Chronic pain after inguinal herniorrhaphy is not rare, but the reported frequency of pain varies from 0% to 37%. ^1–7 However, the extent to which chronic pain impairs function has not been well described. The development of chronic pain after inguinal herniorrhaphy has been attributed to several mechanisms, including damage to well-defined sensory nerves (ilioinguinal, iliohypogastric, and genitofemoral) ⁸ and “mesh inguinodynia.”⁹ Several factors have been proposed as predictors of chronic pain, including surgery for a recurrent hernia, ¹⁰ intensity of early postoperative pain, ^3,10 insurance status of the patient, ¹¹ degree of specialization and experience of the surgeon, ¹² and the type of surgical procedure used. Liem et al ² found a lower incidence of pain after a laparoscopic hernia repair (2%) than an open nonmesh repair (14%). Dirksen et al ⁴ found no difference in the development of chronic pain after a Bassini repair (12%) versus a laparoscopic repair (15%). Hay et al, ⁶ in a large multicenter trial including 1,578 patients, found an overall pain incidence of 7%, with no significant differences among the different types of nonmesh, open hernia repairs. Rutkow and Robbins, ¹³ in contrast, found a chronic pain incidence of 0% in their case series of recurrent hernias, using a tension-free mesh repair. None of these studies of surgical technique had chronic pain as a primary outcome parameter, and the definitions of chronic pain were inconsistent. A large-scale multicenter study addressing postherniorrhaphy pain found moderate to severe pain in 12% of patients. ³ However, this study is difficult to interpret because approximately 62% of the participating patients were excluded or lost to follow-up. Because patient selection and participation in clinical trials may influence the long-term outcome, the frequency of chronic pain after inguinal herniorrhaphy in the general population is unknown. The low recurrence rates associated with the use of mesh repair may shift focus from recurrence to other outcome parameters. Further, all frequent and negative consequences of surgery should be considered when discussing the indication for surgery with the patient. We have therefore attempted to establish the frequency and significance of pain after inguinal herniorrhaphy in a nationwide population.

After receiving approval from the appropriate ethics committees and the oversight board of the Danish Hernia Database, a questionnaire study was carried out. Because of the rules regulating the use of the database, contact with patients was required to be on the basis of a registration in the Danish National Hospital Administrative System. Information in the two registers was linked by the use of unique Social Security numbers. Inclusion criteria included concurrent registration in the database and the hospital administration system, age older than 18, and surgical repair of an inguinal or femoral hernia between February 1, 1998, and March 31, 1998. Patients who underwent surgery for simultaneous bilateral hernias were excluded, as were patients who in the observation period had a subsequent hernia repair. A screening questionnaire (Table 1) was sent by mail to all patients precisely 1 year after surgery. Patients were asked whether they believed they had a recurrence of their hernia or had experienced pain during the past month. Patients who said they had groin pain received a second, more detailed questionnaire (Table 2) asking about the pain and its effect on the person’s function.

Table 1. QUESTIONNAIRE 1

Table 2. QUESTIONNAIRE 2

The setup and organization of the database has been reported elsewhere. ¹⁴ In brief, a one-page form is filled out by the operating surgeon immediately after surgery and sent to a central database secretariat, where the subsequent data processing is carried out. Currently, more than 95% of inguinal herniorrhaphies performed in Denmark (approximately 10,000/year) are reported to the database. The following information was abstracted from the database: whether the repair was for a primary or a recurrent hernia, the type of repair, the type of anesthesia used, the type of hernia found, and the age and sex of the patient. Data from the returned questionnaires, together with data from the database, were analyzed using SAS version 6.12 software (SAS Institute, Inc., Cary, NC). Data are presented, where appropriate, with 95% confidence intervals, considering the study cohort as a sample from a conceptual population of all herniorrhaphy patients in Denmark. Overlapping confidence intervals are seen as no significant difference between the groups compared.

In the 2-month period between February 1, 1998, and March 31, 1998, 1,652 patients were registered in the database as having undergone surgery for an inguinal or femoral hernia, and 1,443 questionnaires were mailed. Reasons for not receiving questionnaire 1 are detailed in Table 3.

Table 3. DANISH NATIONAL HERNIA DATABASE STATISTICS AND REASONS FOR EXCLUSION OF PATIENTS

Questionnaire 1 was returned by 1,166 patients for a response rate of 80.8%. Three hundred thirty-five patients (28.7%) reported having pain in the area of the hernia within the past month and 128 (11.0%) reported that the pain impaired their work or leisure activities, but only 53 (4.5%) had sought or received medical treatment for this pain. A suspicion of recurrence of the hernia was reported by 79 patients (6.8%); another 148 (12.7%) were unsure of a recurrence. Approximately half the patients reporting recurrence also reported pain; less than one third of patients without self-reported recurrence reported pain. The incidences of pain and impairment, stratified by gender, primary versus recurrent hernia repair, type of repair, type of anesthesia, and surgical findings, are shown in Table 4. There was no relation between the risk of chronic pain and the choice of anesthetic method or type of surgical repair.

