Odontoid Fractures

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Continuing Education Activity

The odontoid process, or dens, is a superior projecting bony element from the second cervical vertebrae (C2, or the axis). The first cervical vertebrae (atlas) rotates around the odontoid process to provide the largest single component of lateral rotation of the cervical spine. Fracture of the odontoid process is classified into one of three types, which are type I, type II, or type III fractures, depending on the location and morphology of the fracture. The most common mechanism of injury is a hyperextension of the cervical spine, pushing the head and C1 vertebrae backward. This activity reviews the etiology, presentation, evaluation, and management of fractures of the C2 dens and reviews the role of the interprofessional team in evaluating, diagnosing, and managing the condition.

Objectives:

  • Describe the unique vertebral anatomy of the second cervical vertebra (axis), including the odontoid process.
  • Discuss the components of proper evaluation and assessment of a patient presenting with a potential odontoid process fracture, including any indicated imaging studies.
  • Summarize the treatment and management strategies available for C2 odontoid fractures based on the specific fracture type.
  • Discuss the importance of interprofessional team strategies for improving care coordination and communication to aid in prompt diagnosis of C2 odontoid fracture and improving outcomes in patients diagnosed with the condition.

Introduction

The odontoid process, or dens, is a superior projecting bony element from the second cervical vertebrae (C2, or the axis). The first cervical vertebrae (atlas) rotates around the odontoid process to provide the largest single component of lateral rotation of the cervical spine. Fracture of the odontoid process is classified into one of three types: type I, type II, or type III fractures, depending on the location and morphology of the fracture.[1]

Etiology

Odontoid fractures occur as a result of trauma to the cervical spine. In younger patients, they are typically the result of high-energy trauma, which occurs as a result of a motor vehicle or diving accident. In the elderly population, the trauma can occur after lower energy impacts such as falls from a standing position. The most common mechanism of injury is a hyperextension of the cervical spine, pushing the head and C1 vertebrae backward. If the energy mechanism and resulting force are high enough (or the patient's bone density is compromised secondary to osteopenia/osteoporosis), the odontoid will fracture with varying displacement and degrees of comminution. 

The odontoid fracture can also occur with hyperflexion of the cervical spine. The transverse ligament runs dorsal to (behind) the odontoid process and attaches to the lateral mass of C1 on either side. If the cervical spine is excessively flexed, then the transverse ligament can transmit the excessive anterior forces to the odontoid process and cause an odontoid fracture.[1]

Epidemiology

Odontoid fractures account for 20% of cervical spine fractures in the adult population and are the most common fracture subtype in geriatric patients (≥ 65 years).[2] The axis (C2) is the most common vertebra to be involved in cervical spine injuries, and odontoid fractures account for 50% of all C2 fractures.[3] This shows bimodal distribution with peaks among early adults and the elderly population.[2]

Odontoid fractures result from an interaction between the load magnitude and bone quality.[4] This results from high-impact forces in young cohorts but with trivial injuries among elders. Hyperextension injury causes the skull and C1 arch to cause traction at the odontoid process, while the hyperflexion injury causes the transverse ligament to limit the posterior movement of dens.[5] Type II is the most common of the types of odontoid fractures and accounts for over 50% of all odontoid fractures. Type III odontoid fractures make up most of the remaining odontoid fractures. Type I odontoid fractures are rare.[1] Road traffic accidents are accountable for the majority of cases.[3] In a study comprising more than 30,000 patients, the average age of the cohorts was 77, and 54% were females.[6]

Pathophysiology

Advanced age and large occiput-C2 angles are predictive of the odontoid fracture angle.[7]

The atlantoaxial joint and fractured segment all move in unison, causing unbearable pain during neck movements.[5] The nonunion rate following conservative management can be as high as 90% owing to thin bony trabeculae and watershed zone at the base of dens.[5]

Non-operative management of odontoid fractures can result in the following:

