Surgical Management of Odontoid Fractures and Upper Cervical Instability: Evidence-Based Trajectory for Optimal Fusion

Fractures of the odontoid process (the dens of the second cervical vertebra, C2) represent the most frequent cervical spine injury in elderly adults and account for roughly 10% to 15% of all cervical spine fractures overall. The atlantoaxial complex (C1–C2) provides more than 50% of total cervical rotational mobility, but this exceptional range of motion relies on a delicate balance between bone geometry and ligamentous restraints rather than intervertebral disc buffers.

When traumatic forces shear the odontoid peg, mechanical stability is immediately compromised. In younger patients, these injuries typically result from high-energy blunt trauma, such as motor vehicle collisions or sports impacts. In older adults with osteopenia or osteoporosis, however, an odontoid fracture often follows a seemingly trivial low-energy event—such as a fall from standing height with neck hyperextension.

Management of odontoid fractures requires nuanced decision-making. Historically, non-operative management with rigid external immobilization (such as halo-vest orthoses) carried unacceptably high morbidity and mortality in elderly populations, while traditional posterior fusions permanently sacrificed half of the patient’s neck rotation.

In South Florida, Dr. Evan Trapana is a fellowship-trained orthopedic spine surgeon and Assistant Professor of Orthopaedic Spine Surgery at the University of Miami Miller School of Medicine and UHealth Tower. Having completed his orthopedic surgery residency at UM/Jackson Memorial Hospital and advanced spine fellowship training at the University of California San Diego (UCSD) Medical Center, Dr. Trapana specializes in upper cervical spine trauma, minimally invasive stabilization, and complex spinal reconstruction. Leveraging real-time 3D navigation, anterior motion-preserving screw fixation, and posterior atlantoaxial fusion protocols, Dr. Trapana tailors treatment to bone mineral quality, fracture orientation, and the patient’s physiological reserve.

Classification: The Anderson and D’Alonzo Framework

The standard anatomical framework for evaluating odontoid fractures is the Anderson and D’Alonzo Classification, which stratifies injuries based on the anatomical level of the fracture line:

[ODONTOID FRACTURE CLASSIFICATION]

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├─► Type I: Tip Avulsion (Rare, Alar ligament insertion)

│ └─► Generally stable; treated conservatively with a rigid collar

│

├─► Type II: Fracture at the Waist / Base of the Dens

│ └─► HIGH NON-UNION RATE (Up to 30%–85% with conservative care)

│

└─► Type III: Fracture Extends into C2 Vertebral Body Cancellous Bone

└─► High vascularity; heals reliably in a rigid cervical collar (85%–90% union)

▲ [Dens Tip] ────────► Type I: Alar Ligament Avulsion

/ \

| | [Waist / Neck] ───► Type II: High Non-Union / Watershed Zone

|___|

/ \

| C2 | [Body Base] ────► Type III: Cancellous Extension into Body

\_______/

Why Type II Fractures Are Prone to Non-Union

Type II fractures occur through the narrow neck of the dens and present a persistent clinical challenge:

1. Watershed Microvascular Supply: The arterial supply of the dens ascends from the alar and apical arcade arteries above and the vertebral arteries below. Fractures through the waist interrupt this blood supply, creating localized ischemia.
2. Small Contact Surface Area: The narrow waist provides limited cortical surface area for bone bridging.
3. Synovial Fluid Exposure: The anterior and posterior aspects of the dens are bathed in synovial fluid from the atlantodens and transverse ligament articulations. Synovial fluid contains collagenases that actively inhibit osteoblast activity and biological callus formation.
4. Mechanical Shear: Rotational torque from C1 places continuous shear stress on the fracture plane.

The Decision Matrix: Motion Preservation vs. Posterior Fusion

When a Type II fracture demonstrates instability, displacement $> 5\text{ mm}$, angulation $> 10^\circ$, or presents in an older adult where prolonged bed rest or external bracing is dangerous, surgical stabilization is warranted:

[DISPLACED TYPE II ODONTOID FRACTURE]

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[ASSESS TRANSVERSE LIGAMENT & MORPHOLOGY]

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┌──────────────┴────────────────────────────────────────┐

▼ ▼

[INSPECT FRACTURE LINE & HABITUS] [ANTERIOR CONTRAINDICATIONS PRESENT]

│ │

├─► Fracture oblique: Anterior-superior ├─► Anterior-inferior oblique fracture

│ to posterior-inferior ├─► Chronic non-union (> 6 months)

├─► Intact transverse atlantal ligament ├─► Disrupted transverse atlantal ligament

├─► Non-osteoporotic bone purchase ├─► Severe barrel-chest / short neck anatomy

├─► No severe cervicothoracic kyphosis └─► Severe osteoporotic bone failure

│ │

▼ ▼

[ANTERIOR ODONTOID SCREW FIXATION] [POSTERIOR C1–C2 ARTHRODESIS]

