C2 Pedicle Screw Research Articles

Biomechanical comparison of a C1 posterior arch clamp with C1 lateral mass screws in constructs for C1-C2 fusion.

The aim of this experimental study was to assess the biomechanical performance of a novel C1 posterior arch (C1PA) clamp compared with C1 lateral mass (C1LM) screws in constructs used to treat atlantoaxial instability. These constructs had either C2 pedicle (C2P) screws or C2 translaminar (C2TL) screws. Eight fresh-frozen human cadaveric ligamentous spine specimens (C0-C3) were tested under six conditions: the intact state, the destabilized state after a simulated odontoid fracture, and when instrumented with four constructs (C1LM-C2P, C1LM-C2TL, C1PA-C2P, C1PA-C2TL). Each specimen was tested in a spinal loading simulator that separately applied axial rotation, flexion-extension and lateral bending. In each test condition, displacement controlled angular motion was applied in both directions at a speed of 2 deg/s until a resulting moment of 1.5 Nm was achieved. The measured ranges of motion (ROM) of the C1-C2 segments were compared for each test condition using nonparametric Friedman tests. The destabilized state had significantly more C1-C2 motion (p < 0.05) than the intact state in all cases, and all constructs greatly reduced this motion. C2 pedicle screw constructs that used the C1PA clamp had significantly less C1-C2 motion (p < 0.05) than those with C1LM screws in flexion-extension as well as axial rotation and no statistically significant difference was detected in lateral bending. C2 translaminar screw constructs that used the C1PA clamp had significantly less C1-C2 motion (p < 0.05) than those with C1LM screws in flexion-extension and no statistically significant difference was detected in axial rotation or in lateral bending. Data from the current study suggested that constructs using the novel C1PA clamp would provide as good, or improved, biomechanical stability to the C1-C2 segment compared with constructs using C1LM screws.

The Feasibility of C1-C2 Screw-rod Fixation in the Children 5 Years of Age and Younger.

Atlantoaxial fixation is technically challenging in younger children. The C1-C2 screw-rod fixation technique is established for adults but limited data about the clinical and radiographical outcome for the treatment of children with 5 years of age or younger is available. All files of children who were consecutively treated for spinal disorders were reviewed. Inclusion criteria for further evaluation were: 0 to 5 years of age at initial procedure; detailed surgical report of a posterior C1-C2 fusion with mass lateral and pedicle screw-rod fixation as described by Harms; a minimum clinical and radiographical follow-up of 24 months. The postoperative and last follow-up computed tomography scan and radiographs were used to assess the positioning and stability of the C1-C2 screw-rod construct. Eleven patients (3 boys) with a mean age of 46 months (range: 8 to 66 mo) fulfilled inclusion criteria and were evaluated retrospectively. The mean clinical and radiographical follow-up was 79 months (range: 24 mo to 170 mo). The diagnosis was atlantoaxial rotatory dislocation (4 cases), C1-C2 instability with subluxation (3 cases), atlantoaxial dislocation and os odontoideum (1 case), type II odontoid fracture (1 case), traumatic odontoid epiphysiolysis (1 case), and traumatic rupture of the transverse ligament with C1 subluxation (1 case). Intraoperatively and postoperatively no new neurovascular or vascular complication occurred. C1 lateral mass screws were placed correctly in all cases. Twenty-two C2 pedicle screws were placed correctly (85.7%), and 3 screws showed penetration of the pedicle wall (14.3%). No implant revision, implant failure, and pseudarthrosis were noted. Loss of correction was noted in 1 patient with unilateral C1-C2 fixation and a repeated dorsal fusion procedures were performed. A repeat procedure for implant removal and segmental release was performed in 3 patients to increase the axial rotation of the head. The C1-C2 screw-rod fixation is a safe technique that achieves solid fixation of the atlantoaxial complex in young children with various disorders. The technique preserves the joint and allows for segmental release via implant removal.

