Postoperative Pulmonary Complications after Craniovertebral Junction Anomaly Surgery: A Prospective Observational Study

Abstract

Background

Although respiratory dysfunction is commonly seen in patients with craniovertebral junction (CVJ) anomalies, pulmonary complications following CVJ surgery have not been extensively studied. We studied the incidence of postoperative pulmonary complications (PPCs) after CVJ surgeries and determined the risk factors. We also evaluated the association between the preoperative pulmonary reserve and PPC.

Methods

This prospective observational study was performed in 41 patients aged 12 to 65 years undergoing surgery for CVJ anomalies. The preoperative pulmonary reserve was assessed with bedside tests (breath holding time [BHT], single breadth count [SBC], and chest expansion) and using a spirometer (forced vital capacity [FVC], forced expiratory volume [FEV₁], FEV1/FVC, peak expiratory flow rate). Postoperatively, the incidence of PPC was assessed, and the duration of mechanical ventilation/tracheostomy was noted. Spirometry was repeated after 3 months.

Results

The incidence of PPCs was 26.8%, and respiratory support requirement was commonly seen (54.5%). Bedside PFTs, including BHT, SBC, and chest expansion (p = 0.045, 0.001, and 0.012, respectively), along with blood loss (p = 0.013), had a significant association with PPCs. Multivariate analysis revealed a significant association of PPC with blood loss. There was a decline in FEV1 in the postoperative period, followed by improvement after 3 months.

Conclusion

The incidence of PPC following CVJ surgery is relatively high (26.8%), and intraoperative blood loss is an independent risk factor. Bedside PFTs like chest expansion may be superior to spirometry tests in predicting the risk of PPC.

Keywords

craniovertebral junction anomaly - pulmonary function tests - spirometry - bedside pulmonary function test - pulmonary complications

Introduction

Craniovertebral junction (CVJ) anomalies are disorders affecting the upper cervical spine enclosing the junction of the brain and spinal cord. The bony defects causing compression of neural tissue in these anomalies include occipitalization of the first cervical vertebra, basilar invagination, and congenital atlantoaxial joint dislocation (AAD).[1] This compression may lead to the weakening of the diaphragm and other respiratory muscles, reduction in upper airway muscles tone causing central sleep apnea, poor coughing ability increasing basal atelectasis, and absence of gag and cough reflexes increasing the chances of aspiration.[2] The surgical trauma may reduce pulmonary functions significantly due to the neural handling or the influence of anesthetic agents.[3] [4]

Previously, the incidence of postoperative pulmonary complications (PPCs) is reported to be from 15 to 25% post-CVJ anomaly surgery.[4] [5] Various factors contributing to PPCs include poor American Society of Anaesthesiologists (ASA) physical status, preoperative lower cranial nerves palsy or respiratory involvement, prolonged duration of surgery, and intraoperative blood transfusion.[6]

However, the literature regarding the evaluation of preoperative pulmonary reserve and its association with postoperative complications is lacking. Hence, we conducted this study with the primary objective of determining the incidence of PPCs after surgery of CVJ anomalies. The secondary objectives included determining the risk factors associated with PPCs and evaluating the association between the preoperative pulmonary reserve and PPC.

Materials and Methods

This prospective observational study was conducted from January 2018 to December 2019 after getting approval from Institutional Ethics Committee (INT/IEC/2018/000623, 03/05/2018) and obtaining written and informed consent from the patients or the patient's legal heir. The study conformed to the standards of the Declaration of Helsinki.

After that the study was halted due to the pandemic, which led to the change of institutional policies for PFTs. All the consecutive patients aged 12 to 65 years with CVJ anomalies posted for surgery (posterior decompression and plating from C0 to C2 by posterior approach) were screened for eligibility. Exclusion criteria included patients undergoing combined posterior and anterior approach, requiring preoperative intubation and ventilator support, patients with severe cardiac and pulmonary disease, morbid obesity (body mass index >40 kg/m²), obstructive sleep apnea, clinically significant scoliosis, severe neurological disability (pre-existing hemiplegia or quadriplegia), patient refusal/inability to consent, and association of other neuromuscular disorder.

