Minimally Invasive Techniques for Adult Lumbar Scoliosis

Indications

Low-grade spondylolisthesis

Degenerative disk disease causing discogenic low back pain

Recurrent disk herniation with significant mechanical back pain

Post-diskectomy interbody space collapse with neuroforaminal stenosis and radiculopathy

Recurrent disk herniation (third or more), lumbar disk herniation with radiculopathy (with or without back pain)

Treatment of pseudarthrosis

Treatment of post-laminectomy kyphosis

Treatment of lumbar deformity with coronal/sagittal plan imbalance

Relative contraindications

Single-level disk disease causing radiculopathy without symptoms of mechanical low back pain or instability

Osteomyelitis/diskitis

Severe central canal stenosis

Greater than three levels of surgery

Cobb angle >20° over fused segments^a

Severe osteoporosis

^aExcept as guided by the MISDEF algorithm

The advantages of the transforaminal approach (MIS and open) for interbody placement are numerous. There is direct decompression of the nerve root on the ipsilateral side of the interbody graft placement. The graft is placed through Kambin’s triangle and typically does not require any retraction on the thecal sac or the exiting nerve root. The posterior lumbar interbody fusion (PLIF) technique, on the other hand, often requires retraction of the thecal sac placing the traversing nerve root at risk during interbody graft placement. The anterior lumbar interbody fusion (ALIF) and lateral lumbar interbody fusion (LLIF) are an additional way to achieve interbody fusion and indirect decompression of the nerve roots. However, additional fixation may be required with percutaneous screws and/or additional decompression, which may require changing the patient’s position or staging the procedure adding to the overall operative time. Disadvantages of MIS-TLIF include the limited size of the interbody graft that can be placed through Kambin’s triangle. Pedicle screw distraction while placing an interbody graft could allow a surgeon to place a larger interbody spacer. Newer interbody technology including expandable cages and rotated cages may allow for a taller interspace device than what must fit through the annulotomy in Kambin’s triangle. While multiple levels may be addressed through a MIS-TLIF, an open TLIF may be a better option for multilevel fusions with severe central canal stenosis to decrease operative time. Additionally, it may be difficult to adequately decompress a severely stenotic contralateral foramen without significant risk of durotomy or nerve root entry though a MIS approach.

Adult Spinal Deformity

With the increasing age of the overall population, adult spinal deformity (ASD) is increasing in incidence and has a significant impact on health and disability. Traditional open spinal deformity correction surgery is associated with significant intraoperative blood loss, relatively high perioperative morbidity, increased length of hospital stay, and pain. To reduce these surgical comorbidities, MIS approaches for spinal deformity correction have been utilized. There are limitations on the amount of sagittal correction and curve correction that can be accomplished through MIS techniques. The minimally invasive spinal deformity (MISDEF) algorithm [5] can be a guide for patient selection with MIS techniques in ASD (Fig. 12.1). This algorithm underwent multiple revisions prior to its current state. It was revised from six arms of treatment to three arms to decrease the complexity and increase the inter- and intraobserver reliability. The algorithm was developed with a Delphi approach by 11 fellowship-trained spinal surgeons. A Class I approach is accomplished through a minimally invasive or mini-open muscle-sparing decompression alone or MIS fusion of a single listhetic level regardless of the curve apex. Instrumentation may be placed via a percutaneous technique or through an expandable port tube. A Class II approach entails MIS or mini-open decompression and interbody fusion of the curve apex or the entire coronal Cobb angle of the major curve. A Class III approach entails a traditional open surgical approach involving osteotomies and/or extension of the fusion into the thoracic spine. Class I patients have a sagittal vertical axis (SVA) less than 6 cm, pelvic tilt (PT) less than 25°, lumbar lordosis-pelvic incidence (LL-PI) mismatch of less than 10°, lateral listhesis less than 6 mm, and coronal Cobb angle less than 20°. These patients are candidates for MIS-TLIF with a single-level fusion. Class II patients have a SVA less than 6 cm, PT less than 25°, LL-PI mismatch of 10°–30°, a lateral listhesis greater than 6 mm, thoracic kyphosis less than 60°, and/or a coronal Cobb angle larger than 20°. Additionally, flexible curves with SVA >6 cm that correct to less than 6 cm when supine are included in this group. These Class II patients may be candidates for a multilevel decompression and fusion at the apex or along the entire coronal Cobb of the curve. Interbody fusion may be accomplished with multiple MIS-TLIF. Class III patients have SVA greater than 6 cm that do not correct on supine films, PT >25°, LL-PI mismatch greater than 30°, and/or thoracic hyperkyphosis greater than 60°. Class III patients cannot typically be corrected with MIS techniques because these patients have deformities that often require extensive open posterior osteotomies.

Fig. 12.1

Minimally invasive spinal deformity (MISDEF) algorithm for decision-making when considering less invasive surgery. Y yes, N no

Technique

Patient Positioning

Optimal preoperative positioning of the patient is required to achieve success with the MIS-TLIF. We prefer a prone position on a Wilson frame attached to a radiolucent Jackson table. The use of the Wilson frame allows us to maximize access during the interbody work by flexing the spine in the “cranked-up” position. Following interbody placement the Wilson frame is “cranked down” to maximize lumbar lordosis prior to securing rods. Prior to draping patients, we routinely obtain anterior-posterior (AP) and lateral fluoroscopic images to identify the bony spinal anatomy including the pedicles and verify that the surgery can be accomplished safely (Fig. 12.2). For L4-5 level fusions, we keep the operative table parallel to the floor. However, for L5-S1 cases, we usually position the operative table in 20°–30° of reverse Trendelenburg to allow the surgeon to have a more convenient view of the inferiorly angled L5-S1 disk space by orienting it perpendicular to the floor.

Fig. 12.2

AP x-ray marking the lateral borders of the pedicles at L4 and L5 prior to draping the position. The skin is marked and the needle removed prior to prepping the patient

Pedicle Screw Placement

Pedicle screws may be placed either through a percutaneous technique or via a mini-open technique. The percutaneous technique utilizes AP and lateral fluoroscopy to visualize the pedicles. The skin is incised just lateral and slightly superior to the pedicle. A Jamshidi needle is placed on the upper and lateral border of the pedicle while contacting the bone. It is then driven to the medial border of the pedicle wall under AP fluoroscopy. Lateral views then confirm the depth of the Jamshidi needle. If the Jamshidi needle has been driven to the depth of the posterior edge of the vertebral body without violating the medial border on AP images, it is advanced approximately 2 cm further into the vertebral body. A K-wire is placed through the Jamshidi needle, and the Jamshidi needle is removed. The pedicle is subsequently tapped, and a pedicle screw is placed over the K-wire using fluoroscopy to ensure the K-wire is not being driven deeper into the vertebral body.

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