Most patients with degenerative scoliosis are older than 50 years of age, and with the aging of our population, adult scoliosis will become more common. In this issue, the clinical treatment of degenerative scoliosis will be introduced in detail, including the principles of treatment, choice of procedure, access selection, and postoperative complications. The main focus is on symptom relief, and as far as possible, simple, convenient, and less invasive treatment methods are chosen as long as they can ensure a certain quality of life for the patient.
Selection of fusion segment
Fusion generally does not terminate in a vertebral body with incomplete posterior column structure, a vertebral body with scoliosis or retroversion, a slipped and displaced or rotated subluxation, or a segment with severe disc degeneration. Fixation terminating in an unstable vertebral body cannot re-establish spinal stability, especially in patients with severe osteoporosis, which can lead to excessive stress on the pedicle screw at that location, which can easily break and pull out, resulting in failure of internal fixation, loss of compensation of scoliosis, and progressive development of scoliosis.
The DS range is generally L1-L5, usually with L3-L4 rotational subluxation, L4-L5 tilt, and L5-S1 disc degeneration. These characteristics determine the complexity of the selection of both proximal and distal fusion vertebrae.
Selection of proximal fusion vertebrae
1, the requirements of the proximal fusion vertebrae
The selection of the superior fusion spine should meet the following conditions: no instability of the posterior column, no displacement in any direction, no rotation of the vertebral body, no junctional kyphosis, non-sagittal or coronal deformity of the apex, no degeneration and stability of the adjacent segments, and the adjacent segments should be normally aligned in the coronal, sagittal and axial planes. Usually it is T10 or T11.
2. Problems of the thoracolumbar junction segment
The deformity range of most degenerative scoliosis is L1-L5. If the fusion terminates at the thoracolumbar junctional segment, the pressure on the junctional segment is excessive and secondary proximal junctional kyphosis may occur and increase the probability of adjacent segment degeneration, compression fracture, and screw prolapse at the superior end of the fused segment.
Selection of distal fusion spine
Due to the presence of rotational subluxation of L3-L4 and tilt of L4-L5 in degenerative scoliosis, it is usually not possible to terminate the distal fusion vertebrae at L3 or L4 to preserve the motor segment as in AIS, but only at L5, sacrum, or iliacus.
1.Fusion to L5
If the L5-S1 disc does not have degeneration or is not severely degenerated and there is no obvious deformity, the distal fusion segment can be terminated at L5. the advantage of fusion to L5 is that it protects the L5-S1 motor segment, avoids exposure to the sacrum, reduces the difficulty of surgery, decreases the operative time and intraoperative bleeding, and avoids the formation of the L5-S1 pseudoarthrosis. However, most scholars believe that fusion to L5 will accelerate the degeneration of L5-S1 and may lead to sagittal imbalance and aggravation of symptoms.
2. Fusion to S1
Since most patients with degenerative scoliosis have degeneration of L5-S1, most surgeons prefer to extend the fusion stage to the sacrum. Indications for fusion to the sacrum include: slipped vertebrae at L5-S1, stenosis at L5-S1, previous decompression of the L5-S1 lamina, significant tilt at L4-L5 or L5-S1, significant loss of balance with significant degeneration of the L5-S1 disc.
3. L5-S1 intervertebral fusion and use of the iliac spine nail
In order to avoid the formation of L5-S1 pseudarthrosis and to reduce the probability of sacral extraction and stress fracture many scholars have proposed the need for improvement of L5-S1 fusion technique, which includes interbody fusion and the use of iliac screws. l5-S1 not only increases the biomechanical stability, restores the anterior convexity and increases the probability of lumbosacral fusion, but also increases the height of the intervertebral space and relieves the symptoms of neurological compression.
The simple two sacral screws alone are not conducive to the stability of the sacroiliac structures. Xu Du learned that distal sacral screws should be added or iliac screws should be used. In long-segment fusion, interbody fusion of L5-S1 or even L4-L5 must be performed, using double cortical S1 pedicle screws and iliac pterygoid nails. When using iliac wing screws, the head of the screw should be placed posteriorly under the iliac wall to minimize protrusion.
