Anterior Transarticular Screw Research Articles

Anterior Transarticular Crossing Screw Fixation for Atlantoaxial Joint Instability: A Biomechanical Study.

To evaluate the biomechanical stability of anterior transarticular crossing screw (ATCS) and compare it with anterior transarticular screw (ATS) which may provide basic evidence for clinical application. Eight human fresh cadaveric specimens (occiput-C4) were tested with 5 conditions including the intact status, the injury status (type II odontoid fracture), the injury+ATS fixation status (traditional bilateral ATS fixation); the injury+unilateral ATCS fixation status; and the injury+bilateral ATCS fixation status. Specimens were applied to a pure moment of 1.5 Nm in flexion-extension, lateral bending, and axial rotation, respectively. The range of motions (ROMs) and the neutral zones (NZs) of C1 to C2 segment were calculated and compared between 5 status. ATS and ATCS fixations significantly reduced the motions in all directions when compared with the intact and injury statues (p < 0.05). In flexion-extension, the ROMs of ATS, unilateral ATCS, and bilateral ATCS were 4.7° ± 2.5°, 4.1° ± 1.9°, and 3.2° ± 1.2°, respectively. Bilateral ATCS resulted in a significant decrease in ROM in flexion-extension when compared with ATS and unilateral ATCS (p = 0.035 and p = 0.023). In lateral bending and axial rotation, there was no significant difference in ROM between the 3 fixations (p > 0.05). Three fixations resulted in similar NZs in all directions (p > 0.05). ATCS is a biomechanically effective alternative or supplemental method for atlantoaxial instability.

Biomechanical properties of different anterior and posterior techniques for atlantoaxial fixation: a finite element analysis

BackgroundMany techniques for atlantoaxial fixation have been developed. However, the biomechanical differences among various atlantoaxial fixation methods remain unclear. This study aimed to evaluate the biomechanical influence of anterior and posterior atlantoaxial fixation techniques on fixed and nonfixed segments.MethodsAn occiput-C7 cervical finite element model was used to construct 6 surgical models including a Harms plate, a transoral atlantoaxial reduction plate (TARP), an anterior transarticular screw (ATS), a Magerl screw, a posterior screw-plate, and a screw-rod system. Range of motion (ROM), facet joint force (FJF), disc stress, screw stress, and bone-screw interface stress were calculated.ResultsThe C1/2 ROMs were relatively small in the ATS and Magerl screw models under all loading directions except for extension (0.1°–1.0°). The posterior screw-plate system and screw-rod system generated greater stresses on the screws (77.6–1018.1 MPa) and bone-screw interfaces (58.3–499.0 MPa). The Harms plate and TARP models had relatively small ROMs (3.2°–17.6°), disc stress (1.3–7.6 MPa), and FJF (3.3–106.8 N) at the nonfixed segments. Changes in disc stress and FJF of the cervical segments were not consistent with changes in ROM.ConclusionsATS and Magerl screws may provide good atlantoaxial stability. The posterior screw-rod system and screw-plate system may have higher risks of screw loosening and breakage. The Harms plate and TARP model may more effectively relieve nonfixed segment degeneration than other techniques. The C0/1 or C2/3 segment may not be more susceptible to degeneration than other nonfixed segments after C1/2 fixation.

Anterior atlanto-occipital transarticular screw fixation: a biomechanical comparison with posterior fixation techniques.

Atlanto-occipital instability is commonly treated with posterior fixation. However, in patients with congenital or acquired factors, posterior fixation may not be possible. For these situations, a novel anterior atlanto-occipital transarticular screw (AATS) fixation technique has been introduced recently. However, biomechanical study of this technique is lacking. This study was designed to evaluate the biomechanical stability of AATS fixation for the atlanto-occipital joint and compare it with conventional posterior occipitocervical fixation (POCF). Six cadaveric specimens (occiput-C4) were tested in four conditions, including intact, injury, injury + AATS, and injury + POCF states. A pure moment of 1.5 Nm was applied to specimens in flexion, extension, lateral bending, and axial rotation. The range of motion (ROM) and neutral zone (NZ) were calculated and compared from the occiput to C1. The AATS fixation constrained ROMs to 0.4° in flexion (p < 0.001), 0.4° in extension (p < 0.001), 1.0° in lateral bending (p < 0.001), and 0.7° in axial rotation (p < 0.001) when compared with the injury state. In all directions, there was no statistically significant difference observed in ROMs and NZs between AATS fixation and POCF (p > 0.05). This study identified that the novel AATS fixation, as stand-alone anterior fixation, was equivalent to POCF in all directions. The results suggest that anterior transarticular screw fixation is a biomechanically effective salvage technique for posterior atlanto-occipital fixation, and may also serve as supplemental fixation.

