The mean estimated blood loss per kg of body weight was significantly greater for the small thoracoscopic children compared to the large thoracoscopic children (P = 0.003) (Table 1). There was no significant difference in normalized blood loss between the small thoracoscopic children (13.6 mL/kg) and the small open children (16.3 mL/kg)(P = 0.4). There was no significant difference in estimated blood loss between children with a neuromuscular and nonneuromuscular diagnosis (P = 0.5;Table 2). The interaction between weight/surgical procedure and diagnosis was also not significant (P = 0.08). Examining this interaction further, there was a nonsignificant trend for neuromuscular patients to lose more blood than nonneuromuscular patients when the surgery was thoracoscopic; however, when the surgery was an open thoracotomy, neuromuscular patients were found to lose less blood than nonneuromuscular patients. A significant positive correlation was found between estimated blood loss and operative time for the small thoracoscopic children (P = 0.003), but this relationship was not significant for the other two groups (P > 0.10).
Chest Tube Output
The small thoracoscopic children had greater normalized chest tube output compared to the large thoracoscopic children (P = 0.003;Table 1). Chest tube output per kg of body weight did not differ significantly between small open children and small thoracoscopic children (P = 0.5).
Mean ICU stay was significantly greater in the small thoracoscopic children compared to the large thoracoscopic children (P < 0.001;Table 1). The average stay for small open children was not significantly different from the small thoracoscopic children (P = 0.1). Mean ICU stay was significantly greater for neuromuscular patients compared to nonneuromuscular patients (P < 0.001;Table 2). The interaction was not significant (P = 0.05); however, this nonsignificant trend indicated that neuromuscular patients had an increased ICU stay when the procedure was a thoracoscopic procedure compared to nonneuromuscular patients who underwent a thoracoscopic procedure. Intensive care unit stay for all diagnoses were similar when the procedure was an open thoracotomy.
Anesthesia Preparation Time
The mean time from induction of anesthesia until the start of surgery was significantly greater for the small thoracoscopic children compared to the small open children (P = 0.002;Table 1). There were no differences between the small thoracoscopic children and the large thoracoscopic children (P = 0.2).
The average preoperative scoliosis for the three groups was similar (small thoracoscopic children: 62°± 12°; large thoracoscopic children: 56°± 20°; small open children: 66°± 29°). The average postoperative percent scoliosis correction (for those patients in which correction was attempted) was 53%, 62%, and 37%, respectively (P = 0.06). The average preoperative kyphosis of these patients with surgically indicated hyperkyphosis was 72°± 29°, 71°± 22°, and 76°± 22° for the small thoracoscopic, large thoracoscopic, and small open groups, respectively. For the two thoracoscopic groups, the percent correction, calculated as: [preop − (postop − 40)/preop] × 100, was 95% ± 8% for the small group and 94% ± 17% for the large group. The sagittal correction of the small open group was 68% ± 9% (P = 0.04).
There were three complications in the small thoracoscopic children. Surgery was rescheduled in one 24-kg girl with neuromuscular kyphoscoliosis due to inability to selectively intubate her lungs. She was only the third patient to undergo thoracoscopic spine surgery at our institution. The procedure was successfully completed at the later date utilizing a balloon bronchial blocker. There was one conversion to open thoracotomy in a 24-kg girl with neuromuscular kyphosis. Despite repeated repositioning of a balloon blocker, there was intermittent reexpansion of the lung that prevented proper visualization. One 20-kg girl with neuromuscular scoliosis developed a pleural effusion after chest tube removal. The effusion resolved with reinsertion of the chest tube on postoperative day 6.
There were three complications in the large thoracoscopic children. One 35-kg girl with myotonic dystrophy and kyphoscoliosis had conversion to open thoracotomy due to excessive bone bleeding, which prevented adequate visualization of the spine. There was no vessel injury. One 50-kg girl with idiopathic scoliosis developed a pleural effusion after chest tube removal. Despite thoracentesis, the effusion reaccumulated, necessitating chest tube reinsertion. One 36-kg girl with juvenile idiopathic scoliosis developed chylothorax after surgery. This resolved with a low-fat diet. No further invasive measures were needed.
There was only one complication in the small open group. One 18-kg girl with neuromuscular scoliosis had excessive bleeding causing postponement of her posterior procedure. There were no neurologic complications in any of the three study groups.
