RISK FACTORS FOR EARLY HOSPITAL READMISSION FOLLOWING TOTAL KNEE ARTHROPLASTY

Using the ACS-NSQIP database, we identified patients who underwent primary TKA from 2012-2015. The primary outcome was early hospital readmission. Patient demographics, preoperative comorbidities, laboratory data, operative characteristics, and postoperative complications were compared between readmitted and non-readmitted patients. Logistic regression identified independent risk factors for 30-day readmission.

Results:

137,209 patients underwent TKA; 3.4% were readmitted within 30 days. Advanced age, male sex, black ethnicity, morbid obesity, presence of preoperative comorbidities, high ASA classification, and increased operative time were independently related risk factors. Asian and no reported race were negative risk factors. Postoperative complications: acute myocardial infarction, acute renal failure, stroke, pneumonia, pulmonary embolism, and deep vein thrombosis show positive associations.

Conclusions:

Advanced age, male sex, black ethnicity, morbid obesity, presence of comorbidities, high ASA classification and long operative time are independent risk factors for postoperative complications and early hospital readmission following total knee arthroplasty. Level of Evidence III, Case control study.

Keywords:
Arthroplasty; Knee; Patient readmission; Risk factors

Variable	Not Readmitted^* * Some data points were unrecorded and were therefore unavailable for inclusion in the evaluation. (N= 132,541)	Readmitted^* * Some data points were unrecorded and were therefore unavailable for inclusion in the evaluation. (N=4,668)	P Value	Variable	Not Readmitted^* * Some data points were unrecorded and were therefore unavailable for inclusion in the evaluation. (N= 132,541)	Readmitted^* * Some data points were unrecorded and were therefore unavailable for inclusion in the evaluation. (N=4,668)	P Value
Variable	Age^¥ ¥ The values given represent the average age of patients, in years.	66.53	P Value	Variable	68.49	<0.0001	P Value	Pre-op blood transfusion	67 (0.1%)	7 (0.2%)	0.004
Sex ^ȣ ȣ The values are given as a number of patients, with the percentage in parentheses.			<0.0001	Open / infected wound	325 (0.3%)	35 (0.8%)	<0.0001
Male	49,856 (37.6%)	2,039 (43.7%)		Systemic Sepsis			0.16
Female	82,685 (62.4 %)	2,629 (56.3%)		SIRS	241 (0.2%)	15 (0.3%)
Race ^ȣ ȣ The values are given as a number of patients, with the percentage in parentheses.			<0.0001	Septic Shock	5 (0.0%)	0 (0.0%)
White	103,659 (78.2 %)	3,691 (79.1%)		Sepsis	5 (0.0%)	0 (0.0%)
Black	9,567 (7.2%)	440 (9.4%)		Corticosteroid use	4,675 (3.5%)	260 (5.6%)	<0.0001
Asian	2,845 (2.2%)	63 (1.4%)		Preoperative Labs
American Indian	711 (0.5%)	15 (0.3%)		WBC count (X10³ / L)	7.05 (2.75 – 11.35)	7.26 (1.64 – 12.88)	<0.0001
Native Hawaiian	418 (0.3%)	9 (0.2%)		Hematocrit (%)	40.82 (32.74 – 48.9)	40.29 (31.51 – 49.07)	<0.0001
Unreported	15,341 (11.6%)	450 (9.6%)		Platelets (X10³ / L)	244.12 (111.52 – 376.72)	239.44 (97.78 – 381.1)	<0.0001
BMI Category^ȣ ȣ The values are given as a number of patients, with the percentage in parentheses.			<0.0001	Creatinine (mg/dL)	0.91 (0.11 – 1.71)	1.01 (0.21 – 1.81)	<0.0001
Underweight (<18.5)	287 (0.2%)	10 (0.2%)		Serum albumin (g/dL)	4.10 (3.34 – 4.86)	4.02 (3.2 – 4.84)	<0.0001
Normal (18.5 – 25)	12,938 (9.8%)	466 (10.0%)		INR	1.02 (0.52 – 1.52)	1.06 (0.56 – 1.56)	<0.0001
Overweight (25 – 30)	35,731 (27.0%)	1,211(26.0%)		Operative Variables
Obese (35 – 35)	37,746 (28.6%)	1,246 (26.8%)		ASA class^ȣ ȣ The values are given as a number of patients, with the percentage in parentheses.			<0.0001
Very obese (35 – 40)	25,312 (19.2%)	824 (17.7%)		1	2,837 (2.1%)	66 (1.4%)
Morbid Obese (≥ 40)	20,186(15.3%)	894 (19.2%)		2	67,123 (50.6%)	1,683 (36.1%)
Comorbid Conditions ^ȣ ȣ The values are given as a number of patients, with the percentage in parentheses.				3	60,447 (45.6%)	2,745 (55.8%)
Recent weight loss	146 (0.1%)	6 (0.1%)	0.711	4	2,025 (1.5%)	169 (3.3%)
Smoking	11,401 (8.6%)	482 (10.3%)	<0.0001	5	4 (0.00%)	0 (0.00%)
Diabetes			<0.0001	Not assigned	105 (0.08%)	5 (0.11%)
Insulin-dependent	5,759 (4.4%)	345 (7.4%)		Operation time^# # The values given represent an average, with 1 standard deviation in parentheses. (min)	93.59 (55.24 – 131.94)	97.78 (53.78 – 141.78)	<0.0001
Non-insulin	17,830 (13.5%)	706 (15.1%)		Anesthesia technique⁸8. SooHoo NF, Lieberman JR, Ko CY, Zingmond DS. Factors predicting complication rates following total knee replacement. J Bone Joint Surg Am. 2006;88(3):480-5.			<0.0001
Dialysis Use	197 (0.2%)	22 (0.5%)	<0.0001	General	67,722 (51.1%)	2,563 (54.9%)
Hypertension	86,387 (65.2%)	3,460 (74.1%)	<0.0001	Neuraxial	51,743 (39.0%)	1,685 (36.1%)
CHF	336 (0.3%)	44 (0.9%)	<0.0001	Regional	2,644 (2.0%)	83 (1.8%)
Dyspnea	7,821 (5.9%)	456 (9.8%)	<0.0001	MAC or IV sedation	10,235 (7.7%)	327 (7.0%)
COPD	4,605 (3.5%)	373 (8.0%)	<0.0001	Local	38 (0.0%)	0 (0.0%)
Bleeding disorder	3,022 (2.3%)	241 (5.2%)	<0.0001	Days to discharge^# # The values given represent an average, with 1 standard deviation in parentheses.	2.99 (2.16)	3.36 (2.13)	<0.0001

