Posterolateral fusion is a surgical procedure designed to stabilize sections of the spine by encouraging bones to grow together. This technique involves placing bone graft material in the back and side regions of the vertebrae, aiming to create a solid bone bridge. The purpose of this surgery is to eliminate painful motion between vertebrae and restore spinal stability.
Conditions Leading to Posterolateral Fusion
Posterolateral fusion is considered when non-surgical treatments have not alleviated symptoms caused by specific spinal conditions. One common reason for this procedure is degenerative disc disease, where the discs between vertebrae break down, leading to inflammation and bone-on-bone rubbing. Spinal instability can also necessitate fusion, as symptoms like pain, numbness, or muscle weakness may arise from vertebrae that move excessively.
Spondylolisthesis, a condition where one vertebra slips forward over another, is an indication for posterolateral fusion. This slippage can pinch nerves, causing pain that radiates into the legs and feet. Spinal stenosis, a narrowing of the spinal canal that puts pressure on the spinal cord and nerves, may also be addressed with this surgery. Spinal deformities like scoliosis or spinal fractures can also necessitate posterolateral fusion to restore alignment and stability.
The Surgical Process
The posterolateral fusion procedure begins with the patient positioned on their stomach. A surgeon makes an incision along the midline of the lower back. The muscles surrounding the spine are carefully moved aside to expose the vertebrae and the posterolateral area.
In some cases, a laminectomy may be performed, which involves removing part or all of the lamina, the bone covering the spinal cord, to relieve pressure on nerve roots. The bone surfaces, such as the transverse processes, are then prepared by decortication to promote bone growth. Bone graft material, which can be autograft (from the patient’s own body), allograft (from a donor), or synthetic, is then placed in the posterolateral gutters between the transverse processes.
Instrumentation, such as titanium screws and rods, is often used to provide immediate stability to the spine while the bone graft heals. For multi-level fusions, the number of screws and rods increases accordingly. The surgeon then repositions the muscles over the bone graft, and the incision is closed with stitches or staples.
Post-Surgery Recovery
Immediately following posterolateral fusion surgery, patients remain in the hospital for a few days for monitoring and initial recovery. Pain management is an important aspect of this period, often involving prescribed medications. Early mobilization, such as gentle walking with assistance, is encouraged as soon as the patient is ready to enhance circulation and reduce the risk of blood clots.
During the first few weeks, activity is restricted to allow the spine to heal and the bone graft to fuse. Patients are advised to avoid bending, heavy lifting, or twisting at the spine. Wound care is also important during this time. Physical therapy begins between 6 and 12 weeks post-surgery, focusing on safe walking and gentle stretching, gradually progressing to rebuilding strength. Full recovery, with a return to all usual activities, can take several months, up to a year, as bone growth is a slow process.
Potential Risks and Long-Term Outlook
As with any surgical procedure, posterolateral fusion carries potential risks. These can include infection at the surgical site, bleeding, and nerve damage. A specific complication is non-union, where the bones fail to fuse, which may necessitate an additional surgery. Issues with the implanted hardware, such as screws or rods loosening, can also occur.
The long-term outlook for patients undergoing posterolateral fusion involves improvements in pain and function, though individual outcomes vary. A long-term consideration is adjacent segment disease (ASD), where degeneration occurs in the spinal segments directly next to the fused vertebrae. This can manifest as disc herniation or spinal stenosis in these neighboring areas due to altered biomechanics, as the unfused segments compensate for the loss of motion in the fused area. Studies suggest that adjacent segment disease can lead to symptomatic degeneration requiring further surgery, though research on its exact incidence and causes varies.