Posterolateral Spinal Fusion Explained Step-by-Step

A posterolateral spinal fusion surgery takes around 1 to 3 hours, depending on the number of levels fused, the need for additional procedures, and the type of bone graft used.

This surgery is usually done on an outpatient basis, and patients return home the same day.

Preparing for Posterolateral Spinal Fusion

The standard processes conducted ahead of a posterolateral fusion surgery include:

• Reviewing prescription and& over-the-counter (OTC) medications, such as nonsteroidal anti-inflammatory drugs (NSAIDs), anticoagulants, vitamins and supplements, and anti-hypertensive/anti-diabetic medications. Some of these medications are stopped, or the dosage is adjusted one week before the procedure to reduce the risk of complications.
• Scheduling transportation to get home after discharge due to the use of general anesthesia, which causes drowsiness.
• Fasting before the surgery by stopping all food and drink at least 8 hours before the procedure.

Additional requirements are added based on the surgeon’s instructions and preferences. For example, individuals who smoke, vape, chew tobacco, or use any other form of nicotine products may be asked to discontinue usage around a week (or more) before the surgery as the use of these substances impedes fusion healing and increases the risk of complications.

Posterolateral Spinal Fusion Procedure

Before starting the surgery:

• General anesthesia is administered, and the patient is sedated.
• A tube is inserted into the patient’s throat to supplement breathing.
• Intravenous (IV) antibiotics are given.
• Monitors are placed to check heart function, blood pressure, and oxygen levels.

The general procedure for posterolateral spine surgery involves the following steps:

• Incision: The patient lies on his or her stomach, and a 3-inch to 6-inch-long vertical incision is made along the midline of the spine.
• Exposure: The muscles and tissues surrounding the spine are carefully moved aside to expose the vertebrae and the posterolateral space. The large back muscles, such as the erector spinae, that attach to the vertebra’s transverse processes are moved to the side to create a bed to lay the bone graft.
• Placement of graft: Bone graft or a bone graft substitute is placed in the posterolateral gutter.
  • Harvesting bone graft: At this point, if the patient’s own bone is used as the graft for fusion, the surgeon makes a 0.5-inch to 1-inch-long incision on the back of the hip, and cuts or shaves small morsels or chips of bone from the patient’s hip bone (iliac crest). This type of graft is called an iliac autograft.

This step is not needed if a bone graft substitute or graft from a donor (allograft) is used.

• Placement of spinal instrumentation: In some cases, pedicle screws and rods are used to provide additional stability to the fusion.
• Closure: The spinal muscles are laid back over the bone graft – creating tension and covering the graft tightly, keeping it in position. The incision is closed with stitches or surgical staples.

The anesthesia is stopped, and the patient is moved to a recovery room. After the patient wakes up in the recovery room, his or her vital signs are monitored for about 4 to 5 hours.

Discharge Considerations

Most patients can return home the same day. A longer hospital stay may be required for patients with:

• Additional surgical procedures
• Pre-existing bleeding disorders
• Respiratory difficulties after surgery
• Previous lumbar spine surgery in the same area
• Multiple levels of fusion

A comprehensive list of activity restrictions and rehabilitation guidelines are discussed with the patient for optimal recovery after spinal fusion surgery.

See Postoperative Care for Spinal Fusion Surgery

Risks and Complications

As with all types of spinal fusion surgeries, the main concern with this surgery is that it might not fully relieve the patient's pain.

The main cause of ongoing pain and symptoms is the failure of a solid fusion. This condition is called non-union or pseudoarthrosis, and if it becomes painful, further surgery may sometimes be necessary to re-fuse the spine.

Non-union rates between 8% to 43% have been quoted in the medical literature.¹Guppy KH, Royse KE, Norheim EP, et al. Operative Nonunion Rates in Posterolateral Lumbar Fusions: Analysis of a Cohort of 2591 Patients from a National Spine Registry. World Neurosurg. 2021;145:e131-e140. doi:10.1016/j.wneu.2020.09.142 Not all cases of non-union produce painful symptoms, and not all patients who have a non-union will need to have another fusion procedure. As long as the patient's symptoms are better, more back surgery is not necessary.

Non-union rates are higher for patients who have co-occurring spinal conditions and certain types of health problems that may delay healing. Examples include patients who:

• Have had prior lumbar spine surgery
• Have multiple-level spine fusion surgery
• Have weak bones due to bone disorders like osteoporosis
• Have severe or uncontrolled diabetes
• Have been treated with radiation for cancer
• Smoke or use nicotine products
• Are obese

In addition, there is a risk of achieving a successful fusion, but the patient's pain does not subside. Recurrent pain after a successful spine fusion surgery is generally not from the fused level but from other joints.

Additional risks of a posterolateral spinal fusion surgery include:

• Degeneration in the adjacent spinal segment
• Nerve root injury, including dural tear and spinal fluid leak
• Superficial or deep infection at the surgical site
• Excessive bleeding
• Anesthesia-related risks

Posterolateral gutter spinal fusion is a major surgery and warrants a thorough understanding of the potential risks and benefits, as well as post-surgical recovery and rehabilitation.

Read more about Spine Fusion Risks and Complications