Variable	Odds Ratio (95% CI) ^¥ ¥ The values are given as the odds ratio, with the 95% CI in parentheses. ^ǂ ǂ Logistic regression modeling adjusted for age, sex, race, BMI category, and presence of one of more preoperative comorbidities, ASA class, and operative time.	P value ^ǂ ǂ Logistic regression modeling adjusted for age, sex, race, BMI category, and presence of one of more preoperative comorbidities, ASA class, and operative time.
Preoperative Characteristics
Age (per year)	1.021 (1.018 to 1.025)	<0.0001
Sex female vs male	0.78 (0.73 to 0.83)	<0.0001
Race
Black vs White	1.24 (1.11 to 1.37)	<0.0001
Asian vs White	0.62 (0.48 to 0.80)	0.0002
Native Hawaiian vs White	0.58 (0.30 to 1.13)	0.1118
American Indian vs White	0.60 (0.36 to 1.00)	0.0514
Non reported vs White	0.87 (0.78 to 0.96)	0.0048
BMI Category
Underweight vs Overweight	1.06 (0.56 to 1.99)	0.8670
Normal vs Overweight	1.11 (0.99 to 1.23)	0.0750
Obese vs Overweight	0.96 (0.88 to 1.04)	0.2742
Very obese vs Overweight	0.92 (0.84 to 1.01)	0.0715
Morbidly Obese vs Overweight	1.20 (1.08 to 1.32)	0.0003
Comorbidities	1.29 (1.25 to 1.34)	<0.0001
Operative variables
ASA class
1- No disturb vs 2 -Mild Disturb	1.19 (0.93 to 1.53)	0.1705
3- Severe Disturb vs 2 -Mild Disturb	1.43 (1.34 to 1.53)	<0.0001
4- Life Threat vs 2 -Mild Disturb	2.06 (1.73 to 2.44)	<0.0001
Non Assigned vs 2 -Mild Disturb	1.75 (0.71 to 4.32)	0.2225
Operation time (per min)	1.002 (1.002 to 1.003)	<0.0001

