Resource utilization and costs for robotic-assisted and manual total knee arthroplasty – a premier healthcare database study

Figures & data

Figure 1. Attrition flow diagram of patients included in the analysis.

Table 1. Baseline characteristics of patients undergoing rTKA and mTKA surgery before and after DM-PSM.

	Before DM-PSM			After DM-PSM
Patient Characteristics	rTKA	mTKA	Standardized Differences	rTKA	mTKA	Standardized Differences
N	25,206	688,315		16,714	51,199
Age in years, N(%)
18–54	10.9	9.7	0.072	9.1	9.1	0
55–64	30.3	28.2		30.3	30.3
65–74	38.7	40.2		40.1	40.1
75 plus	20.1	21.9		20.5	20.5
Gender, %
Males	40.1	38.4	0.035	39.4	40.2	0.016
Race, %
White	83.5	83.1	0.016	87.9	87.9	0
Black	8.3	8.7		6.4	6.4
Asian	1.4	1.3		0.8	0.8
Other	6.9	6.9		4.9	4.9
Marital Status, %
Married	61.9	59.6	0.047	64.7	60.8	0.083
Single	30.9	32.9		29.3	32.2
Other or Unknown	7.2	7.5		6.0	7.0
Payor category, %
Medicare	56.0	60.8	0.112	57.1	58.7	0.056
Commercial	34.8	30.6		35.1	32.8
Medicaid	3.7	4.2		2.7	3.3
Other	5.4	4.4		5.1	5.2
Patient Type, %
Inpatient	87.4	82.1	0.147	86.4	87.1	0.021
Year of TKA surgery, %
2015	1.5	5.6	0.755	1.9	1.9	0
2016	5.1	20.9		6.6	6.6
2017	9.5	20.6		11.8	11.8
2018	19.4	18.0		20.8	20.8
2019	29.3	17.6		29.1	29.1
2020	24.3	12.4		22.8	22.8
2021	10.8	4.9		7.1	7.1
Additional Comorbidities, %
Arthritis	99.5	97.6	0.163	99.4	99.0	0.050
Smoking	31.4	31.4	0.001	31.1	31.7	0.013
Knee pain	10.0	7.2	0.099	8.3	7.8	0.018
Osteoporosis	4.3	4.1	0.009	4.6	4.1	0.024
Back pain	3.4	3.4	0.003	3.3	3.4	0.003
Functional Comorbidity Index, %
0–2	32.2	31.9	0.005	32.6	32.1	0.013
4-Mar	44.5	44.7		45.0	45.6
5 +	23.3	23.3		22.4	22.2
Elixhauser Comorbidity Index, %
0	13.8	13.1	0.044	12.9	12.9	0
2-Jan	53.0	51.8		55.2	55.2
4-Mar	27.1	28.1		26.8	26.8
5 +	6.2	7.0		5.0	5.0

AIDS, acquired immunodeficiency syndrome; DM-PSM, direct-matching and propensity score-matching; Elix, Elixhauser; FCI, functional comorbidity index; HIV, human immunodeficiency virus; mTKA, manual total knee arthroplasty; rTKA, robotic total knee arthroplasty.

Table 2. Provider characteristics of patients undergoing rTKA and mTKA surgery before and after DM-PSM.

