Pain is usually assessed subjectively by means of verbal or visual intensity scales and questionnaires [9, 21]. Most pain scales are subjective assessment tools because pain is interpreted differently by each individual. In this study, diligent attempts to control as many confounding variables as possible were made - such as the subjective individuality. This was achieved by performing two incisions in the same patients during the same operation session and asking them to rate their incision-related pain at the same six postoperative time points. Incision length, chest tube size and perioperative analgesic protocols were all controlled for. Careful attention toward reducing the influence of these potential confounders should reduce their effect on our results and produce a more reliable comparison of pain following thoracic surgery.
In contrast to the literature’s overwhelming opinion that subxiphoid VATS results in much less early postoperative pain than intercostal VATS following thoracic surgery [12–16, 18], our study found the subxiphoid incision produced more pain than the intercostal incision during the early postoperative period (POD-1, POD-2, and POD-Discharge), but only in the bilateral VATS group, not in the unilateral VATS group. The authors suggest one reason for the difference may be because the subxiphoid incision was always made below the xiphoid process and slightly tilted in the direction of the operative costal arch. There was greater distance between the two incisions (subxiphoid and intercostal) in the bilateral VATS group than that in the unilateral VATS group, which could possibly decentralize a patient’s focus of attention. Another reason may be that nine of 15 patients in the unilateral VATS group received 3-port VATS. The chest drains were placed through a small intercostal port which has been reported to have negative impact on pain in the literature [20]. This would also confound perceptions of pain for other incisions. These two factors could interfere with a clear comparison of pain between subxiphoid and intercostal incisions in the unilateral VATS group.
Although the findings of this study were in contrast to findings in the literature (less early postoperative pain in subxiphoid compared to intercostal VATS), the present study did find higher pain intensity associated with intercostal incisions in the late follow-up period (POD-90 and 180), consistent with the literature [18]. None of the eleven patients receiving bilateral VATS reported chronic pain (pain lasting 2 to 3 months) over the subxiphoid incision, while four (4/11) reported pain over the intercostal incision on POD-90 and two reported pain through until POD-180. One of the fifteen patients receiving unilateral VATS reported pain over both subxiphoid and intercostal incision and two reported pain over the intercostal incisions on POD-90. The two patients reporting on POD-90 continued to report the same pain on POD-180. It is interesting to note that five of the seven patients who reported chronic pain in our cohort study had primary lung cancers or lung metastases for which they received adjuvant chemotherapy within six months of surgery. One of the seven had pulmonary tuberculosis for which he received six-months of anti-tuberculosis therapy and the other received an unexpected surgical intervention for acute cerebrovascular disorder within three months following thoracic surgery. Previous studies have reported that pain can be expressed or experienced differently depending on race, gender, age, treatment modalities including radiotherapy, pleurectomy, more extensive surgical procedures, and other multifactorial mechanisms [19, 23]. Recently, Yoon and colleagues also reported that adjuvant chemotherapy serves as a risk factor for chronic pain in lung cancer patients after VATS [26], supporting the findings of this study.
The use of subxiphoid VATS incisions avoids intercostal nerve damage, which has often been cited as a major source of postoperative pain and paresthesia after thoracotomy and intercostal VATS. From a surgical standpoint, this approach allows easier access to the anterior mediastinum for thymectomy as well as better access to both sides of the chest with only a single incision. However, this approach, particularly when there is posterior mediastinum and left thorax involvement, can be challenging even for experienced thoracic surgeons. Whether the potential advantages outweigh the potential disadvantages remains to be determined by future studies.
Reviewing the literature, we found it took a long time for the field to draw a firm conclusion regarding relative reported pain associated with thoracotomy versus VATS [1–3, 9, 19]. The debate regarding the relative pain associated with multiportal VATS versus uniportal VATS is also ongoing [5–8]. Until now, only a few studies have reported a reduction in acute postoperative pain and chronic pain associated with subxiphoid VATS [12–16, 18].
This study has a number of limitations. The difficulty in recruiting patients who required receiving two procedures in the same locations at the same time meant the limitation of a small sample size was unavoidable. Another limitation is that all the procedures in this study were performed by one surgeon at one institute, and so the learning curve for the performance of subxiphoid VATS has not been taken into consideration. Therefore, further studies including well-controlled prospective studies and multi-center studies are needed to further verify our findings.