Anterior Spinal Column Reconstruction: Anterior, Lateral, and Oblique Approaches to the Spine



Anterior Spinal Column Reconstruction: Anterior, Lateral, and Oblique Approaches to the Spine


Scott J.B. Nimmons, MD

Andrew E. Park, MD


Dr. Park or an immediate family member has received royalties from Zimmer Biomet Virage posterior cervical system and serves as a paid consultant to or is an employee of Titan Spine, New Era Orthopaedics. Neither Dr. Nimmons nor any immediate family member has received anything of value from or has stock or stock options held in a commercial company or institution related directly or indirectly to the subject of this chapter.



INTRODUCTION

Spinal arthrodesis procedures have been performed for approximately 100 years. During that time many different devices, techniques, and surgical approaches have been used to successfully perform such operations. Even in the setting of historically favorable radiographic and patient-reported outcomes, spinal surgeons seek techniques that may allow higher fusion rates and superior deformity correction and minimize the morbidity of the surgical procedures.

Compared with posterior techniques, anterior and lateral interbody approaches allow for direct stabilization of the anterior column without intraoperative manipulation of the spinal cord or nerve roots. In this way, the risk of postoperative adhesions or iatrogenic neurologic injury is minimized. These surgeries also allow surgeons to decompress nerve roots indirectly by restoring decreased intervertebral body height, thereby opening stenotic neuroforamina. Additionally, anterior and lateral techniques allow the placement of larger interbody devices, which results in greater contact area between the implant and vertebral end plate. Early biomechanical studies suggest this may lead to decreased subsidence. A larger cage also allows for an increased volume of bone graft to be placed, potentially improving fusion rates while also decreasing the likelihood of pseudarthrosis. Within the expanding field of interbody techniques, the focus of this chapter will be on anterior and lateral lumbar interbody fusion techniques.


ANTERIOR LUMBAR INTERBODY FUSION

The anterior lumbar interbody technique for fusion of the lower lumbar spine is being performed with increasing frequency. As surgeons become more familiar and more comfortable with this approach, more clinical scenarios traditionally approached via a posterior surgical technique may be handled with an anterior procedure. Lumbar levels from L2 to the sacrum can be accessed via a single retroperitoneal approach in most instances. The anterior lumbar approach presents significant advantages in long deformity constructs, which extend down to the sacrum or pelvis. The caudal level of long spine reconstructions is more likely to develop a pseudarthrosis. This is particularly true of the L5-S1 level. One significant advantage of the anterior technique is its high fusion rate compared with posterolateral intertransverse fusion. This is particularly true for the L5-S1 level.1,2 In addition, the correction of coronal plane deformity and the graft surface area is substantially greater through an anterior interbody technique.


PATIENT SELECTION





PREOPERATIVE IMAGING

Plain radiographs typically demonstrate height loss on the lateral view (Figure 1). Although instability on flexion-extension views may be coexistent with the degenerative disk, this is relatively uncommon.

The surgeon must beware of spondylolysis affecting the involved motion segment because this may impact the need for additional fixation in the surgical decision making. A vacuum disk sign may also be seen on either standing, recumbent, or flexion-extension radiographs.3,4 MRI changes may include loss of disk space height, loss of signal intensity in the nucleus pulposus of the intervertebral disk on T2-weighted images, posterior disk bulge on axial imaging, and possibly Modic end plate changes affecting the inferior end plate of the superior vertebrae and the superior end plate of the inferior vertebrae (Figure 2). Nerve root compression may also be seen on axial imaging affecting the central canal, the subarticular recess, or the far lateral zone of the neural foramen.5 Other diagnostic maneuvers may include diskography and postdiskography imaging. This area continues to be the subject of considerable debate regarding its utility and relevance to surgical decision making. Diskography also introduces variability in techniques and in interpretation of the results. Even the inclusion of a control level is debated based on the theoretical potential for creating accelerated disk degeneration at the control level.