The patient's epidemiological and anthropometric data were recorded. Broadly two main categories of pulmonary function tests (PFTs) evaluate the pulmonary reserve, preoperatively. One is laboratory-based spirometry, laboratory PFTs (forced vital capacity [FVC], forced expiratory volume [FEV₁], FEV1/FVC ratio, peak expiratory flow rate [PEFR]), which is the gold standard. We used EasyOne Spirometer (ndd medical technology, Switzerland). A decline in PFT was indicated by percentage (%) predicted FEV1: >80%, mild; 50 to 79%, moderate; 30 to 49%, severe; and <30%, very severe.[7] [8] The other is bedside PFTs (chest expansion, breath holding time >20 second [BHT], single breath count >20 [SBC]).[9] [10] [11]

The neurological status was assessed by the Japanese Orthopaedic Association Score (JOAS) preoperatively.[12]

Intraoperatively anesthesia was managed as per the institutional protocol. All the cases were done under general anesthesia using balanced anesthesia technique (propofol, fentanyl, and vecuronium). All the patients were intubated using video-laryngoscope or fiberoptic-assisted video-laryngoscopy. The extubation was planned on table at the end of surgery in patients where surgical duration was less than 6 hours with minimal handling of neural tissues and lesser blood loss. Before extubation, adequate muscle power, full awakening, adequate ventilatory efforts, and intact airway reflexes were ensured. Intraoperative monitoring included invasive as well as non-invasive blood pressure, electrocardiography (ECG), peripheral oxygen saturation (SpO₂), end-tidal carbon dioxide (EtCO₂), temperature, urine output, and blood loss. We recorded intraoperative data, including the duration of surgery, the total intravenous fluid used (crystalloids, colloids, blood, and blood products), and the ratio of partial pressure of oxygen in arterial and inspired oxygen (P/F) at the beginning and end of the surgery. Any intraoperative events like hypotension, bradycardia, and nerve injuries were noted. Postoperatively, the duration of intubation or mechanical ventilation and the day of extubation or tracheostomy after surgery were recorded. Patients were assessed for occurrence of PPC every day after surgery till discharge. PPCs were defined as the presence of any one or a combination of the following signs: fever with productive cough with sputum, pleural effusion, breathing difficulty, the need of respiratory support for more than 24 hours, crepitations, pneumonitis, presence of abnormal chest radiograph, and need of tracheostomy.

Laboratory PFTs were repeated at discharge and after 3 months, postoperatively, and changes were compared with the baseline (preoperative) PFTs. As FEV1 is most affected in patients with CVJ anomalies, we used this parameter to look for the trends of PFTs.

The statistical analysis was performed using Statistical Package for Social Sciences (IBM SPSS Inc., Chicago, IL, version 22). Bivariable analysis was done to detect significant risk factors for developing PPCs. Student's t-test was used to analyze continuous variables such as age, duration of surgery and anesthesia, hospital and ICU stay, blood loss, and fluid infusion. Chi-square or Fisher's exact test was done for categorical variables such as need for mechanical ventilation and respiratory involvement. Factors found significant in the bivariable analysis were entered into a logistic regression model for multivariate analysis. This was done to detect the relative contribution of the factors shown to be significant by bivariate analysis. A P-value of <0.05 was considered significant.

Results

A total of 41 patients, 26 (63%) males and 15 (37%) females with a mean age of 35.5 ± 16.8 years (range 12–64 years), were recruited in the study. Five patients were excluded; one presented with quadriparesis, three patients could not perform PFTs, and one patient developed respiratory distress prior to surgery. The incidence of PPCs was 26.8% (11/41). The demography, baseline characteristics, and association of various perioperative parameters are mentioned in [Table 1].

Table 1 Demographic profile, baseline characteristics, and other perioperative factors

