The complications and technical challenges associated with anterior endoscopic surgery led to the development of a new trajectory to the intervertebral discs (Fig. 1.3). It was described as lateral endoscopic transpsoas retroperitoneal approach (LETRA) and was first presented in 2001 [40]. This technique utilized a blunt finger dissection of the retroperitoneal space, insertion of tubular portals with endoscopic visualization, but without EMG monitoring. The first clinical report on 85 consecutive patients has shown 14 % incidence of postoperative psoas weakness and 3.5 % incidence of slight thigh atrophy [1].

Thus, there was a need to develop tools that allow secure lateral access to the lumbar spine, overcoming the disadvantages and preventing iatrogenic neurological injuries. An expandable retractor was developed (NuVasive®, Inc., San Diego, CA) to provide direct visualization of the surrounding structures, improving visibility achieved by endoscopic viewing. To guide the passage through the psoas muscle, an EMG neuromonitoring prevented the blind traverse of the psoas muscle, protecting the integrity of the neural structures. Thereby, the lateral lumbar interbody fusion (LLIF) is defined as a 90-degree lateral, retroperitoneal transpsoas approach to the anterior spinal column, with minimum tissue trauma by use of blunt finger dissection of the retroperitoneal space and tactile guidance of the first dilator to the psoas surface. Figure 1.4 shows the relevant anatomy for lateral access surgery in lumbar spine. The utilization of a split-blade retractor generates a customizable working portal that allows direct visualization, with the opportunity to insert a wider cage implant in comparison to other anterior interbody devices. The bilateral annular release allows the device to reach both sides of apophyseal ring, generating a more stable construction and greatest biomechanical advantage. The technique also permits the restoration of the normal disc and foraminal heights, allowing indirect decompression of the neural structures through an anterior intervertebral fusion, correcting sagittal and coronal alignment, stabilizing the targeted level and facilitating bone ingrowth without the morbidity of open surgeries.

The initial experience in lateral access surgery included less complex surgical indications, like 1- or 2- level interbody fusion for degenerative conditions [5, 41]. As the procedure maintains intact all ligaments that play a role in ligamentotaxis, the slippage reduction in spondylolisthesis [16, 23] and vertebral derotation in degenerative scoliosis [10–12, 42], added to minimal collateral muscle and bone damage, with decreased risks and complications, demonstrated the superiority in several aspects of lateral access surgery over open traditional techniques [43].

The technical and technological advancement have led to the development of different tools and devices, expanding the range of indications. The polyetheretherketone (PEEK) spacers adapts on patient’s necessities, with different width, length, sagittal angle, coronal angle, integrated fixation, like lateral plating that allow supplemental fixation by the same lateral approach, and advancements in working portal, allowing greater safety and effectiveness through better visualization of the targeted structures, minor damage to adjacent tissues, and greater integration with the new instruments. This leads to a more efficient surgery with less risks and complications for patients.

Since it first description, the published literature into lateral access surgery brought to light greater knowledge regarding applications and outcomes of the procedure. This includes dozens of peer-reviewed articles, and hundreds of abstracts and posters presented at the most important scientific meetings all over the world. These scientific evidences have allowed the expansion of surgical applications. Currently, the applications of lateral approach include pseudoarthrosis, discogenic low back pain, degenerative back and leg pain, trauma, infection, tumor, coronal and sagittal alignment, revision, spondylolisthesis, motion preservation, adjacent level disease, and others that require access to the anterior column of the thoracolumbar spine [15, 18, 20, 25, 44–52]. These results will be discussed throughout the book and so are not addressed in this present moment.

There is a continuous need in keeping medical education, maintaining efforts on development and research, and improving individualized patient care. Multicenter studies and data collection are essential for continued validation of new applications. The lateral approach extended the look on various pathologies of the spine, with more safety, effectiveness, and better clinical outcomes besides significant less morbidity. It is imperative that surgeons and medical societies continually assess the value of the care we deliver using methods that allow us to offer to our patients the best quality of care. This is the new environment that we live in, and we must always be up to date about new techniques and technologies and its validation in evidence-based medicine. The lateral access surgery has revolutionized how interbody fusions can be done, and the involvement of the spine surgeons will be critical in the continued advancement of this technique.