Minimally Invasive Spinal Decompression and Stabilization Techniques I: Philosophy and Rationale

Evolution of Minimally Invasive Spine Surgery

Advances in the evolution of minimally invasive surgery (MIS) for fusion and stabilization included percutaneous interbody fusion during arthroscopic disc surgery, transperitoneal and thoracoscopically assisted placement of interbody cage implants in the lumbar and thoracic spine, and percutaneous translaminar facet screw placement. These techniques were eventually largely supplanted by modern minimally invasive procedures, such as percutaneous pedicle screw fixation, endoscopic laminectomy, endoscopic lumbar foraminotomy, minimally invasive lateral approaches for lumbar interbody fusion (i.e., extreme lateral interbody fusion [XLIF], oblique lateral interbody fusion [OLIF]), and minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF).

The majority of minimally invasive spine procedures now involve using progressively dilating retractor systems for access. Depending on the planned procedure, the access systems can be inserted at various angles and trajectories. These systems allow for many procedures to be performed in the lumbar, thoracic, and cervical spine. When fusion with an interbody strut is required, the tubular systems are placed slightly more laterally (∼3 cm from the midline), allowing for medial angulation to place the graft across the midline. The same tubular access can be used to place pedicle screws, and, if bilateral fixation is needed, percutaneous pedicle screws can be placed on the contralateral side using either image guidance systems or anteroposterior (AP) and lateral fluoroscopy. These techniques have been associated with similar or better outcomes when compared with open techniques.

Within the past 15 years, minimally invasive anterolateral approaches to the lumbar spine have increasingly become of interest because of their ability to spare the disruption of the paraspinal muscles, allowing for wide exposure to the disc space, shorter operative times, decreased blood loss, and indirect decompression. Brau et al. popularized the widely used mini-open retroperitoneal technique in 2002, which allows access to the anterior lumbar spine via a mini-transverse Pfannenstiel incision. This approach can be used to treat neurogenic claudication or radiculopathy caused by spondylosis, owing to its ability to indirectly decompress the foramen and thecal sac. In 2006, Ozgur and associates described an extreme direct or lateral lumbar interbody fusion (XLIF Nuvasive®, DLIF, Medtronic®, LLIF) technique that could be used to access the lateral aspect of the lumbar spine without entering the peritoneal space. This eliminated the need for an access surgeon, and a large interbody graft could be used. The approach was also used for far lateral disc herniations and was later expanded to place interbody grafts at multiple levels, thus allowing for significant correction of coronal deformities in scoliosis surgery. This lateral, transpsoas, retroperitoneal approach has since become commonplace in the world of minimally invasive spine surgery. In 2012, Silvestre and colleagues coined the term oblique lateral interbody fusion; however, this approach was first described by Mayer in 1997. OLIF has indications similar to XLIF; however, OLIF obviated the need for neurological monitoring because of its prepsoas approach and substituted intraoperative computed tomography (CT) with stereotactic navigation instead of fluoroscopic imaging.

The main advantages of endoscopic spine surgery are its lower morbidity, attributable to the minimally invasive approach, and cosmetic advantages. Significantly, patients experience less postoperative pain because of the avoidance of extensive muscular incision and removal of ribs. There also is less impairment of pulmonary function after video-assisted thoracoscopic surgery (VATS) compared with open thoracotomy. Dorsolateral endoscopic approaches for pedicular fixation result in less epidural bleeding, a decreased incidence of perineural and intraneural fibrosis, and less venous stasis.

The most significant disadvantage of endoscopic stabilization is that it is time consuming. This aspect can be overcome, but there is a considerable learning curve. The technology and equipment costs for this approach also create a large upfront investment requirement. All endoscopic approaches, especially thoracoscopic approaches, can be converted to open procedure, if necessary to control bleeding or to deal with excessive adhesions.

Lumbar Spine

A variety of laparoscopic, endoscopic, and minimally invasive techniques have been used or are currently used to stabilize and/or decompress the lumbar spine. Some of the most common procedures are discussed next, along with some potential complications that can be encountered.