  • Solid fusion
  • Unstable nonunion, or
  • Fibrous nonunion.[8]

The fusion is governed by the following:

  • Pattern of injury
  • Fracture subtype
  • The slope of the fracture line
  • Angulation (more or less than 11 degrees
  • Displacement (more or less than 5 mm)
  • Blood supply
  • Bone quality, and
  • Age of the fracture and that of the patient.[2]

History and Physical

Younger patients with an odontoid fracture typically have identifiable recent trauma (motor vehicle accident, sports-related impact, diving accident, fall from a height or downstairs). Older patients tend to have less resilient bones and can sustain an odontoid fracture after minor trauma, including falling from ground level or running into a door or cabinet. However, older individuals can also sustain an odontoid fracture from recent injuries similar to those of younger people. 

On physical exam, patients may note cervical neck pain, which is worse with motion. They can also have dysphagia due to a retropharyngeal hematoma or associated parapharyngeal swelling. Less commonly, the patient may have myelopathic spinal cord injuries such as paresthesias in the arms and/or legs, weakness of the arms and/or legs, or other neurologic dysfunctions. There are fewer spinal cord injuries in odontoid fractures due to the relatively large cross-sectional diameter of the spinal canal at the level of the odontoid process compared to the diameter of the spinal cord.

Evaluation

 X-rays of the cervical spine constitute lateral, anterior-posterior (AP), and open-mouth views. Although radiographs yield lower sensitivity and specificity rates when compared to computed tomogram (CT) scans, experienced clinicians and practitioners can still appreciate suspected injury without CT utilization. In addition, flexion-extension radiographs should be obtained in the setting of suspected occipitocervical instability (useful in type I odontoid fractures or the setting of os odontoideum). Initial stability on upright radiographs is associated with stability on follow-up.[9]

Computerized tomography (CT) spine - provides the best resolution of the bony elements allowing for the identification and characterization of an odontoid fracture. This also allows recognition of anatomic anomalies, such as the defect of the posterior arch of C1, that can help plan the management strategies.[10] CT angiography is justified in cases with fracture extension within the vicinity of the vascular zone and assessing the course of the vertebral artery during posterior fixation.[11]

Magnetic resonance imaging- to assess the integrity of the transverse ligament well as the cord among patients presenting with neurological deficits.[12] 

Classification of Odontoid Fractures

  1. Type I- involves the apex of the dens and is mostly stable. If instability due to the avulsion of the alar ligament is suspected, dynamic radio imaging is advocated.
  2. Type II- involves the neck of the odontoid process. They are categorized depending on the pattern of the fracture line into anterior oblique, posterior oblique, and horizontal variants.[5] They are the most common subtype and are mostly considered unstable. Type IIA variant has comminuted fractures at the base of the dens and is unstable.[5]

Grauer Classification

  • Type IIA- non-displaced and no comminution
  • Type IIB- fracture line running anterosuperior to the posteroinferior direction
  • Type IIC- Fracture line running anteroinferior to posterosuperior direction, or with significant comminution.[13][14]

      3. Type III- fracture extends into the body of C2.[14] Non-surgical treatment remains the preferable option for the majority of these patients.[15]

Treatment / Management

Achieving fracture stability is the mainstay of management.[2] The fibrous union can provide adequate stability.[9][16] Without instability on flexion/extension views or ligamentous injury on an MRI scan, a rigid brace or halo vest can be used to promote healing of the fracture, which may occur in 12 weeks.[9]

A conservative approach may be justified for patients with the following:

  • Good alignment with
  • No dynamic instabitiy
  • No deficits.[8]

Type I and Type III fractures Halo fixation or cervical traction and rigid cervical collar result in fusion in:

  • 100% of type 1 in the majority of cases
  • Approximately 90% of type III fractures, and
  • 60% of type II fractures.[12]

A cervical collar is biomechanically superior to halo orthoses with minimal risk of concurrent device-related complications.[2] Soft collars provide comparable benefits in aged patients compared to rigid collars.[17] The use of halo-vest was not associated with increased mortality.[18]Conservative treatment and surgery had similarly low in-hospital mortality.

