Minimally Invasive Spine Surgery: Thoracic Case Studies

31 Minimally Invasive Spine Surgery: Thoracic Case Studies


Mick J. Perez-Cruet, Richard G. Fessler, and Michael Y. Wang


Abstract


Minimally invasive spine (MIS) approaches to the thoracic spine allow many advantages by preserving the normal anatomic integrity of the thoracic spine. These techniques ultimately result in less tissue damage, faster patient recoveries, and quicker return to improved quality of life. However, it must be cautioned that many of these approaches require specialized training including MIS fellowships, cadaveric workshops, and/or MIS surgeon expert-guided intraoperative training. The thoracic spine is perhaps the most delicate segment of the spine, and overaggressive manipulation can result in permanent neurological deficits. This chapter illustrates a number of thoracic cases that will show the benefits of mastering these challenging but greatly patient-rewarding approaches and techniques to treat trauma, tumor, and degenerative pathology.


Keywords: thoracic pathology, minimally invasive, trauma, tumor, degenerative


31.1 The Evolution of Thoracic Minimally Invasive Spine Surgery


Thoracic minimally invasive spine (MIS) surgery has a long and rich history. This is due in part to the fact that access through the pleural cavity affords the use of endoscopic as well as minimally invasive techniques in a body cavity and thus is a natural extension of general surgical endoscopic and MIS approaches. While the use of thoracoscopy to access the anterior thoracic vertebral column was a natural development, its adoption has been limited by the different and unique skill set that is not part and parcel with traditional spinal surgery.


31.2 Case 1: Retropleural Thoracic Discectomy


31.2.1 Patient Profile


A 60-year-old female with osteoporosis developed a low-energy L1 fracture. She had developed progressive pain in the upper back with a progressive spinal deformity. The pain was associated with mechanical loading, and her symptoms were progressive (image Fig. 31.1a–f).


31.2.2 Case Selection


With severe osteoporosis, the patient was started on pharmacologic treatment to improve her bone density. Extensive counseling was undertaken to inform the patient of the risks and benefits of surgical versus conservative management. The decision was made to perform a MIS anterior and posterior operation to most optimally correct her deformity without performing a long segment fusion.


31.2.3 Preoperative Notes


Extensive discussion was undertaken regarding the length of the construct, given her coronal and sagittal imbalance. The patient refused to have a long segment fusion, for example, a T5 iliac, as a first attempt to correct her problem; therefore, a more parsimonious approach was chosen. The patient was also counseled on the off-label use of recombinant human bone morphogenetic protein (rhBMP-2) as well as the potential risks of pleural violation and the need for a chest tube.


31.2.4 Instrumentation Notes


Numerous cage reconstruction and fixation options are available and it was decided that an expandable cage would give the best option for restoring anterior column height. Use of a polyetheretherketone (PEEK) cage more closely matched the patient’s bone modulus and thus might reduce the likelihood of significant settling.


31.2.5 Surgical Approach and Technique


In the direct lateral approach, the L1 vertebral body was targeted. A small 2-cm flank incision allowed dissection of the retropleural space, which allowed entry through a 3-cm direct lateral incision to place a tubular retractor. This then allowed cutting of the disc spaces above and below the L1 body with Cobb elevators and osteotomes (image Fig. 31.1g–j). Once L1 was removed, temporary distractors elevated the interbody height. This was followed by cage placement and expansion (image Fig. 31.1h–p). The patient underwent percutaneous screw fixation and further sagittal correction under the same anesthetic (image Fig. 31.1q,r). This resulted in a significant improvement, likely possible without employing a longer construct.


31.2.6 Postoperative Care


The patient is managed postoperatively with standard pain management and bracing, similar to standard open surgery. There was no chest tube necessary and chest X-rays did not demonstrate a pneumothorax.


31.2.7 Management of Complications


Routine antibiotic prophylaxis is used to minimize the risk of postoperative infections. Pseudarthrosis can be minimized with proper graft site preparation, use of appropriate graft materials, bracing, external bone stimulation, and the elimination of tobacco use.


31.2.8 Operative Nuances


Great care is taken at the level of the diaphragm to minimize its disruption. Careful direct visualization of the retropleural space is also necessary given the ease with which the pleura is violated.



31.2.9 Postoperative Results


This approach is being employed more commonly given the significant morbidity associated with thoracoabdominal and thoracotomy approaches.


31.3 Case 2: Percutaneous Thoracic Fixation for Trauma


31.3.1 Patient Profile


A 46-year-old woman was involved in a high-speed motor vehicle accident (MVA), resulting in severe back pain. She was presented to the emergency department neurologically intact, but with axial pain 9/10. Imaging studies revealed a dislocation-dislocation at the T6–T7 level (image Fig. 31.2a, b).


31.3.2 Case Selection


With the absence of a large anterior disc herniation in a neurologically intact patient, a posterior approach with reduction, fixation, and fusion is a reasonable treatment option.


