For complex, extremely angular scoliosis deformities, especially severe lateral kyphosis, traditional orthopedic methods often seem overwhelming, relying only on soft tissue release or implantation of devices to correct the deformity, sometimes difficult to achieve satisfactory treatment results, and spinal osteotomy seems to have become a new trend, which has been carried out in several hospitals in China.
When scoliosis is corrected using spinal osteotomy, the posterior structure of the parietal region of the spine is removed to restore some flexibility to the spine, while the convex side of the spine is shortened, thereby reducing the excessive bracing of the concave side of the scoliosis and maximizing deformity correction. However, spinal osteotomy is a complex and technically demanding surgical technique.
The special anatomical structure, such as the operation related around the spinal cord, makes the technique face problems such as high bleeding, long operation time and complicated operation, in addition to the fact that no mistakes are allowed during the whole operation, otherwise it will lead to irreparable consequences, therefore, caution must be exercised when deciding to perform spinal osteotomy in
I. Selecting the right case
Spinal osteotomy, as a means, or rather an avenue, of orthopedic spinal deformity, can only be performed as a supplement to conventional techniques. Generally speaking, the indications for spinal osteotomy are limited to patients with severe scoliosis and lateral kyphosis, with less than 30% flexibility of the deformity, and scoliosis that cannot be better orthoped by conventional techniques. In addition, adult patients with idiopathic scoliosis often have stiff bends and are often associated with spinal instability and narrowing of the spinal canal and nerve root canal.
As a result, the usual bracing, compression and de-rotation correction techniques are often difficult to achieve satisfactory results. In this group of patients, although anterior disc and annulus removal and release can increase the flexibility of the stiff spine, anterior release surgery inevitably increases surgical trauma and treatment costs and can cause further damage to the already impaired pulmonary function, so spinal osteotomy techniques can also be used for severe adult idiopathic scoliosis.
Prior to spinal osteotomy, a thorough imaging evaluation must be performed to carefully study the deformed spinal structures through x-ray and CT 3D reconstruction and, if necessary, MRI to understand whether there are abnormalities in the corresponding spinal nerve structures in the spinal canal, whether there are bony ridges, and whether there are other spinal cord tethering systems. Through these imaging examinations, a thorough surgical plan is formulated, and the site and scope of osteotomy are determined, and appropriate anchorage points for internal fixation are selected.
Second, choose the appropriate osteotomy method
The traditional osteotomy methods of the spine mainly include simple open osteotomy, simple closed osteotomy, and closed-open osteotomy. However, the traditional osteotomy method mainly focuses on the sagittal plane of the spine, but scoliosis is a three-dimensional deformity that requires more focus on the coronal plane in the orthopedic process;
Therefore, when using spinal osteotomies to treat scoliosis, it is important to have a more comprehensive and in-depth understanding of the various osteotomy methods. The most classic spinal osteotomies include the SP osteotomy, the transcolumbar “V” osteotomy, and the spondylectomy.
The SP osteotomy (Smith-Petersenosteotomy, SPO) is a typical open osteotomy that corrects kyphosis by amputating and closing the posterior spinal column structures and opening the disc space in the anterior spinal column, with the center of the hinge often located at the posterior edge of the vertebral body.
The literature reports that a correction of approximately 30° can be obtained with one segment of SPO, but the wedge-shaped opening of the anterior column inevitably prevents bony contact between the vertebrae after spinal orthopedics, and the stability of the anterior mid-column is severely compromised, which can seriously lead to delayed osseointegration or failure of posterior internal fixation, and there is even a risk of paralytic intestinal obstruction and vascular complications. In contrast, when the SPO technique is used to treat scoliosis, it often does not require complete fracture and opening of the anterior intervertebral disc annulus and only requires proper extension to achieve 10-15° per segment, while multi-segment osteotomy can greatly improve its orthopedic capacity.
In the treatment of scoliosis, in addition to improving the sagittal plane deformity of the spine, the orthopedic effect of SPO is more on increasing the flexibility of the spine by removing the posterior column structures such as the vertebral tuberosity, thus increasing the orthopedic effect of scoliosis. Therefore, the SPO technique is more suitable for the treatment of stiff, oblong lateral kyphosis.
Pedicle subtraction osteotomy (PSO) originated from the “eggshellprocedure” in 1949. The method was first used for deformities in the sagittal plane of the spine and was later modified to form the typical osteotomy of today, PSO, which is a closed osteotomy by removing the posterior vertebral plate, the pedicle, and the anterior vertebral body in a “V” shape, and then achieving bony contact (boneon bone) of the anterior mid-column through posterior closure. It is a closed type of osteotomy. In this orthopedic procedure, the hinge point of correction is located in the anterior cortex of the vertebral body.
The PSO technique not only shortens the posterior spinal column structure, but also shortens the anterior mid-column of the spine. On the one hand, the shortening of the osteotomy allows both anterior and middle columns to reach bone-bone contact, which makes the spine more stable and also increases the fusion rate of the spine. On the other hand, if the osteotomy site is high, excessive shortening of the posterior column will inevitably cause flexion and folding of the spinal cord, which can lead to serious neurological complications. Based on these characteristics, the PSO technique is primarily indicated for angular curves that are low in position and have significant deformity changes in the vertebral body, while it is not an option for orthopedic treatment of those rigid oblong curves, when possible.
