Posterior Atlantoaxial Fixation Research Articles

A synovial cyst-induced vertebral artery dissection in bow hunter's stroke: illustrative case.

Bow hunter's stroke (BHS) is a rare condition characterized by occlusion of the vertebral artery (VA) due to a head rotation. BHS typically results from neck hyperrotation, often due to anatomical factors. The authors present a case of BHS in a young male patient exacerbated by os odontoideum (OD), resulting in atlantoaxial dislocation, which ultimately led to VA dissection. A man in his 20s presented with persistent dizziness and nausea and initially received a diagnosis of a brain infarction. However, imaging revealed VA dissection caused by an OD with an associated synovial cyst. Surgical intervention, specifically atlantoaxial posterior fixation, resolved the instability and allowed for natural regression of the synovial cysts, preventing further vascular events. In this case, the OD with atlantoaxial dislocation was identified as the causative factor for BHS. The coexistence of a synovial cyst was a unique finding, likely triggered by chronic irritation caused by the OD. This case emphasizes the importance of thorough cervical spinal evaluation in young patients presenting with posterior circulation stroke. https://thejns.org/doi/10.3171/CASE2487.

The New Alternative Technique Outcomes: Atlas Lateral Mass Screw and C2-3 Transfacet Screw Fixation for Complex Atlantoaxial Instability in Patients with Thin C2 Pedicle or High-Riding Vertebral Artery

The study aimed to evaluate the safety, feasibility, effect on fusion, and clinical efficacy of atlas lateral mass and C2-3 transfacet screw fixation technique, serves as an alternative method to traditional posterior atlantoaxial fixation. Patients with atlantoaxial instability who underwent atlas lateral mass and C2-3 transfacet fixation surgery were included. The duration of the surgery and the quantity of blood lost during the operation were recorded. Patients were monitored via X-ray and computed tomography scans to evaluate the degree of fusion at the 1-month and 12-month follow-up. The Neck Visual Analog Scale and Neck Disability Index were evaluated preoperatively, in the postoperative first week, and at the 12-month follow-up for clinical follow-up. A total of 8 patients with atlantoaxial instability due to odontoid fracture or Arnold- Chiari malformation accompanied by bony or vascular abnormalities were included in the study between 2017 and 2024. All 8 patients underwent successful atlas lateral mass and C2-3 transfacet screw fixation, with no neurovascular injury noted during surgery. All patients with fracture exhibited fusion at the 12-month mark, and both the Neck Visual Analog Scale and Neck Disability Index scores demonstrated significant improvement at both the 1-week and 12-month postoperative periods (P < 0.05). The atlas lateral mass and C2-3 transfacet screw fixation technique, an alternative to conventional posterior fixation, has been demonstrated to be an efficacious method for providing adequate stabilization and fusion in patients with atlantoaxial instability, even in the cases of thin C2 pedicle, high-riding vertebral artery, previous failed surgeries, or reoperation.

Posterior atlantoaxial fixation of osteoporotic odontoid fracture: biomechanical analysis of the Magerl versus harms techniques in a cadaver model

BACKGROUND CONTEXTOdontoid fractures are among the most common cervical spine fractures in the elderly and are associated with increased morbidity and mortality. Clinical evidence suggests improved survival and quality of life after operative intervention compared to nonoperative treatment. PURPOSEThis study seeks to examine the stability of an osteoporotic Type II odontoid fracture following posterior atlantoaxial fixation with either the Magerl transarticular fixation technique or the Harms C1 lateral mass screws C2 pedicle screw rod fixation. STUDY DESIGNBiomechanical cadaveric study. METHODSEighteen cadaveric specimens extending from the cephalus to C7 were used in this study. Reflective marker arrays were attached to C1 and C2 and a single marker on the dens to measure movement of each during loading with C2–C3 and occiput-C1 being allowed to move freely. A biomechanical testing protocol imparted moments in flexion-extension, axial rotation, and lateral bending while a motion capture system recorded the motions of C1, C2, and the dens. The spines were instrumented with either the Harms fixation (n=9) or Magerl fixation (n=9) techniques, and a simulated Type II odontoid fracture was created. Motions of each instrumented spine were recorded for all moments, and then again after the instrumentation was removed to model the injured, noninstrumented state. RESULTSBoth Harms and Magerl posterior C1–C2 fixation allowed for C1, C2, and the dens to move as a relative unit. Without fixation the dens motion was coupled with C1. No significant differences were found in X, Y, Z translation motion of the dens, C1 or C2 during neutral zone motions between the Magerl and Harms fixation techniques. There were no significant differences found in Euler angle motion between the two techniques in either flexion-extension, axial rotation, or lateral bending motion. CONCLUSIONSOur findings suggest that both Harms and Magerl fixation can significantly reduce dens motion in Type II odontoid fractures in an osteoporotic cadaveric bone model. CLINICAL SIGNIFICANCEBoth Harms and Magerl posterior atlantoaxial fixation techniques allowed for C1, C2, and the dens to move as a relative unit following odontoid fracture, establishing more anatomic stability to the upper cervical spine.

