10/3/2017 Welcome to the Wisconsin Worker’s Compensation Forum Where Do Where Do Hernias Hernias Come Come From? From? October Octob r 4, 4, 2017 2017 DISCLOSURES • No disclosures or relevant financial relationships to report Where do Hernias Come From? Brian D. Harrison MD October 4, 2017 Groin Hernias Definition Two types: Those that occur above the abdominocrural “A protrusion of abdominal contents through crease are described as inguinal an opening in the wall of the cavity in which those below are femoral hernia it is contained” Inguinal hernia are further divided into direct type (hernia starts medially and protrudes outward and forward) or But, what makes it a hernia – the opening in indirect (hernia starts laterally and the wall, or the contents that protrude protrudes obliquely or tangentially toward through it? or into the scrotum) 1
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10/3/2017 “Leave well enough alone?” 1/3 hernias cause no/few symptoms when found Surgery will reduce risk it could strangle (but that’s uncommon anyway) . . . AND: 10-20% stay or become painful AFTER surgery Intestine Pushes Intestine May Intestine May Be into the Sac What becomes of painless hernias if left alone? Wall Weakens Become Strangulated As the intestine The abdominal Trapped If the intestine is two recent randomized trials (from the US and the UK) pushes further lining bulges out The sac tightly trapped, it into the sac, it have compared surgery with observation through a weak containing the becomes forms a visible area and begins to intestine may strangulated. The After 2 years, no difference found in either trial bulge. The bulge form a hernia sac. become trapped strangulated area may flatten when This means: The sac may (incarcerated). If loses blood supply you lie down or contain fat, this happens, you and may die. This push against it. YES, you can leave well enough alone if your hernia intestine, or other won't be able to can cause severe This is called a doesn’t hurt (FIX IT when it does) tissues. At this point flatten the bulge. pain and block the reducible hernia the hernia may or You may also intestine. YES, you may start work with an unrepaired painless and does not may not cause a have pain. Emergency surgery cause any hernia visible bulge. Prompt treatment is needed to relieve immediate may be needed. the blockage. danger. 3
10/3/2017 Where Do People Think Hernias Come From? Who gets them? Lifetime risk of inguinal hernia: 27% of men and 3% of women Demographics of accepted work claims: (Rutkow, 1997) random survey of 1000 Americans: 96.8% were males and 3.2% were females 98% believed heavy lifting could cause hernia The average age 41.0 years old 60% felt that accident could be causative (12.3%) were re-current cases 54% felt that coughing could produce a hernia 54% thought obesity could contribute to hernia 2% felt smoking had an impact 62% knew you could have one from birth 3 Magic Questions in Occupational Did THIS hernia come from Disease Causality! working? a.k.a. Bradford-Hill Criteria for Dummies (like me!) CAN IT? Can work cause this type of hernia to arise? Is it possible? PATHOPHYSIOLOGY DOES IT? Does this type of hernia occur more often among large groups of people who do this particular job? EPIDEMIOLOGY DID IT? Did this case likely come about in that way, in terms of the facts and circumstances? CHRONOLOGY for example 4
10/3/2017 Problems w Theory of Increased Intra-Abdominal Pressure (IIP) It does increase with certain types of lifts CAN IT? But IIP while lifting comes and goes fast Protective mechanisms exist for brief IPP Sustained IIP defeats these mechanisms Umbilical hernias strongly linked to sustained IPP in pregnancy, abdominal obesity Obesity NOT associated with inguinal hernias despite the IPP it causes Some Physiology Research Some Physiology Research Goes Favors Work-Relatedness Against W ork-Relatedness In 1959, Davis - report on five healthy adult Deeper cris-crossed muscle fibers (internal males with monitored at internal pressures oblique and transversus abdominus) will (esophagus, stomach, rectum) while lifting automatically contract when the muscles of the weights in various positions. abdomen tighten. This acts as a shutter on the posterior wall to protect it from herniation, and is “There is but little pressure change within either called the Shutter Mechanism . trunk cavity when weights are lifted in the erect posture. (Data) show that there is a considerable Contraction also narrows the internal inguinal increase in pressure when stooping, and that ring, termed the Closure Mechanism . there is a direct relationship between the Sudden efforts automatically activate these magnitude of the weight and the height of the mechanisms, but gradual, long-term increased pressure induced” intra-abdominal pressure, such as pregnancy, “The intraabdominal pressures are largest in the does NOT stooping and prone (face down) positions” 5