	Before DM-PSM			After DM-PSM
Provider Characteristics	rTKA	mTKA	Standardized Differences	rTKA	mTKA	Standardized Differences
N	25,206	688,315		16,714	51,199
Provider volume annual, %
1–273	44.1	35.1	0.192	41.4	41.4	0
274–479	25.4	27.4		24.5	24.5
480–906	27.4	33.2		31.7	31.7
907 plus	3.1	4.3		2.4	2.4
Urban or Rural, %
Urban	87.5	87.6	0.005	90.0	90.0	0
Teaching, %
Yes	42.2	42.1	0.003	43.6	43.6	0
Beds group, %
000–099	5.2	9.7	0.177	4.9	4.9	0
100–199	19.8	18.5		19.1	19.1
200–299	19.5	19.2		18.2	18.2
300–399	19.4	17.1		21.7	21.7
400–499	11.5	11.8		10.0	10.0
500+	24.5	23.7		26.3	26.3
US Geographic Subdivision, %
East North Central	14.9	17.9	0.503	16.8	16.8	0
East South Central	9.5	9.2		8.4	8.4
Middle Atlantic	15.8	12.1		16.1	16.1
Mountain	6.1	3.9		5.5	5.5
New England	9.0	4.2		6.9	6.9
Pacific	7.0	9.7		7.6	7.6
South Atlantic	18.6	26.1		21.1	21.1
West North Central	1.7	8.3		1.1	1.1
West South Central	17.3	8.6		16.6	16.6
US Census Region, %			0.281			0
Midwest	16.7	26.2		17.9	17.9
Northeast	24.8	16.3		22.9	22.9
South	45.4	43.9		46.1	46.1
West	13.1	13.6		13.0	13.0
Fixation Method, %
Uncemented	24.8	4.1	0.616	12.1	11.8	0.008

DM-PSM, direct-matching and propensity score-matching; mTKA, manual total knee arthroplasty; rTKA, robotic total knee arthroplasty.

Table 3. Healthcare resource utilization and costs for rTKA and mTKA from index surgery through 90 days post-index.

	rTKA	mTKA	Difference:
			rTKA – mTKA
N	16,714	51,199
Index Hospitalization
Length of stay in days, mean (95%CI)	1.598 (1.578 to 1.618)	1.799 (1.787 to 1.812)	−0.2 (−0.22 to −0.17)
Surgical time in mins, mean (95%CI)	153 (152 to 155)	143 (142 to 143)	11 (9 to 13)
Cost of index surgery ($), mean (95%CI)	17,005 (16,906 to 17,104)	16,740 (16,683 to 16,796)	266 (152 to 379)
Operating room cost ($), mean (95%CI)	5,506 (5,465 to 5,547)	4,994 (4,971 to 5,016)	513 (466 to 559)
Room and board cost ($), mean (95%CI)	2,055 (2,022 to 2,088)	2,223 (2,203 to 2,242)	−168 (−206 to −129)
Discharged to home with or without home health agency, %	91.0 (90.5 to 91.5)	88.2 (88 to 88.5)	2.8 (2.2 to 3.3)
Discharged home without home health, %	43.0 (42.2 to 43.7)	38.0 (37.6 to 38.4)	5.0 (4.1 to 5.8)
Discharged to skilled nursing facility or other facility, %	9.0 (8.6 to 9.4)	11.8 (11.5 to 12.1)	−2.8 (−3.3 to −2.3)
Follow-up Period (from Discharge to 90 days post-discharge)
Any hospital revisit*, %	28.7 (28 to 29.3)	29.2 (28.8 to 29.6)	−0.6 (−1.4 to 0.2)
Any inpatient readmission, %	3.4 (3.2 to 3.7)	3.9 (3.7 to 4)	−0.4 (−0.8 to −0.1)
Any ER revisit, %	5.4 (5.1 to 5.8)	6.3 (6.1 to 6.5)	−0.9 (−1.3 to −0.5)
Knee-related hospital revisit*, %	7.0 (6.6 to 7.4)	7.4 (7.2 to 7.6)	−0.4 (−0.8 to 0)
Knee-related inpatient readmission, %	1.8 (1.6 to 2)	2.1 (2 to 2.2)	−0.3 (−0.5 to −0.1)
Costs for any hospital revisit ($), mean (95%CI)	994 (920 to 1,069)	1,127 (1,082 to 1,173)	−133 (−220 to −46)
Cost for any inpatient readmission ($), mean (95%CI)	501 (437 to 565)	590 (550 to 630)	−89 (−165 to −14)
Cost for any ER revisit ($), mean (95%CI)*	44 (40 to 48)	47 (45 to 49)	−3 (−8 to 1)
Costs for knee-related hospital revisit ($), mean (95%CI)	460 (404 to 515)	538 (503 to 572)	−78 (−143 to −13)
Costs for knee-related inpatient readmission ($), mean (95%CI)*	286 (238 to 335)	342 (311 to 372)	−55 (−113 to 2)
Total Inpatient Costs: Including Index and Up to 90 days post-discharge – excluding SNF and home health costs
All care costs ($)*	17,999 (17,868 to 18,131)	17,867 (17,792 to 17,942)	132 (−19 to 284)
Knee-related care costs ($)	17,465 (17,346 to 17,584)	17,277 (17,209 to 17,345)	188 (51 to 325)