(Preserves >50% Cervical Rotation) (Harms / Goel-C1 Lateral Mass + C2 Pedicle/Pars)

1. Anterior Odontoid Screw Fixation: Preserving Rotational Kinematics

For acute, reducible fractures in suitable candidates, direct anterior screw osteosynthesis represents the definitive motion-preserving intervention:

[Supine Head-Extended Positioning under Dual Biplanar Fluoroscopy]

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▼

[Anterior Retropharyngeal Approach via C5–C6 Transverse Neck Crease]

│

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[Working Corridor Medial to Carotid Sheath, Lateral to Trachea/Esophagus]

│

▼

[K-Wire Trajectory Drill across Anterior-Inferior C2 Body into Dens Tip]

│

▼

[Cannulated Herbert-Type Lag Screw Compresses Fracture Line]

• Preserving Range of Motion: Unlike posterior procedures that fuse C1 to C2, anterior screw fixation heals the bone while keeping the atlantoaxial joint intact. The patient preserves the ~50% of global neck rotation mediated by the C1–C2 joint.
• Lag Screw Compression: A headless, partially threaded cannulated compression screw crosses from the anterior-inferior lip of the C2 body, traverses the fracture gap, and anchors into the dense cortical tip of the dens. Tightening the lag screw draws the fragments together under dynamic compression, promoting primary bone healing.
• Anatomical Prerequisites: The fracture line must slope from anterior-superior to posterior-inferior (or be purely horizontal). If the fracture slopes anterior-inferior, driving a screw forward simply displaces the dens posteriorly into the spinal cord.

2. Posterior Atlantoaxial Fusion (The Harms / Goel Protocol)

When the fracture line is comminuted, chronicity exceeds several months, bone mineral density is poor, or the transverse atlantal ligament is torn (Dickman Type I injury), anterior screw fixation carries an unacceptably high risk of failure.

In these scenarios, Posterior C1–C2 Fusion using C1 Lateral Mass and C2 Pedicle/Pars Screws (Harms-Goel technique) provides rigid three-column biomechanical stabilization:

[Prone Rigid Mayfield Skull Pin Fixation]

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▼

[Targeted Posterior Midline Suboccipital Exposure (C1 Arch & C2 Lamina)]

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[Navigation-Guided Screw Trajectory]

├─► C1: Polyaxial screws placed into bilateral C1 Lateral Masses

└─► C2: High-purchase screws into C2 Pedicles, Pars, or Translaminar corridors

│

▼

[Rigid Connecting Rods & Structural Autologous Bone Graft Placement]

• Immediate Mechanical Rigidity: Rigid screw-and-rod constructs provide immediate multi-planar stability, eliminating the need for cumbersome postoperative halo vests or hard cervical collars.
• High Fusion Success Rate: With decortication of the C1–C2 facet joints and placement of autologous bone graft between the arches, posterior fusion achieves bony union rates exceeding 95% to 98%, even in elderly and osteoporotic populations.
• Motion Trade-Off: The C1–C2 joint is permanently immobilized. While subaxial cervical motion (C2–C7) accommodates flexion and extension, the patient loses approximately 40 to 45 degrees of horizontal neck rotation to either side.

Comparative Overview: Treatment Pathways for Type II Odontoid Fractures

Managing the Geriatric Odontoid Fracture

The management of odontoid fractures in patients over the age of 65 requires special attention:

• The Danger of Halo Braces: Halo-vest immobilization in elderly patients is associated with cardiopulmonary compromise, aspiration pneumonia, dysphagia, and a mortality rate approaching 20% to 30%.
• Modern Surgical Philosophy: Dr. Trapana favors internal fixation over prolonged external immobilization. By surgically stabilizing the atlantoaxial complex—either via anterior lag screw or posterior Harms instrumentation—elderly patients can sit up, mobilize out of bed on postoperative day one, and avoid pulmonary atelectasis and deconditioning.

Conclusion

Upper cervical spine trauma and odontoid fractures demand nuanced management to balance bony union against long-term mobility. By offering both motion-preserving anterior odontoid screw fixation and rigid posterior atlantoaxial reconstruction, Dr. Evan Trapana tailors surgical care to the fracture morphology and the patient’s individual lifestyle and recovery goals.

• Surgeon: Dr. Evan Trapana, MD
• Academic Role: Assistant Professor of Orthopaedic Spine Surgery, University of Miami Miller School of Medicine
• Clinical Specialization: Upper Cervical Spine Trauma, Motion-Preserving Spine Surgery, Complex Cervical/Lumbar Reconstruction, Minimally Invasive Spine Surgery (MISS)
• Primary Practice Locations:
  • UHealth Tower (University of Miami Hospital): 1400 NW 12th Ave, Suite 2, Miami, FL 33136
  • UHealth at Coral Gables: 5555 Ponce de Leon Blvd, Coral Gables, FL 33146
• Appointments & Consultations: (305) 243-3000 / (305) 689-4979