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Chronic Pain after Laparoscopic Inguinal Hernia Repair Depends on Mesh Implant Features: A Clinical Randomised Trial

The use of alloplastic materials has become the standard procedure in inguinal hernia surgery [1-6]. Hernia surgery is one of the most common visceral operations and thus of great medical and economic importance. Many publications have shown that there are advantages in the early postoperative outcome and lower recurrence rate when using techniques with mesh implantation compared with mesh-free inguinal hernia repair [1-6]. Therefore, inguinal hernia repair with mesh has become the standard in the last 20 years. Open surgery according to Lichtenstein was used most often at the earlier times, whereas minimally invasive techniques have been increasingly applied in the last decade [1-6]. Chronic pain is the most frequent long-term complication after inguinal hernia repair. Its perceived risk varies widely in the international literature. There are studies describing a higher rate of chronic pain after laparoscopic hernia repair in comparison to the open surgery and there are also studies describing it the other way round. Nevertheless, mesh associated chronic pain after hernia repair is an often described phenomenon [7-9].


Introduction
The use of alloplastic materials has become the standard procedure in inguinal hernia surgery [1][2][3][4][5][6]. Hernia surgery is one of the most common visceral operations and thus of great medical and economic importance. Many publications have shown that there are advantages in the early postoperative outcome and lower recurrence rate when using techniques with mesh implantation compared with mesh-free inguinal hernia repair [1][2][3][4][5][6]. Therefore, inguinal hernia repair with mesh has become the standard in the last 20 years. Open surgery according to Lichtenstein was used most often at the earlier times, whereas minimally invasive techniques have been increasingly applied in the last decade [1][2][3][4][5][6]. Chronic pain is the most frequent long-term complication after inguinal hernia repair. Its perceived risk varies widely in the international literature. There are studies describing a higher rate of chronic pain after laparoscopic hernia repair in comparison to the open surgery and there are also studies describing it the other way round. Nevertheless, mesh associated chronic pain after hernia repair is an often described phenomenon [7][8][9].
Meshes cause rigidity, shrinking, chronic pain, adhesion formation as well as infl ammatory process concerning epididimis and vas deferens [10][11][12][13]. Permanent relief of pain or discomfort and low incidence of peri-and postoperative complications and recurrence rates are the goals of successful hernia repair. In laparoscopic inguinal hernia repair the inguinal region is approached and hernia repair is performed from the interior side. Exploration and placement of staplers in the internal inguinal region during laparoscopic hernia repair may induce specifi c complications such as nerve entrapment, neuralgia, hematomas [14][15][16]. In laparoscopic procedures mainly polypropylene meshes are used due to its strength and incorporation characteristics [15,17,18]. They provoke a strong stimulus for chronic infl ammatory response [16][17][18][19][20].
These problem has led to the development of different meshes characterized by a reduction of the polypropylene volume, an increase of the pore size and different web structures [21,22]. discomfort and stiffness of the abdominal wall [11,15,[23][24][25]. The impact of laparoscopic inguinal hernia repair on open radical retropubic prostatectomy is dicussed and it is described that pelvic lympadenectomy could be compromised [24][25][26]. However, urological affections or disorders do play a leading role in the popstoperative disorders like dysuria, touchsensitiveness of the testicle or ejaculation with pain [16].
The designed prospective comparative clinical trial, investigated the compatibility of three different meshes (Table 1) in patients undergoing laparosopic transabdominal polypropylene plastic (TAPP) for primary inguinal hernia in long-term follow-up. In every case we used the same surgical technique, inserting three different meshes with different percent of polypropylene or structure. We investigated the consequences of reducing the quantity of nonabsorbable polypropylene (two pure heavy-weight polypropylene meshes, or a polypropylene-polyglactin tangle) and of different structure (double-and multifi lament heavy-weight polypropylene mesh) by means of urological affections and life quality.

Methods
The study was conducted in accordance with the Declaration of Helsinki and all its amendments. Patients declared their approval of the study by signing an informed consent document.
In the years 1999-2001 one hundred eighty male patients undergoing a laparoscopic transabdominal hernia repair for primary inguinal hernia and fulfi lling the criteria were included into the study. After the process of randomisation 60 patients were treated with mesh A, 60 got mesh B and 60 mesh C implanted ( Figure 1). In every group 60 patients were allocated to intervention. In group A only 58 patients received the intervention. In two cases the Lichtenstein procedere had to be done because of massiv peritoneal adhesions. Also one person in group B had an operation of Lichtenstein. In group C two patients received open hernia repair because of peritoneal adhesions, like in group A ( Figure 1). Inclusion criteria were: male patient, one-sided inguinal hernia, age between 35 and 75 years, BMI less than 30. The exclusion criteria were: peripheral arterial disease worse than clinical stage II b, recurrent inguinal and scrotal hernia, neurological affections or paresthesia of the genital region or the lateral region of the proximal lower extremity, polyneuropathy, disturbance of the testicular blood circulation with testicular atrophy, therapy with anticoagulative drugs, chronic back pain, intraoperative conversion to open procedures, hydrocele, epididymitis, funiculitis, femoral hernia or incarceration.
After the process of randomisation we had three groups: A: 60 (average age 61.5 years) of these were treated with a monofi le, heavy-weight (108 g/m 2 ) and double-fi lament polypropylene mesh. B: 60 (average age 62.3 years) got a multifi lament, heavy-weight variant (116 g/m 2 ) of polypropylene mesh beeing composed by multifi le material implanted. C: 60 patients (average age 63.2 years) were treated with a composite-mesh made of polyglactin (PG) and polypropylene (PP) (PP 35 g/m 2 ) ( Table 1).

