In the present study showed that in onlay VHR, the use of TCM did not affect recurrence but significantly reduced foreign body feeling and chronic pain by a significant degree compared to PM. SSI appears to be linked to increased recurrence of two meshes in this repair. Moreover, the increase in defect size was associated with both foreign body feeling and chronic pain in onlay VHR with PM.
Currently, the use of mesh for incisional hernia repair is recommended at Grade A level from Oxford Centre of Evidence-Based Medicine [9]. Nevertheless, which technique is best for VHR is still controversial. Wéber et al. identified less recurrence with the onlay technique compared to the sublay technique for large ventral hernias (>25 cm2) [10]. In contrast, in the meta-analysis by Timmermanns et al., the sublay technique was stated to cause less SSI and recurrence compared to the onlay technique for incisional hernia repair [11]. Similarly, in the review by Liang et al. in 2017, the sublay technique was recommended for incisional hernia repair [12]. Additionally, if the onlay technique is to be used, it was emphasized that care needs to be taken of many factors like patient selection, surgeon experience, careful dissection and prophylactic measures (drainage, abdominal binders, etc.) to reduce possible complications. In the present study, all operations were performed with the onlay technique and our reason for choosing this technique is that our surgical experience was greater with onlay repair.
In a nationwide prospective study of the Danish Ventral Hernia Database, Helgstrand et al. found that a large hernia defect (>7 cm) was stated to be statistically associated with recurrence for onlay incisional hernia repair [13]. In contrast, in the present study, only in patients using PM was the increase in defect size significantly associated with foreign body feeling and chronic pain; however, there was no significant increase observed in recurrence rates. On the other hand, the authors have many advantages like greater patient numbers, comparison of different surgical techniques, and assessment of early and late complications in their study compared to this study. However, the authors stated they did not analyse factors like smoking habits, BMI and comorbidities in their study. These parameters were investigated in this study, but no significant correlation was identified between these factors with recurrence, foreign body feeling and chronic pain. In onlay VHR, if we consider that the use of a mesh with larger surface area is required with the increase in defect size. Thus, we can state that the greater surface area of the mesh may be the factor affecting formation of mesh-related complications [13]. For example, in a retrospective cohort study by Kroese et al. in 2018, investigated external validation of the EHS classification for a postoperative complication after incisional hernia repair [14]. They found that there were significant differences between W1 and W3 class hernia in terms of postoperative complications (wound, medical and surgical) (p < 0.001). Likewise, investigated this classification in this study too. However, no patient with W3 class hernia was observed. Nevertheless, the EHS width classification was associated with foreign body feeling and chronic pain in the polypropylene group (p < 0.001). Additionally, the authors stated the EHS width classification is associated with postoperative complications. Likewise, the results of this study suggest that the EHS width classification is useful for predicting the foreign body feeling and chronic pain after incisional hernia repair. In another prospective study of the authors, primary and incisional hernia were compared in terms of postoperative complications [15]. They found overall complication rates (wound, surgical, and medical) were significantly different (4.4%) for primary hernia versus (15%) incisional hernia (p < 0.001). Similarly, in this study, found a same result for foreign body feeling and chronic pain (p = 0.029).
Recurrence is one of the complications that can develop after VHR and is an undesirable situation for both patient and surgeons. Though there are many factors increasing recurrence, one of the most commonly blamed factors is DM [16]. Moreover, for DM, a HbA1c >7% has been found to be associated with an increased risk of wound infection [17]. As a result, diabetic patients with poor blood sugar control have increased SSI which increases the possibility of recurrence. In this study, two patients with recurrence identified had DM and one of these patients had HbA1c level above 7%. However, two patients had SSI. In this study, though not statistically, we think the recurrence rate was clinically significantly increased by DM. Today, the incisional hernia repair still has a high incidence of SSI (0.7%-26.6%) [18]. In a prospective study by Juvany et al. in 2018, stated that SSI significantly increased one-year recurrence rate (16%) for elective incisional hernia repair (p = 0.047) [19]. However, they found that the only risk factor identified for SSI by the multivariable analysis was the presence of seroma and hematoma (p = 0.042). The results of this study were very similar in terms of seroma and SSI. A review by Köckerling in 2018, stated that the mean recurrence rate was 9.9% (0-32) at follow-up of 1-8 years for onlay VHR [20]. In this study, the recurrence rate was 1.25%, with a mean follow-up duration of 28 months for all patients. Though many factors may play a role in this difference in recurrence rates, we think it may be due to the shorter follow-up duration in this study. In the literature, there are studies researching the correlation between mesh weight and recurrence in hernia repair. For example, a randomized prospective study by O’Dwyer et al. stated that the use of lightweight mesh for inguinal hernia repair caused less recurrence than the use of heavyweight mesh [21]. Conversely, in studies comparing TCM with PM as in this study, Schopf et al. [22] and Koch et al. [23] stated the opposite and suggested that there was no significant difference between both meshes regarding recurrence. Likewise, in this study, no difference was found between meshes in terms of recurrence.