Unilateral Biplanar Screw-Rod Fixation Technique for the Treatment of Odontoid Fractures in Patients with Atlantoaxial Bone or Vascular Abnormalities

This study aims to introduce the Unilateral Biplanar Screw-Rod Fixation (UBSF) technique (A hybrid fixation technique: Two sets of atlantoaxial screws were placed on the same side), which serves as a salvage method for traditional posterior atlantoaxial fixation. To summarize the indications of this technique and to assess its safety, feasibility, and clinical effectiveness in the treatment of odontoid fractures. Patients with odontoid fractures were enrolled according to special criteria. Surgical duration and intraoperative blood loss were documented. Patients were followed up for a minimum of 12 months. X-ray and CT scans were conducted and reviewed at 1 day, and patients asked return for CT reviews at 3, 6, 9, and 12 months after surgery until fracture union. Recorded and compared the Neck Visual Analog Scale and Neck Disability Index pre-surgery and at one week and 12 months post-surgery. Between January 2016 to December 2022, our study enrolled 7 patients who were diagnosed with odontoid fractures accompanied by atlantoaxial bone or vascular abnormalities. All 7 patients underwent successful UBSF surgery, and no neurovascular injuries were recorded during surgery. Fracture union was observed in all patients, and the Neck VAS and NDI scores improved significantly at 1 week and 12 months postoperative (P < 0.01). The UBSF technique has been demonstrated to be safe, feasible, and effective in treating odontoid fractures. In cases where the atlantoaxial bone or vascular structure exhibits abnormalities, it can function as a supplementary or alternative approach to the conventional posterior C1-2 fixation.

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.

Research Progress on the Application of Goel Technique in Craniovertebral Junction Anomalies

Craniovertebral junction anomalies are a group of diseases characterized by the pathological changes of occipital bone,atlantoaxial bone,cerebellar tonsil,surrounding soft tissue,and nervous system,which are caused by a variety of factors.Chiari malformation is a common type of craniovertebral junction anomalies,the conventional surgical therapy of which is posterior fossa decompression.Currently,scholars represented by Goel have proposed a new theory on the classification,pathogenesis,and treatment of Chiari malformation based on posterior atlantoaxial fixation (Goel technique).This article introduces the progress in Goel technique,aiming to provide reference for the clinical work.

Innovative C-Arm-Free Navigation Technique for Posterior Spinal Fixation for Atlantoaxial Subluxation: A Technical Note.