Indications for Surgery in Type II Fractures

  • Unstable fracture
  • Irreducible fracture
  • Nonunion, and
  • Patients with deficits.[5]

Criteria of instability

  • Fracture age equal to or more than six months 
  • Comminuted fracture
  • Rupture of the transverse ligament
  • Non-reducible or mal-aligned fracture pattern,
  • Dens displacement more or equal to 6 mm,
  • Angulation greater more or equal to 10 degrees or
  • Fracture gap more than or equal to 2 mm
  • Lateral mass gap  >2 mm.[19][20]

Both anterior and posterior fixation techniques have equivalent clinical results.[5] Anterior odontoid screw fixation preserves neck movements while providing fusion rates of  80%–100%.[5]

The posterior inferior fracture type and concurrent tear of the transverse ligament are selected for the posterior fixation.[5]Historically, posterior cervical fusion was undertaken by Brooks, Gallie, and later Dickman and Sonntag methods incorporating the use of sublaminar wires and bone grafts, providing a fusion rate of 86%. This was followed by a transarticular screw, as described by Jeanneret and Magerl, which provided almost 100% fusion.[12] The Goel-Harms technique (C1 lateral mass and C2 pedicle screws) is now an excellent alternative to anterior fixation.[21][22] After the advent of the Goel posterior joint manipulation technique, most of the once irreducible atlantoaxial dislocations (AAD) could be reduced, and the need for transoral odontoidectomy became almost nil.[23] Bone grafting provides long-term stability.[12] Sublaminar wiring can impinge upon the spinal canal, and C1-2 joint fusion restricts neck ranges of movements.[12]

Nakanishi described the technique of anterior odontoid screw fixation.

Anterior fixation is advocated for:

  • Fractures < 6 months old and
  • Anterior-inferior sloping fracture line,
  • Transverse without any comminuting segments at the base.[2][5]

There is no need for bone grafting and minimal risk of injury to the vertebral artery. There are also mild limitations in functional abilities following the procedure.[24]

Prerequisites for the anterior odontoid screw fixation include:

  • Intact transverse ligament, and
  • Reduction and proper alignment following traction.[5]

The bicortical purchase and superior and posterior breach of the odontoid tip significantly govern postoperative alignment.[25] Lag, Herbert, and Acutrak screws are used for anterior odontoid fixation.[26][27] Both single or two-screw anterior odontoid screws have shown similar clinical results.[12] There are anatomical limitations and variability in the placement of two odontoid screws.[28][29]

Subsets not appropriate for anterior odontoid screw fixation include:

  • Type II-a fractures
  • Rupture of the transverse ligament
  • Associated atlantoaxial dislocation
  • Osteopenia
  • >6 months of injury
  • Anterior oblique fracture slope
  • Short neck
  • Barrel-shaped chest, and
  • Severe kyphosis.[5][19]

Recent advances in assisting instrumentation include:

The odontoid screw fixation technique is not recommended for children under six years old.[36] This technique is feasible for children aged 6 to 18 years old; appropriate screw diameter, length, and angle according to the actual CT measurement result is critical.[36]An anterior approach is more suitable for younger cohorts.[2]

There is a level II recommendation for surgical stabilization in geriatric patients due to the high risk of high nonunion.[5] Meta-analysis has revealed better fusion with posterior fixations.[5] There is a high risk of reoperation rates owing to osteopenia following anterior odontoid fixation.[22] There is also an increased risk of postoperative pneumonia, swallowing dysfunction, and increased technical problems.[2][19]

