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Month 2003

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August 2003

EExxcclluussiivvee FFeeaattuurreeExclusive Feature

Tendinitis: An Often Painful OccupationalCondition for Laboratorians• Kevin J. Costello

The U.S. Bureau of Labor Statistics(BLS) monitors occupational illnessesand injuries that occur in private indus-

try each year. Separating the various cate-gories can often be difficult because someoverlap exists among certain injuries like in therepetitive motion injury category, which in-cludes tendinitis and carpal tunnel syndrome.However, these injuries account for tens ofthousands of reported incidents each year. Infact, the BLS has cited that these injuries weresustained by at least 1 out of every 1250 full-time workers in the United States in 1999.They also acknowledged that the rate of inci-dence is most likely higher because under-re-porting often takes place, and the reportedcases only include injuries that resulted indays away from work.

A potential epidemic in the laboratoryWhile the risk of developing tendinitis or

other forms of overuse strain injuries is notconfined to people in a single industry or job,laboratory workers using pipettes may experi-ence a higher risk of these injuries. Tendon ormuscle overuse in the hand, wrist, arm orshoulder occurs from any combination ofrepetitive, unaccustomed, forceful, or awk-ward positions due to bad ergonomics. Theresulting micro injuries gradually accumulatefaster than they can heal and the area even-tually becomes painful. Because of the poorintrinsic healing capability of tendons, evenwith treatment and rest, a degradation ofstrength by as much as 30% is common formonths or years following an acute injury. Inthis weakened condition, the tendons are

prone to further injury, potentially continuingthe damage beyond the effectiveness oftreatments such as anti-inflammatory drugs,immobilization, slings and sprints, or steroidinjections. Surgery and long-term cessation ofoccupational activity may then be required.

While women incurred only 33% of the to-tal number of injuries reported by private in-dustry in 1999, the incidence rate for over-us-age injuries in women is 61%. This notabledifference may be due to a higher percentageof women in jobs that involve repetitive mo-tion, coupled with use of equipment that maynot be as ergonomically favorable to women.

The more common forms of tendon injuryexperienced by laboratory workers usingpipettes include:

• Medial epicondylitis - caused by wristflexion and pronation that injures the tendonsattached to the medial epicondyle of thehumerus. Pain occurs in the flexor tendons andmedial aspect of the elbow when the wrist isflexed or rotated outward.

• Lateral epicondylitis (tennis elbow) -caused by continued stress on grasping mus-cles of the hand on rotation when the forearmfaces upward or forward. Pain occurs over thelateral side (outside) of the elbow when thewrist is extended.

• Rotator cuff tendinitis - involves a groupof muscles that control shoulder rotation. Painoccurs when bringing the arm across the chest.

• Trigger finger/thumb - caused by a nodule(knot) or swelling in the lining of a tendon.Pain, popping or a catching feeling in the fin-ger or thumb occurs as the tendon squeezesthrough the opening of the tunnel (flexor

sheath) during movement.• DeQuervain’s tendinitis - caused by irrita-

tion or swelling of the tendons at the base ofthe thumb. Pain near the thumb side of thewrist occurs as well as an occasional “catch-ing or snapping” when the thumb is moved.

Government and industry have attempted toreduce exposure to some of the pipetting riskfactors and resultant injuries by recommendingmodifications to certain laboratory practicesand the creation of more ergonomically favor-able work environments. Additionally, pipettemanufacturers have reduced spring forces andadded electronics to some of their products inan effort to lower operating forces. However,because of the strong interrelationship be-tween force and posture, simple reductions inmechanical force requirements alone are notsufficient to reduce the physical exertion andmuscle fatigue that leads to injury.

An opportunity to reduce occupationalrisk

Recent evaluations of user exertion levelsrequired while pipetting shows considerabledifferences when the upper arm posture re-mains in ergonomically-favorable positions.The Ovation® BioNatural Pipette, by allowingthe forearm, wrist, and shoulder to remain inneutral positions, demonstrates favorable mus-cle and joint measurements during all pipettingfunctions (acquiring tips, aspirating & dispens-ing, discarding of tips) in comparison to tradi-tional, axial-designed pipettes. Ovation’s detip-ping effort levels required by the flexor musclein all individuals (Figure 1), and in the forearm,hand and thumb specifically among women

(Figure 2) are observed below the threshold of15% MVC (maximum voluntary contraction).MVC is a guideline supported in published lit-erature as an exertion level indicative of mus-cle fatigue. Arm flexion and extension duringplunger operation remains within recom-mended limits for maintaining effective armstrength (Figure 3). Wrist deviation when ap-plying tips also remains near the neutral posi-tion so there is no strength degradation as aresult of poor hand posture (Figure 4).

