Important Concepts

Thoracic disc herniations account for a minority of the disc herniations evaluated by a spine surgeon. This reflects the relative immobility of the thoracic spine as compared with the cervical and lumbar regions and thus the low incidence of degenerative changes. Contemporary series suggest that thoracic herniated discs represent less than 1% of all symptomatic discs and, accordingly, represent less than 1% of all disc operations.¹ This establishes an incidence of 1 symptomatic patient per 1 million individuals per year.^2–4

The majority of thoracic herniated discs are asymptomatic. As many as 37% of patients harbor an asymptomatic herniated thoracic disc as defined on randomly sampled magnetic resonance imaging (MRI) scans.⁵ More conservative estimates propose this number lies in the range of 10% to 15%.^1,6,7

The majority of symptomatic discs are found in the lower third of the thoracic region, with most being found between the T8 and T11 levels.^1,7 Discs in the upper third of the thoracic spine are rare. Herniated discs in the thoracic spine commonly occur centrally within the canal (77% to 94%) and are often calcified (22% to 65%).^1,8 A small but very important 6% to 7% of discs prove to be intradural.⁹

Symptomatic thoracic herniated discs manifest with a wide array of findings. Stillerman and colleagues⁸ presented an exhaustive review of their personal findings in 71 patients with thoracic disc disease as well as a meta-analysis of 13 series encompassing 247 patients (Table 159-1). Both of these surveys demonstrated that sensory changes were seen in more than 60% of cases. Pain was a finding in greater than half of the patients but was actually more likely to be axial than the typically presumed radicular pattern. Motor weakness and spasticity or hyperreflexia were present in 55% to 58% of patients. As with many cervicothoracic lesions, bowel and bladder dysfunction was one of the least-common symptoms, appearing in only 24% to 35% of patients.⁸

Table 159-1 Comparison of the Present Study and Earlier Thoracic Disc Series

NR, not reported.

∗ Number resolved or improved/total number of patients in groups reporting this result.

From Stillerman CB, Chen TC, Couldwell WT, et al: Experience in the surgical management of 82 symptomatic herniated thoracic discs and review of the literature. J Neurosurg 88:623-633, 1998.

The radiographic identification of these lesions is obviously most commonly performed with MRI. MRI allows visualization of the disc herniation and the surrounding neural elements (Fig. 159-1). However, computed tomography/myelography remains a viable imaging technique with excellent resolution of the affected region, despite the inconvenience and invasiveness of the procedure. Plain computed tomography scanning also serves a supportive role because it often assists MRI in evaluating whether a given disc is calcified and offers a better analysis of the bony anatomy (Fig. 159-2).

FIGURE 159-1 Sagittal T2-weighted magnetic resonance imaging demonstrates a thoracic herniated disc and associated syrinx.

FIGURE 159-2 Axial computed tomography scan of same patient demonstrates calcification of the herniated disc.

Selecting patients for surgery is much like selection for degenerative processes afflicting the remainder of the spine. That is, the indications for surgery are by no means objectified and established but rather are physician defined. As with most cervical lesions, myelopathy with or without bowel or bladder involvement is a nearly absolute operative indication. Surgical treatment of thoracic herniated discs for radiculopathy, back pain, or sensory changes is much more difficult to uniformly define. The natural history of thoracic disc herniations is not completely understood. Brown and colleagues¹⁰ followed 40 patients with symptomatic thoracic disc herniations and determined that 77% returned to work symptom free without surgical intervention. Therefore, an argument can be made to manage patients who do not have significant neurologic insult (weakness, spasticity) in a fashion similar to those with degenerative cervical and lumbar conditions. These nonoperative measures can include a combination of rest, physical therapy, oral antiinflammatory medication (steroidal and/or nonsteroidal), and/or steroid injections.

If a patient has myelopathy or nonmyelopathic symptoms not amenable to conservative measures, surgical intervention may be necessary. At this point, a surgeon must decide on an operative approach. Again, a wide variety of techniques may be used for thoracic disc herniations, each method possessing its own advantages and compromises.