Seven large thoracoscopic children, 8 small thoracoscopic children, and 3 small open children remained in the ICU for prolonged postoperative mechanical ventilation of greater than 72 hours. One of these children had scoliosis associated with a large syrinx, and the remaining children had neuromuscular scoliosis.
The authors have demonstrated the safety and efficacy of spinal thoracoscopy in a group of children (n = 33) weighing less than 30 kg. A comparison to larger children treated thoracoscopically as well as similarly sized patients treated by an open thoracotomy allowed differentiation of the effects of patient size, as well as the method of exposure–thoracoscopic versus open.
There were a number of similarities between the study groups that validate the comparisons made. The study design aimed to compare differing patient groups who had the same extent of surgery. Only patients who underwent anterior release and fusion were included in the study. None of the patients had anterior spinal instrumentation. The small open children group was limited to patients who had thoracic surgery only. Any patient with division of the diaphragm was excluded in order to maintain maximal uniformity of the surgical procedures between the open and thoracoscopic groups. The extent of the surgery did prove similar, as there was no difference in the mean operative time or mean number of discs excised between the three groups. Preoperative spinal deformity was similar in the three groups. With patients undergoing in situ fusion (congenital scoliosis) omitted from analysis, the percent deformity correction was also similar in the three groups. All thoracoscopic procedures were performed by a single surgeon. This eliminates intersurgeon variability when comparing small thoracoscopic children and large thoracoscopic children, in a technically demanding procedure with a well-documented learning curve. 7,11,13,15 The small thoracoscopic children and small open children had similar mean body weights of 22.8 kg and 19.4 kg, respectively.
Despite efforts to standardize our study groups, there were notable differences. The mean age varied between the two small children (7.8 years, open vs. 10.7 years, thoracoscopic) groups. This age difference may reflect some selection bias, as very young children may have been chosen for open thoracotomy rather than thoracoscopic surgery. However, many of the small open children were operated before our institution’s use of thoracoscopic techniques and account for the differences in the length of follow-up. The number of patients varied among the three groups. Only 25 patients in the computer database, which began in 1991, met the under-30 kg inclusion criteria for the small open children. Since the thoracoscopic technique has been used at our institution, the vast majority of patients who need anterior thoracic release and fusion are treated by the less invasive thoracoscopic method. The group of large thoracoscopic children represent 48 patients from a previously published study who weighed over 30 kg. 13 The remaining 17 patients from that study are included in the group of 33 small thoracoscopic children. The small thoracoscopic children represent approximately one-fourth of all patients who have undergone thoracoscopic anterior release and fusion at our institution since 1994. The predominant diagnoses in the three groups differed slightly. In the large thoracoscopic children, there was a nearly equal division between patients with neuromuscular disease (42%) and idiopathic scoliosis or kyphosis (46%). In the small open children, there were a similar number of patients with neuromuscular (56%) and congenital (40%) scoliosis. The vast majority of the small thoracoscopic children had neuromuscular scoliosis (76%). This lack of congenital scoliosis patients reflects the authors’ impression that, when two to three levels require treatment (as is often the case in congenital deformities), a limited open approach is simpler and preferred.
Four of the small open children and one patient from the group of small thoracoscopic children had staged posterior procedures. The results of analysis of the postoperative variables (time intubated, chest tube output, chest tube duration, ICU stay, and total hospital stay) did not differ with exclusion of the data from these five patients. Thus, their data were included in the study. This is also true for the three patients who had endoscopic anterior retroperitoneal lumbar surgery following their thoracoscopic procedure.
The effectiveness of curve correction varied among the three groups. Mean correction of scoliosis was 54% for the small thoracoscopic children and 62% for the large thoracoscopic children. This is similar to previous reports, where mean correction of scoliosis ranged from 42% to 77%. 8,10,11,15,20 Arlet 1 reported a 60% mean correction of scoliosis in a meta-analysis and review of 10 studies on thoracoscopic spine surgery. Mean correction of kyphosis was 95% for the small thoracoscopic children and 94% for the large thoracoscopic children in the present study. Niemeyer et al15 reported a 77% correction of kyphosis whereas King et al8 reported an 87% correction. The mean scoliosis correction for the small open children was 38%, increasing to 44% with the omission of patients with congenital scoliosis in whom in situ fusion was performed. Kyphosis correction averaged 68% in this group. In many of the small open children, postoperative casting, rather than posterior instrumentation, was used and is likely the reason for the lower percentage correction.
