Table 2 Results of comparison between same-stage and two-stage ‘young and fit’ subgroup (non-obese, non-complex, ASA 1 or 2, age < 75 years)

Gender and number

26 M, 69 F

6 M, 16 F

Age

65.6 (51–77, SD 5.31, 95% CI 64.5–66.7)

66.1 (56–74, SD 4.94, 95% CI 64–68.2)

ASA grade

1: 5, 5.26%,

1: 3, 13.64%

2: 90, 94.74%

2: 19, 86.36%

3: 0, 0%

3: 0, 0%

FS

50.3 (5–80, SD 12.99,

50.1 (5–90, SD 18.64,

95% CI 47.7–52.9)

95% CI 42.3–57.9)

KS

44.3 (18–79, SD 13.54,

44.7 (12–74, SD 12.97,

95% CI 41.6–47)

95% CI 39.3–50.1)

OKS

24.9 (8–54, SD 6.69,

25.3 (6–54, SD 8.41,

95% CI 23.5–26.3)

95% CI 21.5–28.5)

ALOS (Days)

6.64 (3–12, SD 2.13,

11.29^a (7–15, SD 1.55,

95% CI 6.21–7.07)

95% CI 10.6–11.9)

HbDrop (g/dL)

3.03 (0.0–6.0, SD 1.21,

2.20 (− 0.1–6.2, SD 1.02,

95% CI 2.19–3.27)

95% CI 1.77–2.63)

TV (units) for 2 knees

0.18 (0–6, SD 1.21,

0.10 (0–4, SD 1.02,

95% CI − 0.063–0.42)

95% CI − 0.36–0.53)

Transfusion percentage

8.42% (16 of 190 knees)

9.09% (4 of 44 knees)

RR

3.16% (6 of 190 knees)

6.81% (3 of 44 knees)

Surg CR

3.68% (7 of 190 knees)

9.09% (4 in 44 knees)

Med CR

10.5% (10 of 95 operations)

4.55% (2 of 44 operations)