One of the reasons for the development of this variety of procedures is the surgical constraint of the thoracic spine anatomy. In this region, the spinal cord lies within the relatively narrow thoracic spinal canal and the thecal sac cannot be manipulated as freely as within the lumbar region. Therefore, the operative approach needs to minimize manipulation of the dura and spinal cord. Although this feature is similar to the cervical region, the anterior approaches to the thoracic region (excluding the very superior thoracic spine) are more involved than standard anterior cervical procedures. Thus the ideal procedure would afford the surgeon a ventral view of the region while maintaining the more straightforward technical aspect of a posterior approach. As a result of these requirements, more-aggressive posterior procedures have been developed in attempts to gain greater “anterior” perspectives and circumvent the need for more-involved anterior thoracic exposures.

Considerations for an operative approach for herniated thoracic discs include the following:

Although not inclusive, the following guidelines can be made in terms of operative approaches.

Posterior approaches can be employed at any level. Their utility depends largely on the laterality of the disc; that is, the more lateral the disc, the more accessible and successful a posterior approach might prove. The one caveat is that a standard posterior laminectomy is not an adequate approach for any thoracic disc herniation. Laminectomies for thoracic disc herniations have been repeatedly shown to carry unacceptable rates of morbidity. Excepting a truly foraminal herniated disc or a case of isolated stenosis from thoracic spondylosis (and not a disc herniation), the laminectomy should not be used. Rather, standard posterior approaches include the transpedicular, Stillerman’s transfacet pedicle sparing, transcostovertebral, costotransversectomy, and lateral extracavitary. In that order, these procedures offer gradually increasing exposures toward the midline of the canal despite the incursion of increasingly larger and more destructive incisions and dissections. Unfortunately, no posterior approach allows a true ventral view of the spinal canal and dura. Therefore, features favoring a posterior approach include more laterally located discs, soft discs without evidence of calcification, and extradural lesions. Often these approaches are better tolerated by the patient than anterior approaches, making them more attractive in patients with comorbidities, especially in regard to pulmonary disease. Last, the anatomy encountered by the surgeon in these procedures is very familiar, and mastery of even the more aggressive posterior procedures is usually quickly attained by most surgeons.

Anterior approaches (transsternal and transmanubrial, transthoracic, anterolateral and retropleural) can be used selectively at varying levels. The transmanubrial and transsternal approach is best suited for superior thoracic lesions above T4 (below this level, the aortic arch and associated veins become an obstacle). Below T4, anterior approaches are either transthoracic or retropleural. All the anterior approaches afford the surgeon a more direct view of the ventral dura and disc herniation. This allows greater ease in managing calcified or intradural herniations. Central discs are also more directly accessed through these approaches. The downside of these operations is usually a more substantial operative event for the patient, requiring a greater period of recovery and the contraindication in patients with significant comorbidities. Multiple disc herniations need to be within one or two levels of one another to be accessed ventrally. The surgical approach and anatomy are somewhat foreign to most neurosurgeons and require focused training and repetitive procedures to maintain proficiency. This can be somewhat overcome by cardiothoracic surgeons aiding in the exposure of these regions, but the neurosurgeon must still manage the bony dissection, which is not as familiar to many surgeons as the anatomy encountered in typical posterior spinal procedures.

Intraoperative Localization

Although radiographic localization is often taken for granted in the cervical and lumbar regions, it poses a significant hurdle in the thoracic spine. Lower thoracic levels can often be imaged with standard lateral radiographs. However, in some larger patients and certainly in mid- to upper thoracic regions, lateral radiographs are very difficult to interpret and have no reference with which to localize appropriate levels.

First, a surgeon needs to identify the level of a herniated disc using the same method by which the preoperative level is identified. That is, if the preoperative investigations identify the affected thoracic level counting down from C1, then the surgeon should not necessarily use the sacrum as a reference point intraoperatively, because a lumbarized sacral segment could obviously cause an error in localization. Rather, the surgeon can employ an intraoperative anteroposterior (AP) radiograph and count down from the first thoracic ribs, or the sacrum can be used to count upward, if this has been confirmed as an accurate means of reference. A preoperative localization can be easily performed by taping a radiopaque marker to the patient and obtaining a standard AP radiograph (Fig. 159-3).

