Here, there was no significant difference in the causes of scoliosis among patients at different altitudes (P = 0.291). The average age of patients in the H-A group was higher than that in the L-A group, although there was no significance (P = 0.064). However, the height and weight of the patients in the H-A group were significantly lower than that in the L-A group (P < 0.05), and the BMI of those in the H-A group was significantly lower than that of those in the L-A group (P = 0.036). Moreover, T1-S1 range and T1-T12 range in the L-A group were significantly higher than those in the H-A group preoperatively. The Cobb angle was more serious in the H-A group than in the L-A group preoperatively, although there was no statistical significance(P = 0.064). TK and LL in the H-A group were significantly larger than those in the L-A group(P = 0.01 and P = 0.05, respectively).Related internal and medical complications were more common in patients with larger thoracic kyphosis; if the thoracic kyphosis exceeds the normal value, the rods and foundation anchors may bear more pressure and aggravate the failure of fixation.15
Here, TK in the H-A group was significantly higher than that in the L-A group. This may be related to hypoxia, poor economic conditions, and malnutrition in children living in high-altitude areas, which is similar to the results of previous studies as it has been reported that the nutritional status of Tibetan children is poor, and their incidence of malnutrition as well as dysplasia is high, which is related to high altitude.11The risk of stunting is 2–6 times higher in children living over 3,500maslthan those living over 3,000masl. Moreover, the effect of high altitude on growth retardation persists in both young and older children.13Long-term malnutrition causes irreversible neurodevelopmental delays, leading to increased morbidity and mortality.16In particular, over one-third of children have stunted growth and are underweight, which are related to altitude, and the prevalence of stunting and underweight increases with altitude, increasing the dose-response relationship. Although socioeconomic factors play an increasingly important role in the growth of Tibetan children, altitude effects must be considered.14Altitude significantly increases the risk of neurodevelopmental problems in the first two years after birth. Moreover, it may significantly increase the risk of neurodevelopmental problems as high altitude increases the risk of neurodevelopmental diseases in women by 3 times, and in men by 1.9 times. This may be because firstly, oxygen levels are low and uterine blood flow is reduced in high-altitude areas, resulting in decreased oxygen flow to the fetus, which may cause permanent nerve damage; secondly, high altitude may also have adverse effects on maternal health, such as an increased risk of preeclampsia and pregnancy-induced hypertension, thereby affecting fetal development.13The incidence of rib deformity in children with congenital scoliosis at high altitudes is high, and their degree of rib deformity is serious.12
EOS is an extremely complex disease, and various pathogenic factors lead to several prognostic changes; if not promptly treated, scoliosis will gradually worsen, which may lead to shortening of the trunk, hindering of lung development, and early heart and lung failure.16Progressive scoliosis reduces chest compliance and shifts and rotates the contents of the chest cavity, resulting in asymmetry in lung size.4The treatment of severe spinal deformity in children is a huge challenge, the failure rate of non-surgical treatment is high, and spinal fusion correction can lead to a short trunk.5The core concept of the treatment of EOS is to maintain growth while controlling further aggravation of the deformity. TGR technology has achieved good clinical effects in the treatment of EOS.8,10,16A single rod can achieve a good clinical effect,although it cannot provide sufficient spinal support when the patient is active.6The dual growing rod technique can achieve better coronal correction rate and lengthening.6,17Despite satisfactory deformity correction and skeletal maturity, permanently retaining the double growing rod can be considered.18
Mahdavi used double growing rods to treat 22 patients with EOS, in which the Cobb angle of the patients changed from 52 ± 24° preoperatively to 38 ± 19° at the last follow-up, and the thoracic kyphosis angle was changed from 78 ± 22° preoperatively to 60 ± 17° at the last follow-up,although the incidence of implant-related complications was high at 54.5%17. In our previous study, the growing rod treatment of early-onset scoliosis, in which main thoracic scoliosis and thoracic kyphosis were significantly improved at the last follow-up indicators compared with preoperative18.Single growing rods can effectively improve the angle of scoliosis and maintain spinal growth, although they are not equivalent with the dual rods in preventing internal fixation breakage and maintaining the corrective angle.19In our study,30 patients (83.3%) were treated with a single rod, and 6 patients (26.1%) were treated with a dual rod(P < 0.05).Dual rod surgery has been mainly completed recently because the foundation has funded the treatment of children in high-altitude areas, with a total of 12 patients in the H-A group and 18 in the L-A group who underwent subcutaneous growing rod implantation, while the other patients were implanted growing rods submuscularly(P = 0.871).A meta-analysis of single and dual rod treatment of EOS have showed that dual growing rod implantation can achieve better deformity correction and spinal growth. The incidence of complications related to internal fixation is low, while the dual rod group internal fixation has a high complication rate.20Here, although there were differences in the application of single and dual rods in the two groups, both rod types achieved good therapeutic effects.
The incidence of IRC for spinal surgery was 0.19%, and the incidence of IRC for three-column correction surgery for spinal deformity was 40.2%.21Traditional growth rod technology not only improves the longitudinal growth of the thoracic cavity but also increases the width of the thoracic cavity; thus, the volume of the thoracic cavity can be significantly increased during the treatment process. However, as the age and the number of extensions increase, the width of the thorax (TD) decreases, which is related to the stiffness and spontaneous fusion of the spine; however, the authors also pointed out that for patients with severe EOS, growth rod implantation cannot be postponed because multiple adjustment rod operations can cause an increase in the absolute value.3The incidence of surgical complications was relatively high at 58%-79% in the treatment of EOS, and repeated anesthesia and surgical procedures are major problems.8,10,16The incidence of internal fixation-related complications was 54.2%,and the incidence of surgical site infection was 22.7%.17Bouthors retrospectively analyzed 34 patients with single growth rods for EOS. Although single growth rods can achieve good results in deformity correction and maintenance of spinal growth, the IRCs are especially high. Hence, it is recommended that dual growing rods beused for patients over 8 years old as such rods can better prevent breakage and maintain the orthopedic effect for patients with satisfactory orthopedics after bone maturity. Additionally, dual growing rods can be retained instead of performing final fusion surgery.19
In our study, the overall incidence of complications in the H-A and L-A groups was 60.9% and 63.9%, respectively, and the difference was not statistically significant(P = 0.815).The incidence of implant-related complications in the L-A group(63.9%) was higher than that in the H-A group(52.2%), but the difference was not statistically significant (P = 0.372).Most children with EOS in the H-A group have been subsidized through spinal rescue action recently, and the progress of the treatment concept, the improvement of surgical techniques, and the improvement of internal fixation equipment all promote further reduction of implant-related complications.
Our study has several limitations. First, this was a retrospective study, and there was no randomization between the H-A and L-A groups. Second, the number of patients was relatively small; thus, a larger number of patients and longer follow-up are needed. Third, the operative time of most patients in the L-A group was shorter than that in the H-A group, and the proportion of patients using a single rod or dual rod was very different between the groups, which may have affected the study results.