A new model to facilitate palpation of the level of the transverse processes of the thoracic spine

Study Design: Nonexperimental, normative research design. Objectives: To test a proposed model to locate the level of the transverse processes (TPs) of the thoracic spine through surface palpation. Background: Palpation of the TPs of the thoracic spine is challenging because of their depth relative to the more superficial structures of the spine. Many clinicians use the more superficial spinous processes (SPs) of the thoracic spine to orient themselves for palpation of the TPs. In 1979, Mitchell described a "rule of threes," which attempted to predict the location of the level of the thoracic TPs relative to their corresponding SPs. We previously conducted a pilot study to investigate the validity of the rule of threes and concluded that it is not an accurate predictor of the level of the location of the TPs of the thoracic spine. Based on that previous work, we hypothesized that a more accurate model for predicting the level of the TPs would be that they are generally at the level of the SP of the adjacent cranial thoracic vertebra throughout the thoracic spine. Methods and Measures: We dissected 15 cadavers and measured the vertical distance between the transverse (horizontal) plane of the TPs of 1 vertebra and the SP of the adjacent cranial thoracic vertebra for all levels of the thoracic spine. Results: Mean vertical distances ranged from 2.0 to 4.0 mm. The means for all thoracic vertebral levels except for T11 and T12 were significantly less than the normal 6-mm threshold of 2-point discrimination of the fingertips (P<.01). Conclusion: The results of this study indicate that the TPs of each thoracic vertebra are generally at the level of the SP of the vertebra 1 level above, throughout the thoracic spine. It may be more difficult to predict the location of the TPs of the 2 most caudal levels (T11 and T12), given their greater variability of position.