Introduction

Chronic pain is a significant long-term complication that can occur after inguinal hernia repair and can compromise the patient’s quality of life. The reported incidence of chronic groin pain ranges between 1 and 53 %, in different studies [1–9].

Whereas acute pain begins soon after surgery and is successfully managed with analgesic therapy till resolution that usually occurs within 30 days after surgery, chronic pain arises or lasts for more than 3–6 months from surgery. Chronic pain may be refractory to analgesics and could need for a surgical treatment; it is a disabling condition which may unable the patient to perform daily activities and work [9, 10].

As reported by the European Hernia Society, the so-called pain complex syndrome is a typical clinical presentation, characterized by numbness and burning sensation, groin discomfort and neuralgia that last for at least 1 year after surgery [11].

Postherniorrhaphy pain can be non-neuropathic (nociceptive) due to tissue injury, inflammatory reaction or scar tissue, or neuropathic caused by compression of one or more nerves by suture material and prosthetic material (meshoma and/or plug) or by partial or complete transection of nerves with formation of traumatic neuromas [3, 12–14].

Damage to the sensory afferent system produces partial or complete loss of touch or temperature or pressure, dysesthesia and hyperalgesia that is an amplified reaction to a nociceptive stimulus. The literature does not contain any uniform and defined data on the indication for the different procedures and on the efficacy of the various therapeutic options. Insufficient information is available on the consequences of pain on the quality of life, and few papers contain long-term detailed follow-up.

Non-surgical treatment can be performed by using anti-inflammatory drugs, antidepressives, local infiltrations of anesthetics and anti-inflammatory, laser therapy, transcutaneous electrical neural stimulation (TENS) or physical therapy [7, 15–18].

If those treatments are unsuccessful, an increasing number of studies have suggested that surgical management may obtain the complete pain relief in a high percentage of cases [1, 4, 5, 7, 13, 15–20].

This paper reports our initial experience with our surgical treatment of chronic pain after inguinal hernia repair.

Methods

All the patients who underwent a surgery for postoperative chronic inguinal pain in the General Surgery Department—Day and Week Surgery of the Multimedica Hospital in Castellanza (VA, Italy) between June 2007 and December 2011 were included for this study. All the patients had previous non-surgical treatments, in particular local infiltration with anesthetics, laser therapy, TENS and physical therapy without improvement of symptoms. Inclusion criteria were previous anterior open unilateral inguinal hernia repair and at least 6 months of pain associated with the operative procedure, with a referred VAS >7 measured at rest and during exercise.

Physical examination including neurological examination and further diagnostic with MRI, CT or US was performed preoperatively in all the patients (to exclude other problems such as muscolo-tendinea diseases, osteitis pubis, vertebral diseases and to identify eventually a meshoma). All the patients underwent also a psychological test to assess their personality (Minnesota Multiphasic Personality Inventory®-2, MMPI®-2). The MMPI-2 is most commonly used by mental health professionals to assess and diagnose mental illness. It contains 567 True–False items, and it can be used to help: assess major symptoms of social and personal maladjustment, identify suitable candidates for high-risk public safety positions, give a strong empirical foundation for a clinician’s expert testimony, assess medical patients and design effective treatment strategies, including chronic pain management, support college and career counseling recommendations, provide valuable insight for marriage and family counseling.

Our surgical treatment consists of a simultaneous double approach, anterior and posterior, to the inguinal region passing through a one single transversal incision over the inguinal canal (Figs. 1, 2).

Fig. 1
figure 1

The picture shows our transversal incision in the inguinal region

Full size image
Fig. 2
figure 2

The picture shows our simultaneous double approach, anterior and posterior (as showed by the arrows), to the inguinal region passing through a one single transversal incision over the inguinal canal

Full size image

The operations were performed under general anesthesia by the same senior surgeon, expert in hernia surgery. From the inguinal incision, after opening the aponeurosis of the external oblique muscle and of the rectus muscle, it is possible, through complete dissection of the pre-peritoneal space (Fig. 3), to expose and prepare in the lower part Cooper’s ligament, the prevesical space of Retzius and the iliac vessels, while, in the upper part, the psoas region (Fig. 4), and upper on this region the lower portion of quadratus lumborum. A recurrent hernia can be eventually taken down, suture material or plug can be removed completely and safely, the genitofemoral nerve can be identified before its bifurcation (on psoas bed) and resected at this level, and also the trunks of ilio-hypogastric and ilio-inguinal nerves sometimes can be evidenced and resected at the anterior–superior iliac spine. Sometimes, it is possible, in thin patients, go cranial to the psoas to find the quadratus lumborum and identify ilio-hypogastric nerve and distally to this the ilio-inguinal nerve: in these cases, the neurectomy of these nerves can be done at this level.