FIGURE 159-3 Preoperative anteroposterior radiograph for localizing the incision.

Lateral radiographs are of limited utility in the thoracic spine, and AP radiographs must often be used to adequately visualize spinal elements and levels. The surgeon has the option to prepare the operating table for the insertion of AP radiograph cassettes or to use a radiolucent operating table with intraoperative fluoroscopy. Either option is effective, but exclusively lateral thoracic radiographs can prove to be very difficult to interpret.

Description of Individual Procedures

Posterior Procedures

Transpedicular

The transpedicular approach is perhaps the most commonly considered procedure for a thoracic disc herniation. Its origins date to the initial description of Patterson and Arbit¹¹ in 1978, which represent a modification of Carson’s¹² 1971 technique. The transpedicular approach allows the surgeon relatively straightforward access into the most lateral region of the spinal canal ventral to the spinal cord (Fig. 159-4). The patient is placed in a prone position on gel rolls or a Wilson frame, and a vertical midline incision is centered over the level of interest. Sharp dissection is carried deeply to the thoracodorsal fascia. A unilateral exposure can be performed to minimize trauma to the contralateral paravertebral musculature. Once through the thoracodorsal fascia, a subperiosteal dissection is performed with Cobb elevators until the lateral facets are exposed on the affected side.

FIGURE 159-4 Schematic demonstrates the region of bone removal in the transpedicular approach.

(From Fessler RG, Sturgill M: Review: Complications of surgery for thoracic disc disease. Surg Neurol 49:609-618, 1998.)

Viewing the facet joints, the surgeon needs to then develop an idea as to the location of the pedicle and the associated nerve root. The thoracic pedicle to be drilled is centered 1 to 2 mm beneath the edge of the inferior facet of the superior vertebra (Fig. 159-5). For example, a for a T7–8 disc herniation the surgeon will aim to drill the T8 pedicle, which is centered just below the inferior edge of the T7 inferior facet.

FIGURE 159-5 Transpedicular approach after drilling of facet and superior pedicle.

(From Kumar R, Dunsker SB: Surgical management of thoracic disc herniations. In Schmidek HH, Sweet WH (eds): Operative Neurosurgical Techniques, 4th ed. New York: WB Saunders, 2000, pp 2122-2131.)

By using a combination of the pneumatic drill and Kerrison rongeurs (generally no larger than 2 mm), a lateral laminotomy is performed to visualize the lateral edge of the thecal sac. This visualization allows the surgeon to safely proceed with further bone resection. The removal of bone is then extended laterally to the medial facet joint and ventral pedicle. Once the dorsal aspect of the facet is drilled adequately to visualize the exiting nerve root, the axis of the pedicle can be discerned. At this point, the interior of the pedicle is drilled, allowing the superior and medial cortex to act as a protective barrier against the nerve root and thecal sac, respectively. Often this drilling is undertaken with the aid of the operating microscope. Once the drilling has been performed to the depth of the disc space or vertebral body, a curet may be used to fracture and remove the remaining cortical shell of the pedicle, being careful to fracture the remnant pedicle away from the dura.

The increased lateral exposure obtained by removing the superomedial pedicle allows the surgeon to view a portion of the lateral disc space and spinal canal tangentially under the nerve root and thecal sac. The lateral aspect of the herniated disc is then incised and disc material is removed from centrally within the disc space. This allows the surgeon to displace more-medial herniated tissue into the disc space (the force being directed away from the spinal cord) using a down-biting curet. Once this is completed, the disc fragments can be removed safely without disturbing the dura.

Closure resembles that of posterior lumbar and cervical procedures.

