Posterolateral Approach in the Oblique Position

Following the technique previously reported (1,5,6), the thoracic vertebras from T2 to T12 can be reached, under single-plane fluoroscopic, a C-arm or CT-scan guidance, via an oblique, posterolateral, intercostal approach at an angle of 35° from the patient's sagittal plane (Fig. 9). A coaxial trephine needle is used (Table 2). Preoperative radiographs and CT or MRI help to determine the side of the approach. The presence of a paravertebral abscess or mass facilitates the puncture. Depending on the target of the biopsy (vertebral body or disc space) and the spinal level, the needle should be oriented in a cephalad or caudad direction (Figs. 10 and 11). Using single-plane fluoroscopic guidance, the patient is placed in a 35° prone-oblique position (Fig. 12). With C-arm guidance, the C-arm can be titled 35° obliquely, which prevents the patient from turning. The

FIGURE 10 Changes in angle of approach that must be made for various vertebral levels.

FIGURE 11 Shaded and striped areas shows portions of disc and vertebras that can be reached through an intervertebral approach. As an example, the T-7 and T-8 vertebras and the intervening intervertebral disc are shown.

puncture point is located at the level of the lesion, 4.5 cm from the midline (5,6). A radiopaque mark is placed at this point, and a radiograph is made in this position. The vertebral body or disc lesion can be reached through a "puncture area" whose upper and lower borders are the heads of the ribs, posterior border is the anterior margin of the zygoapophyseal joint, and anterior border is the vertebral body or pleura (Fig. 13). The spinal canal and the pleural space can thus be avoided during the procedure. A 20-G needle is used to anesthetize the superficial planes, and the thin needle or guide of the trephine set is then introduced through a small skin incision. The needle is advanced under fluoroscopic guidance and is vertically oriented to the puncture area, following the direction of the gantry (Fig. 14). At the same time, the needle is used to anesthetize the deeper planes. The vertebral body or disc is usually reached at a depth of 6 cm (5,6). After checking the accurate placement of the needle tip, the thin needle is replaced by the trephine needle. Once the trephine needle abuts the lesion, the patient can be moved to a strict prone position. Two radiographs (a posteroanterior view and a cross-table lateral view) are obtained to check for the correct positioning of the trephine needle. Biopsies are then performed using the cutting cannula, and additional radiographs are obtained (Fig. 5). Pain is usually mild or absent. If there is severe pain, a technical error must be suspected.

FIGURE 12 Patient in 35° oblique procubitus position.

FIGURE 13 Diagram of anatomical relations in 35° oblique procubitus position. (1 ) Rib head, (2) costovertebral joint, (3 ) transverse process, (4 ) external edge of the articular process, (5 ) line of pleural reflection, (6) vertebral body, (7) contralateral lamina, (8 ) spinal canal. The puncture area is indicated by the dotted area.

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