Advantages and Disadvantages.

Although laminectomy is technically the simplest decompressive spinal operation, the only indication for its use in thoracic disc disease may be in the treatment of thoracic spondylosis.

Clinical Experience.

Black described a modified laminotomy/medial facet approach using a unilateral interlaminar laminotomy involving the superior and inferior laminar arches, as well as the medial 2 to 3 mm of the facet joint. The dural edge is exposed to establish boundaries for the cord, and an Epstein stomping curet is used to push the disc downward and away from the cord. This technique was used to remove 11 discs in seven patients. Effective treatment was reported; only one patient reported transient increased weakness compared with preoperative weakness. Coppes and colleagues reported removing 13 symptomatic central thoracic disc herniations using a posterior transdural approach. In these cases, a laminectomy is performed, the posterior dura is opened, the cord exposed, and the ventral dura is opened. Direct access to the thoracic disc is obtained, and it is removed. After the disc is removed, a piece of dural substitute is placed to repair the ventral defect, and the posterior dural opening closed with running sutures. The authors reported only one case of cerebrospinal fluid (CSF) leak.

Technique.

The patient is placed in the prone position and taped to the table to facilitate rotation away from the surgeon during the disc removal. The spinous process, lamina, and facet joints are exposed using a linear midline incision. Most of the facet joint is removed, as is the pedicle caudal to the disc space. The pedicle is drilled out flush with the vertebral body. A small cavity measuring 1.5 to 2 cm in depth is created in the vertebral body to enable depressing the overlying disc away from the ventral dura mater. Additionally, whenever necessary, hemilaminotomies are performed to visualize the dorsolateral dura mater.

Advantages.

This approach is considerably less invasive than most other operations for thoracic disc removal, particularly the transthoracic (TT) and the lateral extracavitary (LECA) approaches. Using this less invasive approach is thought to lessen perioperative pain, shorten hospital stays, and enable earlier return to premorbid activity. The surgery avoids problems associated with thoracotomy, rib resection, and extensive muscle dissection. Operating time and blood loss also appear to be less than with other surgeries.

Disadvantages.

Critics of this procedure point out the limited ability to visualize across the spinal canal, making decompression of the central and contralateral portions of the disc a relatively blind procedure. Sometimes, difficulty is encountered in managing calcified and intradural disc fragments. We believe that safety is enhanced by using specially designed thoracic microdiscectomy instrumentation ( Fig. 92-3 ) and endoscopic techniques. Although some report being able to remove intradural fragments and central, densely calcified discs using the dorsolateral techniques, we have not had success with these entities. Dense calcifications involving the dorsal margin of the disc space tend to adhere strongly to the ventral dura mater. The possibility of significant dural adherence may lead one to use one of the ventrolateral or lateral procedures in those situations.

A selection of the Manny-Mark Stillerman thoracic microdiscectomy instruments. These were developed to facilitate disc removal during a dorsolateral approach without damaging the medially situated spinal cord.

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

The final disadvantage of this procedure relates to the removal of the facet-pedicle complex, without the ability to place an interbody graft. It has been reported that patients operated on using the transpedicular approach have somewhat disappointing results from the standpoint of localized back pain. The desire to improve these results led to the development of the transfacet pedicle-sparing approach. It was postulated that the avoidance of pedicle removal should minimize postoperative back pain. The preliminary experience has suggested that this, in fact, may be the case.

Clinical Experience.

Bilsky reviewed 20 cases performed between 1982 and 1992 at New York Hospital in which the transpedicular approach was used for thoracic discs (lateral or centrolateral calcified or soft discs). No postoperative instrumentation was used for stabilization; however, no patient suffered from postoperative spinal instability-related pain or delayed kyphosis. Levi and associates published a contemporary series of 35 patients operated upon via a unilateral transpedicular approach. Good results were obtained in 15 patients, fair results in 11 patients, no improvement in 8 patients, and 1 patient was paraplegic after surgery. They also did not find evidence of clinical or radiographic instability. Chi and colleagues described a mini-open transpedicular thoracic discectomy in which tubular retractors and microscope visualization are used in performing a transpedicular thoracic discectomy. Eleven patients were operated on using the mini-open discectomy approach versus four patients operated on using an open dorsolateral approach. Patients operated on using the mini-open approach had less blood loss and a greater improvement in their modified Prolo score compared with the open procedure. At long-term follow-up, the modified Prolo score was similar for both groups of patients. Jho published a series of endoscopic transpedicular thoracic discectomies in 25 patients. A 1.5-cm trocar is placed at the junction of the lamina and facet via a paramedian incision. The medial portion of the facet, the very lateral portion of the lamina, and the rostral one third of the pedicle are removed using a high-speed drill. A limited amount of spinal cord dura and nerve root are exposed, and then a 70-degree lens endoscope is introduced, allowing for a discectomy to be performed under direct visualization. This surgery was able to be performed on an outpatient or overnight stay basis; no surgery-related complications were reported.

