Ito The Thoracic And Lumbar Spine

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Vincent J. Devlin, MD

1. Describe the options for patient positioning for posterior surgical approaches to the thoracic and lumbar spinal regions.

Typically patients are positioned prone on a radiolucent operative frame for posterior approaches to the thoracic and lumbar spine. An exception is the use of a lateral decubitus position during simultaneous anterior and posterior surgical procedures.

2. What are the basic types of positioning frames for posterior spinal procedures?

• Four-post frame: Proximal pads are placed beneath the pectoral region and distal pads are placed in the region of the anterior superior iliac spines. The hip joints and lower extremities are positioned parallel with the trunk. Spine-specific operating room tables are available, which incorporate this design (e.g. Jackson spinal table)

• Wilson frame: Longitudinal curved pads are attached to a frame, which can be raised or lowered to alter lumbar lordosis

• Knee-chest frame: The patient's hips and knees are positioned at 90° and the patient's abdominal and lower extremity mass is supported by the patient's knees

3. Discuss major considerations for selecting the appropriate positioning frame for a specific spinal procedure.

A four-post frame design is preferred for multilevel fusion procedures. This type of frame permits extension of the hips and thighs, which preserves or enhances lumbar lordosis. Use of a frame that decreases lumbar lordosis (Wilson frame, knee-chest frame) is preferred for lumbar discectomy procedures. Decreasing lumbar lordosis facilitates access to the lumbar spinal canal as the distance between the spinous processes and lamina is increased. Care is necessary when positioning a patient for spinal stenosis decompressions. Spinal stenosis patients are symptomatic in extension. Positioning such patients on a frame that decreases lumbar lordosis and flexes the spine may result in failure to fully appreciate the extent of neural decompression required to relieve symptoms.

4. Outline the steps involved in a midline posterior exposure of the thoracic and lumbar spine.

• Incise the skin and subcutaneous tissues with a scalpel

• Place Weitlander and cerebellar retractors to tamponade superficial bleeding by exerting tension on surrounding tissues

• Electrocautery dissection is carried out down to the level of the spinous processes

• Cobb elevators and electrocautery are used to elevate the paraspinous muscles from the lamina at the level(s) requiring exposure. This provides sufficient exposure for discectomy and laminectomy procedures

• If a fusion is planned, Cobb elevators and electrocautery are used to elevate the paraspinous muscles laterally to the tips of the transverse processes on each side. Subsequently the facet joints are excised and prepared for fusion. Care is taken to preserve the soft tissue structures (interspinous ligaments, supraspinous ligaments and facet capsules) at the transition between fused and nonfused levels

• Hemostasis is maintained by coagulating bleeding points with electrocautery and packing with surgical sponges

5. Where are blood vessels encountered during posterior spinal exposures?

The arterial blood supply of the posterior thoracic and lumbar spine is consistent at each spinal level (Fig. 27-1). Arteries are encountered at the lateral border of the pars interarticularis, the upper medial border of the transverse process, and the intertransverse region. Sacral arteries exit from the dorsal sacral foramen. The superior gluteal artery enters the gluteal musculature and may be encountered during iliac crest bone grafting.

6. What methods are used to guide the surgeon in exposing the correct anatomic levels during a posterior approach to the thoracic or lumbar spine?

A combination of methods is used to guide exposure of correct anatomic levels:

• Preoperative radiographs are reviewed to determine bony landmarks and presence of anatomic variants that may affect numbering of spinal levels (i.e. altered number of rib-bearing thoracic vertebra, lumbarized or sacralized vertebra)

Figure 27-1. Blood vessels encountered during posterior midline approach. (From Wiesel SW, Weinstein JN, Herkowitz H, et al, editors. The Lumbar Spine. 2nd ed. Philadelphia: Saunders; 1996.)

Figure 27-1. Blood vessels encountered during posterior midline approach. (From Wiesel SW, Weinstein JN, Herkowitz H, et al, editors. The Lumbar Spine. 2nd ed. Philadelphia: Saunders; 1996.)

• Intraoperative osseous landmarks are referenced: C7 (vertebra prominens), T8 (inferomedial angle of the scapula), T12 (most distal palpable rib), L4-L5 (superior lateral edge of ilium)

• An intraoperative radiograph with a metallic marker at the level of exposure is obtained. A permanent copy should be made to document the correct level of exposure for every procedure

7. How is the location of the thoracic pedicle identified from the posterior midline

The thoracic pedicle is located at the intersection of the pars interarticularis and the proximal third of the transverse process just lateral to the midpoint of the superior articular process. The exact location of the pedicle at each thoracic level varies slightly. A rongeur or power burr is used to remove the outer bony cortex and expose the entry site to the pedicle.

8. How is the location of the lumbar pedicle identified from the posterior midline approach?

The lumbar pedicle is located at the intersection of two lines. The vertical line passes along the lateral aspect of the superior articular process and passes lateral to the pars interarticularis. The horizontal line passes through the middle of the transverse process, where it joins the superior articular process.

9. What is a thoracic transpedicular approach?

After the spine is exposed by a posterior midline approach, the thoracic pedicle can be used as a pathway to access anterior spinal column pathology. This approach is most commonly used for non-calcified disc herniations located lateral to the spinal cord. The facet joint at the level and side of the disc herniation is resected. The superior aspect of the pedicle below the herniation is removed with a motorized burr. Sufficient working room is created for removal of disc material. This approach is also useful for vertebral biopsy.

