Incidence of radiographic pulmonary abnormalities after posterior spinal fusion surgery for pediatric scoliosis

Abstract

Background and Aims:

Pulmonary complications are the most common non-neurologic complications following surgical correction of scoliosis. These can affect postoperative recovery by increasing the length of stay and/or the need for ventilatory support. The aim of this retrospective study is to determine the incidence of radiographic abnormalities reported in chest radiography after posterior spinal fusion surgery for the treatment of scoliosis in children.

Material and Methods:

A retrospective chart review of all patients who underwent posterior spinal fusion surgery in our center between January 2016 and December 2019 was attempted. Radiographic data including chest and spine radiographs were reviewed on the national integrated medical imaging system using medical record numbers for all patients in the 7 postoperative days.

Results:

Seventy-six (45.5%) of the 167 patients developed radiographic abnormalities in the postoperative period. There was evidence of atelectasis in 50 (29.9%) patients, pleural effusion in 50 (29.9%) patients, pulmonary consolidation in 8 (4.8%) patients, pneumothorax in 6 (3.6%) patients, subcutaneous emphysema in 5 (3%) patients, and rib fracture in 1 (0.6%) patient. Four (2.4%) patients were noted to have an intercostal tube inserted postoperatively, three for treating pneumothorax, and one for pleural effusion.

Conclusion:

A large number of radiographic pulmonary abnormalities were encountered in children following surgical treatment of pediatric scoliosis. Although not all radiographic findings may be clinically significant, early recognition may guide clinical management. The incidence of air leak (pneumothorax, subcutaneous emphysema) was significant and could influence local protocol formulation with regards to obtaining immediate postoperative chest radiograph and intervention if clinically necessary.

Introduction

Pediatric scoliosis is defined as the lateral rotation of the spine with a Cobb angle of more than 10 degrees in children. It has an estimated prevalence of 1.5%–3%.^[1] Idiopathic scoliosis is the most common type accounting for 70% of the cases.^[1] Neuromuscular and congenital scoliosis are the most common causes of secondary scoliosis.^[2] Posterior spinal fusion (PSF) is the most common surgical treatment for the correction of pediatric scoliosis. Surgery is indicated in most patients with a Cobb angle of >50 degrees, and in some patients with a Cobb angle of <50 degrees, to prevent progression of the curvature and the associated reduction in the pulmonary and cardiac function, as well as to improve cosmesis.^[3]

PSF is a major operation that is associated with significant postoperative morbidity and occasional mortality. There is wide variability in the literature regarding the incidence of complications after PSF. Pulmonary complications (PC) are the most common non-neurologic complications with an incidence of 0.7%–18.2%.^[4,5] These include atelectasis, pleural effusion, pneumothorax, pneumonia, and respiratory failure. PC can affect postoperative recovery by increasing the length of stay and/or the need for ventilatory support and it is the primary cause of death in 41.9%–46.2% of mortality cases.^[6] Factors contributing to postoperative PC include secondary scoliosis, preoperative pulmonary comorbidities, long operation time, and repeat surgery.^[7,8]

Radiographic imaging of the thorax in the operating room immediately after PSF is not routine practice in our institution, with the decision for early chest radiography left to the discretion of the anesthesiologists. Confirmation of the correct positioning of intraoperatively inserted hardware, such as central venous catheters, is usually performed via intraoperative surgical screening radiography. The decision to not perform an immediate postoperative chest radiograph may lead to some missed chest pathology that could benefit from early intervention, such as pneumothorax.

The aim of our study is to determine the incidence of radiographic abnormalities reported in chest radiography after PSF for the treatment of scoliosis in children. This will help in formulating local policy regarding the need for routine immediate postoperative chest radiography following PSF.

Material and Methods

Following approval from our local ethics committee, a retrospective chart review of all patients who underwent posterior spinal fusion surgery for correction of pediatric scoliosis at our institution between January 2016 and December 2019 was undertaken. The patient’s cohort was identified from the operation theatre register database using a specified procedural terminology code. The information obtained from the register included age, gender, and ASA classification. Radiographic data including chest and spine radiographs were reviewed on the national integrated medical imaging system (NIMIS) using medical record numbers for all patients. Radiographic chest imaging from the immediate preoperative period to 7 days postoperatively was reviewed.

To ensure consistency of the radiographic findings, only the original consultant radiologist reports were used to collect data regarding the radiographic abnormalities. Exclusion criteria included patients who had a repeat surgery, as this cohort may have a higher incidence of complications, and patients who had no postoperative radiographic data.

