The anterior approach to the spine has been around since the 1950s. Originally, the surgery involved a large abdominal incision in which the surgeon would cut through the abdominal muscles and the peritoneal cavity to gain access to the spine. The peritoneal cavity contains the patient’s intestines. This would require long recovery times due to the large dissection of the abdomen and muscles to get access to the spine.
Today, however, the anterior approach to lumbar spine fusion (or other spine surgery, such as the artificial disc) can be done with a minimally invasive approach, involving the following steps:
- A relatively small incision (around 3-5 inches) is made for a single level fusion surgery. This incision is normally 4 to 5 inches below the belly button and usually is low enough to be covered by the patient’s pants, especially if a lower lumbar disc level (such as L5-S1) is being fused.
- A retroperitoneal (behind the peritoneum—the membrane that lines the abdomen) muscle sparing approach is typically done, which means that the front abdominal muscles are gently moved to the side and not cut and the peritoneal cavity is not entered.
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- The peritoneal cavity is moved to the side so that it is out of the way to allow for access to the midline spinal column. The anatomy of the abdomen is really a “bag within a bag” and the inner bag that holds the intestines is not entered.
- Directly in front of the vertebral bodies of the spine are large blood vessels that bring blood back and forth to the legs. Depending on the level of the disc, some of these vessels may need to be gently retracted to allow for access to the disc space. Because of the risks and special skills involved with manipulating blood vessels, a vascular surgeon or general surgeon is required to assist with the anterior approaches to help gain exposure to the disc.
Once the disc space is exposed, the degenerated disc itself is removed, and disc material that is bulging on the nerve roots can carefully be eliminated. At this point, the disc space can be restored to its native height, which will decompress the nerve roots indirectly in the foramen space, and also help regain any lordosis of the spine. A structural bone graft, cage, total disc replacement, or other device would then be placed into the empty disc space.
Potential Risks and Complications Unique to the Anterior Approach
As with all surgical procedures, the anterior approach to spine fusion carries with it a few risks and potential complications that are unique to this surgical approach.
- Blood vessel injury. The incidence of injury to the large blood vessels is very small, typically being around 1-2%. To minimize this risk, a vascular surgeon (or general surgeon with the appropriate skills and training) should be involved in the surgery to manipulate the large blood vessels to help the spine surgeon gain access to the front of the spine.
- Retrograde ejaculation. For male patients, a rare complication (< 1%) from the anterior approach to spine surgery is retrograde ejaculation. At the lower end of the lumbar spine, there is a group of small nerves which can lie over the lowest disc space (L5-S1). These nerves help control a valve needed to express semen, and instead the semen goes up into the bladder after ejaculation. The nerves do not have any effect on erectile function, which is controlled separately by a different set of nerves. In the majority of patients who experience this complication, the condition resolves by itself within 3 to 6 months, but if necessary, an urologist can be consulted to help with fertility. If the retrograde ejaculation becomes permanent, the patient may be unable to have children (without medical intervention from a fertility expert) but will otherwise have normal sexual function.
The other risks and potential complications associated with the anterior approach to spine surgery are similar problems that one would encounter with a posterior spinal surgery, such as infection, and are not unique to the anterior approach. Infection is very rare. There is an excellent blood supply to the area.
Non-unions can occur, but done properly one should expect a 90-95% fusion rate for patients. Pain relief in patients with degenerative disc disease varies, but it has been reported to be effective for pain relief in between 60% - 90% of patients.