How Does Scoliosis Surgery Work? A Look at the Procedure

Scoliosis surgery straightens an abnormally curved spine by repositioning the vertebrae, locking them in place with metal hardware, and fusing the bone so the correction holds permanently. The most common version, posterior spinal fusion, involves anchoring screws into the vertebrae from the back, connecting them with rods, and packing bone graft material around the construct so the treated segments grow together into a single, solid block of bone. The procedure has evolved considerably over the past two decades, with pedicle screws replacing older hook-and-wire systems and newer technologies like robotic navigation and growth-friendly implants expanding what surgeons can offer different patient groups.

When Surgery Is Recommended

Not every scoliosis curve needs an operation. Surgery is generally considered when a curve reaches about 45 to 50 degrees as measured on a standing X-ray, because curves above that threshold tend to keep progressing even after a person has finished growing. Curves beyond roughly 60 degrees begin to compress the lungs and reduce breathing capacity, and very large curves can eventually cause respiratory failure.¹ A large study of over 4,200 adolescent idiopathic scoliosis cases found that the median curve size at the time of fusion was 55 degrees for thoracic (mid-back) curves and 51 degrees for lumbar (lower-back) curves, though some patients were offered surgery below 50 degrees depending on factors like skeletal maturity, curve location, and sex.²

The decision also weighs the patient’s age and growth remaining, pain, cosmetic concerns, and how the curve affects daily life. A 14-year-old with a 48-degree curve that is still progressing faces a very different calculus than a 50-year-old with a stiff 55-degree curve. For adolescents, the main worry is future progression and its consequences. For adults, chronic pain and declining function tend to be the driving reasons. Conservative approaches like specialized exercises have shown benefits for smaller or moderate curves, but once a curve is large enough and rigid enough, bracing and physical therapy cannot reverse it.³

Posterior Spinal Fusion Step by Step

Posterior spinal fusion from the back of the spine has become the dominant technique at most centers worldwide, largely because pedicle screws give the surgeon powerful, three-dimensional control over each vertebra.⁴ Here is what happens in practice:

After general anesthesia, the patient lies face down on a specialized operating table. The surgeon makes a long incision along the midline of the back, exposing the vertebrae that need correction. At each vertebra included in the construct, screws are placed into the pedicles, the thick columns of bone that connect the back of the vertebra to its body. These screws serve as anchor points. Once all the screws are seated, the surgeon threads one or two contoured metal rods through their heads. By carefully rotating the rods and tightening the connections, the surgeon gradually pulls the curved vertebrae into a straighter alignment. Additional maneuvers like compression, distraction, or direct vertebral rotation fine-tune the correction.

With the spine repositioned, the surgeon prepares the bone surfaces by removing the outer cortex and packing bone graft material along the exposed areas. The graft can come from the patient’s own pelvis, from a bone bank donor, or increasingly from synthetic substitutes. One study compared a synthetic calcium phosphate ceramic to traditional pelvic bone graft in teenagers undergoing fusion and found that the ceramic incorporated successfully within a year, with equivalent correction maintained in both groups, eliminating the need to harvest bone from the pelvis.⁵ Over the following months, the graft material and native bone slowly knit together, turning the instrumented vertebrae into a single fused mass. The rods and screws remain in place permanently, though it is the bone fusion itself that provides lasting stability.

How Surgeons Protect the Spinal Cord

Repositioning vertebrae that sit millimeters from the spinal cord is inherently high-stakes. The field has developed several overlapping safeguards to minimize the risk of neurological damage.

Intraoperative neuromonitoring has become standard practice during scoliosis surgery. Small electrodes track electrical signals traveling through the spinal cord and peripheral nerves in real time while the surgeon works. If a correction maneuver starts to compromise nerve function, the monitoring team detects signal changes and alerts the surgical team, who can back off or adjust before permanent damage occurs.⁶ The Scoliosis Research Society considers this monitoring the standard of care whenever the spinal cord is at risk.⁷

Screw placement accuracy is another major safety concern, because a misplaced pedicle screw can breach into the spinal canal or compress a nerve root. Traditional freehand placement relies on the surgeon’s feel and anatomical landmarks, sometimes supplemented by fluoroscopy. Robotic-assisted navigation systems and intraoperative 3D imaging have improved accuracy. A meta-analysis comparing robotic-assisted to freehand screw placement found that robots produced a significantly higher rate of clinically acceptable screw positions.⁸ A separate study comparing robotic navigation, O-arm navigation, and freehand techniques found postoperative accuracy rates of about 97%, 93%, and 80% respectively.⁹ Robotic navigation does not yet achieve a higher rate of “perfect” screw positions compared to freehand, but it significantly reduces the number of screws that end up in unacceptable positions, which is the more clinically meaningful measure.

