Validity of the Rule of Threes and Anatomical Relationships in the Thoracic Spine.

Context: The location of the more superficial thoracic spinous processes is used to help osteopathic physicians locate the deeper and more difficult-to-palpate thoracic transverse processes. In 1979, Mitchell et al proposed the thoracic rule of threes to describe the relationship of the spinous processes to the transverse processes in the thoracic spine. This rule is currently taught at osteopathic medical schools.