In the patients who had undergone corrective surgery to treat scoliosis, the BMI, pre-operative pulmonary function test results, Cobb angle, number of fused vertebrae, operating time, and intra-operative blood loss differed by age, but the incidence and types of post-operative complications did not differ by age. In both the pediatric and adult patients, the Cobb angle and the amount of transfused concentrated red blood cells were related to the incidence of complications. The pre-operative decreased pulmonary function led to an increased incidence of complications in A20, but was not related to the incidence of complications in U20.
Takahashi et al. [5
] reported that older patients who had undergone corrective scoliosis surgery were, the stiffer the spinal curvature was, which made correction even more difficult; and Nachemson [12
] reported that adult patients who had concomitant thoracic scoliosis had increased risks of post-operative complications and death because of cardiopulmonary dysfunction. In addition, Anderson et al. [11
] reported that of the patients aged 1-34 years who had undergone spinal surgery, those who had undergone the surgery when they were more than 20 years old had a higher incidence of post-operative pulmonary complications. In addition, Patil et al. [13
] reported that pediatric patients (aged 0-17 years) had a better short-term prognosis after corrective spinal surgery than adult patients. In this study, the incidence and types of complications did not differ between the U20 and A20. In A20, however, the post-operative hospital stay was significantly longer; and although the Cobb angle and the number of fused vertebrae were greater in U20, the operating time and the intra-operative blood loss were higher in A20. The absence of differences between the 2 groups in this study is believed to be because the overall incidence of complications was low (11%), and the total size of A20 was small, with only 152 patients.
Regarding the relationship between the Cobb angle and the post-operative complications, Gibson [14
] reported that at a Cobb angle of 65° or more, the pulmonary volume decreased and disharmony between the ventilation and perfusion occurred; and a Cobb angle of above 100° resulted in pulmonary hypertension and right ventricle hypertrophy. Kang et al. [4
] also reported that a Cobb angle of 69° or more resulted in increased post-operative pulmonary complications and the need for mechanical ventilation. On the other hand, Modi et al. [15
] reported that the extent of spinal deformity did not increase with the incidence of post-operative complications and the risk of ICU treatment. In this study, the increased Cobb angle resulted in an increased risk of post-operative complications in both groups. But, of the 15 patients with a Cobb angle of 100° or more, no patient experienced respiratory complications and one patient died as a result of a myocardial infarction during surgery. These might have been because physical therapy was performed for several months before the surgery on the patients with a pre-operative Cobb angle of 100o or more to reduce the angle, and pediatric clinicians and rehabilitation medicine clinicians were fully aware of the related risks and thus, paid attention.
Of the risk factors of the occurrence of complications after scoliosis corrective surgery, the influence of the pre-operative pulmonary function test on the occurrence of post-operative complications is still debatable. Udink ten Cate et al. [16
] reported that in patients with neuromuscular scoliosis, the pre-operative pulmonary function test was a useful predictor, and vital capacity (VC) was a particularly important predictor of the need for post-operative mechanical ventilation. Yuan et al. [17
] also reported that the pre-operative pulmonary function test was a prognostic factor that increased the need for post-operative mechanical ventilation in pediatric patients with scoliosis. On the other hand, Wazeka et al. [1
] reported that of 21 patients with severe restrictive pulmonary dysfunction, only 4 patients required long-term mechanical ventilation; and Marsh et al. [18
] reported that in 30 patients with neuromuscular scoliosis, there was no difference between the post-operative complications of the group with a VC of 30% or more and the group with a VC of less than 30%. Harper et al. [19
] reported that in 45 patients with Duchenne's muscular dystrophy, there was no difference between the complications of the group with an FVC ratio of less than 30% and the group with an FVC ratio of 30% or more. Whether or not the pre-operative decreased pulmonary function is a risk factor of post-operative complications in patients with idiopathic scoliosis remains debatable [20
]. In this regard, Kang et al. [4
] reported that the controversy on the impact of the pulmonary function test on the occurrence of complications was due to the low incidence of complications in patients with scoliosis. In this study, decreased pulmonary function did not increase the incidence of complications in pediatric patients, but influenced the occurrence of complications in adult patients. In this study, risk factors of respiratory complications could not be identified because of limitations in the statistical significance, as the overall incidence of complications was 11%, and only 18 (11.8%) of the 152 patients aged 20 years or more had complications, with only 5 patients having respiratory complications. Additional studies are required that include a higher number of patients with respiratory complications.