31.3.3 Preoperative Notes


The patient was neurologically intact with good alignment, so she was a good candidate for percutaneous fixation. On the other hand, this fracture was likely too unstable to be treated only with external bracing.


31.3.4 Instrumentation Notes


Numerous fixation options are available for thoracic percutaneous screw fixation. In this case, extension tab screws were chosen for ease of bringing the rod to the screw saddles while requiring a very small skin and fascial incision for placement.


31.3.5 Surgical Approach and Technique


The patient is positioned prone on a Jackson table with care not to overextend her and further disrupt the alignment. Screws are placed through 6-mm individual incisions. Pedicle targeting is achieved using the anteroposterior (AP) fluoroscopic view to enter the pedicle 2 cm without passing the medial wall of the pedicle to ensure the canal is not violated. Kirschner’s wires (K-wires) allow passage of an awl and tap under lateral fluoroscopic views, and screws are then placed. The rod is bent appropriately and then passed subfascially and connected to the screws using set screws (image Fig. 31.2c, d). The reduction portion of the screw extensions makes this an efficient process and also allows for correction of kyphosis. The facets can also be drilled, decorticated, and packed with graft materials for fusion. Wound closure is with a single stitch at each incision (image Fig. 31.2e).


31.3.6 Postoperative Care


If a fusion is not performed, the patient should be counseled on the possibility of needing a delayed hardware retrieval after bony fusion has occurred.


31.3.7 Management of Complications


Routine antibiotic prophylaxis is used to minimize the risk of postoperative infections.


31.3.8 Operative Nuances


Use of AP targeting minimized radiation exposure for the surgeon, and frequently four bilateral spinal levels can be targeted with a single fluoroscopic view.


31.3.9 Postoperative Results


Given the nature of polytrauma, such percutaneous approaches may be used for “internal bracing” and as “damage control surgery” to allow a patient to survive an injury without taking as much risk as in an open surgical procedure.



31.4 Case 3: Minimally Invasive Trans-facet Thoracic Discectomy


31.4.1 Patient Profile


The patient is a 56-year-old woman status post MVA. Immediately after the MVA, her legs “felt like jelly.” Since then she has had pain located below her bra line, radiating bilaterally around to her anterior chest. She has attempted physical therapy, has had 12 thoracic epidural steroid injections, and is on chronic narcotic pain medication without significant relief. MRI revealed T7/T8 herniated disc with compression and deviation of the spinal cord (image Fig. 31.3a, b).


31.4.2 Case Selection


This patient presents with a traumatic thoracic disc herniation and has failed 4 years of aggressive nonsurgical therapy. Because she has significant radiculopathy that correlates with her disc herniation level, she is an excellent candidate for thoracic discectomy.


31.4.3 Preoperative Notes


Other than mild distal right lower extremity weakness, the patient is neurologically intact. She does not have evidence of myelopathy. To ensure identification of the correct operative level, preoperative thoracic (to count ribs) and lumbar (to verify five normal lumbar vertebrae) X-rays are necessary. Furthermore, an MRI scout showing the herniation and the sacrum or C2 in the same cut is needed.


31.4.4 Instrumentation Notes


When a minimally invasive technique is used, instrumentation is not necessary.


31.4.5 Surgical Approach and Technique


The patient was induced with general anesthesia, intubated endotracheally, and turned into the prone position onto chest rolls. Using lateral fluoroscopy, an appropriate incision to approach the right T7/T8 level was identified and marked 1.5 cm off midline. The correct level was identified by counting vertebrae from S1 to the surgical level using continuous fluoroscopy. A no. 10 scalpel was then used to incise the skin over approximately 2 cm and a K-wire was placed through the incision and advanced to the T7/T8 facet. A series of dilators was placed over the K-wire, the K-wire was then removed, and the working channel was positioned, angled medially, and locked in place. Bovie cautery was used to remove a small amount of residual tissue at the bottom of the working channel. An angled curette was then used to define the sublaminar space below T7 and T8. Kerrison’s punch was used to perform a hemilaminotomy of T7/T8. This was extended into a medial facetectomy using a drill. An angled curette was then used to define the plane between the ligamentum flavum and dura. Ligamentum flavum was removed using a Kerrison punch. The disc space was then readily visible and palpable. A no. 15 blade scalpel was used to incise the disc space lateral to the dura. A series of curettes and pituitary rongeurs was then used to perform a lateral discectomy. Using down-pushing curettes, the disc bulge was pushed into the disc space and removed laterally using pituitary rongeurs. Exploration with a right-angled spatula revealed that the ventral dura was well decompressed. Hemostasis was obtained with Surgifoam and bone wax.


Oct 17, 2019 | Posted by in NEUROSURGERY | Comments Off on Minimally Invasive Spine Surgery: Thoracic Case Studies
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