The courses of the C8 and thoracic medial branch nerves are described in the introduction of Chapter 22 and demonstrated in Chapter 22D . Thoracic medial branch nerve radiofrequency (RF) neurolysis is indicated for the treatment of axial thoracic (i.e., midback) pain that typically originates from zygapophysial (i.e., facet) joint sprains, contusions, or osteoarthritis. This procedure is performed via a posterior approach. The RF electrode tip is placed at the superolateral edge of the transverse process in an oblique manner so that the tip bisects the superolateral edge.

Thoracic zygapophysial joint pain relief must first be confirmed through positive controlled diagnostic medial branch nerve blocks (see Chapter 22B ) before considering RF neurolysis. Two medial branch nerves must be lesioned to denervate a thoracic zygapophysial joint. For example, the T5 and T6 medial branch nerves must be denervated to treat pain that originates from the T6-T7 zygapophysial joint.

This chapter will focus on the RF electrode placement for C8 and thoracic medial branch neurolysis. As discussed in Chapter 22B and demonstrated in 22D, the medial branch nerve locations in association to the transverse process vary anatomically, depending on the thoracic level.

The variability of the medial branch nerve location is greatest in the midthoracic spine region (i.e., T4-T8) ( Fig. 22D.1 ). An injection of a phenol solution has been used to create medial branch chemical neurolysis. ² Although there is a lack of supportive evidence in the literature, phenol injection has been used either alone or in combination with RF to denervate medial branch nerves, especially those with variable location such as T4-T8. For C8 and T1-T10 RF, the electrode is placed more obliquely (medial to lateral) and more parallel to the nerve than the trajectory for thoracic medial branch injections. This facilitates a larger area for neurolysis. Ipsilateral oblique views are recommended for the T11 and T12 medial branch nerves because their locations are similar to those of the lumbar medial branch nerves.

A, Fluoroscopic image of a trajectory view with the radiofrequency needle position aligned with the left T7 transverse process so that the tip bisects the superolateral edge of the transverse process. The radiofrequency electrode overlies the left T6 medial branch nerve. B, Radiopaque structures, trajectory view. C, Radiolucent structures, trajectory view.

The needle is placed with the use of a fluoroscopic trajectory view along the medial branch nerves, confirming the needle tip position and depth in the anteroposterior (AP) and lateral views prior to denervation. Ipsilateral oblique views are also recommended for the T11 and T12 medial branch nerves because their locations are similar to those of the lumbar medial branch nerves.