preserved and the risk of vertebral artery injury could be largely reduced. The C2MPS traveled along the drilled inner cortex into the anterior vertebral body, achieving a 3-column fixation of the axis with multicortical purchase.

RESULTS

Satisfactory C2MPS placement and reduction were achieved in all 12 patients. No instance of C2MPS related vertebral artery injury or dural laceration was observed. There were no cases of implant failure, and solid fusion was demonstrated in all patients.

CONCLUSIONS

This novel in-out-in technique can provide 3-column rigid fixation of the axis with multicortical purchase. Excellent clinical outcomes with low complication rates were achieved with this technique. When placement of a C2 pedicle screw is not possible due to anatomical constraints, the C2MPS can be considered as an efficient alternative.

Avoiding iatrogenic injuries to the vertebral artery: A morphometric study of the vertebral artery-free dissection area

OBJECTIVE

To determine the area of a safety window that excludes the vertebral artery for the safe access of the occipital condyle screws during occipitocervical fixation.

METHODS

This study included 138 cervical computed tomography angiograms. Six measurements per side were made in each imaging study. These measurements are from the vertebral artery to (A) the mastoid process, (B) the mastoid incisura, (C) the posterior condylar fossa, (D) the occipital condyle in its midline, and (E) the medial border of the condyle. We also measured from the tip of the mastoid process to the lower border of the occipital condyle on its lateral side (F).

RESULTS

A total of 276 areas from 138 individuals were included, of which 51.4 % were men. The mean age was 54.2 ± 18.63 years. The mean variable measurements (mm) for all the population were 21 ± 4, 16 ± 3, 6 ± 2, 3 ± 2, 2 ± 1 and 35 ± 4 for variables A-F, respectively. We found significant differences between sex when we compared measurements A (p = 0.003), C (p = 0.001), D (p = 0.000) and F (p = 0.000). The incidence rate of dominance for the vertebral artery was 18.8 % and 30.4 % for right and left respectively.

CONCLUSION

Women had significantly smaller measures than men. This could indicate a higher risk of iatrogenic injury secondary to a smaller vertebral artery-free area. Results may guide surgeons in the pre-surgical planning aiming to reduce the risk of iatrogenic injuries to the vertebral artery.

Biomechanical evaluation of two alternative techniques to the Goel-Harms technique for atlantoaxial fixation: C1 lateral mass-C2 bicortical translaminar screw fixation and C1 lateral mass-C2/3 transarticular screw fixation

OBJECTIVE

The authors conducted a study to investigate the biomechanical feasibility and stability of C1 lateral mass-C2 bicortical translaminar screw (C1LM-C2TL) fixation, C1 lateral mass-C2/3 transarticular screw (C1LM-C2/3TA) fixation, and C1LM-C2/3TA fixation with transverse cross-links (C1LM-C2/3TACL) as alternative techniques to the Goel-Harms technique (C1 lateral mass-C2 pedicle screw [C1LM-C2PS] fixation) for atlantoaxial fixation.

METHODS

Eight human cadaveric cervical spines (occiput-C7) were tested using an industrial robot. Pure moments that were a maximum of 1.5 Nm were applied in flexion-extension (FE), lateral bending (LB), and axial rotation (AR). The specimens were first tested in the intact state and followed by destabilization (a type II odontoid fracture) and fixation as follows: C1LM-C2PS, C1LM-C2TL, C1LM-C2/3TA, and C1LM-C2/3TACL. For each condition, the authors evaluated the range of motion and neutral zone across C1 and C2 in all directions.

RESULTS

Compared with the intact spine, each instrumented spine significantly increased in stability at the C1-2 segment. C1LM-C2TL fixation demonstrated similar stability in FE and LB and greater stability in AR than C1LM-C2PS fixation. C1LM-C2/3TA fixation was equivalent in LB and superior in FE to those of C1LM-C2PS and C1LM-C2TL fixation. During AR, the C1LM-C2/3TA-instrumented spine failed to maintain segmental stability. After adding a cross-link, the rotational stability was significantly increased in the C1LM-C2/3TACL-instrumented spine compared with the C1LM-C2/3TA-instrumented spine. Although inferior to C1LM-C2TL fixation, the C1LM-C2/3TACL-instrumented spine showed equivalent rotational stability to the C1LM-C2PS-instrumented spine.