Smith et al. [22
] reported that pediatric patients who had undergone scoliosis surgery and had a lower BMI, the greater the risk of superior mesenteric artery (SMA) syndrome. Hassan et al. [23
] reported that in 106 patients who had undergone scoliosis surgery, the lower the BMI, the higher the blood transfusion amount required. In contrast, Chen et al. [10
] reported that in adults, the higher the BMI, the higher the occurrence of spinal deformity and the greater the post-operative pain, although the higher BMI did not increase the incidence of post-operative complications. In this study, the SMA syndrome occurred in 2 patients, but the BMIs between U20N and U20C did not differ; and in the adult patients, a decreased BMI increased the incidence of complications. It is believed that the results of this study differed from those of Chen et al. [10
] because a low BMI reflected a poor nutrition state rather than an increased BMI reflecting obesity.
In the pediatric patients with scoliosis, those who had comorbidites showed an increased incidence of complications. Taggart et al. [8
] reported that although posterior spondylodesis is safe in most patients aged less than 18 years with congenital heart disease, those with concomitant severe pulmonary hypertension are at an increased risk of death. Bitan et al. [24
] reported that of 44 patients with congenital heart disease who had undergone spondylodesis, one patient died during the surgery and one patient had an intra-operative cardiac arrest, but was resuscitated via cardiopulmonary resuscitation. Coran et al. [25
] reported that of 74 patients with congenital heart disease, 2 died and 24% had complications. In this study, one patient with congenital heart disease had pre-operative concomitant mild pulmonary hypertension, and at day 1 post-operatively, experienced decreased blood pressure, increased pulmonary arterial blood pressure, and heart failure.
There were 12 patients had mental retardation, of whom 2 showed concomitant cerebral palsy. Wongprasartsuk and Stevens [26
] reported that in cases of anesthesia administration in patients with cerebral palsy, communication difficulty and musculoskeletal-abnormality-related difficulty may occur; and that with the use of a muscle relaxant, problems such as increased sensitivity to succinylcholine, resistance to vecuronium, minimal alveolar concentration of an inhalation anesthetic agent, and difficulty in postoperative extubation. In this study, rocuronium and vecuronium were used as a muscle relaxant, and no related problems were observed. One patient with cerebral palsy died during surgery; and a second patient with an endotracheal tube in place was transferred to the ICU and the tube was removed later in the ICU without specific complications.
Since Sunohara et al. [27
] reported in 1984 on scoliosis and malignant hyperthermia, numerous cases of malignant hyperthermia that occurred in patients with scoliosis had been reported [28
]. Since 2008, in this study, TIVA has been performed using propofol and remifentanil. TIVA lowered the risk of malignant hyperthermia and enabled intra-operative identification of neural damage by enabling monitoring of somatosensory-evoked potential and motor-evoked potential [29
]. The intra-operative effect site concentrations of propofol and remifentanil were 2.5-3.0 µg/ml and 15-20 ng/ml, respectively, with target-controlled infusion.
In one patient with neuromuscular scoliosis caused by cerebral palsy who died of post-operative complications, acute myocardial infarction occurred during the course of the spinal correction. Of the patients with cardiovascular complications, 2 transiently developed atrial fibrillation after the surgery but had a normal electrocardiograph within 1 hour. The 9 patients with gastrointestinal complications, whose AST and ALT levels were 3 times or more than the normal level, were diagnosed with hepatitis caused by a non-steroidal anti-inflammatory agent. Of the total 602 patients, 18 patients were transferred to the ICU with an endotracheal tube in place and 7 patients developed respiratory complications. Two patients developed respiratory complications due to intra-operative pneumothorax and hemothorax, and another 5 developed respiratory complications due to a large intra-operative transfusion, pulmonary edema caused by heavy bleeding, or hemodynamic instability. An additional 9 patients were transferred to the ICU with an endotracheal tube in place because they were diagnosed with severe restrictive ventilatory defect in the pre-operative pulmonary function test or because the removal of the tube was deferred due to severe mental retardation; in all of these patients, the endotracheal tube was removed within 2 hours.
This study had limitations in its regression analysis because of the low incidence of complications, and thus, we couldn't identify all significant variables of the univariate regression analysis were independent risk factors for post-operative complications. In addition, the correlation between each risk factor and the pulmonary or cardiovascular complications could not be identified. Regarding this, further studies with additional data are required. Also, there may have been some missing data among the hospital and clinical charts. Last, this was a retrospective study and the results are compromised as a result of relatively limited sample and a non-randomized design.
In conclusion, there was no difference in the incidence of complications between the pediatric and adult patients after scoliosis corrective surgery, but there was a difference in the correlation factors of the occurrence of complications between the 2 groups. In all ages, the larger the pre-operative Cobb angle, the increase in operating time, duration of anesthesia, and required amounts of intra-operative red blood cell transfusions which resulted in a higher incidence of post-operative complications. In the adults, a pre-operative deteriorated pulmonary function increased the incidence of complications; and in the pediatric patients, comorbidities affected a patient's outcome.