Bande et al. BMC Surgery (2020) 20:147 https://doi.org/10.1186/s12893-020-00805-9 RESEARCH ARTICLE Open Access Chronic pain after groin hernia repair: pain characteristics and impact on quality of life David Bande1* , Luis Moltó1, Jose Antonio Pereira2 and Antonio Montes1 Abstract Background: Chronic postsurgical pain (CPSP) after hernia repair research has mainly relied on unconfirmed self- reporting. We aimed to describe confirmed CPSP incidence, management, and quality of life (QoL) in a 2-year prospective study. Methods: Multicenter study (GENDOLCAT) of 3890 patients undergoing 4 common surgical procedures in 23 hospitals to develop a risk model for CPSP; 2352 men underwent open hernia repair. Patients with pain were identified by telephone at 1 and 3 months and referred to the hospital 4 months after surgery for a physical examination to confirm CPSP. Three validated tools were used: the Brief Pain Inventory (BPI) for severity, analgesic use, and interference with activities; the SF-12 questionnaire for QoL (validated Spanish version), and the Douleur Neuropathique 4 (DN4). Patients with CPSP were called again at 1 and 2 years. Results: In 1761 patients who underwent hernia repair and were eligible for physical examination for CPSP, the incidence of confirmed pain at 4 months was 13.6% (patient-reported pain, 6.2% at 1 year and 4.0% at 2 years). Neuropathic pain was diagnosed in 38.5% of the CPSP patients at 4 months. The incidences of neuropathic CPSP in patients with mesh or non-mesh repairs were similar (38.6 and 33.3%, respectively). SF-12 physical component scores changed little in all patients, whether or not they developed CPSP. The SF-12 mental component decreased significantly in all patients, but the decrease was clinically significant only in CPSP patients. CPSP interfered with activities (18%), work (15.6%), walking (15%) and mood (10.2%). At 2 years 52.1% of CPSP patients had moderate/ intense pain and 28.2% took analgesics. Conclusion: CPSP affects QoL-related activities, and although it diminishes over the course of 2 years after surgery, many patients continue to have moderate/intense pain and take analgesics. CPSP and neuropathic pain rates seem to be similar after mesh and non-mesh repair. BPI and SF-12 mental component scores detect effects on QoL. Trial registration: ClinicalTrials.gov NCT01510496. Keywords: Chronic pain, Hernia repair, Quality o life * Correspondence: dbande@parcdesalutmar.cat 1 Pain Clínic, Department of Anaesthesiology, Institut Municipal d’Investigació Médica. Parc de Salut Mar, Universitat Autònoma de Barcelona, Passeig Martím 25–29, 08003 Barcelona, Spain Full list of author information is available at the end of the article © The Author(s). 2020 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data. Bande et al. BMC Surgery (2020) 20:147 Page 2 of 11 Background CPSP in 23 hospitals in Catalonia and Valencia between Chronic postsurgical pain (CPSP) is a frequent complica- 2009 and 2010 [1]. The open groin hernia repair cohort tion in the general surgical population [1, 2]. After open included 2352 male patients (code 53.00, 53.05, 53.10, groin hernia repair, a procedure undergone by more than 53.16, 53.17, 53.29, 53.9, International Classification of 20 million patients every year [3], the reported incidence of Diseases, 9th Revision) who were operated under general CPSP ranges widely from 6.9 to 60% [1, 4–6]. The reason or regional anaesthesia or local anaesthesia with sed- for discrepancies is thought to be the differing research de- ation. Women were not enrolled in the hernia group to signs applied, especially regarding diagnostic criteria and rule out sex as a confounding factor in the study of genetic the means of gathering evidence, by postal questionnaires risk, which the GENDOLCAT study explored. Patients [2, 7, 8] or telephone interviews [9, 10], for example, rather were excluded if they were under the age of 18 years, re- than by physical examination as used in some studies [1, 3]. quired reintervention or were scheduled for endoscopic The features and persistence of CPSP and its impact on surgery (no incision), or had a significant mental disorder. quality of life (QoL) have been reported after studies seek- In addition, relatives (parents, grandparents, children, ing to establish risk factors [1–3, 11–13]. Most groups, grandchildren, or siblings) who had already been included however, have not included long-term follow-up of pa- in one of the other surgical groups were excluded, given tients. Nor have they diagnosed or determined the charac- that their inclusion