Surgical management of chronic inguinal pain syndromes - Liespijn

INTRODUCTIONHernia recurrence rates have plummeted ever since the introduction of mesh. Researchinterest has, therefore, shifted towards studying the characteristics of chronic pain followingroutine implantation of mesh 1 . Approximately 11% of all operated hernia patientsare troubled by chronic inguinal pain 2-4 . About half suffers from neuropathic paincaused by entrapment or damage to one (or more) of the inguinal nerves (ilioinguinal,iliohypogastric or/ and genital branch of the genitofemoral nerve). The other halfexperience nociceptive pain including periostitis, recurrent hernia, folded mesh(‘meshoma’), fibrotic tissue or funiculodynia 5 .Published studies on treatment regimes for postherniorrhaphy inguinal pain syndromesare scarce. Examples of non-operative treatment options include nerve blocks with localanaesthetics and corticosteroids 6 , transcutaneous electric nerve stimulation (TENS), orpulsed radio frequency (PRF) 7 . Neuropathic pain caused by nerve entrapment can alsobe treated by an open nerve removal (neurectomy), as this technique effectivelydecreased pain in 60-80% of the patients 8-13 . Peripheral nerve blocks likely aid in discriminatingbetween pain types. However, it is important to realize that to our knowledgeno validation studies on sensitivity and specificity of nerve blocks in discriminatingneuropathic from nociceptive pain have been conducted.In order to evaluate which therapeutic regime serves best for neuropathic postherniorrhaphypain syndromes, a randomized controlled trial was constructed comparingtwo frequently used treatment modalities, nerve blocks and neurectomy of the inguinalnerves. Characteristics of this randomized controlled trial will be discussed in thepresent article.METHODSStudy designThe GroinPain Trial is a randomized, non-blinded, monocenter study. The protocol wasapproved by the Regional Ethics Committee of the Máxima Medical Center, Veldhoven,The Netherlands (no. 0543). The objective is to evaluate long-term pain reduction inpatients with chronic postherniorrhaphy groin neuralgia following two different treatmentmodalities. Clinical results of nerve blocks with lidocain, corticosteroids and hyaluronicacid are compared with a operative neurectomy of the ilioinguinal, iliohypogastricor/and genital branch of the genitofemoral nerve(s). Patient enrolment started inFebruary 2006. The study protocol has been registered at www.clinicaltrial.gov(ClinicalTrials.gov identifier: NCT00306839).Study populationAll adult patients (18 years or older) with chronic neuropathic pain after routine inguinalhernia repair (open or laparoscopic) are considered for inclusion. A pain-free interval(hours to days/weeks) after a diagnostic nerve block using 10 cc 1% lidocain injectedinto the trigger point is a prerequisite for inclusion. Patients with less than 50% painreduction do not qualify for study. A nerve block administered at the outpatientdepartment is part of our standard diagnostic pathway. In some patients, a diagnosticnerve blocks results in a persistent pain reduction. These patients are excluded fromfurther participation but are registered and monitored over time. To assure that theinternational definition for the study of chronic pain (pain persisting beyond the normalhealing period of 3 months) was applicable to all patients, the minimal follow-up periodof three months was chosen. Patients were excluded if an adequate follow-up wasimpossible, omitting all patients with severely compromised physical or mental health.Patients with a recurrent inguinal hernia, harbouring signs of local inflammation or havingan American Society of Anaesthesiologists classification 3 or more are also excluded.RandomizationAfter a thorough explanation regarding rationale and important characteristics of thetrial, verbal and written informed consent is obtained at the outpatient department.Patients are subsequently randomized to repetitive nerve blocks using lidocain, corticosteroidsand hyaluronic acid (group A) or a neurectomy (group B, figure 1). Blocks ofeight-randomization principle without prestratification are applied by computer.InterventionsNerve blocks (Group A, figure 2): This group receives an injection with 2 cc 1% Lidocain, 40mg corticosteroids (Depomedrol®), and 75 IE hyaluronic acid (Hyason®) at the surgicaloutpatient department. These blocks are placed in the pain trigger point. In case ofadditional genital branch neuralgia, a separate nerve block placed at the internal inguinalring is often mandatory. If pain reduction is temporary, injections are repeated at twoweek intervals. A maximal number of three blocks is used over a six week period. Allinjections are administered by the principal investigators (M.L. or T.V.).Neurectomy (Group B): Patients are offered surgery using spinal or general anaesthesiain a day-care setting. All operations are performed by the senior authors M.S. and R.R.,both experienced in performing this procedure. Patients receive 2.500 IU of low molecularheparin (Fragmin®) subcutaneously two hours prior to the procedure. By extendingthe inguinal incision some centimetres laterally, access is gained to an unaffected areain most cases. The iliohypogastric and/or ilioinguinal nerves penetrating internal obliquemuscles are identified and followed as proximal as possible. The prosthetic material isusually opened and dissected for additional exposure. If indicated, the genital branch98 Chapter 7Randomized controlled trial of neurectomy versus injection with lidocain, corticosteroids... 99