Three-dimensional anatomic analysis and navigation templates for C1 pedicle screw placement perpendicular to the coronal plane: a retrospective study

ABSTRACT Objective To explore the corridor for atlas pedicle screw placement perpendicular to the coronal plane and to develop patient-specific navigation templates for pedicle screw placement. Methods This study is a retrospective analysis. A total of 71 patients (41 males and 30 females) were involved in this study from June 2016 to June 2018, and they were divided into a template group (39 patients) and a conventional group (32 patients). The CT-based 3D reconstruction models were analyzed in the template group. From the perspective of the 3D atlas in a coronal view, the pedicle corridor was obtained. Taking the center of the tangential circle of the pedicle as the entry point, we simulated screw placement perpendicular to the coronal plane. Then, the individual navigation template was designed and used in surgery. In the conventional group, free-hand pedicle screw placement was performed perpendicular to the coronal plane. The diameter of the maximum tangential circle and screw length of the pedicle corridor were measured in the template group. The surgical time, radiation exposure time, screw grading criteria and so on were evaluated and compared between the two groups after surgery. Results ;The diameter of the maximum tangential circle and the distance between the entry point and posterior tubercle were significantly greater in males than in females. The operation was successfully completed in all patients, without aggravation of nerve injury, and the follow-up was 12-20 months, with an average of 15.6 months. A total of 78 screws were inserted in the template group, and 64 screws were inserted in the conventional group. The surgical times in the template group and conventional group were 76.47±24.44 min and 125.63±36.41 min, respectively. The radiation exposure times in the template group and conventional group were 3.51±1.77 and 10.15±4.95, respectively, and there was a significant difference between the two groups. In the template group, the deviation in the screw entry point and screw angle were 1.92±1.67 mm and 2.08±1.98°, respectively. The medial angle deviation between the left and right sides was 2.71±1.88° in the template group, which was significantly less than the deviation of 3.76±2.22° in the conventional group. Conclusion A pedicle screw trajectory perpendicular to the coronal plane can be quickly obtained based on the perspective of 3D models. The technique of screw placement perpendicular to the coronal plane assisted by navigation templates has a shorter operative time, lessintraoperative fluoroscopy and a higher safety of screw placement than traditional surgery.

Occipitocervical instrumented fixation utilising patient-specific C2 3D-printed spinal screw trajectory guides in complex paediatric skeletal dysplasia.

Instability of the craniocervical junction in paediatric patients with skeletal dysplasia poses a unique set of challenges including anatomical abnormalities, poor bone quality, skeletal immaturity and associated general anaesthetic risks. Instrumented fixation provides optimal stabilisation and fusion rates. The small vertebrae make the placement of C2 pedicle screws technically demanding with low margins of error between the spinal canal and the vertebral artery. We describe a novel clinical strategy utilising 3D-printed spinal screw trajectory guides (3D-SSTG) for individually planned C2 pedicle and laminar screws. The technique is based on a pre-operative CT scan and does not require intraoperative CT imaging. This reduces the radiation burden to the patient and forgoes the associated time and cost. The time for model generation and sterilisation was < 24h. We describe two patients (3 and 6years old) requiring occipitocervical instrumented fixation for cervical myelopathy secondary to Morquio syndrome with 3D-SSTGs. In the second case, bilateral laminar screw trajectories were also incorporated into the same guide due to the presence of high-riding vertebral arteries. Registration of the postoperative CT to the pre-operative imaging revealed that screws were optimally placed and accurately followed the predefined trajectory. To our knowledge, we present the first clinical report of 3D-printed spinal screw trajectory guides at the craniocervical junction in paediatric patients with skeletal dysplasia. The novel combination of multiple trajectories within the same guide provides the intraoperative flexibility of potential bailout options. Future studies will better define the potential of this technology to optimise personalised non-standard screw trajectories.

Bicortical Short C2 Pars Screw Fixation for High-Riding Vertebral Artery Provided Sufficient Biomechanical Stability: A Finite Element Study.