could have skewed the study of gene teristics of CPSP by means of physical examination. The associations that formed part of the wider GENDOLCAT population-based GENDOLCAT study, which gathered aims. The study was approved by the clinical research eth- data on CPSP for 2 years in four surgical scenarios, in- ics committee of the leading centre, Parc de Salut Mar (file cluded a large prospective cohort of 2352 men undergoing reference CEIC-IMAS: 2008/3080/I) and the commitees hernia repair [1]. Designated anaesthesiologists in each of all other centres. Patients signed informed consent centre completed preoperative clinical questionnaires ac- statements for data collection and use and agreed to cording to protocol. A telephone interview to screen for follow-up telephone interviews and an outpatient hospital possible CPSP was done 3 months after surgery, and pa- visit, if necessary, to confirm CPSP by physical examin- tients reporting pain were given a hospital outpatient ap- ation. The study was registered before data collection pointment at 4 months to confirm CPSP. CPSP developed began (ClinicalTrials.gov NCT01510496). in 13.6% after hernia repair and persisted up to 2 years in a sizeable minority. Although no genetic differences were Outcomes and data collection identified in CPSP patients, a risk model based on presurgi- Patients who might have CPSP were identified in two cal clinical variables alone identified 73% of the cases. The preliminary telephone interviews between the first and six predictors were type of surgery, younger age, general third months after surgery. If pain was reported, they physical and mental health status (SF-12), and prior pain at were given appointments for a physical examination and the site of surgery or another area. The study generated ex- clinical interview. CPSP was defined by a modified ver- tensive information about the course of confirmed CPSP, sion of the diagnostic criteria of Macrae and Davies [14]: including the distinction between neuropathic and non- 1) pain developed after a surgical procedure, 2) pain neuropathic pain, but data for specific surgeries was only lasted at least 3 months after surgery, 3) no other causes, partially reported. A detailed understanding of the course such as cancer or chronic infection, could be found to of pain after hernia repair has the potential to inform sur- explain the pain, and 4) absence of the same pain (loca- geons and pain physicians who follow patients with CPSP tion or sensation) before surgery. The main outcomes at as well as researchers interested in exploring the effective- approximately 4 months after groin hernia repair were ness of different management approaches. the characteristics of CPSP and the degree to which pain The aim of the present analysis of the GENDOLCAT at that time interfered with daily living and its effects on data for physician-confirmed diagnoses of CPSP after QoL. We were particularly interested in identifying hernia repair was to include full descriptive information whether or not pain was neuropathic at this time and re- on clinical features and management of pain not re- cording the features and the locations of neuropathic ported earlier, with particular focus on neuropathic pain. and non-neuropathic pain. Secondary outcomes were We discuss pain features in the context of incidence changes in the incidence of reported CPSP up to ap- rates, interference with QoL at 4 months (the main proximately 2 years after surgery and reported ap- GENDOLCAT outcomes), and the course of pain over proaches used to manage pain and their effectiveness. the full 2-year period. Each hospital centre recruited a researcher or research team. One anaesthesiologist from each team was desig- Methods nated to attend training sessions on how to gather data The prospective, multicentre, population-based GEN- before surgery and during hospitalisation, and to diag- DOLCAT study of clinical and genetic risk factors for nose CPSP and neuropathic pain at 4 months. The data Bande et al. BMC Surgery (2020) 20:147 Page 3 of 11 manager (J. Cantillo) conducted all the follow-up tele- unoperated sides were examined. We also asked the pa- phone interviews. (See Online Resource 1 for question- tient to report the use of specific analgesics on a list (see naires and clinical definitions.) Online Resource 1) so that type and combinations were Before surgery, a trained anaesthesiologist administered on record. Patients who reported no pain during the first the validated Spanish version [15] of the Hospital Anxiety and second telephone interviews were sent an