Approximately 8% of all inguinal hernia repairs recorded in Sweden are performed in women [1]. However, because the global volume of inguinal hernia repair is high, women undergoing repair represent a large group of patients.
To the best of the authors of this work, there are no randomized controlled trials focused on inguinal hernia repair in women. Guidelines recommend timely repair of all female groin hernias, in contrast to the watchful waiting strategy recommended for asymptomatic or minimally symptomatic male inguinal hernias [2].
Chronic pain has become the most important area of improvement in inguinal hernia surgery, and the incidence varies greatly in the literature, between 0.7% and 75% [2,3], mostly due to the use of different definitions [4].
To define clinically significant levels of discomfort, the guidelines suggest that the cut-off point should be “moderate bothersome pain that affects daily activities,” which would mean that approximately 10% to 12% of all operated patients suffer from chronic pain. postoperative [2].
Review articles [5,6], have previously established that female sex is a strong risk factor for chronic postoperative pain. However, studies evaluating chronic pain after inguinal hernia surgery in women, compared to men, are small or show statistically insignificant differences [7-11].
The aim of this study was to evaluate chronic pain after inguinal hernia surgery in women, using a large unselected cohort of 4021 women, from the Swedish National Register . We hypothesized that the rate of chronic postoperative pain after inguinal hernia repair is higher in women than in men.
| Methods |
This was an observational cohort study based on a national hernia registry, combined with a patient-based outcome measurement (PROM) questionnaire. The STROBE [12], Good Clinical Practice, and the WMA Declaration of Helsinki [13] guidelines were followed.
Approval for the study was obtained from the Swedish Ethical Review Authority , DNR: 2019-00041. This study was registered at http://clinicaltrials.gov, after having completed the primary data, but before beginning the analysis, since observational studies are not subject to pre-registration at the time of their initiation (NCT04228536).
The Swedish Hernia Register (SHR) is a national quality registry that covers approximately 97% of all hernia repairs performed in Sweden. It is a national population-based registry and, consequently, patients, surgeons and units are not selected.
All variables are prospectively recorded online at the time of surgery, and include: details on hernia anatomy, method of repair, body mass index (BMI), and American Society of Anesthesiologists (ASA) classification [14].
Preoperative pain scores are not recorded. Each citizen of Sweden has a unique personal identification number, making it possible to follow-up patients over time, regardless of whether they had their primary or recurrence operation in Sweden [14]. Patients are followed until reoperation of the hernia on the same side, emigration, or death.
> Questionnaire
To evaluate postoperative pain 1 year after primary repair, all patients included in the SHR between September 1, 2012 and August 30, 2017, received a shortened version of the previously validated Inguinal Pain Questionnaire (IPQ) [ 16]. They were asked the worst degree of pain they had felt in the operated groin during the previous week.
The seven grades were:
1 , no pain;
2 , pain present but easily ignored;
3 , present pain that cannot be ignored;
4 , present pain that cannot be ignored and that interferes with concentration on daily activities;
5 , pain present that interferes with most activities;
6 , pain present requiring bed rest; and
7 , present pain for which prompt medical attention is requested.
Scores of 1 to 3 were defined as no pain, and scores of 4 to 7 as significant postoperative chronic pain. The cut-off point was chosen in accordance with the guideline recommendations, defining chronic postoperative pain as a level of discomfort evaluated by the patient as moderate and impacting daily activities [2].
To measure patient satisfaction 1 year after surgery, patients were asked:
Are you satisfied with the result of your inguinal hernia operation?
The grades were:
1 , yes, completely;
2 , yes, mostly;
3 , mostly not; and
4 , completely not.
Scores 1 and 2 were defined as satisfactory.
| Definitions |
Chronic pain was defined as pain affecting daily activities with a duration > 3 months [17]. Emergency operation was defined as surgery within 24 hours of admission due to symptoms of incarcerated hernia. Reoperation due to recurrence was defined as a new operation performed on a groin previously operated on during the study period.
Hernia anatomy was defined as indirect (lateral), direct (medial), femoral (crural), or combined hernia (indirect and direct). A hernia combined with a femoral component was considered a femoral hernia.
The surgical repair method was divided into the following groups: open anterior mesh, totally extraperitoneal endoscopic (TEP), transabdominal preperitoneal endoscopic (TAPP), combined technique anterior and posterior, open technique with preperitoneal mesh, or suture repair.
> Patients
• Inclusion criteria
All patients 15 years of age or older who were included in the SHR with a primary unilateral inguinal hernia. Both elective and emergency surgeries were included.
• Exclusion criteria
Patients who did not respond to the questionnaire, patients with an unspecified or absent method of operation, patients who died within 1 year after surgery, patients who emigrated or whose address was lost after 1 year of follow-up by questionnaire, patients who had another operation on the side. contralateral during the study period.
> Data collection
All patients included in the SHR between September 1, 2012 and August 31, 2017 were identified. The abbreviated IPQ form was sent by regular mail to all registered patients 1 year after surgery.
