Before reading this article, we sincerely invite you to click "Follow", which is convenient for you to discuss and share, but also to share more professional health knowledge to escort your health, thank you for your support.
Juvenile idiopathic scoliosis (AIS) is a three-dimensional spinal deformity involving coronal, sagittal and axial positions, which not only causes physical development deformities, but also easily produces inferiority complex, which seriously affects the physical and mental health of adolescents. Severe thoracic scoliosis can also compress the patient's heart and lungs, causing a decrease in mobility, further aggravating the development of scoliosis.
The incidence of spine in the mainland Han population is about 2.4%, and the incidence is higher in women than in men. The pathogenesis of AIS is not fully understood, and it may involve genetic factors, bad habits, stunted development and other factors. Mild scoliosis can be corrected to some extent with conservative treatments such as braces, massage, and postural training.
However, because the epiphysis is not completely healed in adolescents, brace therapy can not effectively prevent the further development of scoliosis, and about 40% of patients are eventually or unable to avoid surgery, and surgical treatment is still the most effective way to treat idiopathic scoliosis in adolescents.
There are clear indications for surgical treatment, that is, for AIS thoracic Cobb angle > 40°, lumbar spine Cobb angle > 35°, or Cobb angle increase by more than 5° within 1 year, spinal surgery orthopedic treatment is usually required, the history of surgical scoliosis can be traced back to the 60s of the last century, mainly through spinal fusion and Harrington rod for spinal fixation.
In the 90s of last century, it was first reported that pedicle screws were used for scoliosis orthosis. With the development of surgical techniques to the present, more and more scholars advocate better coronal position, sagittal orthopedic and more reliable internal fixation by posterior pedicle nail, and have fewer complications than previous hybrid or hooked structures.
The pedicle screw structure is inserted into the vertebral body and can act directly on the vertebral body. It can provide a stronger three-dimensional correction effect than hybrid instruments, but in scoliosis, many vertebral bodies rotate or develop abnormally.
As a result, the shape of the pedicle is relatively abnormal, and even if the surgeon is careful, it is inevitable that the pedicle nail placement deviation may lead to spinal cord, nerve and even large blood vessel damage. This makes pedicle screw placement often difficult and their use in the thoracic spine more limited.
In recent years, with the advancement of surgical technology and the development of surgical robots, navigation technology and neural monitoring systems have made pedicle nail placement for scoliosis have a slightly lower learning curve, but in academia, how much nail placement can achieve satisfactory correction effect is still very controversial.
At present, the definition of low screw density and high screw density in academia is still unclear and there is no gold standard. Many scholars have explored this issue and come to very different conclusions.
Studies have concluded that the low screw density structure can achieve the same correction effect as the high screw density structure, and there is no significant difference in the correction degree and correction rate of the main thoracic curvature before and after surgery in the subgroups with different screw densities. Thirty-one patients with Lenke-type scoliosis were followed for up to two years, and no significant differences were observed.
However, the result is different, that is, the high screw density structure and the lower screw density structure can provide a more powerful correction effect. A retrospective analysis of 584 patients with Lenke1 AIS showed higher anchor density on X-ray and higher curve correction rates. It is believed that continuous screw placement is better than intermittent screw placement.
Our goal was to explore whether a high screw density structure leads to better coronal correction of juvenile idiopathic scoliosis. We found no significant difference in pooled data on the Cobb angle of the main curve in nine studies (p=0.02, I2=53%) in nine studies.
However, our analysis found no clear difference in the preoperative Cobb angle in 13 studies (p=0.004, I2=59%), but at the last follow-up (p=0.06, I2=0.04%).
A retrospective analysis of 39 patients with Lenke5 type posterior scoliosis internal fixation orthopedic results showed that pedicle insertion density was significantly positively correlated with coronal curve correction rate (r=0.43, P=0.006).
This is consistent with the reported results, which retrospectively analyzed 292 patients who underwent scoliosis surgery at multiple centers and followed up for 2 years, and found that implant density after 2 years was significantly correlated with the rate of main curve correction (R=0.31, p<0.001).
Looking back at previous research, we have asked whether the same pattern exists in previous scoliosis orthopedics, so we retrospectively analyzed scoliosis orthopedics performed in the past 8 years and obtained similar answers.
