History

Anterior approaches to the spine have been used to treat lumbar degenerative disc disease for 70 years. The earliest reports of anterior spine surgery arise from the late 19th century. Tuberculosis of the spine was a significant problem, which often led to paraplegia. Vincent of Paris, in 1892, evacuated a tuberculosis abscess using costotransversectomy.¹ Three years later, the other pioneer of anterior spine surgery, Victor Menard, authenticated the benefits of the anterior approach by performing a posterolateral costotransversectomy for abscess drainage.² The first attempted anterior approach to the lumbar spine was in 1906 by Muller, wherein he used a transperitoneal approach to debride tuberculosis of the lumbar spine.³ Postoperatively, his patient did well; however, subsequent patients had significant morbidities and mortalities, which slowed the progression of the approach. Almost 15 years later, in 1921, Royle used a retroperitoneal approach to remove a congenital hemivertebra in the lumbar spine.⁴ The next year, MacLennon was the first to treat scoliosis in children with an anterior retroperitoneal approach.⁵

During the 1930s, Chaklin performed an anterior retroperitoneal osteotomy of the lumbar spine, while Burns, whom many credit to be the first to perform an anterior fusion of the lumbar spine, used bone grafting to treat lumbar spondylolisthesis via a transperitoneal approach.^6,7 Ito et al. used both an anterior costotransversectomy approach to the thoracic spine to treat Pott’s disease and a retroperitoneal approach to the lumbar spine to perform structural bone grafting.⁸ In 1944, Iwahara treated lumbar degenerative disease by an interbody fusion done using a retroperitoneal approach.⁹ Four years later, Lane and Moore used a transperitoneal approach to treat lumbar degenerative disease.¹⁰ In 1945, Capener described a transperitoneal approach using a tibial allograft graft; in 1959, he modified this approach by removing an additional rib laterally.¹¹ In 1956 and then in 1960, Hodgson and Stock, who were able to successfully eradicate the disease in hundreds of tuberculosis patients, extended the anterior approach to the thoracic and lumbar spine for debridement of tuberculosis abscesses with subsequent interbody fusion.¹² Acceptance of the anterior interbody fusion technique as an efficacious procedure has evolved as one of the predominant techniques to treat discogenic back pain.

Advantages

The anterior approach to the lumbar spine has been shown to have several advantages over posterior approaches. The anterior approach provides direct access to the ventral surface of the vertebral bodies and disc spaces, and it provides a direct and more complete view of the anterior surface of the lumbar spine from L3 to S1.¹³ In addition, the anterior approach avoids dissection through the soft tissue and musculature encountered in the posterior approach, especially the paraspinal muscles. Avoidance of injury to these tissues may result in significantly decreased postoperative pain and subsequently decreased length of postoperative hospital stay.^13,14

Lumbar interbody fusion via the anterior approach has also shown to be advantageous over posterior techniques, such as posterior lumbar interbody fusion (PLIF). One significant advantage is the absence of neural retraction required in the anterior approach, as compared to the degree of retraction required on the neural structures in the PLIF technique.¹⁵ One recent study compared the anterior lumbar interbody fusion (ALIF) technique to the transforaminal lumbar interbody fusion technique and shows an increased ability of ALIF to improve foraminal height, local disc angle, and lumbar lordosis.¹⁶ Other studies have demonstrated decreased rate of adjacent segment degeneration with ALIF compared to PLIF.¹⁷

Indications

The indications for ALIF have increased over the last several years. The most common indication for ALIF is discogenic back pain that occurs between the levels of L3 to S1.^13,18 Another common indication for this procedure is spondylolisthesis, namely, the isthmic and degenerative types.^19,20 ALIF has also been used as revision surgery after a failed posterior fusion involving segments from L3 to S1.^13,21 A secondary indication for anterior fusion is intervertebral foraminal stenosis secondary to loss of disc height,²² in conjunction with the need for interbody fusion.

Contraindications

Several contraindications exist to the ALIF technique. Severe and numerous medical comorbidities pose a relative complication to any major surgical procedure. In addition, severe obesity is a contraindication to the anterior approach, given the hindrance the obesity would have during exposure and retraction of intra-abdominal tissues and structures.