Vertebral Column Resection (VCR) is the complete removal of one or more spinal segments, including the upper and lower intervertebral disc structures. The procedure begins with the removal of the posterior structures, and by occluding the transverse costal joints and part of the proximal ribs on both sides, subperiosteal dissection is performed from both sides to expose the anterior vertebral body and occlude it completely, and then the spine is shortened and orthopedic by applying pressure with instruments. This method is a typical closed-open osteotomy. Because of the large amount of bony structures removed from the anterior mid-column, structural support implants or nonsupporting implants are generally required to rebuild the stability of the anterior mid-column.
radford et al. used a combined anterior-posterior approach for total laminectomy to correct patients with severe rigid scoliosis, whereas Suk [8] et al. used a purely trans-posterior spondylectomy to correct severe spinal deformities. Theoretically, the VCR technique completely removes the deformed vertebrae and the anterior column is reconstructed as needed to completely correct deformities in the sagittal and coronal planes. However, the poor intraoperative and postoperative stability, high bleeding, and high risk of nerve injury make it impossible to use this technique widely for the correction of scoliosis deformities.
In our clinical work, we have combined the advantages of PVCR and eggshell techniques to achieve debridement of single or multiple vertebral bodies and scraping of adjacent discs by an expanded eggshell technique. The method starts with the cancellous bone, forming a hollow shell, and then thins the hard shell from the inside out, finally completely removing the cortical structures around the vertebral canal. The technique is highly controllable and has a low chance of damaging the neural structures because of the fine detail that can be achieved with the grinding drill.
The repositioning and realignment of the spinal deformity can be accomplished very well by debridement of single or multiple parietal vertebrae. In this operation, it is particularly important to make the vertebral body partially denuded, and its residual part of bone can be used as a bony cage, which facilitates early bony fusion and helps to reconstruct spinal stability.
In conclusion, before proposing to use spinal osteotomy to correct severe scoliosis deformity, different osteotomies such as posterior column wedge osteotomy, transforaminal osteotomy and spondylectomy must be selected according to the type of deformity, severity, presence of nerve damage and general condition of the patient. SPO or VCR, as well as our expanded eggshell technique, may be considered for patients with largely uncorrected spinal deformity on left and right lateral flexion plain radiographs in the supine position, with a coronal cobb angle > 90°, and/or a sagittal cobb angle > 50°.
The specific osteotomy approach needs to be decided based on the localization of the deformity on the 3D CT reconstructed images and combining the advantages and disadvantages of the various osteotomy approaches. Of course, it is also very important for the operator to use the surgical method and access that he or she is most familiar with.
Selection of osteotomy site and osteotomy range
In the past, vertebral osteotomy was generally below T10, because osteotomy above this level is likely to cause massive blood loss and irreversible paralysis. From our clinical experience, according to the patient’s specific situation, choose the appropriate osteotomy method, as long as the operation is proper, above T10 is not a forbidden area for osteotomy. The resected vertebral body is generally selected for the laterally convex parietal vertebrae for wedge-shaped osteotomy with the bottom edge in the coronal plane of the convex side. If the lateral bending angle is too large, multiple vertebral coronal osteotomies are feasible to increase the correction rate and to disperse the stress borne by the internal fixation instrumentation.
For single vertebral osteotomy of thoracic spine, whether coronal osteotomy or sagittal osteotomy, in order to reduce excessive shortening and tortuosity of the spinal cord, resulting in relative spinal stenosis, therefore, excessive osteotomy should be avoided, and the height of the bottom edge of the wedge osteotomy should not exceed 1/3 of the height of the osteotomy vertebrae.
Fourth, the prevention of complications
Spinal osteotomy is a very challenging spinal surgical technique, and the surgical outcome may be ideal if handled well, while the chances of surgical complications are very high if mistakes are made. Common surgical complications currently include nerve injury and vascular injury. Familiarity with and avoidance of the associated surgical risks is a problem that every surgeon must face.
Nerve injury: The most common cause is spinal cord cramping during closure of the osteotomy after completion of the osteotomy, or compression of the spinal cord by the vertebral plate. The spinal cord is also susceptible to injury if it is not properly protected at the time of completion of the osteotomy because the spinal cord has lost the protection of stable structures.
The main avoidance measures include.
(1) For cases where the entire spine is to be completely amputated, as in the VCR technique, the circumferential decompression of the spinal cord should be complete and it needs to be fully estimated that the spinal cord cannot be compressed by any bony structures anteriorly or posteriorly during the orthopedic process. Temporary fixation with titanium rods is required before osteotomy to avoid sagittal translation (ST) of the spine after osteotomy, which may damage the spinal cord;
(2) The osteotomy should not be too long to avoid spinal cord injury due to excessive shortening of the spine after compression at the parietal spine;
(3) The correction of the parietal vertebrae should be based on compression on the convex side, with appropriate support on the concave side;
(4) The height of the bottom edge of the osteotomy should preferably not exceed 1/3 of the height of the vertebral body, otherwise the spinal cord may be thickened and tortuously compressed, resulting in spinal cord compression symptoms;
(5) Maintain a clear surgical field, and dynamically observe the pulsation of the spinal cord under direct vision to avoid spinal nerve injury;
(6) During orthopedic surgery, it is best to perform dynamic detection with the relevant neurological monitoring system.
Vascular complications: When performing spinal osteotomy, moderate controlled hypotension is beneficial to reduce the amount of intraoperative bleeding. Of course, some intraoperative maneuvers, such as complete hemostasis and sealing the bone trauma with bone wax, can also be effective in reducing bleeding.
Intraoperative bleeding is mainly concentrated in the process of removing the inner and posterior walls of the spinal canal, and it is very difficult to control bleeding from the epidural venous plexus. Neither bipolar electrocoagulation nor hemostatic gauze can effectively control bleeding, and the key is to remove the inner and posterior walls of the spinal canal before grinding and drilling to effectively thin the residual bone to facilitate removal, in order to reduce the interference with the epidural venous plexus and the operation time [12]. The use of intraoperative autologous blood transfusion can also effectively reduce the input of allogeneic blood.