Many pipetting products have been intro-duced to the market in recent years boastingergonomic features such as plungers or but-tons that require less force due to electronicsor reduced spring forces, or soft grip handlesand hand hooks. However, these feature en-hancements fail to address or correct the pri-mary causative factor of strain and injury inthe upper arm extremity (neck, shoulder, el-bow, wrist and hand), specifically the awk-ward posture that takes place during use withthe device. When magnified with sufficientrepetition, even minimal stress and force lev-els can become formidable. Unfortunately, theforce/exertion threshold associated with over-use strain injuries varies greatly among indi-viduals and effects from injury accumulateover long periods, often going unnoticed untilthey are severe. However, laboratory workersmay consider reducing their occupational riskfactors now by using pipettes designed specif-ically to operate with neutral alignments ofthe upper arm extremities, and in all likelihoodreduce overuse strain injuries like tendinitisthat continue to aggravate the health of manywith increased frequency.

Additional Resources for ErgonomicInformation Particularly Relevant toLaboratory Practice:http://www.niehs.nih.gov/odhsb/ergoguid/home.htmNIEHS Health and Safety Guide to Laboratory Ergonomics.The National Institute of Environmental Health Sciences(NIEHS) is one of 25 Institutes and Centers of the NationalInstitutes of Health (NIH)

http://odp.od.nih.gov/whpp/ergonomics/ergonomics.htmlUS Department of Health and Human Services. TheNational Institutes of Health is the steward of medical andbehavioral research for the Nation.

http://www.osha.gov/ergonomics/U.S. Department of Labor - Occupational Safety & HealthAdministration

http://www.cdc.gov/od/ohs/Ergonomics/labergo.htmCenters for Disease Control - Laboratory Ergonomics. TheCenters for Disease Control and Prevention (CDC) is recog-nized as the lead federal agency for protecting the healthand safety of people.

http://www.isber.org/pdfs/barr.pdfPreventing repetitive stress injuries (RSI’s). Presentation byJason Barr, Division of Safety, National Institutes of Health

http://www.d.umn.edu/ehso/ergonomics/labergo.htmLaboratory Ergonomics. University of Minnesota

http://ergo.human.cornell.edu/Human Factors and Ergonomics. Cornell University. Thissite links to several ergonomic sites that focus on safetyissues, such as: carpal tunnel syndrome, back injuries, airquality, sick building syndrome, and lighting.

http://www-ehs.ucsd.edu/ergo/training/labergo/ErgoLabSlide1.htmPractical approach for improving comfort in research envi-ronments Daphne A. Thaung, certified Industrial Hygienist.University of California, San Diego - Environmnent, Healthand Safety Department

http://www.stanford.edu/dept/EHS/prod/researchlab/lab/laboratory_ergonomics.htmlLaboratory Ergonomics. Stanford University -Environmental Health & Safety Department

http://www.interface-analysis.com/ergoworld/ErgoWorld has planets specifically focused on OfficeErgonomics and Injury Prevention/Treatment. This site alsohas links to other topics in the field (industrial ergonomics,HCI/usability, transportation HF, HF in design), and providesinformation on employment opportunities, university pro-grams, consultants, products, and events.Write In xxx - Or Reply Online

• Awkward postures and working positions during pipetting are leading contributors to tendon injuries

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Action: elevated, extended arm reachesPotential Consequence: strain and inflam-mation to shoulder musclesLeads to: Rotator cuff tendonitis

Action: wrist ulnar deviation, tight hand grip,extended thumb reachPotential Consequence: swelling within ten-don liningsLeads to: Trigger finger/thumb, Carpal TunnelSyndrome

Action: elevated arm, forearm supination,wrist extension and radial deviationPotential Consequence: shoulder and upperarm injuries, elbow problems, swelling withintendon liningsLeads to: Lateral epicondylitis

Action: forearm supination, wrist flexion andulnar deviationPotential Consequence: strain to medialarea of elbow, swelling within tendon liningsLeads to: Medial epicondylitis

Action: tight hand grip, wrist ulnar deviation,thumb strainPotential Consequence: strain to medialarea of elbow and base of thumb, swellingwithin tendon liningsLeads to: DeQuervain’s tendonitis

The Ovation pipette designkeeps the entire upper arm inneutral positions, permittingmuscles and joints to operateefficiently with minimum effortlevels as shown in Figures 1-4.

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