Lumbar Fusion Case Examples
This illustrative case involves a 52 yr. old male with chronic severe low back pain that has failed to respond to conservative (non-operative treatment), including medications, therapy, and injections. After discussion of the options and explanation of the risks, the patient decided to proceed with surgery.
On the lateral (side) view of the pre-op MRI, note the normal appearing discs between L1 and L4, marked with white asterisk. The discs between L4 and S1, marked by the dark arrowhead, are not normal appearing. While the disc at L5-S1 is clearly flattened, the disc at L4-5 has a bulge at the back and does not have the same white signal as the normal discs above.
The decision was made to include the L4-5 disc in the fusion since, after fusing L5-S1, the stress would be concentrated on the next level (L4-5), which in this case, already shows signs of wear and tear.
One month after surgery, the interbody spacers, which are invisible to X-ray except for the metal markers in them, can be seen below in the interspaces between the vertebral bodies.
The patient’s back pain was significantly better by about 6 weeks.
Seven months after surgery, the patient is feeling much better. On the lateral (side) view X-ray below, some calcification (whiteness) can be seen in the interspaces. This finding, however, is subtle.
By checking the patient with a CT scan, however, the bony healing between the vertebral bodies can be demonstrated on the reconstructed views.
The patient was released to his regular duty at 8 months post op. However, since he has two less discs in his spine (four discs doing the job of six), he is still advised to avoid frequent bending, lifting, and twisting.
On the lateral X-ray at one year post op, more calcification can be seen between the vertebral bodies as indicated by the asterisk.
The patient continues to do well.
Here’s an example of another patient who at one year after a two level fusion had a solid bony connection.
Nonunion with Hardware Loosening
However, below is an example of a case where, despite proper technique, with no complications, the fusion did not occur. This result is also referred to as a nonunion or pseudarthrosis (if you see that term). Although bone is growing from above and below within the spacer, it never connected. The patient didn't do anything wrong. Sometimes a nonunion can occur.
X-ray Findings with Nonunion
On those occasions where a nonunion occurs, the screws will eventually become loose. In the X-ray below, you can see that the two lowest screws have a dark line around them that is referred to as a “halo.”
When the surgery is performed, there is a race that starts: either the fusion will fuse, aided by the stability provided by the hardware, or the fusion does not occur, in which case the hardware (screws) will eventually get loose.
Although the screw has good fixation in the bone (referred to as "purchase") when initially placed, when a nonunion occurs, not only are there clinical signs (patient having more pain), but there are also X-ray findings. When a screw starts to get loose, it will to a small degree compress the bone around the screw to form the halo appearance. In the x-ray below, the screws higher in the spine, which are not loose, do not have the halo.
This images below are from a CT scan, taken from a different patient, and show the X-ray appearance of screws when they become loose. This loosening is demonstrated by the dark line around the screws (the halo) which indicate that the screw threads have no purchase or bite into the bone.
Ectopic (Extra) Bone Formation
Here is a case where extra bone grew near and in the foramen, which is the opening through which the nerve root exits the spinal column.
In this case, while the patient might be expected to have pain along the area supplied by the involved nerve root, the patient had no symptoms. This situation shows why the focus is on treating the patient, not the X-ray.
