Prosthetic reinforcement has become the standard treatment of groin hernias compared to suture repair, since it significantly reduces the risk of recurrence and chronic pain [1
]. However, the first generations of meshes, commonly polypropylene and polyester, were associated with side effects such as pain and reduced abdominal wall compliance [2
]. This has resulted in less foreign material in the development of modern meshes. The main properties of the mesh are found to be the type of filament, tensile strength, and porosity [3
]. These can affect the weight of the mesh and its biocompability to the abdominal wall when it comes to flexibility and discomfort [3
]. When decreasing the amount of polypropylene and increasing the pore size, less foreign body reaction is produced [4
]. The so-called lightweight meshes (LWM) can, therefore, provide adequate strength for hernia repair with less associated side effects [5
]. The previous studies have shown benefits of LWM compared to heavyweight meshes (HWM) in terms of improved aspects of pain, discomfort, and early return to normal activity after surgery in open anterior mesh groin hernia repair (Lichtenstein) [6
]. LWM appears to have similar advantages in laparoscopic totally extra-peritoneal repair (TEP), as well [8
]. However, concerns exist if it may have an increased risk of recurrence, especially for larger hernia defects [9
The aim of the study was to compare the reoperation for recurrence rate in a large number of hernias with long-term follow-up following the use of LWM versus standard HWM in TEP. The hypothesis was that LWM does not increase reoperation for recurrence rate compared to HWM.
This study is, to our knowledge, the largest cohort that compares the risk of reoperation for recurrence in lightweight and heavyweight meshes in TEP repair with a long follow-up.
Recurrence is an undesirable complication after groin hernia repair and our hypothesis was that LWM was comparable to HWM in respect of recurrence rates. This was not entirely supported in this report with 13,839 hernias operated in Sweden, recruited from the Swedish Hernia Register. Instead, we detected an increased risk of recurrence after use of LWM compared to HWM both in the univariate and multivariate statistical analyses. The difference in recurrence rate between the mesh groups could be considered as small and overall low. The total reoperation rate for recurrence in our material was 3.5 per cent. This corresponds well with the findings published by the International Endo Hernia Society’s (IEHS) guidelines reporting an incidence even lower at specialized centers [13
The previous studies have reported a higher recurrence rate after TEP repair with LWM compared to HWM, although not statistically significant [9
]. However, Burgmans et al. reported in the recent randomized controlled trial with 2-year follow-up not only a significant higher recurrence rate in LWM, but also an increased rate of chronic pain compared to HWM [15
]. The IEHS’s recommendation is that meshes with large pores are more beneficial to use than meshes with more foreign body material [14
]. The theory is that HWM is oversized with regards to the mechanical properties that can lead to more postoperative pain and stiffness [16
]. The findings are summarized from controlled-randomized studies, with short-to-medium-term results having different postoperative aspects as primary outcome [8
]. However, these studies have been undersized in terms of number of patients and have had insufficient follow-up time to detect a difference in recurrence rate between HWM and LWM. Therefore, the strength of our study is the large number of unselected TEP hernia repairs conducted during a 9-year period. The data from SHR represent both low- and high-volume TEP surgeons from almost the whole nation, eliminating single surgeon and possible center bias, as opposed to TEP experts that normally are operating in randomized clinical trials. A randomized control trial is considered to be the golden standard to establish reliable clinical results. However, since recurrence rate is low with only a few percent presenting recurrences after 3 years of follow-up, a good RCT has limitations to implement the number of hernia repairs that requires demonstrating a significant difference between the meshes. Our study with 13,839 TEP hernia repairs over an 11.5-year period makes it possible to analyze risk factors of reoperation for recurrence with a long follow-up. However, the study has limitations. First, patient-specific information such as smoking, obesity, medications, or status of physical activity was absent, which may have had an impact on outcome. Second, the surgeon’s technical skills in performing TEP repairs could also affect the outcome and could not be evaluated in this study. However, in all centers participating in the current study, the use of LWM resulted in higher reoperation rates for recurrence compared to HWM. Nearly, all repairs were performed by consultant surgeons and not by residents. Third, another limitation with the study is the lack of information of the mesh size. The register does not provide that data and the previous reports have shown that appropriate size may be more important to avoid recurrence than the surgical technique and type of mesh [14
]. Finally, a circumscription in this study was the use of reoperation rate for recurrence as a surrogate measure for the true recurrence rate. The previous reports presents data, showing that reoperation rate could be underestimated with 40% [20
Heavyweight meshes made of polypropylene has been used for a long period of time and the reason for a change to LWM is to avoid side effects of pain, stiffness, and foreign body sensation that could be associated with HWM [21