Technique.

The operation is performed with the patient in the prone position on a radiolucent frame and spinal table. The arms are placed at the sides, and the patient is taped to the table. Anteroposterior (AP) fluoroscopic imaging is used to identify the appropriate disc space. A 4-cm linear skin incision is centered over the disc space. The paraspinal muscles are subperiosteally reflected laterally, exposing the ipsilateral spinous process, lamina, facet joint, and transverse processes above and below the disc space. A small, self-retaining retractor is placed, and the fluoroscope is introduced to verify the correct level and the precise location of the underlying disc relative to the facet joint. Once this relationship is ascertained, a high-speed drill is used to facilitate a partial facetectomy ( Fig. 92-4A ). Care is taken to preserve the lateral margin of the inferior and superior articular processes of the facet joint and the entire pedicle directly caudal to the disc. When the partial facetectomy is completed, the underlying neuroforaminal fat is coagulated with bipolar cautery. The nerve root, which exits the spinal canal under the more rostral pedicle, is rarely encountered, except in the upper thoracic spine ( Fig. 92-4B ). The underlying anulus is coagulated and incised. The disc herniation is removed using conventional microdiscectomy techniques ( Fig. 92-4C ). As with the transpedicular approach, no fusion is required.

Transfacet pedicle-sparing approach.

Diagrams illustrating surgical sequence. Bar scale represents 0.8 cm = 1 cm. A mesial facetectomy is centered over the disc herniation. A, Fluoroscopy is used to limit the amount of bone removed. B, On completing the partial facetectomy, the foraminal fat is coagulated and the disc is exposed. C, The disc herniation is removed using conventional microdiscectomy techniques. Specially designed thoracic microdiscectomy instruments are helpful to facilitate safety during discectomy. Additionally, open endoscopy can be used to improve visualization of the central and contralateral spinal canal during disc removal.

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

Advantages.

Advantages of the transfacet pedicle-sparing approach may include diminished operating time, decreased blood loss, and limited bone and soft tissue removal. Like the transpedicular approach, perioperative pain, hospital stay, and return to premorbid activity appear to compare favorably with the more formidable ventrolateral and lateral approaches. When necessary, multiple disc herniations may be treated. The exposure is identical to that provided by the transpedicular approach. Preservation of the pedicle may improve long-term localized back pain results.

Disadvantages.

The disadvantages are the same as for the transpedicular approach. Specially designed thoracic microdiscectomy instrumentation and, on occasion, open endoscopic visualization of the disc and ventral dural mater have enhanced safety during the disc removal.

Clinical Experience.

Zhang and coworkers published a series of 18 patients treated with the transfacet pedicle-sparing approach with dorsal instrumentation and fusion. Although the transfacet approach was published with the goal of avoiding dorsal instrumentation, the patients in this series all had additional segmental instrumentation. All patients had good exposure of the disc space and good decompression of the spinal cord. These investigators experienced a complication rate of 33%, with six of the patients requiring additional surgery; five had wound infections or seromas requiring washout and one required revision of a misplaced screw.

Technique.

The basic underlying instrumentation used in all approaches involves a dorsolateral approach, endoscope, and tubular dilators. The patient is usually placed in a prone position; however, Jho has placed the patient in a lateral position for an endoscopic transpedicular thoracic discectomy. The approach used by Fessler and colleagues involves a prone position on a radiolucent Wilson frame. A localizing radiograph is obtained to determine the level of the thoracic disc. A paramedian skin incision is made at the level of the disc, approximately 3 to 4 cm lateral to the midline. A series of tubular muscle dilators are then placed, and the tubular retractor is placed to form a working port for the endoscope. The endoscope is passed down the center of the tubular retractor. Under endoscopic visualization, the muscle and soft tissue is cleaned off at the level of the transverse process and lateral aspect of the facet. A drill then excises the junction of the transverse process and lateral facet, allowing access to the disc. The pedicle is identified, and drilling of the superior aspect of the caudal pedicle is performed to allow access to the thoracic disc. The disc anulus is identified and cut, and the endoscope is tilted for a 30-degree visualization similar to a transforaminal-type approach. The disc is removed, and a down-going curet or a Woodson elevator is used to push down the disc fragment away from the spinal cord. After the discectomy is performed, the tubular retractor is removed and the wound closed.

