44 Minimally Invasive Spine Surgery: Lumbar Case Studies

The patient showed a central disc herniation at L4–L5 ( Fig. 44.1).

44.2.3 Preoperative Notes

The patient failed 6 weeks of nonoperative therapy including physical therapy (PT) and chiropractic manipulation. He was offered epidural steroid injection (ESI), but he refused.

44.2.4 Instrumentation Notes

There is no indication for instrumentation is this case.

44.2.5 Surgical Approach and Technique

The patient was induced with general anesthesia and intubated endotracheally. Appropriate arterial and venous access was obtained. The patient was then turned into the prone position on the Wilson frame. Fluoroscopy was placed in the lateral position and the patient’s lumbar spine was shaved, prepped, and draped in the usual sterile fashion. Using lateral fluoroscopy, an appropriate incision to approach the left L4/L5 level was identified and marked 1.5 cm off the midline. This area was infiltrated with 0.5% Marcaine with epinephrine. A no. 10 scalpel was then used to incise the skin over approximately 2 cm. Hemostasis was obtained with bipolar cautery. A Kirschner wire (K-wire) was then placed through the incision and advanced to the L4/L5 facet. This position was confirmed fluoroscopically. A series of dilators was then placed over the K-wire, and after the first dilator was placed the K-wire was removed. Finally, the working channel was positioned, angled medially, and locked in place. This position was confirmed fluoroscopically. Camera was then introduced into the working channel. 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. Kerrison punch was used to perform a hemilaminotomy and this was extended into a medial facetectomy using the Legend (Sofamor Danek, Memphis, TN) drill with a cutting M8 burr. The traversing nerve root was then retracted slightly medially, and the epidural space explored. The bulging disc was identified and confirmed fluoroscopically. A no. 15 blade scalpel was used to incise the annulus, and a discectomy was performed using a series of curettes and pituitary rongeurs. At the completion of decompression, the exiting and traversing nerve roots were noted to be well decompressed throughout their course. Hemostasis was obtained with bipolar cautery and Gelfoam. The wound was copiously irrigated with antibiotic solution and the retractor was removed. Fascia was closed using 0 Vicryl stitches. The subcutaneous tissue was closed using 2–0 Vicryl stitches. Finally, the skin was closed using Dermabond. The patient was then returned to the supine position and allowed to recover from anesthesia.

Fig. 44.1 Sagittal T2-weighted MRI demonstrates an extremely large, central disc herniation at the L4–L5 level.

44.2.6 Postoperative Care

Radiographic imaging demonstrated a mobile grade I spondylolisthesis at the L3/L4 level due to an old bilateral pars defect ( Fig. 44.2a,b).

44.3.3 Preoperative Notes

The patient was offered anterior versus posterior versus combined (360-degree) approaches. He elected for a posterior approach, which was more likely to achieve a successful reduction and fixation in a single-stage operation. Additionally, the patient had relatively normal spinal canal diameter at the L3–L4 level and did not require direct decompression to address spinal canal stenosis.

44.3.4 Instrumentation Notes

Accomplishing a percutaneous interbody fusion requires the use of expandable cages that can be placed through Kambin’s triangle. As such, all disc preparation and graft placement must be carried out through a maximum of an 8-mm corridor. Percutaneous screws are placed in standard fashion.

44.3.5 Surgical Approach and Technique

The patient is given sedation with propofol anesthesia but no narcotics. Positioning is prone on a Jackson table. A flank incision is made 12 cm off the midline and access is made into the disc space using the extraforaminal endoscopic approach into Kambin’s triangle. After discectomy and nerve root decompression, disc clearance can be achieved utilizing specialized brushes that do not violate the bony end plate. After disc space preparation, the space is filled with graft material and the interbody expandable cage is inserted. Expansion of the cage allows interbody distraction, spondylolisthesis correction, fusion, and indirect decompression of the contralateral nerve root with disc and foraminal height restoration ( Fig. 44.2f). Percutaneous screws are then placed after injecting the screw tracts with long-acting local anesthetic medications.

44.3.6 Postoperative Care

The patient is managed postoperatively with standard pain management and bracing, similar to standard open surgery.

44.3.7 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.

