Benefit of Lumbar Fusion for Older Adults
Spinal fusion is a commonly used way to stabilize one or more segments of the spine in older adults. A spinal fusion procedure is also known as a spinal arthrodesis. There are several different ways to perform this operation.

In this article, surgeons from the Norton Leatherman Spine Center in Louisville, Kentucky help us understand how the simplest and most often studied technique (posterolateral spine fusion) is done. It is against this technique that the results of all other methods are compared and judged. Outcomes are measured using patient report of pain and function as well as X-rays of the fusion site.

All patients evaluated had just one spinal level fused. The patients were divided into two groups by age: under age 65 and 65 and older. Everyone was followed at regular intervals for up to two years. The same surgical procedure (posterolateral fusion) was performed on each patient in both age groups.

Patients were placed face down (prone) on a special surgical table called a Wilson frame. This frame can be adjusted to place the spine in the exact amount of curvature (flexion or extension) needed to give the surgeon access to the spine while limiting blood loss as much as possible. A color photo of a sample patient positioned is part of the review.

In layman's terms, the surgeon makes the necessary incision down to the bone, divides the fascia (connective tissue covering the muscles and spine), and cuts the muscles away enough to get to the spine. The surgeon removes the cartilage around the facet (spinal) joint and then removes enough bone along the sides to form a gutter. This depression is where the bone graft will be placed for the fusion.

Screws are used to hold the segments together (one above and one below) until the fusion takes hold. X-rays are used to make sure the screws are in the right spot for optimal stability. Once the screws are in place, additional bone is shaved or cut away, a procedure called decortication. The screws are locked together with a supporting (vertical) rod between the two segments being fused. The final step involves packing the gutters with bone graft material.

It used to be that surgeons would remove some of the patient's own pelvic bone to use as an autograft (bone donated to oneself). But more and more, bone from a bone bank is used supplemented by newer materials that work much better. These newer graft substitutes are made up of bone marrow, bone morphogenetic proteins (growth factors), and even ceramic material.

One final X-ray is taken to make sure everything is in place where it should be before closing the incision. Patients are followed routinely to make sure the graft material fills in and stabilizes the segment.

So how do patients fare after posterolateral spinal fusion based on age? This study showed a major benefit for all patients regardless of age. Older adults (65 and older) seemed to get more pain relief but they also went into the surgery with higher levels of baseline back and leg pain compared to the younger patients.

The authors make a final note to say that lumbar spine fusion using the posterolateral technique isn't for everyone. There are certain indications (reasons to use this method) and contraindications (reasons NOT to use the procedure). For example, this type of fusion works best for patients who have an unstable spinal segment from age-related degenerative disease of the disc, vertebral bones, and/or local scoliosis (curvature of the spine). A local scoliosis affects a small segment of the spine without major deformity.

It should not be used in patients who have a normal disc space height or who have had a previous fusion from behind (posterior fusion). Spinal deformities such as kyphosis (forward curve or rounded spine) will need more than a simple one- or two-level fusion to correct the problem.

Surgeons can expect to see spinal fusion remain an important surgical option to stabilize the spine. The procedure itself hasn't changed much lately. The source of the graft material is probably the biggest change in how the posterolateral technique is performed.

More studies will be needed to see if results are different for patients based on differences in graft material used and number of levels fused -- perhaps combined with other factors such as age as was investigated in this study.
References
Steven D. Glassman, MD, et al. Outcome of Lumbar Arthrodesis in Patients Sixty-five Years of Age or Older. Surgical Technique. In Journal of Bone and Joint Surgery. March 2010. Vol. 92-A. Suppl 1 (Part 1):77-84.