SF-12 ques- and Depression Scale (HADS), which has proven useful tionnaire by ordinary post and asked to fill it out and re- for diagnosing or ruling out anxiety or depression in pa- turn it in an envelope provided. Patients whose diagnosis tients without a prior history of psychiatric problems. The of CPSP was confirmed by physical examination were Short Form Health Survey-12 questionnaire (SF-12, Span- called again at approximately 1 year and, if pain had per- ish version 2 [16]) was used to assess the physical and sisted, they were also contacted at approximately 2 years. mental components of QoL. Also recorded at this time During these calls the interviewer filled in a standardised were physical status according to the American Society of questionnaire to evaluate pain intensity, whether the pain Anesthesiologists’ classification; prior pain in the area of was continuous or intermittent, analgesic use, and surgery and pain in other parts of the body expressed on a whether or not the patient had returned to work. The Na- verbal numerical rating scale of 0 to 10 (0 = no pain, 10 = tional Health Service Death Register was checked for exi- the worst imaginable pain) and a verbal categorical pain tus if patients were not reached. scale (no pain or mild, moderate, intense, or unbearable To evaluate the quality of data collection, four authors pain); history of treatment with analgesics; concomitant audited the medical records of a random sample of 5% diseases; and any history of substance addiction to street of the patients from 5 randomly chosen centres. The drugs, alcohol, or smoking. total number of audits was 22. A total of 22 instances of During and after surgery we recorded the following error in a variable or missing data were found, giving an variables: duration of surgery, duration of hospital stay, error rate of 1.2% of the data audited. anaesthetic technique used, whether or not techniques were used to spare nerves in the surgical field (the ilio- Statistical analysis hypogastric and ilioinguinal nerves, and the genital We compiled descriptive statistics for all demographic branch of the genitofemoral nerve), opioid use, and in- and clinical variables. Clinical variables included a finding traoperative complications. Postoperative pain on the of neuropathic pain (DN4), use of postoperative analge- two scales and analgesia used were recorded for 24 h sics, use or non-use of nerve-sparing techniques, BPI re- after wound closure. sults and scores on physical and mental components of The next phase of data collection involved the standar- the SF-12. Continuous variables were presented as mean dised telephone questionnaire (see Online Resource 1). (SD). Categorical variables were presented as number of In the first two interviews at approximately 1 and 3 observations and percentage of the relevant number of months after surgery, the researchers sought to identify cases with available data. SF-12 results at 4 months were patients to ask about continued pain. Those who re- compared with the t test (if paired and normally distrib- ported such pain at the second phone call were given uted) or the Wilcoxon test (if unpaired and non-normally outpatient clinic appointments for an exhaustive physical distributed). The CPSP incidence was calculated for the examination to confirm the diagnosis of CPSP. During population of included patients, after removing early ex- the diagnostic examination, the examiner, who was an clusions (during hospitalization), withdrawals, deaths, and anaesthesiologist expert in pain management, used the patients not located after 2 phone calls. Patients lost dur- following assessment instruments: the Brief Pain Inven- ing telephone screening before the 4-month physical tory (BPI), which records pain severity, analgesic use, examination were counted as having no CPSP. This deci- and interference with daily living, the Spanish SF-12 sion was made in order to avoid overestimating the per- questionnaire, and the Douleur Neuropathique 4 (DN4) centage of chronification. Cases were classified as CPSP inventory to detect neuropathic pain [17]. The BPI rated on the basis of confirmed presence of pain related to sur- pain interference on a scale of 0 to 10 (0 = interfered not gery in the follow-up visit at the patient’s hospital. at all; 10 = interfered completely), and a score of 3 or more was defined as clinically important. A positive re- Results sponse to 4 out of 10 items on the DN4 classified pain Of the 2352 patients recruited, 1761 were located and as neuropathic. As part of the DN4 assessment, the eligible for