When instability or deformity runs across more than one lumbar level, the segments are decompressed and joined together into a single stable column. This is the largest operation described on this site, and the aim is not simply to fuse the spine — it is to fuse it in the right shape, so the patient stands upright without having to work at it.
A single-level fusion treats one worn-out joint. A multilevel fusion treats a spine that has stopped holding its own shape — several segments that have slipped, tilted or collapsed, so that the problem is no longer one painful level but the column they add up to.
The operation has three parts, and all three matter. The nerves are decompressed wherever they are being squeezed. The segments are realigned, which is the part patients rarely hear about and the part that most determines how they feel a year later. And the whole construct is held with screws and rods while the bone grows across and makes it permanent.
The hardware is not the fusion. It is the scaffold that keeps everything still and in the right position for the months it takes the bone to knit — the biology does the actual work.
Multilevel instrumented lumbar fusion. Posterior and lateral views of a multi-segment construct with pedicle screws and contoured rods, interbody cages at the treated levels, and the restored lumbar lordosis shown against the pre-operative alignment.
Patterns where the instability or the deformity is the disease, rather than a single level being worn.
A recognisable version of this is the patient who can stand straight for a few minutes and then has to hold onto something, or who notices they are looking at the ground when they walk. That is the spine no longer carrying its own balance, and the muscles doing the job instead until they tire.
A healthy lower back curves forward. That curve is what balances the head and torso over the pelvis, so standing upright costs almost nothing in muscular effort. As discs collapse at several levels the curve flattens, the torso drifts forward, and staying upright becomes work the muscles have to do all day.
This is why a multilevel fusion is planned on standing full-length X-rays rather than on an MRI. The MRI shows what is compressing the nerves; the standing films show the shape of the column and where the body has compensated — a pelvis rotated back, knees slightly bent, a thoracic spine flattened to make up for the lumbar spine.
A construct that fuses the levels but leaves the spine flat locks in the very posture the patient came in with. Rods are contoured, interbody cages are chosen for the lordosis they hold, and releases are made where the spine will not otherwise move — all so the fusion sets in the shape a spine is supposed to have.
Every additional level costs something real: more operating time, more blood loss, more of the lumbar spine that no longer moves, and more load transferred to the segments at either end of the construct. Those end segments are where adjacent segment disease shows up years later.
So the length is not decided by how much of the spine looks worn on the scan. Plenty of degeneration is visible on imaging and silent in life. The construct spans the levels that are unstable, that are deformed, or that have to be crossed to end the fusion somewhere sound — and stops there.
Where the fusion ends is a deliberate decision rather than a consequence of where the disease appears to stop. Ending on a level that is itself unstable is one of the recognised ways a long fusion fails.
Standing full-length films, flexion and extension views, MRI and usually CT. The alignment targets and the intended top and bottom of the construct are decided before the day of surgery, not during it.
Prone on a frame that lets the abdomen hang free and allows the lordosis to be set by the table. An intraoperative CT is taken and registered so that navigation is working from this spine in this position.
The nerves are freed at every level that is compressing them — centrally, in the lateral recesses, and out through the foramina. Because the levels are being fused, the joints can be taken as far as the decompression requires.
At levels where height and lordosis have to be restored, the disc is removed and a cage is placed. This is where most of the correction comes from, and it also puts graft in the disc space, which is the most reliable place for a fusion to take.
Pedicle screws are placed under CT-based navigation, and with robotic guidance where it suits the case — the trajectory is planned on the images and the guide is held to it, which matters most in the rotated, scoliotic anatomy where landmarks are least reliable.
Rods contoured to the planned alignment are seated and the correction is brought about against them. Bone graft is laid along the decorticated surfaces to fuse. Final imaging confirms every screw and the alignment achieved before closing.
Spinal cord and nerve monitoring runs throughout. In a case where alignment is being changed across several levels, the monitoring is what confirms the correction is being tolerated as it is applied rather than afterwards.
Multilevel instrumented fusion. Navigated screw placement across a rotated segment, interbody cages restoring height and lordosis, and the correction brought about against contoured rods.
A multilevel fusion is a major operation, and it is chosen when the alternative is worse rather than because more surgery is better surgery. What that means practically:
None of this argues against the operation where it is indicated. It argues for being certain that it is.
Figures are general ranges from the surgical literature, not guarantees for any individual case. Recovery after a multilevel fusion varies more between patients than after any other operation on this site, because the constructs themselves vary so widely — two levels and seven levels are both described by this page. Follow the instructions you are given after your own operation rather than these.
Whether this is the operation, and how much of the spine it would need to span, is decided on standing full-length X-rays alongside the MRI. Bring any imaging and any operative reports from previous spine surgery.