Advantages.

The main advantages of the minimally invasive approaches are potentially less destruction to the dorsal paraspinal muscles, minimal bone and ligamentous removal, maintenance of disc integrity, avoidance of thoracic fusion, and avoidance of chest entry. The ideal result would be minimal trauma to the adjacent tissue during the approach to the thoracic disc and its removal. As a result, potential recovery time, amount of blood loss, and length of hospital stay would be minimized.

Disadvantages.

The main disadvantage of a minimally invasive endoscopic approach is the learning curve and familiarity with the anatomy. This approach should be performed by individuals with facility using the endoscope and previous experience with the open dorsolateral approach. Minimally invasive approaches can turn out to be maximally invasive approaches when the learning curve is steep. Visualization is good at the point of entry and is limited to familiarity with the anatomy seen on the endoscope.

Clinical Experience.

Three main series using this approach have been published. Perez-Cruet and colleagues have a series of seven patients operated on using a minimally invasive thoracic microendoscopic discectomy (TMED). Results demonstrated no morbidity with this approach, good access, and quick return to work. Khoo and coworkers described an extension of this technique in 13 patients using a microscopic tubular approach via a far lateral oblique trajectory for removal of the thoracic disc fragment followed by interbody arthrodesis and cage stabilization of the segment ( Fig. 92-5 ). No case in either series required conversion to an open procedure. Jho reported a series of endoscopic transpedicular approaches also with excellent results. His series is based on a more extensive pedicle takedown, coming in more medially than Perez-Cruet. Results were also excellent for visualization, disc removal, and quick return to work.

A, The working portal is docked at a far lateral oblique trajectory similar to that of the lateral extracavitary approach in contrast to the more vertical transpedicular technique. B, Initial bone removal is initiated after docking at the lateral facet. C, As the transverse process and lateral facet are removed with a drill, the underlying soft-tissue structures, including the ligamentum flavum and the herniated disc, are encountered. The rostral portion of the pedicle is then drilled nearly flat to the disc space. This provides direct view of the disc space. D, Dissection of the ligamentum flavum will now clearly demonstrate the herniated disc as well as nerve root, ganglion, and the lateral portion of the spinal cord. The disc is removed with pituitary rongeurs and microcurettes. E, After removal of the disc and ligament, a near-lateral view of the decompressed spinal cord and disc interface should be possible. F, Through this far lateral window, composite bone graft and an interbody cage is placed obliquely in to the disc space for stabilization and arthrodesis of the segment.

Technique.

The procedure is performed with the patient prone and taped to the table with arms at the side. A hockey stick skin incision is made, with the vertical portion centered over the area of pathology ( Fig. 92-6A ). Caudally, the incision is gently curved off the midline for 8 to 12 cm, enabling the skin, subcutaneous tissue, and fascial flap to be rotated far laterally. Alternatively, a paramedian lunar-shaped incision may be used. The erector spinae muscles are subperiosteally dissected off the dorsal ribs and transverse processes and flapped medially. The erector spinae muscle complex may be wrapped in a moistened laparotomy pad and gently retracted medially. Intraoperative imaging helps ensure removal of the rib that articulates with the correct disc space ( Fig. 92-6B ). Once the proximal 8 to 12 cm of rib is resected, the underlying intercostal nerve is identified and traced into the neural foramen ( Fig. 92-6C ). The pedicle caudal to the disc is identified and removed, exposing the lateral aspect of the dura mater ( Fig. 92-6D ). At this point, the dorsal third of the disc space is removed. Care is taken to leave intact the dorsal-most margin of disc and the posterior longitudinal ligament ( Fig. 92-6E ). The dorsal-caudal quarter of the rostral vertebra is drilled out, as is the dorsal-rostral quarter of the caudal vertebra. This creates a cavity so that the remaining dorsal disc and posterior longitudinal ligament can be gently depressed away from the spinal cord ( Fig. 92-6F ). The ventral dura mater can then be inspected either directly, with small dental mirrors, or with an endoscope. The rib, which was resected to facilitate exposure of the disc space, is then fashioned into strut grafts and carefully impacted into the cavity ( Fig. 92-6G ). The ventral dura mater and spinal canal are then inspected again to ensure that there is no encroachment by the bone grafts.