Table 4. DEMOGRAPHICS AND SURGICAL FACTORS

Questionnaire 2 was mailed to the 335 respondents of the first questionnaire who reported having pain where the hernia was situated, and 278 responses were received (83.0% response rate). Temporal and activity-related aspects of the pain are summarized in Table 5. Pain was more commonly reported with activity than at rest (85.6% vs. 50.7%). Moderate to severe pain was also much more commonly reported with activity (32.7% vs. 14.4%). Impairment of one or more daily life activities as a result of pain was reported by 194 (69.8%) patients responding to questionnaire 2 (corresponding to 16.6% of the 1,166 patients), when they were questioned about eight specific activities. The activities most frequently associated with pain were “standing for more than half an hour” (32.0%) and “climbing stairs” (27.7%). The location or locations of the pain were determined from the pain diagram completed by the patient. Pain in the groin (defined as pain above the inguinal ligament, lateral to a small area over the pubic tubercle and not related to the genital area) was the most frequent single location (n = 122; 43.9%) and was present in 245 patients (88.1%) when combined with other locations. Isolated pain over the pubic tubercle, in the leg, or in the genitalia was present in only nine patients. The pain descriptors used by the patients are listed in Table 6. The most frequent pain descriptor used was “tender” (42.1%); “shooting” was used by 28.8% of the patients and “pricking” by 25.2%. One or more neuropathic pain descriptors (sharp, shooting, pricking, or burning) ¹⁵ were used by 59.4% of the patients. Affective pain descriptors were used less frequently than sensory descriptors; “irritating” (irriterende in Danish, which connotes “annoying” to a greater extent than “inflamed”) was the most frequently used affective term.

Table 5. FREQUENCY AND INTENSITY OF PAIN AND THE RELATION TO PHYSICAL ACTIVITY

Table 6. PAIN DESCRIPTORS

All surgeons know that chronic pain may occur after inguinal herniorrhaphy, but the exact prevalence, cause, duration, and social consequences have not been well described. To our knowledge, this is the first nationwide survey that describes the frequency of the problem and the consequences to individual function. The literature shows a highly variable incidence of chronic pain, ranging from 0% to 37% in individual or multicenter studies. ^1–7 These reports are predominantly from public hospitals and university institutions and are in contrast with results from dedicated hernia centers, where the incidence of chronic postherniorrhaphy pain is 0% to 2%. ^13,16,17 However, assessing chronic pain was not the primary aim of most of the available studies. Detailed descriptions of the pain pattern and social consequences from large studies are rare, except for two multicenter studies. ^3,5 In these studies, where the follow-up rate was approximately 32%³ and approximately 70%, ⁵ an incidence of moderate to severe pain was found in approximately 10%. In Gillion and Fagniez’s study, ⁵ 5% of the patients assessed their discomfort as more troublesome than the hernia they had before. Based on these and other outcome data, ¹⁸ it has been suggested that data other than recurrence rate should be considered in the overall assessment of the outcome after inguinal herniorrhaphy.

Predictive factors of chronic postherniorrhaphy pain are not well established, although it may be related to the intensity of pain in the early postoperative period ^3,10 and late sensory disturbances. ^3,5 In accordance with the lower pain intensity in elderly patients in the early postoperative period, ¹⁰ the results of the present study also found less chronic pain in elderly patients. The existing literature is inconsistent in explaining the relation between a specific surgical procedure and the risk of chronic postherniorrhaphy pain, ^1–6,13 although in some studies there may be a tendency toward less chronic pain after laparoscopic herniorrhaphy. ^2,7 In our large-scale study, we found no relation between chronic pain and the type of hernia repair, however, the relatively small number of laparoscopic procedures performed precludes final conclusions as to the potential benefits of this type of herniorrhaphy.

The cause of chronic postherniorrhaphy pain is probably associated with nerve damage to one or more of the three nerves passing through the surgical field. This is supported by the association between sensory disturbances and chronic pain. ^3,5 The correlation between the intensity of early postherniorrhaphy pain and the risk of chronic pain ¹⁰ leads us to hypothesize that nerve compression or injury may be a pathogenic risk factor for both acute and chronic pain. However, hernia surgeons have recommended that nerve ends should be ligated ¹⁹ or intentionally severed ²⁰ to reduce the risk of chronic pain, but with no documentation regarding the outcome of these recommendations. Nevertheless, the pain characteristics found in our study, combined with the relation between early pain intensity and sensory disturbances, suggest that pain from nerve damage is a concern.

