Influence of body mass index and age on day-of-surgery discharge, prolonged admission, and 90-day readmission after fast-track unicompartmental knee arthroplasty

Figures & data

Table 3. Distribution of BMI and age groups among all included patients (N = 3,897). Values are count (%) unless otherwise specified

BMI, n	3,897
Median [IQR]		28 [25–32]
Normal: < 25	840 (22)
Overweight: 25.0–29.9	1,677 (43)
Obese: 30.0–34.9	996 (26)
Very obese: 35.0–39.9	294 (7.5)
Morbidly obese ≥ 40	90 (2.3)
Age, n	3,897
Mean (SD) [range]		66 (9.4) [26–97]
< 50	168 (4.3)
50–60	901 (23)
61–70	1,441 (37)
71–80	1,198 (31)
> 80	189 (4.9)

Table 4. Unadjusted analyses of difference in DOS discharge, LOS >2 days and 90-day readmission between BMI groups

	DOS discharge		LOS > 2 days		90-day readmission
BMI groups (n = 3,897)	n (%) [95%CI]	p-value	n (%) [95%CI]	p-value	n (%) [95%CI]	p-value
Normal: < 25	220 (26) [23–29]	Ref.	62 (7.4) [5.6–9.2]	Ref.	54 (6.4) [4.8–8.1]	Ref.
Overweight: 25.0–29.9	423 (25) [23–27]	0.6	112 (6.7) [5.5–7.9]	0.5	107 (6.4) [5.2–7.6]	1.0
Obese: 30.0–34.9	257 (26) [23–29)	0.9	80 (8.0) [6.3–9.7)	0.6	65 (6.5) [5.0–8.1)	0.9
Very obese: 35.0–39.9	72 (25) [20–29]	0.6	23 (7.8) [4.8–11]	0.8	32 (11) [7.3–14]	0.01
Morbidly obese ≥ 40	20 (22) [14–31]	0.4	15 (17) [9.0–24]	0.002	11 (12) [5.5–19]	0.04

DOS = day of surgery. Ref. = reference group. LOS = length of stay.

Table 5. Unadjusted analyses of difference in DOS discharge, LOS >2 days and 90-day readmission between age groups

	DOS discharge		LOS > 2 days		90-day readmission
Age groups (n = 3,897)	n (%) [95%CI]	p-value	n (%) [95%CI]	p-value	n (%) [95%CI]	p-value
< 50	47 (28) [21–35]	1.0	15 (8.9) [4.6–13]	0.3	10 (6.0) [2.4–9.5]	0.9
50–60	276 (31) [28–34]	0.2	66 (7.3) [5.6–9.0]	0.7	48 (5.3) [3.9–6.8]	0.7
61–70	406 (28) [26–31]	Ref.	100 (6.9) [5.6–8.3]	Ref.	82 (5.7) [4.5–6.9]	Ref.
71–80	249 (21) [19–23]	<0.001	89 (7.4) [5.9–8.9]	0.6	108 (9.0) [7.4–11]	0.001
> 80	14 (7.4) [3.7–11]	<0.001	22 (12) [7.1–16]	0.02	21 (11) [6.6–16]	0.004

DOS = day of surgery. Ref. = reference group. LOS = length of stay.

Table 6. Adjusted analysis of occurrence of DOS discharge, LOS > 2 days and 90-day readmission in age groups

Age groups (n = 3,596)	DOS discharge	LOS > 2 days	90-day readmission
	OR (95% CI)	OR (95% CI)	OR (95% CI)
< 50	0.85 (0.55–1.3)	1.2 (0.68–2.3)	1.2 (0.59–2.6)
50–60	1.3 (1.0–1.6)	1.2 (0.83–1.7)	1.0 (0.70–1.6)
61–70	Ref.	Ref.	Ref.
71–80	0.71 (0.58–0.88)	0.95 (0.69–1.3)	1.5 (1.1–2.1)
> 80	0.18 (0.10–0.34)	1.3 (0.73–2.2)	1.6 (0.89–2.8)

DOS = day of surgery. Ref. = reference group. LOS = length of stay. OR = odds-ratio.

Table 7. Adjusted analysis of occurrence of DOS discharge, LOS > 2 days and 90-day readmission in BMI groups

BMI groups (n = 3,596)	DOS discharge	LOS > 2 days	90-day readmission
	OR (95% CI)	OR (95% CI)	OR (95% CI)
Normal: < 25	Ref.	Ref.	Ref.
Overweight: 25.0–29.9	0.96 (0.76–1.2)	0.97 (0.69–1.4)	1.0 (0.73–1.5)
Obese: 30.0–34.9	1.0 (0.78–1.3)	1.1 (0.76–1.6)	0.99 (0.65–1.5)
Very obese: 35.0–39.9	0.91 (0.62–1.3)	1.0 (0.60–1.8)	1.9 (1.1–3.1)
Morbidly obese ≥ 40	1.1 (0.59–2.0)	1.5 (0.71–3.0)	2.1 (0.98–4.5)

DOS = day of surgery. Ref. = reference group. LOS = length of stay. OR = odds-ratio.