Disease processes and abnormalities of intra-abdominal structures have a significant influence on the risk associated with the anterior approach to the lumbar spine. For instance, significant retroperitoneal scarring due to previous surgery, injury, or infection could severely limit the exposure and therefore increase the risk for injury to the intra-abdominal and retroperitoneal structures during the exposure. The presence of an abdominal aortic aneurysm would also be a contraindication to the anterior approach to the lumbar spine, since a significant amount of retraction is placed on the major vessels. Moreover, severe peripheral vascular disease would be considered a contraindication to this approach due to the potential compromise of already-diseased vasculature. Finally, a solitary kidney on the side of the exposure poses as a risk associated with the anterior approach, since there is a nonzero risk of injury to the ureter.

Contraindications to the ALIF technique exist that are related to the state of the bone and fusion. Spinal infection is a contraindication to interbody fusion, given that a foreign body is being place into infected tissue. Severe osteoporosis is also considered a contraindication. An area of question is the contraindication of stand-alone anterior interbody fusions in potentially unstable segments of the spine. For instance, it is considered that ALIF to treat high-grade spondylolisthesis should require posterior stabilization and fusion.

Preoperative Evaluation

The preoperative evaluation of patients who will undergo ALIF first requires careful selection of those patients likely to have a successful outcome after an anterior fusion. For example, in patients with discogenic pain, the following criteria have been shown to be associated with a good outcome after ALIF¹³: (1) axial back pain aggravated by spinal loading and fusion, (2) radiographic studies consistent with disc degeneration, (3) provocative discography that produces pain only at the affected levels, and (4) dynamic studies demonstrating motion/sagittal deformity on sagittal views.

Careful consideration also needs to be placed on the type of approach used to access the anterior spine. This depends on the patient’s characteristics, as well as the surgeon’s preference. ALIF has three major types of approaches: open, mini-open, and laparoscopic. Each approach has advantages and disadvantages. Open ALIF requires a larger incision and opening into the retroperitoneal space. However, the drawbacks of this approach include increased blood loss during surgery, as well as increased operative time, compared to other approaches.²³

On the other end of the spectrum, the laparoscopic approach to the anterior spine minimizes the size of the incision and dissection into the retroperitoneal space. This technique has been gaining popularity for some time. However, the significant drawback with this approach is the decreased visibility intraoperatively, leading to inadvertent injury to nearby critical structures.

Mini-open anterior lumbar interbody and fusion has gained a great amount of popularity over time and has been the favored technique for approaching the anterior spine for many surgeons. This approach seems to be an optimization between the laparoscopic technique and the open technique in that the incision and dissection are minimized yet visibility is significantly improved compared to that of the laparoscopic approach. This technique is detailed further in the later sections.

Next, the surgeon has to decide whether to approach the anterior spine via a transperitoneal or an extraperitoneal approach. The retroperitoneal approach seems to be the favored approach, given the complications that seem to be associated with the transperitoneal approach. The transperitoneal approach has been shown to have an increased of retrograde ejaculation compared to the retroperitoneal approach by approximately a factor of 10,^23,24 secondary to an increased rate of injury to the hypogastric plexus.²⁵ In addition, the number of levels than can be accessed with the transperitoneal approach is typically decreased. Finally, the transperitoneal approach requires direct manipulation of intra-abdominal contents, including visceral structures. This may lead to an increased rate of postoperative ileus, as well as an increased rate of injury to the intraperitoneal structures.

Careful preoperative assessment must also be made in regard to whether ALIF should also be supplemented with additional posterior fusion. The addition of posterior fusion introduces a second step to the surgery. Since it requires dissection of posterior soft tissues, it counteracts the advantage that anterior lumbar approaches have in avoiding dissection of paraspinal musculature. However, biomechanical studies have shown a significant decrease in the relative motion between segments and a decrease in bone stress level, resulting in higher rates of fusion.²⁶ In cases of isthmic spondylolisthesis, the addition of posterior fusion should strongly be considered, given the inherent instability and motion with isthmic spondylolisthesis. In addition, standalone anterior interbody fusion has been associated with increased incidence of sacral fractures over time.¹⁹ Finally, in cases requiring multilevel fusion, posterior fixation and fusion should be considered.¹⁵

Preoperative imaging should carefully be assessed prior to surgery. Plain radiographs are used to estimate the size and angle of the implant to be used in an effort to achieve optimal postoperative disc height and lordosis. The degree of sagittal imbalance should also be assessed on preoperative imaging, which should be restored.²¹ One study demonstrated that correction of sagittal imbalance, local lumbar lordosis, disc height, and neural foramen led to better overall long-term outcomes.¹⁶