What are the indications, surgical technique, and postoperative management for posterior cervical spine fixation?

Posterior Cervical Spine Fixation

Posterior cervical fixation is indicated for instability, multilevel stenosis with myelopathy, traumatic injuries with ligamentous disruption, failed anterior procedures, and cases requiring decompression with concurrent stabilization—with lateral mass screws being the primary fixation method for subaxial cervical spine (C3-7) and C1 lateral mass/C2 pars or pedicle screws for upper cervical pathology.

Indications for Posterior Fixation

Posterior cervical fixation should be performed in the following clinical scenarios:

• Traumatic instability: Cervical fracture-dislocations, facet injuries, and ligamentous disruptions requiring realignment and stabilization 1
• Multilevel cervical spondylotic myelopathy (CSM): When decompression of 3+ levels is needed, particularly with preserved or restorable lordosis 2, 3
• Post-laminectomy instability: Prevention of progressive kyphosis after extensive posterior decompression 2
• Rheumatoid arthritis and ankylosing spondylitis: When atlantoaxial or subaxial instability develops 4
• Failed anterior procedures: Pseudarthrosis, hardware failure, or inadequate decompression 4
• Epidural abscess with instability: Though posterior approaches carry higher infection risk, they allow circumferential decompression when combined with anterior debridement 5

Surgical Technique Selection

Upper Cervical Spine (C1-C2)

• C1 lateral mass screws: Use the notching technique with entry point 3-4mm from posterior arch midline, directed 10-15° medially 6
• C2 fixation options: Pars screws (safer, lower vertebral artery risk) or pedicle screws (stronger biomechanically but higher neurovascular risk) 7, 6
• C2 translaminar screws: Alternative when pars or pedicle anatomy is unfavorable 6

Subaxial Cervical Spine (C3-7)

Lateral mass screw fixation is the workhorse technique for C3-7 posterior stabilization 7, 4:

• Entry point: Center of lateral mass, 1mm medial to midpoint
• Trajectory: 10-15° lateral, 25-30° cephalad (Magerl technique) or 30° lateral, 15° cephalad (Anderson technique)
• Screw length: Typically 14-16mm
• Avoid medial angulation >15° (risks nerve root injury) and avoid lateral angulation <10° (risks vertebral artery injury)

Cervical pedicle screws provide superior biomechanical stability but require:

• Preoperative CT to assess pedicle diameter (minimum 4.5mm)
• Computer-assisted navigation strongly recommended given 2-3mm pedicle diameter and proximity to vertebral artery 6
• Reserved for revision cases, severe osteoporosis, or when lateral mass bone stock is inadequate 7

Instrumentation Considerations

• Titanium constructs are preferred: Biologically inert with smooth surface that resists bacterial adherence 5
• Rod contouring: Must restore or maintain cervical lordosis; kyphotic alignment correlates with worse outcomes 2, 8
• Fusion substrate: Autograft from iliac crest or local bone is optimal; structural allograft acceptable but higher subsidence risk 5
• Bone morphogenic protein: No contraindication even in infection settings 5

Critical Technical Pitfalls

Avoid These Common Errors:

1. Excessive medial angulation of lateral mass screws: Causes nerve root injury—stay 10-15° lateral 7
2. Inadequate cephalad angulation: Risks facet joint violation and adjacent segment degeneration—maintain 25-30° 7
3. Operating on kyphotic spine with laminoplasty alone: Requires fusion to prevent progressive deformity 2, 3
4. Ventral epidural abscess decompression via posterior-only approach: High risk of cord injury; requires anterior debridement first 5
5. Placing hardware in active infection without adequate debridement: While titanium can be used in infection, complete corpectomy/discectomy of infected tissue is mandatory 5

Postoperative Management

Immobilization

• Hard cervical collar for 6-12 weeks if single-level fusion with good bone quality
• Halo vest for 8-12 weeks if multilevel fusion, poor bone quality, or upper cervical instrumentation
• No external immobilization if rigid segmental fixation achieved with lateral mass or pedicle screws in good bone stock

Imaging Surveillance

• Immediate postoperative CT: Confirm screw position and alignment 5, 6
• 6-week radiographs: Assess hardware position and early fusion
• 3-month CT: Evaluate fusion mass development
• 6-month and 1-year radiographs: Confirm solid arthrodesis and rule out adjacent segment degeneration

Complications to Monitor

Posterior approaches have inherently higher morbidity than anterior approaches 5:

• Wound complications: 15-20% infection/dehiscence risk due to muscle dissection and recumbent positioning 5
• C5 nerve palsy: 5-10% incidence after multilevel decompression, typically transient 9
• Hardware failure: 5-8% with wire fixation, <2% with modern screw-rod constructs 2
• Pseudarthrosis: 10-15% without instrumentation, 3-5% with rigid fixation 2, 8
• Progressive kyphosis: 24-40% after laminectomy without fusion vs 7-12% with fusion 2, 8

Functional Outcomes

Expected neurological recovery with posterior fixation for myelopathy: 55-60% improvement in Japanese Orthopaedic Association (JOA) scores, equivalent to anterior approaches or laminoplasty alone 2, 8, 3. Recovery is limited by:

• Symptom duration >18 months (worse outcomes)
• Severe preoperative myelopathy (JOA <8)
• Poorly controlled diabetes
• Age >70 years (conflicting evidence) 3

Fusion prevents late kyphotic deformity that occurs in 24-40% of laminectomy-alone patients, though functional outcomes at 3-5 years may be equivalent if deformity doesn't develop 2, 8.