C1 Lateral Mass C2 Research Articles

Posterior Reduction and Temporary Fixation Through Intermuscular Approach for Odontoid Fracture.

Posterior reduction and temporary fixation (PRTF) through open approach can effectively avoid the loss of C1-C2 motion caused by posterior atlantoaxial fusion in the treatment of odontoid fracture. PRTF through intermuscular approach can preserve the integrity of the paravertebral muscle. However, its contribution to the preservation of C1-C2 rotation remains unassessed in the context of fresh odontoid fractures. The data of 31 patients with odontoid fractures who underwent PRTF through intermuscular approach were retrospectively reviewed. Operation time, intraoperative blood loss, the time of ambulation and surgery-related complications were recorded. After fracture healing, the instrumentation was removed. The Japanese Orthopedic Association score, Visual Analog Scale score for neck pain, and patient satisfaction were recorded. The range of motion in rotation of C1-C2 was calculated 1 month after removing the instrumentation. Fracture healing was observed in all patients, and the instrumentation was removed. After removing the instrumentation, the range of motion of C1-C2 in rotation was returned to 35.6° ± 4.8°. Patient satisfaction was improved (P < .05). There was no significant difference in Japanese Orthopedic Association scores and Visual Analog Scale score for neck pain between 2 values before and after removing the instrumentation (P > .05). No osteoarthritis was observed at the C1-C2 lateral mass joints. There were no perioperative complications. PRTF through intermuscular approach can be used as a salvage treatment of an odontoid fracture with an intact transverse ligament in cases of failure of, or contraindication to, anterior screw fixation. This minimally invasive technique can effectively preserve the rotational function of the atlantoaxial complex.

C1 Lateral Mass-C2 Pars Fixation in Occipitalized Atlas with Fenestrated V3 Vertebral Artery-Operative Nuances Step by Step (Video Section).

C1 Lateral Mass-C2 Pars Fixation in Occipitalized Atlas with Fenestrated V3 Vertebral Artery-Operative Nuances Step by Step (Video Section).

Clinicoradiological evaluation and outcome assessment of single-stage posterior correction of atlantoaxial dislocation

Background: Atlantoaxial dislocation (AAD) refers to loss of stability between atlas and axis vertebrae, resulting in loss of normal articulation. It may be due to congenital, traumatic, or inflammatory reasons. Various techniques of atlantoaxial fixation have been described and used in patients over the years, but each has its own merits and demerits. Aims and Objectives: The aim of the study was to study clinicoradiological evaluation and outcome assessment of single-stage posterior correction of AAD. Materials and Methods: This is a prospective study done in the Department of Neurosurgery, JA group of hospitals, Gajra Raja Medical College, Gwalior, from July 2021 to July 2022. The study was conducted on 20 randomly selected patients whose presentation and imaging showed indication for surgery. Results: C1 lateral mass C2 pars screw fixation had one Frankel grade improvement in 6 months in 96% patient with a fusion rate of 100% and the patient also has modified Japanese orthopedic association score improvement of 15.25±0.98. Conclusion: This study reviewed single-stage posterior correction of AAD using C1 lateral mass and C2 pedicle screw and rod fixation; it enables the stabilization of atlantoaxial motion and preserves motion at occipito-atlantal level with high fusion rates, good neurological recovery, and minimal complications.

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.

Temporary Posterior C1-C2 Instrumentation without Fusion for Treatment of Displaced Atlantoaxial Fractures

To describe open reduction internal fixation (ORIF) with posterior C1-C2 instrumentation without fusion to treat displaced atlantoaxial fractures with later instrumentation removal. A retrospective review identified 14 patients (mean age 44 years) with displaced atlantoaxial fractures treated with ORIF without fusion. Patient demographics, fracture morphology, trauma etiology, instrumentation levels, timing of hardware removal, and complications were collected. Patients were maintained in a cervical collar, and healing was confirmed via imaging before instrumentation removal. Fractures included type III odontoid, C2 pars, C1 ring, and complex C1 or C2 fractures. All cases used C1 lateral mass screws and C2 pars or pedicle screws with a C1 cross-link. Two patients had C3 lateral mass screws. All patients showed fracture healing on imaging within 4 months after ORIF. Instrumentation removal was performed in 13 patients. No complications were noted. Displaced atlantoaxial fractures have been traditionally managed with halo-vest immobilization closed reduction or ORIF with fusion. ORIF without fusion and subsequent hardware removal is an alternative approach. This strategy preserves mobility at C1-C2, avoids halo-vest immobilization, and appears to be a safe option for treatment of atlantoaxial fractures.

