The sacral tubercle--a cause for hot spots on bone scan

Area of Science:

• Nuclear medicine
• Radiology
• Anatomy

Background:

• The sacral tubercle (S1 posterior spinous process) can exhibit high intensity on bone scans.
• This finding occurs in approximately 4% of normal adult males.
• Anatomical variations, including sexual dimorphism, can affect sacrum appearance on scans.

Purpose of the Study:

• To describe the normal anatomy of the sacrum relevant to bone scan interpretation.
• To elucidate potential causes of false-positive and false-negative readings in sacroiliac joint imaging.
• To present diagnostic methods for sacral pathology.

Main Methods:

• Review of normal sacral anatomy on posterior bone scans.
• Analysis of potential pitfalls in interpreting sacroiliac joint and sacral intensities.
• Development of a diagnostic algorithm for sacral disease.

Main Results:

• The sacral tubercle can be mistaken for sacroiliac joint pathology.
• Sexual differences in sacral anatomy can lead to misinterpretations.
• Incorrectly assuming constant sacral intensity can cause false-negative results in sacroiliac disease assessment.

Conclusions:

• Normal sacral anatomy, particularly the sacral tubercle, is crucial for accurate bone scan interpretation.
• Awareness of anatomical variations prevents false-positive diagnoses of sacroiliac joint disease.
• A systematic approach is necessary to diagnose sacral conditions and avoid misinterpretation of sacroiliac joint scans.