Neurosurgery notes/Spine/Deformity/Thoracic and lumbar deformity

Thoracic and lumbar deformity

View Details
logo
Parent item
Deformity
Sub-item
Scoliosis
Kyphosis
Adjacent segment disease
 

Positioning

  • Aim
    • Adequate exposure to the surgical site.
    • Passive spinal column correction.
    • Minimise the risk of associated pressure-related injuries to the patient.
  • Common Positions and Historical Context:
    • Prone most common
      • Historical descriptions of the prone position, such as the "tuck, knee-chest, and praying position," were associated with high rates of complications.
        • Vascular injury
        • Peripheral nerve injury
        • Muscle necrosis → acute kidney injury
    • Other position Supine and lateral
  • Advancements in Positioning Equipment:
    • Modern frames
      • has significantly reduced complications.
      • Designed to:
        • Pad bony prominences.
        • Maintain physiological positioning of the limbs.
        • Reduce intra-abdominal and intra-ocular pressure.
        • Play a vital role in inducing lordosis or kyphosis on the native spine, depending on surgical goals.
      • Studies on frame impact:
        • Hastings, Andrews, and four-poster frames were reported to cause a 50% reduction in overall lumbar lordosis compared to preoperative standing alignment.
        • OSI Jackson surgical table
            • Introduced in 1992
            • Has ability to generate lordosis.
            • A dual-column design, allowing for an
              • Unrestricted abdomen
              • 360 degrees of rotation
              • Complete radiolucency
                •  
            notion image
  • Leg positioning
    • Influences spinal lordosis and kyphosis
      • Placing legs in a sling allows for relative hip flexion, which can facilitate decreasing lumbar lordosis.
      • Placing legs on flat boards with pillows will extend the hips, thereby inducing lumbar lordosis.
  • Risks and Complications of Improper Patient Positioning:

      • Perioperative Peripheral Nerve Injury (PPNI):

      • Risk of peripheral nerve damage:
        • Patient factors
          • Medical conditions – diabetes, smoking, high blood pressure, vascular disease.
          • Being male.
          • Increasing age.
          • Being very overweight or extremely thin.
        • Surgical factors
          • More complicated operations which involve more instruments are more likely to damage nerves than simpler operations.
          • Certain operations, including:
            • Operations on the spine or brain
            • Cardiac or vascular operations (on the heart or major blood vessels)
            • Operations on the neck or parotid (a gland in the face)
            • Some kinds of breast operation
            • Operations in which a tourniquet (a tight band around a limb) is used to reduce bleeding.
          • Positioning
            • Prone
            • Lateral
      • Typically presents as
        • Neuropraxia or
        • Axonotmesis.
      • Lower Extremity Injuries:
        • Patients with significant fixed sagittal malalignment can sustain various lower extremity nerve compressions, such
          • As quadriceps palsy, even with appropriate padding, which can be relieved by appropriate recognition and interventions.
      • Upper Extremity Injuries:
        • Brachial Plexus
          • Highly susceptible to stretch injuries due to its fixation at the cervical and axillary fascia and its traversal through bony architecture (clavicle, first rib, humeral head).
          • Risk factor
            • Abduction of the arm greater than 90° (Greatest risk)
            • Extension, external rotation plus abduction of the arm
            • Rotation plus lateral flexion of the neck in the ipsilateral direction
            • Application of shoulder braces.
        • The most common clinical presentation is a motor deficit, with the majority of cases resolving over time.
      • Specific Peripheral Neuropathies:
        • Ulnar nerve palsy
          • Increased risk with
            • Elbow flexion greater than 90°
              • Most vulnerable peripheral nerve in the upper extremity to brachial artery ischemia.
            • Direct pressure to the cubital tunnel
              • Obesity and preoperative cubital tunnel syndrome are identified risk factors for ulnar nerve injury.
            • Malpositioning of a blood pressure cuff
        • Lateral femoral cutaneous neuropathy (meralgia paresthetica)
          • Reported in up to 24% of patients undergoing prone spinal surgery.
          • This is believed to be caused by direct compression of the nerve by the pelvic bolsters near the anterior superior iliac spine.

      Post-Operative Vision Loss (POVL):

      • Occurs in 0.03%.
      • Due to
        • Ischemic optic neuropathy
        • Central artery occlusion
        • Ischemic orbital compartment syndrome
        • Occipital cerebral infarction.
      • Proposed pathogenesis involves increased orbital venous and intraocular pressure due to external pressure during surgery.
      • Risk factors include:
        • Prolonged operative time.
        • Intraoperative anaemia.
        • Hypotension.
        • High-volume infusions.
        • Trendelenburg position.
        • Rotation of the head.
        • Applied ventral pressure, which may compromise blood flow to the optic nerve.
      • Mitigation strategies:
        • Routine use of a skull clamp
          • (e.g., Gardner-Wells tongs, halo, or Mayfield)
          • For long-segment spinal deformity surgery in some institutions.
          • Pros
            • Not applying external pressure to the orbit compared to horseshoe and foam headrests.
            • Unobstructed visualisation of the face
            • Controlled positioning of the cervical spine
            • Facilitate surgical exposure.

Instrumentation

  • Rod Constructs
    • Two-rod constructs
      • Standard of Care for many years
      • Cons:
        • When extensive spinal destabilisation occurs intraoperatively, particularly with 3-column osteotomies (3CO), there have been high rates of rod failure with standard two-rod constructs.
    • Multi-Rod Constructs (MRCs):
      • Pros
        • Lower rate of implant failure
          • Merril 2017 found that MRCs significantly reduce the risk of rod breakage.
        • Reduced need for revision surgery
      • Triple or "quad" rod techniques (3 to 4 iliac screws)
        • Has become more popular over the last decade, even for non-3CO constructs.
        • The "four-rod" technique, first described by Shen et al., has demonstrated biomechanical superiority compared to traditional two-rod constructs.
          • However, this technique is technically challenging due to the need for pedicle screw placement at different angles throughout the construct.
        • Most surgeons now utilise MRC's when performing 3CO's in the thoracic or lumbar spine for ASD patients.
      • Long-term studies are still needed to determine the ideal rod configuration and whether supplemental rods influence fusion rates in these constructs.
  • Starting and ending fusion level
    • If L5/S1 shows degeneration (disc) → include pelvis in the fusion

Osteotomies in ASD Surgery

Deformity correction techniques

Outcomes

  • Shin 2025:
    • The risk factors with the higher OR for medical complications were
      • Frailty (OR: 4.4, 95% CI: 2.0-9.9),
      • ASA class 4 (OR: 3.58, 95% CI: 2.00-6.39),
      • Male sex (OR: 3.52, 95% CI: 1.78-6.96)
      • Malnutrition (OR: 2.89, 95% CI: 1.69-4.93), and pathologic weight loss (OR: 2.38, 95% CI: 2.01-2.81).
    • The risk factors with the higher OR for mortality were
      • Liver disease (OR: 36.09, 95% CI: 16.16-80.59),
      • Pathologic weight loss (OR: 7.28, 95% CI: 4.36-12.14),
      • Renal failure (OR: 5.51, 95% CI: 2.57-11.82),
      • Chronic heart failure (OR: 5.67, 95% CI: 3.3-9.73)
      • Age over 65 (OR: 3.49, 95% CI: 2.31-5.29).