Table 1.
Characteristics of patients who underwent primary total knee replacement and revision surgery between 1997 and 2009
| Patients from the DKAR (2013) (n = 43,910) n (%) | Dermatitis patients from the DKAR a (n = 327) n (%) | Odds ratio (95% CI) b | |
|---|---|---|---|
| Female gender | 27,367 (62.3) | 234 (71.6) | 0.7 (0.5–0.8) |
| Age groups: | |||
| 10–49 | 2,224 (5.1) | 15 (4.6) | 1.1 (0.7–1.9) |
| 50–59 | 7,383 (16.8) | 68 (20.8) | 0.8 (0.6–1) |
| 60–69 | 14,721 (33.5) | 111 (33.9) | 1 (0.8–1.2) |
| 70–79 | 14,161 (32.2) | 108 (33.0) | 1 (0.8–1.2) |
| > 79 | 5,421 (12.3) | 25 (7.6) | 1.7 (1.1–2.6) |
| Primary diagnosis: | |||
| Primary idiopathic osteoarthritis | 36,694 (83.6) | 281 (85.9) | 0.8 (0.6–1.1) |
| Secondary osteoarthritis | 4,190 (9.5) | 24 (7.3) | 1.3 (0.9–2) |
| Sequelae of trauma | 1,029 (2.3) | 3 (0.9) | 2.6 (0.8–8.1) |
| Rheumatoid arthritis | 1,389 (3.2) | 16 (4.9) | 0.6 (0.9–1.1) |
| Sequelae of other arthritides | 211 (0.5) | 0 | |
| Hemophilia | 21 (0) | 1 (0.3) | 0.2 (0.02–1.2) |
| Other diagnoses | 376 (0.9) | 2 (0.6) | 1.4 (0.4–5.7) |
| Type of operation: | |||
| Total arthroplasty | 40,773 (92.9) | 301 (92.0) | 1.1 (0.8–1.7) |
| Unicompartmental arthroplasty | 3,137 (7.1) | 26 (8.0) | 0.9 (0.6–1.3) |
| Previously operated in the same knee | 13,261 (30.2) | 86 (26.3) | 1.2 (1–1.6) |
| Cause of revision: | |||
| Aseptic loosening | 883 (2.0) | 7 (2.1) | 0.9 (0.4–2) |
| Pain but no loosening | 669 (1.5) | 13 (4.0) | 0.4 (0.2–0.7) |
| Instability of the knee | 587 (1.3) | 9 (2.8) | 0.5 (0.3–0.9) |
| Deep infection | 622 (1.4) | 7 (2.1) | 0.7 (0.3–1.4) |
| Secondary insertion of patella component | 340 (0.8) | 5 (1.5) | 0.5 (0.2–1.2) |
| Polyethylene failure, patella/tibia | 223 (0.5) | 3 (0.9) | 0.6 (0.2–1.7) |
| Other | 443 (1.0) | 1 (0.6) | 3.3 (0.5–23.7) |
| Postoperative complications | 2,023 (4.6) | 11 (3.4) | 1.4 (0.8–2.5) |
a
Patients who were examined for metal allergy at Gentofte Hospital
b
Comparison of patients from the Danish Knee Arthroplasty Register (DKAR) (reference category) and patients from the DKAR who were also examined for metal allergy at Gentofte Hospital, Copenhagen (chi-square test). Fisher’s exact test was used when the expected frequency in 1 of the cells was lower than 5.