Challenges and Outcomes of COVID-19 Positive Neurosurgical Patients: An Institutional Experience With Emphasis on Modifications of Neurosurgical Practice.

Introduction: There has been a drastic reduction in the number of neurosurgeries performed during the COVID-19 pandemic due to a multitude of challenges prompting restructuring of neurosurgical services. The present study describes the challenges and outcomes of non-elective neurosurgical procedures done on COVID-19 positive patients along with the modifications in neurosurgical practice during the pandemic.Methods: A retrospective study was done in the Department of Neurosurgery over a period of one year and three months. Demographic and clinical details including outcomes of the COVID-19 positive patients, who had undergone non-elective neurosurgical interventions, were collected.Results: Ten patients (3.8%) were COVID-19 positive out of 262 neurosurgical interventions done. The age of the patients ranged from 5 days to 78 years with five males and five females. Out of the 10 patients, five were neurotrauma cases including one patient of head injury with craniovertebral junction injury. The patient with craniovertebral junction injury underwent foramen magnum decompression with C1 lateral mass-C2 pedicle screw on the right and C0-C2 pedicle screw and rod fixation on the left. The rest of the neurotrauma cases underwent craniotomy or burr-hole craniostomy followed by evacuation. Only one patient (10%) had postoperative 30-day mortality. The rest nine patients (90%) survived the post-operative 30-day mortality. The various modifications incorporated in the neurosurgical practice included categorizing the emergency room into various zones, a separate operating theatre for COVID-19 patients, limiting the number of operating members as well as minor modifications in the operating procedures.Conclusions: The postoperative surgical outcome is favorable in COVID-19 positive patients with modifications of the existing neurosurgical practices.

Posterior First and Second Cervical Vertebrae Fusion by Screw Fixation Technique using the Modern Pre-fabricated Template Method on Cadaver Samples

Introduction:C1 lateral mass and C2 pedicular screws insertion are used for C1-C2 posterior fusion. Fluoroscopy Guided technique is routinely used for screw placement but it is associated with risk of injury to spinal cord and vertebral artery. 3D printing has developed rapidly in the fields of medicine. It is helpful in improving precise treatment and used for instrumentation in spine. We want to evaluate the accuracy of C1 lateral mass screws and C2 pedicle screws insertion by Pre-Fabricated Template made by three-dimensional (3D) printing.Materials and methods:Five cervical samples were obtained from cadavers. Based on fine-cut CT scan 3D-images reconstructed and the path of the screws designed by special software. A template produced by 3D-printer from 3D images. After printing the templates, they were fixed on the relevant vertebra in the operation room and based on the template path, C1 lateral mass screw and C2 pedicular screws were inserted. Placement of the screws was evaluated using CT scans post-operatively.Results:A total of 14 screws were inserted by above-mentioned method. After evaluation with CT scans none of the screws were entered in the spinal canal. Two screws had vertebral artery canal perforation with less than 50% breach. Violation was judged as noncritical and would probably not have resulted in injury to vertebral artery.Conclusions:The accuracy of C1 lateral mass screw and C2 pedicle screw insertion is acceptable with pre-fabricated template and can provide a useful aid for screw placement.

Posterior fusion for fragility type 2 odontoid fractures.