]. A mesh should have adequate strength, be of an appropriate size, and attain good tissue incorporation by initiation of fibrosis to prevent recurrence [5
]. The explanation for the increase of the recurrence rate with LWM compared to HWM in our study could be partly explained by the higher intrinsic weakness and the decreased formation of fibrosis that has been showed in animal experiments [22
]. The mass of fibrosis that is formed depends on the intensity of inflammatory response, whereas the two most important factors for this are the pore size and the amount of foreign material [22
]. The inflammatory response continues 3 months postoperatively and the following fibrotic changes can lead to that pain may occur later [23
]. Therefore, it is theoretically considered that increased fibrotic reaction from the use of HWM with more material would be accompanied by a higher frequency of chronic pain [16
]. The current literature regarding pain in the use of LWM or HWM shows no significant differences at 1-year follow-up after TEP [9
]. In contrast, Li et al. showed higher incidence of chronic groin pain after 6-month follow-up after use of HWM compared to LWM [27
]. The authors were also concerned about the results showing increased recurrence for LWM, especially for larger defects. Despite the conflicting data concerning pain after use of LWM compared to HWM in TEP, according to recent guidelines, one should at least avoid fixation in TEP, as fixation itself may result in chronic pain without preventing recurrence [14
]. In our study, the non-fixated meshes did not reveal an increased risk of reoperation for recurrence compared to the fixated ones. The tendency was instead that, in the TEP repairs where the mesh was fixated, it resulted in an increased reoperation rate for recurrence. An explanation for this result may be that a higher proportion of the procedure with a suboptimal dissection for the mesh had mesh fixation.
Another interesting result in the current study was the detection of older patients having an increased risk of reoperation for recurrence. Whereas most studies have not revealed age as a significant risk factor for recurrence, in our study, age above median (≥ 59 years) was significantly related to a higher risk of reoperation for recurrence. The reason why patients over 59 years had a higher recurrence rate is not yet clear. One possible explanation could be that older patients have a weaker connective tissue quality, thereby increasing the risk of recurrence. We also believe that the recurrence rate is probably underestimated particularly in older patients. It may possibly be due to not seeking care for the recurrent hernia and surgeons also being reluctant to re-operate older patients. Although the reoperation rate for recurrence was significantly higher in older patients, the difference between HWM and LWM was most evident in younger patients (Fig. 2
There was also a difference in the outcome between the genders. The reoperation rate for recurrence was in female hernia repair 1.4%, significantly lower than for male patients. We could identify two possible main explanations to the difference between the genders. First, the size of the defect that exceeded 3 cm was much lower in female hernias compared to in male hernias. Second, the high proportion of femoral defects in female patients may cause difficulty to re-operate with an anterior repair and thereby, perhaps, lower the reoperation rate for recurrence. A pre-peritoneal repair, open or laparoscopic, is the golden standard in female groin hernia repair and is supported by the low reoperation rate for recurrence in female patients in this study.
The defect of the hernia was not a significant factor related to reoperation for recurrence. In addition, neither recurrent hernias nor unilateral or bilateral repairs demonstrated any significant differences. However, in the subgroup analysis of all direct hernias in men, we demonstrated a significant difference between the meshes (Fig. 2
c). In the younger half of the male patients (< 59 years) with direct hernias, this was more evident (Fig. 2
d) compared to the older group of direct hernias (≥ 59 years), where there was no difference between the meshes. Thus, younger patients with a direct hernia had pronounced higher risk of reoperation for recurrence after the use of LWM.
Hence, in indirect hernias, the differences between the meshes were more comparable. Moreover, the use of LWM was not associated with an increased risk of reoperation for recurrence compared to HWM in smaller hernia defects (Table 3
Furthermore, similar to several previous studies, we found that hernia repairs with a defect exceeding 3 cm were associated with an increased risk of reoperation for recurrence in the univariate analysis. The intrinsic weakness of LWM and the decreased formation of fibrosis may be a part of the increased hernia recurrences after the use of LWM. The less material in LWM may not have sufficient strength to avoid bulging in larger defects.
In conclusion, this first long-term nationwide population-based study, comparing the use of LWM to HWM in TEP groin hernia repair, showed that LWM was associated with an increased risk of reoperation for recurrence. This was most evident in direct hernias (particularly in younger male patients) and in larger hernia defects. These might benefit from HWM to avoid increased recurrence rates. However, the overall difference in recurrence rate between the mesh groups was small, and therefore, other aspects, such as chronic pain, need to be considered when choosing type of mesh. The use of LWM could possibly improve other outcomes and are, therefore, recommended to be used in indirect hernias and in smaller hernia defects in TEP repair, since the risk of recurrence was comparable to HWM.