Atlantoaxial Anterior Transarticular Screw Fixation: Indications and Surgical Technique.

Posterior atlantoaxial screw fixation is a widely adopted therapeutic option for C1-C2 instability secondary to fractures or dislocation, degenerative diseases, or tumors at this level. Anterior transarticular screw fixation (ATSF) is an effective alternative to the posterior approaches, presenting several advantages despite being scarcely known and rarely chosen.In this chapter, we describe the ATSF step by step, illustrating its variations reported in literature, and we critically analyze the several advantages and contraindications of this technique. Moreover, we provide a list of tips and tricks on the surgical procedure, including critical operating room settings-the result of more than 10years of experience in the field by a senior author.ATSF is a valid strategy for the treatment of different diseases occurring at the level of the atlantoaxial complex that needs consideration. Given the significant learning curve of this strategy, some hints may be essential to begin introducing this technique in the personal armamentarium of a spine surgeon so that they can perform ATSF safely and effectively.

Referencing for anterior atlantoaxial trans-articular osteosynthesis: a radiological study and proposal of a decisional algorithm.

Anterior trans-articular C1-C2 screw placement can be considered as a surgical alternative in different conditions affecting the atlantoaxial region. While its rigidity is similar to posterior Magerl and Harms techniques, it also provides some surgical advantages. However, the literature lacks papers exhaustively describing indication criteria, surgical steps, and pitfalls. This is a radiological study on 100 healthy subjects. Thin-layer CT scans of the craniovertebral junction were retrieved from the institutional database. The coronal inclination of the C1-C2 joint rim and the depth of the entry point of the screw with respect to the anterior profile of C2 were measured. The antero-posterior and the medio-lateral surgical corridors for the screw placement, and the wideness of the target area on the upper surface of C1 were also measured. The multivariate analysis showed that the coronal inclination of the C1-C2 articular joint rim strongly influences the surface extension of the C1 target area; the depth of the entry point and the C1-C2 articular rim inclination seem to be independent factors in influencing both the medio-lateral and the antero-posterior surgical corridors wideness. A decisional algorithm on whether to perform an anterior or posterior approach to the atlantoaxial region was also proposed. We can conclude that, as much as the C1-C2 articular rim is tending to the horizontal line, and as deeper is the entry point of the screw on the anterior profile of C2, as easier the anterior C1-C2 trans-articular screw placement will result.

A Clinical Study to Assess the Efficacy of Anterior Transarticular C1-C2 Screw Fixation for Stabilization of AtlantoAxial Instability

Introduction: The upper cervical spine includes the atlas (C1) and Axis (C2). The anatomy of upper twovertebrae is unique from each other. Atlanto-axial articulation is the most unique, mobile segment of spine,which largely depends on ligamentous supports based on integrity of odontoid for its stability. Historically,atlanto-axial subluxation was treated by reduction and fusion of C1-C2 joint. However, High riding vertebralartery precludes the placement of posterior trans-articular screw, which is liable to injury during screwplacement. Socomputed tomography scans can be used to evaluate the risk of “high riding” vertebral arteryduring the management of atlanto-axial subluxation. Hence, anterior trans-articular screw fixation techniqueavoids the course of high riding vertebral artery.Material and Method: Nine patients underwent NCCT cervical spine with 3-D reconstruction and clinicalevaluation of pain was done by recording the VAS score done pre operatively and after surgery.Results: All surgical cohorts underwent anterior C1-C2 fixation with an average follow up for 24 months.All patients were assessed as per fixed protocol of our local hospital guidelines of orthopaedics department.Pain score was clinically evaluated by VAS score before and after surgery yielding 90% excellent result.Conclusion: Anterior Trans-articular C1-C2 screw fixation isa minimally invasive technique with less bloodloss, shorter skins car and faster post-operative recovery. It is an appropriate technique for stabilization ofAtlanto-Axial instabilities.