Fig. 3
figure 3

The operation starts with the complete dissection of the pre-peritoneal space, after opening the aponeurosis of the external oblique muscle and of the rectus muscle

Full size image
Fig. 4
figure 4

The pre-peritoneal space is exposed, in the upper part, until the psoas region, in which the genitofemoral nerve can be identified before its bifurcation (on psoas bed) and resected

Full size image

The anterior inguinal region is approached through the same incision. From the incision, after the dissection of the skin and subcutaneous space toward the pubic bone (Fig. 2), it is possible to approach and open the scar tissue above the external oblique aponeurosis and open the aponeurosis itself, finding below the mesh previously placed, the non-absorbable stitches and the sutures on the inguinal ligament and eventually on the internal oblique muscle when wrongly placed (Fig. 5), and remove these. With this approach, mesh and sutures can be removed, specially if in direct contact with nerves; the ilio-inguinal and the ilio-hypogastric nerves can be also identified once again and resected.

Fig. 5
figure 5

The picture shows the ilio-hypogastric nerve strangulated in a polypropylene suture, near to the pubic tubercle

Full size image

The operation ends with the positioning of a new mesh in the pre-peritoneal space, according to Wantz sutureless technique, mostly biologic or ultralight partially absorbable. The choice of the mesh was uniquely due to our preference, as at the moment no data support this kind of choice.

A follow-up of the patients was scheduled 1 week, 1, 3, 6 months and 1 year after surgery and each year until now; for most of them, follow-up is still on course.

Before surgery and during follow-up, pain is evaluated according to the visual analogue scale (VAS), at rest and during exercise.

Results

Between June 2007 and November 2011, 46 patients, with an average age of 45 years, underwent surgical treatment for chronic groin pain all after open anterior approach. Forty-two patients had previous treatment for groin hernia with anterior mesh repair without any complication; two patients developed seroma formation and wound infection after the first operation, and two patients had multiple previous hernia repair. All these patients came to our attention after a 6- to 12-month non-surgical treatment performed in other Institutions.

In 44 cases (95.7 %), complete neurectomy of all the three nerves of the groin has been done. In 2 cases (4.3 %), only the ilio-hypogastric nerve was resected, which results compressed by the mesh and fixed by a polypropylene suture on the pubic tubercle, thus being the only clear cause of pain (Fig. 5). The mesh was removed in 24 cases (52.2 %), whereas in 16 cases (34.8 %), besides the mesh, the plug was also removed (Fig. 6). Mesh or plug was not removed in the first 6 patients submitted to surgery, because at the starting of the experience, the normal “learning curve” induced us to cautious approach, while the surgical technique was studied and improved. A new mesh repair was performed in 42 cases (91.3 %), a partially absorbable mesh in 20 cases (UltraPro™, Ethicon), a polypropylene mesh in 16 cases (Hermesh™, Herniamesh) and a biologic mesh in 6 cases (Surgisis ™, Cook in 3 cases and Tutomesh ™, Tutogen Medical GmbH in 3 cases). Mesh repair was not performed in the first 4 patients, during the learning curve of the surgical technique proposed. Once again the choice of the kind of mesh was justified by personal preference related to the surgical field and not from objective data.

Fig. 6
figure 6

The picture shows a plug attached to the spermatic cord, a situation that can be the cause of chronic pain

Full size image

In 44 cases, the patients were discharged the day after surgery, in two cases the same day. The patients were examined 1 week, 1, 3, 6 months and 1 year after surgery. From that moment on, the follow-up was done from June 2008 until November 2012 for each patient evaluating the VAS at rest and during exercise. At the moment (December 2012), follow-up at 1 year after surgery is completed for all patients and range is 12–66 months.

For some patients, the follow-up is still in process, but until now, 40 patients (87 %) have complete relief of pain; two patients (4.3 %) refer persistent groin pain, but different from preoperative neuropathic pain, while in 4 cases (8.7 %), the groin pain referred before the surgical treatment persists without substantial benefit. All the patients referred for the first month a light numbness.

