Anterior lumbar interbody fusion—advances in spinal fusion technology

AORN Journal, Nov, 2005 by Sharon Brady, Sarah Jackson

As much as 80% of the US population will be affected by back pain at some time during their lives. (1) Some of the causes of low back pain are

* aging (ie, normal wear and tear on the vertebrae and discs);

* injury or trauma;

* infection; and

* tumor.

According to injury statistics from the US Bureau of Labor Statistics, there were 303,750 work-related back injuries in 2003. (2) The aging process itself can lead to back pain that may require treatment and surgery, and because people today are living longer, the number of patients with back pain increases every year. Members of the Baby Boom generation will be the largest population of older adults in history who may require joint and back treatment or surgery. (3)

Factors leading to back pain at any age are related to the anatomy of the lumbar spine that consists of five vertebrae located in the lowest portion of the spine. The natural shape of the lumbar spine is a lordotic curve that looks like a backwards C. The location of the lumbar vertebrae makes them more likely to be injured because the major work of the back (eg, lifting, carrying) is accomplished using the lumbar spine. This results in injuries involving disc herniation. Movement of discs or spondylosis also will occur more frequently at this level than at other levels.

Conservative treatment for back pain may include rest, use of anti-inflammatory medications, and physical therapy. After a patient has undergone conservative treatment for at least six months with poor results, he or she may decide to pursue surgical intervention for pain. Spinal fusion is one of the most commonly performed procedures for degenerative disorders of the lumbar spine. (4)

The surgeon determines whether to perform spinal fusion surgery based on the patient's symptoms and diagnosis and failure of conservative treatment. A magnetic resonance imaging (MRI) scan, myelogram, or computed axial tomography (CAT) scan, and sometimes, an electromyograph (EMG) are performed to diagnose the specific problem. Some of the most common disorders are herniated disc, degenerative disc disease, degenerative spondylolisthesis, spinal stenosis, and revision of previously failed low back surgery.

More than 10,000 anterior lumbar interbody fusions have been performed in the United States in the past 10 years. (5) These procedures have resulted in effective management of degenerative joint disease, instability, and spondylolisthesis, with approximately an 87% patient satisfaction rate. (5) The greatest advantage of anterior lumbar surgery is that back muscles and nerves are undisturbed, so recovery time is shorter compared to recovery for surgery that requires a posterior approach. Secondly, the fusion area is in the front of the spine where it is compressed, which tends to produce better fusion results. If the fusion becomes solid, the patient has a better chance of a permanent recovery without requiring reoperation.

PREOPERATIVE PREPARATION

After the patient is examined and a thorough history and physical is obtained, the surgeon discusses the findings with the patient. The surgeon explains options, benefits, risks, and complications and obtains informed consent. Possible risks and complications include

* bleeding complications (eg, injury to vessels could cause loss of function in one or both legs);

* bowel obstruction that could require reoperation;

* hardware fracture;

* implant migration;

* infection;

* persistent pain;

* pseudoarthrosis (ie, a failure to fuse);

* respiratory complications associated with anesthesia administration;

* sexual dysfunction in men (eg, retrograde ejaculation);

* spinal cord injury;

* sympathetic dysfunction (ie, a feeling of warmth or uncomfortable sensations in one or both legs);

* transitional syndrome (ie, increased stress on the discs above and below the fused level that may cause disc degeneration and pain); and

* thrombophlebitis and deep vein thrombosis. (6,7)

The surgeon or nurse discusses preoperative preparation and the surgical environment with the patient and his or her family members. The vascular surgeon who will open the abdomen and provide access to the spine for the orthopedic surgeon obtains informed consent and answers questions about the procedure. During a preoperative clinic visit, an anesthesia staff member discusses the patient's anesthesia options and answers questions regarding postoperative pain control methods. Laboratory tests are performed within a week before surgery and might include a complete blood count, electrolyte levels, blood typing and cross match, and coagulation tests. In addition, a 12-lead electrocardiogram (ECG) and chest x-ray may be performed if the patient's age (ie, older than age 35) or medical condition (eg, a past history of heart problems) warrants it. Female patients of childbearing age will take a pregnancy test.

DAY OF SURGERY

The patient is admitted to the same day surgery center on the day of surgery. The preoperative nurse monitors the patient's vital signs (eg, blood pressure, oxygen saturation) and ECG. The nurse places an IV line and prepares the IV antibiotics for administration along with other preoperative medications. Antibiotics for spinal fusion surgery include cefazolin 1 g, vancomycin 1 g, and ceftazidime 1 g. The patient will receive one or more of these medications depending on his or her size, medication allergies, and medical history.