Postoperative Pulmonary Complications in Complex Paediatric and Adult Spine Deformity: A Retrospective Review of Consecutive Patients Treated at SRS GOP Site in Ghana

Background Pulmonary complications are important cause of morbidity and mortality in patients following spinal surgeries. There is paucity of literature on pulmonary complications following complex spine deformity surgery in underserved regions. This study sought to assess the incidence and risk factors of pulmonary complication following complex spine deformity surgery Methods Data of 276 complex spine deformity patients aged 3-25yrs who were consecutively treated at a single site were retrospectively reviewed. Data was analyzed using Stata 14 software. Patients were labelled into two groups: Grp 1: patients with pulmonary complications(N=17) vs Grp 2: patients with no pulmonary complications (N=259). Comparative analysis for risk factors included independent t-test and chi square test for independence. Multivariate logistic regression analysis was also performed. Results The incidence proportion of pulmonary complication was 17/276 (6.1%) (Grp 1) whiles 259 pts had no pulmonary events (Grp 2). There were 8M/9F for Grp 1 vs 100M/159F Grp 2, p=0.48. BMI was similar in both groups (17.2 vs 18.4km -2 , p=0.15). Average pre-op sagittal cobb (90.6 vs 88.7deg, p=0.87.), coronal cobb (95 vs 88.5deg, p=0.43), Pre-Op FVC (45.3 vs 62.0%, p=0.02), Pre-Op FEV1 (41.9% vs 63.1, p<0.001), Grp 1 vs Grp 2, respectively. EBL, OR time and Surgery Levels were similar in both Grps. Thoracoplasty was performed in 41.18% vs 21.57%, p=0.06, SPO 47.06% vs 42.31%, p=0.04 and VCR 5.88% vs 20.31%, p=0.145, Grp 1 vs Grp 2, respectively. Multivariate logistic regression showed that every unit increase in pre-Op FVC (%) decreases the odds of pulmonary complication by 5% (OR=0.95, 95% CI 0.90 to 0.99, p=0.045). Conclusion The observed 6.1% incidence of pulmonary complications is comparable to reported series. Only pre-Op FVC was an independent predictor of pulmonary complications. The observed case fatality rate (17%) following pulmonary complications highlights the need for thorough preoperative evaluation to identify high risk patients.


Abstract
Background Pulmonary complications are important cause of morbidity and mortality in patients following spinal surgeries.There is paucity of literature on pulmonary complications following complex spine deformity surgery in underserved regions.This study sought to assess the incidence and risk factors of pulmonary complication following complex spine deformity surgery Methods Data of 276 complex spine deformity patients aged 3-25yrs who were consecutively treated at a single site were retrospectively reviewed.Data was analyzed using Stata 14 software.Patients were labelled into two groups: Grp 1: patients with pulmonary complications(N=17) vs Grp 2: patients with no pulmonary complications (N=259).Comparative analysis for risk factors included independent t-test and chi square test for independence.Multivariate logistic regression analysis was also performed.Results The incidence proportion of pulmonary complication was 17/276 (6.1%) (Grp 1) whiles 259 pts had no pulmonary events (Grp 2).There were 8M/9F for Grp 1 vs 100M/159F Grp 2, p=0.48.BMI was similar in both groups (17.2 vs 18.4km -2 , p=0.15).Average pre-op sagittal cobb (90.6 vs 88.7deg, p=0.87.), coronal cobb (95 vs 88.5deg, p=0.43),Pre-Op FVC (45.3 vs 62.0%, p=0.02),Pre-Op FEV1 (41.9% vs 63.1, p<0.001),Grp 1 vs Grp 2, respectively.EBL, OR time and Surgery Levels were similar in both Grps.Thoracoplasty was performed in 41.18% vs 21.57%, p=0.06,SPO 47.06% vs 42.31%, p=0.04 and VCR 5.88% vs 20.31%, p=0.145,Grp 1 vs Grp 2, respectively.Multivariate logistic regression showed that every unit increase in pre-Op FVC (%) decreases the odds of pulmonary complication by 5% (OR=0.95,95% CI 0.90 to 0.99, p=0.045).Conclusion The observed 6.1% incidence of pulmonary complications is comparable to reported series.Only pre-Op FVC was an independent predictor of pulmonary complications.The observed case fatality rate (17%) following pulmonary complications highlights the need for thorough preoperative evaluation to identify high risk patients.Key words: Complex spine deformity; Pulmonary complications; late presentation; Forced Vital Capacity; Halo Gravity Traction; FVC; pediatric deformity; scoliosis; Pulmonary function tests; PFT; complications; Preoperative management.
The concern for pulmonary complications is even greater in developing regions with limited expertise and resources.Patients in these regions typically report to health facilities when spine deformities have signi cantly progressed [13].These severe deformities are associated with poor pulmonary function [14][15][16][17][18]. Impaired pulmonary function increases the risk of post-op pulmonary complications after spine surgery [18].Besides, spine surgery for these patients is characterized by signi cant blood loss, long operative time, and the use of three column osteotomies which further increases the risk for neurologic and non-neurologic complications [1].The presence of comorbidities coupled with major surgical procedures further increases the risk of pulmonary complications [9] The mechanism of pulmonary complication following spinal surgery may be related to direct trauma, embolization of marrow material into the lung including fat, ventilation-association lung injury and transfusion-associated lung injury [19][20][21][22][23]. Post-op pulmonary complications increase the risk of mortality after spine surgery [5,6,7].Aside mortality, post-op pulmonary complications can affect the length of stay and cost of hospitalization [7].Identi cation of risk factors for pulmonary complications would help avert these outcomes.However, there is paucity of literature on pulmonary complications following complex pediatric spine deformity surgery in underserved regions such as West Africa.This study sought to investigate the incidence and risk factors for pulmonary complications following complex pediatric and adult spine deformity surgeries in specialist Orthopaedic Hospital in Ghana, West Africa.