Finite element analysis. To determine and compare the biomechanical stability of the bicortical short C2 pars screw fixation for high-riding vertebral artery (HRVA) with the C2 pedicle screw and C2 translaminar screw fixation in finite element models. Fixation of C2 is technically demanding in the case of HRVA. However, there is no consensus on the alternative technique for the C2 screw fixation for HRVA in the literature. A finite element model of the upper cervical spine (C0-C2) with HRVA had been developed. C1 pedicle screw was applied at C1 by using notching technique. Bicortical short C2 pars screws, C2 pedicle screws, and C2 translaminar screws were used in each model. Then a vertical load of 50 N and a 1.5 Nm torque were applied to the C0 to simulate flexion, extension, lateral bending, and axial rotation respectively. Compared with C2 pedicle screw fixation, the bicortical short C2 pars screw fixation increased the range of motion by -1.45%, 2.13%, 62.0%, and 22.0% under flexion, extension, lateral bending, and axial rotation, respectively. However, the C2 translaminar screw fixation increased the range of motion by 43.6%, 17.8%, 423.4%, and 19.9%, respectively. In terms of the peak von Mises stress, compared with C2 pedicle screw fixation, bicortical short C2 pars screw decreased 46.1%, 41.6%, 71.3%, and -12.5% under flexion, extension, lateral bending, and axial rotation, respectively; C2 translaminar screw decreased -2.66%, -4.87%, 73.0%, and -10.1%, respectively. For a patient with HRVA, bicortical short C2 pars screw fixation provides sufficient stability and exhibited a smaller von Mises distribution on the screw-rod construct, indicating it could be an effective C2 internal fixation method for HRVA to promote C1-C2 stability and avoid the vertebral artery injury.Level of Evidence: N/A.

C1-C2 Arthrodesis With C1 Lateral Mass and C2 Parsicle Screws Combined With Interlaminar Arthrodesis and Wiring.

C1-C2 arthrodesis is a common procedure performed for the correction of atlantoaxial instability due to a host of pathologies, including degenerative, neoplastic, congenital, and trauma. While there is clinical equipoise, C1-C2 fusion is associated with a lower morbidity than occipital-cervical fusion. However, due to the unique morphometric characteristics of the C1 lateral mass, and the challenges that its fixation presents, some surgeons may elect to extend the construct to the occiput rather than attempt a C1-C2 fusion. Here, we describe our freehand technique of safely and expeditiously performing a C1-C2 fusion with C1 lateral mass and C2 "parsicle" screws. In patients with high preprocedural probability to develop pseudarthrosis, we combine our instrumented fusion with interlaminar bone graft wiring, as similarly described by Gallie. We believe the C2 "parsicle" screw avoids the technical challenges of placing a traditional C2 pedicle screw and accommodates a much larger screw length than those placed in the C2 pars. Practical surgical tips, pearls, and potential complications are discussed in detail.

Using the lamina nutrient foramen as the entry point for posterior cervical pedicle screw placement

Study designA prospective study and technique description. ObjectiveThis study introduced a method for posterior cervical pedicle screw placement by using the bilateral posterior lamina nutrient foramens as the entry point. MethodsFirstly, 30 dry C3-C7 vertebrae specimens were harvested for measurement. The lamina nutrient foramens were used as the entry points for posterior cervical pedicle screw placement and four linear and two angle parameters were obtained from a computed tomography scan(CT). Then, 60 patients who underwent C3–C7 pedicle screw fixation using this method were included, linear and angle parameters were obtained from a postoperative CT. ResultsThe average incidences of lamina nutrient foramen on the C3–C7 specimens were 88.3%, 90.0%, 95.0%, 95.0%, and 96.7%, respectively. The distances from the entry point to the pedicle screw tip (OD), the pedicle transverse angles (α), and the pedicle sagittal angles (β) measure for the entry points from C3–C7 were 28.74 ± 3.45–30.15 ± 2.01 mm, 26.88 ± 6.89° to 32.72 ± 5.91°, and 12.48 ± 9.31° to 19.71 ± 8.45°, respectively, with no significant differences between the left and right sides. In the 60 patients who underwent surgery, the lengths of the pedicle screws (PL) were 28.34 ± 2.25–30.15 ± 2.31 mm, the pedicle transverse angles (α) were 26.89 ± 6.86° to 32.36 ± 5.65°, and the pedicle sagittal angles (β) were 12.49 ± 9.11° to 20.06 ± 8.91°. The new method had a 96.8% (454/469) success rate among these patients, with no screws penetrating the spinal canal or signs of vertebral artery injury. ConclusionEntry at the bilateral lamina nutrient foramen represents an alternative posterior cervical pedicle screw placement technique that is feasible and safe.

