Inferior pulmonary ligament dissection after thoracoscopic bullectomy for primary pneumothorax prevents recurrence

Introduction

Primary spontaneous pneumothorax (PSP) is a common disease entity affecting adolescents and young adults, and it is most notorious for its high recurrence rate. Young age, thin patients with lower body mass index (BMI) and the presence of blebs or bullae on high-resolution computed tomography (CT) scans after an initial episode are significantly correlated to higher ipsilateral recurrence of PSP (1-5).

Wedge bullectomy performed using video-assisted thoracoscopic surgery (VATS) is deemed effective for reducing recurrence and postoperative pain in patients with PSP (6-9). The procedure aims are to resect any visible bullae or blebs, with additional means including pleurodesis or pleurectomy to obliterate the pleural space in case of air leak site from tiny invisible pores on visceral pleura surface, or subsequent bleb regrowth. We previously reported that prolonged suboptimal lung expansion to the apex of the pleural cavity, with persistent apex-to-cupola (ATC) distance measurement >1 cm on chest radiograph over postoperative day (POD) 3, can compromise the pleurosymphysis effect and increase the risk of postoperative PSP recurrence (10). This finding drove us to seek for ways to refine postoperative lung expansion to maximize the pleural symphysis effect. Inferior pulmonary ligament dissection (IPLD) has been arguably utilized for postoperative lung expansion enhancement, particularly in upper lobectomies to reduce effusion and drainage time (11,12). In this study, we evaluate whether IPLD during VATS bullectomy plus pleurodesis could further promote lung expansion and decrease postoperative PSP recurrence. We present this article in accordance with the STROBE reporting checklist (available at https://jtd.amegroups.com/article/view/10.21037/jtd-2025-1022/rc).

Methods

Study design

In this retrospective matched cohort study, we included PSP patients who underwent VATS procedures at the Ditmanson Medical Foundation Chia-Yi Christian Hospital. The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The study was reviewed and approved by the Institutional Review Board of Ditmanson Medical Foundation Chia-Yi Christian Hospital (IRB approval number: IRB2020004). Informed consent was waived due to the retrospective design of the study.

A total of 180 patients with PSP involving 198 surgeries, including 18 sequential or simultaneous bilateral surgeries, were recorded from September 2009 to December 2016. Our patient inclusion criteria included (I) being <30 years old, (II) having no known underlying lung disease, (III) having serial perioperative chest X-rays, and (IV) having postoperative follow-up data of >24 months. Exclusion criteria were as followed, (I) repeated operations, (II) having known underlying disease, (III) having additional postoperative bedside chemical pleurodesis via chest tube, (IV) postoperative follow-up <24 months.

Procedure

The operations were conducted using three-port VATS approach. Intraoperatively, after careful inspection of the whole lung, identified bullae or blebs would be resected using the stapling method routinely with endoscopic staplers (Endo GIA™ ultra universal stapler by Medtronic™); further, any visible active air leak sites from lung parenchyma would be suture-repaired or stapled. If no obvious blebs or emphysematous bullae were found, wedge resection at the apex of the upper lobes would be still performed for being statistically the most common lesion sites. No tissue sealant was applied to reinforce the resection lines in our series, for being not yet prevalent during the study period. Intraoperative mechanical pleurodesis was performed using pleura scrubbing to cover at least upper half of the parietal pleura. IPLD was performed with the ligament divided using electrocautery, starting from its lowest tip above the diaphragm to the lower border of the inferior pulmonary vein. At the end of the operation, the wounds were closured with one 20 Fr. chest tube for drainage. The chest drainage would be removed after air leak stopped and lung expansion observed on chest radiograph. All the operations were performed by two separate surgeons with same operation fashion with same surgical instruments across the whole study period.

