The Lasegue test: Defining its specificity and sensitivity based on geometry

Area of Science:

• Orthopedics
• Neurosurgery
• Radiology

Background:

• The Lasegue test, or straight leg raise test, is a common diagnostic tool for lumbar disc herniation.
• Its diagnostic accuracy can be influenced by the herniated disc's geometry and location.

Purpose of the Study:

• To investigate the relationship between herniated disc dimensions (apical and basal size) and Lasegue test results.
• To determine the specificity and sensitivity of the Lasegue test based on herniated disc height, location, and size.

Main Methods:

• Analysis of 865 cases with diagnosed lumbar disc herniation and available MRI scans and Lasegue test results.
• Calculation of radix length to the foramen using apical and basal lengths of the herniated disc.
• Recording of herniated disc level and apical direction to assess test specificity and sensitivity.

Main Results:

• Apical length of the herniated disc was the most critical factor influencing Lasegue test outcomes.
• The Lasegue test demonstrated the highest sensitivity and specificity for lateral herniated discs at the L4-5 level.
• Decreased specificity and sensitivity, with potential for false negatives, were observed in L3-4, migrated, and sequestered disc herniations.

Conclusions:

• The Lasegue test's diagnostic performance is geometrically explainable and influenced by herniated disc characteristics.
• Understanding factors affecting specificity and sensitivity, such as disc size and location, is crucial for accurate diagnosis and avoiding false results.