Pain Trajectories in Severe Persistent Inguinal Post-herniorrhaphy Pain

Study Overview
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Brief Summary
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Severe persistent postsurgical pain (PPP) remains a major healthcare challenge. In the third most common surgical procedure in the UK, inguinal herniorrhaphy, including 85,000 surgeries in 2015, an estimated 1,500 to 3,000 patients will annually develop severe PPP. While the trajectory of PPP is generally considered a continuation of the acute post-surgery pain, recent data suggest the condition may develop with a delayed onset. The present study evaluated pain-trajectories in a consecutive cohort referred to a tertiary PPP-center. Explanatory variables based on individual psychometric, sensory and surgical profiles were analysed.

Detailed Description
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Severe persistent post-surgical pain (PPP) is a prevalent medical problem leading to impairment of physical and psycho-social functions in a large number of individuals.Severe PPP may significantly influence 4-8% of the surgical population, depending primarily on the surgical procedure and technique, but also patient-related pre-surgical factors.Updated criteria for PPP have recently been suggested. Inguinal herniorrhaphy qualifies for PPP-research due to a high surgical volume. Paradoxically, while the surgery is considered a minor procedure with limited tissue damage it is carried out in a territory with abundant nerve and vascular supply, and, complex musculoskeletal functions essential for locomotor actions. Persistent pain after inguinal herniorrhaphy may develop after a seemingly successful surgical procedure, and, is seen in a severe form in 2-4% of the patients associated with significant deterioration of the health-related quality of life. The transition process from acute to persistent pain may be more complex than previously assumed, making the study of temporal pain trajectories interesting. Based on clinical experience from a nationwide research center in PPP following inguinal herniorrhaphy, the authors decided first, to perform a prospective exploratory cohort study examining graphical pain charts by planimetrics, attempting to construct a valid statistical sub-classification of the trajectories. Secondly, the relationship between the sub-classification of the trajectories, and, potential explanatory variables, based on individual profiles of pain, psychometrics, quantitative sensory testing, and surgical procedures, were analysed, using principal component analysis and logistic regression models.

Official Title
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Pain Trajectories in Severe Persistent Inguinal Post-herniorrhaphy Pain

Conditions
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Chronic Pain

Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Patients with severe persistent pain (>6 mo) after groin hernia repair referred to our center for PPP Exclusion Criteria: Unable to cooperate with the sensory examinations

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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What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Group I pain trajectories | Trajectories are examined by area-under-curve using normalized pain intensities (numeric rating scale values 0-10 [y-axis]) and normalized time points (years [x-axis]) in patients with sustained severe where the acute post-surgical pain continued into persistent post-surgical pain (PPP) with unchanged high-intensity pain | 2014-2016 | 
| Group II pain trajectories | Trajectories are examined by area-under-curve using normalized pain intensities (numeric rating scale values 0-10 [y-axis]) and normalized time points (years [x-axis]) in patients where the acute post-surgical pain decreased significantly to low-intensity levels, but pain recurred developing into high-intensity PPP | 2014-2016 | 
| Group III pain trajectories | Trajectories are examined by area-under-curve using normalized pain intensities (numeric rating scale values 0-10 [y-axis]) and normalized time points (years [x-axis]) in patients where repeat-surgery precipitated high-intensity PPP | 2014-2016 | 
| Group IV pain trajectories | Trajectories are examined by area-under-curve using normalized pain intensities (numeric rating scale values 0-10 [y-axis]) and normalized time points (years [x-axis]) in patients where pre-surgical high-intensity pain continued unchanged post-surgically. | 2014-2016 | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Pain intensity | Numeric Rating Scale (NRS; 0-10 units) | 2014-2016 | 
| Activity of Daily Living (ADL) score | Activities Assessment Scale (AAS; 8 specified physical activities; 0-8 units each) | 2014-2016 | 
| Assessments of Anxiety and Depression | Hospital Anxiety and Depression Scale (HADS; 14 items scale; 0-21 units) | 2014-2016 | 
| Assessment of Pain Catastrophizing | Pain Catastrophizing Scale (PCS; 13 item scale; 0-65 units) | 2014-2016 | 
| Quantitative sensory testing (QST) | Mechanical and thermal detection and pain thresholds | 2014-2016 | 
| painDETECT | Neuropathic pain questionnaire (15 items scale; 0-38 points; 0-12 points = neuropathic pain unlikely; 13-18 = existence of neuropathic pain cannot unambigously be rejected;19-38 points = neuropathic pain likely) | 2014-2016 | 
| S-LANSS | Neuropathic pain questionnaire (7 items; minimal cumulated score 0 points, maximum cumulated score 24 points; a score of 12 or more suggests pain of predominantly neuropathic origin) | 2014-2016 | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Inguinal Herniorrhaphy, Hernia, Persistent postsurgical pain, Long term follow up, Quantitative sensory testing (QST), Pain trajectory, Explanatory variables