10/3/2017 Some Pathology Research Goes Against Work-Relatedness Pans (1997): Biomechanical, physiologically oriented study on DOES IT? groin connective tissue characteristics used fresh samples of groin tissue harvested from individuals undergoing hernia repair and subjected them to various biomechanical stresses. “Presently reported biomechanical alterations seem to be the cause and not the consequence of hernias . . . This is therefore in keeping with other authors’ thoughts that inherent connective tissue pathology probably plays a role in the genesis of groin hernia.” Most Epidemiologic Research Self-Perpetuating Myth? that favors W-R suffers from poor design! “Using 1994 DOL data . . . This provides support for the hypothesis that the hernias Kang 1994: “Although the rate ratios for are work-related, especially in work hernias varied significantly within involving strenuous, heavy manual labor.” occupations and industries, the highest Of course, what gets reported to DOL???? rate ratios found were in those industries Recall man-in-the-street interviews found and occupations involving manual labor.” 98% believed heavy lifting could cause hernia; OSHA record keeper decisions will reflect this bias! 6
10/3/2017 Weak Epidemiology Epidemiology Studies Must Control Research Favors W-R for Confounders (Personal Risks) for Inguinal Hernia Flich (1992) studied inguinal hernia in relation to level of physical work activity Family history Concluded that positive relationship. Smoking / Chronic Cough “The results of this study show that physical effort, as a risk factor, is closely related to the Especially if Chronic Obstructive Pulmonary appearance of inguinal hernias. A person whose Disease - COPD work involves lifting or other strenuous exertion has a higher risk than those whose jobs are less Bladder obstruction d/t enlarged prostate strenuous.” (Obesity DOESN’T increase rates) DIDN’T CONTROL FOR CONFOUNDERS What do you get when you put all Everyone likes the studies together? Fresh Danish! 2013 Danish analysis of world’s literature Occup Environ Med. 2012 Nov;69(11):802-9. doi: 10.1136/oemed-2012-100787. Epub 2012 Aug 30. Review of all 23 occupational epidemiologic hernia Impact of occupational mechanical exposures on risk of lateral and studies published by 2011 (meta-analysis) medial inguinal hernia requiring surgical repair. “Insufficient evidence to draw meaningful conclusions Vad MV 1 , Frost P, Bay-Nielsen M, Svendsen SW. about (i) the existence of causal associations between Author information specific occupational mechanical exposures and the 1 Danish Ramazzini Centre, Department of Occupational Medicine, Herning Regional Hospital, Gl. development of inguinal hernia, and (ii) the influence of Landevej 61, DK-7400 Herning, Denmark. these exposures on prognosis after inguinal hernia repair Scand J Work Environ Health. 2013 Jan;39(1):5-26. doi: 10.5271/sjweh.3305. with respect to hernia recurrence and persistent pain” Risk and prognosis of inguinal hernia I n relation to occupational mechanical exposures— a systematic review of the epidemiologic evidence. Danish Ramazzini Centre Danish Ramazzini Centre 7
10/3/2017 Danish 2012 Study Cohort of More Danish Data 1,545,987 men observed 5 years Did not find that the chance of needing In general, the risk of direct hernia repair reoperation following a successful hernia was unrelated to the exposures repair was related to occupational The risk of indirect hernia repair (“lateral”) mechanical exposures increased with ton-years, frequent-heavy- lifting-years, and esp. standing-years, but with ORs of only “up to around 1.4.” Application of this study to the next case your queue . . . Even this huge study 1.4 Odds Ratio indicates a WEAK had flaws . . . association Authors used it to calculate a Preventive Could not control for risk Fraction of 15% (meaning if all factors of smoking and occupational factors are eliminated, incidence of hernias drops 15%) physical activity off-work For any one hernia case – is this MATERIAL or IMMATERIAL? 8
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