assessment for CPSP at 4 months, after examiner tested for hypoesthesia (light touch with a cot- 591 losses (25.1%) as shown in the flow chart (Fig. 1). ton swab, pinpricking with Von Frey filaments) and dy- Patient, surgical, and anaesthetic characteristics in this namic allodynia (brushing). The exact location of pain cohort are detailed in Table 1. The presence of CPSP (upper or lower abdomen, scar, groin, thigh, external was confirmed in 239 (13.6%) during the DN4-guided genitals) was also recorded. Both the operated and physical examination at 4 months, excluding 2 Bande et al. BMC Surgery (2020) 20:147 Page 4 of 11 Fig. 1 (See legend on next page.) Bande et al. BMC Surgery (2020) 20:147 Page 5 of 11 (See figure on previous page.) Fig. 1 Flow chart showing patients recruited when scheduled for groin hernia repair, those lost before the telephone interviews, and the group of 239 patients initially diagnosed with CPSP based on physical examination and followed for 2 years. aIn order not to overestimate the frequency of CPSP, incidence rates were calculated on a cohort of 1761 patients we intended to follow: from the 2352 patients recruited, 17 were excluded as having been inappropriately enrolled, 312 were lost before phone calling started at 1 month, an additional 254 could not be reached by phone before the diagnostic examination at 4 months, and 8 deaths had occurred. The timeline shows median (10–90th percentile) times in months when data collection occurred, counting from the day of surgery patients whose pain was caused by another disease; Figure 2 shows the locations of diagnosed CPSP at 4 13.9% of those undergoing mesh repairs (236/1693 months. Pain was most often in the groin (42%) and at patients) developed CPSP versus 4.4% (3/68 patients) the scar (32%). of those repaired without mesh, although the differ- Neuropathic pain was diagnosed in 92 (38.5% of the ence did not reach statistical significance (P = 0.053). 239 of the patients with confirmed CPSP). The differ- Of the 1522 patients who reported no pain in the ence in the rates of neuropathic pain between patients first and second telephone interviews and who were with mesh (38.6%, 91/236) and non-mesh repairs (33.3%, sent the postal questionnaire (SF-12), 471 (30.9%) 1/3) was not significant. Table 2 shows the distribution responded. of signs and symptoms of neuropathic pain. Table 1 Characteristics of the cohort of 1761 patientsa Age, years, mean (SD) 59.01 (14.02) BMI, kg/m2, mean (SD) 26.11 (3.26) ASA physical status, n/N (%) 1. normal healthy patient 543/1761 (30.8) 2. patient with mild systemic disease 1027/1761 (58.3) 3. patient with severe systemic disease 187/1761 (10.6) 4. patient with severe systemic disease that is a constant threat to life 4/1761 (0.2) Anxiety, HADS, n/N (%) 318/1705 (18.7) Depression, HADS, n/N (%) 108/1705 (6.3) Duration of surgery, min, mean (SD) 45.57 (21.90) Meshless hernia repair 68/1755 (3.87) Anaesthetic technique, n/N (%) General 241/1736 (13.9) Combined (general + local/regional) 138/1736 (7.9) Neuroaxial 1296/1736 (74.6) Ilioinguinal, abdominal-genital, or transversus abdominis plane blockade 12/1736 (0.7) Local anaesthetic infiltration 49/1736 (2.8) Endovenous opioids during surgery, n/N (%) 672/1733 (38.8) Complications during surgery, n/N (%) 20/1734 (1.2) Prior analgesic treatments, n/N (%) 397/1752 (22.7) Diagnosed chronic illness, n/N (%) 230/1756 (13.1) Street drug dependence,n/N (%) 29/1755 (1.6) Alcohol dependence, n/N (%) 252/1756 (14.4) Smoking, n/N (%) Smoker 486/1756 (27.7) Ex-smoker 388/1756 (22.1) Non-use of nerve-sparing techniques, n/N (%) 312/1756 (17.8) Hospital stay, days, mean (SD) 0.61 (1.54) a The cohort of patients followed for chronic postsurgical pain after hernia repair, after exclusions and early losses (exitus, missing information before pain screening started, withdrawals) (Fig. 1). Numbers shown in denominators in the table reflect the total number of patients (N) for whom data were available for the variable named Bande et al. BMC Surgery (2020) 20:147 Page 6 of 11 Fig. 2 Locations of diagnosed CPSP at 4 months in 239 patients Table 3 summarises the life-interference effects of pain hernia repair. Although scores on the mental component as shown by changes in the physical and mental compo- decreased significantly from baseline in both groups, the de- nent scores on the SF-12 questionnaire at 4 months for crease was clinically significant (≥ 3 points) only in patients all patients with confirmed CPSP and the 471 patients confirmed to have CPSP. Thirty of the 167 patients with without CPSP who