CONCLUSIONS

On the basis of our biomechanical study, C1LM-C2TL and C1LM-C2/3TACL fixation resulted in satisfactory atlantoaxial stabilization compared with C1LM-C2PS. Therefore, the authors believe that the C1LM-C2TL and C1LM-C2/3TACL fixation may serve as alternative procedures when the Goel-Harms technique (C1LM-C2PS) is not feasible due to anatomical constraints.

Vertebral artery segment at the suboccipital dural penetration site: an anatomical study using magnetic resonance imaging

PURPOSE

The morphology of the vertebral artery (VA) segment at the suboccipital dural penetration site has little been explored with magnetic resonance imaging (MRI). Therefore, the aim of this study was to examine the structure using MRI.

METHODS

In total, 94 patients underwent thin-sliced, contrast MRI in the axial, coronal, and sagittal planes involving the atlas, axis, occipital bone, and V3 and V4 segments of the VA.

RESULTS

The VA segment at the suboccipital dural penetration site was well-delineated in 93% on the axial images and in 95% on the coronal images. The axial images showed that 82% of the VA penetration sites were located in the middle third of the dural sac. Meanwhile, the coronal images revealed that the heights of both VA penetration sites were located at the same level in 87%. The axial VA penetration angle, which is formed by the VA and tangential line of the dural sac, was 66 ± 11.9° on the right side and 61 ± 14.1° on the left side. The coronal VA penetration angle, which is formed by the tangential line of the VA and dural sac, was 111 ± 24.6° on the right side and 112 ± 19.9° on the left side.

CONCLUSIONS

The morphology of the VA segment is considerably variable at the suboccipital dural penetration site, while most penetration sites are located in the middle third of the dural sac on axial MRI. These should be assumed during surgeries around the suboccipital VA penetration site.

Unilateral Aplasia versus Bilateral Aplasia of the Vertebral Artery: A Review of Associated Abnormalities

Morphological characteristics of 108 cases of uni- and bilateral aplasia of the vertebral artery (VA) in reports or images of retrospective studies, including one recent case, published between 1967 and 2016 are analyzed. Incidence, gender, persistence of carotid-vertebrobasilar anastomosis (CVBA), associated with other vascular variants, and vascular pathology in each group of uni- and bilateral VA aplasia are mutually compared. Most of the cases of VA aplasia in ages 31 to 80 were discovered in USA, Japan, and India. The bilateral VA aplasia is more common in the male gender than in the female one. The side of the VA aplasia had a significant effect on the side of CVBA persistence. Associated aplasia of other arteries was more common in cases of unilateral VA aplasia. The left VA was more commonly hypoplastic in cases of single right VA aplasia than the right VA in cases of single left VA aplasia. Aneurysms of definitive arteries were more frequent in cases of single right VA aplasia than in cases of single left VA aplasia. We claim that the aplasia of the VA probably depends on genetic factors in some races, while diseases are expressed usually in persons over 30 years of age.

The computed tomography angiography study of the spatial relationship between C1 transpedicular screw trajectory and V3 segment of vertebral artery

BACKGROUND CONTEXT

To our knowledge, there is no study that has systematically analyzed the relationship between C1 transpedicular screw trajectory and V3 segment of vertebral artery (VA V3 segment).

PURPOSE

To study the relationship between C1 transpedicular screw trajectory and VA V3 segment.

STUDY DESIGN

A morphologic computed tomography angiography (CTA) analysis of the spatial relationship between C1 transpedicular screw trajectory and VA V3 segment.

METHODS

Measurements were made on a workstation by using CTA data of 62 patients. Firstly, parameters related to the relationship between C1 vertebral artery groove (VAG) and vertebral artery (VA) were measured: (A) the shortest distance between the posterosuperior aspect of C1 posterior arch and VA; (B) distance between the outer aspect of VAG and VA; (C) distance between midpoint of VAG and VA; and (D) distance between the inner aspect of the VAG and VA. Then, the central axis of trajectory perpendicular to the coronal plane (axis P) and the central axis of trajectory with a medial inclination (axis M) were designed for the basis of measurements. Parameters related to the relationship between axis P/M and VA V3 segment were measured respectively: (E, E'), distance between insertion point and anterior aspect of VA along axis P/M; (F, F'), the shortest distance between axis P/M and the outer cortex of C1 transverse foramen; and (G, G'), the narrowest width of C1 internal medullary canal along axis P/M.

RESULT

A, B, C, and D were 1.7±1.0 mm, 1.6±0.9 mm, 1.5±0.7 mm, 2.3±1.1 mm, respectively. E, E' were 5.5±1.7 mm and 4.1±2.3 mm. F, F' were 1.9±0.7 mm and 2.9±0.7 mm. G, G' were 3.7±1.4 mm and 4.8±1.2 mm. There was a little interspace between atlas VAG and VA, which was mainly filled with venous plexus.