Parameter	PPCs present 11 (26.8%)	PPCs absent 30 (73.2%)	P-values
Age (years)	34.45 ± 20.4	35.93 ± 15.6	0.806
Gender (male/female), n (% within PPCs)	5 (54.5%)/6 (45.5%)	21 (70%)/9 (45.5%)	0.141
ASA, n (% within PPCs)
I	8 (72.7%)	26 (86.7%)	0.268
II	1 (20%)	4 (13.3%)
III	2 (8%)	0
BMI (kg/m2)	20.10 ± 3.7	22.59 ± 3.4	0.530
JOAS—Preoperative	15.55 ± 2.2	15.3 ± 1.8	0.720
Laboratory PFTs (% predictive value)
FVC	70.17 ± 20.6	75.15 ± 16.5	0.099
FEV1	67.12 ± 18.7	73.59 ± 18.2	0.186
FEV1/FVC	70.98 ± 11.4	77.96 ± 9.5	0.064
FEF 25–75%	44.01 ± 10.9	63.46 ± 19.1	0.064
PEFR	72.13 ± 37.2	67.39 ± 21.4	0.748
Bedside PFTs
BHT (Sec)	24.40 ± 3.5	26.59 ± 5.9	0.045[*]
SBC (number)	24.00 ± 3.7	28.11 ± 3.5	0.001[*]
Chest expansion (cm)	5.14 ± 1.3	6.44 ± 0.8	0.012[*]
P/F ratio at the start of surgery	418.91 ± 21.8	418.80 ± 60.08	0.993
Respiratory rate (per minute)	14.64 ± 1.9	14.93 ± 1.9	0.659
Intraoperative parameters
Duration of anesthesia (min)	244.55 ± 37.0	247.17 ± 38.1	0.844
Blood loss (mL)	804.55 ± 446.3	396.67 ± 133.9	0.013[*]
Crystalloids (L)	4.70 ± 1.4	4.77 ± 1.17	0.895
Colloids (L)	1.00 ± 0.0	0.00	0.999
Blood transfusion (mL)	360.0 ± 40.8	343.5 ± 52.4	0.300
Urine output (mL)	636.36 ± 313.9	646.67 ± 157.0	0.919
P/F ratio at end of surgery	468.00 ± 43.0	468.40 ± 57.0	0.980
Extubated on table, n (%)	2 (18.2%)	11 (36.7%)	0.231

Abbreviations: BHT, breath holding time; BMI, body mass index; FEF 25–75%, forced expiratory flow at 25–75% of expiration; FEV1, forced expiratory volume at 1 second; FVC, vital capacity; JOAS, Japanese Orthopaedic Association Score; P/F ratio, ratio between partial pressure of oxygen in blood to fraction of inspired oxygen; PEFR, peek expiratory flow rate; PFTs, pulmonary function tests; PPCs, postoperative pulmonary complications; SBC, single breath count.

Notes: Data are presented as mean, number (%), and standard deviation. P-value <0.05 is statistically significant.

^* means statistically significant.

Out of 41 patients, 13 were extubated as shown in [Table 1]. The various pulmonary complications observed after the surgery are enumerated in [Table 2]. Seven patients (63.6%) developed signs of pneumonitis followed by patients requiring prolonged mechanical ventilation (six, 54.5%), >24 hours postoperatively. [Table 3] presents the trend of PFTs at various time points. There was significant decline in all the parameters postoperatively, which recovered at 3 months.

Table 2 Distribution of various pulmonary pathologies

Pulmonary complications	Number of patients (%)
Purulent secretions, fever, cough	7 (63.6%)
Tracheostomy	5 (45.4%)
Need for respiratory support (>24 hours)	6 (54.5%)
Crepitations	5 (45.4%)
Presence of abnormal chest radiograph	4 (36.4%)
Breathing difficulty	2 (18.2%)

Note: Data are presented as number (%). P-value <0.05 is statistically significant.