Design a novel integrated screw for minimally invasive atlantoaxial anterior transarticular screw fixation: a finite element analysis

PurposeTo design a new type of screw for minimally invasive atlantoaxial anterior transarticular screw (AATS) fixation with a diameter that is significantly thicker than that of traditional screws, threaded structures at both ends, and a porous metal structure in the middle. The use of a porous metal structure can effectively promote bone fusion and compensate for the disadvantages of traditional AATSs in terms of insufficient fixation strength and difficulty of bone fusion. The biomechanical stability of this screw was verified through finite element analysis. This instrument may provide a new surgical option for the treatment of atlantoaxial disorders.MethodsAccording to the surgical procedure, the new type of AATS was placed in a three-dimensional atlantoaxial model to determine the setting of relevant parameters such as the diameter, length, and thread to porous metal ratio of the structure. According to the results of measurement, the feasibility and safety of the new AATS were verified, and a representative finite element model of the upper cervical vertebrae was chosen to establish, and the validity of the model was verified. Then, finite element-based biomechanical analysis was performed using three models, i.e., atlantoaxial posterior pedicle screw fixation, traditional atlantoaxial AATS fixation, and atlantoaxial AATS fixation with the new type of screw, and the biomechanical effectiveness of the novel AATS was verified.ResultsBy measuring the atlantoaxial parameters, the atlantoaxial CT data of the representative 30-year-old normal adult male were selected to create a personalized 3D printing AATS screw. In this case, the design parameters of the new screw were determined as follows: diameter, 6 mm; length of the head thread structure, 10 mm; length of the middle porous metal structure, 8 mm (a middle porous structure containing an annular cylinder ); length of the tail thread structure, 8 mm; and total length, 26 mm. Applying the same load conditions to the atlantoaxial complex along different directions in the established finite element models of the three types of atlantoaxial fusion modes, the immediate stability of the new AATS is similar with Atlantoaxial posterior pedicle screw fixation.They are both superior to traditional atlantoaxial anterior screw fixation.The maximum local stress on the screw head in the atlantoaxial anterior surgery was less than those of traditional atlantoaxial anterior surgery.ConclusionsBy measuring relevant atlantoaxial data, we found that screws with a larger diameter can be used in AATS surgery, and the new AATS can make full use of the atlantoaxial lateral mass space and increase the stability of fixation. The finite element analysis and verification revealed that the biomechanical stability of the new AATS was superior to the AATS used in traditional atlantoaxial AATS fixation. The porous metal structure of the new AATS may promote fusion between atlantoaxial joints and allow more effective bone fusion in the minimally invasive anterior approach surgery.

The Anterior Transarticular Fixation of C1/C2 in the Elderly With Dens Fractures.

Anterior transarticular screw fixation (ATSF) of C1/C2 can be used for the treatment of unstable dens fractures. Here, we evaluated the feasibility of an anterior C1/C2 fixation in elderly patients with unstable dens fractures. Furthermore, we tried to analyze safe entry zones for ATSF surgery. A consecutive cohort of 13 patients with unstable dens fractures were treated with ATSF of C1/C2 between January 2015 and October 2016. If necessary, an additional screw was placed into the odontoid process. The placement was radiographically analyzed using the 3D Arcadis Orbic (Siemens, Erlangen, Germany). Additionally, computed tomography scans of the cervical spine from 50 trauma patients were analyzed to evaluate safe entry zones for anterior odontoid screw fixation and for ATSF. ATSF was performed in 13 cases (7 female, 6 male; mean age 81.80 years). One screw had to be corrected intraoperatively due to initial malplacement. Neurological deficits or an injury of the vertebral artery were not observed. All patients suffered from swallowing difficulties during the postoperative course, without lesions of the esophagus or the trachea. In 4 patients (30.8%), an additional posterior fixation was offered to the patients due to progressive loosening of the screws.The anatomical-radiographic analyzes revealed a significantly shallower angle of trajectory for anterior odontoid screw fixation (24.9° ± 5.85°) than for ATSF (39.1° ± 6.44° (left); 40.5° ± 6.79° (right) P = 0.02). The ATSF of C1/C2 might be a valuable option in the treatment of instable C1/C2 fractures, especially in the elderly or in patients with short necks and/or high body mass index due to the steeper trajectory compared with odontoid screw placement. Yet available screws seem to be of inferior resistance compared with the biomechanical properties of a dorsal fixation. Further studies should focus on screws with better mechanical properties and probably additional cement augmentation. 4.

Anatomic Considerations of Anterior Transarticular Screw Fixation for Atlantoaxial Instability.