Patients could answer the questionnaire on paper or online. If a response was not received within a month, a reminder was sent. Reoperation due to recurrence was analyzed until December 31, 2018, if there was no death or reoperation before, in which case, follow-up was done until the date of death or reoperation.
> Other measurements
• Primary end goal
The primary endpoint was chronic pain 1 year after inguinal hernia surgery.
• Secondary final objectives
Secondary endpoints were risk factors for chronic pain, reoperation for recurrence, and patient satisfaction after surgery for inguinal hernia in women.
> Statistics
Differences in results were tested using the t test for continuous variables, and the Chi-square test for dichotomous variables. Multivariate logistic regression analysis was used to calculate the odds ratio (OR) for chronic pain in women, with men as a control group.
Adjustments were made for age (dichotomized as above/below median), hernia anatomy, repair method, emergency or elective surgery, low-volume surgeon (≤5 repairs/year), ASA classification ≥ 3, and BMI (dichotomized as above/below the median). Statistical significance was established at P < 0.05.
Patients with missing data for any of these variables were excluded from the multivariate analysis.
| Results |
A total of 59,396 patients met the inclusion criteria. With a response rate to the IPQ of 70%, 4021 women and 37,542 men in the control group were available for analysis.
The most common method of operation in women was TEP; in men, open placement of mesh via the anterior approach. A femoral hernia was found in 24.7% of female patients, and only 0.7% of male patients.
A woman was 3.7 times more likely to have emergency surgery than a man. Among women who had emergency surgery, 18.1% had a laparoscopic repair (TEP or TAPP), versus 61.5% in elective surgeries. Men were more satisfied with their inguinal hernia surgery than women.
According to the authors’ definition, 18.4% of women and 15.2% of men reported chronic pain (IPQ ≥ 4) 1 year after surgery, with 12.8% of women and 10.5% of men having pain that interfered with most activities, or the worst pain (IPQ ≥ 5).
Multivariable logistic regression analysis for all operations in the cohort showed a significantly higher risk for chronic pain (IPQ ≥ 4) in women compared to men. The difference between the sexes remained when the lowest and highest pain scores were analyzed.
Among women reporting chronic pain, univariate analysis showed an over-representation of emergency repairs ( P = 0.04), an ASA classification ≥ 3 ( P < 0.001), and a higher BMI ( P = 0.001). 03).
If the patient was reoperated for a recurrence, 41.4% ( P < 0.001) reported chronic pain 1 year after primary repair. Not surprisingly, among women reporting chronic pain, the satisfaction rate after inguinal hernia surgery (75%) was significantly lower than among those patients without chronic pain (95.7%; P < 0.001); therefore, chronic pain affects patient satisfaction.
Multivariate analysis showed no significant differences when repair methods and chronic pain were compared, but there was a trend toward less pain after the TEP procedure; however, the sample size was insufficient to be significant. The significant risk factors found were: femoral hernia, BMI above average, and ASA classification ≥ 3. In contrast to men, younger age and emergency surgery were not significant risk factors in women.
The reoperation rate for recurrence was 1.4% for women and 1.8% for men ( P = 0.07), with a median follow-up of 1365 days for women (interquartile range [IQR ]: 982-1783 days), and 1395 days for men (IQR: 950-1838). 50% of women and 31.7% of men who were subsequently reoperated for recurrence had their reoperation within 1 year after primary surgery.
| Discussion |
In this large cohort of unselected patients with data on chronic pain 1 year after surgery for an inguinal hernia, women were 30% more likely than men to have chronic pain. Risk factors for chronic pain included a high ASA classification, a high BMI, and the presence of a femoral hernia.
Guidelines [2] and reviews [5,6] have previously stated that female sex is a strong risk factor for chronic postoperative pain. However, most of the original studies are too small to show a statistically significant difference between the sexes in terms of chronic pain. For example, Kalliomaki et al. [7], had 7 women, Liedm et al. [8], 48 women, Franneby et al. [9], 157 women, and Reinpold et al. [11], 85 women. Those sample sizes are too small to detect 5% differences in absolute numbers.
Dahlstrand et al. [10], analyzed a cohort of 1046 women and 406 men operated on for a femoral hernia. That study was adequately powered and conducted, to a large extent, in a similar manner to the present study.
A major difference is that long-term follow-up was carried out with a minimum of 18 months and a maximum of approximately 11 years. Since chronic pain apparently decreases over time [18], this may have contributed to the relatively low proportion of patients presenting with pain that interfered with daily activities in Dahlstrand’s study (5.5%). Therefore, this lack of statistical significance could be due to the low number of cases in that study.
To the best of our knowledge, the only previous studies that showed a significant difference between men and women in relation to chronic pain after inguinal hernia surgery were those by Bay-Nielsen et al. [19], and Andresen et al.[20].
Bay-Nielsen reported high rates of chronic pain, but used a broad definition where patients were asked, 1 year after surgery: “Have you had any pain within the last month, in the area where you were located?” the inguinal hernia before the operation.” That could be the equivalent of an IPQ score ≥ 2 in the present study. Ninety-three women and 1073 men were included; 37.6% of women reported chronic pain, versus 28.0% of men ( P = 0.048).
