Table 3.
Incidence rates with crude and adjusted incidence rate ratios (IRRs) for prosthetic joint infection according to 2 BMI categories and 2 weight categories (above and below the threshold)
| BMI < 35 n = 8,214 | BMI ≥ 35 n = 847 | Weight < 100 kg n = 8,286 | Weight ≥ 100 kg n = 775 | |
|---|---|---|---|---|
| Cases | 90 | 21 | 90 | 21 |
| Person-years | 53,495 | 5,128 | 54,049 | 4,573 |
| Incidence rate, cases/1,000 person-years | 1.7 | 4.1 | 1.7 | 4.6 |
| Crude IRR (95% CI) | 2.3 (1.5–3.8, p < 0.001) | 2.6 (1.6–4.2, p < 0.001) | ||
| Crude IRR (95% CI) a | 2.4 (1.5–3.8, p < 0.001) | 2.6 (1.6–4.2, p < 0.001) | ||
| Adjusted IRR (95% CI) b | 2.5 (1.5–4.3, p < 0.001) | 2.1 (1.3–3.6, p = 0.003) | ||
BMI: body mass index; IRR: incidence rate ratio; CI: confidence interval.
a
Crude estimates only including the cases with complete covariate information.
b
Adjustment was performed for age, sex, ASA score (ASA 1–2 vs. 3–4), presence of diabetes, smoking status, -etiology of OA (primary vs. secondary), site of arthroplasty, use of antibiotic-laden cement, and length of operation, using Cox regression analysis.