FIGURE 1 Lateral radiograph shows a loss of disk space height at L5-S1.






FIGURE 2 Sagittal T2-weighted MRI demonstrates typical changes associated with a symptomatic lumbar degenerative disk.






POSTOPERATIVE CARE AND REHABILITATION

Patients may be mobilized either on the day of surgery or the following day with physical therapy. The use of an external brace may be at the discretion of the operating surgeon. Once the patient’s mobility allows, the indwelling Foley catheter may be removed. Following surgery, clear liquids may be started once bowel sounds return. Advancing diet to solid foods is typically allowed with the return of flatus. Most patients with single-level surgery are able to return to a normal diet by postoperative day 1 or 2.


LATERAL LUMBAR INTERBODY FUSION

Lateral lumbar interbody fusion (LLIF) is a minimally invasive spine surgical technique that utilizes laterally based flank incision to access the intervertebral disk by way of the retroperitoneal space.15,16 There are other names for this procedure, such as “transpsoas interbody fusion,” “extreme lateral interbody fusion,” direct lateral interbody fusion, or even “oblique lateral lumbar interbody fusion (OLIF),” but each represents a modification of procedures described by Mayer in 1997, McAfee et al in 1998, Bertagnoli et al in 2003, and Ozgur et al in 2006.15,17 The procedure has generated interest among spine surgeons because of the relative simplicity of the technique and the potential reduction in complications compared with open anterior approaches to the lumbar spine. Along with this enthusiasm, there has been an increase in the number of LLIF procedures performed and a broadening of surgical indications.18


Despite a general lack of long-term, evidence-based literature supporting this rapid acceptance within the field, there are several perceived advantages of LLIF. Firstly, this approach does not require direct entry or violation of the spinal ligamentous structures, the spinal canal, the neuroforamen, or the retraction of nerve roots, allowing for a more atraumatic approach to the spine, the potential for less blood loss, and a more rapid functional recovery for the patient.15,16 Furthermore, the procedure allows for the placement of a larger interbody cage than those placed during transforaminal lumbar interbody fusion (TLIF) or posterior lumbar interbody fusion (PLIF) techniques. It is thought that the larger interbody cage increases stability, with an associated reduction in rates of device subsidence through the accommodation of a greater volume of graft material. Increased density of graft creates a more favorable biomechanical environment for fusion because of increased cage-end plate contact surface area. Additionally, this technique allows for the indirect decompression of neuroforaminal impingement or lateral recess canal stenosis through restoration of intervertebral height.15 More specifically, the placement of wider interbody cages with higher profiles than those used with PLIF or TLIF procedures results in the spanning of the lateral extent of the apophyseal ring bilaterally, an area composed of more structurally sound bone.17 When applying similar criteria to LLIF cases as those applied to anterior interbody fusion procedures, Berjano et al found fusion rates of their cohort to be high, with percentages that fell within previously reported ranges. Based on their classification, 87.1% of operated levels within their cohort were “completely fused,” 10.2% were deemed “stable” or “probably fused,” and only 2.6% of levels had a “pseudarthrosis.”19

Although its use has expanded dramatically over the past decade, surgeons must balance the procedure’s benefits with its drawbacks. This technique (LLIF) is still unfamiliar to many spine surgeons. As such, the orientation of the regional anatomy may be confusing to those surgeons first attempting the technique. Another drawback is the approach-related morbidity to structures surrounding the spine; with dissection of the psoas muscle, there is often postoperative hip flexion pain and weakness.15 There are also limited reports of bowel perforation and ureteral injury related to the surgical approach. Aside from iatrogenic injuries, the approach itself can have practical limitations. The L5-S1 level is considered inaccessible and access to the L4-L5 should be limited to those who have advanced experience with LLIF techniques because of risk of injury to the adjacent lumbar plexus.15

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Feb 2, 2020 | Posted by in ORTHOPEDIC | Comments Off on Anterior Spinal Column Reconstruction: Anterior, Lateral, and Oblique Approaches to the Spine

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