Data collection

Clinical parameters, including age, sex, patient body mass index (BMI), history of smoking, lung collapse severity measurement with the Light index, surgical indications, and operative findings including bullae or blebs resection involving single (mostly apex of upper lobes) or multiple lobes (resection involving more than upper lobes), were recorded. Surgical indications included failure of conservative treatment including oxygen supply or persistent air leak after chest drainage, and recurrence of pneumothorax. Imaging data included perioperative serial chest radiographs and preoperative chest CT scan, if available. Postoperative course details, including chest tube suction, duration of chest drainage, hospital stay, and complications including prolonged air leak (defined as air leak >5 days), were recorded. Postoperative residual apical pleural space (RAPS), inversely correlated with the extent of lung expansion, was quantified using the simple ATC distance measurement, adopted by the American College of Chest Physicians (ACCP) in the guidelines for pneumothorax management, and was defined as the vertical distance from the first costovertebral joint to the tip of apical lung on the standard erect posteroanterior chest X-ray. Our rationale to utilize ATC distance to be the inverse surrogate of postoperative lung expansion is: (I) it is easier for clinical practice, being a single linear measurement without calculation, compared to other complex quantitative percentage-based pneumothorax size calculator, such as the “Light index or Collins equation”, more sophisticated yet with under or over-estimation concerns (13); (II) since all the efforts of the operative procedures are meant to increase pleurosymphysis effect, to obliterate particularly the upper part of the pleural residual space, we believe, the ATC distance measurement should be the most direct and appropriate indicator. The ATC distance documentation was categorized into two time-windows because the patients did not receive uniform postoperative chest X-ray schedule in this retrospective study. The two time-windows were the following: the shortest ATC distance during POD 0 and 3 (POD 0–3) and the shortest ATC distance during POD 4 and 14 (POD 4–14). Within 1–3 weeks after discharge, follow-up chest X-rays were also taken in the outpatient department, and the patients were instructed to return to hospital if they experienced fever, or dyspnea. The study endpoint, recurrence, was defined as a subsequent episode of new radiographically-documented ipsilateral pneumothorax after full lung expansion observed during postoperative outpatient follow-up.

Statistical analysis

Continuous data were presented as mean ± standard deviation and were analyzed using a two-tailed Student’s t-test. Categorical data were presented as counts with percentages and were analyzed using the Chi-square or Fisher’s exact test. Considering the effect of confounders, we performed 1:1 propensity score matching between PSP patients who underwent surgery with or without IPLD by applying logistic regression analysis for three variables: patient age, Light index, chest tube suction. All data were analyzed using SPSS 21.0 for Windows (SPSS, Chicago, IL, USA). P<0.05 was considered statistically significant.

Results

Of the 180 consecutive PSP patients who underwent surgeries at Ditmanson Medical Foundation Chia-Yi Christian Hospital, 153 were enrolled (84 and 69 in the IPLD and non-IPLD groups, respectively). After propensity score matching, each group had 61 patients. Detailed patient enrollment flowchart was illustrated in Figure 1.

Figure 1 Patient enrollment flowchart of the total 180 patients with PSP. PSP, primary spontaneous pneumothorax.

Of the 153 patients included [mean age, 20.28±4.19 years old; 141 (94.6%) male], the overall recurrence rate was 4.6% (7/153) with median follow-up of 49.4 months. The mean duration of postoperative chest drainage was 2.20±1.43 days. Risk analysis for postoperative recurrence of overall 153 PSP patients was summarized in Table 1, showing that young age (16.57±2.30 to 20.46±4.18 years old, P=0.02) and larger ATC distance at POD 4–14 (21.00±22.35 to 6.44±9.87 mm, P=0.001) being significant predictors. Moreover, IPLD was performed more in the non-recurrence than recurrence group (57.5% to 0.0%, P=0.003). No significant differences were observed in gender distribution, smoking status, BMI, Light index, laterality, operation time, resection involving single or multiple lobes, chest drainage time, and postoperative hospital stay. There were also no differences regarding prolonged air leak and complications, including fever, retained pleural effusion requiring drainage, or pulmonary edema. Of the 7 patients with ipsilateral recurrence, following treatment included repeated VATS in 5 patients and observation only in 2 patients.

The comparisons between the IPLD and non-IPLD groups were detailed in Table 2. The IPLD patients tended to be older (21.17±4.10 vs. 19.20±4.08 years old, P=0.004) and have a higher Light index (44.21±28.52 to 33.43±29.23, P=0.02), fewer chest tube suction applied (56.0% vs. 73.9%, P=0.03), shorter chest tube indwelling time (1.92±0.90 vs. 2.55±1.84 days, P=0.006), and shorter postoperative hospital stay (2.94±0.95 vs. 3.54±1.59 days, P=0.005). ATC distance were also shorter in the IPLD group at POD 0–3 (7.82±5.89 vs. 10.70±8.58 mm, P=0.02) and POD 4–14 (4.49±8.05 vs. 10.23±13.41 mm, P=0.001). Less recurrence was observed in IPLD group (0% vs. 10.1%, P=0.003). No significant differences were observed in gender, smoking status, BMI, laterality, operation time, wedge resection involving single or multiple lobes, prolonged air leak, or overall complications.