Transfacet Pedicle Sparing

This technique shares many similarities with the transpedicular approach but avoids the resection of the pedicle. Devised by Stillerman and colleagues,¹³ the technique employs a setup similar to that used in the transpedicular technique. The patient is positioned prone. Stillerman and colleagues recommend the use of AP fluoroscopy to verify the proper level during the exposure. A linear midline incision is used, and the standard dissection and subperiosteal exposure is performed so as to expose the ipsilateral facet joint.

At this point, the proper disc level and overlying facet joint are verified with fluoroscopy. As with the transpedicular procedure, a pneumatic drill is used to penetrate the medial aspect of the facet joint. Unlike the previous procedure, the inferiorly lying pedicle is not entered with the drill. Once the surgeon reaches neural foramen, blunt dissection may be performed to visualize the disc space lying at the inferior aspect of the foramen (Fig. 159-6). The exiting nerve root is usually found in the extreme superior aspect of the foramen and therefore is often not encountered (except in the higher thoracic spine). Once the annulus is identified, the disc removal proceeds in a fashion similar to that of any of the other posterior procedures.

FIGURE 159-6 Sequential views of the transfacet pedicle-sparing procedure illustrate facet drilling, identification of nerve root and disc material, and removal of disc herniation.

(From Stillerman CB, Chen TC, Diaz Day J, et al: The transfacet pedicle-sparing approach for thoracic disc removal: Cadaveric morphometric analysis and preliminary clinical experience. J Neurosurg 83:971-976, 1995.)

Transcostovertebral Approach

Another, more recent posterolateral approach has been described by Dinh and colleagues,³ in which only the posterior cortex of the rib head is removed, thus allowing an increased lateral exposure while not incurring the potential disadvantages of complete rib resection. In this procedure, the patient is once again positioned on the operating table in a prone position. A midline incision is used, typically spanning the adjacent superior and inferior disc spaces. A standard subperiosteal dissection is performed, but the exposure is extended laterally to visualize the transverse process. At this point, the transverse process is removed to reveal the underlying rib head. Using a diamond-tipped drill, the lateral one half of the facet joint and the upper one third to one half of the pedicle are removed (Fig. 159-7). This allows visualization of the spinal cord and exiting nerve root. Further ventral drilling is performed through the posterior cortex of the rib head until the annulus is identified medially. The authors emphasize that the key to this procedure is “staying within the costovertebral joint and drilling outward circumferentially to include immediate adjacent structures such as the posterior cortex of the rib head and the lateral endplates above and below the annulus.”³ Once the annulus is exposed, the disc can be removed in the standard fashion by central decompression of the disc and removal of the herniation via the newly formed central cavity.

FIGURE 159-7 Transcostovertebral approach demonstrates intended region of bone removal (dashed lines) and resultant exposure of the lateral annulus.

(From Dinh DH, Tompkins J, Clark SB: Transcostovertebral approach for thoracic disc herniations. J Neurosurg 94:38-44, 2001.)

The advantages of this procedure are the increased lateral exposure to the disc space while leaving the ventral portion of the rib and, consequently, the pleura. Inspection for violation into the thoracic cavity is performed before closure, but generally no chest tube is required.

Early during their experience, the authors noted a postoperative radiculopathy that appeared in several patients when the nerve root was maintained. Their recommendation is now to transect the nerve root proximal to the ganglion to prevent this occurrence. In doing so, the authors have not noted any adverse complications.

Costotransversectomy

The next progression in terms of a greater lateral exposure through a posterior incision is the costotransversectomy. Recognition has been awarded to both Hulme and Menard for the development of this procedure.^9,14

This technique offers a more lateral working corridor than the transpedicular route and hence affords a better view of the anterior spinal canal (Fig. 159-8). To do so, the costotransversectomy requires a more extensive muscular and bony dissection, often leading to more postoperative discomfort.

FIGURE 159-8 Bone removal in costotransversectomy procedure.

(From Fessler RG, Sturgill M: Review: Complications of surgery for thoracic disc disease. Surg Neurol 49:609-618, 1998.)