The purpose of this study was to evaluate the outcomes of elderly patients with type 2 odontoid fractures treated with an instrumented posterior fusion. Ninety-three consecutive patients older than 65 years of age in whom a type 2 odontoid fracture had been treated with a variety of C1-2 posterior screw fixation techniques were retrospectively reviewed. The average age was 78 years (range 65-95 years). Thirty-seven patients had an additional fracture, 30 of which involved C1. Three patients had cervical spinal cord dysfunction due to their injury. All patients had comorbidities. The average total hospitalization was 9.6 days (range 2-37 days). There were 3 deaths and 19 major complications, the most common of which was pneumonia. No patient suffered a vertebral artery injury. Imaging studies were obtained in 64 patients at least 12 months postsurgery (mean 19 months). Fusion was assessed by dynamic radiographs in all cases and with a CT scan in 80% of the cases. Four of the 64 patients did not achieve fusion (6.25% overall). All patients in whom fusion failed had undergone C1 lateral mass fixation and C2 pars (1/29, 3.4%) or laminar (3/9, 33.3%) fixation. Instrumented posterior cervical fusions may be performed in elderly patients with acceptable morbidity and mortality. The fusion rate is excellent except when bilateral C2 translaminar screws are used for axis fixation.

Retro-odontoid pseudotumor concomitant with proximal adjacent cervical spondylotic myelopathy after multilevel anterior cervical discectomy and fusion.

Introduction and importanceAdjacent cervical spondylotic myelopathy (CSM) following anterior cervical discectomy and fusion (ACDF) presenting as a retro-odontoid pseudotumor (ROP) is uncommon. This consequence adversely affects hand function, causes gait imbalance and results in other disabilities for the patient. This report describes the successful surgical treatment of a patient with ROP associated with adjacent CSM following multilevel ACDF of the subaxial cervical vertebrae by performing posterior cervical decompression and fusion.Case presentationA 60-year-old-male presented with progressive, disabling cervical myelopathy. He had undergone ACDF C3-C7 for treatment of CSM 16 years ago and his symptoms had fully resolved. Magnetic resonance imaging (MRI) revealed severe cervical spinal cord compression caused by a retro-odontoid mass at the C1-C2 level with upper adjacent segment disease (ASD) of C1-C3. The patient received C1-C3 posterior cervical spinal fusion by C1 lateral mass C2 and C3 pedicle screw fixation and C1-C3 laminectomy. After the surgery, he was able to ambulate independently and the myelopathic symptoms were significantly improved at the 6 months follow-up.Clinical discussionRetro-odontoid pseudotumor concomitant with proximal ASD following ACDF is a rare occurrence. Both diagnosis and surgical management are challenging.ConclusionsPosterior cervical decompression and fusion of C1-C3 is an effective option for treatment of severe cervical spinal cord compression by a retro-odontoid mass at the C1-C2 level combined with ASD after ACDF.

Three-dimensional reduction method with a modified C2 isthmus screw in irreducible atlantoaxial dislocation: a technical note

BackgroundThree-dimensional reduction plays a vital role in surgical reduction of irreversible atlantoaxial dislocation (IAAD). However, the most commonly used combination of C1 pedicle screw (PS) or lateral mass screw (LMS) and C2 PS or isthmus screw often fails to achieve satisfactory reduction at one time. The difficulty is usually caused by short anteroposterior and vertical distance between heads of C1 and C2 screws, which lack enough space for reduction operation. The objective of this study is to describe a three-dimensional reduction method with a modified C2 isthmus screw and to illustrate its advantage and effectiveness for IAAD.MethodsTwelve patients with IAAD underwent reduction and fixation with modified C2 isthmus screw combined with C1 PS or LMS, fusion with autologous bone graft. The insertion point was lateral to the intersection of caudal edge of C2 lamina and lateral mass, with a trajectory towards C2 isthmus, via lateral mass. The three-dimensional reduction was achieved through pulling and distracting. Radiographic evaluation included anteroposterior and direct distance between different insertion points, the occipitoaxial angle (O-C2A), clivus-canal angle (CCA) and cervicomedullary angle (CMA). Clinical outcomes evaluation included the Japanese Orthopaedic Association (JOA) score, Visual analog scale (VAS) and Neck Disability Index (NDI).ResultsAll the patients maintained effective reduction during the follow-up. The anteroposterior and direct distance was significantly higher in modified C2 isthmus screw than C2 PS whether combined with C1 PS or LMS (P < 0.05). The degree of O-C2A, CCA and CMA, JOA score, NDI, and VAS were significantly improved after the surgery (P < 0.05).ConclusionsThree-dimensional reduction method with a modified C2 isthmus screw is effective and safe in managing IAAD. It can increase the anteroposterior and vertical distance between the heads of C1 and C2 screws, which is benefit for the three-dimensional reduction operation of IAAD.

