Back pain

How it is linked to our an­ces­tors

Down to Earth - - CONTENTS -

GP DUREJA, a pain medicine spe­cial­ist and di­rec­tor of the Delhi Pain Man­age­ment Cen­tre, at­tends to 300-400 pa­tients with com­plaints of back pain ev­ery week. If those are the num­bers for a sin­gle clinic in Delhi, then, it is not dif­fi­cult to imag­ine how per­va­sive the is­sue of back pain is in In­dia. “Rough es­ti­mates show that 80 per cent of the pop­u­la­tion suf­fers from at least one ma­jor episode of back pain in their life­time and there is a 22-43 per cent preva­lence of spinal pain cases in In­dia,” says Dureja, who pre­vi­ously worked at aiims on ad­vanced pain man­age­ment tech­niques.

In the 2010 Global Bur­den of Dis­ease study, of all 291 con­di­tions stud­ied, lower back pain ranked high­est in terms of dis­abil­ity (years lived with dis­abil­ity), and sixth in terms of over­all bur­den (dis­abil­ity-ad­justed life years). The global point preva­lence of lower back pain was 9.4 per cent. Dis­abil­ity-ad­justed life years in­creased from 58.2 mil­lion in 1990 to 83 mil­lion in 2010.

Back to the fore

What is man­i­fested as back pain is of­ten a con­se­quence of ill health of the tiny bones called ver­te­brae that en­case our spinal cord. The hu­man ver­te­bral col­umn is made up of 33 ver­te­brae stacked on top of the other. Each ver­te­bra is spaced from the other by tiny cush­ions called in­ter­ver­te­bral disc. Some­times, back pain can even re­sult in an ab­nor­mal­ity in this disc. While it is pos­si­ble for any­one to be af­flicted by back pain, there is in­creas­ing con­sen­sus that en­vi­ron­men­tal causes, like work­ing con­di­tions, bad pos­ture, stress and seden­tary lifestyles of­ten cause back pain (see ‘Six com­mon mis­takes to avoid’, p39).

In a pa­per pub­lished in the jour­nal, BMC Evo­lu­tion­ary Bi­ol­ogy, on April 27 this year, sci­en­tists have pro­posed that back pain is linked to the shape of ver­te­brae. They say that the more an in­di­vid­ual’s ver­te­bra is shaped like his/her non-hu­man an­ces­tors, the more likely he/she is to get back pain. Kim­berly Plomp, a post­doc­toral re­searcher from Si­mon Fraser Univer­sity, Canada, who is the first au­thor of the study, told the press, “Our study is the first to use quan­ti­ta­tive

meth­ods to un­cover why hu­mans are so com­monly af­flicted with back prob­lems com­pared to non-hu­man pri­mates.The find­ings have po­ten­tial im­pli­ca­tions for clin­i­cal re­search,as they in­di­cate why some in­di­vid­u­als are more prone to back prob­lems.”

The sci­en­tists com­pared me­dieval-pe­riod spec­i­mens of 114 hu­man, 56 chim­panzee and 27 orang­utan ver­te­brae and found that there ex­isted a clear “dif­fer­ence in shape be­tween healthy hu­man ver­te­brae, chim­panzee ver­te­brae and orang­utan ver­te­brae”. These dif­fer­ences could be at­trib­uted to their “dif­fer­ent modes of lo­co­mo­tion”.The sec­ond thing they ob­served was that “patho­log­i­cal (dis­eased) hu­man ver­te­brae shared more sim­i­lar­i­ties in shape with chim­panzee or orang­utan ver­te­brae than with healthy hu­man ver­te­brae.”

The team looked for a spe­cific patho­log­i­cal symp­tom called the Sch­morl’s node, which is known to be a bony in­di­ca­tor of in­ter­ver­te­bral disc her­ni­a­tion.The sci­en­tists say that “com­pared to healthy hu­mans, patho­log­i­cal hu­mans and chim­panzees have rel­a­tively smaller neu­ral foram­ina, shorter, wider pedi­cles and rounder ver­te­bral bod­ies”.They also found that “healthy hu­man ver­te­brae are sta­tis­ti­cally dis­tin­guish­able from chim­panzee ver­te­brae, whereas patho­log­i­cal hu­man ver­te­brae are not”.

The au­thors be­lieve dis­eased ver­te­brae, which are closer in shape to hu­man an­ces­tors, are less adapted for bipedal­ism—a form of lo­co­mo­tion where an or­gan­ism uses its two rear limbs for move­ment.As a re­sult,these an­ces­tor-like ver­te­brae be­come more prone to ail­ments of the ver­te­bral col­umn.They call this “the an­ces­tral shape hy­poth­e­sis”.

Cor­re­la­tion vs dogma

Com­ment­ing on the study, H S Ch­habra, chief of Spine Ser­vice and med­i­cal di­rec­tor at the In­dian Spinal In­juries Cen­tre, New Delhi, says,“The au­thors have mooted a hy­poth­e­sis and have car­ried out a pre­lim­i­nary study.This needs to be sub­stan­ti­ated by biome­chan­i­cal and clin­i­cal stud­ies.” He agrees that there ex­ists a range of vari­a­tion in the shape of the ver­te­bra of hu­mans. For ex­am­ple, the pedi­cle part of the ver­te­bra is much nar­rower among In­dian pop­u­la­tions, com­pared to their Euro­pean coun­ter­parts. “The pa­per is strongly bi­ased to the dogma that the hu­man spine is not well adapted to bipedal­ism.This is not a given: spines are,in fact,well adapted to bipedal­ism and bone and car­ti­lage have a very strong ca­pac­ity to adapt them­selves to in­di­vid­ual me­chan­i­cal load­ing regimes,”says Theodoor H Smit,a pro­fes­sor at the depart­ment of or­tho­pe­dic surgery, VU Univer­sity Med­i­cal Cen­tre, move Re­search In­sti­tute, Am­s­ter­dam. “This is an old dogma that doc­tors tell to their pa­tients to make them ac­cept their back pain, but it is not true,”he adds.

Spine and its func­tion­al­ity are com­plex is­sues. Sev­eral ge­netic and en­vi­ron­men­tal fac­tors are re­spon­si­ble for its op­ti­mum func­tion­ing. With so much con­tra­dic­tion in views among sci­en­tists, only fur­ther stud­ies on the ver­te­bral shape of live sub­jects can es­tab­lish whether or not ver­te­bral shape has a ma­jor bear­ing on spinal prob­lems.Till that hap­pens,all one can do is to stay in good phys­i­cal shape and cre­ate op­ti­mum con­di­tions for our spine to func­tion.

Ver­te­bra The study found a pos­i­tive cor­re­la­tion be­tween the shape of the ver­te­bra and Sch­morl's node, which is an in­di­ca­tor of a spinal ab­nor­mal­ity— in­ter­ver­te­bral disc her­ni­a­tion

Sch­morl's

node

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