Influence of day of surgery and prediction of LOS > 2 days after fast-track hip and knee replacement

Figures & data

Figure 1. Study population. THA – total hip arthroplasty, TKA – total knee arthroplasty.

Table 1. Patient characteristics Values are count (%) unless otherwise specified

Factor	n (%)
Age median (IQR)	70 (14)
< 50	514 (4.9)
50–60	1,671 (16)
61–65	1,384 (13)
66–70	2,055 (19)
71–75	2,218 (21)
76–80	1,639 (16)
81–85	806 (7.6)
> 85	289 (2.7)
BMI median (IQR)	27.4 (6.5)
< 18.5	94 (0.9)
18.5–24.9	4,110 (39)
25–29.9	2,968 (28)
30–34.9	2,237 (21)
35–39.9	788 (7.5)
> 39.9	279 (2.7)
Missing	100 (0.9)
Female sex	6,213 (59)
Walking aid	2,391 (23)
Missing	195 (1.8)
Living alone	3,632 (35)
In institution	75 (0.7)
Missing	80 (0.8)
Smoking	1,347 (13)
Missing	89 (0.8)
Alcohol > 24 g/day	790 (7.5)
Missing	91 (0.9)
Total knee arthroplasty	4,448 (42)
Psychiatric disease	1,520 (14)
Missing	0 (0.0)
Cardiac disease	1,439 (14)
Missing	106 (1.0)
Pulmonary disease	945 (9.0)
Missing	64 (0.6)
Hypertension	5,911 (56)
Missing	0 (0.0)
Diabetes mellitus
Non-insulin dependent	912 (8.8)
Insulin dependent	199 (1.9)
Missing	61 (0.6)
Anticoagulants	821 (7.8)
Missing	0 (0.0)
Preoperative anemia ^a	2,522 (24)
Missing	155 (1.5)

^a Hemoglobin < 13 g/dL.

Figure 2. Distribution of procedures and day of discharge according to weekday. There were 11 (0.1%) procedures on Saturday and Sunday, all in patients with < 6 points.

Table 2. Multiple-regression analysis of risk factors (n = 9,987) for LOS > 2 days and attributed risk-score points

Variable	OR (95%CI)	p-value	points
Weekday of surgery
Monday	1 (ref.)	–
Tuesday	1.0 (0.9–1.2)	1.0
Wednesday	0.9 (0.7–1.0)	0.08
Thursday	0.9 (0.8–1.1)	0.4
Friday	1.5 (1.2–2.0)	< 0.01
Saturday	2.9 (0.3–30.5)	0.4
Sunday	1.4 (0.2–13.6)	0.8
Age group
< 50	1.3 (0.9–1.8)	0.08
50–60	1.2 (0.9–1.4)	0.1
61–65	1.0 (0.8–1.3)	0.9
66–70	1 (ref.)	–
71–75	1.2 (1.0–1.4)	0.1
76–80	1.4 (1.2–1.7)	< 0.01	1
81–85	2.0 (1.6–2.5)	< 0.01	2
> 85	3.4 (2.5–4.6)	< 0.01	3
BMI
< 18.5	1.6 (1.0–2.6)	0.07	0
18.5–24.9	1 (ref.)	–
25–29.9	1.0 (0.8–1.1)	0.7	0
30–34.9	1.0 (0.9–1.2)	1.0	0
35–39.9	1.2 (0.9–1.5)	0.2	0
> 39.9	1.3 (0.9–1.8)	0.1
Female sex	1.3 (1.2–1.5)	< 0.01	1
Walking aid	1.9 (1.7–2.3)	< 0.01	2
Living alone	1.6 (1.4–1.8)	< 0.01	1
Smoking	1.1 (0.9–1.3)	0.5	0
Alcohol > 24 g/day	0.8 (0.6–1.0)	0.06	0
Total knee arthroplasty	1.9 (1.7–2.1)	< 0.01	1
Psychiatric disease	1.6 (1.4–1.9)	< 0.01	1
Cardiac disease	1.2 (1.0–1.4)	0.04	1
Pulmonary disease	1.3 (1.1–1.6)	< 0.01	1
Hypertension	1.0 (0.9–1.1)	0.8	0
Diabetes mellitus
Non-insulin dependent	1.3 (1.1–1.6)	0.02	1
Insulin dependent	2.0 (1.4–2.9)	< 0.01	2
Anticoagulants	1.2 (1.0–1.5)	0.09	0
Preoperative anemia ^a	1.5 (1.3–1.7)	< 0.01	1

OR: odds ratio. CI: confidence interval.

^a Hemoglobin < 13 g/dL.

Figure 3. Distribution of patients with length of stay (LOS) > 2 days and < 3 days according to number of points based on odds ratios of relevant risk factors for LOS > 2 days.

Figure 4. Distribution of procedures on each weekday according to number of points for LOS > 2 days.

Table 3. Distribution of points depending on number of risk factors for LOS > 2 days

Number of points	n (%)
0	898 (8.9)
1	1,278 (13)
2	1,759 (17)
3	1,902 (19)
4	1,497 (15)
5	1,107 (11)
6	727 (7.2)
7	449 (4.4)
8	293 (2.9)
9	134 (1.3)
10	68 (0.7)
11	14 (0.1)
12	3 (0.0)
13	0 (0)
14	0 (0)
15	0 (0)

N = 10,129 due to 447 cases with missing data for variables associated with LOS > 2 days (see Table 1).