Under general endotracheal anesthesia, the patient is positioned prone on padded chest rolls, rolled blanket bolsters, or a Wilson spinal frame to provide adequate cushioning for the chest and abdomen while allowing vacant space under these areas (thereby promoting epidural venous drainage and adequate pulmonary exchange). The operating table (or Wilson frame) is slightiy flexed, thereby widening the thoracic interlaminar and interpedicular spaces. The knees are placed in 30 degrees of flexion, and support stockings are used to promote venous drainage. Soft foam padding is placed at all pressure points, and special care is taken to avoid pressure on the lateral femoral cutaneous and common peroneal nerves. The head is turned sideways on a foam cushion, with special caution to prevent compression upon the globes. The arms are positioned upward in a relaxed manner with slight shoulder and elbow flexion (care is taken to avoid any traction on the brachial plexus). Padding is placed under the elbows to protect the ulnar nerves in the olecranon grooves. The breasts and genitalia are carefully checked for undue pressure points.

Caution: Appropriate additional support of the patient should be provided so that a small amount of lateral tilt in the operating table away from the surgeon may safely be applied at any point during the procedure. In addition, it is important that the anesthetist be prepared to inflate the lung should the pleura be inadvertently compromised.

The spinous processes, transverse processes, and associated posterior rib tubercles provide helpful superficial landmarks for localization. Using a fingernail (or a marking pen), the surgeon gently indents (or marks) the skin to delineate the intended spinous processes and associated transverse processes and rib tubercles.

Note that heads of the 1st, 11th, and 12th ribs articulate only with their own vertebra whereas the heads of all the other ribs possess two facets and articulate with their own vertebra and the one above (i.e., the 8th rib articulates with both the T7 and T8 vertebrae and crosses the T7–T8 disc space) (Fig. 45.3).

An appropriate Betadine skin prep is applied, and 1 g cephalosporin (or when indicated by hypersensitivity, 80 mg gentamicin) is administered intravenously. An 18-gauge spinal needle is inserted off the midline at the suspected appropriate interspinous space, and a lateral radiograph is obtained to confirm the deeper levels of anatomy; this permits the skin incision to be precisely located in relation to the surgical pathology and overlying bony elements. A large percentage of thoracic disc protrusions occur along the lower four thoracic disc spaces (easy to localize); the middle third of the thoracic spine ranks next in frequency; clinically relevant herniations in the upper thoracic spine (where radiographic confirmation of level is often tedious) are fortunately quite rare.

A midline or paramedian incision (3–5 cm in length) centered at the level of the appropriate disc space is utilized medial to or along the paravertebral muscle mass. A symptomatic disc is approached from the side of lateralizing signs or symptoms or from the site of greatest protrusion. In the absence of such indications, a left-sided approach (for the right-handed surgeon) is employed.

Once the incision is made, hemostasis is obtained with bipolar coagulation. A small self-retaining retractor is placed, and the subcutaneous tissues are incised with electrocautery.