Table 3 Trend of PFTs at various time points

Parameters	Baseline	At discharge	At 3 months	P-value
FVC
PPCs + , 11 (26.8%)	70.17 ± 20.6	69.08 ± 20.0	70.08 ± 21.1	0.006[a]
PPCs − , 30 (73.2%)	75.15 ± 16.5	71.63 ± 17.2	74.78 ± 17.0	<0.001[a]
FEV1
PPCs+	67.12 ± 18.7	65.98 ± 19.6	69.70 ± 19.3	0.887
PPCs−	73.59 ± 18.2	69.99 ± 18.6	73.36 ± 18.8	0.003[a]
FEV1/FVC
PPCs+	70.98 ± 11.4	70.48 ± 10.5	71.38 ± 13.1	0.258
PPCs−	77.96 ± 09.5	74.36 ± 10.7	78.72 ± 09.4	0.010[a]
FEF 25–75%
PPCs+	44.10 ± 10.9	42.05 ± 11.0	42.88 ± 10.0	0.391
PPCs−	63.46 ± 19.1	61.34 ± 18.5	64.03 ± 18.1	0.025[a]
PEFR
PPCs+	72.12 ± 37.2	69.18 ± 37.4	74.70 ± 35.9	<0.001[a]
PPCs−	67.39 ± 21.4	62.11 ± 16.7	68.23 ± 20.3	0.621
BHT (Sec)
PPCs+	24.40 ± 3.5	22.80 ± 4.658	25.20 ± 5.167	0.202
PPCs−	26.59 ± 5.9	25.19 ± 3.259	27.04 ± 3.777	0.202
SBC
PPCs+	24.00 ± 3.7	21.00 ± 3.7	24.80 ± 5.5	0.014[a]
PPCs−	28.11 ± 3.5	26.00 ± 4.2	28.22 ± 4.2	0.014[a]
Chest expansion
PPCs+	5.14 ± 1.3	4.71 ± 1.3	5.29 ± 1.1	<0.001[a]
PPCs−	6.44 ± 0.8	6.26 ± 0.9	6.26 ± 0.9	<0.001[a]

Abbreviations: BHT, breath holding time; FEF 25–75%, forced expiratory flow at 25–75% of expiration; FEV1, forced expiratory volume at 1 second; FVC, vital capacity; PEFR, peek expiratory flow rate; PFTs, pulmonary function tests; PPCs − , postoperative pulmonary complications absent; PPCs + , postoperative pulmonary complications present; SBC, single breath count.

Notes: Data are presented as mean ± SD.

^a Indicates P-value <0.05.

Out of all the parameters, bedside PFTs and blood loss were found to have a significant association with PPCs. On multivariate analysis only blood loss was found to be statistically significant ([Table 4]). Although the chest expansion showed a higher odds ratio, it was insignificant due to a very wide confidence interval.

Table 4 Odds ratio of various risk factors

Parameter	P-value	Odds ratio (95% CI)
Blood loss	0.010	1.012 (1.003–1.021)[a]
BHT	0.337	1.230 (0.806–1.877)
SBC	0.843	1.047 (0.665–1.649)
Chest expansion	0.117	8.049 (0.592–109.36)

Abbreviations: BHT, breath holding time; CI, confidence interval; SBC, single breath count.

^a P-value <0.05.

In the current study, we observed that the incidence of PPCs is 26.8%. The multivariable analysis extracted one parameter, blood loss, on univariable analysis (chest expansion, SBC, BHT, and blood loss). PFT values declined after surgery while reached above baseline at 3 months follow-up.

Discussion

The current study aimed to determine the incidence and risk factors of PPCs, and we observed PPCs in 26.8% of cases. Crockard et al[13] reported a 25% incidence of PPCs following cervical spine surgery, which is quite close to our findings. Patients with CVJ anomaly are more likely to develop postoperative respiratory complications, which may be exacerbated by general anesthesia and surgical intervention.

In the current study, the commonest complication was pneumonitis (63.6%). Most of these patients required the support of mechanical ventilation. The need for prolonged ventilatory support was mainly due to decreased respiratory muscle strength. Reddy et al[14] has advised monitoring respiratory functions and physiotherapy for several days after definitive surgery to prevent PPCs in these patients. Among the patients who required tracheostomy in our study, two patients had poor gag and cough reflexes, out of which one patient suffered from aspiration pneumonitis and the rest were tracheostomized due to failure to wean.

The respiratory muscle weakness in patients with AAD leads to a restrictive type of muscle weakness. Rosomoff[15] observed that in patients with CVJ anomalies, the respiratory compromise was occult in most of the cases, which required laboratory testing. The author also observed decreased respiratory parameters, including vital capacity, peak breathing ability, and lung compliance. In the present study, we found that the mean value of preoperative FVC, FEV1, and FEF was 25 to 75%, in which PPCs were present in 65, 64, and 50% of the predicted value, respectively, while patients who did not develop PPCs had slightly higher values of 75, 72, and 63%, respectively.