Our findings of a relatively low use of affective words (“tiring/exhausting,” 8.6%; “sickening,” 2.2%) in patients with chronic postherniorrhaphy pain differs from what is usually reported in patients with chronic pain but is similar to what is reported for acute pain. ²¹ Of patients with low back pain or musculoskeletal pain seen in pain clinics, 30% to 50% use the terms “tiring/exhausting” or “sickening” as descriptors. ²² This may represent selection bias in studies based in pain clinics or, less likely, a difference between patients with chronic postherniorrhaphy pain versus patients with other chronic pain problems.

The present study represents the largest study to date of chronic postherniorrhaphy pain, with a high follow-up rate (> 80%), and it is the only large-scale epidemiologic study from a nationwide population. Eleven percent to 17% of the patients reported that pain interfered with their work or leisure activity, underscoring the importance of this problem. This is emphasized by the data for participation in usual sports activities, where 25% of respondents with pain reported impairment and another 25% reported no impairment. However, the remaining 50% responded that they no longer participated in this activity or did not answer the question. The finding that more than 5% of all patients undergoing inguinal herniorrhaphy report difficulty with standing for 30 minutes or more (or inability to do so) because of pain at the site of hernia to us indicates significant functional impairment.

Our reported incidences of chronic pain may have been slightly overestimated if the nonresponders had less pain than responders. However, pain limiting social activities would still be in the range of 9% to 11%, even assuming that all nonresponders did not have any pain.

In summary, our nationwide, large-scale study in unselected patients undergoing inguinal herniorrhaphy documents a high incidence of chronic pain leading to various types of social disability in 11% to 17% of patients. We believe that potential pain and impairment need to be considered and discussed before deciding to proceed with herniorrhaphy. The results of our study and those of others ^3,5 suggest that a significant proportion of the pain is of neuropathic origin. Future studies should focus on a detailed description of the surgical technique (e.g., nerve identification, transsection, repair technique) and a detailed postoperative follow-up with characterization of the pain (stimulus-independent vs. -dependent pain). Only by such careful studies and assessment of the causes of pain can rational prevention and management techniques be developed. ²³

Surgical departments of Kjellerup Sygehus, Brovst Sygehus, Broerup Sygehus, Dronninglund Sygehus, Tarm Sygehus, Centralsygehuset i Esbjerg, Farsoe Sygehus, Fredericia Sygehus, Frederikshavn-Skagen Sygehus, Frederikssund Sygehus, Sygehus Fyn Faaborg, d KAS Gentofte, d KAS Glostrup, Grenae Sygehus, Grindsted Sygehus, Haderslev Sygehus, Sygehuset Oeresund Hoersholm, d KAS Herlev, Herning Centralsygehus, Hilleroed Sygehus, Hobro/Terndrup Sygehus, Centralsygehuset i Holbaek, Nykoebing Sjaelland Sygehus, Centralsygehust i Holstebro, Horsens/Braedstrup Sygehus, HS Hvidovre Hospital, Kalundborg Sygehus, k Bispebjerg Hospital, Amager Hospital, Koege Amtssygehus, Lemvig Sygehus, Sygehus Fyn Middelfart, Nykoebing Mors Sygehus, Amtssygehuset i Stege, Amtssygehuset i Nakskov, Sygehus Fyn Nyborg, Centralsygehuset i Nykoebing Falster, Odder Centralsygehus, k Randers Centralsygehus, Ringkoebing Sygehus, Ringsted Sygehus, Roskilde Amtssygehus, Bornholms Centralsygehus, Centralsygehuset i Silkeborg, Skive Sygehus, k Sygehus Fyn Svendborg, k Soenderborg Sygehus, Thisted Sygehus, Toender Sygehus, k Vejle Sygehus, Viborg Sygehus, Aabenrae Sygehus, Aalborg Sygehus, l Aarhus Kommunehospital, c HS Rigshospitalet, Kolding Sygehus, Hjoerring/Broenderslev Sygehus, Centralsygehuset i Naestved, l Aarhus Amtssygehus, Privathospitalet Hamlet, Saeby Sygehus, Samsoe Sygehus, a Odense Universitetshospital; and the following at private outpatient clinics: Nis Alstrup, Marianne Schroeder, Hans-Eric Jensen, Finn Heidemann Andersen, Elisabeth Rubinstein, Per Bech-Jansen, Jes Henrik Steen, Peter Michael Joergensen, Erik Secher-Hansen, Annet Aasted, Walter Schradieck, Jens Schoubye, Carsten Hansen, Günther Roepke, John Stagsted Soerensen, Lars Bjoern Rasmussen, Bjarne Jensen, Kaare Nielsen.