3D-printed spine models have also entered preoperative planning. Surgeons can now hold a physical replica of a patient’s individual deformity, rehearse screw trajectories, and anticipate anatomical surprises before making an incision. A scoping review found that 3D printing was associated with improvements in screw placement accuracy, shorter operative times, reduced blood loss, and lower fluoroscopy exposure in several comparative studies.¹⁰ For complex adolescent scoliosis cases, patient-specific 3D models have demonstrated accuracy within half a millimeter for practicing screw placements.¹¹

Managing Blood Loss

Scoliosis surgery involves stripping muscle from long sections of the spine, and blood loss can be substantial. The surgical area is wide, which leads to more bleeding than smaller spine operations, and some blood loss is hidden in tissues rather than collected in suction canisters. A large retrospective study of 765 adolescent cases found that this hidden blood loss was a significant contributor and that tranexamic acid, an anti-clotting drug given intravenously during surgery, was associated with lower hidden blood loss.¹²

Cell salvage, a technique where blood lost during surgery is collected, washed, and returned to the patient, has also become increasingly common. While cell salvage does not reduce the total amount of bleeding, it does reduce the need for donor blood transfusions.¹³ Together, tranexamic acid and cell salvage have shifted the field away from heavy reliance on banked blood, which matters because donor blood transfusion itself was identified as an independent risk factor for hidden blood loss in corrective scoliosis surgery.

What Changes for Adults Versus Adolescents

Surgeons use the same fundamental approach for both age groups, but the stiffness and degeneration of an adult spine make the procedure harder. A meta-analysis comparing outcomes in adolescents versus adults found that adolescents achieved about 68% Cobb angle correction on average compared to roughly 61% in adults, a statistically significant gap.¹⁴ Operative time, blood loss, the number of vertebrae instrumented, and hospital stay were not significantly different between the two groups, and complication rates for neurological injury and hardware problems were also comparable. The correction gap likely reflects the fact that adult spines are less flexible, not that the procedure itself is less well performed.

Adults also face a second layer of surgical complexity: sagittal balance. This refers to the front-to-back alignment of the spine, specifically whether the body’s center of gravity falls in the right place relative to the pelvis. In adolescents, sagittal balance is usually reasonable and surgery focuses primarily on correcting the side-to-side curve. In adults with long-standing scoliosis, the spine often develops a forward tilt, and restoring that balance becomes just as important as correcting the lateral curve. Failure to restore sagittal alignment is one of the strongest predictors of poor outcomes after surgery, including persistent pain and disability.¹⁵

Osteotomies for Stiff or Severe Curves

When a curve is too rigid to correct with rod rotation alone, surgeons use osteotomies, controlled cuts through bone, to loosen the spine enough to reposition it. These range in aggressiveness. A Smith-Petersen osteotomy removes the facet joints and posterior ligaments to hinge the spine open through the disc space. A pedicle subtraction osteotomy goes further, removing a triangular wedge of the vertebral body to allow the spine to shorten from the back. And a vertebral column resection, the most extreme version, removes an entire vertebra and surrounding disc material to permit correction of the sharpest, most rigid deformities.¹⁶

The choice of osteotomy depends on the curve’s shape and rigidity. Gently rounded deformities can often be managed with an anterior release to loosen the apex and then posterior instrumentation. Sharp, angular deformities resist anterior loosening and are better addressed with a posterior vertebral column resection.¹⁷ These osteotomies are powerful but carry higher complication risks. Rod fracture rates are considerably higher after pedicle subtraction osteotomy than after simpler techniques, and constructs that span multiple spinal junctions or require rods bent to extreme angles are at greater risk of hardware failure.¹⁸ In a large study of 526 adult deformity patients fused to the sacrum, rod fracture occurred in about 18% of cases, with larger preoperative imbalance and more levels fused identified as risk factors.¹⁹

Fusion-Free Options for Growing Patients

Fusing the spine of a young child would freeze the growth of the treated segments and leave the torso disproportionately short. Two categories of implant work around this.