Study DesignCadaveric, observational study.PurposeAtlantoaxial instability (AAI) is characterized by excessive movement at the C1–C2 junction between the atlas and axis. An anterior surgical approach to expose the upper cervical spine for internal fixation and bone grafting has been developed to fix AAI. Currently, no anatomic information exists on the anterior transarticular atlantoaxial screw or screw and plate fixation between C1 and C2 in the Indian population. The objective of this study is to assess the anatomic landmarks of C1–C2 vertebrae: entry point, trajectory, screw length, and safety of the procedure.Overview of LiteratureMethods outlined by Magerl and Harms are the optimal approaches among the dorsal techniques. Contraindications for these techniques include aberrant location of vertebral arteries, fractures of C1–C2 posterior structures. In these cases, anterior transarticular fixation is an alternative. Several available screw insertion trajectories have been reported. Biomechanical studies have demonstrated that adequate rigidity of this fixation is comparable with posterior fusion techniques.MethodsDirect measurements using Vernier calipers and a goniometer were recorded from 30 embalmed human cadavers. The primary parameters measured were the minimum and maximum lateral and posterior angulations of the screw in the sagittal and coronal planes, respectively, and optimum screw length, if it was placed accurately.Results The posterior and lateral angles of screw placement in the coronal and sagittal planes ranged from 16° to 30° (mean±standard deviation [SD], 23.93°±3.93°) and 8° to 17° (mean±SD, 13.3°±2.26°), respectively. The optimum screw length was 25–38 mm (mean±SD, 28.76±3.69 mm).ConclusionsIf the screw was inserted without lateral angulation, the spinal canal or cord could be violated. If a longer screw was inserted with greater posterior angulation, the vertebral artery at the posterior or posterolateral aspect of the C1 superior facet could be violated. Thus, 26° and 30° of lateral and posterior angulations, respectively, are the maximum angles permissible to avoid injury of the vertebral artery and violations of the spinal canal or atlanto-occipital joint.

Stent augmentation of an anterior odontoid screw for type 2 odontoid fracture-dislocation in the elderly population: Report of two cases and literature review

The fixation of type 2 odontoid fractures poses significant challenges in the elderly population due to coexistent osteoporosis and communition resulting in a high failure rate with conventional anterior screw fixation. Two elderly patients with unstable odontoid peg fractures and coexistent osteoporosis were treated with stentoplasty and anterior odontoid screw fixation. Additional anterior transarticular C1–2 screws were placed to address C1–2 instability. Both patients made an uneventful clinical recovery. One of the anterior C1–2 screws loosened due to the poor purchase in the osteoporotic bone in one patient. This did not affect the final outcome, and both the patients demonstrated maintained reduction and good alignment of odontoid peg after 2 years of follow-up. There was no intraoperative cement leak, pseudoarthrosis, or loss of reduction. Stentoplasty coupled with the anterior odontoid screw is a safe technique that can provide a biomechanically sound fixation of type 2 odontoid fractures in the presence of osteoporosis and significant communition.

334 Anterior Screw Plate Fixation for Odontoid Fractures

Abstract INTRODUCTION Certain unstable odontoid fractures (anterior oblique fracture, displaced distal fragment, disrupted alar ligament) are usually offered posterior C1-C2 fixation by Goel-Harms technique. Anterior submandibular extrapharyangeal approach offers a simple safe and biomechanically correct option to treat these fractures. Fracture manipulation, reduction and repositioning is feasible along with fixation in compression mode with a VSP plate and screws. Additional instability of the atlantoaxial joints, if present, can be treated with anterior transarticular screws. METHODS The right sided submandibular extrapharyangeal approach was used to expose the fractured odontoid. Open manipulation to reduce displaced fracture fragments followed by fixation with a VSP plate (Titanium customized from Jayon Inc Pallakad India) using 3.5 mm thick titanium screws. If fracture was associated with disruption of alar ligament then additional bilateral tranarticular screws were passed to fix the joints in neutral position after abrading the opposing endplates and corticocancellous bone grafts into the joints. RESULTS &gt;Since February 2011 January 2017 45 patients with unstable odontoid fractures have been offered this procedure. No transfusion was required in any case and no case required additional procedure. All patients showed bone union across fracture site at 3 months. Five elderly patients (70 yrs and 76 yrs) complained of dysphagia for 2–3 days after surgery, 4 patients (including the ones with dysphagia) had mild hypoglossal weakness which recovered in a week. Neck pain persisted in 9 patients for 4 weeks which responded to analgesics. Long-term follow-up imaging has been at 3 years in 8 patients, without implant failure and 100% bone fusion. CONCLUSION Anterior submandibular extrapharyangeal approach offers a simple safe and biomechanically correct option to treat these fractures.