Study design: Technical note. Objectives: To present a novel C-arm-free technique guided by navigation to insert and place a C1 lateral mass screw. Background and Objectives: Atlantoaxial subluxation (AAS) is a relatively common sequelae in patients with rheumatoid arthritis (RA) and upper cervical trauma. If they present with severe symptoms, surgical intervention such as posterior fusion is indicated. The established treatment for AAS is fixation with a C1 lateral mass screw and C2 pedicle screw (modified Goel technique) to achieve bony fusion. However, this technique requires fluoroscopy for C1 screw insertion. To avoid exposing the operating team to radiation, we present here a novel C-arm-free C1 lateral mass screw insertion technique for AAS. Materials and Methods: A 67-year-old man was referred to our hospital with neck pain, quadriparesis, and clumsiness and numbness of both upper and lower limbs. He had undergone C3-6 posterior fusion previously in another hospital. In physical examination, he had severe muscle weakness of bilateral upper limbs and hypoesthesia of all four limbs. He had hyper-reflexia of bilateral lower limbs and pollakiuria. His Japanese orthopedic score was 8 points out of 17. Preoperative radiograms showed AAS with an atlantodental interval (ADI) of 7 mm. MRI indicated retro-odontoid pseudotumor and severe spinal cord compression at the C1-2 level. The patient underwent posterior atlantoaxial fixation under navigation guidance. To prevent epidural bleeding during the insertion and placement of a C1 lateral mass screw, we have here defined a novel screw insertion technique. Results: The surgical time was clocked as 127 min and blood loss was 100 mL. There were no complications per-operatively or in the postoperative period. The patient showed almost full recovery (JOA 16/17) at two months follow-up and a solid bony fusion was noticed in the radiograms at one year follow-up. Conclusions: This novel surgical procedure and C1 lateral mas screw placement technique is a practical and safe method in recent advances of AAS treatment. Procedurally, the technique helps prevent epidural bleeding from the screw entry point and also allows for proper C1 screw insertion under navigation guidance without exposing surgeons and staff to the risk of fluoroscopic radiation.

Salvage posterior atlantoaxial fixation techniques: A retrospective study

ObjectSince the atlantoaxial region have critical neurovascular anatomy and limited bone surface for fusion, the application and choice of salvage fixation techniques are highly important. To discuss alternative posterior atlantoaxial fixation surgery techniques. MethodsWe retrospectively surgical records of 22 patients that posterior atlantoaxial fixation techniques were applied. ResultsThe patients included 11 males and 11 females (mean age: 65.7 years). The fracture type that caused instability is type 2 odontoid fractures (22). In six of these patients alternative stabilization techniques were applied due to anatomical variations, huge venous bleeding and iatrogenic trauma of the screw entry points during surgery. ConclusionsOwing to anatomical variations, intraoperative challenges, and/or instrumentation failures, performing alternative surgical fixation technique is an important factor that affects the success of stabilization of the atlantoaxial region. Knowledge of salvage techniques especially during the learning curve is vitally important. Surgeons should adapt to intraoperative surgical challenges as required.

Posterior Atlantoaxial Screw Placement in a Portuguese Population: A Morphometric Analysis Based on Computed Tomography Scan Measurements.

Objective The present study aims to evaluate the screw length and trajectory angles for posterior atlantoaxial fixation in a Portuguese population, through the study of cervical computed tomography (CT) scans. Methods Cervical CT scans of 50 adults were measured according to predefined screw trajectories of C1-C2 transarticular (C1C2TA), C1 lateral mass (C1LM), C2 pedicle (C2P), C2 pars and C2 laminar (C2L) screws. For each of these trajectories, screw length and angles were measured and compared between males and females. Results For the C1C2TA screw trajectory, the mean length, medial, and cranial angles were 34.12 ± 3.19 mm, 6.24° ± 3.06, and 59.25° ± 5.68, respectively, and for the C1LM screw trajectory, they were 27.12 ± 2.15 mm, 15.82° ± 5.07, and 13.53° ± 4.80, respectively. The mean length, medial, and cranial angles for the C2P screw trajectory were 23.44 ± 2.49 mm, 27.40° ± 4.88, and 30.41° ± 7.27, respectively; and for the C2 pars screw trajectory, they were 16.84 ± 2.08 mm, 20.09° ± 6.83, and 47.53° ± 6,97. The mean length, lateral, and cranial angles for the C2L screw trajectory were 29.10 ± 2.48 mm, 49.80° ± 4.71, and 21.56° ± 7.76, respectively. There were no gender differences except for the lengths of the C1C2TA ( p = 0,020) and C2L ( p = 0,001) screws, which were greater in males than in females. Conclusion The present study provides anatomical references for the posterior atlantoaxial fixation in a Portuguese population. These detailed data are essential to aid spine surgeons to achieve safe and effective screw placement.

Atlantoaxial posterior screw fixation using intra-operative spinal navigation with three-dimensional isocentric C-arm fluoroscopy.