	Not Readmitted^* * Some data points were unrecorded and were therefore unavailable for inclusion in the evaluation. ^ȣ ȣ The value are given as a number of patients, with the percentage in parentheses. (N=132,541)	Readmitted^* * Some data points were unrecorded and were therefore unavailable for inclusion in the evaluation. ^ȣ ȣ The value are given as a number of patients, with the percentage in parentheses. (N=4,668)	P Value ^¶ ¶ P value from univariate modeling.	Odds Ratio (95% CI) ^¥ ¥ The values are given as the odds ratio, with the 95% CI in parentheses. ^ǂ ǂ Logistic regression modeling adjusted for age, sex, race, and presence of one of more preoperative comorbidities, ASA class, and operative time. Not adjusted for concurrent medical or surgical complications.	P Value ^ǂ ǂ Logistic regression modeling adjusted for age, sex, race, and presence of one of more preoperative comorbidities, ASA class, and operative time. Not adjusted for concurrent medical or surgical complications.
Overall complications	13,835 (10.4%)	6,143 (58.0%)	<0.0001
Medical complications	11,753 (8.9%)	1,513 (32.4%)	<0.0001
Pneumonia	327 (0.3%)	176 (3.8%)	<0.0001	12.15 (10.04 to 14.71)	<0.0001
Unplanned intubation	138 (0.1%)	66 (1.4%)	<0.0001	9.94 (7.35 to 13.46)	< 0.0001
Urinary tract infection	975 (0.7%)	225 (4.8%)	<0.0001	6.22 (5.34 to 7.23)	<.0.0001
Ventilator for more than 48 hours	62 (0.1%)	35 (0.8%)	<0.0001	11.16 (7.28 to 17.09)	<.0.0001
Stroke or cerebrovascular accident	72 (0.1%)	37 (0.8%)	<0.0001	12.18 (8.11 to 18.28)	<.0.0001
Acute renal failure	41 (0.0%)	33 (0.7%)	<0.0001	15.26 (9.50 to 24.52)	<.0.0001
Cardiac arrest	81 (0.1%)	30 (0.6%)	<0.0001	7.68 (5.00 to 11.81)	<.0.0001
Septic Shock	32 (0.0%)	57 (1.2%)	<0.0001
Sepsis	67 (0.1%)	191 (4.1%)	<0.0001
Myocardial infarction (MI)	152 (0.1%)	125 (2.7%)	<0.0001	18.48 (14.47 to 23.58)	<.0.0001
Blood transfusion	9,806 (7.4%)	538 (11.5%)	<0.0001	1.41 (1.28 to 1.55)	<.0.0001
Surgical complications	2,082 (1.6%)	1,195 (25.6%)	<0.0001
Superficial surgical site infection	481 (0.4%)	224 (4.8%)	<0.0001	13.53 (11.46 to 15.98)	<.0.0001
Deep or incisional surgical site infection	49 (0.0%)	164 (3.5%)	<0.0001
Organ or space surgical site infections	26 (0.0%)	179 (3.8%)	<0.0001
Pulmonary embolism	613 (0.5%)	319 (6.8%)	<0.0001	16.45 (14.27 to 18.96)	<.0.0001
Deep venous thrombosis	913 (0.7%)	309 (6.6%)	<0.0001	10.32 (9.02 to 11.82)	<.0.0001

ATHA EDITORA Rua: Machado Bittencourt, 190, 4º andar - Vila Mariana - São Paulo Capital - CEP 04044-000, Telefone: 55-11-5087-9502 - São Paulo - SP - Brazil
E-mail: actaortopedicabrasileira@uol.com.br

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[1] Correspondence: Rua Dr. Ovídio Pires de Campos, 333, Cerqueira Cesar, São Paulo, SP, Brazil. 04503-010. alexandrelemegodoy@gmail.com.br