31 Minimally Invasive Spine Surgery: Thoracic Case Studies

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 ( 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 ( Fig. 31.1g–j). Once L1 was removed, temporary distractors elevated the interbody height. This was followed by cage placement and expansion ( Fig. 31.1h–p). The patient underwent percutaneous screw fixation and further sagittal correction under the same anesthetic ( 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.

Fig. 31.1 (a) Sagittal CT reconstruction showing an L1 chronic compression fracture with deformity. (b) The spine shown on MRI, (c) flexion, and (d) extension lateral X-rays. (e) Thirty-six-inch anteroposterior scoliosis X-rays. (f) Thirty-six-inch lateral scoliosis X-rays. (g) Intraoperative lateral imaging to target the center of the L1 vertebral body. (h) A Cobb elevator cutting across the T12/L1 disc space. (i) Osteotomy cuts at the top. (j) Bottom of the L1 body. (k) Distraction of the fracture site with a temporary expandable cage on the right and (l) left sides of L1. (m) Initial placement of a radiolucent expandable cage using a shim to reduce the likelihood of end plate violation. (n) Following cage expansion. (o) Sagittal CT reconstruction showing height restoration at L1. (p) Axial CT showing central cage placement. (q) AP and (r) lateral final 36-inch standing films showing improvement in coronal and sagittal alignment.

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 ( 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.

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 ( 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 ( 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.

Fig. 31.2 (a) CT and (b) MRI sagittal reconstructions showing a T6–T7 disruption consistent with a ligamentous chance fracture. (c,d) Following placement of percutaneous screws, a rod bent into the appropriate kyphosis is introduced and passed subfascially. (e) Postoperative anteroposterior X-ray.

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 ( 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.

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