Overview

Anterior lumbar interbody fusion (ALIF) has evolved as one of the predominant surgical techniques for the treatment of diskogenic back pain. Through an anterior retroperitoneal approach, the entire ventral surface of the disk is exposed, making complete diskectomy and subsequent placement of a large intradisk implant straightforward.

Although various surgical techniques have been developed to access the anterior lumbar spine—open retroperitoneal, transperitoneal, endoscopic, and balloon-assisted endoscopic—the mini-open retroperitoneal approach has become the most widely accepted. Mini-open access allows wide exposure of up to three disk spaces from L3–L4 to L5–S1. Furthermore, standard open techniques and instrumentation can be used, allowing for direct manipulation of vascular structures. Surgeon disorientation is also kept to a minimum.

Advantages of an Anterior Approach

Lumbar interbody fusion can be approached from a number of different access corridors: anterior, anterolateral, extreme lateral, transforaminal, and posterior. The anterior retroperitoneal corridor provides the most direct and complete exposure of the disk space. Through this approach, the view is centered in the midline with lateral exposure to either side of the vertebral bodies. This extensive lateral exposure allows for the most extensive disk removal and permits placement of a single-unit implant that nearly matches the vertebral end plate in surface area. The implant enables coverage of a large vertebral body surface area and allows for low nonunion rates, and it minimizes the risk of interbody subsidence. Likewise, restoration of disk height allows for indirect neurologic decompression through expansion of the neural foramen and results in reduction of ligamentous buckling. Although direct neurologic compression is not routinely performed with ALIF techniques, posterior disk herniations and posterior longitudinal ligament (PLL) removal are also possible.

Another major advantage of ALIF is that the technique spares both the posterior spinal musculature and the anterolateral psoas musculature. This results in a reduction of the postoperative pain and disability that frequently accompanies posterior spinal fusions and has also been reported following transpsoas extreme lateral interbody fusions. In addition, because ALIF avoids the extensive stripping of the dorsal soft tissues, the muscle denervation and atrophy implicated in abnormal biomechanics and failed back surgery syndrome are avoided. Likewise, because the psoas muscle is not traversed by the surgical approach, the lumbar plexus is not at risk of injury during the approach or by the retractors. As a result, the ALIF technique can be safely used at levels that may pose increased neurologic risk during an extreme lateral approach (L4–L5) and those that may not be accessible by a lateral approach (L5–S1).

Patient Selection

The surgical treatment of diskogenic back pain remains controversial. Although the intervertebral disk undoubtedly contains nociceptive receptors, the relationship between symptoms of back pain, diagnostic studies, and surgical outcomes remains unclear. Because of the ubiquity of back discomfort and the high incidence of disk abnormalities on magnetic resonance imaging (MRI), strict criteria in selecting patients for surgery remains critical.

Several factors do appear to be predictive of pain relief following lumbar interbody fusion: 1) the history should be consistent with mechanical symptoms of axial pain aggravated by spinal loading and motion; 2) radiographic studies should demonstrate severe disk degeneration localized to discrete levels; 3) provocative diskography should produce concordant pain only at the affected levels and should demonstrate an abnormal nuclear distribution; and 4) abnormal excessive motion on dynamic studies or sagittal deformity are highly predictive of postoperative improvement.

Indications and Contraindications

Operative Technique (Mini-Open Approach)