Scoliosis is an abnormal, sideways curvature and rotation of the spine, most commonly diagnosed in adolescents. When the curve is severe (typically exceeding 45 to 50 degrees), the standard treatment is spinal fusion surgery. This procedure corrects the deformity and stabilizes the spine, but it raises concerns about whether growing patients can still increase in height afterward. The answer is nuanced, involving a distinction between the immediate height gained from curve correction and the ongoing biological process of skeletal development.
How Spinal Fusion Impacts Vertebral Growth
Spinal fusion surgery permanently joins two or more vertebrae to halt the progression of the scoliotic curve. The procedure involves placing metal instrumentation, such as rods and screws, to hold the spine in a corrected alignment. Bone grafts are packed around the vertebrae, and over six to twelve months, these grafts heal, causing the treated section of the spine to fuse into a single, solid column of bone.
This fusion process intentionally stops the vertical growth of the specific vertebrae included in the surgical segment. The growth plates (apophyses) within those vertebral bodies are bridged and immobilized by the solid bony mass. Once the fusion is complete, that portion of the spine can no longer lengthen, and the fused segments will not contribute to the patient’s ultimate adult height.
Sources of Post-Surgical Height Increase
Despite the cessation of growth in the fused vertebral segments, patients continue to grow after scoliosis surgery. Standing height is determined by more than just the spine, and the majority of post-pubertal height increase comes from other skeletal sources. Most longitudinal growth occurs in the lower limbs, specifically the femur and the tibia, which are unaffected by the spinal procedure.
Longitudinal studies suggest that the loss of potential spinal length due to fusion is often compensated for by an increase in leg length. This means the final adult standing height may not be significantly different from patients who did not undergo surgery. Crucially, any segment of the spine not included in the fusion (typically the neck or lower lumbar region) will continue to grow normally until skeletal maturity is reached.
Predicting Remaining Growth Potential
Surgeons use specific medical indicators to predict a patient’s remaining growth, which is a significant factor in timing the surgery. The most widely used tool is the Risser scale, a staging system assessing skeletal maturity by examining the ossification of the iliac crest (part of the pelvis) on an X-ray. The scale ranges from Risser 0 (most remaining growth potential and highest risk of curve progression) to Risser 5 (complete skeletal maturity).
A patient with a lower Risser grade (0 or 1) is often still in their period of peak growth velocity. This may lead a surgeon to delay fusion to maximize growth and minimize the risk of curve progression above or below the fusion site. Alternatively, some centers use the Sanders classification, which examines growth plates in the hand and wrist, as it may provide a more accurate prediction of the adolescent growth spurt timing. These scores, combined with chronological age and puberty onset, help determine the optimal window for intervention.
Immediate Height Gain vs. Long-Term Growth
A distinction must be made between the height increase observed immediately after surgery and the biological process of long-term growth. Many patients experience a significant and immediate height increase, which is a mechanical effect of the procedure itself. This gain is achieved because the surgical straightening of the spinal curve restores the vertical height lost due to the sideways and rotational deformity.
The magnitude of this immediate gain relates directly to the severity of the original curve and the degree of correction achieved. Some patients gain a mean of 27.1 millimeters (over an inch) immediately. This height restoration is separate from the gradual, ongoing longitudinal growth the patient achieves from their legs and unfused spinal segments until skeletal maturity.