responded to the postal question- CPSP who also fully completed the BPI questionnaire (18%) naire. Physical component scores were similar in pa- reported that pain interfered with their general activities at 4 tients with and without CPSP both before and after months. The reported interferences involved walking (25 [15%]), enjoyment of life (19 [11.4%]), work inside or outside the home (26 [15.6%]), mood (17 [10.2%]), personal relation- Table 2 Neuropathic pain characteristics according to the self- ships (15 [9%]), and sleep (7 [4.2%]. Three of those who had report questionnaire portion of DN4 diagnostic tool not reached the age of retirement (1.3%) had nevertheless Characteristics Patients, n (%)a not yet returned to work 2 years after surgery. Burning, n (%) 25 (27.2) Four months after surgery 32 patients with CPSP Painful sensation of cold, n (%) 11 (6.5) (18.9%) reported taking nonsteroidal anti-inflammatory Electric shocks, n (%) 27 (29.3) drugs or paracetamol, 2 (1.2%) took weak or strong opi- oids, and 5 (3.0%) took adjuvant treatments (anticonvul- Tingling, n (%) 33 (35.9) sant agents or antidepressants) (Table 4). These figures Pins and needles, n (%) 43 (46.7) had changed little 1 and 2 years after surgery. Thirty per- Numbness, n (%) 44 (47.8) cent of these patients taking medication for CPSP felt Itching, n (%) 24 (26.1) their treatments relieved pain adequately. Hypoesthesia to touch, n (%) 42 (45.7) The incidence of CPSP (Table 5) decreased over time Hypoesthesia to prick, n (%) 30 (32.6) from 13.6% at 4 months to 4.0% at 2 years. However, pain intensity remained high (4.2 on the numerical pain Brushing, n (%) 13 (14.1) scale) in patients who still had CPSP at 2 years. Further- a A total of 92 patients with a DN4 score ≥ 4 (positive score on at least 4 items) were diagnosed with neuropathic chronic postsurgical pain. The percentages more, over half of those with pain at 2 years (52.1%) de- for each symptom are of the 92 patients scribed it as moderate or intense. Bande et al. BMC Surgery (2020) 20:147 Page 7 of 11 Table 3 Effect of pain on QOL at 4 months: changes in SF-12 scores, mental and physical components, for patients with and without CPSP CPSP SF-12 Presurgical 4 mo Difference p valuea Mean (SD) Mean (SD) Mean (SD) Yes Physical component 42.81 (9.72) 41.10 (10.68) −1.71 (10.09) 0.266 Mental component 54.00 (8.58) 50.92 (10.80) −3.08 (8.95) 0.028 b No Physical component 48.37 (8.45) 48.39 (8.53) 0.03 (9.27) 0.967 Mental component 55.96 (8.11) 54.22 (9.19) −1.65 (9.34) 0.001 a SF-12 results were compared with the t test for normally distributed paired results when CPSP was present or the Wilcoxon test when CPSP was not present b Although all patients with CPSP completed the SF-12, the postal response rate for non-CPSP patients was only 30.9% Discussion incidence rates of neuropathic pain that has not been di- This prospective population-based study found that agnosed by physical examination. Most of our patients 13.6% of the cohort of 1761 patients had firmly diag- with CPSP reported pain in the groin (42%) and/or scar nosed CPSP at 4 months after groin hernia repair. The (32%), as in another study [21]. However, some also re- incidence of CPSP fell substantially by about two-thirds ported pain at unexpected locations, even ones that bear (to 4.0%) after 2 years. This study also provides exhaust- no apparent relation to the innervation of the surgical ive information on the location and characteristics of field. Nine percent, for example, reported pain in the pain, particularly for the 38.5% of CPSP patients with lower abdomen. These findings underline the import- neuropathic pain. We found that the interference of pain ance of careful physical examination in diagnosing CPSP with QoL could be detected mainly by the mental com- and whether it is neuropathic or not, even when nerve ponent of the SF-12. Finally, even though the incidence damage from surgery is not suspected or a specific dam- of CPSP fell substantially over 2 years, the proportion of aged nerve cannot be identified. Thus, pain detected in patients who continued to take analgesics remained unexpected locations, while there is absence of pain in stable at about a quarter of the CPSP patients. Nonethe- expected ones, does not rule out CPSP, which can de- less, only 30% of those still on analgesics reported they velop not only as the result of evident nerve damage were effective. from surgery but also from an inflammatory response The proportion of CPSP patients we diagnosed with unrelated to neuropathy [11]. Inflammation arises with neuropathic