Theoretically, the patients with CVJ anomalies should have a restrictive type of respiratory pattern on spirometry due to decreased muscle power leading to a limitation in chest movements.[16] However, in our study, the preoperative PFTs showed a mixed pattern, both obstructive and restrictive types. The explanation for this finding may be due to the inability to perform the test properly due to the pain or neck stabilization devices preoperatively. In the current study, we observed that approximately 40% of patients who developed PPCs fell under the severe grade as per the American Thoracic Society's severity grading.[17] Pulmonary function tests are highly subjective, and their findings vary with the effort and power of the patient. Hence, we cannot rely on PFTs alone to predict the occurrence of PPCs.

PFT parameter values decreased from the baseline in the early postoperative period (at the time of discharge). A prospective study by Rath et al[3] reported that PFTs significantly deteriorated in the early postoperative period. They gave the following explanation for their results. There may be residual edema in the spinal cord due to surgical manipulations in the immediate postoperative period. Patients may have difficulty performing tests due to pain or residual atelectasis following general anesthesia. At 3 months follow-up, these values reached the preoperative stage with slight improvement, suggesting that surgery had no adverse effect on respiratory reserve at 3 months follow-up.

In the current study, we also conducted bedside preoperative PFTs in all the patients, including BHT, SBC, and chest expansion. The bedside PFTs are non-invasive, simple tests which can predict cardio-pulmonary reserve. The incidence of PPCs was significantly high in patients with deranged bedside PFTs. The odds ratio of BHT, SBC, and chest expansion were 1.23, 1.05, and 8.05, respectively. Among these parameters, reduced chest expansion showed higher odds for occurrence of PPCs. As the small sample size may lead to wider confidence interval, larger study is required in the future to prove the association of chest expansion with PPCs.

The patients with CVJ anomalies have generalized muscle weakness, including respiratory muscles, which are involved in chest movements. The reduced chest expansion indicates more severe muscle weakness and greater compression of the spinal cord. Such patients are more prone to atelectasis and aspiration due to reduced coughing ability, which might have contributed to the higher incidence of PPCs in patients with reduced chest expansion. However, due to the small sample size, these values may not accurately reflect the true odds ratio.

We found that the incidence of PPCs was significantly higher in patients with more blood loss, but there was no difference in crystalloids infusion and blood transfusion in patients with or without PPCs. The patients who received hydroxyethyl starch solution along with crystalloid and blood also did not develop PPCs. Excessive crystalloid and blood transfusions are known to be associated with PPCs. In our study, blood transfusion was not found to be related to PPCs as none of the patients received massive transfusion. The blood loss was significantly higher in PPC groups (804 mL) compared with without PPC group (396 mL) PPCs. Blood transfusion causes immunomodulation that may result in more chest infections in patients receiving a blood transfusion.[18] [19] Blood loss is associated with reduced levels of hemoglobin leading to lethargy and reduced coughing ability and may potentiate PPCs.[20] However, although the analysis shows statistically significant values, the odds ratio was slightly higher than 1, i.e., 1.012 (1.003–1.021), indicating clinical irrelevance ([Table 4]).

This study highlights the role of bedside PFTs in patients undergoing CVJ surgeries. Many a times laboratory PFTs may not be available or possible to do due to traction in place; then bedside PFTs is the reliable alternative. Patients showing derangements in these parameters should undergo vigorous chest physiotherapy and incentive spirometery started in preoperative period to minimize the risk of PPCs.

The major limitation of the current study is the limited sample size. However, this study paves the path for future investigation and gives some insight that bedside PFTs, which are non-expensive tools, are superior to more resource-consuming PFTs. Also, it avoids aerosol generation. We can direct future studies to prove these hypotheses. Another limitation is that we did not perform computed tomography of the chest to quantify the severity of chest involvement to avoid radiation exposure. Modalities like ultrasound lung and diaphragmatic excursion may be included in future, which can detect even minor lung involvement.

Conclusion

We conclude that the incidence of PPCs following the cranio-vertebral junction anomaly surgery was 26.8%. Preoperative pulmonary function tests using spirometry could not predict the development of PPCs as these tests may become unreliable if not performed correctly due to pain or neck stabilization devices. All the bedside PFTs could be performed even in bed-ridden patients and were found to be significantly deranged in patients who developed PPCs, and chest expansion showed the highest odds ratio of 8.04. The intraoperative blood loss was also an independent risk factor for PPCs.

Conflict of Interest

None declared.

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Publication History

Article published online:
28 January 2026