Anterior retropharyngeal plate screw fixation with bilateral anterior transarticular screws for odontoid fractures ... a new comprehensive technique

Introduction: A certain group of odontoid fractures (Anderson and D’ Alonzo Type-2) are usually offered surgical treatment. Common surgical option is an anterior odontoid screw. Some of the fractures are not suitable for anterior odontoid screw (anterior oblique, displaced distal fragments and those with atlantoaxial instability) and these are usually offered posterior transarticular screws (Magerl’s) or posterior atlantoaxial screw rod/plate fixation (Goel-Harms technique). Posterior surgery involves atlantoaxial fixation with an indirect attempt to reduce and fuse the fracture . Posterior surgery has a risk of injury to the vertebral arteries, hemorrhage from the paravertebral venous plexus and the C2 root ganglion.Methods: A direct anterior submandibular retropharyangeal approach with open reduction and fixation (ORIF) using a customized variable screw placement (VSP) plate was used to realign and fix the fracture fragments in compression mode under direct vision. Twenty patients of type-II odontoid fractures (unsuitable for anterior odontoid screw) underwent an anterior retropharyngeal approach with anterior variable screw position (VSP) plate and screw fixation and eight amongst them, who had associated atlantoaxial instability underwent additional bilateral anterior transarticular screws.Results: All patients treated by this technique had 100% fracture site bone union without any implant failure. Longest follow-up has been for 3 years.Conclusion: Anterior retropharyangeal approach allows direct fracture fragment realignment under vision with an opportunity to fix in compression mode using the VSP plate, which ensures early fusion across the type-II odontoid fracture. Any associated instability can be treated by additional bilateral anterior transarticular screws. The approach is simple and safe without any risk to the vertebral arteries and biomechanically appealing.

Ošetření zlomeniny zubu čepovce u starších pacientů metodou kompresní osteosyntézy a přední transartikulární stabilizací

Ošetření zlomeniny zubu čepovce u starších pacientů metodou kompresní osteosyntézy a přední transartikulární stabilizací

A Method to Prevent Occipitocervical Joint Violation Using Plain Radiography During Percutaneous Anterior Transarticular Screw Fixation.

A prospective study of anterior transarticular screw (ATS) fixation patients. To develop a method to determine screw tip position through plain radiography after percutaneous ATS fixation to prevent occipitocervical joint (OCJ) violation. No studies using plain radiography to prevent OCJ violation during percutaneous ATS fixation have been performed. In total, 34 subjects (with 68 screws) who had undergone percutaneous ATS fixation were enrolled. To evaluate the screw tip location in relation to the C1 lateral mass (LM), the screw tip positions were graded 1, 2, or 3 on anteroposterior (AP) radiographs, and I, II, or III on lateral radiographs. OCJ violation was analyzed by postoperative computed tomography (CT). Screws with tips located lower (tip I) in the LM did not result in OCJ violation. Only one tip in the tip 3 position showed OCJ perforation, and this screw was also located in tip III. Screw perforation rates of tip 1-tip II, tip 1-tip III, and tip 2-tip III were the highest (100%), followed by tip 2-tip II (10.5%) and tip3-tip III (10%). This study provides insights into OCJ violation during percutaneous ATS fixation. According to AP radiography, a percutaneous ATS with the screw tip located in the lateral part of the LM resulted in a lower rate of OCJ perforation, whereas screws located in the medial LM resulted in the highest rate of perforation. Percutaneous ATS with the screw tip located in the neutral part of the LM should ensure that the screw tip is below the upper part of the LM, preventing OCJ violation. These findings may help surgeons assess screw positioning both during and after the operation. 3.

A novel computed method to reconstruct the bilateral digital interarticular channel of atlas and its use on the anterior upper cervical screw fixation.