The main outcome measure was the presence of abnormal radiographic findings as reported by the consultant radiologist in chest radiographs postoperatively.

Results

A total of 259 patients were identified as having thoracolumbar scoliosis and who underwent PSF at our institution during the study period. According to our inclusion and exclusion criteria, 167 patients were included in the study [Figure 1]. Of these, 129 (77.2%) were female and 38 (22.8%) were male patients. The median age was 13 ± 2.33 years. There were nineteen (11.4%) patients with American Society of Anaesthesiology (ASA) grade I, 89 (53.3%) patients with ASA II, and 59 (35.3%) patients with ASA grade III [Table 1].

Figure 1.

Patient flow chart

Table 1.

Preoperative patient characteristics

	Normal chest Radiographs (n)	Abnormal chest radiographs (n)
Age	13±2.27	13±2.3
Sex	Female: 71	Female: 58
	Male: 20	Male: 18
ASA I	9	10
ASA II	51	38
ASA III	31	28

An immediate routine postoperative chest radiograph was obtained in 108 (64.7%) patients, whereas the remainder of the patients had chest radiographs later during their postoperative stay if clinically indicated. The indications for ordering a delayed chest radiograph were episodes of temperature, cough, desaturation events, or persistent chest pain.

There were 120 abnormalities reported among 76 (45.5%) patients. There was evidence of atelectasis in 50 (29.9%) patients, pleural effusions in 50 (29.9% of the total study cohort) patients, pulmonary consolidations in 8 (4.8%) patients, pneumothorax in 6 (3.6%) patients, subcutaneous emphysema in 5 (2.9%) patients, and rib fracture in 1 (0.6%) patient [Table 2]. Ninety-one (54.5%) patients did not develop any pulmonary abnormality in the postoperative chest radiographs. Central venous catheter malposition was reported in four (2.4%) patients. Four (2.4%) patients were noted to have an intercostal tube inserted postoperatively, three for treating pneumothorax and one for draining pleural effusion.

Table 2.

Number and percentage (of the total number of the study cohort) of radiographic abnormalities

Abnormal finding	Patients (n)	Percentage
Atelectasis	50	29.9
Left lower lobe atelectasis	40	23.9
Other atelectasis	10	6.0
Pleural effusions	50	29.9
Bilateral pleural effusion	20	11.9
Right pleural effusion	16	9.6
Left pleural effusion	14	8.4
Pulmonary consolidations	8	4.8
Pneumothorax:	6	3.6
Bilateral pneumothorax	2	1.2
Right pneumothorax	2	1.2
Left pneumothorax	2	1.2
Subcutaneous emphysema	5	2.9
Rib fracture	1	0.6

Of the seventy-six patients who had abnormal chest radiographs, 23 (30.3%) patients were diagnosed on the immediate postoperative chest radiographs, seven (9.2%) patients on the first postoperative day, eight (10.5%) patients on the second day, 16 (21.1%) patients on the third day, and 22 (28.9%) patients after the third day.

The overall incidence of air leaks (pneumothorax and subcutaneous emphysema) in our cohort was 6.5%. There was evidence of pneumothorax in six (3.6%) patients, five were diagnosed on the immediate postoperative chest radiograph, and one patient was diagnosed with right-sided tension pneumothorax on the third postoperative day. Subcutaneous emphysema was present in five (2.9%) patients; one of these patients had a concomitant bilateral pneumothorax as well.

Discussion

Pulmonary complications occur frequently postoperatively and increase morbidity and mortality following noncardiac surgery.^[9,10] Postoperative pulmonary complications are usually related to postoperative changes in lung volumes as a result of changes in chest wall mechanics and respiratory muscles dysfunction.^[11] PC are the most common non-neurological complications following scoliosis correction surgery and have a negative impact on outcomes.^[5,6]

Risk factors for PC specific to scoliosis surgery include patient demographics, preoperative comorbidities, the etiology and degree of scoliosis, the surgical approach, and its invasiveness.^[12,13]

There is a wide variation in the reported incidence of PC following pediatric scoliosis surgery which might be related to the method of reporting the complications, heterogenous primary outcomes, or the patient cohort selected. The incidence tends to be low in studies where complications are reported by surgeons rather than those studies which reviewed patients’ charts.^[1,6,14]