Methods
Data of 276 consecutive complex spine deformity patients aged 3-25yrs who were treated at a single site in Ghana from January, 2015 to December, 2017 were retrospectively reviewed using information from the FOCOS Spine Registry, electronic records and led folders.Institutional Review Board (IRB) approval was obtained from the Noguchi Memorial Institute for Medical Research (NMIMR) prior to initiation of the study (Certi ed Protocol Number: 057/16-17).Research data was initially extracted in excel format and exported into Stata 14 Software for analysis.The primary outcome reviewed was post-op pulmonary complications which was de ned as any pulmonary event following spine deformity surgery including respiratory distress, prolonged intubation of more than 48hrs, re-intubation, pneumonia, Acute respiratory distress syndrome (ARDS), signi cant pneumothorax and tracheostomy.Record review for the primary outcome was restricted to pulmonary complication events that occurred within the rst six (6) weeks after surgery.All deformity etiology types were included in the analysis.Patients were divided into two groups during data analysis: Group 1: patients who developed pulmonary complications and Group 2: patients who did not develop pulmonary complications (Differences between the groups were not known prior to data collection).Comparative analysis was performed between the two groups to identify the risk factors.Multivariate logistic regression analysis was performed to evaluate the strength of the association.

Outcomes of Pulmonary Events
The etiologies of the 17 patients who developed pulmonary complications comprised 7 Idiopathic, 5 congenital, 2 Neuromuscular, 2 Neuro bromatosis and 1 Post TB.There were 3 mortalities (1 congenital, 1 Post TB and 1 Neuro bromatosis) representing a case fatality rate of 17.6%.The details of the outcomes of pulmonary events by type of pulmonary event and deformity etiologies are shown in Table 3 and Table 4, respectively.