The Cobb angle improvement was greater in the high screw density structure group (p=0.0016) and the correction rate was also greater (p<0.0001), and the screw implantation density was significantly positively correlated with the correction rate.
This proves that high-density screws can provide a more robust coronal correction. One of the reasons why low-screw density structures cannot achieve the same correction may be that low-density screws cannot withstand the abnormal biomechanics of the spine, because there are no more anchor points, resulting in screw stress concentration, unable to maintain the same correction effect as high-density screws, and may even lead to internal fixation failure.
The curve flexibility of the high screw density structure group was lower than that of the screw density group (p=0.0139). MingLi believes that factors that determine the degree of correction of posterior surgery in Lenke1AIS patients include the size and flexibility of curvature, the degree of surgical release, and the number of fixed points. In this study, it is believed that the structure with high screw density can provide a stronger coronal position correction effect.
Sagittal correction is also one of the goals of scoliosis internal fixation orthopedics, and improper physiological sagittal curves may cause patients to be more prone to fatigue, fatigue, and even increased pain, unable to maintain an upright posture normally. We analysed preoperative thoracic kyphotic angles reported in 11 studies and included 657 patients and found no significant differences (p=0.31, I2=14%).
Data from the last follow-up were pooled with thoracic kyphosis and the same conclusion was found (p<0.00001, I2=85%). Obviously, screw implantation density did not differ significantly for thoracic sagittal correction. However, we can see that the heterogeneity of thoracic kyphosis deformities after each study was performed.
Because the angle of thoracic kyphosis recorded varied greatly in each study. Similar results were obtained in our retrospective study, and there were no significant changes in cervical curvature or thoracic curvature before or after surgery.
Although not statistically significant, thoracic kyphosis increased compared with preoperative period, and most patients can reach the range of 20°<TK<40°, and the internal fixation structure of pedicle screws can provide some orthosagittal orthopedic of the thoracic spine. An analysis of 34 patients with scoliosis undergoing surgery found that patients who received total pedicle screws had greater thoracic kyphosis losses than mixed structures.
Our study found no significant loss of thoracic kyphosis, or even a slight increase. It was noted that screw fixation improved the overall sagittal parameters and allowed postoperative recovery of thoracic kyphosis angle, which is similar to the results we found.
This has something to do with the surgeon's surgical technique, and seeking an overall transposition of the spine during surgery, rather than a direct segmental transposition of the affected vertebral body, may provide better thoracic kyphosis recovery. In the high screw density structure group, the postoperative lordosis angle of the lumbar spine was greatly reduced compared with that before surgery.
This suggests that high screw density may have reduced lordosis, but no imbalance was found during follow-up to prevent the patient from standing. It was concluded that screw structure can provide limited thoracic kyphosis correction, independent of screw density; However, high-density screws may reduce lumbar lordosis.
A few studies have mentioned axial correction. The torso rotation angle was assessed using a measuring instrument before surgery and at the last follow-up visit and found no difference in rotational correction between high- and low-density pedicle screw structures. Cross-sectional assessment was performed indirectly by imaging preoperative and postoperative costopal deformity.
They also did not find any significant correlation between implant density and photographic parameters related to rotation. Ismail Emre Ketenci used Perdriolle and Vidal12 methods to measure parietal spine rotation and found that the parietal spine rotation correction effect was better in the high screw density structure group, which was related to the three-dimensional correction ability of pedicle screw structure.
Alexandre Delikaris, Meng analyzed the rotation angle of 140 AIS surgeries and found that increasing screw density had a significant positive effect on rotational recovery (r-0.887, p<0.05). In our retrospective analysis, imaging data corresponding to spinal rotation were lacking and no further evaluation was possible.
More research attention is needed in the long term. The difference in surgery time is a topic that has been discussed in the past. Eight studies reported on time to surgery.
Pooled analysis found significant differences between the two groups (p=0.22, I²=26%). Kemppainen retrospectively analyzed 52 patients with AIS who underwent surgery and found a significant difference in the low screw density group with a time to surgery of 267±43 compared with 309±59 for the high density group (p=0.007).
It suggests that the operation time was shorter in the low-density screw group than in the high-density screw group. Unfortunately, there was considerable heterogeneity in the duration of surgery in the included studies (I2 = 87%) in the face of this problem.