Intra-operative image acquisition coupled with navigation aims to increase screw placement accuracy, and it is particularly helpful in complex spinal procedures. The aim of this study is to analyze the accuracy and reliability of posterior atlanto-axial fixation using spinal navigation combined with intra-operative 3D isocentric C-arm. We retrospectively reviewed all patients presenting with C1-C2 instability and treated by posterior atlanto-axial fixation in our center between December 2016 and September 2018. Screw positioning was guided by intra-operative navigation, registered with surface matching procedure on a previously obtained CT scan and controlled by intra-operative 3D isocentric C-arm. Age, sex, pre- and post-operative neurological status, duration of surgery, presence/absence of vertebral artery injury, and screw placement were retrospectively collected from patients' records. All patients underwent clinical and radiological follow-up at threemonths after surgery. Radiological assessment of screw positioning was performed by an independent radiologist using the Gertzbein and Robbins grading. N = 11 (7F, 4M) consecutive patients were included, with a mean age of 72years (range from 51 to 85). N = 44 navigated screws were inserted and controlled with intra-operative 3D fluoroscopy at the end of the procedure. An acceptable screw positioning (Gertzbein-Robbins grade A and B) was obtained in all cases (100%). No vertebral artery injury was observed. Mean operating time was 123minutes. At threemonths, no screw loosening or displacement was observed. In our experience, spinal navigation coupled with intra-operative 3D fluoroscopy proved to be reliable and safe for C1-C2 screw placement.

Analysis of Patients who Underwent Posterior Atlantoaxial Fixation in Our Department

Analysis of Patients who Underwent Posterior Atlantoaxial Fixation in Our Department

C1 laminoplasty and posterior atlantoaxial fusion for large retro-odontoid pseudotumor with Instability: A technical note

BackgroundRetro-odontoid pseudotumor (ROPT) is a non-neoplastic pathology of the craniovertebral junction that is usually associated with atlantoaxial instability. The mass compresses the spinal cord, causing cervical myelopathy and potentially resulting in severe disability. Posterior atlantoaxial fixation without laminectomy is a suitable surgical option when the symptoms are mild and the static compression is moderate. In the setting of patients with severe symptoms and large ROPTs, posterior decompression becomes necessary. However, achieving solid posterior atlantoaxial fusion is difficult without a bony surface, namely the C1 posterior arch. Here, we describe a novel technique of C1 laminoplasty to achieve C1 decompression, and posterior atlantoaxial fusion with a modified Goel technique. MethodsAn 83-year-old man was referred to our orthopedic department with quadriplegia due to atlantoaxial instability. His daily life had been affected by severe neck pain, clumsiness of bilateral hands, and gait disturbance for more than 2 years. Preoperative cervical radiograms revealed atlantoaxial instability, and magnetic resonance imaging showed a large pseudotumor compressing to the spinal cord. ResultsThe patient underwent C1 laminoplasty to decompress the spinal cord and retain the posterior arch as a bony surface for grafting and posterior atlantoaxial fusion. The procedure was well tolerated. The patient’s quadriparesis was improved and his Japanese Orthopedic Association score improved from 9/17 to 15/17 and his visual analog scale score for neck pain improved from 75 mm to 28 mm at the 1-year follow-up. ConclusionC1 laminoplasty and posterior atlantoaxial fusion appears useful when C1 decompression and atlantoaxial fusion become necessary.

Posterior realignment of basilar invagination with facet joint distraction technique*

Purpose We describe our experience with management of basilar invagination (BI) with the atlantoaxial dislocation (C1/C2) joint reduction technique, including posterior atlantoaxial internal fixation. Materials and methods From 2008 to 2018, eleven patients with atlantoaxial dislocation (AAD) and BI underwent surgical reduction using C1/C2 the joint reduction technique with a fibular graft/peek cage placement followed by C1 lateral mass/C2 pedicle screw fixation. In two cases that we originally planned to perform C1/C2 joint reduction, occiput-C2 pedicle screw fixation was performed instead due to intraoperative challenges. Post-operative course and surgical complications will be discussed. Results A total of 13 patients, with an average age of 30.46 ± 13.23 years (range 12–57), were operated. In one patient, iatrogenic vertebral artery injury occurred without any neurological complication. JOA score improved from 10.45 ± 1.128 to 15.0 ± 1.949 (p < 0.0001, paired t-test). All radiological indices were improved (p at least < 0.001). No construct failure was seen in any of the patients with C1-2 facet joint distraction technique during follow-up, and no additional anterior decompression surgery was required. Conclusions C1/C2 joint reduction technique with fibular graft/cervical PEEK cage of BI patients together with AAD seems to be an effective and safe surgical method of treatment.

