Table VII.
Relative venous thromboembolism risk ratio of bilateral total knee arthroplasty (TKA) relative to unilateral TKA by risk factor. Only comorbidities with a sample size > 10 for bilateral TKA were analysed
| Risk factor | Bilateral PE, n (%) | Unilateral PE, n (%) | PE RR (95% CI) | Bilateral VTE, n (%) | Unilateral VTE, n (%) | VTE RR (95% CI) |
|---|---|---|---|---|---|---|
| Reference* | 66/3685 (1.8) | 150/15 266 (1.0) | 1.8 (1.4 to 2.4) | 78/3685 (2.1) | 186/15 266 (1.2) | 1.7 (1.3 to 2.3) |
| Elderly (> 70 yrs) | 19/835 (2.3) | 75/5477 (1.4) | 1.7 (1.0 to 2.7) | 21/835 (2.5) | 89/5477 (1.6) | 1.6 (1.0 to 2.5) |
| High VTE risk† | 13/223 (5.8) | 53/3567 (1.5) | 3.9 (2.2 to 7.1) | 15/223 (6.7) | 72/3567 (2.0) | 3.3 (1.9 to 5.7) |
| Low VTE risk‡ | 11/994 (1.1) | 14/2820 (0.5) | 2.2 (1.0 to 4.9) | 17/994 (1.7) | 18/2820 (0.6) | 2.7 (1.4 to 5.2) |
| Anaemia | 15/455 (3.3) | 24/2943 (0.8) | 4.0 (2.1 to 7.6) | 17/455 (3.7) | 32/2943 (1.1) | 3.4 (1.9 to 6.1) |
| Varicose veins | 1/14 (7.1) | 8/837 (1.0) | 7.5 (1.0 to 56.0) | 1/14 (7.1) | 16/837 (1.9) | 3.7 (0.5 to 26.0) |
| History of MI | 4/55 (7.3) | 8/796 (1.0) | 7.2 (2.2 to 23.0) | 4/54 (7.4) | 14/796 (1.8) | 4.2 (1.4 to 12.0) |
| Sleep apnoea | 5/287 (1.7) | 19/1604 (1.2) | 1.5 (0.55 to 3.9) | 6/287 (2.1) | 25/1604 (1.6) | 1.3 (0.6 to 3.2) |
| Afib | 6/97 (6.2) | 22/860 (2.6) | 2.4 (1.0 to 5.8) | 6/97 (6.2) | 26/860 (3.0) | 2.1 (0.9 to 4.9) |
| COPD | 1/34 (2.9) | 1/98 (1.0) | 2.9 (0.2 to 45.0) | 1/34 (2.9) | 1/98 (1.0) | 2.9 (0.2 to 45.0) |
| History of VTE | 2/58 (3.5) | 7/437 (1.6) | 2.2 (0.5 to 10.0) | 3/58 (5.2) | 12/437 (2.8) | 1.9 (0.6 to 6.5) |
| PVD | 2/31 (6.5) | 9/669 (1.4) | 4.8 (1.1 to 21.0) | 2/31 (6.5) | 14/669 (2.1) | 3.1 (0.7 to 13.0) |
| Solid tumour | 1/95 (1.1) | 8/574 (1.4) | 0.76 (0.1 to 6.0) | 1/95 (1.1) | 10/574 (1.7) | 0.60 (0.1 to 4.7) |
*All study patients included as a baseline reference for risk of bilateral relative to unilateral TKA †High VTE risk is taken to be the top 20% of National Inpatient Sample VTE scores above 80.63 points ‡Low VTE risk is taken to be the bottom 20% of NIS VTE scores below 48.34 points PE, pulmonary embolism; Bilateral PE, risk of PE for simultaneous bilateral total knee arthroplasty (TKA); Unilateral PE, risk of PE for unilateral TKA; Bilateral VTE, risk of combined VTE for simultaneous bilateral TKA; Unilateral VTE, risk of combined VTE for unilateral TKA; RR, relative risk; CI, confidence interval; VTE, venous thromboembolism, MI, myocardial infarction; COPD, chronic obstructive pulmonary disease; PVD, peripheral vascular disease