What is the management and treatment of posterior ligament injuries of the spine?

Management and Treatment of Posterior Ligament Injuries of the Spine

Posterior ligamentous complex (PLC) injuries require surgical stabilization when disrupted, as they render the spine unstable and carry high risk for neurological compromise and progressive deformity. 1

Critical Role of the Posterior Ligamentous Complex

The PLC is the primary stabilizing structure of the spine, consisting of the supraspinous ligament, interspinous ligament, ligamentum flavum, and facet joint capsules. 2, 1 The ligamentum flavum provides the greatest mechanical resistance to spinal motion, followed by the articular capsules, interspinous ligament, and supraspinous ligament. 3

PLC integrity is one of three critical factors that determine surgical decision-making in thoracolumbar spine trauma, alongside injury morphology and neurological status. 1 When the PLC is disrupted, the spine becomes unstable regardless of the fracture pattern, necessitating surgical intervention. 2, 1

Diagnostic Approach

Imaging Strategy

MRI without contrast is the mandatory imaging modality for evaluating suspected PLC injury, as it directly visualizes soft tissue structures and has superior sensitivity and specificity compared to other modalities. 4, 5

• Fat-suppressed T2-weighted sequences are essential for detecting PLC disruption, showing high signal intensity in injured ligaments. 6
• Plain radiographs and CT scanning can suggest PLC injury indirectly through findings like widened interspinous distance, facet joint dislocation, or vertebral body translation, but they frequently miss isolated ligamentous injuries. 4, 2, 6
• MRI influences surgical decision-making in up to 25% of cases by revealing PLC integrity status. 7

Clinical Indicators of PLC Injury

Look specifically for:

• Palpable gap between spinous processes on physical examination 2
• Visible bruising or swelling over the posterior spine 2
• Neurological deficits suggesting spinal instability 1
• Mechanism involving flexion-distraction forces (most common cause) 6

Injury Patterns and Associated Fractures

PLC injury occurs in 53% of all thoracolumbar trauma patients, with varying frequency depending on fracture type: 6

• 100% of dislocation fractures have PLC disruption 6
• 63% of flexion-distraction injuries involve PLC tears 6
• 42% of burst fractures have associated PLC injury 6
• 26% of compression fractures demonstrate PLC disruption 6

This high prevalence in "stable-appearing" fractures like burst and compression fractures underscores why MRI is mandatory when clinical suspicion exists. 6

Treatment Algorithm

Surgical Indications (Absolute)

Proceed with surgical stabilization when:

• PLC disruption is confirmed on MRI, regardless of fracture type 2, 1
• Neurological deficit is present with PLC injury 1
• Progressive kyphotic deformity develops 2
• Spinal instability is demonstrated on dynamic imaging 2

Surgical Approach Selection

The choice between anterior, posterior, or combined approach depends on:

1. Posterior-only approach is appropriate when:

   • PLC disruption is the primary pathology 1
   • Anterior column is relatively intact 1
   • No significant anterior compression requiring corpectomy 1

2. Combined anterior-posterior approach is indicated when:

   • Severe anterior column destruction coexists with PLC injury 1
   • Load-sharing classification score is 7-9 points 4
   • Significant kyphotic deformity requires anterior reconstruction 1

Surgical Techniques

Traditional fusion remains the standard for most PLC injuries, providing definitive stability. 2 However, temporary fixation without fusion is emerging for select patients with isolated PLC injuries and intact anterior/middle columns, allowing potential ligamentous healing. 2

Special Populations

Pediatric Considerations

In children, ligament injuries differ fundamentally from adults as pediatric ligaments are often stronger than growth plates. 8

• Immobilization should not exceed 10 days in pediatric ligament injuries, followed by functional treatment. 8
• Functional bracing is superior to compression bandages and easier to maintain than taping in children. 8
• Exercise therapy focusing on proprioception, strength, and coordination should begin immediately after the immobilization period. 8

Cervical Spine PLC Injuries

For cervical spine trauma with suspected ligamentous injury:

• MRI cervical spine without contrast is the definitive study 4
• Look specifically for injuries at the craniocervical junction (C1-C3) and cervicothoracic junction, where injuries are frequently concealed 4
• Fat-saturated T2 sequences are optimal for detecting soft-tissue injuries 4

Critical Pitfalls to Avoid

The most common error is missing PLC injuries in patients with "minor" compression or burst fractures, leading to delayed instability and neurological deterioration. 2, 6 Always obtain MRI when:

• Mechanism suggests flexion-distraction forces 6
• Physical examination reveals posterior tenderness or palpable gap 2
• Plain films show subtle widening of interspinous distance 6
• Any neurological symptoms are present 1

Do not rely on CT alone to clear the spine in unconscious or unreliable patients, as 25% of ligamentous injuries will be missed. 4 MRI is mandatory in this population. 4

Avoid prolonged conservative management once PLC disruption is confirmed, as this leads to progressive kyphosis and potential neurological compromise. 2 Surgical stabilization should proceed expeditiously. 2, 1