Surgical management of chronic inguinal pain syndromes - Liespijn

at the outpatient department as well (visit 2). Cross-over from the neurectomy to thenerve block group does not seem beneficial and is not included in the protocol.All patients receive a questionnaire by mail 3 and 6 months postoperatively. One yearpost-intervention, all participants are invited for final questionnaire assessment and aphysical examination at the surgical outpatient department (visit 3). Each patient willcomplete a Surgical Pain Scales 14 , McGill Pain Questionnaire - Dutch Language Version 15 ,SF-36 version II quality of life questionnaire at each follow-up moment 16 . At the outpatientdepartment visits (baseline, after 2 weeks, 12 months) the LANNS Pain scale, theLeeds Assessment of neuropathic pain and symptoms and signs, is completed 17 .Complications and change in employment status is noted at each post-interventionevaluation moment.Study endpointsThe primary endpoint is number of successfully treated patients with respect to painreduction. Successful pain reduction is defined as a >50% pain reduction during restingconditions measured with the Surgical Pain Scales after 6 months. In case of necessityto cross-over from the nerve block group to the neurectomy group or if additionaltreatment like chronic pain medication remains necessary, this is considered a treatmentfailure.Secondary endpoints are quality of life (SF-36 version II), alterations in inguinal neurophysiologicalstatus (LANNS pain scale), complications (self-constructed questionnaire),and change in employment status (self-constructed questionnaire).Sample sizeA successful intervention is defined as a 50% reduction (Visual Analogue Scale) in restpain (Surgical Pain Scales) after 6 months of follow-up. After a thorough study of theavailable literature, success rates of a nerve block appeared unknown. After a consultationof several of our anaesthesiologists specialized in the treatment of chronic pain, thesuccess rate of a nerve block is set at 25%. Based on retrospective cohort studies, thesuccess percentage following a surgical neurectomy approximates 75%. Using a type Ierror of 0.05 and type II error of 0.10, a sample size is calculated of 54 patients (2 groupsof 27 patients).Statistical analysisIntention-to-treat analysis will be applied on the primary endpoint pain reduction. Sincewe expect a significant cross-over from the nerve block group towards the neurectomygroup, an ‘as treated analysis’ will be made as well. Endpoints will be analyzed per groupand at each evaluation time. Chi/square test is used for comparison of categoricalvariables. Quantitative variables will compared by Mann-Whitney U test. Results willbe considered significant if P≤ 0.05.DISCUSSIONIn recent years, a number of studies has stressed the importance of chronic pain as animportant complication after inguinal hernia repair 1-4 . However, to date only a fewstudies on treatment options such as operative neurectomy or therapeutic nerve blockshave been published. There is a definite need for more evidence-based treatment regimesin these populations. The present trial will be the first randomized study comparingtwo frequently used treatment modalities for chronic neuralgia after inguinal herniarepair.Populations with postherniorrhaphy pain syndromes are notoriously heterogeneous.Therefore, only patients with presumed peripheral inguinal nerve entrapment areincluded. In contrast, individuals with non-neuropathic pain (‘nociceptive’) includingperiostitis or folded or migrated fibrotic mesh material are not eligible as their pain isprobably unresponsive to an exclusive neurectomy 8 . Patients that will probably also notrespond to a tailored neurectomy are the ‘long-term neuropathic pain sufferers’, as theymay have developed sensitization of the central nervous system. Permanent sensitisationon cerebral level is thought to render peripheral interventions such as a neurectomyinsufficient 18 . Although these patients typically report symptomatology associated withneuropathic pain, peripheral nerve blocks will probably not induce pain reduction. Therefore,a substantial temporary pain reduction after inguinal nerve block with lidocainserves as an important prerequisite for inclusion in the present trial.There is little evidence on the beneficial effects of an injection of a cocktail of agents forthe treatment of chronic inguinal neuropathic pain. The choice for a combination oflidocain, corticosteroids and hyaluronic acid was made after consultation of several anaesthesiologist-painspecialists 19 . One study suggested that corticosteroids act by suppressionof ectopic neural discharges from the injured nerve endings 6 . Moreover,hyaluronic acid may soften scar tissue and may aid in local infiltration of the anaestheticand corticosteroids 20 . It was hypothesized that the combination of these twosubstances acted synergistically and facilitated and potentiated the analgesic effectsof lidocain.Although the sequence of steps in the surgical neurectomy is standardized as much aspossible, experience with past cases indicated that each patient requires individualization.Therefore, pre- and perioperative findings guided us on the handling of the affectednerves, ‘the tailored approach’ 12 . In contrast, a single specialist center advocates astandard ‘triple neurectomy’ for this pain syndrome, removing all three inguinal nervesduring one procedure , achieving success rates up to 85%. However, slightly lower successrates for this difficult chronic pain issue are probably more realistic, which we havedemonstrated in a recently published retrospective review on the ‘tailored approach’.The latter patient cohort exhibited a more heterogeneous pain pattern (e.g. alsonon-neuropathic) and had often received surgical interventions in other clinics as well.102 Chapter 7Randomized controlled trial of neurectomy versus injection with lidocain, corticosteroids... 103