No relationship was found between the six cases (4 + 2) who are not responding to the therapy and the patients in which mesh and plug were not removed (6 cases) and in which the neurectomy was not completed (2 cases).

Indeed, we found any correlation between the kind of mesh used (absorbable or non-absorbable) and residual pain in the six patients.

Before surgery, the mean VAS value was 7.89, ranging between 7 and 10. Pain with VAS 7 was present in 21 patients, pain with VAS 8 in 13 patients, pain with VAS 9 in 8 patients and pain with VAS 10 in 4 patients (measured at rest and during exercise).

After surgery, the mean VAS value decreased to 1.89, ranging between 0 and 10. In the 40 patients with complete relief, the mean VAS was 0.95, ranging from 0 to 2.

For the 4 patients who did not have benefits from surgery, we have no clear explication: in fact, the situation at beginning was almost the same, the surgery was the same, and the surgeon was the same; so it is possible (although we have no data) to suppose a sort of different personality or different pain thresholds in different patients that could be detected by specific psychological test.

Discussion

The introduction of mesh repair has decreased considerably recurrence rate, so chronic pain after inguinal hernia repair has become a significant problem and one of the primary outcome parameter of clinical studies. The rate of this complication is reported to occur in about 11 % of patients [21], ranging between 1 and 53 % in different studies [1–9].

A few studies have homogeneous patient population and detailed long-term follow-up until 5 years [9, 22–27].

The literature suggests that the incidence rate of chronic pain diminishes over time. As reported in the study of Grant et al. [27] on a large and well-defined cohort of patients including patients undergoing open mesh repair and laparoscopic repair, the incidence of chronic groin pain 1 year after repair is 31.5 % and at 5 year is 19.1 % in both groups. Pain is reported as severe or very severe by 9.7 % of patients at 1 year and by 1.8 % of patients at 5 years.

Even if there are many papers in the literature examining presentation, clinical findings, causes, prevention and ways of treatment of postherniorrhaphy neuralgia, the pathogenic factors and the choice of an adequate therapy are still a controversial issues [28].

In a subset of patients, an inflammatory response to the prosthetic material implanted seems to contribute to the pathogenesis of chronic pain, but up to now, it is not reported a defined way to identify the various factors responsible for the pain complex syndrome [29–32]. A few studies examining non-surgical factors related to the patient have noted that previous pain experience, pain present before surgery, expectation of pain, fear, young age and other psychosocial factors can be predictive factors of chronic postoperative pain; for this reason, it is important to pay attention in giving right indication to surgery and obtaining a well-explained informed consent [25].

Chronic groin pain after inguinal hernia repair is usually a neuropathic pain, generally caused by a lesion or entrapment of one or more nerves of the inguinal region during surgery [3].

As reported by Lichtenstein et al. [18], the most important cause of injuries to the nerves of the groin is the lack of identification and division, if necessary, during surgery.

The study of Alfieri et al. [26] clearly evaluates the effects of preservation or division of all the three nerves on chronic neuralgia; this large-scale prospective multicenter study has demonstrated that the risk of developing chronic postoperative groin pain is directly related to the number of nerves identified. Chronic pain at 6 months after repair was zero in those patients in whom all 3 nerves were identified and preserved, whereas the incidence of chronic pain was 40 % when all the nerves were divided and 4.7 % when no nerves were identified. This is the only one study that points out that identification and preservation of the nerves of the inguinal region can reduce chronic groin pain.

On the other side, some other papers have examined the effects of preservation or division of one of the three groin nerves on chronic pain after hernia repair; some of them report a reduced incidence of postoperative chronic pain after prophylactic excision of the ilio-inguinal or ilio-hypogastric nerve, whereas other studies have not evidenced any significant difference between preservation and excision of the nerve [6, 24, 25, 33–36].

Similarly, Amid et al. [32] confirm that a thorough knowledge of the groin anatomy along with identification and preservation of the nerves is necessary to avoid the incidence of complication of hernia surgery.

These aspects were considered during an important consensus conference about prevention and management of postoperative chronic pain that was held in Rome in 2008, in which a consensus was reached regarding the definition of chronic pain and guidelines were presented to avoid or at least reduce the risk of chronic pain after surgery [37].

