Because of the ventral position of the disk herniation and its partial calcifica- tion in the patient described in the Case Presentation, an approach that offered a lateral angle of attack was felt to be more suitable. The retropleural approach described by Otani and colleagues6 and McCormick and colleagues7 affords a lateral approach without pleural violation or the need for single lung ventilation, but still requires a relatively large exposure with extensive soft tissue manipula- tion. Utilizing the benefits of minimally invasive tubular retractor systems, a modi- fication is presented that minimizes the morbidity of the traditional retropleural approach.
Tips from the Masters 4-3 • Midline and calcified disk herniations are relative indications for lateral or anterolateral approaches such as the minimally invasive retropleural approach and thoracoscopic approaches.
FUNDAMENTAL TECHNIQUE
Tips from the Masters 4-4 • Depending on the spine level of the disk and the patient’s individual anatomy, the initial thoracotomy in the minimally invasive retropleural approach may be at the level, or a level above, the disk space of the patient’s lesion. The more distal the segment, the more caudally angulated the rib, and the more likely that the initial thoracotomy will need to be performed at the level above.
Tips from the Masters 4-5 • If greater exposure is needed, the minimally invasive retropleural approach is easily converted into an open retropleural thoracotomy.
The patient was placed in the standard lateral position for an open retropleural approach, with the ipsilateral arm positioned above the head to elevate the scapula.
As is true in most patients, a lateral fluoroscopic image demonstrated that the T7 rib covered the site of the pathology, that is, the T7-8 disk space that articulates with
the T8 rib head. This is a result of caudal angulation of the rib from its costovertebral articulation. A 4-cm incision was made over the T7 rib. The exposed rib was dis- sected free of its muscle insertions, with care taken to preserve the T7 neurovascular bundle. A2 to 3 cm section of the rib was resected without violation of the parietal pleura. Using blunt dissection, the parietal pleura was elevated off the ventral sur- face of the proximal rib. With account taken of the caudal rib angulation, a direct lateral approach to the anterolateral surface of the spine allowed exposure of the T7-8 disk space. Once the anterolateral spine was identified, the dissection cavity was extended to allow visualization of the proximal T8 rib and rib head. The pari- etal pleura over the T8 rib head, the T7-8 disk space, and the lateral aspect of the T8 vertebral body was mobilized and reflected ventrally. A thin malleable retractor was placed over the reflected parietal pleura to protect and retract the lung, which continued to be ventilated. An expandable tubular retractor was placed through the mini-thoracotomy, docked over the rib head and disk space, and locked into position (see Figure 4-1, C ). The procedure was performed through the tubular retractors using the intraoperative microscope for visualization. The rib head was removed with a drill and rongeurs providing exposure of the disk space. The canal was defined using the T8 pedicle as the principal landmark. The diskectomy was performed with standard techniques using curettes, rongeurs, and drill with modifi- cations for minimally invasive spine surgery.
Tips from the Masters 4-6 • A narrow, malleable retractor is a useful adjunct to a tubular retractor to protect the lung and keep it out of the operative field, which obviates the need for lung deflation during surgery.
Tips from the Masters 4-7 • Drilling of the rib head and the posterolateral end plates of the vertebral bodies is useful to provide additional exposure and space in which to deliver the disk herniation.
Postoperative course: The patient did not require a chest tube and had an unevent- ful postoperative recovery. Because of her gait disorder, she was discharged to an acute inpatient rehabilitation facility on postoperative day 3. She was discharged home after 2 weeks and was seen 1 month after surgery. At this time she had had modest improvement in her neurologic symptoms and was taking a small amount of narcotic pain medication. At last follow-up, 3 months after surgery, she had stopped taking all narcotics and had experienced a significant improvement in leg strength and gait as well as resolution of her urinary dysfunction.