Correlation between osteoarthritis of the atlantoaxial facet joint and a high\u2010riding vertebral artery

BackgroundA high-riding vertebral artery (HRVA) is an intraosseous anomaly that narrows the trajectory for C2 pedicle screws. The prevalence of a HRVA is high in patients who need surgery at the craniovertebral junction, but reports about HRVAs in subaxial cervical spine disorders are limited. We sought to determine the prevalence of HRVAs among patients with subaxial cervical spine disorders to elucidate the potential risk for VA injury in subaxial cervical spine surgery.MethodsWe included 215 patients, 94 were with a main lesion from C3 to C7 (subaxial group) and 121 were with a main lesion from T1 to L5 (thoracolumbar group). A HRVA was defined as a maximum C2 pedicle diameter of < 3.5 mm on axial CT. The sex, age of patients, body mass index (BMI), osteoarthritis of the atlantoaxial (C1-2) facet joints, and prevalence of a HRVA in the 2 groups were compared and logistic regression was used to identify the factors correlated with a HRVA.ResultsThe patients in the subaxial group were younger than those in the thoracolumbar group, but their sex and BMI did not differ significantly between the 2 groups. The mean osteoarthritis grade of the C1-2 facet joints of patients in the subaxial group was significantly higher than that in those in the thoracolumbar group. A HRVA was found in 26 patients of 94 (27.7 %) in the subaxial group and in 19 of 121 (15.7 %) in the thoracolumbar group. The prevalence of a HRVA in the subaxial group was significantly higher and osteoarthritis of C1-2 facet joints correlated significantly with a HRVA.ConclusionsThe prevalence of a HRVA in patients with subaxial cervical spine disorders is higher than in those without and osteoarthritis of the C1-2 facet joints is correlated with a HRVA.

Analyzing parsicle screws as a viable alternative to pars screws and pedicle screws for C2 posterior instrumentation fixation

IntroductionThis study examined the possible clinical utility of “parsicle screws” in securing C2 instrumentation. MethodsTen patients’ C2 vertebrae were virtually reconstructed using computer-aided design software. Pedicle, pars, and parsicle screws were virtually placed in the vertebrae. ResultsIn addition to establishing the trajectory and theoretical safety of parsicle screws, this study determined that parsicle screws were significantly longer than pars screws (p = 0.005). ConclusionThe additional length of parsicle screws may improve construct stability. As such, parsicle screws should be examined as an alternative to pars screws in patients unable to receive C2 pedicle screws.

Posterior fixation for paediatric and adolescent unstable hangman's fracture: evolution to C1 sparing techniques.