A novel 3D-printed locking cage for anterior atlantoaxial fixation and fusion: case report and in vitro biomechanical evaluation

BackgroundTreatment of atlantoaxial dislocation is aimed at reduction and stabilization of the atlantoaxial joint. 3D printing refers to a process where additive manufacturing is achieved under precise computer control. Literature on its utilization in anterior atlantoaxial fixation and fusion is rare. This study is the first report on a 3D-printed locking cage used in the anterior procedure for atlantoaxial dislocation.MethodsA middle-aged male in his 40s presented with weakness and numbness of his extremities for 3 years and could only walk slowly with assistance. Imaging studies revealed severe anterior migration of C1, irreducible atlantoaxial dislocation, and severe cervical-medullary compression. A preoperative plan consisting of trans-oral soft tissue release and fixation using tailor-designed 3D-printed cages was devised. Following fluoroscopic confirmation of reduction of the atlantoaxial joints, two customized 3D-printed cages made of titanium alloy were inserted into the bilateral facet joints, which were then locked by six screws into the lateral masses of C1 and C2. The microstructure of the inserted cages was optimized for improved biomechanical stability and enhanced osseo-integration, without the need for bone grafting. In addition, a biomechanical test was performed on seven human cadaveric specimens comparing the novel implant with the conventional C1 lateral mass-C2 pedicle screw construct in three modes of motion (flexion-extension, lateral bending, axial rotation).ResultsImprovement of neurologic function in the patient was evident immediately after surgery. He was able to walk independently 1 month post-operatively. At the 12-month follow-up, coronal reconstruction of CT demonstrated properly-positioned 3D-printed cages, evidence of osseo-integration at the bone-implant interface, and no subsidence or displacement of the implant. Eighteen months out of surgery, the mJOA score improved to 15, and lateral X-ray confirmed reduction of atlanto-axial dislocation. Additionally, the new construct provided strong fixation comparable to that conferred by conventional constructs as there was no significant difference observed between the two groups in all three directions of motion.ConclusionsThe novel implant represents a new option in the treatment of irreducible atlantoaxial dislocation. It can provide strong anterior support for solid fixation and fusion with a low profile and a microstructure that obviates the need for bone grafting.

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.

“Crossed C1 Lateral Mass–C2 Subfacetal Screw and Rod Construct” for Atlantoaxial Fixation in Patients with High-Riding Vertebral Artery: A Technical Note

Background: Goel–Laheri's posterior C1/C2 fixation technique is the gold standard procedure for atlantoaxial dislocation (AAD) and basilar invagination. Coexisitng vertebral artery anomalies such as high-riding vertebral arteries pose an increased risk of vertebral artery injury during instrumentation. Alternate technique for avoiding vertebral artery injury in such cases like translaminar screw fixation had been associated with a high chance for screw pull out, resulting in an unstable construct. This case report introduces a novel, cost-effective technique of atlantoaxial fixation with a “bilateral crossed C1 lateral mass-C2 subfacetal screw and rod construct” in patients with atlantoaxial subluxation with high-riding vertebral arteries.Case Presentation: A 63-year-old male presented with complaints of neck pain and difficulty in walking. On physical examination, he had features of high cervical myelopathy. Imaging revealed AAD with bilateral high-riding vertebral arteries. He was treated with “Crossed C1 lateral mass-C2 subfacetal screw and rod fixation” without evidence of vertebral artery injury or neurological deficits. Postoperatively, the patient showed significant improvement in pain and Nurick score.Conclusions: This technique has the uniqueness of providing a stable, rigid fixation of the atlantoaxial joint with screws inserted into the C2 body providing good bone purchase and at the same time avoid vertebral artery injury in high riding cases. The surgical technique is demonstrated in a detailed manner in this technical note.

