Table 2.
Associations between occupational heavy lifting and hip structural changes
| Univariate β or odds ratio (95% CI) | P | Multivariate β or odds ratio (95% CI) Model 1 | P | Multivariate β or odds ratio (95% CI) 4 Model 2 | P | |
|---|---|---|---|---|---|---|
| Heavy lifting aged 18 to 30 years (yes versus no) | ||||||
| Femoral head cartilage volume1 | 327 (97, 556) | <0.01 | 18 (−127, 164) | 0.80 | 15 (−132, 162) | 0.84 |
| Femoral head cartilage defects 2 | ||||||
| Anterior | 5.7 (0.7, 46.3) | 0.11 | 5.2 (0.6, 44.7) | 0.13 | 5.0 (0.6, 43.1) | 0.14 |
| Central superolateral | 1.8 (0.8, 3.3) | 0.06 | 1.8 (0.9, 3.4) | 0.08 | 1.8 (0.9, 3.4) | 0.09 |
| Central inferomedial | 1.5 (0.8, 2.6) | 0.17 | 1.3 (0.7, 2.4) | 0.35 | 1.3 (0.7, 2.4) | 0.37 |
| Posterior | 1.7 (0.8, 3.5) | 0.19 | 1.8 (0.8, 4.0) | 0.15 | 1.8 (0.8, 4.1) | 0.14 |
| Femoroacetabular BMLs 3 | ||||||
| Anterior | 1.0 (0.5, 2.1) | 0.93 | 1.2 (0.6, 2.6) | 0.63 | 1.2 (0.5, 2.6) | 0.67 |
| Central superolateral | 4.3 (1.8, 10.4) | <0.01 | 3.8 (1.5, 9.2) | <0.01 | 3.9 (1.6, 9.8) | <0.01 |
| Central inferomedial | 4.0 (0.9, 18.4) | 0.08 | 4.4 (0.9, 21.6) | 0.07 | 5.0 (1.0, 26.2) | 0.06 |
| Posterior | 2.0 (0.8, 5.4) | 0.15 | 2.3 (0.8, 6.5) | 0.10 | 2.5 (0.9, 7.0) | 0.08 |
| Persistence score for heavy lifting (grades 1 to 3) | ||||||
| Femoral head cartilage volume1 | 189 (33, 345) | 0.02 | 48 (−50, 146) | 0.33 | 49 (−49, 148) | 0.32 |
| Femoral head cartilage defects 2 | ||||||
| Anterior | 2.4 (0.8, 7.7) | 0.13 | 3.1 (0.8, 11.0) | 0.10 | 3.1 (0.8, 12.0) | 0.11 |
| Central superolateral | 1.6 (1.1, 2.5) | 0.02 | 1.6 (1.0, 2.5) | 0.04 | 1.6 (1.0, 2.5) | 0.04 |
| Central inferomedial | 1.1 (0.8, 1.6) | 0.55 | 1.0 (0.7, 1.5) | 0.93 | 1.0 (0.7, 1.6) | 0.89 |
| Posterior | 1.2 (0.7, 2.0) | 0.44 | 1.2 (0.7, 2.1) | 0.48 | 1.2 (0.7, 2.1) | 0.44 |
| Femoroacetabular BMLs 3 | ||||||
| Anterior | 0.8 (0.5, 1.3) | 0.34 | 0.8 (0.5, 1.3) | 0.33 | 0.8 (0.5, 1.3) | 0.32 |
| Central superolateral | 1.6 (1.0, 2.6) | 0.05 | 1.5 (0.9, 2.5) | 0.11 | 1.5 (0.9, 2.6) | 0.09 |
| Central inferomedial | 1.9 (0.8, 4.4) | 0.14 | 1.7 (0.7, 4.1) | 0.27 | 1.7 (0.7, 4.3) | 0.25 |
| Posterior | 1.9 (1.0, 3.8) | 0.06 | 1.9 (1.0, 3.8) | 0.07 | 2.0 (1.0, 4.1) | 0.05 |
1Regression coefficient (β) (95% CI) where for every one unit increase in the exposure (occupational heavy lifting), there is an associated increase (+) or decrease (−) in femoral head cartilage volume (mm3) adjusted for age, gender, BMI, femoral head bone area and MRI centre in Model 1; 2odds ratio (OR) where for every one unit increase in the exposure (occupational heavy lifting), there is an associated increased risk (value >1) or decreased (value <1) risk for cartilage defects, adjusted for age, gender, BMI, femoral head cartilage volume and MRI centre in Model 1; 3odds ratio (OR) where for every one unit increase in the exposure (occupational heavy lifting), there is an associated increased risk (value >1) or decreased (value <1) risk for BMLs adjusted for age, gender, BMI and MRI centre in Model 1; 4Model 2: vigorous physical activity in past 7 days and heavy domestic chores in past 7 days added to Model 1 multivariate equation. CI, confidence interval; BMLs, bone marrow lesions; BMI, body mass index; MRI, magnetic resonance imaging.