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Back to Journal »Orthopedic Research and Review» Volume 13
The effect of cantilever method in reducing kyphosis in thoracolumbar tuberculosis: short-term follow-up
Authors Librianto D, Hadisoebroto Dilogo I, Fauzi Kamal A, Saleh I, Ipang F, Apriya D
Published on December 3, 2021, Volume 2021: 13 pages, pages 275-280
DOI https://doi.org/10.2147/ORR.S342365
Single anonymous peer review
Editor who approved for publication: Professor Clark Hung
Didik Librianto、1 Ismail Hadisoebroto Dilogo、2 Achmad Fauzi Kamal、2 Ifran Saleh、2 Fachrisal Ipang、1 Dina Aprilya Faculty of Orthopaedics and Traumatology, Faculty of Medicine, Professor Soelarto Building, 1st Floor, RS Fatmawati Street, Jakarta, Indonesia Phone +12430 6289655106136 Fax +6221-7660616 Email [email protected] Background: Tuberculous spondylitis (STb) of the spine Kyphosis is not just a matter of appearance. It has potential adverse effects on spine related structures and cardiopulmonary function. It can be corrected at any stage of STb; however, corrective surgery is challenging, especially in advanced cases, where the additional stiffness of the spine can be considered. So far, the cantilever technique is still the gold standard for sagittal deformity correction. However, so far there is no research to explore its effectiveness for thoracolumbar kyphosis, especially caused by tuberculous spondylitis. Methods: A retrospective study of 16 patients with thoracolumbar kyphosis and tuberculous spondylitis undergoing corrective surgery in our center from 2020 to 2021. STb patients. Results: At the 3-month follow-up, the average Cobb angle was 14.6°±10.27°, and the average gain was 20.90°±12.00°, which was positively correlated with the correction of thoracolumbar kyphosis (TLK) (68.69%, r = 0.654), p = 0.001). The average thoracic kyphosis, lumbar lordosis, and sagittal axis were 30.6°±13.08°, 39.4°±16.02°, and 1.4±4.09 cm, respectively, and the sagittal Cobb difference was 12.70±9.85. Conclusion: The thoracolumbar spine cantilever technique to reduce the kyphotic Cobb angle can significantly improve the thoracolumbar kyphosis and readjust the sagittal axis of the spine. Therefore, the cantilever technique is still the gold standard for sagittal deformity correction and can be used to correct kyphosis in STb cases of thoracolumbar spine. Keywords: thoracolumbar spine, kyphosis, tuberculous spondylitis, deformity correction, cantilever technique
The incidence of tuberculosis in Indonesia ranks third in the world. In 2018, the World Health Organization (WHO) estimated that 316 out of every 100,000 Indonesians have the disease, and it is estimated that 3% of all tuberculosis cases have tuberculous spondylitis (STb). 1,2 Nearly 3% of STb patients develop severe kyphotic deformities. 3 In both early and late stages of infection, the development of kyphosis will increase more disability related to abnormal postures caused by spinal imbalance-even if the infection has subsided. Painful rib-pelvic impingement, cardiopulmonary dysfunction, or delayed paraplegia may occur an average of 10 years after the onset of the disease. 4-6
The management of residual deformities is always challenging, especially those without neurological deficits. Appropriate surgical techniques may help prevent or reverse the deterioration of neurological function, improve lung function, overall motor function, cosmetic and psychosocial problems. The cantilever method is one of the most common spinal deformity correction techniques. Our goal is to use the cantilever technique to evaluate the reduction of kyphosis in the thoracolumbar STb.4-6
This is a retrospective study of 20 patients who underwent surgical treatment of thoracolumbar STb kyphosis at Fatmawati General Hospital in Jakarta, Indonesia from January 2020 to June 2021. Among them, there are 7 males and 13 females. The average age of the patients was 31.3 years. The onset of the deformity is 5 to 12 months before the operation. The most affected segment is L1-2 (30%), followed by T10-11 (25%) and T11-12 (10%). The general characteristics are restored in Table 1. Table 1 General characteristics
Surgical indications are neurological deficits and abnormal thoracic kyphosis (TK) or evidence of kyphosis in other spine regions (lumbar or thoracolumbar region). All patients received conventional anti-tuberculosis chemotherapy at least 2 weeks before surgery and 18 months after surgery. Before the operation and 3 months after the operation, the whole spine plain film was taken to evaluate the sagittal plane parameters.
