Table 1 Demographics of Patients Undergoing Unilateral Total Knee Arthroplasty before Propensity Matching Analysis

Age, (y), mean ± SD

65.61 ± 9.34

66.33 ± 8.68

64.36 ± 10.28

1.97 (1.44, 2.50)

 < .001

Sex, % (n)

 Male

45.9 (2557/5574)

45.8 (1621/3540)

46.0 (936/2034)

-0.23 (-2.94, 2.49)

0.87

 Female

54.1 (3017/5574)

54.2 (1919/3540)

53.9 (1098/2034)

0.23 (-2.49, 2.94)

BMI, kg/m², Mean ± SD

31.67 ± 6.03

31.12 ± 5.74

32.64 ± 6.38

-1.52 (-1.86, -1.19)

 < .001

Functional status before surgery, % (n)

 Independent

99.6 (5553/5574)

99.7 (3530/3540)

99.5 (2023/2034)

0.26 (-0.11, 0.62)

0.13

 Partially dependent

0.38 (21/5574)

0.28 (10/3540)

0.54 (11/2034)

-0.26 (-0.62, 0.11)

 Totally dependent

0.00 (0/5574)

0.00 (0/3540)

0.00 (0/2034)

0.00 (-, -)

ASA PS, % (n)

 ASA PS 1 or 2

61.70 (3439/5574)

64.41 (2280/3540)

56.98 (1159/2034)

7.43 (4.76, 10.09)

 < .001

 ASA PS 3 or 4

38.30 (2135/5574)

35.59 (1260/3540)

43.02 (875/2034)

-7.43 (-10.09, -4.76)

Smoker, % (n)

 No

93.02 (5185/5574)

94.07 (3330/3540)

91.20 (1855/2034)

2.87 (1.41, 4.32)

 < .001

 Yes

6.98 (389/5574)

5.93 (210/3540)

8.80 (179/2034)

-2.87 (-4.32, -1.41)

Pre-op Hematocrit, Mean ± SD

41.75 ± 3.88

41.89 ± 3.69

41.50 ± 4.18

0.39 (0.17, 0.62]

 < .001

Surgical Duration, min, Mean ± SD

83.02 ± 29.42

79.65 ± 23.57

88.88 ± 36.77

-9.23 (-11.00,-7.45)

 < .001

Hypertension, % (n)

57.05 (3180/5574)

55.34 (1959/3540)

60.03 (1221/2034)

-4.69 (-7.38, -2.00)

 < .001

Diabetes, % (n)

14.46 (806/5574)

13.33 (472/3540)

16.42 (334/2034)

-3.09 (-5.05, -1.13)

0.002

Congestive Heart Failure, % (n)

0.07 (4/5574)

0.06 (2/3540)

0.10 (2/2034)

-0.04 (-0.20, 0.12)

0.57

Bleeding disorder, % (n)

1.38 (77/5574)

1.07 (38/3540)

1.92 (39/2034)

-0.84 (-1.53, -0.16)

0.009

COPD, % (n)

2.15 (120/5574)

1.75 (62/3540)

2.85 (58/2034)

-1.10 (-1.94, -0.26)

0.006