There is marked variation in the treatment strategies as well as follow-up and imaging algorithms.[37] Major comorbidities and older age are significant factors in refraining from surgical fixation.[38] The proportion of crossover from primary external immobilization to surgery was 14.4%, whereas the proportion of revision surgery in the primary surgical group was 9.5%.[39] Operative treatment has shown an average increase of 3.7% per year; operative management nearly doubled between 2003 to 2017 for managing geriatric odontoid fractures.[6] [Level 3] Increased sagittal balance and bone fusion within the atlantodental interspace confer a high risk of nonunion.[40] Duration from injury to surgery > 7 days appears to have a 48 times higher risk for nonunion in elderly patients despite anterior odontoid screw fixation.[41]

Differential Diagnosis

Some entities can be mistaken for an odontoid fracture. It is important to recognize these to avoid unnecessary interventions.

Os Odontoideum 

Os odontoideum is a recognized anatomical variant of the normal C2 odontoid process. During the development, there are multiple ossification centers in the spine, with one being in the odontoid process, one in the odontoid tip, and one in the vertebral body. If the ossification centers in the odontoid process and the vertebral body fail to fuse, then the odontoid process (dens) can appear to be detached from the vertebral body and mimic a type II odontoid fracture. In younger children, complete ossification of the spine has not yet occurred, and the normal growth pattern and ossification can also mimic a type II odontoid fracture.

Persistent Ossiculum Terminale 

The rostral tip of the odontoid process has a separate ossification center during development from the remaining odontoid process. When the two ossification centers fail to fuse, there can be a persistent gap between the odontoid process and the tip of the odontoid process, which can mimic a type I odontoid fracture.

Prognosis

Children achieve stable fusion with halo immobilization. However, patients over 50 years of age have 21 times high risk of nonunion with halo immobilization.[12]

The fusion rate is 88% when the surgery is performed within six months of allowing a fusion rate of 88%, but it drops to 25% when surgery is performed more than 18 months after injury.[12] If a patient fails external immobilization and is within six months of the injury, anterior odontoid screw placement is still an option.

Displaced distal fracture segment or facetal malalignment causing cervicomedullary compression and irreducible despite traction previously required transoral resection preceding posterior fusion. Anterior extrapharyangeal open reduction and internal fixation have now been introduced to manage the same.[42]

Complications

Mortality at the time of injury is observed in 25% to 40% of patients.[43]

Most of the survivors are usually neurologically intact. However, this can harbinger the risk of instability at the atlantoaxial region and spinal cord injury, causing Brown-Sequard syndrome, spinal Cord transection, cruciate paralysis, myelopathy, and persistent disabling neck pain in around 25% of patients.[12][44][45]

There can be concurrent injuries associated with and complicating the odontoid fractures, which include:

  • Anterior cervical wedge fracture
  • Atlanto occipital dissociation
  • Cervical burst fracture
  • Cervical facet dislocation
  • Cervical spinous process fracture
  • Extension cervical teardrop fracture
  • Flexion cervical teardrop fracture 
  • Hangman's fracture
  • Isolated transverse process fractures, and
  • Jefferson fracture

Deterrence and Patient Education

Postoperatively, patients should be monitored for retropharyngeal hematoma, dysphagia, aspiration, vocal cord paralysis, and surgical site infections. The patient needs to understand these signs and symptoms and contact their surgeon's office immediately if these present.

Enhancing Healthcare Team Outcomes

Odontoid fractures most often occur as a result of trauma to the cervical spine. Patients are often younger. The clinicians must work together in a coordinated interprofessional team approach to care that minimizes the risk of further injury. Trauma nurses are responsible for cervical spine immobilization—radiologists review X-rays and scans. Neurosurgeons and orthopedists provide definitive care. Physiatrists and rehabilitation nurses coordinate care and feedback to the interprofessional team. Often pharmacist assists the team in helping to maintain pain control in the acutely injured patient. Nurses can serve as the liaison point between the various disciplines, assist in patient assessment and during surgery, monitor patients, and answer patient questions. All care team members must maintain accurate and updated patient records so that every team member is operating from the same information. This interprofessional team approach will lead to improved patient outcomes. [Level 5]