Normalized estimated blood loss correlated more with patient age and size than with the surgical technique employed. Both the small thoracoscopic children and small open children had over twice the volume of blood loss, per unit weight, than did the large thoracoscopic children. There was no difference between the small thoracoscopic children and the small open children, thus the method of spinal access does not explain the differential blood loss. Although the small thoracoscopic children had a high percentage of neuromuscular patients, it is unlikely that variability in diagnosis was a major factor in the blood loss differences between the thoracoscopic groups; both the small open children and the large thoracoscopic children had similar numbers of neuromuscular patients yet very different normalized blood loss values. Instead, age and vertebral body development are more important. Whalen et al22 showed that although the disc is avascular, young children have numerous arterioles and venules in their cartilaginous endplates. Ratcliffe 16 demonstrated extensive venous and arteriole anastomoses throughout the vertebral bodies of younger children. These vessels involute near age 15 years, the mean age of the large thoracoscopic children in our study. The bony endplates are thinner in young children, compared to older adolescents. This may allow more frequent entrance into the cancellous bone of the vertebra during disc and cartilaginous endplate excision, in these immature patients. Thus, in younger children, more blood loss should be expected following discectomy and endplate excision given this increased vascularity of the vertebral bodies.
The anesthesia preparation time was greater in the two thoracoscopic groups when compared to the small open children. This statistically significant difference was expected given the specialized methods of single lung ventilation required for thoracoscopic surgery. The small thoracoscopic children and large thoracoscopic children had statistically similar anesthesia preparation times and quality of lung collapse. More difficulty was anticipated with the small thoracoscopic children, and although trends supporting these ideas did exist, statistical significance was not reached. In the vast majority of large thoracoscopic children, a Univent or double lumen endotracheal tube readily allowed selective lung ventilation. These tubes are often too large for smaller children, necessitating specialized methods. This usually involves a small balloon catheter, such as a Foley, Fogarty, or balloon removed from the Univent tube that is placed adjacent to a standard endotracheal tube. The balloon is inflated in the mainstem bronchus on the operative side, allowing selective ventilation of the opposite lung. Given the number of thoracoscopic procedures performed at the authors’ institution, the anesthesiologists have become quite facile with this technique. Although one patient from each group required conversion to open thoracotomy, there was no statistically significant difference in the quality of lung collapse between the two thoracoscopic groups. At the authors’ institution, little extra time is required when standard double lumen endotracheal tubes cannot be used.
The benefits of thoracoscopy relate largely to the limited chest wall dissection that is associated with this approach. The lengths of the portal incisions are typically 15 mm. Thus, the total incision length varies between 4.5 and 7.5 cm, depending on the number of portals required. Although difficult to quantitate, it is the authors’ impression that as the size of the patient decreases, the relative benefit of the thoracoscopic approach also decreases. This is because the summed length of the portal incisions approaches that of a thoracotomy for a small child. This is especially true if only two or three levels of the spine require treatment (e.g., hemiarthrodesis for congenital hemivertebra). The smallest child in the thoracoscopic group (age: 1 year and 8 months, weight: 10 kg) had congenital scoliosis in which a hemiepiphysiodesis was performed over three levels. The benefits of thoracoscopy, compared to thoracotomy, for such an exposure are limited and likely not worth the effort. Although there were similar outcomes in the small and large children thoracoscopic groups, the authors believe that patient size under 20 kg should remain a relative contraindication to thoracoscopic surgery, especially during a surgeon’s learning curve.
Despite the decreased working space within the chest and difficulties of selective intubation, anterior thoracoscopic surgery for spinal release and fusion can be performed safely in small children. Intraoperative challenges associated with increased blood loss (mL/kg), as well as increased chest tube output (mL/kg), longer ICU stay, and the need for specialized intubation methods should be anticipated.
- Thoracoscopic anterior spinal surgery can be safely and effectively performed in children weighing less than 30 kg.
- In these small children, greater blood loss per kg body weight should be anticipated.
- Specialized methods of intubation for single lung ventilation may be required.
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Keywords:© 2002 Lippincott Williams & Wilkins, Inc.
thoracoscopy; scoliosis; spine deformity; endoscopy; pediatric]Spine 2002;27:2368–2373