Treatment strategy and curative effect analysis of os odontoideum complicated with atlantoaxial joint dislocation

To explore the treatment strategy and clinical efficacy for os odontoideum complicated with atlantoaxial dislocation. The clinical data of 17 patients with os odontoideum complicated with atlantoaxial dislocation surgically treated from January 2006 to January 2015 were retrospectively analyzed, including 7 males and 10 females, aged 17 to 53 (43.1±11.3) years old;course of disease was 3 to 27(10.2±6.9) months. All patients received cranial traction before operation, 12 of 14 patients with reducible dislocation were treated by posterior atlantoaxial fixation and fusion, and 2 patients with atlantooccipital deformity were treated by posterior occipitocervical fixation and fusion;3 patients with irreducible alantoaxial dislocation were treated by transoral approach decompression combined with posterior atlantoaxial fixation and fusion. The operation time, intraoperative blood loss and perioperative complications were recorded. Visual analogue scale (VAS) and Japanese Orthopaedic Association (JOA) score were used to evaluate the change of neck pain and neurological function. Atlantoaxial joint fusion rate was evaluated by CT scan. The operation time of posterior fixation and fusion ranged from 86 to 170 (92.2±27.5) min, and the intraoperative blood loss was 200-350 (250.7±65.2) ml. No vertebral artery injury and spinal cord injury were recorded. Among the patients underwent atlantoaxial fixation and fusion, 1 patient with reducible dislocation fixed by C2 laminar screw lost reduction after primary operation, and received anterior release again and finally occipitocervical fusion. All patients were followed up for 15 to 58 (32.0±12.2) months. VAS score was decreased from preoperative 4.2±0.9 to 1.3±0.7 at final follow up and the JOA score was improved from preoperative 11.2±1.2 to 16.9±0.8 at final follow-up. CT scan confirmed that the atlantoaxial or occipitocervical fusion wasgood, and the fusion time was 5 to 9 (6.7±0.6) months. Surgical treatment of os odontoideum complicated with atlantoaxial dislocation can achieve satisfactory results, improve the patient's neurological function and improve the quality of life, however the surgical options needs to be individualized.

EVALUATION OF FIXATION OF ATLANTOAXIAL SUBLUXATION USING HARMS' TECHNIQUE

Background: The placement of C1 lateral mass, C2 pedicle screw screws provide a useful alternative method to achieveatlantoaxial fixation. Aim of the work: This study aims at evaluation of Posterior Atlantoaxial fixation using Harms' technique in atlantoaxial subluxation regarding neck pain, fusion rates, neurological and radiographic outcomes.Patients and Methods: This method achieves immediate rigid stabilization of the atlantoaxial joint and obviates the need for halo vest immobilization. This technique may be used in certain cases as an alternative to occipitocervical fusion, and may also be used to increase construct stability when occipitocervical fixation is used. Results: We thus advocate that this procedure only be performed by surgeons who are highly experienced in the treatment of atlantoaxial instability, and who have an intimate understanding of the anatomy of this region. Further biomechanical analysis of this technique should be performed to quantify the strength of constructs employing C1 lateral mass, C2 pedicle screws as compared with otherfixation methods. Conclusion: Further biomechanical analysis of this technique should be performed to quantify the strength of constructs employing C1 lateral mass, C2 pedicle screws as compared with other fixation methods.

A biomechanical comparison of crossed and parallel rod configurations in atlantoaxial internal fixation.