The aim was to study surgical outcomes in hangman's fractures in paediatric and adolescent patients and to demonstrate evolution in posterior surgery from C1-C2-C3 fusion to C1 sparing techniques. Patients (aged ≤ 18 years) operated at a tertiary level centre between September 2011 to February 2018 with more than 1 year of follow-up were included. Neurological status, type of fracture, operating time, blood loss, follow-up, and complications were assessed. Nine patients were included, with mean age mean of 16.45 years, with a mean follow-up of 42.78 months. Six patients having neurological deficit showed improvement. Two patients, one having undergone C1-C3 lateral mass screw rod fixation (LMSF) and other had C2 pedicle screw with C3 LMSF, developed kyphosis for which fixation was further extended caudally. One patient with an old hangman's fracture with reabsorbed axis pedicle underwent C2 body screw along with C3-C4 pedicle screw rod fixation and C2 pedicle reconstruction. All patients showed evidence of postoperative fusion. Hangman's fractures in young patients can be successfully managed via posterior fixation. In our centre, we have evolved in the direction of motion preservation at C1 C2 joint, along with 3 column stable fixation of the C2 pedicle. C2 pedicle reformation has allowed motion preserving surgery in complex fracture types. Extension of construct till C4 in selected cases is important to prevent postoperative kyphosis.

Prevalence of high-riding vertebral arteries and narrow C2 pedicles among Central-European population: a computed tomography-based study

High-riding vertebral artery (HRVA) and narrow C2 pedicles (C2P) pose a great risk of injuring the vessel during C2 pedicle or transarticular screw placement. Recent meta-analysis revealed a paucity of European studies regarding measurements and prevalence of these anatomical variants. Three hundred eighty-three consecutive cervical spine CT scans with 766 potential screw insertion sites were analyzed independently by two trained observers. C2 internal height (C2InH), C2 isthmus height (C2IsH), and C2P width were measured. Kappa statistics for inter- and intraobserver reliability as well as for inter-software agreement were calculated. HRVA was defined as C2IsH of ≤ 5 mm and/or C2InH of ≤ 2 mm. Narrow C2P was defined as C2P width ≤ 4 mm. STROBE checklist was followed. At least 1 HRVA was found in 25,3% (95% CI 21,1–29,8) of patients (16,7% of potential sites). At least 1 narrow C2P was seen in 36,8% (95% CI 32,1–41,7) of patients (23,8% of potential sites). Among those with HRVA, unilateral HRVA was present in 68,0% (95% CI 58,4–77,0), whereas bilateral HRVA in 32,0% (95% CI 23,0–41,6). No difference in terms of laterality (right or left) was seen neither for HRVA nor narrow C2P. Significant differences were found between females and males for all measurements. Each parameter showed either good or excellent inter- or intraobserver, and inter-software agreement coefficients. HRVA and narrow C2P are common findings in Central-European population and should be appreciated at the planning stage before craniocervical instrumentation. Measurements can be consistently reproduced by various observers at varying intervals using different software.

Evolution to Pedicle Reformation Technique in Surgical Management of Hangman's Fracture

Opinions vary regarding optimal treatment of unstable hangman's fractures. Recent technological advances have allowed short segment, motion preserving fixation, even in complex cases. The aim of the study was to demonstrate C1-C2 motion-preserving short-segment fusion in hangman's fracture and the evolution of technique from pedicle realignment to pedicle reformation in complex fractures with resorbed/destroyed C2 pedicles. This was a retrospective study. Patients operated by a single surgeon at a tertiary level center from 2012 to 2018 were included. The type of fracture, operating time, and blood loss was recorded. Neurologic deficits were recorded using the American Spinal Injury Association scale with regular clinicoradiologic follow-up. Nine patients (8 male), with a mean age of 36 ± 16.9 years were included. In the initial 7 patients, C2 pedicle screw, C3-C4 lateral mass screw, and rod fixation was done. The last 2 patients were complex neglected injuries, with 1 having severe angulation and displacement and the other having spondyloptosis with C2 body placed anterior to C4 body. In both these patients, direct C2 body screw were placed and pedicle reconstruction was done. Mean follow up was 41.4 ± 29.8 months. All 5 patients with preoperative neurologic deficits had improvement in power. C1-C2 joint motion was preserved in all. All patients had bony fusion. Preservation of motion at the C1-C2 joint should be the goal in all surgically managed hangman's fracture patients. The technique of C2 pedicle reconstruction can be utilized for the same in old neglected hangman's fractures.