Further comparisons between the IPLD and non-IPLD groups after propensity score matching were presented in Table 3. We chose parameters including age, Light index, chest tube suction for matching to control potential selection bias. After matching, no significant differences were observed regarding factors including patient gender, age, smoking status, BMI, Light index, chest tube suction, and resection involving single or multiple lobes. The result showed that IPLD group had shorter chest tube indwelling time (1.85±0.93 vs. 2.57±1.94 days, P=0.01), shorter postoperative hospital stays (2.85±0.95 vs. 3.54±1.67 days, P=0.006), shorter ATC distance at POD 0–3 (8.31±5.86 vs. 11.3±8.77 mm, P=0.03) and POD 4–14 (5.18±8.87 vs. 11.03±13.97 mm, P=0.007), and lower postoperative recurrence (0.0% vs. 9.8%, P=0.03) than the non-IPLD group.

Discussion

To the best of our knowledge, this is the first study investigating whether additional IPLD may further promote lung expansion and decrease PSP recurrence after VATS bullectomy with pleurodesis. In our current study, the overall recurrence rate after VATS was 4.6% (7/153), which was comparable to reported recurrence rates in literature review, ranging from 3.8% to 8.1% (13-16). Our result indicated that the PSP patients who underwent VATS procedures with IPLD had shorter ATC distance at both POD 0-3 and POD 4-14, shorter chest tube indwelling time, postoperative hospital stay, and postoperative recurrence than those patients without IPLD after propensity score matching.

In 2008, Gaunt et al. revealed the correlation between the RAPS and the recurrence of both primary and secondary pneumothoraxes, but without quantitative measurement (17). We were the first to quantify RAPS by using the simple ATC distance measurement and concluded in our previous study that if the lung failed to expand well, to reach full contact with (ATC distance <1 cm) the apical parietal pleura within 2 weeks, the risk of postoperative recurrence would be higher (10). The result was verified in the current study, in which significantly larger ATC distance at POD 4–14 was observed in the recurrence group (Table 1). The finding further inspired us to apply IPLD in addition to VATS bullectomy with pleurodesis during our practice, trying to maximize postoperative lung expansion and the effect of pleurosymphysis.

To create pleurosymphysis, pleurodesis is regarded as comparably effective to pleurectomy or pleural tenting, with the advantage of shorter procedure time. Mechanical pleurodesis is performed using pleural abrasion covering at least the upper half of parietal pleura and has been our routine practice for over 15 years. Chemical pleurodesis is applied through pleural instillation with various sclerosing agents including minocycline, tetracycline, talc and bleomycin (18-20). Both pleurodesis methods are generally accepted and share equal efficacies (20). However, the expected pleural symphysis effect would become suboptimal if the lung fails to rise to the apex of the pleural space, to have maximal opposing pleural contact. Chest drainage suction is widely utilized to facilitate postoperative lung expansion and shorten chest tubes indwelling period and hospital stay for pulmonary resection management (21). and also adopted in the majority of our patient series. Nevertheless, some claimed otherwise by showing no benefits in suction-applied group to decrease the air leak duration over the water-seal group (22,23). Therefore, suction or not is often at the surgeons’ discretion. To minimize the potential selection bias, we included the chest tube suction factor in the propensity score matching.