The patient may be positioned in a variety of ways, ranging from prone to a partial lateral position. Skin incisions for this approach have also varied, ranging from curvilinear (convexity toward midline) to straight paramedian. Generally, these incisions are much longer than their transpedicular counterparts, spanning two to three segments above and below the affected region.

The skin and muscle (trapezius, erector spinae) layers are reflected medially to allow visualization of the ribs and transverse processes. The bony resection begins by identifying the adjoining rib to the lower vertebral body (e.g., rib 8 for a T7–8 disc). The rib is then dissected free of investing fascia and pleura. A Cobb or periosteal elevator can be used to initiate this procedure, but Doyen dissectors are generally used to complete the bulk of the dissection. The rib is then disarticulated and removed with rongeurs from the costotransverse and costovertebral joints. Additionally, the corresponding transverse process should be resected.

Anatomic landmarks at this point include the corresponding pedicle, the neurovascular bundles of the resected rib and superior rib, and the underlying pleura. The pleura can be retracted ventrally under a malleable retractor. Attention is next turned to drilling the pedicle just inferior to the affected disc space. This allows identification of the lateral thecal sac and the exiting nerve root. The herniated disc is then visualized from its inferior aspect, where it is incised laterally for removal. As in the transpedicular approach, the lateral herniated disc is initially removed, followed by removal of the central nucleus pulposus. Once a cavity has been created within the disc, the more medial herniated material is carefully mobilized from the canal into the center of the disc space. The herniated disc can then be removed safely with pituitary rongeurs.

Closure requires inspection of the pleura for violations into the thoracic cavity. The operative site is flooded with irrigation under positive-pressure ventilation. Small tears can be closed with sutures. Larger tears require closure and the placement of a chest tube.

Lateral Extracavitary

The term lateral extracavitary approach was first coined by Larson and colleagues¹⁵ in 1976 for a technique for treating traumatic thoracic spine injuries. However, this was a modification of Capener’s¹⁶ 1954 technique for treating tuberculous spondylitis.¹⁷

The lateral extracavitary approach represents the most aggressive posterior approach. It therefore offers the greatest visualization of the anterior canal via a posterior incision but requires a much more significant dissection than a transpedicular approach. The “lateral” nomenclature should not fool one into believing that the entirety of the anterior dura is as well visualized as in anterolateral procedures. This procedure is still a posterior approach, despite its lateral viewing corridor.

This procedure typically uses one of two incisions: a hockey-stick incision with the vertical segment centered over the affected level or a curvilinear incision with the convexity facing medially. The major difference between the lateral extracavitary approach and the costotransversectomy is that a larger lateral resection of the inferior rib is performed (Fig. 159-9). This allows a lower viewing angle toward the canal. If a hemilaminectomy is performed, the nerve root overlying the disc space can be ligated, incised, and then used to rotate the thecal sac dorsally. The disc material is removed in the same manner as the preceding techniques. If necessary, portions of the vertebral body can be drilled to facilitate disc manipulation. If this is performed, then portions of resected rib can be placed as strut grafts between the vertebral bodies.

FIGURE 159-9 Bone removal in the lateral extracavitary approach. Note the larger amount of rib to be resected as compared with the costotransversectomy.

(From Fessler RG, Sturgill M: Review: Complications of surgery for thoracic disc disease. Surg Neurol 49:609-618, 1998.)

Closure is performed in a manner similar to that for costotransversectomy.

Transthoracic Procedure (Adapted from Vollmer and Simmons²⁰)

A curvilinear incision is made from the posterior angle of the rib to several centimeters beyond the anterior axillary line. The decision as to which rib to dissect can be clarified by obtaining a preoperative AP chest radiograph and drawing a line directly lateral to the affected disc space. This line intersects the rib directly lateral to this region, offering the most direct exposure. Typically, this tends to be the lower associated rib in the upper and midthoracic spine, whereas in the lower thoracic spine, often the 10th rib is adequate for discectomies. Muscles are divided with electrocautery. Once the subscapular space has been entered, the surgeon can verify the appropriate level by reaching superiorly, palpating the first rib, and then counting downward. A second AP radiograph provides added confirmation of the level. Cobb and Doyen elevators are used to perform a subperiosteal dissection of the rib, which can then be removed and used later for bone grafting, if necessary. The neurovascular bundle is identified and traced to the neural foramen. After the rib is removed, the pleural cavity is sharply entered. A rib spreader is then inserted to provide additional exposure within the thoracic cavity.

