Does Re-surgery Improve Somatosensory Outcomes in Persistent Pain After Groin Hernia Repair

Study Overview
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Brief Summary
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Groin hernia repair is accompanied by persistent severe pain in 2-4% of the patients significantly restraining psychophysical functions. Re-surgery with meshectomy and selective neurectomy may improve the pain condition, compared to non-surgical alternatives. In the current study, the primary objective was to examine and describe the underlying pathophysiological perturbations by quantitative somatosensory testing before and after re-surgery.

Detailed Description
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Persistent severe pain occurring in the aftermath of a surgical procedure is frequently associated with significant impairment of physical and psycho-social functions. After groin hernia repair (GHR), 2-4% of patients develop persistent severe pain. The GHR procedure, previously considered belonging to minor surgeries, qualifies as a rather complex procedure performed in a territory with a high density of nerve fibers, accommodating essential functions for locomotion and reproduction. More than 20 million repairs are performed annually worldwide, and consequently, it is estimated that 400.000-800.000 patients each year will develop persistent severe pain after the groin hernia repair (PSPG). Management of PSPG is medically challenging and may require re-surgery with mesh removal and selective neurectomy. After re-surgery for pain after open primary GHR, a potential pain-relieving effect, as well as an improvement of the deteriorated physical functions, has been demonstrated. Quantitative somatosensory testing (QST) is an investigational psychophysiological tool with the potential to uncover the putative pathophysiological substrate in PSPG, i.e., neuropathic and inflammatory constituents. The method may also be used to quantitate changes induced by the re-surgery. Since re-surgery is a neuroablative procedure, essentially performed in previously damaged tissue, it is of interest to examine the extent of neurological perturbations, i.e., 'loss' and 'gain' of sensory functions and the relation to clinical outcome measures. The authors are only aware of one previous PSPG-study (n = 21) finding that re-surgery, including meshectomy and selective neurectomy, was associated with increased pain pressure thresholds, decreased pain ratings and improved pain-related functional measures. The objectives of the current study, comparing pre with post-re-surgery data, were first to perform a more detailed analysis of the quantitative somatosensory data regarding 'loss' and 'gain' of sensory functions and their relation to clinical outcome measures. Second, to corroborate the clinical outcome findings of the previous study using a threefold larger cohort.

Official Title
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Somatosensory Outcomes Following Re-surgery in Persistent Severe Pain After Groin Hernia Repair

Conditions
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Patients With Persistent Severe Pain After Groin Hernia Repair

Intervention / Treatment
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* Procedure: Re-surgery


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Patients with persistent severe pain (activity-related or maximal pain intensity > 7 NRS-scores [numeric pain rating scale 0-10]) following unilateral, uncomplicated, open groin hernia repair. Exclusion Criteria: All that contradicts the above.

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Intervention/Treatment |
| --- |
|Procedure: Re-surgery|Re-surgery with meshectomy and selective neurectomy|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Thermal thresholds | Warmth detection threshold (WDT), cool detection threshold, heat pain threshold (HPT) and cold pain threshold (CPT) are made by a computerized contact thermode (Thermotest, Somedic AB, Sweden) with an active thermal surface of 12.5 cm^2 (2.5 x 5.0 cm^2). The thresholds are determined from a baseline temperature of 32°C with a ramp rate of + 1°C/s. Cut-offs for heat and cold are 50°C and 5°C, respectively. The assessments are made in triplicate and the mean values are used in the statistical analyses. | 3-6 months | 
| Pressure algometry | Deep-tissue pain sensitivity is assessed using a hand-held pressure algometer with a neoprene-coated tip of area 1.0 cm2 (Somedic AB, Sweden), as previously described. The algometer is applied perpendicularly to the skin with a pressure rate of 30 kPa/s. The study subject is told to report the pressure pain threshold (PPT) by activating the button device when pain is perceived. The cut-off limit is 350 kPa. Testing is done in triplicate and the average value is used in the statistical analyses. | 3-6 months | 
| Suprathreshold heat stimulation | A short tonic heat stimulus (heating area 12.5 cm^2; ramp rate: 1°C/s, plateau: 47°C, 5 s; STH) is delivered in order to evaluate the suprathreshold heat pain perception (NRS). | 3-6 months | 
| Temporal summation | Temporal summation test, i.e., the perception in response to repetitive (0.3 to 3 Hz) mechanical stimulation [i.e., wind-up like pain: WUP], indicates presence of central sensitization. The repetitive 1 Hz stimuli for 60 s are either dynamically delivered by a brush or statically delivered by a polyamide filament (one nominal rank below TPT). The study subjects are told to report the level of pain (NRS) every 15 s-1 during the stimulation. Signs of aftersensations are followed 60 s after discontinuation of the stimulation, and the intensity of discomfort or pain is rated by NRS. | 3-6 months | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Activity Assessment Scale (AAS) | Changes in AAS scores before and thre-six months after operation | 3-6 months | 
| Pain intensity scores (NRS) | Changes in pain intensity scores (NRS) at rest, on average and maximally before and thre-six months after operation | 3-6 months | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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groin hernia repair, chronic post-surgical pain, pain thresholds, patient reported outcome measures, reoperation, sensory thresholds