44.3.8 Operative Nuances

Performing this procedure without a general anesthetic requires careful attention to patient selection, preserving soft-tissue structures, use of expandable cages, specialized percutaneous screws placed through smaller incisions, and the use of long-acting local anesthetics. In addition, thoughtful coordination with the anesthesiologist is key.

Fig. 44.2 (a,b) Sagittal X-ray and MRI views of a patient with a grade I L3/L4 spondylolisthesis. (c,d) Entry and dilation of the intervertebral disc space through Kambin’s triangle. (e) Removal of the disc using a drill with end plate bone preservation. (f) Filling of the disc space with a contrast-filled balloon to ensure adequate disc removal and end plate contact. (g) Intervertebral allograft cage in place and cannulation of pedicles above and below. (h,i) Final fluoroscopic images before disarticulation of the screw and rod extensions.

A 57-year-old woman presented with difficulty standing, walking, and working due to intractable low back pain. She had lost 3 inches of height over the past 4 years. Imaging revealed the patient had a degenerative kyphoscoliosis, consistent with her symptoms ( Fig. 44.3a).

Fig. 44.3 (a) Anteroposterior (AP) and (b) lateral 36-inch standing X-rays showing a degenerative kyphoscoliosis. (c) Intraoperative view showing placement of the four rods through screw extensions and fracture at the mini-pedicle subtraction osteotomy site. Final (d) AP and (e) lateral 36-inch standing X-ray plane films.

After positioning the patient on a Jackson table, a dorsal midline skin incision is made. However, the deeper soft tissues are dissected only at the level of the PSO. Thus, this exposure is similar to an open two-level lumbar fusion. Interbody fusion is performed below the level of the PSO using the MIS transforaminal lumbar interbody fusion (TLIF) technique. The L3 level PSO is performed in standard fashion with spinous process, lamina, and facet removal. This is followed by pedicle removal and a bilateral de-cancellation osteotomy using a series of enlarging curettes to remove two cones of cancellous bone from the vertebral body. Central bone was removed with a curved curette and the de-cancellation is extended superiorly into the L2–L3 disc space. A Leksell rongeur is then used to remove the lateral vertebral body wall bilaterally in a wedge-shaped pattern to match the de-cancellation. Control of the spine to break the osteotomy is then achieved by placing percutaneous pedicle screws at least three levels above and below the PSO site. A total of four rods are bent and passed through each set of screw heads above and below the PSO. The posterior vertebral body wall and posterior longitudinal ligament are removed, and after ensuring there is no ventral bone or ligament that might impinge on the thecal sac, the osteotomy is closed ( Fig. 44.3c). The L3 nerve roots and thecal sac are then inspected to ensure that there is no neural compression, and any bleeding is controlled with powdered collagen matrix. The cranial and caudal rods are connected with offset connectors, and the construct is finally tightened and fusion of the facets above the PSO is achieved through small access sites ( Fig. 44.3d,e).

44.4.6 Postoperative Care

The patient is managed postoperatively with standard pain management and bracing, similar to standard open surgery.

44.4.7 Management of Complications

As with open osteotomies and deformity corrections, these patients are subject to risks associated with bleeding, nerve root compression, pseudoarthrosis, and spinal misalignment.

44.4.8 Operative Nuances

Great care must be taken to connect the four rods properly and also to bend them to the proper degree of lordosis.

44.4.9 Postoperative Results

In a series of patients treated in this manner, significant reductions in blood loss were made possible by reducing the amount of soft-tissue dissection and subperiosteal exposure.

44.5 Case 4: Minimally Invasive Lateral Lumbar Interbody Fusion

44.5.1 Patient Profile

A 56-year-old woman with history of multiple motor vehicle accidents (MVA) and falls presented with 3 years of low back pain, radiating bilaterally to her lateral thighs, calves, and ankles ( Fig. 44.4).

44.5.2 Case Selection

Two-level spondylolisthesis with back pain equal to or greater than radicular pain suggests that fusion, rather than just decompression, is the better option for this patient. MIS techniques include TLIF or lateral lumbar interbody fusion (LLIF). In this case, LLIF seems to be the less invasive technique, and enables more rapid recovery.

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