(Click Image to Enlarge)
Anderson and D'Alonzo classification of odontoid fractures.
Anderson and D'Alonzo classification of odontoid fractures.
Contributed by Steven O Tenny, MD, MPH, MBA

(Click Image to Enlarge)
Odontoid fracture
Odontoid fracture
Contributed by Sunil Munakomi, MD

(Click Image to Enlarge)
Odontoid fracture
Odontoid fracture
Contributed by Sunil Munakomi, MD
Article Details

Article Author

Steven Tenny

Article Author

Sunil Munakomi

Article Editor:

Matthew Varacallo

Updated:

11/16/2022 10:57:23 AM

PubMed Link:

Odontoid Fractures

References

[1]

C2 Fracture Subtypes, Incidence, and Treatment Allocation Change with Age: A Retrospective Cohort Study of 233 Consecutive Cases., Robinson AL,Möller A,Robinson Y,Olerud C,, BioMed research international, 2017     [PubMed PMID: 28182084]

[2]

Deluca A,Wichlas F,Deininger C,Traweger A,Mueller EJ, Reevaluation of a classification system: stable and unstable odontoid fractures in geriatric patients-a radiological outcome measurement. European journal of trauma and emergency surgery : official publication of the European Trauma Society. 2022 Aug     [PubMed PMID: 35597894]

[3]

Bakhsh A,Alzahrani A,Aljuzair AH,Ahmed U,Eldawoody H, Fractures of C2 (Axis) Vertebra: Clinical Presentation and Management. International journal of spine surgery. 2020 Dec     [PubMed PMID: 33560250]

[4]

Benca E,Zderic I,van Knegsel KP,Caspar J,Hirtler L,Fuchssteiner C,Strassl A,Gueorguiev B,Widhalm H,Windhager R,Varga P, Biomechanical Assessment of Fracture Loads and Patterns of the Odontoid Process. Spine. 2022 Sep 1     [PubMed PMID: 35853162]

[5]

Sommer F,Kirnaz S,Goldberg J,McGrath L Jr,Navarro-Ramirez R,Gadjradj P,Medary B,Härtl R, Treatment of Odontoid Fractures in Elderly Patients Using C1/C2 Instrumented Fusion Supplemented With Bilateral Atlantoaxial Joint Spacers: A Case Series. International journal of spine surgery. 2022 Jun     [PubMed PMID: 35772974]

[6]

Alluri R,Bouz G,Solaru S,Kang H,Wang J,Hah RJ, A Nationwide Analysis of Geriatric Odontoid Fracture Incidence, Complications, Mortality, and Cost. Spine. 2021 Jan 15;     [PubMed PMID: 33038203]

[7]

Gold C,Seaman S,Yamaguchi S, Relationship between odontoid fracture angle and cervical sagittal balance. Surgical neurology international. 2021     [PubMed PMID: 33948327]

[8]

Florman JE,Gerstl JVE,Kilgallon JL,Riesenburger RI, Fibrous Nonunion of Odontoid Fractures: Is It Safe To Accept Nonoperative Management? A Systematic Review. World neurosurgery. 2022 Aug;     [PubMed PMID: 35659587]

[9]

Wilson C,Hoyos M,Huh A,Priddy B,Avila S,Mendenhall S,Anokwute MC,Eckert GJ,Stockwell DW, Institutional review of the management of type II odontoid fractures: associations and outcomes with fibrous union. Journal of neurosurgery. Spine. 2021 Jan 22     [PubMed PMID: 33482645]

[10]

Butt BB,Gagnet P,Patel R,Aleem I, Congenital defect of the posterior arch of C1: a case report. Journal of spine surgery (Hong Kong). 2021 Jun     [PubMed PMID: 34296035]

