What is Fusion Used to Treat?: A Guide to Spinal Surgery and Pharmacology

October 9, 2025 •

4 min read

The annual incidence of lumbar spine fusions increased by 289% between 1997 and 2016 [1.9.5]. But what is fusion used to treat? This surgical procedure primarily addresses spinal instability and pain by permanently joining two or more vertebrae [1.2.3, 1.3.4].

Quick Summary

Surgical fusion permanently joins two or more vertebrae to eliminate painful motion and stabilize the spine. It treats conditions like degenerative disc disease, scoliosis, spinal fractures, and spondylolisthesis when conservative methods fail.

Key Points

What it is: Fusion is a surgical procedure that permanently joins two or more vertebrae to eliminate motion and stabilize the spine [1.3.4].
Primary Conditions Treated: It is used for degenerative disc disease, scoliosis, spondylolisthesis, spinal fractures, and instability when other treatments fail [1.2.1, 1.2.2].
The Goal: The main objective is to reduce pain caused by movement and to correct spinal deformities or instability [1.2.5, 1.3.1].
Role of Pharmacology: Medications are crucial for managing post-operative pain (NSAIDs, opioids), preventing infection, and sometimes promoting bone growth (teriparatide) [1.8.2, 1.8.5].
Success and Recovery: Success rates are high (70-95%), but recovery is lengthy, often taking 6-12 months for the bone to fully fuse [1.5.1, 1.7.2].
Not a First-Line Treatment: Fusion is typically considered only after conservative treatments like physical therapy and injections have proven ineffective [1.2.2, 1.2.5].
Surgical Hardware: Screws, rods, and plates are often used to hold the vertebrae in place while the bone graft heals into a solid mass [1.3.5].

Understanding Medical Fusion: A Surgical Solution

In the medical field, "fusion" almost always refers to a surgical procedure, most commonly spinal fusion, designed to permanently join two or more bones in the spine, called vertebrae [1.2.3, 1.3.4]. The primary goal is to eliminate motion between these bones, which can be a significant source of pain, and to provide stability to a damaged or deformed spinal segment [1.3.1, 1.5.4]. This is achieved by placing bone graft material between the vertebrae, which stimulates the growth of new bone over several months, eventually welding the vertebrae into a single, solid structure [1.3.5]. Surgeons often use hardware like metal plates, screws, and rods to hold the vertebrae together and provide support while the bone graft heals [1.2.4, 1.3.5].

Key Conditions and What is Fusion Used to Treat

Spinal fusion is typically recommended only after more conservative treatments, such as physical therapy or medication, have failed to provide relief [1.2.2]. It is a major surgical intervention aimed at resolving specific, identifiable sources of spinal pain and instability [1.2.5].

Degenerative Disc Disease (DDD)

DDD involves the gradual breakdown of the cushioning discs between vertebrae. As these discs lose height and water content, they can cause pain and spinal instability [1.2.5]. Fusion stabilizes the spine by eliminating the painful motion between the affected vertebrae [1.2.5]. The procedure can also help restore the normal height between vertebrae, relieving pressure on compressed nerves [1.2.5].

Spinal Deformities: Scoliosis and Kyphosis

Scoliosis (a side-to-side curvature) and kyphosis (an abnormal outward curve) are spinal deformities that can progress over time, causing pain, imbalance, and in severe cases, issues with organ function [1.2.5]. Fusion surgery is used to correct the abnormal curvature and then fuse the vertebrae in the corrected position to prevent further progression [1.2.5, 1.3.3].

Spondylolisthesis

This condition occurs when one vertebra slips forward over the vertebra below it, leading to spinal instability and potential nerve compression [1.2.2, 1.3.3]. This misalignment can cause significant lower back and leg pain [1.3.3]. Spinal fusion is performed to realign the vertebrae and stabilize the affected segment, preventing further slippage and alleviating symptoms [1.2.5].

Spinal Fractures, Tumors, or Infections

Traumatic injuries, osteoporosis, spinal tumors, or infections can cause vertebral fractures or weakness, leading to spinal instability [1.3.2, 1.2.3]. In these cases, fusion surgery is used to stabilize the spine, protect the spinal cord and nerves from further damage, and relieve pain [1.3.2].

The Role of Pharmacology in Fusion Surgery

While fusion is a mechanical, surgical procedure, pharmacology plays a critical role in its success. Medications are used before, during, and after the surgery to manage pain, prevent complications, and promote healing.