pain after hernia repair was higher than the the nociceptive stimulus of the incision, after which pain 28.7% other authors identified by means of neuropathic may be exacerbated by the sensitisation of peripheral pain descriptors in the short-form McGill Pain Ques- nerves and the central nervous system [22]. tionnaire [18] but lower than the 64% identified as We assessed the interference of pain with QoL with neuropathic based only on the descriptor “aching” in an- two instruments, the SF-12 and the BPI. A decrease of other study [19] and the 55% identified by a list of 3.08 points was detected in the SF-12 mental component neuropathic descriptors that did not form part of a vali- score at 4 months in patients with CPSP, an effect that dated scale in a third study [20]. We attribute these dis- was just over the threshold considered clinically import- crepancies to differences in study design, specifically the ant. The decrease in this measure in patients without instruments used. Few researchers evaluate this type of CPSP, while statistically significant at 1.65 points, was pain using a specific questionnaire that requires physical well below that threshold. However, it is important to examination, such as the DN4. Rather, they rely exclu- remember that the response rate in non-CPSP patients sively on descriptors (such as aching, burning, cutting, was only 30.9%, whereas all patients with CPSP stabbing) associated with neuropathy. Our results for responded to the SF-12. Physical component scores pain location is also relevant for interpreting reported changed little after surgery in all patients, regardless of Table 4 Use of pain medications by patients with CPSP 4 mo N = 169 1 y N = 103 2 y N = 71 Any pain medication, n (%) 42 (24.9) 28 (27.2) 20 (28.2) Anti-inflammatory and/or paracetamol, n (%) 32 (18.9) 23 (22.3) 18 (25.4) Weak opioid without paracetamol, n (%) 2 (1.2) 0 (0) 1 (1.4) Strong opioid, n (%) 0 (0) 1 (1) 1 (1.4) Anticonvulsant and/or antidepressant, n (%) 5 (3.0) 1 (1) 1 (1.4) Other 12 (7.1) 9 (8.7) 4 (5.6) Bande et al. BMC Surgery (2020) 20:147 Page 8 of 11 Table 5 Incidence and intensity of CPSP according to numerical and categorical pain scale results 4 mo 1y 2y CPSP incidence, n (%) 239 (13.6) 107 (6.2) 71 (4.0) Verbal numerical pain scale, mean (SD) 3.9 (2.0) 4 (2.1) 4.2 (2.0) Verbal categorical pain scale, n (%) Mild 128 (53.6) 51 (48.1) 34 (47.9) Moderate 88 (36.8) 39 (35.8) 25 (35.2) Intense/excruciating 23 (9.6) 17 (16.1) 12 (16.9) the presence or absence of diagnosed CPSP. We think rate of analgesic use (2%), but they they did not look at that the presence of a mental, but not a physical, effect how much time had passed since the patients’ opera- on QoL can be attributed to the unexpected nature of tions. It is striking, however, that our review of the lit- long-term pain. In other words, the physical impact of erature on recovery from groin hernia repair found that pain might be relatively minor but the fact that it takes a analgesic use is not systematically reported or analyzed considerable number of patients by surprise exacerbates in detail. The drugs most often taken by our patients the emotional impact. If our interpretation is right, these with CPSP were nonsteroidal anti-inflammatory drugs, results suggest that patients undergoing hernia repair and there was little use of opiods or coadjutants. This procedures should be informed of the possibility of last finding was particularly interesting given the propor- CPSP and given discharge instructions on how and when tion of CPSP patients with neuropathic pain (38.5%). We to seek care if pain persists beyond 3 months. Of the also observed that the percentages of patients with mod- three other studies that used used the SF-12 to assess QoL erate/intense pain (46.4 to 52.1%, depending on the mo- after hernia repair [23–25], one of them [25] also reported ment reported) and those taking analgesics (only 24.9 to that all patients, whether with or without CPSP, had sig- 28.2%) were quite different. Moreover, only 30% of nificantly improved physical component scores, but not treated patients felt their analgesic regimens were effect- mental component scores, after 12 months. Our BPI re- ive. These data suggest that CPSP seems to be under- sults revealed that 18% of CPSP patients found that pain diagnosed and under-treated in routine clinical practice, interfered with daily activities, 15% reporting that walking at least in our mixed urban-rural area of eastern Spain. was affected. One systematic review found that 32% of pa- The incidence of CPSP we detected (13.6% at 4 months) tients reported that CPSP affected daily and leisure activ- was similar to results reported elsewhere [4, 5, 7, 29], ities and/or work; however, only 2 of the 7 studies but much lower than some reports of up to 60% [4–6]. reviewed used a validated instrument (the SF-36) [4]. Such variability can be attributed to diverse causes. The A large number of validated instruments are available first is the very definition of CPSP, twenty-two of which to assess QoL and function: the Activities Assessment have been used in studies on hernia repair alone accord- Scale, Activity Restriction Questionnaire, Carolinas ing to Molegraaf et al,[28] who found that no definition Comfort Scale [26], Core Outcome Measures Index, Da- at all had been made explicit in 39% of the studies nish Hernia Database Questionnaire, Functional Ability reviewed. We used the definition of the International Test, European Registry for Abdominal Wall Hernias Association for the Study of Pain modified by Macrae Quality of Life Instrument, Functional Index Score, and Davies [14], which is the one most often used across Hernia-specific Quality of Life Assessment Instrument, surgical settings. A second reason for variability is that Inguinal Pain Questionnaire [27], McGill Pain Question- many incidence rates are based on data derived only naire, Pain Impact Questionnaire, and various SF ver- from postal or telephone surveys, without subsequent sions. Validated instruments are rarely used, however, physical examination. The lack of an examining physi- according to a recent critical review, which also reported cian’s confirming diagnosis could lead to false positives, that even among studies using them, assessments have explaining higher incidence rates. The third reason for not been recorded both before and after the procedures variability is that retrospective studies in the literature [28]. We suggest that validated questionnaires should be have used different periods of postsurgical follow-up. used systematically by both caregivers and researchers if The CPSP rates associated with mesh (13.8%) and we are to be able to understand the impact of CPSP on non-mesh (4.4%) were dissimilar in our cohort but not QoL in this and other surgical settings. significantly different, although we note that the number Our finding that 24.9% of patients with CPSP were of non-mesh repairs was low (68 cases) and the number taking some type of analgesic 4 months after surgery, of confirmed CPSP cases was fewer than expected (3 ra- and that the proportion had changed little after 2 years, ther than the 9 cases we expected). Still, this observation is noteworthy. Kailliomaki et al.7 reported a much lower of nonsignificance and the similar rates of neuropathic Bande et al. BMC Surgery (2020) 20:147 Page 9 of 11 pain after mesh and non-mesh repair suggest that using screening at 3 months (13.7% of those enrolled) as not a mesh seems not to play a role in neuropathic CPSP. having pain, the CPSP incidence we report may be an Rather, our observations suggest that the patient-related underestimate. If we had simply eliminated these pa- factors that form part of the GENDOLCAT group’s risk tients, the percentage of possible CPSP cases for examin- model (particularly young age, prior pain in the surgical ation would have been 15.9%, not 13.6%. The field or elsewhere, and psychological profile) are the researchers made this decision in the interest of minim- main predictors of both neuropathic and non- izing the number of false positives identified by the neuropathic CPSP after hernia repair, as they are after model and increasing the sensitivity. Our aim in model- other procedures [1]. The rates of CPSP in both mesh ling risk was to provide guidance for planning preventive and non-mesh repairs in this study are consistent with measures or designing trials to confirm their efficacy. We rates reported for other surgical settings in which mesh wished to avoid treating patients who would receive no is not used, such as thoracotomies, breast surgery, and benefit from therapies. Third, given that only about a third abdominal hysterectomies [1, 2]. The relatively low rate of the patients reporting no pain at 3 months returned the of neuropathic pain we observed also suggests that bet- SF-12 questionnaire by post, the results should interpreted ter medical rather than surgical approaches for prevent- cautiously when applying them to patients without diag- ing and treating pain are called for. We believe this is nosed CPSP, whose situation may not be reliably reflected particularly true if we