IPLD can theoretically help the remaining lung to float, especially the lower lobes after upper lobectomies, to obliterate the RAPS and to reduce the air leak, pleural effusion, and potential empyema, but this procedure is performed at the cost of potential bronchial deformity and stenosis, or even lung torsion (24-26). However, strong supportive evidence regarding its efficacy is lacking. In 2025, a meta-analysis by Chen et al., including two prospective randomized controlled trials and seven retrospective case-controlled studies reported no significant differences in postoperative drainage volume and time, dead space assessment, and postoperative complications between patient groups with or without IPLD. They concluded that IPLD is not effective in reducing the postoperative complications (27). However, nearly all the studies focused on major lung resections, particularly upper lobectomies. In this setting, the obliteration of the RAPS could not be accomplished with the effect by IPLD only, but along with contralateral lung inflation, mediastinal shift, and diaphragm elevation all together (10,17). We proposed that effect of the IPLD would be more high-lightened for minor lung resection, such as bullectomy for PSP. Considering the patients chosen for IPLD application in our retrospective cohort is often surgeons’ preferences, we managed to minimize the potential and inevitably selection bias using propensity score matching to control factors including patient age, pneumothorax severity by Light index, and chest tube suction. The analysis after matching suggested that IPLD significantly reduced postoperative RAPS and recurrence after VATS bullectomy with pleurodesis for PSP.

Regarding the postoperative complications, the integrity of pleura covering the lower chest wall was proposed to be crucial for the reabsorption of the pleural effusion (28,29); hence, the IPLD might raise the concern of residual pleural effusion problem. In our data, no significant differences between the IPLD and non-IPLD groups in terms of postoperative complications including prolonged air leak, fever or refractory pleural effusion, requiring further intervention. This indicates that IPLD is a safe, time-efficient, and effective technique in addition to traditional VATS bullectomy with pleurodesis for PSP treatment.

There were several limitations in our study. Firstly, the study is retrospective, non-randomized, and conducted in single center with limited case numbers, future prospective large-scale study would be mandatory to further validate our data. Secondly, un-uniformed radiograph schedule for patients prompts us to group postoperative chest films into two time-windows of POD 0–3 and POD 4–14 for better analysis. Thirdly, the resected lung volume could not be precisely assessed due to the retrospective cohort study character with long time span; routine CT scan, particularly raw data of thin slice CT scan is lacking for further detailed analysis of size, number of bullae or even small blebs, or even more difficult emphysematous lung volume analysis; further the preoperative estimation of target bullectomy area does not necessarily correlate to exact final resected volume for surgeon’s discretion during the operation. We tried our best to semi-quantitatively stratify the resection volume as single or multiple-lobe involved. The influence of resected lung volume on the postoperative recurrence remains to be clarified in the future study with pre- and postoperative CT 3D simulation lung volumetrics analysis. Fourthly, the RAPS estimation using ATC distance documentation on chest radiograph might include residual air and fluid as well; however, further clarification of each individual influence is extremely difficult. Fifthly, functional assessment including pre or postoperative pulmonary function, and wound pain assessment along with pain control analysis are lacking.

Conclusions

In our study for PSP surgical treatment, IPLD not only reduced postoperative RAPS with lowered ATC distance measurement at both POD 0–3 and POD 4–14 on chest radiography but also shortened chest drainage time and hospital stay. Notably, it significantly lowered postoperative PSP recurrence rate. Our result suggests that IPLD is feasible, effective, and could be considered as a good supplementary procedure to VATS bullectomy and pleurodesis for PSP prevention.

Acknowledgments

We thank Dr. Hsin-Yi Yang for her professional support and advise in our statistical analysis.

Footnote

Reporting Checklist: The authors have completed the STROBE reporting checklist. Available at https://jtd.amegroups.com/article/view/10.21037/jtd-2025-1022/rc

Data Sharing Statement: Available at https://jtd.amegroups.com/article/view/10.21037/jtd-2025-1022/dss

Peer Review File: Available at https://jtd.amegroups.com/article/view/10.21037/jtd-2025-1022/prf

Funding: This work was supported by the Ditmanson Medical Foundation Chia-Yi Christian Hospital (grant number R109-035, to J.M.C.). The funder had no role in the study design, data collection, analysis, interpretation, or decision to submit the manuscript for publication.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://jtd.amegroups.com/article/view/10.21037/jtd-2025-1022/coif). J.M.C. received internal research support from Ditmanson Medical Foundation Chia-Yi Christian Hospital (grant number R109-035). The other authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The study was reviewed and approved by the Institutional Review Board of Ditmanson Medical Foundation Chia-Yi Christian Hospital (IRB approval number: IRB2020004). Informed consent was waived due to the retrospective design of the study.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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