The literature has not established the limits for an indication of reconstructive vertebral surgery in patients with severe restrictive disease. Studies in pediatric patients with neuromuscular scoliosis have shown an inverse relationship between the vital capacity and the rate of postoperative complications [7]. Anderson et al. [1] reported a series of risk factors for the development of postoperative pulmonary complications in patients undergoing scoliosis surgery: scoliosis with a non-idiopathic etiology, obstructive lung disease, arterial hypoxemia, mental retardation, age less than 20 years, and anterior fusion. In our series, two of the criteria for inclusion were age under 19 and FVC less than 40% of the theoretical value. There was only one patient with psychomotor retardation, although all except one had scoliosis with a non-idiopathic etiology. These factors may have contributed to the development of postoperative lung complications in 25% of the series.
Spinal bracing using rigid jackets is an important stage in the management of scoliosis, particulary in children with muscle weakness. In these cases, the brace has most often considered a means of delaying the deformity progress and thus postponing surgical spinal fusion or as sitting support. Spinal bracing on respiratory function in neuromuscular disease results in a considerable reduction in FVC [2, 11]. Olafsson et al. [6] reviewed 90 patients with neuromuscular diseases and progressive spine deformity, treated with soft Boston orthosis. The mean pretreatment Cobb angle was 47°, with a mean brace-induced Cobb angle correction of 60%; after a follow-up of 3.1 years, the treatment was considered successful (<10° curve progression) in 23 patients. They concluded that brace treatment in neuromuscular scoliosis, except as a sitting support, can be questioned.
According to Wazeca et al. [13], one of the main risk factors for the development of postoperative lung complications is treatment with anterior fusion, and the risk increases if the procedure includes a thoracotomy. Five patients in our series were treated with a double approach, and respiratory complications occurred in the two patients who underwent the operation in a single stage. Among the 19 patients who were treated with posterior surgery alone, four (21%) experienced postoperative respiratory complications.
Pulmonary function is severely affected following scoliosis surgery [14]. In the immediate postoperative period, the functional respiratory test values decrease by up to 60% of the preoperative values, at 1 week, respiratory function is at 50%, and at 1 or 2 months, functional results return to the normal preoperative values, with no significant differences in the magnitude of the postoperative decrease according to the etiology of scoliosis (among 24 cases, 46% were idiopathic and 38% neuromuscular scoliosis), or the approach used in the surgical procedure. In a study including 298 scoliosis patients, Zhan et al. [15] reported the following rates of postoperative pulmonary complications as related to the preoperative FVC values: FVC 60–80% of theoretical, complications 2.72%; FVC 40–60%, complications 7.4%; and FVC less than 40%, complications 31.6%. In addition, the authors found statistically significant differences in relation to the surgical approach (complications were 18-fold more frequent in patients undergoing a transthoracic approach than in those treated by posterior fusion, p < 0.05). The potential impact of the etiology of scoliosis was not investigated.
In all the patients included in the present study, FVC was less than 40% of the theoretical value and in 71% the etiology was neuromuscular; the rate of postoperative pulmonary complications was 25%. In our opinion, the etiology of scoliosis is a risk factor for the development of postoperative pulmonary complications and for inability to recover lung function. Whereas in idiopathic scoliosis the deformity itself is the cause of functional deterioration, in patients with neuromuscular disease the underlying disease persists even after the deformity is corrected. As to the status of lung function at long-term, some studies have provided evidence of improved pulmonary function at 1–2 years following surgery [5, 8], whereas in others this improvement was not observed [4, 10, 12]. In the present study, FVC was 26% (range 13–39%) of the theoretical value preoperatively. In Fig. 1, we can see the improving of the pulmonary function after the surgery: at 16 months (range 12–25 months) FVC was 27.4% (range 21–40.7%) of the theoretical value and 33% (range 16–47%) at a mean follow-up of 30 months (range 20–33 months); ventilatory support was discontinued in 3 patients, 7 continued without support, and 12 continued with ventilation. Figure 2 shows the evolution of the pulmonary function of two subgroups of patients: posterior fusion and anterior and posterior fusion. It shows that in anterior and posterior group, the postoperatory FVC is higher than the preoperative results; we think that this result can be explained because patients in double approach were not neuromuscular patients, so when you get the fusion, they suffer an improve in their pulmonary function.
There were only three articles in the literature whose results could be compared with those of the present study, although the criteria for inclusion differed. Wazeka et al. [13] performed a retrospective study in patients with FVC less than 45%, age under 21, and severe thoracic scoliosis (21 cases). Rawlins et al. [9] reviewed patients with restrictive lung disease and FVC less than 40%, age under 18 and vertebral deformity (32 patients). Gill et al. [3] prospectively studied patients with progressive scoliosis, myopathy and respiratory failure (8 patients). The findings from our group of patients and the results from these studies are summarized in Table 1.
Table 1 Summarization of results of several series
What we wish to emphasize from these data is the low rate of major postoperative complications in our group of patients. Table 2 shows the complications of posterior fusion and anterior and posterior fusion. We can see that 9 of 19 of posterior fusion has no complications, but 1 of 5 in the anterior and posterior fusion. In this last group, two major respiratory complications happened. We explain it because in the anterior approach (thotacotomy and thoracolumbotomy) you need a selective intubation in one lung, and the recovery of the pulmonary function is worst.
Table 2 Complications in posterior fusion and in anterior and posterior fusion
We believe that this low rate of major complications is because multidisciplinary treatment was provided preoperatively and postoperatively, and few patients underwent corrective surgery involving a double approach. Many of our patients were admitted to the hospital some days before surgery to undergo extensive nutritional and respiratory preparation, together with methods for orthopedic skeletal traction, which make management of the deformity at the time of surgery less complex.