Ultrasound lumbar canal measurement inhospital employees withbackpain

Theoblique parasagittal diameter ofthelumbarspinal canal attheL5-SIlevel was measured in49employees oftheWm Jennings BryanDornVeterans' Hospital using real time ultrasound inacase-control study. Individuals with acanal diameter ofless than14mm represented thelowest 10th percentile inthis population andbeing inthenarrowest 10th percentile constituted a risk factor fortime missed fromworkbecause oflowbackpain(odds ratio 10-7). Whereas numbers in this pilot study aresmall, results areconsistent withearlier ultrasound studies doneintheUnited Kingdomandwithother research showing increased morbidity fromlowbackpaininindividuals withsmall lumbar canals. Ultrasound hasadvantages overother modalities formeasuring thesize of thelumbar canal andmay beuseful asapreplacement screening examination inindustry. Lowbackpain(LBP)isacommoncondition that costs industry billions ofdollars annually inworkers' compensation claims alone.'2 Afewclaims result ina disproportionate amountofcost.23 Ina studyof Boeing Company employees 10%ofclaims accounted for79%ofthetotal costs fromLBP.4 Ifworkers at increased risk fordeveloping highcost backinjuries could beidentified before injury occurs special training orjobplacement, orboth, might lower their risk of serious lowbackdisability, which wouldreduce both employee suffering andemployer costs. An anatomically narrowlumbarspinal canal is associated withincreased morbidity arising fromat least three majorconditions: intervertebral disc dis- ease, neurogenic claudication (spinal stenosis syn- drome), androot entrapment syndromes. Theclinical importance ofa stenotic lumbarcanalhasbeen increasingly understood inrecent decades."2' The usefulness ofthisknowledge, however, hasbeen severely limited bythedifficulty inobtaining invivo canal measurements without unduecost, exposure to radiation, ordiscomfort.22 In1978Porter etalfirst showedthat midsagittal lumbar spinal canal diameters could bemeasured by ultrasound.23 Theydetermined thatlumbarcanals weresmaller inpatients withdisc symptoms thanin controls, andthat thegreater themorbidity thesmaller thecanal size.2 13Macdonald etal, using ultrasound,