Single-Staged Transoral Intra-Lesional Excision of Aneurysmal Bone Cyst of Axis (C2) Vertebra and Temporary Stabilization of Upper Cervical Spine in an Adolescent: A Case Report

Aneurysmal bone cyst (ABC) infrequently occurs within the upper cervical vertebrae. Various therapeutic options have been reported in the literature. We would like to share our experience in managing a case of a 16-year-old girl diagnosed with ABC at the body of axis (C2) vertebra. Serious attention had to be given on the stability of the cervical spine following tumour resection, which can be affected by the mode of treatment chosen. Instability can have a detrimental effect on the cervical spine, in which case may necessitate further surgery. We performed a single-staged intra-lesional curettage via a transoral approach and temporary non-fusion posterior stabilization of C1 lateral mass screw and C2 pedicle screw. The implants were removed after six months once ossification of C2 has taken place to regain full motion of the neck. There was no evidence of recurrence or instability of the cervical spine three years following surgery.

Comparison of Atlantoaxial Fusion with Transarticular Screws and C1 Lateral Mass–C2 Screws Using Intraoperative O-Arm Navigation

This study compared the surgical outcomes of atlantoaxial fusion with transarticular screws (TASs) and C1 lateral mass-C2 screws (screw-rod constructs [SRCs]) using the intraoperative O-arm navigation system (O-arm). Among a total of 28 patients who underwent atlantoaxial fixation, 13 underwent TAS fixation and 15 underwent SRC fixation using the O-arm. All patients underwent Brooks procedure with iliac bone graft in addition to screw fixation. TAS fixation was performed for cases without high-riding vertebral artery (hVA). In the SRC group, pars or lamina screws were inserted for the side with a C2 hVA. Operative time, intraoperative bleeding, perioperative complications, screw accuracy, and bone union were evaluated. There were statistically significant differences in mean operative time between the 2 procedures (166 minutes in the TAS group vs. 212 minutes in the SRC group, P < 0.05) and in mean blood loss (80 vs. 185 mL, respectively; P < 0.01). Two patients developed temporary postoperative occipital neuralgia probably related to C2 nerve root in the SRC group. No screws violated the cortex in either group. Complete bone union was observed in all cases. O-arm-assisted TAS fixation had less intraoperative blood loss, shorter operative time, and fewer screw insertion complications than O-arm-assisted SRC fixation. O-arm-assisted TAS fixation is preferable for atlantoaxial fusion in patients without hVA.

The Role of Transverse Connectors in C1-C2 fixation for Atlantoaxial Instability: Is It Necessary? A Biomechanical Study

To investigate the biomechanical effect of C1 lateral mass-C2 pedicle screw-rod (C1LM-C2PS) fixation with and without transverse connectors (TC) in an atlantoaxial instability (AAI) model. Ten freshly frozen cadaveric specimens were tested using an industrial robot under the following conditions: intact model, AAI model, C1-C2 model, C1-C2 with one TC model, and C1-C2 with two TCs model. Three types of motion, flexion-extension (FE), lateral bending (LB), and axial rotation (AR), were applied (1.5 Nm) to the specimens. The range of motion (ROM) and neutral zone (NZ) between C1 and C2 in all directions were measured. Compared with those of the intact and AAI models, the C1-C2 ROM and NZ of all instrumented groups were decreased significantly in each direction of loading motion (P < 0.05). The mean FE ROM in the no TC, 1 TC, and 2 TC groups was 2.12° ± 0.41°, 2.29° ± 0.42°, and 2.04° ± 0.69°, respectively (P= 0.840, 0.981, 0.628, respectively); the mean LB ROM in the 3 intervention groups was 1.26° ± 0.67°, 1.02° ±0.51° and 1.03° ± 0.57°, respectively (P= 0.489, 0.501, 1.000, respectively). During AR, the ROM and NZ of the no TC group (3.19° ± 0.89° and 1.51° ± 0.42°) were significantly reduced by more than 60% compared with those in the 1 (0.98° ± 0.28° and 0.40° ± 0.11°) and 2 TC groups (1.17° ± 1.69° and 0.42° ± 0.61°) (P < 0.001). Two TCs were equivalent for all loading motions to 1 TC (P > 0.05). Adding TCs to C1LM-C2PS can effectively decrease the axial rotation ROM and enhance the stability of C1-C2 segment. Therefore, it is necessary to use TC-strengthened C1 lateral mass -C2 pedicle screw-rod fixation in patients with instability of C1-C2.