In summary, DS surgery is more complex and has many complications. Intraoperatively, it is important to fully understand the source of the patient’s pain and the characteristics of the deformity, carefully assess the coronal, sagittal balance and rotational deformity, and select the appropriate surgical approach, access and fusion segment in order to achieve satisfactory results.
Posterior osteotomy orthopedic surgery
Posterior osteotomies, including Smith-Petersen osteotomies and even total vertebral body resections, can be used for lumbar kyphosis or rigid fixed deformities. SPO and PO are used in patients with long-stage arcuate kyphosis with mild to moderate sagittal balance and only partial flat back or kyphosis. PSO is indicated for patients with significant sagittal imbalance, angular kyphosis, and a spine that is difficult to fuse with SPO or PO. One PSO can correct up to 35 degrees of kyphosis in the lumbar spine and up to 25 degrees of kyphosis in the thoracic spine. The lower the level of osteotomy, the more effective the overall correction, but the distal side needs to be fixed for at least 2-3 segments.
Application of minimally invasive surgery
With the advancement of technology, minimally invasive surgery has been gradually used in the treatment of DS, including endoscopic decompression, transcatheter TLIF, percutaneous pedicle screw fixation, and retroperitoneal intervertebral fusion via the extreme lateral approach of the lumbaris major muscle L5-S1 axial intervertebral fixation fusion, decompression and dynamic stabilization of non-fusion techniques for the treatment of DS in the elderly. It is the current direction of spinal surgery, which can relieve symptoms and reduce injuries at the same time.
Postoperative complications
Recent complications (perioperative period)
1. Pulmonary disease
Pulmonary complications are a more serious complication after adult scoliosis orthopedic surgery and are one of the main causes of death. They mainly include pleural effusion and pulmonary atelectasis.
2. Urinary tract infection
Urinary tract infection is the most common complication after DS surgery.
3.Nerve injury
4.Other
They include postoperative infection, perioperative heart disease, retinal vascular embolism and cerebral infarction, nerve root injury, cerebrospinal fluid leakage, deep vein thrombosis, pulmonary embolism, pedicle fracture, vertebral fracture and other complications. Intraoperative blood transfusion is mostly a risk factor, while the amount of bleeding is related to the number of surgical segments and pedicle osteotomy.
Distant complications
1.Adjacent segment disease
Adjacent segmental disease is the most common long-term complication, including spinal stenosis, disc herniation, compression fracture, and posterior convexity deformity.
2.Pseudarthrosis formation and internal fixation failure
3.Junctional kyphosis
The incidence of junctional kyphosis is 2% to 26% and occurs mostly at the proximal end of long segmental fixation. Proximal fixation of the vertebral body or adjacent vertebral body fractures and adjacent segmental degeneration can lead to progressive kyphosis.
Clinical outcome assessment
Appropriate surgical treatment of DS can yield relatively satisfactory results, with pain relief rates generally in the range of 70% to 80%, especially for neurogenic pain and intermittent claudication, which are often significantly improved. Due to the stiffness of the DS deformity, the correction rate is lower than that of AIS, with a coronal correction rate of 34% to 43%. For adult DS patients, the primary goal of surgical treatment is not purely orthopedic, but to re-establish sagittal balance, restore spinal stability, and improve patient symptoms and quality of life. The health-related quality of life (HRQL) of patients after surgery is less related to their coronal deformity than to their sagittal deformity. The primary goal of adult spinal deformity orthopedics is to re-establish SVA balance, and the recommended ideal value of SVA is ≤5 cm. anterior lumbar and posterior thoracic convexity angles are the most important local sagittal assessment indicators affecting quality of life in adults with spinal deformities. The pelvic tilt angle (PT) is highly correlated with quality of life after SVA and trunk tilt.