Discussion
Pulmonary complications are very critical in perioperative management of patients after complex deformity surgery.Despite the variation in de nition of pulmonary complications, the conditions classi ed as such are generally similar and they include Empyema, Haemothorax, Pleural effusion, Postop hypoxia, Pneumonia, Pneumothorax, Pulmonary embolus, Respiratory arrest, Transfusion-related Acute Lung Injury (TRALI), Transfusion Associated Circulatory Overload (TACO) and pulmonary edema amongst other pulmonary problems [9,19,20,[24][25][26].
The cumulative incidence of post-op pulmonary complication observed in this cohort was 6.16%.This incidence is within the range reported by previous studies [7][8][9][10][11][12].Patil et al. [7] reported a post-op pulmonary complication rate of 8.1% among idiopathic patients <18years (1-17yrs) old and 9.8% in idiopathic patients >18years old (18-84yrs).Imposti et al. [9] also reported a 9% cumulative incidence of a pulmonary complication after spine surgery.Their patients were >18years and comprised degenerative and trauma cases.Moreover, pulmonary complications within 2-year period after spinal surgery were included in their reported cumulative incidence [9].However, the present study included only paediatric and young adult deformity patients aged 3-25years and reported only early pulmonary complications (up to 6weeks post-op).These methodological variations could account for the slight difference observed in the cumulative incidence of post-op pulmonary complications.
However, the degree of pulmonary compromise is not attributable to curve magnitudes alone [17].We observed that pre-op FVC (% predicted) was signi cantly lower in patients who developed pulmonary complications compared to those who had no pulmonary complications.Further analysis with multivariate logistic regression revealed that increasing pre-op FVC was associated with reduced odds of pulmonary complications (OR=0.95,95% CI 0.90 to 0.99, p=0.035).Spine surgery can cause signi cant transient decline in PFT up to 60% of pre-op values with a gradual return to baseline 1-2 months after surgery [27].Therefore, patients with poor baseline PFT may have higher risk for post-op pulmonary complications because they are likely to experience further deterioration in their PFT after spine surgery compared to their counterparts with good baseline PFT.Lao et al. [18] also reported that patients with severe or moderate preoperative pulmonary dysfunction, as measured by the FVC ratio, had a higher incidence of post-op pulmonary complications.Stein et al. [24] also found a higher incidence of pulmonary complications in patients with abnormal PFT results compared to those with normal PFTs.In addition, Kang et al. [25] found that neuromuscular patients with FVC <39.5% have increased risk of postop pulmonary complications following spine surgery.Preoperative long term Halo gravity traction with breathing exercises may help in this regard.
We report a case-fatality rate of 17.6% among patients who developed post-op pulmonary complications.This highlights the likelihood of an adverse outcome when there is a pulmonary complication.Previous studies have also documented signi cant mortality following post-op pulmonary complications [5,6,9,26].Imposti et al. [9] found that mortality rate from pulmonary complications was 3.61 per 1,000 persons per year.Pumberger et al. [26] also assessed the risk factors for in-hospital mortality following lumbar fusion surgery and found that patients who developed post-op pneumonia had 3 times greater risk of mortality whiles those who developed pulmonary embolism had 10 times greater risk of mortality.The case-fatality rate observed in the present series of paediatric and young adult spine deformity patients underscores the need for proactive perioperative measures to reduce pulmonary complications.
The 6.16% incidence of pulmonary complication recorded in this series is commendable for a private facility in low-resource setting such as Ghana.Various perioperative measures have enabled us to achieve such comparable pulmonary complication rates despite the complexities of the spine deformity cases present in this cohort.These included utilization of pre-op Halo Gravity Traction (HGT) [13,[28][29], adequate pre-op nutritional rehabilitation [30], elective overnight ventilation after surgery for patients with poor FVC and early application of tracheostomy at the earliest sign of di culty in weaning off ventilation.
Therefore, we make the following recommendations for surgeons performing complex deformity surgery in low-resource settings: 1. Identi cation of high risk patients with poor pre-op FVC This paper is the largest single site review of post-operative pulmonary complications following complex spine deformity surgery in Africa.However, as a retrospective study, the study has certain limitations.Analysis and ndings were based on only data that could be retrieved.The study reported on early pulmonary complications (up 6weeks post-op) hence it is possible that the complication rate may vary if patients were followed over longer period after surgery.These patients are being followed for long term pulmonary outcomes.

Conclusion
We report a 6.16% cumulative incidence of pulmonary complication in our series which is within the range of other reports.Pre-op FVC was the only signi cant independent risk factor for pulmonary complications.The high case fatality rate observed (17.6%) implies the need for thorough pre-op evaluation to identify high risk patients and the need for proactive perioperative measures to reduce incidence and mortality associated with pulmonary complications.

2 .
Utilization of HGT to reduce curve magnitude and stiffness 3. Pre-op nutritional optimization 4. Elective post-op ventilation and use of prophylactic diuretics for pulmonary edema 5. Application of Tracheotomy at the earliest sign of respiratory distress .Need for ICU coverage Strengths and Limitations Expiratory Volume in one second (FEV1) Post-op: Post-operative Pre-op: Pre-operative EBL: Estimated Blood Loss

Table 1 :
Summary of demographic, clinical and surgical logs by post-op pulmonary of pulmonary complication by 5% (OR=0.95,95%CI 0.90 to 0.99, p=0.045), after controlling for age, curve type, curve etiology, BMI, gender, pre-op sagittal and coronal cobb angles, duration of surgery, EBL, thoracoplasty, SPO, PSO and VCR.(Table2) Predictors of Pulmonary Complications in Multivariate AnalysisOnly Pre-operative FVC was found to be a signi cant independent predictor of pulmonary complication in multivariate analysis.Multivariate logistic regression revealed that every 1% increase in pre-operative FVC decreases the odds

Table 2 :
Multivariate Logistic Regression Estimates of the Risk Factors for Pulmonary Complications

Table 3 :
Outcomes of Pulmonary Complications by type of Pulmonary Event ARDS: Acute respiratory distress syndrome

Table 4 :
Outcomes of Pulmonary Complications by Curve Etiologies