C2 Pedicle Sclerosis Grading, More Than Diameter, Predicts Surgeons' Preoperative Assessment of Safe Screw Placement: A Novel Classification System

The preoperative assessment of C2 morphology is important for safe instrumentation. Sclerotic changes are often seen in C2 pedicles. Evaluating the diameter measurements solely might not accurately assess the safety of screw insertion. We have proposed a novel grading system of the C2 pedicle that includes sclerosis and evaluated the predictive value of this grading system with the surgeon's safety evaluation. We reviewed and measured the dimensional values in 220 cervical computed tomography angiograms. Additionally, we used a grading system that divides the findings into 5 grades according to the width measurement and degree of sclerosis in the C2 pedicle. Two spine surgeons independently classified the pedicles as follows: safe (minimal risk of pedicle violation), caution needed (caution to minimize pedicle violation), or dangerous (a high risk of pedicle violation). Finally, we compared the measurements and the surgeons' safety assessments. A total of 411 pedicles of 203 patients (mean age, 69.5 years; 49.5% women) were included. Of the 411 C2 pedicles, 170 were classified as high risk by ≥1 surgeon. Between the dimensional measurements and grading system, the sclerotic grade showed the best predictive value. We have introduced a novel tool to evaluate the safety of C2 pedicle screw placement. Our results suggest that our pedicle width-sclerosis grading system is reproducible and predicts the surgeon's assessment of safe screw placement better than C2 pedicle diametrical measurements alone.

C1-2 Pedicle Screw Fixation for Ponticulus Posticus and Duplication of Vertebral Artery: 2-Dimensional Operative Video

We previously introduced C1 pedicle screw placement to treat C1-2 pathology in a patient with normal vertebral artery anatomy.1 However, we should prepare to meet various anatomic variations. Ponticulus posticus is a bony prominence arising from the posterior arch or the superior articulating process of the atlas that completely or partially encircles the vertebral artery.2 We herein report a 79-yr-old female who presented with myelopathy and was diagnosed with compressive myelopathy at the C1 level in magnetic resonance imaging. A computed tomography showed ponticulus posticus (complete type to the right side) with duplication of vertebral artery. She underwent surgical treatment of C1-2 pedicle screw placement and reduction of C1 vertebra under a microscopic view. After C1 laminectomy, both-side vertebral arteries were dissected with a microscissor. The mobilization of upper divisions of vertebral artery was identified to secure the entry point and pedicle to insert a C1 pedicle screw. After complete protection of the upper and lower divisions of vertebral artery and identification of pedicle, a C1 pedicle screw was inserted by a freehand technique. We inserted autologous bone chips in the distracted C1-2 facet joint for facet joint fusion, and the C1 vertebra was pulled out by a rod reducer. After surgery, the patient's symptoms disappeared, and no vertebral artery injury was identified in postoperative 3-dimensional computed tomography angiography. Patient consent was obtained prior to performing the procedure.

Letter: C2 Pedicle Screws Combined With C1 Laminar Hooks for Reducible Atlantoaxial Dislocation: An Ideal Salvage Technique for C1-C2 Pedicle Screws.