It is well known that the most difficult type of spinal surgery is scoliosis surgery, where the number of pedicle screws implanted can be between 10 and 20 or even more. Surgical time is highly dependent on skill and surgeon experience, and heterogeneity in surgical timing is common.
In our retrospective analysis, there was no significant difference in the operation time between the low screw density structure group and the high screw density structure group (p=0.4442), and the operation time of continuous nail placement and intermittent nail placement was similar.
There was no significant difference in the time to surgery, we believe that the year of surgery was generally earlier in the low screw density group than in the high screw density group, and that a higher learning curve may have led to a longer duration of early scoliosis surgery, which affected our judgment.
Surgery time is a key factor influencing intraoperative and postoperative infections, shortening surgery time reduces the likelihood of postoperative complications, and we know that if a patient suffers from surgical complications, the additional cost will increase accordingly and the length of hospital stay will increase accordingly.
The cost of AIS surgery is high in both developed and developing countries, placing a huge financial burden on patients, health care systems and countries.
It was found that the proportion of screw costs in hospitalization costs may reach up to 50%, and this figure can be reduced to 20%-30% when screw density is reduced. In our retrospective analysis, total hospital costs were 20% higher in the high screw density group than in the low screw density group.
This is consistent with the conclusions of Tsirikos, who analyzed the cost of surgery in 212 patients with AIS, with lower implantation costs in the low screw density group due to the reduced number of pedicle screws. An average reduction of 35%. Surgical bleeding is also a factor that affects the progress of a patient's postoperative recovery. Eight studies reported surgical bleeding.
The low screw density group was found to have the characteristics of low bleeding. The intraoperative blood loss of the two groups was calculated and it was found that the high screw density group had more blood loss (p=0.048).
In our retrospective analysis, the amount of bleeding in both groups, although higher in the group with high screw density, was not significant (p=0.1874). In the statistics of 56 patients who underwent AIS surgery, the intraoperative blood loss showed that there was no significant difference between the intermittent nail placement group and the continuous nail placement group (p=0.376).
This suggests that there may not be a strong relationship between the amount of bleeding and the number of nails. Complications include short-term complications such as infection, nailing, hematoma, nerve damage, etc., and long-term complications such as flat back, revision, etc.
The meta-analysis found no association between screw density and complications in the included studies. In our retrospective analysis, 3 cases of postoperative short-term re-nailing and 1 case of posterior mediastinal hematoma occurred in the low screw density group; One case of incision infection occurred in the high screw density group. There was no significant difference in the incidence of complications between the two groups.
However, a review of 80 patients with AIS who underwent surgery and followed up to 5 years found that the revision rate of high screw density structures was lower and that of the screw density group was low.
This also needs to be supported by a greater amount of evidence. Quality of life assessment is what our meta-analysis wanted to know, but the method of assessing QOL results was different from study to study.
It is difficult to quantify uniformly. However, all the scoring criteria showed no significant difference in quality of life between the two groups. The SRS-22 rating scale was used to evaluate the quality of life of the two groups, and there were no differences in performance (p=0.23), mobility ability (p=0.84), pain (p=0.34), mental state (p=0.74), satisfaction (p=0.85) and total score (p=0.66).
In our retrospective analysis, VAS scores were used to assess discomfort before, after and at follow-up, and there was no clear difference between the two groups. This suggests that screw density did not affect the patient's quality of life.
In general, the high screw density structure can achieve better coronal position correction, a certain degree of thoracic kyphotic correction, poor axial correction effect, but will lose a certain lumbar lordosis, the impact on patients needs to be observed in the long term;
Low screw density has a lower economic burden, and lumbar lordosis is not significantly lost; There was no significant difference in operation time, surgical bleeding, and postoperative quality of life.
The high screw density structure allows for better imaging results, but the postoperative quality of life, length of surgery, surgical bleeding outcomes are the same, and the patient's complications are the same.
Due to the large economic burden on the patient, the cost of a structure with high screw density increases with the number of pedicle screws and should be considered. However, although the correction effect of the low-density screw group was slightly worse than that of the high-density screw group, the cost of surgery was lower than that of the high-density screw group. How to balance the corrective effect and the cost of surgery is a big problem that needs to be solved in the future.