Advantages.

One major advantage of this procedure is the enhanced safety during the disc removal because of direct visualization of the dura mater before and during the decompression, which is facilitated by the removal of the pedicle. Additionally, because of the extensive amount of rib removed compared with the other lateral procedures, the exposure to the ventral spinal canal is improved. Surgeon orientation is almost truly lateral. By remaining extrapleural, the procedure avoids the complications observed with intrathoracic surgery. These include the need to place a thoracostomy tube and various pulmonary complications (CSF–pleural) fistula, pneumonia, and complications related to the need to take down the diaphragm at the thoracolumbar junction). A ventral strut graft can be placed with relative ease. Finally, in the rare instance of multiple symptomatic discs, multiple levels can be exposed.

Disadvantages.

The major disadvantage of LECA is that it is a formidable operation with a potential for significant perioperative pain. Additionally, there is a potential for a prolonged operating time and considerable blood loss, especially early on in a surgeon’s experience. In experienced hands, however, these parameters appear to be comparable to the ventrolateral approaches. Densely calcified central discs, intradural fragments, ventral dural tears, or discs that are completely enveloped by the dura mater may be difficult to remove without the need to elevate the dura mater. These conditions may be better treated using a ventrolateral approach. Finally, as is the case with ventrolateral surgeries, we do not generally recommend LECA in the medically high-risk patient.

Technique.

Patients are placed prone and taped to the table so they can be rotated 15 to 20 degrees away from the surgeon during the decompression. The arms are kept at the sides. A midline incision extends two spinous processes above and below the disc to be removed. Caudally, the incision is gently curved laterally to the scapular line on the side of pathology. To minimize postoperative seroma formation, the incision is carried down to the deep fascia, with only minimal subcutaneous undermining. The rhomboid and trapezius muscles are then dissected off the spinous processes. A myocutaneous flap is rotated toward the medial scapular border. The caudal fibers of the trapezius muscle are transected to reflect the flap. It is important to protect the rostral latissimus dorsi fibers while cutting the inferior portion of the trapezius muscle. The musculocutaneous flap is limited by the skin incision and the medial scapula. The scapula rotates laterally as the trapezius and rhomboid muscles are mobilized. This increases the exposure of the ribs laterally for better orientation to the ventral spinal cord and central disc space.

Most of the advantages and disadvantages of LECA are identical to those for its LPEA modification. The following sections emphasize points that are specific to the LPEA surgery.

Advantages.

The major advantage of this technique is that it simplifies removal of upper thoracic disc herniations by providing a far lateral orientation to the disc space at this level. This far lateral exposure enhances safety during decompression by improving visualization across the ventral spinal canal. Superior mediastinal structures, which may be traumatized with other approaches to the upper thoracic spine, are avoided. Recurrent laryngeal nerve palsies are also avoided.

Disadvantages.

Disadvantages include the potential for shoulder morbidity from scapular mobilization, T1 nerve injury, Horner syndrome, sympathectomy, and intercostal neuralgia.

Technique.

Different costotransversectomy techniques have been proposed. Patient positioning options vary from prone to modified lateral decubitus. Skin incisions likewise vary and include the paramedian incision along the lateral border of the erector spinae muscles and a semilunar incision. A skin, subcutaneous tissue, and fascial flap may be rotated medially toward the spinous process. The trapezius muscle can be incised in line with the skin incision and retracted medially. The erector spinae muscles are then dissected from their attachments and can be reflected medially. Some surgeons prefer to cut this muscle complex and reapproximate it at the time of closure. From this point, surgical decompression is the same as for LECA.

Advantages.

Skin and muscle manipulation and the amount of rib resection are somewhat less than with LECA or LPEA, offering the theoretic advantages of comparatively diminished perioperative pain and a possibly shortened length of hospitalization.

Disadvantages.

This is a more dorsal approach than that provided by the other two lateral surgeries. Consequently, the visualization of the central spinal canal is not as good as with those approaches.

Clinical Experience.

LECA has been augmented by the use of a neuronavigational system for frameless stereotaxy by Kim and colleagues, who used the Stealth surgical navigation system (Stealth Surgical, Gordonsville, VA) to localize the anatomy and provide feedback regarding the dura relative to the disc. Five patients were operated on in this manner with good complete removal of the herniated disc relative to the spinal cord. These investigators cite the advantage of accurate knowledge of the surgical instrumentation relative to the surrounding structures not directly visible in the operating field.