It is well known that meshes used for hernia repair cause inflammation and this leads to foreign body reactions. Post et al. stated that a foreign body reaction caused by meshes leads to foreign body feeling [24]. In another study by Orenstein et al., it was stated that lightweight meshes lead to less foreign body feeling than heavyweight meshes [25]. Similarly, in several experimental studies, it was stated that TCM led to less foreign body reaction than identical meshes [26, 27]. In this study, foreign body feeling was found to be significantly less in patients with TCM. We think that the reason for this is that the mesh used was a lightweight mesh.
Chronic pain is also a common complication of VHR and multifactorial in aetiology [28]. The most important factors in the aetiology are surgeon experience, surgical technique and mesh characteristic. This pain is mostly associated with the mesh itself and frequently is related to a foreign body reaction and inflammation tissue response caused by the mesh and stiffness and shrinkage ensuing as a result [29]. In the literature, there are studies researching the correlation between inflammatory response and mesh weight. For instance, in an experimental study by Junge et al. in 2005, no incompatibility was observed in terms of biocompatibility between lightweight TCM and heavyweight PM, and they showed that inflammatory response was considerably low [30]. Similarly, Pereira-Lucera et al. reported that an inflammatory response was significantly low for lightweight TCM compared to meshes containing polyglactin + polypropylene [31]. Generally, in these studies, lightweight TCM was shown to cause less foreign body reaction and scarring compared to heavyweight PM. These results support the lower chronic pain rates among patients using TCM in the present study. On the other hand, in the literature, there are studies analysing the chronic pain rates in VHR performed with different techniques. Similar to the present study, in a study about onlay repair with PM, Kingsnorth found the incidence of chronic pain to be 18% in patients with large abdominal defect (>10 cm) [32]. However, different from this study, the authors added component separation and fibrin sealant to this technique. With the underlay technique, another study with lightweight mesh by Gronnier et al. with 109 patients and mean 24-month follow-up stated 34% had chronic pain [8]. The authors identified that chronic cough (a cough lasting eight weeks or longer) significantly increased the chronic pain rate. In the current study, no patient with large abdominal defect was observed and chronic cough was not assessed. Chronic pain identified at lower rate in both mesh groups in this study. We think that a lack of the large abdominal defect in this study could affect chronic pain rates. A prospective study by Welty et al. assessed patients with sublay technique using different weight meshes in terms of chronic pain [33]. They found the chronic pain rates (at rest and during heavy work) according to mesh weights (heavy, mid and lightweight) were 17%, 6%, 7% vs. 9%, 3% and 0%, respectively. In this study, these rates were 1%, 6.2% vs. 0% and 0%, respectively. A common point between the studies by Wind et al. and this study is that though different surgical techniques were applied, the reduction in weight of the mesh significantly reduced chronic pain rates. Generally, the chronic pain rates in this study are partly consistent with the literature.
There are several limitations to the findings of the current study. Firstly, this study was retrospective and conducted with a limited number of patients. Secondly, owing to the VAS scale not having a specific identification and pain being a subjective finding, type 1 errors may be present at the statistical significance level. Due to the retrospective design of this study, we could not perform strong and valid tools like the Carolinas Comfort Scale or McGill Pain Scale for postoperative pain and functionality. Despite these limitations, the advantage of our study is that operations were performed by a single surgeon and it is a single-centre study. Moreover, one of the other advantages is that there are very few studies in the literature about recurrence, foreign body feeling and chronic pain in the long run when lightweight TCM is used for VHR. Although this study focuses on the effects of TCM on recurrence, foreign body feeling and chronic pain, many findings were also detected about SSI and seroma in onlay VHR with TCM. Therefore, further studies, which take these variables into account, will need to be undertaken.