When are reduction pedicle screws recommended for use in spinal surgery?

Reduction Pedicle Screws in Spinal Surgery

Reduction pedicle screws are recommended for use in spinal surgery when there is preoperative evidence of spinal instability, kyphosis at the level of spondylolisthesis, or when iatrogenic instability is anticipated during the procedure. 1

Indications for Reduction Pedicle Screws

• Pedicle screw fixation should be considered as a treatment option in patients with lumbar stenosis and spondylolisthesis when there is preoperative evidence of spinal instability or kyphosis at the level of the spondylolisthesis 1
• Patients with preoperative lumbar kyphosis who undergo reduction and pedicle screw instrumentation-augmented fusion demonstrate better outcomes than those treated with noninstrumented fusion 1
• Pedicle screw fixation is particularly beneficial when extensive decompression is required, which may create iatrogenic instability 1

Evidence Supporting Pedicle Screw Fixation

• Class I medical evidence demonstrates that pedicle screw fixation significantly improves fusion success rates (83% with instrumentation vs. 45% without) 1, 2
• Pedicle screw fixation is recommended when posterolateral lumbar fusion is used to manage low-back pain in patients at high risk for pseudarthrosis 1
• The use of pedicle screws enhances fusion rates, although a positive correlation with clinical outcomes has not been consistently demonstrated 1

Specific Clinical Scenarios

• For patients with spondylolisthesis (any grade) with spinal stenosis, posterior lumbar fusion with pedicle screws is medically necessary 2
• In cases with evidence of instability (defined commonly as 5mm or more of spondylolisthesis), reduction pedicle screws provide improved structural support 2
• Patients with double major idiopathic scoliosis benefit from pedicle screw fixation on the convex portion of the lumbar spine, allowing for improved correction of the lumbar Cobb measurement, horizontalization and translation of the lowest instrumented vertebra 3

Technical Considerations

• Larger diameter screws (6.5mm) have shown superior coronal, sagittal, and rotational correction compared to standard screws (5.0-5.5mm) in adolescent idiopathic scoliosis patients 4
• Screws with more degrees of freedom (polyaxial and 6DOF screws) demonstrate lower bone-screw forces compared to monoaxial and uniaxial screws, which may be beneficial in patients with large and stiff spinal deformities or compromised bone quality 5
• The proper selection of patients for surgery is likely the most important factor associated with good outcomes when using pedicle screw fixation 6

Potential Complications and Considerations

• Complications of pedicle screw fixation can include screw malpositioning, dural lacerations, pedicle fractures, and deep wound infections 6
• When using a meticulous surgical technique, these complications can be minimized 6
• The use of an assistant surgeon is beneficial during complex spinal procedures involving instrumentation and hardware placement to maintain proper exposure, assist with retraction of neural elements, and help with hardware placement 7

Decision Algorithm for Reduction Pedicle Screws

1. Confirm diagnosis with appropriate imaging showing spondylolisthesis or other spinal instability 2
2. Assess for presence of:
   • Spinal stenosis with spondylolisthesis 2
   • Evidence of instability (dynamic motion on flexion/extension) 2
   • Preoperative kyphosis at the level of spondylolisthesis 1
   • Need for extensive decompression that may create iatrogenic instability 1
3. If any of these criteria are met, reduction pedicle screws are indicated 1, 2