[11]

Windsor TA,Tewelde SZ,Blosser KM,Richardson AC, An odontoid fracture and vertebral artery injury in fast-track. Clinical case reports. 2020 Sep;     [PubMed PMID: 32983515]

[12]

Rao G,Apfelbaum RI, Odontoid screw fixation for fresh and remote fractures. Neurology India. 2005 Dec     [PubMed PMID: 16565532]

[13]

Moscolo F,Meneghelli P,Boaro A,Impusino A,Locatelli F,Chioffi F,Sala F, The use of Grauer classification in the management of type II odontoid fracture in elderly: Prognostic factors and outcome analysis in a single centre patient series. Journal of clinical neuroscience : official journal of the Neurosurgical Society of Australasia. 2021 Jul     [PubMed PMID: 34119278]

[14]

Fazzolari B,Jannelli G,Conti E,Delitala A,Tessitore E,Brunori A, Clinical and radiological outcome after minimally invasive surgical approach for type II unstable odontoid fractures. Neuro-Chirurgie. 2021 Jul     [PubMed PMID: 33338497]

[15]

Rizvi SAM,Helseth E,Aarhus M,Harr ME,Mirzamohammadi J,Rønning P,Mejlænder-Evjensvold M,Linnerud H, Favorable prognosis with nonsurgical management of type III acute odontoid fractures: a consecutive series of 212 patients. The spine journal : official journal of the North American Spine Society. 2021 Jul     [PubMed PMID: 33577924]

[16]

Sucu HK, A True Percutaneous Anterior Odontoid Screw Fixation: The Results of 42 Cases by a Single Surgeon. World neurosurgery. 2022 Oct     [PubMed PMID: 35948230]

[17]

Coleman N,Chan HH,Gibbons V,Baker JF, Comparison of Hard and Soft Cervical Collars for the Management of Odontoid Peg Fractures in the Elderly. Geriatric orthopaedic surgery & rehabilitation. 2022     [PubMed PMID: 35320993]

[18]

Honda A,Michihata N,Iizuka Y,Mieda T,Takasawa E,Ishiwata S,Matsui H,Fushimi K,Yasunaga H,Chikuda H, Clinical features and early post-operative complications of isolated C2 odontoid fractures: a retrospective analysis using a national inpatient database in Japan. European spine journal : official publication of the European Spine Society, the European Spinal Deformity Society, and the European Section of the Cervical Spine Research Society. 2021 Dec     [PubMed PMID: 33959795]

[19]

Fiani B,Doan T,Covarrubias C,Shields J,Sekhon M,Rose A, Determination and optimization of ideal patient candidacy for anterior odontoid screw fixation. Surgical neurology international. 2021     [PubMed PMID: 34084598]

[20]

Koshimizu H,Nakashima H,Ito K,Ando K,Kobayashi K,Kato F,Sato K,Deguchi M,Matsubara Y,Inoue H,Kanemura T,Urasaki T,Yoshihara H,Wakao N,Shinjo R,Imagama S, Risk factors of non-union in Anderson-D'Alonzo type III odontoid fractures with conservative treatment. Journal of orthopaedics. 2021 Mar-Apr     [PubMed PMID: 33897130]

[21]

Yee TJ,Strong MJ,Willsey MS,Oppenlander ME, Cervical 1-2 Posterior Instrumented Fusion Utilizing Computer-Assisted Navigation With Harvest of Rib Strut Autograft: 2-Dimensional Operative Video. Operative neurosurgery (Hagerstown, Md.). 2021 May 13     [PubMed PMID: 33571358]

[22]

Jain AK,Tawari M,Rathore L,Sahana D,Mishra H,Kumar S,Sahu RK, An experience with Goel-Harms C1-C2 fixation for type II odontoid fractures. Journal of craniovertebral junction & spine. 2022 Apr-Jun     [PubMed PMID: 35837432]

[23]