take into consideration that symp- by our data. Fourth, the small number of non-mesh repairs toms tended to resolve for about two-thirds of our pa- in the cohort (68 patients, 3.87% of the total) may be the tients with CPSP (affecting 6.2% after 1 year and 4.0% reason we did not detect significant differenes in CPSP be- after 2 years), possibly attributable to the rarity of struc- tween mesh and non-mesh repairs. Although statistical tural damage to nerves in the surgical field. However, conditions for the analysis were met [33], we would like to while this might initially appear to point to the spontan- see data for a larger number of non-mesh cases before ar- eous resolution or attenuation of pain, we must empha- guing strong conclusions given that the CPSP rates between sise that the percentage of CPSP patients with moderate the two groups were quite different (4.4% vs 13.9%) and or intense pain remained fairly constant (at 46.4% at 4 approached significance. A cohort with a larger number of months to 51.9 and 52.1% at 1 and 2 years, respectively). non-mesh cases might have yielded different results. Finally, This constancy may be explained by the under- we did not do specific neurophysiological studies in either treatment of CPSP we discuss above. Few other studies the CPSP patients at 4 months or in patients without CPSP have analysed CPSP prospectively and long-term [7, 8]. after surgery. Our decision was based on reports that stan- An important strength of this study, which is the largest dardised tests often show persistent postoperative sensory prospective long-term analysis of CPSP after groin hernia re- dysfunction in patients without pain [34, 35]. Moreover, pair thus far, was its reliance on a trained, expert physical material and trained staff were not available in all of the 23 examination to confirm the CPSP diagnosis. Although one hospitals participating in the study. other recent study did include physical examination [21], the authors used a single anaesthetic technique in all operations Conclusions and excluded patients with diabetes, prior neuropathic pain In conclusion, we have provided prospectively gathered or ischaemic disease, limiting generalisability to the general data detailing the clinical features and management of surgical population. A second strength was our representa- CPSP at 4 months in the 13.6% of patients the GENDOL- tive sampling of a previously characterised surgical caseload CAT [1] study identified with this complication of hernia [30], such that the findings can be cautiously generalised to repair surgery. Furthermore, we showed that pain persists natural clinical settings. A final strength was the 2-year in a sizeable proportion (about 4% at 2 years) of patients period of follow-up of patients with confirmed diagnoses, and may be undertreated or ineffectively treated. Our de- which we believe provides a reliable clinical picture of the sign attempted to respond to shortcomings in the literature long-term natural history of CPSP. on CPSP after hernia repair that have emerged as a result One limitation is that the questionnaires we used to of variation in the definition of outcomes and the uncertain identify QoL issues (the BPI and SF-12) were not specific reliability and comparability of tools used for both the diag- to hernia repair. We did not use the Inguinal Pain Ques- nosis and evaluation of CPSP’s impact on QoL. tionnaire [27] or the Carolinas Comfort Scale [31] be- cause our data were extracted from the aforementioned Supplementary information larger study of a wider surgical population [1]. The two Supplementary information accompanies this paper at https://doi.org/10. instruments we chose, however, have been validated in 1186/s12893-020-00805-9. various surgical settings [31, 32] and have been adopted in other studies of CPSP after hernia repair [23–25]. Sec- Additional file 1. Online Resource 1: Data collection, variables, definitionsand telephone questionnaires. ond, by classifying patients unavailable for phone Bande et al. BMC Surgery (2020) 20:147 Page 10 of 11 Abbreviations 7. Kalliomäki ML, Meyerson J, Gunnarsson U, Gordh T, Sandblom G. Long-term CPSP: Chronic postsurgical pain; QoL: Quality of life; HADS: Hospital Anxiety pain after inguinal hernia repair in a population-based cohort; risk factors and Depression Scale; SF-12: The Short Form Health Survey-12 questionnaire; and interference with daily activities. Eur J Pain. 2008;12:214–25. BPI: The Brief Pain Inventory; DN4: Douleur Neuropathique 4; SF-36: The 36- 8. 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