Once the appropriate level is identified by these methods, the lung is retracted and deflated. The parietal pleura is incised longitudinally, extending over adjacent vertebral bodies, and a subperiosteal dissection performed until the disc space and vertebral bodies are well visualized. Care is taken to preserve the intersegmental vessels running at the midportions of the vertebral bodies. The sympathetic chain is then mobilized away from the vertebral bodies in a dorsal direction. The intercostal nerve is dissected from the pleura and used to identify the location of the neural foramen and pedicle.

The rib head is removed with rongeurs, drills, or both. Resection of the rib allows access to the posterolateral aspect of the disc and the intervertebral foramen. At this point, the surgeon needs to identify the disc margins, the intervertebral foramen, and the pedicles above each foramen. The pedicle inferior to the desired disc space can be drilled away with a diamond-tipped drill to allow greater visualization of the exiting nerve root and thecal sac. Because of the typically narrow thoracic disc spaces, the posterolateral portions of the vertebral bodies might need to be drilled away to adequately access the disc space itself. Larger and more centrally located disc herniations often require more aggressive drilling, in some cases even extending beyond the midpoint of the ventral spinal canal (Fig. 159-10). Exposure of this portion of the disc allows an incision to be made in the lateral annulus. Using curets, the dorsal herniation can then be manipulated into the cavity created by the initial disc removal. This portion of the procedure can be performed under loupe magnification, although the operating microscope allows superior magnification and illumination.

FIGURE 159-10 Bone removal employed in the transthoracic procedure.

(From Fessler RG, Sturgill M: Review: Complications of surgery for thoracic disc disease. Surg Neurol 49:609-618, 1998.)

Often after decompression, notable bleeding from epidural veins is encountered. This is usually easily dealt with by using a combination of gentle tamponade with hemostatic agents (Gelfoam or the equivalent) and/or bipolar electrocautery at lower settings. In most instances, no graft is required unless the bone removed from the vertebral bodies is significant.

Retropleural Thoracotomy

Although the transthoracic approach offers a clear visualization of the thoracic spinal canal, it carries the inherent complications of entering the thoracic cavity. McCormick²¹ introduced the retropleural approach as an alternative means of ventrolateral access to the spine.

Positioning is similar to that of the transthoracic procedure. The patient is placed in a lateral position on a beanbag, preferably with the lesion lying directly over a break in the operating table. The incision is slightly smaller than in the transthoracic procedure. In the midthoracic spine, the incision is placed over the rib of interest, extending from several centimeters off midline to the posterior axillary line. Higher thoracic lesions necessitate a hockey-stick incision, and lower thoracic lesions are best approached by making an incision over the 10th rib (Fig. 159-11).

FIGURE 159-11 Incisions for the retropleural thoracotomy in the upper (A), mid- (B), and lower (C) thoracic regions.

(From McCormick PC: Retropleural approach to the thoracic and thoracolumbar spine. Neurosurgery 37:908-914, 1995.)

Again, the muscular dissection remains similar to the transthoracic procedure. The inferior rib of the affected level is dissected free from investing fascia. An 8- to 10-cm segment of rib is removed, leaving the proximal portion still attached to the transverse process and vertebral body.

Once this portion of the rib is removed, the endothoracic fascia is identified. This layer of tissue encompasses the entire thoracic cavity and the parietal pleura. By incising this fascia along the longitudinal axis of the recently removed rib, the parietal pleura is exposed (Fig. 159-12). Using blunt dissection, the parietal pleura can be gently dissected free from the inner aspect of the fascia toward the spine. When necessary, the remaining portion of rib can be disarticulated and removed to allow additional exposure. A malleable retractor is placed over the parietal pleura to prevent entrance into the thoracic cavity and to facilitate the exposure of the disc space.

