A lumbar fusion done from the front, through the abdomen, so the back muscles are not disturbed. The disc is removed completely and a large graft is placed directly against the endplates. This gives the largest graft of any approach and the best restoration of lost disc height and the natural curve of the lower back.
ALIF: Anterior Lumbar Interbody Fusion. Licensed patient-education animation, ViewMedica.
Reaching a lumbar disc from behind means working around the nerves, which lie between the surgeon and the disc, so the graft has to fit through a small window beside them. From the front, the nerves are on the far side of the disc. No nerves are moved aside, and the whole width of the disc is exposed.
This has two benefits. The disc can be removed completely, including the front portion that cannot be reached from behind, which leaves more bone surface for the fusion. And the graft can be as large as the disc space itself, resting on the dense bone around the rim of the vertebra instead of the softer bone in the middle.
A tall graft placed at the front of the disc space props the front of the segment open, which restores the forward curve of the lower back.
ALIF construct at L5–S1. Lateral view of the anterior interbody graft seated against prepared endplates, showing restored disc height and segmental lordosis, with the foramen opened compared with the collapsed pre-operative state.
It is chosen when the operation needs to restore height and alignment as well as stability, and especially often at the bottom of the lumbar spine.
The bottom disc of the lumbar spine sits deep in the pelvis, tipped steeply forward. The iliac crest blocks the way from the side, which is why a lateral approach cannot reach L5–S1 at all. From behind it can be reached, but restoring the curve is harder because the graft goes in from the back of a space that needs propping open at the front.
From the front, the steep angle helps: the disc faces the surgeon almost squarely, and the large blood vessels usually divide above it, leaving a natural window onto the disc. L5–S1 is the level ALIF suits best.
This is why a fusion over several levels is sometimes done through two approaches: from the side for the levels above, and from the front for L5–S1.
The route to the front of the lumbar spine passes behind the abdominal cavity, so the bowel is moved aside without being opened. Directly over the disc lie the body’s largest blood vessels: the aorta, the vena cava and the iliac vessels they divide into. These have to be moved carefully to one side to expose the disc.
For that reason the approach is usually done with an access surgeon, a vascular or general surgeon who opens the way and protects the vessels while the spine surgeon does the fusion, then closes afterwards. Having two surgeons is the standard arrangement for this operation and is a safety measure.
The same level, reached from opposite directions. MIS TLIF is the more commonly performed of the two.
Dr. Zaidi performs both, and both are minimally invasive: neither strips the back muscles the way an open posterior fusion does. Where the canal itself needs opening, a decompression from behind is needed as well, because ALIF alone cannot do it. See how the approach is chosen.
The patient lies on their back. Imaging confirms the level and the working angle onto the disc before the incision.
A short transverse incision low on the abdomen. The surgeon works behind the abdominal cavity, moving the bowel aside without entering it, and the great vessels are identified and gently moved to expose the disc.
The disc is removed across its full width and depth, including the front portion that cannot be reached from behind. The endplates are prepared back to bleeding bone without breaking through the strong plate that will carry the graft.
Trials establish the height that opens the foramina and the angle that restores the segment’s lordosis. The chosen implant, packed with graft, is seated against the rim of the endplates where the bone is strongest.
The construct is secured with screws through the implant into the vertebrae above and below, or with pedicle screws placed from behind, depending on stability, bone quality and what is being corrected.
The vessels are returned to their position and confirmed to be pulsatile and intact, and the abdominal wall is closed in layers.
Anterior lumbar interbody fusion. The retroperitoneal corridor, the great vessels mobilized, complete discectomy and endplate preparation, and a lordotic implant seated at the front of the disc space with height and curve restored.
Every fusion shares the general risks of surgery. Two belong to this corridor specifically and are discussed as part of consent:
Figures are general ranges from the surgical literature and cannot be guaranteed for any one person. Recovery is different from a fusion done from behind: the back itself is fairly comfortable early on, while the abdomen takes a few days to settle and lifting is restricted while the abdominal wall heals. Always follow the instructions you are given after your own operation.
Whether the front is the right approach for your level depends on what needs restoring as well as what needs stabilizing. Please bring any MRI or CT you already have.