To the Editor: We read the article by Han et al1 with great interest in which the authors describe an innovative option to salvage C1-C2 fusion using laminar hooks instead of pars screws. We take this opportunity to share a similar experience and agree that it is not always possible to place screws in C1 or C2. C1-C2 fusion using C1 lateral mass and C2 pars or pedicle screws is a safe modality for the reduction and fusion of abnormal C1-C2 alignment and instability, including cases of post-traumatic C1-C2 subluxation.2-4 We managed a case of a 4-yr-old child who suffered odontoid tip fracture with rotatory atlantoaxial dislocation (Figure 1) following a fall from a height and presenting with torticollis and quadriparesis. The patient presented to us 2 wk after the fall. A 3-dimensional (3D) computed tomography (CT) reconstruction revealed a thin C2 pars and lamina. Based on CT measurements, a high chance of cortical breach of C2 while placing 3.5-mm pars or pedicle screws was anticipated during preoperative planning. Hence, that laminar screws over C2 could be an option during surgery was kept as an alternative salvaging procedure. The subluxation reduced under traction as soon as bilateral C1-C2 joints were opened and further distracted using dissectors. Then C1-C2 joint surfaces were curetted, and bone chips from iliac crest were inserted. The placement of C2 pedicle, pars, or laminar screws is considered to be more technically demanding than C1 lateral screw placement.5 Often, it is the C2 screw placement that more commonly leads to vascular or neural injury.6 This is particularly true in the case of children in which the small dimension of C2 makes it even more difficult to place screws of diameter 3.5 mm, which is the commonly available size.FIGURE 1.: Preoperative imaging of the patient showing the odontoid fracture and atlantoaxial dislocation A in the sagittal view. In the 3D CT angiogram, the right lateral mass of C1 is not visible B from the posterior view, which is seen subluxated anteriorly in the anterior view C.C1 lateral mass screws were placed according to the technique described by Goel et al.7 Because C2 dimensions were very thin for 3.5-mm screws, laminar hooks were placed bilaterally over C2 and minirods placed between C1 lateral mass screws and C2 laminar hooks. Finally, the C1 and C2 laminae were decorticated and iliac crest graft placed to achieve posterior bony fusion as well. A repeat scan at 3 mo showed good decompression of the craniovertebral junction and cord along with the implant in Situ (Figure 2). The patient's myelopathy has improved and is now mobilized independently. Therefore, in cases in which certain factors preclude the use of C2 pars/pedicle or lamina screws, C2 laminar hooks can be a useful rescue adjunct.FIGURE 2.: Postoperative CT showing a good reduction achieved with restoration of canal space in the sagittal view A. The 3D color rendering on maximum intensity projection B shows the C1 lateral mass screws and C2 laminar hooks in Situ.Funding This study did not receive any funding or financial support. Disclosures The authors have no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article.

Treatment of a Patient with Ossification of Ligamentum Flavum of Cervical Spine and Literature Review

<i>Background</i>: The ossification of ligamentum flavum occurs frequently in the thoracic vertebra, and the incidence of ossification of cervical ligamentum flavum is relatively low. It is easy to cause misdiagnosis and mistreatment due to lack of understanding in clinical practice. <i>Object</i>: To understand the diagnosis and treatment of cervical ossification of ligamentum flavum through the treatment of one case. <i>Material</i>: A 65-year-old female patient was hospitalized due to "lumbar discomfort with numbness of both lower limbs for 1 year, and aggravation with numbness and weakness of both upper limbs for the last 3 months". Physical examination showed cervical flexion, extension and lateral flexion activities were limited, post extension limitations were obvious, limb muscle strength was grade 4, right knee tendon reflex was active, and bilateral Hoffman sign and right Babinski sign were positive. Cervical JOA score was 8 points. Magnetic resonance imaging of cervical spine showed that there were pressure objects protruding to the spinal canal between C3/4, C5/6, and C6/7 laminae. Sagittal MRI showed segmental or focal nodular space occupying and protruding into the spinal canal from the rear of the spinal canal. Cross sectional MRI showed nodular or "M" shaped occupying space. T1 weighted image was equal signal, and T2 weighted image showed low signal shadow, suggesting high-density ossification and severe spinal cord compression. The effective sagittal diameter was less than 8mm. <i>Method</i>: Hemilaminectomy was performed for a single segmental OLF of C3/4, and a total laminectomy was performed for bilateral and multi-segmental OLF of C5/6, 6/7. According to the range of intraoperative decompression, C5 and 6 posterior lateral mass screws and C7 pedicle screws were fixed. <i>Result</i>: After the operation, the patient indicated that his upper limbs were relaxed, the umbilical horizontal band disappeared, and the muscle strength of his limbs was stronger than that before the operation. She could move freely on the ground, and her holding was more flexible and powerful than before. The postoperative JOA score was 12 points. The postoperative pathological result was fibrous connective tissue and ossification. The follow-up JOA score was increased to 15 points 8 months after operation, and the improvement rate was 78%. The patient could completely take care of herself, and the treatment was satisfactory. <i>Conclusion</i>: Surgical resection of cervical olf and canal decompression is an effective method for the treatment of Cervical OLF and can achieve good clinical results.