Standard anteroposterior (AP) and lateral X-rays of the standing spine were taken before and 3 months after the operation. All radiological measurements were evaluated by independent observers who were not involved in the surgery. On the lateral radiograph, several sagittal balance parameters were evaluated: cervical spine 7 sagittal axis (SVA), thoracic kyphosis (TK), lumbar lordosis (LL), and thoracolumbar kyphosis (TLK). Cobb angle or regional kyphosis angle is defined as the angle between the upper and lower ends of adjacent vertebrae and the pathological segment. 7
Thoracic kyphosis (TK) is measured from the upper endplate of T2 to the lower endplate of T12. If it is difficult to see T2 due to the radiographic shadow of the shoulder, TK can also be estimated from the upper endplate of T5 to the lower endplate of T12. The thoracic spine has an average of 30 degrees of kyphosis at T5-T12. Thoracolumbar kyphosis (TLK) (normal 0 degrees) is measured by the angle between the upper endplate of T10 and the lower endplate of L2. Lumbar lordosis (LL) (normal 60° lordosis) is the angle between the lower endplate of T12 and the upper endplate of S1. In addition, global sagittal parameters can be used to assess spinal balance. When performing SVA measurements on patients with normal or neutral sagittal balance, the C7 plumb line should be located within 3 cm above and behind the S1 endplate, whether it is anterior (3 cm positive) or posterior (3 cm negative) (table 2). Table 2 Normal sagittal parameters
The surgery is performed by an orthopedic spine surgeon (DL). Make a posterior midline incision and extend above and below the affected segment as needed. Insert pedicle screws at the proximal and distal ends of the apex (Figure 1). Depending on the type of deformity, osteotomy is performed at the apex, followed by spinal decompression surgery (laminectomy, facet joint resection). Depending on the position of the apex, we manage flexible deformities through posterior column, Smith-Petersen or Ponte osteotomy (Figure 2A). Fixed deformities are processed according to the size of the deformity. A large kyphotic angle of more than 30° and a fused anterior column are treated by spinal resection (Figure 2B). At the same time, pedicle osteotomy combined with Ponte or Smith-Peterson osteotomy is used for smaller angles. Figure 1 The cantilever method of kyphosis correction: (A) the level of stability required for pedicle screw placement; (B) osteotomy at the apex of the deformity; (C) insertion of the pre-curved rod; (D) from the proximal end to the distal end Tighten the screws gradually and make adjustments to achieve the final correction. (E) Final construction. Note: Reprinted from Ann Med Surg, 69, Librianto D, Aprilya D. Cantilever treatment of tuberculous spondylitis with severe kyphosis correction: technical description and literature review. 102764, Copyright 2021, with permission from Elsevier5. Figure 2 Postoperative results with reduced kyphosis. (A) Flexible deformity; (B) Fixed deformity (black arrow: anterior segment of fusion).
Figure 1 The cantilever method of kyphosis correction: (A) the level of stability required for pedicle screw placement; (B) osteotomy at the apex of the deformity; (C) insertion of the pre-curved rod; (D) from the proximal end to the distal end Tighten the screws gradually and make adjustments to achieve the final correction. (E) Final construction.
Note: Reprinted from Ann Med Surg, 69, Librianto D, Aprilya D. Cantilever treatment of tuberculous spondylitis with severe kyphosis correction: technical description and literature review. 102764, Copyright 2021, with permission from Elsevier5.
Figure 2 Postoperative results with reduced kyphosis. (A) Flexible deformity; (B) Fixed deformity (black arrow: anterior segment of fusion).