Posterior atlantoaxial fixation with screw rod forms an approximate "II" shape or "H" increasing transverse link for better stability. In order to improve stability and in consideration of difficult placement of transverse connecting rod, possibility of inadequate bone graft, some scholars have preliminarily researched biomechanics of a novel crossed rod as an approximate "X" configuration of screw rod. The aim of this study was to evaluate and compare the biomechanics of the crossed and parallel rod configurations in the screw rod system for posterior atlantoaxial fixation on a cadaveric model. Six fresh cervical specimens were used to complete the range of motion (ROM) testing by applying pure moments of ± 2.0nm. Following intactstate and under destabilization testing, screws were implanted. The specimens were then tested in the following sequence: Group BLS + PR (C2 bilateral laminar screws + parallel rod), Group BLS + CR (C2 bilateral laminar screws + crossed rod), LPRLS + PR (C2 left pedicle screw and right laminar screw + parallel rod), LPRLS + CR (C2 left pedicle screw and right laminar screw + crossed rod), BPS + PR (C2 bilateral pedicle screws + parallel rod) and BPS + CR (C2 bilateral pedicle screws + crossed rod). The ROM of the C1-2 segments was measured in flexion-extension, lateral bending and axial rotation. Six surgical constructs were compared between the groupsand with intact condition, respectively. The six fixed modes significantly increased stability compared with both the intact and destabilization group in flexion-extension, lateral bending and axial rotation (p < .05). In extension, BPS + CR and BLS + CR showed greater stability than BLS + PR (p < .05). During flexion, the six fixation methods showed no statistical significance (p > .05). In left lateral bending, stability of the other five screw rod fixation techniques significantly increased when compared with BLS + PR (p < .05). In the right lateral bending direction, the stability of BLS + PR was worse than that of BPS + CR and BPS + PR (p < .05). In the left axial rotation, stability of BLS + CR, LPRLS + CR and BPS + CR was greater than that of BLS + PR, LPRLS + PR and BPS + PR (p < .05). In the right axial rotation, the stability of BPS + CR and BLS + CR was greater than that of BLS + PR (p < .05). The six investigated fixation methods provide sufficient biomechanical stability. The crossed rod configuration can further enhance the axial rotation stability of the screw rod system, which consists of C1 bilateral pedicle and C2 pedicle, or C2 lamina screws. The crossed rod can also improve the stability of the screw rod system made up of C1 bilateral pedicle and C2 lamina screws in lateral bending and extension. The crossed rod configuration is reliable and provides superior stability for clinical application.

Evaluation of the Accuracy of Free-hand C1 and C2 Screw Placement

Objective Posterior atlantoaxial fixation is an effective treatment for various pathologies. The anatomies of the atlas and axis are highly complex, and thus, freehand placement of C1, 2 instrumentation is technically challenging. The objective of this study was to evaluate the accuracy and safety of C1, 2 screw placement without fluoroscopic or any other guidance method by a 2-year spine surgeon. Methods A retrospective analysis of radiologic data was performed on all patients that underwent C1 or C2 instrumentation from April 2019 to January 2020; all procedures were performed by a 2-year spine surgeon. Computed tomography was used to assess cortical breaches of screw placement at C1 or C2. Severities of breaches were quantified using percentages screw diameter beyond cortical edges (0=cortical touch, 1≤25%; II=26-50%; III=51-75%; IV=76-100%). Results The surgeon placed 16 C1 screws and 20 C2 screws in 10 consecutively treated patients. For C1 screws, there were 4 breaches (25%), of which 3 were medial (18%) and 1 was anterior (7%), and for C2 screws, there were 3 total breaches (15%), of which 2 were anterior (10%) and 1 was medial (5%). Breaches were classified as grade I in 3 cases (42.8%), grade III in 1 case (14.4%), and grade IV in 3 cases (42.8%). No clinical sequelae were attributed to these breaches. Conclusion Although 25% of C1 screws and 15% of C2 screws placed using a freehand technique without guidance may be achieved accurately and safely. Preoperative morphometric evaluation and controlled exposure to this unique anatomy are essential to improve screw placement. Key Words: Accuracy of screws; Free hand technique; Malposition; Posterior atlantoaxial fixation; VA injury

Management of congenital craniovertebral anomalies: a single-centre experience of 71 cases by an algorithmic approach.

