Surgical management of chronic inguinal pain syndromes - Liespijn

pensational costs in The Netherlands yearly.It should be appreciated that occupational disability affects about 1% of all operatedinguinal hernia patients. Interestingly, occupational disability after hernia repair andappropriate management schemes have received very little attention. Yet, with respectto work resumption, a neurectomy seems to be effective in over 50% of the patients.Therefore, millions of euros for worker’s compensational and additional costs (replacement,loss of productivity, medical costs) may be saved if an effective treatment modalitysuch as a neurectomy is provided. When these figures are extrapolated globally,huge sums of money can be saved.The present study indicates that tailored neurectomy is an effective treatment foroccupational disability due to postherniorrhaphy inguinal neuralgia in over half of thepatients. A successful neurectomy greatly reduces workers’ compensational costs andmay have substantial financial consequences worldwide.CONCLUSIONS1. Chronic pain and functional impairment are common long-term complications afteringuinal hernia repair and Pfannenstiel incisions.2. The VRS should be favoured over the VAS in future postherniorrhaphy pain assessment.3. Moderate to severe chronic pain after inguinal hernia repair can be classified intoneuropathic pain (50%), non-neuropathic pain (25%), and ‘funiculodynia’ (25%). Nerveentrapment is a frequent cause of chronic pain after a Pfannenstiel incision.4. Neurectomy provides substantial long-term pain relief in the majority of patients(50-75%) suffering from inguinal neuralgia after inguinal hernia repair or Pfannenstielincisions.5. Neurectomy is an (cost-)effective treatment modality for resolution of occupationaldisability due to postherniorrhaphy inguinal neuralgia.FUTURE PERSPECTIVESThe introduction of mesh techniques has reduced inguinal hernia recurrence rates spectacularly.However, some issues related to chronic pain are largely unknown. The bodyof evidence suggests that type of mesh or placement technique are not crucial for thedevelopment of pain. Therefore, which direction should future pain studies take?As some patients apparently are at risk for chronic pain development, it would behelpful to identify their characteristics preoperatively 27 . Some have found that geneticsusceptibility indeed is a risk factor for chronic pain development 6 . At present a fewgenotypes have been identified that may predispose for chronic pain states. Other ‘paingenes’ will likely be recognized in the near future, and this tendency could serve as abasis for preoperative identification of ‘pain individuals’. As a consequence, surgery maybe postponed in these individuals.Lately, numerous psychosomatic risk factors for chronification of pain have been identified.Among the most important determinants are long duration of the operation,high levels of acute postoperative pain, preoperative fear of surgery and optimism 28 .Prospective pre-operative identification with subsequent postoperative modulation ofthe most influential risk factors, may be worthwhile in preventing pain chronification.Future research may also focus on the identification of altered peripheral nerve signalling.The effects of inguinal neurectomy on various aspects of nerve signalling pathwaysmay give clues as to why this treatment is effective in some but not all individuals.Microglia in the dorsal horn are found to play a critical role in neuropathic pain 29 . Nerveinjury reduces microglial neuronal inhibition which may lead to a pathologically alteredsignalling pathway. Secondly, proinflammatory cytokines (IL-6) and sphingolipids havebeen found responsible for mechanical hypersensitivity 30 . Thirdly, neurotrophic factorsincluding nerve growth factor (NGF) act as peripheral pain mediators as well 31 . Infuture studies these and other substances may be chemically or histologically studiedin neurectomized nerve tissue. It may be hypothesized that different responses in thesesignalling pathways are related to clinical outcome.Various other clinical aspects of chronic pain mechanisms deserve further exploration.Some studies have assessed static quantative sensory testing (QST, measuring painthresholds, magnitude levels and tolerance) in the prediction of direct postoperativepain or chronic postoperative pain 32 . Research suggests that certain QST patterns can belinked to somatosensory phenotypes which may mirror certain pain mechanisms. Thesecharacteristics may eventually result in a mechanism-based treatment, or may evenallow for a separation between successful patients and failures. However, the discriminativevalue of these tests as a means of chronic pain prediction is still under debate.The role of inter-individual differences in dynamic pain tests such as diffuse noxiousinhibitory controls (DNIC) may even be more promising 33 . DNIC describes the phenomenonof one noxious stimulus inhibiting the pain produced by a second. For instance,subjects may receive thermal and cold stimuli in a certain order after which perceivedDNIC is measured using questionnaires. A reduced DNIC may be related to hypersensitivityfor clinical pain and possibly also to its chronification 32 . These test panels maytherefore aid in selecting patients at risk for chronification of pain. If other risk factorsfor pain are involved as well, one may decide against operation such as inguinal herniarepair or a gynaecological procedure using a Pfannenstiel incision.Is there any room for future improvement in the imaging department? Neuro-imagingstudies may provide objective data on plasticity, sensitisation and certain amplificationprocesses 34 . Moreover, functional MRI may identify the locations of neural sensitisationand other amplification processes, and may relate these findings to pain experience144 Chapter 10Summarizing discussion, conclusions, and future perspectives 145