DISCUSSION OF BEST EVIDENCE
The history of surgery for thoracic disk herniations reflects disaffection with the dismal neurologic outcomes from a purely dorsal approach (i.e., laminectomy) and the subsequent adoption of lateral or posterolateral approaches (transpedicular, lat- eral extracavitary, retropleural) that resulted in excellent neurologic outcomes but were more invasive.6-9 The subsequent development of less invasive approaches stemmed from a desire to mitigate postoperative pain and recovery time while main- taining excellent outcomes. To date, the best evidence regarding minimally invasive approaches to thoracic diskectomy is confined to small retrospective surgical series and descriptions of operative techniques.3,5 These reports illustrate the feasibility and initial efficacy of less invasive approaches for this pathologic condition in selected patients. The evidence cannot begin to elucidate the superiority of one approach over another. Indeed, given the relative rarity of this lesion, and the case-to-case het- erogeneity, such comparisons will be difficult and perhaps inappropriate. The deci- sion of whether to use a less invasive approach over a more invasive one and which approach to select is likely to remain primarily influenced by the constraints of the pathologic features present and the training and expertise of the individual surgeon.
COMMENTARY
Thoracic disk herniations are extremely heterogeneous with respect to presenting symptoms, anatomic relationship to the spinal cord, and intrinsic physical proper- ties. This explains to a large degree why there is such an array of approaches for what is a relatively rare surgical disease. The extremes illustrate this point. What is required of a surgical approach for the safe, effective removal of a soft lateral disk herniation causing a radiculopathy bears little resemblance to what is required for a calcified midline disk or osteophyte causing myelopathy. The foremost consider- ation is the ability to safely remove the lesion regardless of the invasiveness of the exposure. Having said this, there are clearly some thoracic disk herniations that do not require extensive exposures. As is often the case in spine surgery, judicious selection of the approach based on the nature of the lesion and the surgeon’s own expertise is paramount, as is a back-up plan should the initial surgical approach prove unfeasible.
REFERENCES
1. Isaacs RE, Podichetty VK, Sandhu FA, et al: Thoracic microendoscopic discectomy: a human cadaver study, Spine 30:1226–1231, 2005.
2. Jho HD: Endoscopic transpedicular thoracic discectomy, J Neurosurg 91:151–156, 1999.
3. Perez-Cruet MJ, Kim BS, Sandhu F, et al: Thoracic microendoscopic discectomy, J Neurosurg Spine 1:58–63, 2004. A retrospective review of data for seven patients with soft disk herniations who under- went diskectomy via the transfacet approach using a muscle-splitting tubular retractor and endoscopic visualization. Outcomes were excellent, and no complications were reported.
4. 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. This study describes the transfacet approach to thoracic diskectomy with a unilateral muscle dissection and the authors’ experience with the approach in cadavers and six patients. The authors reported excellent outcomes and decreased perioperative morbidity compared with other approaches.
5. Rosenthal D, Dickman CA: Thoracoscopic microsurgical excision of herniated thoracic discs, J Neu- rosurg 89:224–235, 1998. A retrospective review comparing outcomes for 55 patients who underwent thoracoscopy for thoracic disk herniations with outcomes for 18 patients who underwent thoracotomy and 15 patients who underwent costotraversectomy. Neurological outcomes were similar. However, patients in the thoracoscopy group had fewer pulmonary complications, less pain, and shorter length of hospital stay than those in the thoracotomy group.
6. Otani K, Yoshida M, Fujii E, et al: Thoracic disc herniation. Surgical treatment in 23 patients, Spine 13:1262–1267, 1988.
7. McCormick PC: Retropleural approach to the thoracic and thoracolumbar spine, Neurosurgery 37:908–
914, 1995. This study describes in detail the retropleural approach to the thoracic spine and the author’s initial experience in treating a range of pathologic conditions, including thoracic disks.
8. Benzel EC: The lateral extracavitary approach to the spine using the three-quarter prone position, J Neurosurg 71:837–841, 1989.
9. Patterson RH Jr, Arbit E: A surgical approach through the pedicle to protruded thoracic discs, J Neuro- surg 48:768–772, 1978.
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