No adjustment was made for covariates, which could have influenced the results, given that both the indication and the results are different in men and women. Andresen et al., included 223 women and 1198 men after hernia surgery using TAPP procedure, and found that male sex was a protective factor for chronic postoperative pain, with an OR of 0.47 (95% interval). confidence: 0.29-0.74).
In that study, the follow-up time varied considerably, ranging from 12 to 62 months. It may be inappropriate to draw general conclusions about all types of inguinal hernia surgery based on studies that include only 1 repair method.
This study presents compelling evidence that more women than men suffer chronic pain after inguinal hernia surgery. These data cannot present any reason for that difference. Unmeasured confounding factors, such as preoperative pain, nerve resections, or heterogeneity in the compared groups due to different indications for inguinal hernia surgery in men and women, may have contributed.
Epidemiological studies on sex and pain show that, at the population level, women have a higher prevalence of pain than men [21]. The underlying mechanisms for this are not clear, but it has been suggested that it may be an interaction of biological, psychological, and sociocultural factors [22].
The risk factors identified in this study for chronic pain in women were high BMI, high ASA classification, and femoral hernia.
These risk factors are not widely recognized [6], but Köckerling et al. [23] found similar results in women, in relation to BMI and ASA classification. That study was performed on patients registered in the Herniamed Registry , which is a voluntary registry, mostly including centers with a special interest in hernia surgery [24]. Likewise, emergency surgery was excluded. However, the results related to risk factors were the same, supporting the results of the present study.
A high BMI was also found to be a risk factor for chronic pain in the study by Massaron et al. [25] (1440 operations, 111 women), and in a study by Niebuhr et al. [26], on 20,004 male patients, after TAPP surgery.
When operating methods were compared in women, there was a trend toward less pain after a PET procedure, although not statistically significant. Multivariate analysis did not show emergency hernia surgery to be a significant risk factor for chronic pain in women. Although young age is generally considered a strong risk factor for chronic pain [2], the results in this study on women do not support that.
With 58 cases of reoperation for recurrence in women in this material, the recurrence rates were very low to compare with the operation methods. Women appear to develop recurrence earlier than men, presumably due to a femoral hernia missed at primary surgery [27].
This study sheds light on chronic pain among women operated on for groin hernia. For some reason, there are very few studies on this large group of patients. Postoperative pain assessment has increasingly become an important marker of quality since the introduction of mesh techniques and the subsequent decrease in recurrence rates.
Chronic pain after hernia repair is common, and an in-depth understanding of the factors that increase chronic pain will improve management strategies and therefore quality of life for many patients operated on for a groin hernia [ 28].
The most effective way to prevent chronic pain after hernia repair is to not perform any surgery. Current guidelines recommend timely hernia repair for all female inguinal hernias, due to the high frequency of femoral hernias and subsequent risk of incarceration.
Dahlstrand et al. concluded that the potential to prevent emergency surgery for a femoral hernia is limited, given that most femoral hernias are not known prior to incarceration. Only 10.9% were on a waiting list for surgery, before incarceration [29].
The high rate of chronic pain seen in this study, and the fact that emergency surgery does not increase the risk of chronic pain in women, warrants a discussion about whether women with a minimally symptomatic or asymptomatic inguinal hernia should be recommended surgery. or attentive waiting. More research is needed on management strategies in female groin hernia. Is watchful waiting safe in minimally symptomatic and asymptomatic women?
The strengths of the present study are that virtually all adult women operated on for a groin hernia in Sweden are included in the SHR. Patients, surgeons, and units were not selected, while most other registries, excluding the Danish Hernia Database [30], consist of specialized hernia centers and high-volume surgeons [24,31].
The large population in this study allows for a multivariable analysis with sufficient statistical power to detect clinically significant differences. Likewise, population coverage allows generalization of conclusions related to the absolute number of possible patients experiencing chronic postoperative pain.
The weakness of this study is the absence of preoperative pain scores, and that the data were not verified by clinical examination at the 1-year follow-up.
In a previous study, the authors analyzed lack of follow-up, where non-responders were found to have lower pain scores than responders. A test-retest reliability test showed a k value of 0.58. In future studies it is imperative to include preoperative pain, as it is known to be a risk factor for postoperative pain [18]. It is difficult to compare this study with previous ones, because of the different definitions of chronic pain, and the lack of a uniform measurement tool [18].
The abbreviated version of the IPQ used in this study has been previously validated by Fränneby et al. They concluded that “although the IPQ is not able to distinguish post-repair pain from inguinal pain of other etiology, it is still sensitive enough to detect pain caused by inguinal hernia surgery in a large population, without confounding with all other causes of groin pain” [16].
In the present study, 6.1% of women reported that, during the last week, they experienced pain with a severity of IPQ grade 7 (present pain for which prompt medical attention is requested).
The authors have no further information on what type of medical advice was sought. When comparing different evaluation scales for chronic pain after inguinal hernia repair, Molegraaf et al. concluded that the IPQ or the Carolina Comfort Scale were the most appropriate tools, due to their ease of use and the incorporation of both the pain intensity and quality of life [4].
Conclusions
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