Radiological Definitions of Sagittal Plane Segmental Instability in the Degenerative Lumbar Spine - A Systematic...

Area of Science:

• Orthopedics
• Neurosurgery
• Radiology

Background:

• Lumbar spinal stenosis (LSS) and lumbar degenerative spondylolisthesis (LDS) are common conditions often associated with segmental instability.
• Defining segmental instability is crucial for diagnosis and treatment planning in spinal surgery.
• Existing definitions and measurement thresholds vary significantly across studies.

Purpose of the Study:

• To systematically collect and categorize definitions of segmental instability in surgical studies of LSS and LDS.
• To analyze the frequency of different definitions and imaging measurement thresholds.
• To compare thresholds used in patient studies with those from biomechanical studies and studies of healthy individuals.

Main Methods:

• A systematic review adhering to PRISMA guidelines was conducted.
• Included clinical and biomechanical studies on adult patients with LDS/LSS undergoing surgical treatment with diagnostic imaging data.
• Data synthesis involved tabulation and narrative synthesis following independent review by two researchers.

Main Results:

• 118 studies were included; 69% were surgical intervention studies.
• Definitions of segmental instability were grouped, with dynamic sagittal translation (24%) and dynamic translation with angulation (26%) being most common.
• Narrative definitions were more frequent in non-interventional studies of healthy populations.

Conclusions:

• Despite historical lack of consensus, a radiological definition for segmental instability in the degenerative lumbar spine is proposed.
• The consensus definition identified is greater than 3 mm of dynamic sagittal translation.