Purpose. To investigate a novel computed method to reconstruct the bilateral digital interarticular channel of atlas and its potential use on the anterior upper cervical screw fixation.Methods. We have used the reverse engineering software (image-processing software and computer-aided design software) to create the approximate and optimal digital interarticular channel of atlas for 60 participants. Angles of channels, diameters of inscribed circles, long and short axes of ellipses were measured and recorded, and gender-specific analysis was also performed.Results. The channels provided sufficient space for one or two screws, and the parameters of channels are described. While the channels of females were smaller than that of males, no significant difference of angles between males and females were observed.Conclusion. Our study demonstrates the radiological features of approximate digital interarticular channels, optimal digital interarticular channels of atlas, and provides the reference trajectory of anterior transarticular screws and anterior occiput-to-axis screws. Additionally, we provide a protocol that can help make a pre-operative plan for accurate placement of anterior transarticular screws and anterior occiput-to-axis screws.

Biomechanical study of the atlantoaxial joint after artificial atlanto-odontoid joint arthroplasty

ObjectiveTo investigate the stability and three-dimensional movements of the atlantoaxial joint after artificial atlanto-odontoid joint (AAOJ) arthroplasty by comparing with a conventional method. MethodsAfter anterior decompression, 24 human cadaveric spinal specimens of C0-C3 were randomly divided into two groups: Group A receiving artificial AAOJ arthroplasty; Group B experiencing anterior transarticular screw (ATAS) fixation. Two groups underwent flexibility test in intact and instrumented states. Rotational angle of the C0-C3 segments was measured to study the immediate stability and function of anterior decompression with AAOJ arthroplasty compared with the intact state and ATAS fixation. ResultsCompared with the intact state, anterior decompression with AAOJ arthroplasty resulted in a significant decrease in the range of motion (ROM) and neutral zone (NZ) during flexion, extension and lateral bending (P<0.05); however, with regard to axial rotation, there was no significant difference in ROM and NZ (P>0.05). Compared with anterior decompression with ATAS fixation, anterior decompression with AAOJ arthroplasty during flexion, extension and lateral bending, significant difference was found in ROM and NZ (P>0.05); however, as for axial rotation, there was a significant increase in ROM and NZ (P<0.05). ConclusionThe self-designed AAOJ has an excellent biomechanical performance, which can restore excellent instant stability and preserve the movement of the atlanto-axialjoint.

Morphometric Characteristics of C1-C2 Vertebrae to Perform Anterior Transarticular Crossing Screw Fixation.

In unique clinical situations where C1-C2 posterior fixation is not available or has previously failed, an anterior transarticular screw (ATAS) may be a viable alternative. However, there are no previous reports that investigate possible screw angles, screw entry points, and screw length based on computed tomography (CT) multiplanar reconstruction images in Turkish patients. The aim of this study was to determine the morphometric characteristics C1-C2 vertebrae in order to perform anterior transarticular crossing screw fixation. Patients who underwent a complete CT scan of the cervical spine for causes other than an investigation of cervical spine malformation or congenital anomaly between the years 2013 and 2015 were included in this study. The anterior transarticular C1-C2 screw angles, screw entry point, and screw length were measured on coronal and sagittal CT multiplanar reconstruction images. Twenty-five male and 14 female patients were included in the study. The mean maximum screw angle for ATAS was found to be 41.18°±4.49°. The minimum and maximum screw lengths were 27.46±3.39 mm and 28.46±3.60 mm, respectively. Preoperatively, performing a calculation of the possible screw angles, screw entry point, and screw length based on CT multiplanar reconstruction images for ATAS is a safe and applicable method. In cases in which ATAS fixation across the atlantoaxial joint procedure should be performed without performing a measurement, a screw angle not more than 41.18°±4.49° on the coronal plane does not damage the vertebral artery. Furthermore, using screws shorter than 28.46±3.60 mm doesn"t purchase the atlantoaxial joint.

Feasibility and trajectory study of anterior transarticular crossing screw placement for atlantoaxial joint instability: a cadaveric study and description of a novel technique.