Govindasamy R,Preethish-Kumar V,Gopal S,Rudrappa S, Is Transoral Surgery Still a Relevant Procedure in Atlantoaxial Instability? International journal of spine surgery. 2020 Oct     [PubMed PMID: 33077434]

[24]

Wolan-Nieroda A,Maciejczak A,Drużbicki M,Guzik A, Determinants of health-related quality of life in patients with fracture of the axis vertebrae. Scientific reports. 2021 Sep 24     [PubMed PMID: 34561492]

[25]

Tyagi G,Patel KR,Singh GJ,Uppar AM,Beniwal M,Rao KVLN,Pruthi N,Bhat D,Somanna S,Chandramouli B,Dwarakanath S, Anterior Odontoid Screw Fixation for C2 Fractures: Surgical Nuances, Complications, and Factors Affecting Fracture Union. World neurosurgery. 2021 Aug;     [PubMed PMID: 34058365]

[26]

Duransoy YK,Mete M,Ünlü Ünsal Ü,Aydın M,Zileli M, Anterior odontoid screw fixation using Acutrak screw: Report of 19 patients. Ulusal travma ve acil cerrahi dergisi = Turkish journal of trauma & emergency surgery : TJTES. 2021 Jul     [PubMed PMID: 34213004]

[27]

Pongmanee S,Kaensuk S,Sarasombath P,Rojdumrongrattana B,Kritworakarn N,Liawrungrueang W, Anterior screw fixation for type II odontoid process fractures: A single-center experience with the double Herbert screw fixation technique (Retrospective cohort study). Annals of medicine and surgery (2012). 2022 Feb;     [PubMed PMID: 35198171]

[28]

Acharya S,Kumar M,Ghosh JD,Adsul N,Chahal RS,Kalra KL, Morphometric parameters of the odontoid process of C2 vertebrae, in Indian population, a CT evaluation. Surgical neurology international. 2021;     [PubMed PMID: 34754544]

[29]

Choudhary KS,Doddamani RS,Devarajan LJ,Agrawal M,Sawarkar D,Meena RK,Varma S,Kumar A,Singh P,Chandra PS,Kale SS, Feasibility of Double Anterior Odontoid Screw: A CT-Based Morphometric Analysis of the Axis in Adult Indian Population. Neurology India. 2020 Nov-Dec     [PubMed PMID: 33342869]

[30]

Zhao R,Ding W,Li X,Han FY,Yang D,Yang S, Application of the O-arm Intraoperative Imaging System to Assist Anterior Cervical Screw Fixation for Odontoid Fractures. Journal of visualized experiments : JoVE. 2022 Aug 30     [PubMed PMID: 36121255]

[31]

Abreu PG,Romero C,Lourenço JAB,Pappamikail L,Brito M,Teles P,Correia J, Case report: Challenging post-traumatic pseudoarthrosis of C2 odontoid fracture and extreme C1-C2 subluxation. Surgical neurology international. 2022;     [PubMed PMID: 35509539]

[32]

Li Y,Lin J,Wang Y,Luo H,Wang J,Lu S,Xu Y, Comparative study of 3D printed navigation template-assisted atlantoaxial pedicle screws versus free-hand screws for type II odontoid fractures. European spine journal : official publication of the European Spine Society, the European Spinal Deformity Society, and the European Section of the Cervical Spine Research Society. 2021 Feb     [PubMed PMID: 33098009]

[33]

Kedia S,Sawarkar D,Sharma R,Mansoori N,Lalwani S,Gupta D,Kumar R,Kale SS, Endoscopic Anterior Odontoid Screw Fixation for the Odontoid Fracture: A Cadaveric Pilot Study. Asian journal of neurosurgery. 2021 Jan-Mar;     [PubMed PMID: 34211869]

[34]