Endoscopically-Assisted Percutaneous Unilateral Atlantoaxial Screw-Rod Nonfusion Fixation Treatment for Type II Odontoid Fractures in Geriatric Patients: Case Series and Technical Note

Considerable controversy exists regarding the optimal treatment for type II odontoid fractures in geriatric patients. Surgical intervention can help patients return to their prior level of function as rapidly as possible while avoiding the morbidity and mortality associated with prolonged and bedbound hospitalization. However, the optimal treatment is still a difficult choice for patients with increased risk from anesthesia. The objective of our study was to describe an innovative method of endoscopically-assisted percutaneous unilateral C1 lateral mass screw and C2 pedicle screw-rod nonfusion fixation for type II odontoid fractures in geriatric patients. A case series design and technical notes. This study took place at Second Affiliated Hospital of Chongqing Medical University. Seven geriatric patients (> 65 years) with type II odontoid fractures and an American Society of Anesthesiologists (ASA) score of 2 or higher received endoscopically-assisted percutaneous unilateral atlantoaxial screw-rod nonfusion fixation. After surgery, all patients were required to wear a rigid collar full-time for 12 weeks. Intraoperative data, the bone union time, American Spinal Injury Association (ASIA) scale scores, Neck Disability Index (NDI) scores, and postoperative complications were collected for assessment.RESULTS The surgical goal was successfully achieved in all patients, 3 of whom had high ASA scores (>= 3) and underwent surgery under local anesthesia. The operative time ranged from 112 to 169 minutes (mean, 131.1 minutes). No neurovascular complications were observed intraoperatively or postoperatively. All patients rapidly returned to their prior level of function and were followed up for 12 to 24 months (average: 16.9 months). Bone union was achieved in all patients. This study is limited by being a retrospective study. Endoscopically-assisted percutaneous unilateral atlantoaxial screw-rod nonfusion fixation is a feasible technique for type II odontoid fractures in geriatric patients. This method offers a compromise between non-operative and operative treatment and allows geriatric patients to rapidly return to their prior level of function. Endoscopically-assisted surgery; geriatric patient; percutaneous atlantoaxial fixation; type II odontoid fracture; unilateral nonfusion fixation.

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

The authors conducted a study to investigate the biomechanical feasibility and stability of C1 lateral mass-C2 bicortical translaminar screw (C1LM-C2TL) fixation, C1 lateral mass-C2/3 transarticular screw (C1LM-C2/3TA) fixation, and C1LM-C2/3TA fixation with transverse cross-links (C1LM-C2/3TACL) as alternative techniques to the Goel-Harms technique (C1 lateral mass-C2 pedicle screw [C1LM-C2PS] fixation) for atlantoaxial fixation. Eight human cadaveric cervical spines (occiput-C7) were tested using an industrial robot. Pure moments that were a maximum of 1.5 Nm were applied in flexion-extension (FE), lateral bending (LB), and axial rotation (AR). The specimens were first tested in the intact state and followed by destabilization (a type II odontoid fracture) and fixation as follows: C1LM-C2PS, C1LM-C2TL, C1LM-C2/3TA, and C1LM-C2/3TACL. For each condition, the authors evaluated the range of motion and neutral zone across C1 and C2 in all directions. Compared with the intact spine, each instrumented spine significantly increased in stability at the C1-2 segment. C1LM-C2TL fixation demonstrated similar stability in FE and LB and greater stability in AR than C1LM-C2PS fixation. C1LM-C2/3TA fixation was equivalent in LB and superior in FE to those of C1LM-C2PS and C1LM-C2TL fixation. During AR, the C1LM-C2/3TA-instrumented spine failed to maintain segmental stability. After adding a cross-link, the rotational stability was significantly increased in the C1LM-C2/3TACL-instrumented spine compared with the C1LM-C2/3TA-instrumented spine. Although inferior to C1LM-C2TL fixation, the C1LM-C2/3TACL-instrumented spine showed equivalent rotational stability to the C1LM-C2PS-instrumented spine. On the basis of our biomechanical study, C1LM-C2TL and C1LM-C2/3TACL fixation resulted in satisfactory atlantoaxial stabilization compared with C1LM-C2PS. Therefore, the authors believe that the C1LM-C2TL and C1LM-C2/3TACL fixation may serve as alternative procedures when the Goel-Harms technique (C1LM-C2PS) is not feasible due to anatomical constraints.