Management of chronic groin pain is still a problematic and controversial issue; consensus regarding choice of treatment has not yet been achieved. All articles in the literature are either descriptive studies or case reports. The treatment is usually empirical, at the beginning pharmacological and then surgical. Palumbo et al. [7] proposed a step-by-step progressive therapeutic protocol beginning from less-invasive options, using non-steroidal anti-inflammatory drugs, local infiltration of bupivacaine and methylprednisolone and in case of failure, surgical neurectomy or pharmacological therapy with carbamazepine.

A similar multi-step protocol was proposed by Lichtenstein et al. [18], starting from nerve block with bupivacaine until surgery.

As far as surgery is concerned, neurectomy seems to obtain the complete relief of pain in a high percentage of patients [1, 4, 5, 13, 15–20, 38]. The surgical treatment should consists in the excision of the nerve injured, but the exact and true identification of the nerve involved can be very difficult; for this reason, the surgical treatment must not be limited to the excision of one single nerve but of all three of them and, if possible, in a relatively virgin field such as pre-peritoneal space (after previous anterior approach).

About surgical technique, Starling proposed a two-stage operation including first ilio-inguinal and ilio-hypogastric nerves resection through an inguinal approach and next genitofemoral neurectomy through a posterior flank approach [13], and Amid proposed a one-stage operation by anterior approach with simultaneous excision of all three nerves thus avoiding a second-stage flank approach [19]; anyway, the nerves should be resected as far proximally and distally as possible to include the neural segments injured and the neural communications; the nerve resected should be ligated as to prevent formation of neuromas; suture knots, prosthetic material, staples and tacks along the course of the nerves should be removed en bloc with the nerve.

Some authors reported personal experience on combined open anterior and laparoscopic posterior approach for nerve transaction and mesh removal, with good outcomes and patients’ satisfaction [5].

The procedure we adopt for the treatment of posthernioplastic neuralgia lines up to the surgical approach proposed by Amid, with differences related to the complete dissection and access to the pre-peritoneal space, that is commonly a virgin field, where it is easy to find the genital branch of the genitofemoral nerve that can be resected completely before its subdivision. Moreover, in this space, it is possible to identify at high level also the ilio-inguinal and the ilio- hypogastric nerves and to remove, if necessary, plugs positioned deeply in the previous operation. Through the same transversal cutaneous incision in the high inguinal region, we get access also to the anterior space. With this approach, it is possible to check the course of the three nerves of the region, if visible, in order to resect them again in their distal end and to remove sutures, knots or mesh compressing structures such as cord, pubis, spermatic duct and vessels.

Since the 80s, studies report the complete resolution of chronic groin pain after surgical treatment in 70–80 % of cases, but many series have small patient population and cannot reach any statistical power. Moreover, a long-term detailed follow-up of patients is still lacking in many reports. In our experience, complete resolution of pain was possible in 87 % of patients, while in 13 % of patients, surgery was not resolutive.

Our feeling about this problem is that, even if the re-exploration of anterior–posterior inguinal repair is completed with the triple neurectomy, removal of misplaced meshes, knots, tacs and sutures, a certain number of patients will not benefit from such treatment, even if adequate, and we do not know why.

Thus, it will be crucial, in the future, to identify predictive “patients-related” factors for chronic pain, such as in the study of Aasvang et al. [39], in order to prevent it, choosing an operative technique with lowest risk for nerve damage in these patients; in case of postsurgical pain, it will be important to select patients who can benefit from the surgical approach proposed, according to the suggestion of an involvement in the onset of chronic groin pain of subjective factors (probably linked to each personality or each pain threshold) that cannot be controlled by surgery.

It is for this hypothesis that we are submitting the patients with chronic pain to a psychological test (e.g. MMPI®-2), to evaluate aspects of their personality and their “attitude” to an effective surgery, before our procedure.

In conclusion, the choice of a complete and definitive therapy for postoperative chronic groin pain after inguinal hernia repair is still controversial.

Based on our experience, we can affirm that a wide anterior–posterior exploration of inguinal region (in our technique through a single high sovrapubic incision) allows us to isolate and resect the three nerves of the region and allows us to remove both mesh and plug (when present). This procedure seems to us (and in literature) the best at the moment we can propose to the patients, with almost 90 % of success.

We have no explication for the cases that even if well treated (like the others) do not achieve the same results.