Severe Spinal Deformity Surgery: Curves Beyond 90 Degrees

Severe spinal deformity surgery corrects curves of 90 degrees or more caused by scoliosis, kyphosis, spinal tuberculosis or a previous operation that failed. The techniques include removing an entire vertebra to straighten the spine, growth rods in young children and cages to rebuild collapsed segments, all performed under neuromonitoring. Late referral can turn a small operation into a very large one.

Dr. Puneet Girdhar, then Principal Director & Head, Ortho Spine, MIS & Robotic Spine Surgery at BLK-Max Super Speciality Hospital, New Delhi, India, closed his 2024 masterclass on spinal surgery technology with a series of his most complex cases. This article sets out the types of deformity, the thresholds for bracing and surgery, the cases he presented and the lesson he drew from them about timing. It forms part of the spinal surgery technology guide.

What counts as a severe spinal deformity

A spinal deformity is an abnormal curvature of the spine. Scoliosis is a sideways curve, usually with rotation of the vertebrae; kyphosis is a forward curve that produces a hunched posture; kyphoscoliosis combines both. Curves are measured on X-ray as the Cobb angle, the angle between the most tilted vertebrae at the top and bottom of the curve.

Several of the cases Dr. Girdhar presented had curves of 90 degrees, and one was close to 100 degrees. At that size, a curve affects far more than appearance: it can compress the spinal cord, impair breathing and leave the patient unable to stand balanced or to walk.

Three types of scoliosis

Dr. Girdhar classifies scoliosis into three types, each of which can require surgery at a different stage:

• Idiopathic scoliosis, the most common form, with no identifiable underlying cause.
• Congenital scoliosis, caused by a malformation of the vertebrae present from birth, such as a hemivertebra, a wedge-shaped half vertebra that tilts the spine as the child grows.
• Neuromuscular scoliosis, caused by an underlying disorder of the nerves or muscles.

Warning signs and thresholds for treatment

The warning signs he listed are visible on examination: one shoulder higher than the other; the head not centred over the pelvis, so that the patient tilts; one hip more prominent than the other; one side of the rib cage or chest standing out; and changes in the skin over the back, such as a dimple, a patch of hair or a brown discolouration, which can point to an underlying abnormality of the spine. His 2025 masterclass covered these signs in children in detail in scoliosis and kyphosis in children.

The treatment thresholds differ by type.

A doctor in the audience asked at what point bracing should be considered to have failed. Dr. Girdhar's answer: bracing has failed when the curve progresses beyond 40 degrees despite the brace, and a surgical opinion is then needed; surgery is generally indicated once the curve exceeds 45 to 50 degrees. For congenital scoliosis his rule was absolute: surgery at about four years of age.

Spinal tuberculosis: rebuilding a spine destroyed by infection

Tuberculosis of the spine, also known as Pott's disease, destroys the vertebral bodies; in Dr. Girdhar's words, it eats the bones. As the front of the spine collapses, the spine angles forward into a kyphosis and can compress the spinal cord.

He presented two patients. In the first, an earlier operation for spinal tuberculosis had failed. His team reconstructed the spine, inserted a new cage to replace the destroyed bone and restored proper alignment.

The second patient had tuberculosis that had damaged the spine and produced a 90-degree curve. She arrived in a wheelchair, unable to walk, with grade 2 power in her legs, meaning she could move them only with gravity eliminated and could not lift them against it. The team removed one entire vertebra, a procedure known as vertebral column resection, and corrected the deformity. Four weeks after surgery she had started walking, a major recovery of neurological power. Spinal tuberculosis is covered from another surgeon's perspective in spinal TB surgery.

Growth rods for early-onset deformity

Deformity that begins in early childhood presents a different problem: the spine still has years of growth ahead, and fusing it early would stunt the chest and trunk. Dr. Girdhar showed a child with syndromic early-onset kyphoscoliosis, a combined sideways and forward curve associated with an underlying syndrome.

The solution was growth rods, fixed to the spine with screws and rods. Rather than a single full correction, the curve is corrected slowly while the spine continues to grow, with an increase in height over three to four years. Growth rods are lengthened at intervals as the child grows.

Revising failed deformity surgery

One patient had undergone deformity surgery elsewhere that failed, leaving a very severe scoliosis combined with kyphosis: two curves, each of 90 degrees. Dr. Girdhar's team performed a revision correction. After surgery, a single curve of 40 degrees remained in place of the two 90-degree curves.

The operation was performed, like all his deformity surgery, under neuromonitoring, and all the nerve signals were normal after surgery. The role of neuromonitoring in deformity correction is explained in spine surgery paralysis risk and the technology that reduces it. His 2026 masterclass returned to failed operations in revision spine surgery and neglected spinal deformity.

Very large curves and deformity of the neck

Two further cases showed the range of the technique. In one, a curve of almost 100 degrees was corrected, with a marked difference between the images before and after surgery.

In the other, the deformity lay in the cervical spine, the neck, with severe scoliosis and kyphosis. The team removed whole vertebrae to achieve complete correction, in an operation lasting eight to ten hours. Surgery on a deformed neck carries particular risk, because the spinal cord and the arteries supplying the brain run through a narrow space.

Late referral: a four-hour operation becomes 16 hours

Dr. Girdhar's final case was chosen to make a point to referring doctors. The patient had a hemivertebra. The right time for surgery, he said, is four years of age; the patient reached him at 16.

The delay, in his view, is avoidable. Many doctors are not aware that a hemivertebra should be operated on at four, and because the child seems small, everyone waits and surgery is postponed. Had this child come at four, the operation would have been a small one, taking about four hours. At 16, the deformity had become large, and so did the surgery: the team removed bone, inserted a cage and corrected the spine in an operation lasting 16 hours. To cut bone safely close to the spinal cord, they used the latest ultrasonic bone cutting.

The comparison is the clearest statement in the masterclass of what referral timing means in practice:

Implants in modern deformity and fusion surgery

A second part of the audience question on bracing asked whether long plates, such as Roy-Camille plates, could be used in place of an interbody cage. Dr. Girdhar's answer was that nobody uses Steffee plating or similar plates nowadays. For the last 15 to 20 years, surgeons have used pedicle screws, passed through the pedicles into the vertebral bodies, together with titanium or PEEK cages placed between the vertebrae. PEEK (polyetheretherketone) is a strong medical plastic.

When to refer for severe spinal deformity surgery

The cases point to a short set of rules for any doctor who first sees a child or adult with a spinal curve:

1. Examine for the warning signs: uneven shoulders, a tilted trunk, a prominent hip or rib cage, and skin changes over the spine.
2. Refer idiopathic curves for a surgical opinion once they pass 40 degrees or progress despite bracing; surgery is generally indicated beyond 45 to 50 degrees.
3. Refer a congenital hemivertebra early, so that surgery can take place at about four years of age.
4. Refer neuromuscular scoliosis when it affects breathing or balance.

Costs for deformity correction are listed on the scoliosis and spinal deformity correction cost page. The questions from this session, including the full answer on bracing, are on the Live Discussion page.