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Causation of lumbar spine disorders.13 January at 11:45 from atlas
Causation of lumbar spine disorders.Share5 January at 02:10 from atlas
The causation of lumbar spine disorders(LSD) or lumbar spine radiological changes(LSRC) are two of the most frequently encountered by an IME in spinal practice.At first it must be stated that an accurate diagnosis is required with respect to the reported symptoms, incapacity and requirement for certain treatments including drugs of dependence and surgery.The IME may not be provided with any, or sparse contemporaneous medical notes regarding the documented history and detailed examination findings at, or shortly after the subject incident , injury or event.Further more there is a need for incident reports and progressive chronological records to assess progress and time of onset of each symptom and what the signs were. At times the IME is asked to approve major spinal surgery without any , or at times a portion of this valuable information.
Scientific and legal analyses of causation approach evidence differently.Scientific versus Legal cause analyses refer to : predominant, major or significant cause (Medical) whereas Legal is interested in proximate cause. Medical refers to an Inductive argument with Legal deductive logic. Doctors look at populations whereas lawyers the individual case.Medical assessors relate to the stochastic or chaos theory with lawyers deterministic. Doctors prefer randomised trials (see prior monograph on Sir Austin Bradford Hill ) with lawyers weighing up experts opinions as their qualifications are accepted. Doctors relate to the concepts of multifactorial causation and strict application of aetiology whereas lawyers relate to unifactorial cause and seek responsibility rather than details of the complexities of determining causation scientifically.I have referred to Sir Austin Bradford Hill's work on causation in a previous monograph.The most common heuristic in applying deductive logic to statistical data is the Hill principles of causation and relate to inter alia, mechanistic or biomechanics studies on animals or cadavers, Cohort studies that demonstrate a strength of association and interventional or crossover studies that demonstrate a reversal of causation.
Another commonly utilised heuristic is the attributable-fraction method which finds that if a risk factor has a relative risk of 2 or more, it can be argued that the causal risk for an individual is 50% or more, or 'within reasonable medical certainty or probability'.
Usually spinal changes are multi-level and are likely degenerative with single level more suggestive of traumatic causation. Caution is advised when applying deterministic logic in individual cases in the absence of good population numbers and data to avoid causal fallacies such as post hoc ergo proper hoc.
It is difficult to examine the effect of acute trauma in a scientific manner as trauma can generally only be defined retrospectively.Deyo et al (Devo RA. Weinstein JN.Primary care: low back pain.N Eng J Med.2001;344:363-370) sagely remind us that strain and sprain have never been anatomically or histologically characterised.As a clinician I can say that short of after surgery or penetrating fracturing spinal injury , I cannot recall a CT or MR showing lumbar (or cervical) strain or sprain findings-on either the films or reports by radiologists.
Because of the high prevalence of low back pain in the community we are left with various risk factors with varying levels of association with the subject condition.Prospective studies are scarce -these maximise power and minimise bias and confounding compared with retrospective studies.
Disc herniations are predominantly the consequence of annulus fibrosis degeneration with fissures( or tears) , fragmentation along with genetic factors, age-related disc changes,(The odds ratio:OR: for sciatica increases by 1.4 each decade up to 64 years), ischaemic degeneration, effects of obesity, effete of smoking age, gender and occupational ( carpenters OR 1.7),and recreational factors including fitness,
The IME needs to be familiar with the thin-skull and the crumbling skull principles and that theses are not medical or scientific areas but legal.There are no studies or body of valid literature upon which an IME can refer to.
Occupational factors have been shown to have a statistically significant association between weight lifting and certain lumbar conditions. Andreas Seidler et al ( Occup Environ Med 2003;60:821-830) found a link between cumulative (not specific incident) extreme forward lifting but only in the setting of degeneration but not otherwise normal spines. In 2009 Andreas Seidler et al conducted the EPILIFT multi-centre case-control study(BMC Musculoskeletal Disorders 2009, 10:48)and stated that their data suggests' an association between past physical workload and lumbar disc disease(symptomatic osteochondrosis / spondylosis)'.and 'exposure to manual handling of objects might play a role particularly in lumbar disc space narrowing, while exposure to trunk inclination might be of particular importance for ..lumbar disc herniation".Importantly this extensive 2009 multi-centre trial stated' this would be in accordance with (sic ..their prior study) ..of clear dose-response relationship between exposure to weight lifting/carrying and asymptomatic osteochondrosis/spondylosis, whereas exposure to weight lifting and carrying was of limited relevance to isolated lumbar disc herniation.Their finding was that their findings supported a clear dose relationship between cumulative lumbar load and lumbar disc herniation as well as symptomatic lumbar disc narrowing.
Shiri Rahman et al (Am J Epidemiol, 2014;179(8):929-937.) found a consistent dose-resonse relationship between both overweight and obesity factors and lumbar radicular pain and sciatica in both men and women.
Thus , I conclude on reviewing epidemiological data ,along with my study of age related MR lumbar spine changes and the mechanisms of degeneration, including herniation,that there is a relationship between lumbar loading over an extended period of time and lumbar disc herniation in degenerate spines but not healthy ones. The strength or odds factor compared with the other factors is not published.There are cadaver and animal studies assessing load induced disc ruptures but no live human such studies,. Age, smoking. obesity, lifestyle , genetic and occupational activities all have a role in lumbar disease but there is no evidence that occupational acute loading is a major or significant contributing factor in acute disc herniation although there is evidence that cumulative exposure to heavy lifting increases lumbar disc herniation in degenerate spine. The significant issue is that there is no valid evidence that occupational findings , including Seidler's EPILIFT study (and others including Professor Franco Postacchini) that the risk is major or significant-it is one of a number of (multi-factorial ) risks.The strongest evidence is in relation to increasing age and chronic degeneration as being the 'major' or 'significant' contributing factor both causing lumbar spondylosis with , and with out disc herniation.
Patients must consult with their treating medical practitioners at all times for treatment.
Dr Michael Coroneos is a senior Brisbane neurosurgeon.
Qualifications: CIME MASE FACS FRCSI FRACS FAIM FRCS(EDIN)SN
MB BS (1st Class HONS) MNSA MNSQ MAPS
National RACS Examiner/ RACS Mortality Assessor/ Adjunct Assistant Professor.