Magnetic controlled growth rods (MCGRs) are placed surgically with anchor points at the top and bottom of the curve but no fusion in between. The rods contain a small internal magnet that can be lengthened from outside the body using a handheld remote controller, allowing periodic distraction without repeat surgery.²⁰ A study following patients for at least four years found that the average preoperative curve of 60 degrees was reduced to about 42 degrees after implantation, with an average of roughly 14 lengthening sessions over the follow-up period.²¹ Older traditional growing rods required a return to the operating room every six to eight months for manual lengthening, so the magnetic versions represent a meaningful quality-of-life improvement for young patients and their families, even though they come with their own complications including rod breakage and mechanism failure.²²

Anterior vertebral body tethering (VBT) takes a completely different approach. Rather than rods and screws from the back, the surgeon places screws into the sides of the vertebral bodies through a minimally invasive approach from the side of the chest. A flexible cord connects the screws along the convex (outer) side of the curve. Tightening this cord immediately pulls the curve partly straight, and then as the child grows, the tether restrains growth on the convex side while allowing the concave side to catch up, producing ongoing, gradual correction.²³ Because VBT does not fuse any vertebrae, it preserves spinal motion, which is its main appeal. The trade-off is that it only works in patients who still have significant growth remaining, and there is a risk of overcorrection or tether breakage that may require additional procedures.

Recovery and Pain Management

Hospital stays after posterior spinal fusion for scoliosis typically last around four to six days for adolescents. The first couple of days focus on getting pain under control and starting to move. Most patients are walking by the day after surgery, though bending, lifting, and twisting are restricted for months while the fusion solidifies.

Pain management has shifted substantially in recent years. There is a strong push to minimize opioid use, and most centers now use multimodal regimens that combine several types of medication. Evidence supports the use of neuraxial opioids at safe doses (a single dose given near the spinal cord at the time of surgery), low-dose ketorolac (a nonsteroidal anti-inflammatory), and methadone for longer-lasting opioid coverage when needed.²⁴ These multimodal protocols, sometimes called rapid recovery or enhanced recovery pathways, combine anti-inflammatories, acetaminophen, nerve-pain medications, nerve blocks, and local anesthesia to attack pain from multiple angles and reduce total opioid consumption.²⁵

Full recovery to unrestricted activity usually takes six to twelve months, though the timeline varies. Most adolescents return to school within a few weeks and can resume light exercise by three to four months. High-impact sports and heavy lifting are typically the last activities cleared.

Long-Term Mobility and Adjacent Segment Wear

The most important trade-off of spinal fusion is permanent loss of motion in the fused segments. The more vertebrae that are fused, the more flexibility is sacrificed. For a typical adolescent fusion spanning eight to twelve vertebrae in the thoracic spine, most bending and twisting actually comes from the unfused lumbar and cervical spine, so day-to-day mobility often feels surprisingly normal. Fusions that extend lower, especially into the lower lumbar spine, produce more noticeable stiffness.

But the segments above and below a fusion must compensate for the lost motion, and over years or decades, this extra stress can cause those adjacent segments to degenerate faster than they otherwise would. This is known as adjacent segment disease. A meta-analysis of adolescent idiopathic scoliosis patients found that roughly half showed signs of adjacent segment degeneration on imaging after fusion, and the prevalence climbed with longer follow-up time and with more segments fused.²⁶ It is worth noting that visible degeneration on imaging does not always cause symptoms. Many patients with radiographic adjacent segment changes never develop pain or functional problems from them, but a meaningful portion eventually do, and some need additional surgery decades later.

Returning to Sports

One of the first questions adolescent patients and their parents ask is whether sports will still be possible. The research is reassuring on safety: returning to play after spinal fusion is considered safe, with complications reported only rarely. That said, flexibility does decrease after fusion, and the ability to return to the same competitive level can be affected by how many spinal levels are included in the construct.²⁷ Athletes in sports that demand extreme spinal mobility, like gymnastics or competitive swimming, may notice more limitation than those in running or cycling. Most surgeons clear patients for full sports participation between nine and twelve months after surgery, once the fusion is solid on imaging.

Psychological and Body Image Effects

Scoliosis is not purely a structural problem. Visible asymmetry in the shoulders, waistline, or rib cage affects how adolescents feel about their bodies, and rates of anxiety and depression are higher in teenagers with scoliosis than in the general population. Surgical correction addresses this in a way that bracing and exercise cannot. A study of adolescents who underwent deformity correction found significant improvements in both quality of life and psychiatric symptoms after surgery.²⁸ Body image disturbance specifically improved after operative correction, and the degree of body image improvement correlated with gains in self-image, activity, and mental health scores on a validated scoliosis questionnaire.²⁹ These psychological benefits are part of the decision-making equation and are worth discussing with the surgical team, especially for patients whose curves fall in the borderline range where the indication for surgery is not purely structural.