Reames et al.^[1] reviewed 19,360 cases of pediatric scoliosis from the Scoliosis Research Society Morbidity and Mortality Database and found that PC occurred in 1% of the patients. The authors note that this low incidence might be due to a higher threshold for reporting pulmonary complications and a lack of methods to determine the accuracy and completeness of data submission. Conversely, Ramos et al.^[12] analyzed the complication rate of 36,335 patients following adolescent idiopathic scoliosis surgery using hospitalization data from the USA nationwide inpatient sample database and found that PC were the most common complication with an incidence of 5.5%. They found that preoperative comorbidities and anterior, or combined anterior/posterior surgical approach, increased the risk of complications.^[12] Patil et al.^[6] identified 51,911 patients who had undergone spinal fusion surgery, and they found that the incidence of PC after surgical correction of idiopathic scoliosis in children was 8.1%.

Carreon et al.^[5] reviewed 702 patients who had undergone corrective surgery for adolescent idiopathic scoliosis and reported postoperative pulmonary complications rate of 1.4% and found no correlation between preoperative respiratory disease and the development of postoperative PC. Many studies have found that the incidence of PC in secondary scoliosis is higher than in the idiopathic form.^[15] Yin et al.^[13] reported that the incidence of pulmonary complications following PSF in congenital scoliosis was 14.9%. Mohamad et al.^[16] retrospectively reviewed 175 patients who underwent surgical correction for neuromuscular scoliosis and found that 19.4% of the patients developed postoperative PC.

Our study has demonstrated a high incidence (45.5%) of abnormal chest radiographs after PSF surgery. This finding is similar to that of Jules-Elysee et al.,^[17] who reported abnormal radiographic findings in 64% of the patients following anterior-posterior spinal fusion.

The incidence of radiographic abnormalities in our study is higher than the incidence of clinical pulmonary complications in the literature as many of these abnormalities may go unnoticed if they caused no or minimal clinical manifestations. However, early identification of these abnormalities may alter clinical management before a clinical deterioration occurs. This is demonstrated in the Jules-Elysee et al.^[17] the study, where patients with abnormal chest radiographs had 3 days longer postoperative length of stay in the hospital compared to patients with normal radiographs.

Of all possible postoperative pulmonary complications, pneumothorax may result in acute clinical deterioration requiring immediate intervention. The overall incidence of pneumothorax in our cohort was 3.6% (the overall incidence of air leak, including subcutaneous emphysema, 6.6%). The majority of pneumothoraxes were diagnosed on the immediate postoperative chest radiograph with 50% of them requiring intercostal tube drain.

Rajmani et al.^[18] looked at the incidence of early pulmonary complications requiring chest tube insertion following spinal fusion surgery for pediatric scoliosis. They found that 1.33% of all children who underwent surgical correction of scoliosis required chest tube insertion, mainly for the drainage of pleural effusion.^[18] The overall incidence of intercostal tube insertion in our cohort was 2.4%, and the main indication was the drainage of postoperative pneumothorax.

Pleural effusion and atelectasis were the most common radiographic abnormalities in our cohort. Pleural effusion can be related to fluid overload from the large volume of crystalloid usually administrated intraoperatively to maintain the circulating volume. Other causes can include diaphragmatic manipulation, prolonged duration of surgery in the prone position, and cardiac failure.^[17,19] Atelectasis can be induced by prolonged surgical time in the prone position, which induces alveolar fluid shift and mucus plug, and postoperative reduction in lung volumes which tends to occur after general anesthesia. Splinting due to incisional pain can also be a contributing factor.^[16,20]

The present study has some limitations. It is a single center, retrospective study, and it lacks preoperative patient clinical details differentiating the etiology of scoliosis, Cobb angle, and the clinical postoperative course and its relation to the postoperative complications. This is due to the authors reviewing patient radiographic data only, rather than their full clinical charts. However, we have demonstrated a high incidence of radiographic abnormalities in children following PSF for scoliosis. Although not all abnormalities may be clinically significant, early recognition may inform ongoing clinical management. The incidence of air leak is significant enough for us to consider reassessment of our policy for immediate postoperative chest radiograph in order to intervene with chest drains should this be clinically necessary. Also, our data may give additional advice for the perioperative planning of scoliosis surgery helping potentially to reduce the incidence of postoperative pulmonary complications.

In conclusion, there was a high incidence of radiographic pulmonary abnormalities in children following PSF surgery. The incidence of air leak (pneumothorax, subcutaneous emphysema) was significant and it could influence local protocol with regards to obtaining immediate postoperative chest radiograph and intervention if clinically necessary.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.