After osteotomy and decompression, a pre-bent rod is inserted and connected to each screw in turn. When the distal screw is gradually tightened from the proximal end to the distal end, the proximally fixed rod will act as a cantilever, pulling the lower segment backwards. Therefore, the spine will adopt the shape of a rod and enter the desired alignment (Figure 1).
For severely bent cases, it is best to use an extra-long arm to reduce the screw and bend the operating table to stretch the spine to reduce the reduction force and prevent the screw from being pulled out during the correction process. After reduction, posterolateral fusion was performed. After the operation, the patient wears a spinal brace for at least 3 months.
Statistical analysis was performed using SPSS 25.0 (SPSS Inc., Chicago, IL, USA). All results are reported as the mean ± standard deviation (SD) of normally distributed data and the median (range) of abnormally distributed data. Paired-sample t-test and nonparametric 2-dependent test were used to compare preoperative and postoperative radiology data. The statistical significance is set as P ≤ 0.05.
From January 2020 to March 2021, 56 cases of tuberculous spondylitis with kyphosis were treated in our center, of which the affected segment was the thoracolumbar segment (20 cases), followed by the lumbar segment (14 cases), and the upper thoracic segment (11 cases), thoracic aorta (8 cases), cervical spine (3 cases). The main focus of this study was the thoracolumbar region (n = 20). We compared the short-term radiology results of the cantilever reduction technique to overcome this level of kyphosis.
At the preoperative and 3-month follow-up, the average Cobb angles were 35.5°±17.41° and 14.6°±10.27°, respectively. The preoperative Cobb angle was strongly positively correlated with the thoracolumbar kyphosis angle (r=0.775, p<0.001). The preoperative and postoperative measurements of Cobb angle, thoracic kyphosis, and SVA were significantly different (Table 3). The average Cobb correction, thoracolumbar kyphosis reduction, and SVA improvement were 62.07%, 68.69%, and 2.12 cm, respectively. In this study, the reduction in Cobb was also significantly correlated with the reduction in postoperative TLK (r = 0.654, p = 0.001) (Table 3). Table 3 Results summarize the sagittal plane balance parameters before and after surgery
Table 3 Results summarize the sagittal plane balance parameters before and after surgery
Sagittal Cobb difference (SCD) is measured as the difference between the thoracic kyphosis angle and the lumbar lordosis angle. The average preoperative and postoperative SCD were 20.65±10.70 and 12.70±9.85, respectively. The preoperative and postoperative SCD was significantly different (p = 0.036).
There were no complications such as kyphosis at the proximal junction or aggravated curve in the early postoperative period.
The thoracolumbar region, the lower thoracic spine and upper lumbar spine (T10-L2) are the most commonly affected parts of STb. This transition zone has complex biomechanical features because it is located between the relatively fixed thoracic spine and the more flexible lumbar spine. Moreover, it is also the transition from physiological thoracic kyphosis to physiological lumbar lordosis. This area is at a biomechanical pressure point and is susceptible to bacterial infection. 8
STb can cause damage to the vertebral body, intervertebral discs, and surrounding soft tissues. Kyphosis is a common manifestation of the collapse of the anterior vertebral body caused by STb. It occurs in the thoracolumbar region and causes the thoracolumbar kyphosis (TLK) angle to increase by more than 0-6 degrees. 7-9 In our study, the average kyphotic Cobb angle and TLK are 35.5° and 34.15°, respectively. These two parameters are closely related before surgery.
Kyphosis is basically a sagittal deformity. Therefore, it can usually be fully corrected by the cantilever method. 5,6 Since the discovery of pedicle screws decades ago, the cantilever method has been widely used to correct kyphotic deformities. The reduction in kyphosis is achieved by fixing the pre-bent rod to the pedicle screw proximal to the apex of the deformity after the osteotomy. The prerequisite of the cantilever device in the spinal structure is to be able to withstand the deformation under various physiological loads. The pedicle or vertebral screw used must have this requirement. The rod or plate is used to transfer the load to another cantilever beam to the spine. In addition, by applying pressure, traction or rotation force to the screw connected to the rod, correction can be accomplished by applying a moment arm. 5,10,11
Our research proves that the cantilever technology we use is sufficient to correct the kyphotic Cobb angle with a correction of 20.90°±12.00°. This result is slightly better than the study by Xu et al.13, which compared surgical methods for tuberculous spondylitis in the elderly population. Both groups use cantilever technology, and their angle correction curves are similar, 16.3 ± 2.0 and 15.4 ± 5.0 (p: 0.068). The reduction rate of kyphosis in our study was 68.69%, which is similar to that Hu et al.14 also used this correction technique to treat 20 cases of active thoracolumbar tuberculosis in children with kyphosis.