Randomisation
The coincidence distribution was done with prepared envelops. The day before the operations every patient has to tear an envelope with a card inside. The name of the mesh was typed on the card. Every surgeon (two fi xed teams) received a list with the name of the patient and the sort of mesh that had to be implantated. The surgeons who implanted the mesh were not included in the follow-up. Neither the patients nor the investigating doctor were informed about the type of mesh used (Table 1).

Follow-up of the patients
On the day prior to the operation a detailed physical investigation with determination of the blood routine-  was also closed with a resorbable suture (Ethicon, Vycryl 3/0).
The two surgeons, who carried out the operative procedure, had a long experience of laparoscopic hernia repair procedure with more than three hundred.

Results
The three groups were comparable in terms of group size and age structure, body mass index and comorbidities as well as the local fi ndings ( Table 1). The overall follow-up rate was 97.2% after 60 months ( Figure 1): We lost two patients in group A after two years: one died and one did house moving. In group B one patient died after one year of follow-up and in group C we lost a patient after two years ( Figure 1).
Overall we analysed 58 patients of group A, 59 patients of group B and 58 of group C.
In each group we found COPD, hypercholesterinemia and -lipidemia, arterial hypertony and coronary heart disease at comparable percentage (  In all group the surface was determined between 3 and 16 cm 2 . The patients spent nearly the same time in hospital (group  (Table 3). We had an overall recurrence rate of 2.3 % (two in group A, one in group B and one in group C). In all these cases we found medial recurrences caused by partial mesh migration. There were no signifi cant differences between the individual groups as regards the frequency of recurrence.
From the fi rst postoperative week in all groups an increase of touch-sensitiveness of the testicle at the operated side, pain with ejaculation and discomfort with urination could be documented (Table 3). These symptoms became signifi cant different (p<0.05) in the 4 th and 12 th postoperative week (Table   3) in group A compared to groups B and C.
Regarding the pain development measured with visualscales one could fi nd signifi cant (p<0.05) more pain from the 1 th day after the operation up to the 12 th postoperative week ( Figure   2) in group A. In the other groups there was no signifi cant  men. Sensory disturbances are described in many patients after inguinal hernia repair without chronic pain [16,27,28]. Corresponding to the results of previous studies comparing pure polypropylene meshes and Vypro II meshes we found no differences in the recurrence rates up to 60 months after the operative procedure [21,29].
Horstmann et al. [29], examined the impact of polypropylene Beyond this point of time there were no signifi cant differences in our three groups. In the long-term follow up (60 month) no signifi cant difference was documented. The difference was just signifi cant in the short-and the mean-term follow up.
Schmidtbauer et al. showed that large pore-sized, lowweight polypropylene meshes composed of multifi laments (e.g., Vypro II), had better abdominal wall compliance and caused less chronic pain than large pore-sized, monofi lament heavyweight polypropylene mesh (e.g., Prolene) [25]. In contrast we did not fi nd an advantage of the composite mesh concerning It is quite interesting, that the differences seem to diminish in the long-term follow up. After 60 month we could not fi nd any signifi cant differences between the three groups. The process of incorporation of the materials seems to provoke different reactions refl ecting in pain development, life quality and discomfort. But after the 12 th week of operative therapy these differences are not evident anymore in our groups.
Nevertheless, we found still 5% of patients suffering from chronic pain and discomfort in the long-term follow-up independent which mesh was implanted.
There is a need for evidence-based treatment strategies for established chronic pain. Few prospective long-term follow-ups of large cohorts suggest a burn-out rate of about 50% within 5 years. Some positive results have been reported using neurectomy. But the literature on surgical treatment of chronic pain after laparoscopic inguinal hernia repair does not allow any fi rm recommendations [26]. Pharmacological treatment of chronic pain after hernia repair has not been established, gabapentanoids and tricyclics may play a role.
Local anaesthetics may prove useful concerning the relatively limited anatomical pain area [16].
In conclusion, independent which mesh was implanted still 5% of the patients are suffering from discomfort after fi ve