Lebl DR,Avrumova F,Abjornson C,Cammisa FP, Cervical Spine Navigation and Enabled Robotics: A New Frontier in Minimally Invasive Surgery. HSS journal : the musculoskeletal journal of Hospital for Special Surgery. 2021 Oct;     [PubMed PMID: 34539275]

[35]

Issa M,Kiening KL,Unterberg AW,Scherer M,Younsi A,Fedorko S,Oskouian RJ,Chapman JR,Ishak B, Morbidity and Mortality in Patients over 90 Years of Age Following Posterior Stabilization for Acute Traumatic Odontoid Type II Fractures: A Retrospective Study with a Mean Follow-Up of Three Years. Journal of clinical medicine. 2021 Aug 24     [PubMed PMID: 34501228]

[36]

Dou H,Xie C,Zhu S,Wang X,Huang Q,Zhou F, Feasibility analysis of the use of anterior screw fixation in the treatment of pediatric odontoid fracture. Translational pediatrics. 2021 Apr     [PubMed PMID: 34012844]

[37]

Watts A,Athanassacopoulos M,Breakwell L,Chiverton N,Cole A,Ivanov M,Tomlinson J, Management of C2 odontoid peg fragility fractures - A UK survey of spinal surgeons. Injury. 2022 Mar     [PubMed PMID: 34635337]

[38]

Rizvi SAM,Helseth E,Rønning P,Mirzamohammadi J,Harr ME,Brommeland T,Aarhus M,Høstmælingen CT,Ølstørn H,Rydning PNF,Mejlænder-Evjensvold M,Utheim NC,Linnerud H, Odontoid fractures: impact of age and comorbidities on surgical decision making. BMC surgery. 2020 Oct 14;     [PubMed PMID: 33054819]

[39]

Rizvi SAM,Helseth E,Harr ME,Mirzamohammadi J,Rønning P,Mejlænder-Evjensvold M,Linnerud H, Management and long-term outcome of type II acute odontoid fractures: a population-based consecutive series of 282 patients. The spine journal : official journal of the North American Spine Society. 2021 Apr     [PubMed PMID: 33346157]

[40]

Yamaguchi S,Park BJ,Takeda M,Mitsuhara T,Shimizu K,Chen PF,Woodroffe RW, Healing process of Type II odontoid fractures after C1-C2 posterior screw fixation: Predictive factors for pseudoarthrosis. Surgical neurology international. 2022     [PubMed PMID: 35509583]

[41]

Ricciardi L,Trungu S,Scerrati A,De Bonis P,Rustemi O,Mazzetto M,Lofrese G,Cultrera F,Barrey CY,Di Bartolomeo A,Piazza A,Miscusi M,Raco A, Odontoid screw placement for Anderson type II odontoid fractures: how do duration from injury to surgery and clinical and radiological factors influence the union rate? A multicenter retrospective study. Journal of neurosurgery. Spine. 2020 Oct 2     [PubMed PMID: 33007754]

[42]

Patkar S, Unstable odontoid fractures: technical appraisal of anterior extrapharyangeal open reduction internal fixation for irreducible unstable odontoid fractures. Patient series. Journal of neurosurgery. Case lessons. 2021 Nov 15     [PubMed PMID: 36061093]

[43]

Maeda K,Ichiba T, Unusual Clinical Course of Odontoid Fracture: Transient Prehospital Cardiopulmonary Arrest. Cureus. 2020 Dec 18;     [PubMed PMID: 33489569]

[44]

Zygogiannis K,Georgoulis JD,Antonopoulos SI,Gourtzelidis G,Chatzikomninos I, Cruciate Paralysis Following a Displaced Type II Odontoid Fracture: A Case Report. Cureus. 2022 May     [PubMed PMID: 35747018]

[45]

Agunbiade S,Belton PJ,Mesfin FB, Spinal Cord Transection in a Type II Odontoid Fracture From a Ground-Level Fall. Cureus. 2020 Dec 28     [PubMed PMID: 33520537]