The role of cumulative physical work load in lumbar spine disease: risk factors for lumbar osteochondrosis and spondylosis associated with chronic complaints

Objectives-To investigate the relation with a case-control study between sy mptomatic osteochondrosis or spondylosis of the lumbar spine and cumulative occupational exposure to lifting or carrying and to working postures with extreme forward bending. Methods-From two practices and four clinics were recruited 229 male patient s with radiographically confirmed osteochondrosis or spondylosis of the lum bar spine associated with chronic complaints. Of these 135 had additionally had acute lumbar disc herniation. A total of 197 control subjects was recr uited: 107 subjects with anamnestic exclusion of lumbar spine disease were drawn as a random population control group and 90 patients admitted to hosp ital for urolithiasis who had no osteochondrosis or spondylosis of the lumb ar spine radiographically were recruited as a hospital based control group. Data were gathered in a structured personal interview and analysed using l ogistic regression to control for age, region, nationality, and other disea ses affecting the lumbar spine. To calculate cumulative forces to the lumba r spine over the entire working life, the Mainz-Dortmund dose model (MDD), which is based on an overproportional weighting of the lumbar disc compress ion force relative to the respective duration of the lifting process was ap plied with modifications: any objects weighing greater than or equal to5 kg were included in the calculation and no minimum daily exposure limits were established. Calculation of forces to the lumbar spine was based on self r eported estimates of occupational lifting, trunk flexion, and duration. Results-For a lumbar spine dose >9x10(6) Nh (Newtonxhours), the risk of hav ing radiographically confirmed osteochondrosis or spondylosis of the lumbar spine as measured by the odds ratio (OR) was 8.5 (95% confidence interval (95% CY) 4.1 to 17.5) compared with subjects with a load of 0 Nh. To avoid differential bias, forces to the lumbar spine were also calculated on the b asis of an internal job exposure matrix based on the control subjects' expo sure assessments for their respective job groups. Although ORs were lower w ith this approach, they remained significant. Conclusions-The calculation of the sum of forces to the lumbar spine is a u seful tool for risk assessment for symptomatic osteochondrosis or spondylos is of the lumbar spine. The results suggest that cumulative occupational ex posure to lifting or carrying and extreme forward bending increases the ris k for developing symptomatic osteochondrosis or spondylosis of the lumbar s pine.