Here, no significant difference was noted 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 this difference was not significant (P = 0.064). However, the height and weight of the patients in the H-A group were significantly lower than that inthe 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–S1heightand T1–T12 height in the L-A group were significantly higher than those in the H-A group preoperatively.The Cobb angle was more severe in the H-A group than that in the L-A group preoperatively,although this difference was notsignificant (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).The height, weight, BMI, T1–12, and T1–S1 of patients with EOS living in high altitude areas were lower than those of patients in low altitude areas, which may be related to poor nutritional status and long-term hypoxic environment of children in high altitude areas. Severe spinal deformities were more common in children in high altitude areas, and also associated with small thoracic volume. The results showed that 73.9% of the patients in the high altitude group were treated with dual rods, while only 16.7% of the patients in the low altitude group were treated with dual rods.No significant difference was noted in the complications between both groups. Patients with scoliosis in high altitude areas have been given increasing attention and treatment has been focused on them, which may be related to the improvement of concept and technology, and the progress of internal fixation technology.Related internal and medical complications were more common in patients with larger TK; if the TK 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.TK is an important parameter to evaluate the severity of scoliosis. The increase or decrease of TK will affect the curative effect and complications of growing rod surgery for EOS. In a previous study, a surprisingly strong correlation between TK and Cobb has been reported.16 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 another previous study reporting that the nutritional status of Tibetan children is poor, and their incidence of malnutrition and dysplasia is high, which is related to high altitude.11The risk of stunting is 2–6 times higher in children living over 3,500mthan those living over 3,000m. Moreover, the effect of high altitude on growth retardation persists in both young and olderchildren.13Long-term malnutrition causes irreversible neurodevelopmental delays,leading to increased morbidity and mortality.17In 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 severe.12
Children with EOS in high altitude areas have poor nutritional status, shorter height, lighter weight, severe spinal deformity,which may be combined with spinal cord or vascular malformation, thoracic deformity, small thoracic volume, worse cardiopulmonary function, and commonly have restrictive ventilation dysfunction, and even respiratory failure.Therefore, more comprehensive preoperative evaluation is needed because Tibetan children in high altitude areas have language communication difficulties. Thus, health education should be carried out for these children,and preoperative nutrition and balloon blowing exercise are needed.Preoperative traction treatment and intraoperative nerve electrophysiological monitoringshould be used.Dual rods implanted subcutaneously should be used as much as possible to maintain spinal growth, especially for children with EOS in high altitude areas. However, for patients with poor nutritional status and larger Cobb angle, inserting dual growing rods may be difficult,and the anchoring strength of the lower and upper internal fixation should be increased as much as possible to ensure the role of growing rods in spinal correction.During the operation, the integrity of the capsule and the posterior ligament of the adjacent segment of the fixed vertebrae should be protected to prevent the failure of internal fixation.The first operation and each distraction operation are carried out under spinal cord monitoring, and the intraoperative blood pressure of patients is always a concern. Once the spinal cord monitoring signal appears abnormal during the operation, the factors that may lead to nerve injury should be investigated first, the distraction should be relaxed, the blood pressure changes should be checked, and hormonal treatment should be done.As patients in high altitude areas are mostly Tibetan children and their language communication may not be smooth, X-ray taking cannot be done on time,so there may be difficulty ingrowing rod adjustment. Thus, more attention should be paid to the healthcare of patients in high altitude areas.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.17Progressive 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.8,10,17 A 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.6,18 Despite satisfactory deformity correction and skeletal maturity, permanently retaining the double growing rod can be considered.19
Mahdavi18 used double growing rods to treat 22 patients with EOS,in which the Cobb angle of the patients was changed from 52 ± 24° preoperatively to 38 ± 19° at the last follow-up, and the TK 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%.In our previous study, the growing rod treatment of EOS, in which main indicators of thoracic scoliosis and TK were significantly improved at the last follow-up compared with those recorded during thepreoperative period.19Single 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.20Here,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 with growing rods submuscularly(P = 0.871).A meta-analysis of single and dual rod treatment of EOS has showed that dual growing rod implantation can achieve better deformity correction and spinal growth. The incidence of complications related to internal fixation was lower in the in the single rod group than in the dual rod group.21Here, 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%.22TGR 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 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, growing 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.8,10,17The incidence of internal fixation-related complications was 54.2%,and the incidence of surgical site infection was 22.7%.18Bouthors20retrospectively analyzed 34 patients with single growing rods for EOS.Although single growing 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 be used 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.20
Here,the overall incidence of complications in the H-A and L-A groups was 60.9% and 63.9%, respectively, with no significant difference (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%), although the difference was not 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 andthe improvement of surgical techniques and internal fixation equipment all promote further reduction of implant-related complications.
Our study has several limitations.First,this was a retrospective study, and no randomization was performed between the H-A and L-A groups. Second, the number of patients was relatively small; thus, a larger number of patients and a longer follow-up period are needed. Third, theoperative 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.