Minimally Invasive Percutaneous C1-C2 Fixation Using an Intraoperative Three-Dimensional Imaging–Based Navigation System for Management of Odontoid Fractures

Odontoid fractures are the most common lesions of the upper cervical spine in patients >70 years old. These fractures are associated with frequent comorbidities, and minimally invasive techniques might have the potential to reduce postoperative complications while ensuring better precision. The aim of this study was to report an innovative technique and preliminary results of minimally invasive atlantoaxial fixation using a three-dimensional intraoperative navigation system and percutaneous approach. This retrospective study included 5 consecutive patients with an acute traumatic odontoid type II fracture managed using a percutaneous Harms fixation under three-dimensional intraoperative navigation guidance. C1 lateral mass screws and C2 isthmus screws were successfully placed in all patients. In all cases (100%), adequate screw positioning with no medial breach and no transverse foramen obstruction was observed. No intraoperative complications, such as injury of the vertebral artery, spinal nerve root, or spinal cord, occurred. None of the 5 patients received blood transfusion during or after the procedure. During the follow-up period (mean, 11.2 months; range, 5-16 months), 4 patients (80%) demonstrated a favorable clinical recovery, and only 1 patient required occasional medication for moderate pain. Mean radiation exposure was 4.83 mSV for each patient and 0 mSv for surgical staff. Minimally invasive atlantoaxial fixation using an intraoperative three-dimensional navigation system is a safe and effective alternative to the conventional approach that reduces postoperative morbidity.

Intraoperative imaging and navigation for C1-C2 posterior fusion.

Background:Cervical axial spine fusion is challenging as the anatomy is extremely variable, and screw misplacement can lead to severe complications. C1 lateral mass screws and C2 pedicle screws are routinely placed under either fluoroscopic guidance or imaging-assisted navigation. Here, we compared the two for axial screw placement.Methods:We retrospectively evaluated patients’ treated from 2011–2016 utilizing the Harm’s procedure for C1-C2 screw fixation performed under either fluoroscopic guidance (nine patients) or image-assisted O-arm navigation (five patients). The groups had similar demographic and risk factors. Variables studied included operative time, estimated blood loss (EBL), accuracy of screw placement, screw reposition rates, and reoperation rates.Results:The mean EBL was 555CC and 260CC, respectively (not a significant difference) utilizing fluoroscopic versus O-arm navigation. Of interest, the mean surgical duration was 27 min longer in the O-arm versus fluoroscopy group (P = 0.03). Ten C2 pedicle screws were performed using O-arm navigation. Alternatively, as 9 of 18 C2 pedicles were considered “risky” for the placement of fluoroscopic-guided pedicle screws, laminar screws were utilized. Although the accuracy rate of C1 and C2 screw placement was higher for the navigated group, this finding was not significant. Similarly, despite complications involving two unacceptably placed screws from the fluoroscopic guidance group, there were no neurological sequelae.Conclusion:Axial cervical spine instrumentation is challenging. Utilization of Imaging-assisted navigation increases the accuracy and safety of screw placement.