10. What is a costotransversectomy approach?

A costotransversectomy approach is a posterolateral approach to the thoracic spine (Fig. 27-2). It provides unilateral access to the posterior spinal elements, lateral aspect of the vertebral body, and anterior aspect of the spinal canal without the need to enter the thoracic cavity. Exposure includes resection of the posteromedial portion of the rib and transverse process. This approach was initially developed for drainage of tuberculous abscesses. It remains useful for approach?

Paraspinal mu:

Trapezius muscle

Paraspinal mu:

Trapezius muscle

Segments of transverse process and rib to be removed

Figure 27-2. Costotransversectomy approach. (From Winter RB, Lonstein JE, Dennis F, Smith MD, editors. Atlas of Spine Surgery. Philadelphia: Saunders; 1995.)

biopsies and disc excision (lateral and paracentral disc herniations) in patients who cannot tolerate a formal thoracotomy. It does not provide sufficient exposure of the ventral spinal canal to permit removal of central disc herniations or placement of an anterior strut graft/cage.

11. What is a lateral extracavitary approach?

A lateral extracavitary approach is a posterolateral extrapleural approach to the thoracic spine and thoracolumbar junction (Fig. 27-3). It provides greater exposure of the anterior spinal column and anterior aspect of the spinal canal than is achieved with a costotransversectomy. This approach requires removal of portions of the rib, costotransverse joint, facet, and pedicle. The exposure achieved is sufficient to permit removal of central disc herniations, corpectomy, and placement of an anterior strut graft or cage. This approach is usually combined with posterior segmental spinal instrumentation and fusion as this approach results in significant spinal instability.

12. Describe the paraspinal approach to the lumbar spine.

The paraspinal (Wiltse) approach is a posterolateral approach to the lumbar region (Fig. 27-4). It utilizes the plane between the multifidus and longissimus muscles. It permits direct access to disc herniations and spinal stenosis located in the extraforaminal zone without the need to resect the pars interarticularis or facet complex. It is also a useful approach for lumbar intertransverse fusion and instrumentation procedures.

Figure 27-3. Lateral extracavitary approach. (From Amundson GM, Gartin SR. Posterior spinal instrumentation for thoracolumbar tumor and trauma reconstruction. Semin Spine Surg 1997;9:262.)
Figure 27-4. Lumbar paraspinal approach. (From Zindrick MR, Selby D. Lumbar spine fusion: different types and indications. In Wiesel SW, Weinstein JN, Herkowitz H, et al, editors. The Lumbar Spine. 2nd ed, vol. 1. Philadelphia: Saunders; 1996. p. 609.)

13. What is a PLIF approach?

Posterior lumbar interbody fusion (PLIF) refers to placement of intracolumnar implant(s) into a lumbar disc space from a posterior approach (Fig. 27-5). The disc space must be prepared to receive the interbody devices. Steps involved in this process include laminectomy, discectomy, restoration of disc space height, and decortication of the vertebral endplates. One interbody device is generally placed on each side of the disc space, and posterior pedicle instrumentation is used to stabilize the spinal segment.

Figure 27-5. Posterior lumbar interbody fusion (PLIF). (From Zindrick MR, Wiltse LL, Rauschning W. Disc herniations lateral to the intervertebral foramen. In White AH, Rothman RH, Ray CD, editors. Lumbar Spine Surgery: Techniques and Complications. St. Louis: Mosby; 1987. p. 204.)

14. What is a TLIF approach?

Transforaminal lumbar interbody fusion (TLIF) refers to placement of intracolumnar implant(s) into a lumbar disc space through a unilateral posterior approach (Fig. 27-6). Unilateral removal of the pars interarticularis and facet complex provides posterolateral access to the disc space. This technique minimizes the need for significant retraction of neural elements and preserves the contralateral facet complex. The working space is sufficient to permit placement of two interbody fusion devices or a single large device through a unilateral approach. Posterior pedicle instrumentation is used to stabilize the spine segment.

15. What is a vertebral column resection?

A vertebral column resection (VCR) is a procedure to treat severe rigid spinal deformity. Using modern techniques, VCR can be performed entirely from a posterior approach in appropriate cases. The procedure involves removal of one or more spinal segments including the spinous process, lamina, transverse processes, pedicles, cephalad and caudad intervertebral discs, and vertebral body. When the resection is performed at a thoracic spinal level, rib resection is also required. Placement of temporary screw-rod fixation prior to osseous resection is critical to prevent neurologic injury during the procedure. Following the resection, the deformity is corrected by shortening the spinal column. An intervertebral cage is often placed into the anterior column defect to serve as a fulcrum for deformity correction and to prevent excessive spinal column shortening. The procedure is associated with significant neurologic risk and intraoperative neurophysiologic monitoring is mandatory.

Key Points

1. Posterior approaches to the thoracic and lumbar spine are extremely versatile and permit posterior decompression, fusion, and instrumentation from T1 to the sacrum.

2. Modern surgical techniques permit circumferential decompression and fusion of the thoracic and lumbar spine utilizing a single-stage posterior approach.


Posterior lumbar fusion approaches: Vertebral column resection:


1. Harms J, Tabasso G, editors. Instrumented Spinal Surgery: Principles and Technique. New York: Thieme Verlag; 1999.

2. Steffee AD, Sitkowski DJ. Posterior Lumbar Interbody Fusion and Plates. Clin Orthop 1988;227:99-102.

3. Vaccaro AR, Baron EM, editors. Operative Techniques: Spine Surgery. Philadelphia: Saunders; 2008.

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