Pain Management: Complex spinal procedures are associated with intense post-operative pain [1.8.2]. A multimodal approach is used, including pre-operative administration of non-steroidal anti-inflammatory drugs (NSAIDs) or COX-2 inhibitors and paracetamol [1.8.2]. Post-operatively, opioids are often used for rescue analgesia, while muscle relaxants like methocarbamol may be prescribed to manage muscle spasms [1.8.1, 1.8.2, 1.8.4]. Medications like gabapentin may also be used to manage nerve-related sensations as nerves awaken after surgery [1.8.4].
Bone Growth Promotion: In some cases, specific medications are used to enhance the fusion process itself. Anti-osteoporotic agents like teriparatide have been shown to increase the fusion rate [1.8.5]. Bone Morphogenetic Protein (BMP), a synthetic protein, can also be used to stimulate bone growth and has been shown to be effective in achieving solid fusion [1.5.4].
Infection Prevention: As with any surgery, antibiotics are administered to prevent post-operative infections [1.8.2].

Comparison: Surgical Fusion vs. Non-Surgical Alternatives


Treatment Approach	Description	Best For	Considerations
Spinal Fusion Surgery	Permanently joins vertebrae to eliminate motion using bone grafts and hardware [1.2.4].	Severe instability, deformity (scoliosis), spondylolisthesis, fractures, or degenerative pain unresponsive to other treatments [1.2.2, 1.2.5].	Invasive procedure with a long recovery period (up to a year for full recovery) [1.7.5]. Carries risks like nerve damage and infection [1.2.2].
Physical Therapy	Exercises to strengthen core muscles, improve flexibility, and support the spine [1.6.5].	Mild to moderate pain from DDD, minor instability, and post-surgical rehabilitation [1.2.5, 1.6.5].	Requires long-term commitment. May not be sufficient for severe structural problems [1.2.5].
Epidural Steroid Injections	Injects corticosteroids into the epidural space to reduce inflammation and nerve pain [1.6.6].	Radiating nerve pain (sciatica) caused by herniated discs or spinal stenosis [1.6.6].	Provides temporary pain relief, not a permanent fix. Effects can diminish over time [1.6.6].
Artificial Disc Replacement	Replaces a damaged disc with a synthetic device that preserves motion [1.6.2].	Degenerative disc disease in patients who wish to maintain spinal flexibility. An alternative to fusion for some [1.6.2, 1.6.6].	Not suitable for all patients, particularly those with significant instability or facet joint arthritis [1.6.2].

Conclusion

So, what is fusion used to treat? It is a definitive surgical treatment for serious spinal conditions that cause pain and instability, such as degenerative disc disease, scoliosis, and spondylolisthesis, especially when conservative options have been exhausted [1.2.5]. While it has a high success rate, reported between 70% and 95% depending on the procedure, it is a major operation with a significant recovery period [1.5.1, 1.5.2]. The decision to undergo fusion surgery is a personalized one, made in consultation with a surgeon after carefully weighing the potential benefits against the risks [1.2.5]. The procedure is intricately linked with pharmacology, which is essential for managing pain, preventing complications, and ensuring the best possible outcome.

For more information, you can consult authoritative sources like the American Association of Neurological Surgeons.

Frequently Asked Questions

Initial recovery can take 4 to 12 weeks to return to non-strenuous activities, but full recovery and complete bone fusion can take from six months up to a year or more [1.7.1, 1.7.5].

The success rate for spinal fusion is generally high, with reported rates ranging from 70% to over 90%, depending on the specific condition being treated and the surgical technique used [1.5.1, 1.5.2, 1.5.5].

Post-surgery, patients are often prescribed a short course of opioids for severe pain, muscle relaxants for spasms, and may use over-the-counter pain relievers like acetaminophen. Anti-inflammatories like ibuprofen are sometimes avoided initially as they can slow bone healing [1.7.1, 1.8.4].

Most patients can resume driving between 2 to 4 weeks after surgery, but only once they are no longer taking narcotic pain medications and can move comfortably enough to operate a vehicle safely [1.7.2].

Once you have fully healed, there may not be specific restrictions on daily activities. However, surgeons often advise avoiding high-impact sports or activities that place extreme stress on the spine to protect the fused area and adjacent levels [1.7.2].

The surgery itself is performed under anesthesia. Post-operative pain is expected and can be intense initially, but it is managed with a combination of medications. This surgical pain typically subsides significantly within four weeks [1.7.1, 1.8.2].

Alternatives depend on the condition but include physical therapy, epidural steroid injections, artificial disc replacement, laminectomy (decompression surgery), and dynamic stabilization devices [1.6.1, 1.6.6].