We found that Cobb angle correction was significantly associated with a reduction in TLK-it was also significantly reduced to near normal values after surgery. Our results show that the reduction of Cobb in the thoracolumbar region has little value for thoracolumbar curvature, and there is no significant difference before and after surgery. Interestingly, the angle difference between TK and LL becomes smaller after TKL correction, which is more conducive to sagittal plane balance.
The C7 sagittal longitudinal axis (SVA) can help determine the overall sagittal balance by measuring the distance between the line drawn from the center of the body of C7 to the tail and the horizontal line from the upper S1 endplate. The best sagittal balance is when the SVA is within 3 cm of the anterior or posterior relative to the posterior and upper posterior aspect of the S1 endplate. The distance between 3 and 8 cm is considered suboptimal. Optimal sagittal alignment can improve the efficiency of spinal biomechanics, thereby reducing energy consumption and slowing down the degeneration process of adjacent segments. 7
In a retrospective analysis of the factors that control sagittal spine balance after TL fusion with a long instrument in adults, the sagittal Cobb angle difference of more than 20° between LL and TK resulted in the best sagittal balance in most cases. 7,12 In our study, the preoperative sagittal cobb difference was 20.65, which has been significantly reduced to 12.7 degrees (p=0.036). Although there is no significant correlation between the preoperative and postoperative sagittal cobb difference and the preoperative and postoperative SVA (p = 0.077 and 0.417), the postoperative cobb difference has been reduced to the optimal value (below 20 degrees) and SVA It has also improved (within 3 cm) (Table 4). These hints have achieved the improvement of sagittal plane balance through correction. Table 4 Measurement of the difference between the sagittal vertebral axis and the sagittal Cobb
Table 4 Measurement of the difference between the sagittal vertebral axis and the sagittal Cobb
The disadvantage of this technique is that the degree of correction is completely determined by the manual pre-bent rod, so more force is required to achieve the required correction. The greater corrective force is accompanied by the risk of screw loosening and pulling out, especially when the maximum stress is applied. 6,10 To avoid the risk of implant failure after correction, multiple osteotomy levels can be considered for progressive correction. 15 A longer follow-up is needed to assess correction loss, kyphosis and failure, adjacent segment disease, Implantation failure and development of spinal imbalance.
So far, the cantilever technique is still regarded as the gold standard for correcting sagittal deformities of various spinal deformities. Our research proves that this technique can effectively and safely correct thoracolumbar tuberculosis and kyphosis.
SVA, sagittal longitudinal axis; SCD, sagittal Cobb difference (between thoracic kyphosis and lumbar lordosis); TK, thoracic kyphosis; LL, lumbar lordosis; TLK, thoracolumbar kyphosis.
There is no other supporting data.
The study has been approved by the Ethics Committee of Fatimawati General Hospital in Jakarta. Privacy and personally identifiable information are protected. Obtained the patient's informed consent for access to medical records.
My manuscript does not contain any personal data. The co-authors agreed to publish this article.
All authors have made significant contributions to the work of the report, whether in terms of concept, research design, execution, data acquisition, analysis, and interpretation, or in all these areas; participating in drafting, revising, or critically reviewing articles; final approval requirements Published version; agreed on the journal to which the article was submitted; and agreed to be responsible for all aspects of the work.
This research did not receive any specific funding from funding agencies in the public, commercial, or non-profit sectors.
The authors declare that they have no competing interests.
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