In Reply: C2 Pedicle Screws Combined With C1 Laminar Hooks for Reducible Atlantoaxial Dislocation: An Ideal Salvage Technique for C1-C2 Pedicle Screws.

In Reply: C2 Pedicle Screws Combined With C1 Laminar Hooks for Reducible Atlantoaxial Dislocation: An Ideal Salvage Technique for C1-C2 Pedicle Screws.

Atlantoaxial osteoarthritis: a well-established entity that remains frequently overlooked

Painful atlantoaxial (C1-2) osteoarthritis (AAOA) has been described over 40 years ago. The condition may cause severe pain symptoms and disability related to the unilateral suboccipital pain and, in some cases, occipital neuralgia. One of the greatest challenges with AAOA is making the diagnosis. Diagnosis is commonly missed or delayed when headaches are treated in isolation or when pain is attributed to subaxial spondylosis. Here we present an illustrative case involving a 67-year-old male presenting with classic painful AAOA. After failing conservative treatments, he was evaluated with morphologic, radiological studies and a diagnostic injection. He was successfully treated with bilateral, navigation guided C1 lateral mass and C2 pedicle screw fixation and fusion. To conclude, when there is clinical suspicion for painful AAOA, providers have numerous diagnostic modalities, including newer hybrid techniques, that can be used to solidify the diagnosis. When conservative efforts fail, C1-2 fusion is an effective and enduring treatment for most patients.

C2 partial transpedicular screw technique for atlantoaxial dislocation with high-riding vertebral artery: A technique note with case series

ObjectiveAlthough the C2 pedicle screw (C2PS) is currently the most biomechanically robust option for C2 fixation, the high-riding vertebral artery (HRVA) precludes safe C2PS placement. However, unintentional partial C2 pedicle perforation and vertebral foramen violation due to C2PS placement without neurovascular complications occurred frequently in clinic. Therefore, we have attempted to apply C2 partial transpedicular screw (C2PTS) in patients with HRVA with satisfactory preliminary outcomes. The aim of the present study is to introduce the C2PTS technique and report the preliminary radiological and clinical outcomes of application of C2PTS. Patients and methodsThe data of 15 patients with atlantoaxial dislocation underwent atlantoaxial arthrodesis with posterior screw-rod construct were retrospectively reviewed. All patients had unilateral or bilateral HRVA that precluded safe C2PS placement and C2PTS was used as an alternative. In this technique, a Penfield dissector was used to properly mobilize the HRVA inferiorly to preclude vertebral artery injury and pave the way for C2PTS placement. The C2PTS travelled under the superior border of the isthmus and toward the ipsilateral atlantoaxial articulation. The implant position and atlantoaxial reduction were evaluated using computed tomography (CT) scans and vertebral artery (VA) was assessed using CT angiography postoperatively. ResultsSatisfactory C2PTS placement and atlantoaxial reduction were achieved in all patients. Postoperatively, no vertebral artery injury and implant failure were observed, and bone fusion was achieved in all the patients. Additionally, there were no VA occlusion or stenosis due to screws demonstrated on VA CT angiography. ConclusionC2PTS can achieve three-column fixation of axis and is an efficient alternative to C2PS which is prohibited due to HRVA; also, gently mobilizing the HRVA inferiorly is mandatory to prevent vertebral artery injury during C2PTS placement.

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.