FIGURE 159-12 Incision of the endothoracic fascia, allowing exposure of the pleura.

(From McCormick PC: Retropleural approach to the thoracic and thoracolumbar spine. Neurosurgery 37:908-914, 1995.)

The periosteum and investing tissues are then dissected off the vertebral body. The neural foramen is identified, along with the pedicle and the superiorly lying disc space. At this point, disc space manipulation remains the same as in the transthoracic procedure. The end plates and pedicle are removed via a pneumatic drill (Fig. 159-13). Closure is also the same, being sure to check for tears in the parietal pleura and closing these with sutures as needed. A chest tube is generally not needed unless a large tear in the pleura is encountered.

FIGURE 159-13 Drilling of the end plates and pedicles in a transthoracic or retropleural thoracotomy.

(From McCormick PC: Retropleural approach to the thoracic and thoracolumbar spine. Neurosurgery 37:908-914, 1995.)

Transsternal Approach to Thoracic Spine (T1-5)

The transsternal approach affords access to the upper thoracic spine, from T1 to T4–5. The lower limit of this approach depends on individual anatomic variability as defined by the level of the aortic arch, which allows only minimal manipulation.

An orogastric tube can be placed in the esophagus to improve intraoperative identification of this structure. Several incisions can be used to perform this procedure including a midline T-shaped incision or a vertical incision over the sternal region, which curves to one side or another as it extends superiorly into the lower cervical region. The upper portion of the dissection is similar to that of an anterior cervical procedure. Fascial attachments to the sternum are removed, and the surgeon can insert a finger to bluntly dissect along the underside of the sternum. The sternum is then opened with a sagittal saw, whereupon a sternal retractor is placed. At this point, the major vessels are identified, along with the pericardium and thymus. The inferior thyroid artery and vein can be ligated for additional exposure.²² The thymus is reflected to the patient’s right side, affording a window of operative exposure just medial to the left common carotid artery.⁹ Disc manipulation is then carried out in the fashion similar to that of anterior cervical surgery. In addition to the vascular and neurologic structures, care must be taken to avoid injury to the thoracic duct, which ascends along the esophagus and eventually runs behind the left subclavian artery to enter the internal jugular vein.

Fortunately, the demand for transsternal surgery is low, owing to the infrequency of upper thoracic herniated discs and the posterior procedures generally offering access with less morbidity. In the few cases requiring a transsternal approach, assistance by cardiothoracic surgeons is often invaluable.

Complications

Since the abandonment of laminectomy for thoracic disc herniations, morbidity and mortality rates have dropped significantly.² Obviously, the type of complication differs with the specific procedure, because pneumonia and hemo- and chylothorax are more commonly seen after a transthoracic procedure than after a transpedicular procedure. Again, complications of some procedures may be accepted outcomes in others. For example, a pleural tear is an undesirable outcome during a costotransversectomy, but a pleural incision is intentionally performed in a transthoracic procedure.

Despite these difficulties in comparing the complication rates, the morbidity and mortality associated with currently accepted procedures appear similar.^2,23 Fessler and Sturgill² demonstrated that since 1986, reported complication rates for all thoracic disc surgeries ranged from 8% to 16%. When analyzed with respect to procedure, morbidity rates were 9% for transpedicular, 12% for costotransversectomy, 12% for lateral extracavitary, and 11% for transthoracic procedures. No mortality was noted.

Infection rates ranged from 1% to 3%, which compare favorably with those of other spinal surgeries.² Neurologic worsening was seen in approximately 1% of cases.^2,9

In regard to the newer procedures mentioned in this chapter, reports of the transfacet pedicle-sparing procedure of Stillerman and colleagues¹³ and the transcostovertebral approach of Dinh and colleagues³ mentioned no complications in the their analyses of 6 and 22 patients, respectively.

Conclusion

Most neurosurgeons encounter symptomatic thoracic disc herniations from time to time in their practices. Successful management of these lesions requires a thorough understanding of the spectrum of available procedures.