CONCLUSIONS

There is a close relationship between C1 transpedicular screw trajectory and VA V3 segment. Trajectory with medial inclination technique is suggested especially for female patients.

The Impact of Engorged Vein within Traumatic Posterior Neck Muscle Identified in Preoperative Computed Tomography Angiography to Estimated Blood Loss during Posterior Upper Cervical Spine Surgery

Objective

Injuries of upper cervical spine are potentially fatal. Thus, appropriate diagnosis and treatment is essential. In our institute, preoperative computed tomography angiography (CTA) has been performed for evaluation of injuries of bony and vascular structure. The authors confirmed the engorged venous plexus within injured posterior neck muscle. We have this research to clarify the relationship between the engorged venous plexus and engorged vein.

Methods

A retrospective review identified 23 adult patients who underwent 23 posterior cervical spine surgeries for treatment of upper cervical injury between 2013 and 2015. Preoperative CTA was used to identify of venous engorgement within posterior neck muscle. The male to female ratio was 18:5 and the mean age was 53.5 years (range, 25-78 years). Presence of venous engorgement and estimated blood loss (EBL) were analyzed retrospectively.

Results

The EBL of group with venous engorgement was 454.55 mL. The EBL of group without venous engorgement was 291.67 mL. The EBL of group with venous engorgement was larger than control group in significant.

Conclusion

The presence of engorged venous plexus is important factor of intraoperative bleeding. Preoperative CTA for identifying of presence of engorged venous plexus and fine operative techniques is important to decrease of blood loss during posterior cervical spine surgery.

A case study of occipital outgrowth: a rare suboccipital abnormality

PURPOSE

To describe the clinical and radiological characteristics of uncommon upper cervical spine abnormality in children.

METHODS

Clinical and diagnostic characteristics of three patients aged 6-12 years with a similar uncommon type of occipital anomaly are described. The patients were admitted in 2007, 2009, and 2014, respectively.

RESULTS

All patients were clinically and radiologically examined. In each case the massive, additional unilateral outgrowth of the occipital bone (os occipitale) was visualized. The signs and symptoms included torticollis, acute brain ischemia, and limited head motion. Two of the three patients underwent surgical treatment: an occipital-cervical fusion was performed in the first patient, and the outgrowth was removed in the second patient. After 1 year of follow-up the results were estimated as good for both patients, with better functional outcome for the second patient. The parents of the third patient did not consent for the surgical treatment.

CONCLUSIONS

The unique features of this abnormality distinguish it from previous descriptions of the manifestation of pro-atlas, atlas, or atlanto-occipital synostosis. The presented abnormality had different manifestation of various severity in each case, from torticollis to acute vascular disorder.

STUDY DESIGN

Clinical case series.

LEVEL OF EVIDENCE

IV.

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.

Anatomical study of suboccipital vertebral arteries and surrounding bony structures using virtual reality technology

Background

This work aimed to evaluate the efficacy of virtual reality (VR) technology in neurosurgical anatomy through a comparison of the virtual 3D microanatomy of the suboccipital vertebral arteries and their bony structures as part of the resection of tumors in the craniovertebral junction (CVJ) of 20 patients compared to the actual microanatomy of the vertebral arteries of 15 cadaveric headsets.

Material/Methods

The study was conducted with 2 groups of data: a VR group composed of 20 clinical cases and a physical body group (PB group) composed of 15 cadaveric headsets. In the VR group, the dissection and measurements of the vertebral arteries were simulated on a Dextroscope. In the PB group, the vertebral arteries in the cadaver heads were examined under a microscope and anatomical measurements of VA and bony structures were performed. The length and course of the vertebral arteries and its surrounding bony structures in each group were compared.

Results

The distances from the inferior part of the transverse process foramen (TPF) of C1 to the inferior part of TPF of C2 were 17.68±2.86 mm and 18.4±1.82 mm in the PB and VR groups, respectively. The distances between the middle point of the posterior arch of the atlas and the medial intersection of VA on the groove were 17.35±2.23 mm in the PB group and 18.13±2.58 mm in the VR group. The distances between the middle line and the entrance of VA to the lower rim of TPF of Atlas were 28.64±2.67 mm in PB group and 29.23±2.89 mm in VR group. The diameters of the vertebral artery (VA) at the end of the groove and foramen of C2 transverse process were 4.02±046 mm and 4.25±0.51 mm, respectively, in the PB group and 3.54±0.44 mm and 4.47±0.62 mm, respectively, in VR group. The distances between the VA lumen center and midline of the foramen magnum at the level of dural penetration was 10.4±1.13 mm in the PB group and 11.5±1.34 mm in the VR group (P>0.05).

