Questioning the anatomical relationship between the seventh thoracic vertebra and the inferior angle of scapula: a radiographic review to inform anaesthesia practice.

Aim: Blockade of thoracic dermatomes for anaesthesia and analgesia relies on accurate identification of spinal level. For many practitioners this is achieved by using the classical relationship between the inferior angle of scapula (IAS) and the spinous process of the seventh thoracic vertebra. There is mounting published evidence to suggest that this relationship is not a reliable one.

Methods: 100 departmental radiographs in posterior-anterior projection were reviewed by a radiologist. Exclusion criteria included age = 20 years and spinal pathology.

Results: We found that the T7-IAS relationship was not a reliable one, and that anatomical variation exists as a function of age and gender. T8 is the most frequent level corresponding to the IAS in the study population and in males, with the T8/9 interspace the most frequent in females. The T7/8 interspace is the most frequent in the third decade descending to T8/9 in the seventh.

Discussion: For accurate identification of the correct vertebral level we suggest techniques such as ultrasound or fluoroscopic guidance rather than clinical examination and historical anatomical associations.