In unique clinical situations where C1-C2 anterior transarticular screw (ATS) fixation is not available or has failed, an anterior transarticular crossing screw (ATCS) with transcorporal pathway of the screws inside the contralateral promontory of C2 may enhance the stabilization and achieve atlantoaxial arthrodesis. The present study was to describe a novel technique of ATCS fixation for atlantoaxial joint instability and its applied anatomy, and compared it with ATS fixation method. Direct measurements using digital calipers and a goniometer were conducted on 30 pairs of dried human C1 and C2 vertebrae. The ATS and ATCS with screws (Φ 4.0mm) were performed on 11 fresh cervical spine specimens. The screw lengths in the C1 and C2, and screw entry angles of the ATS and ATCS were measured, respectively. Cadaver specimens were dissected to observe the incidence of violation to the important structures surrounding the ATS andATCS fixation technique. There was enough osseous space for ATCS placement. The lateral and incline angle of the ATCS was 36.2° and 28.7°, respectively. Screw purchase in C2 of the ATCS (25.6mm) was greater than that of the ATS (11.4mm). The ATCS C1 purchase (14.8mm) was similar to the ATS C1 purchase (14.9mm). No violation to the vertebral artery groove, the spinal canal or the atlanto-occipital joint was observed after the ATCS placement. Anterior transarticular crossing screw is a feasible and viable option for atlantoaxial fixation in selected cases. This technique achieved remarkable longer screw purchase and could enhance the atlantoaxial stability.

Anterior Extrapharyngeal Fixation of the Atlanto–Axial Joints

Introduction The atlanto–axial joints can be easily exposed from a unilateral submandibular extrapharyngeal approach. Decortication and intrajoint bone grafting can be easily accomplished. Rigid anterior fixation of the joint is possible without any risk to the vertebral arteries. Materials and Methods Between April 2008 and September 2014, 95 patients, 50 male and 45 female patients, in the age group of 12 to 82 years, were offered this procedure. 55 patients had anterior transarticular screws, 40 patients had anterior screw plate fixation (AAD 63 patients, tuberculosis 20, fixed AAD with Basilar invagination 12). All patients underwent preoperative dynamic X-rays of craniovertebral junction, computerized tomography (CT scan) of C1–C2 static and dynamic study with bone window settings and 3D reconstruction, magnetic resonance imaging (MRI), and MR angiography to study the course of vertebral artery. Stevenson technique (22 patients) for exposure to reach the prevertebral space at C1–C2. Technique 1: plate and screws (C1 lateral mass and C2 body); Technique 2: anterior transarticular screws across C1–C2 joint. Results Average procedure time was 3 hours, no case required blood transfusion, reoperation occurred in seven cases; three screw malposition both ipsilateral (right sided), reoperated within 48 hours and screw repositioned correctly. One overdistraction of C1–C2 joint due to screw not piercing the C1 lateral mass and pushing the lateral mass of C1 away from C2 (because of inadequate drilling of C1 lateral mass). Reoperated on the 3rd day and lateral mass of C1 drilled correctly and the screw passed successfully. Two inadequate excisions of odontoid process had to be removed transorally after 3 weeks because of excessive backward angulation of odontoid process. One case of screw loosening that was due to incorrect plate contouring, reoperation after 3 weeks when patient had come for first postoperative follow-up. Follow-up in 75% for 24 months. Rigid fixation in 100%, mortality 0%. Conclusion Anterior extrapharyngeal approach allows for reduction of the atlanto–axial dislocation, opportunity for bone grafting of the joint, and with anterior C1 lateral mass and C2 body screw plate fixation or anterior transarticular screws, provides rigid fixation without any risk to the vertebral artery, venous plexus, or spinal cord.

Atlantoaxial anterior transarticular screw fixation: a case series and reappraisal of the technique

Background contextAtlantoaxial instability is commonly treated with C1–C2 fixation performed via posterior approaches. Although anterior transarticular screw (ATS) fixation, performed with a classic retropharyngeal approach, was described more than 10 years ago, the published literature still lacks a comprehensive analysis of the procedure and a real case series. PurposeWe report a series of patients treated with atlantoaxial ATS, describing the surgical procedure in detail and discussing advantages and disadvantages of the technique. Study designThe study design includes case series and technical report. MethodsWe prospectively enrolled 15 patients affected by atlantoaxial instability secondary to trauma, degenerative diseases, or inflammatory diseases. Anterior transarticular screw fixation was performed with anteroposterior open-mouth and lateral intraoperative radiographs. All patients were evaluated radiologically at follow-up to identify bone fusion. ResultsAnterior transarticular screw was performed successfully in 14 patients without complications. The procedure was aborted in a case of vertebral invagination, and one case required revision surgery owing to C2 articular bone fracture. Solid C1–C2 fusion was achieved in all cases (at 10- to 21-week follow-up) except in an elderly patient affected by severe osteoporosis. No complications occurred. ConclusionsAlthough the procedure is still not widely known, ATS allows the effective and safe treatment of C1–C2 instability even in patients with systemic comorbidities. It offers several advantages over posterior approaches.