Conclusions

VR technology can accurately simulate the anatomical features of the suboccipital vertebral arteries and their bony structures, which facilitates the planning of individual surgeries in the CVJ.

Three-Dimensional CT Imaging with Volume Rending of Separating Fusing, Opacifying and False-Coloring Technique

This paper proposes a three-dimensional CT imaging (3DCT) method to show the anatomical structures. With the CT volume scanning data, 3DCT imaging with volume rendering of separating, fusing, opacifying and false-coloring (SFOF-VR) techniques was done on the workstation. SFOF-VR, with separately and jointly showing the complicated anatomy and their spatial relations, is valuable in finding the variations of bone, artery and vein, and diagnosing their diseases. When comparing with routine volume rendering (R-VR), SFOF-VR provides more clear and direct anatomical basis for imaging diagnosis and surgical operation.

Computerized tomographic morphometric analysis of the cervical spine

Background:

Detailed knowledge of cervical canal and transverse foramens’ morphometry is critical for understanding the pathology of certain diseases and for proper preoperative planning. Lateral x-rays do not provide the necessary accuracy. A retrospective morphometric study of the cervical canal was performed at the authors’ institution to measure mean dimensions of sagittal canal diameter (SCD), right and left transverse foramens’ sagittal (SFD) and transverse (TFD) diameters and minimum distance between spinal canal and transverse foramens (dSC-TF) for each level of the cervical spine from C1-C7, using computerized tomographic scans, in 100 patients from the archives of the Emergency Room.

Results:

Significant differences for SCD were detected between C1 and the other levels of the cervical spine for both male and female patients. For the transverse foramen, significant differences in sagittal diameters were detected at C3, C4, C5 levels. For transverse diameters, significant differences at C3 and C4 levels. A significant difference of the distance between the transverse spinal foramen and the cervical canal was measured between left and right side at the level of C3. This difference was equally observed to male and female subjects.

Conclusion:

CT scan can replace older conventional radiography techniques by providing more accurate measurements on anatomical elements of the cervical spine that could facilitate diagnosis and preoperative planning, thus avoiding possible trauma to the vertebral arteries during tissue dissection and instrument application.

Biomechanical comparison of occiput-C1-C2 fixation techniques: C0-C1 transarticular screw and direct occiput condyle screw

STUDY DESIGN

In vitro human cadaveric biomechanical study.

OBJECTIVE

The objective was to evaluate and compare the construct stability of occiput-C1-C2 fixation provided by C0-C1 transarticular screws or occipital condyle screws.

SUMMARY OF BACKGROUND DATA

The placement of an occipital plate is commonly recommended in occipitocervical fixation surgery. However, there are unique clinical situations in which the placement of the occipital plate may not be possible or may have already failed. For these situations, 2 novel techniques that use the occipital condyle have been recently introduced: (1) C0-C1 transarticular screws fixation and (2) direct occipital condyle screws and C1 lateral mass screws fixation. However, there is a lack of thorough biomechanics studies of these techniques.

METHODS

Nondestructive kinematic tests and destructive tests were conducted in 16 fresh frozen cadaveric spines. As a nondestructive kinematic test, a pure moment of up to 2.0 N·m was applied in smooth continuous flexion/extension, lateral bending, and axial rotation motions. In addition to an intact-state case, a total of 5 different constructs (standard occipital plate, C0-C1 transarticular screws with/without occipital plate, and occipital condyle screws with/without occipital plate) were tested after destabilization of C0-C1 and C1-C2. All constructs had C2 pedicle screws fixation, and occipital condyle screws were incorporated with C1 lateral screws.

RESULTS

All fixation techniques significantly reduced ranges of motion compared with the intact state. In comparison with the standard occipital plate construct, the 2 novel techniques showed higher stability in axial rotation and lower stability in lateral bending. In both nondestructive and destructive tests, there were no statistical differences between C0-C1 transarticular screw construct and occipital condyle screw construct.

CONCLUSION

The C0-C1 transarticular screw technique and direct occipital condyle screw with C1 lateral mass screw technique can be salvage fixation methods when occipital plate fixation is not feasible.