Retrospective study. Congenital craniovertebral (CV) anomalies include a wide variety of conditions involving basilar invagination (BI), atlantoaxial dislocation (AAD), bony congenital anomalies and Chiari malformation. The management of these disorders is more surgeon dependent rather than based on clear guidelines. This study aims to provide a step-by-step algorithmic approach to the management of congenital CV anomalies to achieve good CV alignment, neural recovery and long lasting stability. The study retrospectively analyses 71 patients of congenital CV anomalies treated by our algorithmic approach. Clinical assessment was done with the help of Nurick's grading pre- and post-operatively. Radiological outcome was assessed by plain radiographs, and computed tomographic scan was done at 12-month follow-up. Mean age at presentation was 17.9years (6-41years). Mean Nurick score pre-operatively was 3.8 which was reduced to 1.3 at a mean follow-up of 13.6months. Sixty-one patients had type I BI, 6 had type II BI, and 4 patients had os odontoideum. Most common symptom at presentation was weakness in limbs, neck pain and difficulty in walking. Patients of isolated AAD with os odontoideum required posterior atlantoaxial fixation and fusion only. Thirty-two patients of type I BI and 4 patients of type II BI required anterior release procedures prior to occipitocervical instrumentation. Bony fusion was achieved in 96% (68) cases with the help of autologous bone grafting. Three patients of occipitocervical fusion developed pseudoarthrosis. Our retrospective analysis demonstrates that the algorithm is effective in ensuring long lasting results in all types congenital CV anomalies.

Posterior atlantoaxial fixation with new subfacetal axis screw trajectory avoiding vertebral artery with customized variable screw placement plate and screws to enhance biomechanics of fixation.

Fixation for atlantoaxial dislocation is a challenging issue, and posterior C1 lateral mass and C2 pars–pedicle screw plate–rod construct is the standard of care for atlantoaxial instability. However, vertebral artery injury remains a potential complication. Recent literature has focused on intraoperative navigation, the O-arm, 3D printing, and recently use of robots for perfecting the trajectory and screw position to avoid disastrous injury to the vertebral artery and enhance the rigidity of fixation. These technological advances increase the costs of the surgery and are available only in select centers in the developed world.Review of the axis bone anatomy and study of the stress lines caused by weight transmission reveal that the bone below the articular surface of the superior facet is consistently dense as it lies along the line of weight transmission A new trajectory for the axis screw 3–5 mm below the midpoint of the facet joint and directed downward and medially avoids the course of the vertebral artery and holds the axis rigidly. Divergent screw constructs are biomechanically stronger. Variable screw placement (VSP) plates with long shaft screws permit manipulation of the vertebrae and realignment of the facets to the correct reduced position with fixation in the compression mode.The video can be found here: https://youtu.be/E1msiKjM-aA

Is Initial Posterior Atlantoaxial Fixation and Fusion Applying Bilateral C1-2 Transarticular Screws and C1 Laminar Hooks Reliable for Acute Pediatric Atlantoaxial Instability?: A Minimal 10-Year Analysis of Outcome and Radiological Evaluation.

A retrospective case series study with at least 10 years of follow-up data. To validate the reliability of bilateral C1-2 transarticular screws and C1 laminar hooks and a bone autograft for acute pediatric atlantoaxial instability. The reliability of initial posterior atlantoaxial fusion in pediatric patients is still controversial. To date, however, only a few published articles with short-term follow-up data are available to help spinal surgeons understand the effects of posterior atlantoaxial fusion in the skeletally immature spine. Five pediatric patients with acute atlantoaxial instability underwent atlantoaxial fusion using the above technique over a 3-year period. During a minimum 10-year follow-up period, not only outcomes and complications were investigated, but the vertical growth of the constructed spine in relation to the growth of the entire cervical spine, overall cervical spinal alignment, and adjacent-segment instability were evaluated. The clinical follow-up indicated solid fusion and complete clinical relief from symptoms. No neural or vascular impairment was observed. The radiological evaluation showed that all patients had growth within the fusion construct reaching a mean 35.4% of the entire cervical spine. There were no radiological indicators of subaxial instability, even when cervical sagittal alignments became straight with a mean C2-7 angle of 6.4°. The results showed that initial posterior atlantoaxial fusion accomplished with bilateral C1-2 transarticular screws, C1 laminar hooks fixation, and bony autograft is a reliable surgical technique for treating acute pediatric atlantoaxial instability without negative effects on vertical growth at the fused level or the stability of the subaxial spine. 3.