In this study, a newly introduced implant of a different design resulted in an improved pain profile and lower recurrence rate at 60-month follow-up, compared to rates for the knitted polypropylene traditionally used for Lichtenstein hernioplasty. We have confirmed that this mesh may be used in a routine clinical setting as the first-choice mesh for inguinal hernia repair. This multicentre trial was created based on our previous findings from a small pilot study that indicated the possible advantages of this implant [
11]. Previously, we encountered less pain with WN versus heavyweight polypropylene mesh, and no recurrences in the WN mesh group. The group treated in that study was quite small (25 patients in each cohort), so those differences might have been coincidental. Based on those results, it was mandatory to design and conduct a larger trial.
In recent decades, many studies had proven that use of mesh decreases acute pain (up to 6–12 months) compared to tension methods. However, the incidence and intensity of postoperative pain are still high, affecting up to 20% of patients operated on with mesh [
12,
13]. To reduce this problem, companies are searching for new materials that can potentially reduce the number of patients suffering from pain due to the presence of a foreign body after the procedure. Experimental studies have shown that the extent of reaction to a foreign body, with the scar tissue and inflammatory reaction it provokes, depends on the amount and structure of the material implanted [
4]. New meshes have been introduced into the market. An absorbable component has been added to the polypropylene fibres to decrease the weight of mesh during the incorporation process, and the potential advantage conferred by partially absorbable light-weight meshes, such as Vypro, Vypro II and Ultrapro, has been confirmed in clinical studies conducted by Post, O’Dwyer and the Polish Hernia Study Group [
5,
6,
8]. The incidence of pain of any sort was generally two times lower in lightweight mesh groups, but the values ranged from 39% [
5] to 3.8% [
8] for the LW meshes, and from 51% to 6.8% in the HW groups, respectively. On the other hand, Bringman found no significant difference in pain scores when a Vypro II implant was compared with polypropylene mesh in another large study (only the pain occurring when rising from a lying to a sitting position was lower in the lightweight mesh group) [
7]. There is no meta-analysis of the above-mentioned trials, and the values measured seems to differ due to the different protocols used for assessment of pain. In our present study, early postoperative pain depended on the mesh used. These trends were also noted over the first 3 months, but the small number of patients precluded definitive statistical evaluation. However, the incidence of pain observed here was comparable to pain from lightweight meshes, which may also confirm the findings of other trials [
8,
14]. For other meshes (low weight partially absorbable meshes), the tissue reaction and fibroblastic ingrowth creates a scar that is responsible for mesh shrinkage; this has been described in experimental studies [
4]. Formation of an elastic scar on megaporous meshes should theoretically prevent pain and/or a feeling of a foreign body in the groin. These differences in pathophysiological processes have not been observed for the WN implant. Experimental studies have shown no statistical differences in visual sign of inflammatory response (electron-microscope measurements), fibrotic reaction and implant integration for non-woven mesh compared to HW knitted polypropylene [
15]. Only the total amount of macrophages at the site of the mesh was statistically higher in the non-woven mesh group, which supports the assumption of a more pronounced inflammatory reaction caused by the mesh structure [
15].
In the last few decades, recurrence has been shown to be an outcome of less value than pain, due to an incidence below 1–2% in 3–5 years of follow-up. Introduction of lightweight meshes has again focussed attention on this complication. In most studies, the recurrence rate was significantly higher in the lightweight mesh groups, being as high as 5% [
6]. The authors of the O’Dwyer’s trial suggested that the high rate of recurrence may be a consequence of the different elastic properties of Vypro II mesh, and could require modification of the fixation technique. The modification of the operative technique postulated by O’Dwyer and applied by the Polish Hernia Study Group has reduced the recurrence rate to accepted levels of about 2% in first year of observation [
8,
16]. Although the rate noted in the present study was less than 2% after 1 year for the HW implant, it was lower still in the non-woven WN group. Additionally, the WN mesh described here does not require any modification of the classical Lichtenstein technique due to its firmness and shape memory. We did not find any differences when handling and suturing this implant. In this study, as in the pilot study, we did not observe any recurrences in the WN group up to 1 year, and very low recurrence rates after 5 years.
Summarizing the described findings, we conclude that the examined lightweight implant shows good results in preventing postoperative pain, being comparable with other low weight materials and superior to HW mesh. Also, the low recurrence rate at 5-year follow-up confirms the value of this implant, especially considering that long-term results have not been described for other LW materials to date. WN mesh can be safely considered as an appropriate choice of implant for primary inguinal mesh repair.