Note: Differences were significant (p < 0.05) for all variables except for the ones marked with *

Table 4. Sensitivity analysis for healthcare resource utilization and costs for rTKA and mTKA from index surgery through 90 days post-index*.

	rTKA	mTKA	Difference:
			rTKA – mTKA
N	10,622	31,327
Index Hospitalization
Length of stay in days, mean (95%CI)	1.623 (1.603 to 1.643)	1.825 (1.813 to 1.838)	−0.2 (−0.225 to −0.179)
Surgical time in mins, mean (95%CI)	153 (152 to 155)	144 (143 to 144)	10 (8 to 11)
Cost of index surgery ($), mean (95%CI)*	17,060 (16,958 to 17,162)	17,071 (17,013 to 17,130)	−12 (−129 to 106)
Operating room cost ($), mean (95%CI)	5,502 (5462 to 5542)	5,005 (4983 to 5027)	497 (451 to 543)
Room and board cost ($), mean (95%CI)	2,089 (2056 to 2121)	2,254 (2235 to 2273)	−165 (−203 to −128)
Discharged to home with or without home health agency, %	91 (90.5 to 91.4)	88.2 (87.9 to 88.4)	2.8 (2.3 to 3.3)
Discharged home without home health, %	42.6 (41.8 to 43.3)	37.9 (37.5 to 38.3)	4.6 (3.8 to 5.5)
Discharged to skilled nursing facility or other facility, %	9 (8.6 to 9.5)	11.8 (11.6 to 12.1)	−2.8 (−3.3 to −2.3)
Follow-up Period (from Discharge to 90 days post-discharge)
Any hospital revisit*, %	28.6 (28 to 29.3)	29.2 (28.8 to 29.6)	−0.5 (−1.3 to 0.2)
Any inpatient readmission, %	3.4 (3.2 to 3.7)	4 (3.8 to 4.2)	−0.6 (−0.9 to −0.3)
Any ER revisit, %	5.4 (5.1 to 5.8)	6.3 (6.1 to 6.5)	−0.9 (−1.3 to −0.5)
Knee-related hospital revisit, %	7 (6.6 to 7.3)	7.6 (7.4 to 7.8)	−0.6 (−1.1 to −0.2)
Knee-related inpatient readmission, %	1.8 (1.6 to 2)	2.2 (2.1 to 2.4)	−0.4 (−0.7 to −0.2)
Costs for any hospital revisit ($), mean (95%CI)	983 (910 to 1056)	1,172 (1126 to 1217)	−189 (−275 to −103)
Cost for any inpatient readmission ($), mean (95%CI)	496 (434 to 559)	622 (582 to 662)	−125 (−199 to −52)
Cost for any ER revisit ($), mean (95%CI)*	44 (40 to 48)	47 (45 to 49)	−3 (−7 to 2)
Costs for knee-related hospital revisit ($), mean (95%CI)	453 (401 to 505)	561 (528 to 594)	−108 (−170 to −47)
Costs for knee-related inpatient readmission ($), mean (95%CI)	280 (235 to 325)	360 (331 to 390)	−80 (−134 to −26)
Total Inpatient Costs: Including Index and Up to 90 days post-discharge – excluding SNF and home health costs
All care costs ($)	18,043 (17,909 to 18,176)	18,243 (18,166 to 18,320)	−200 (−354 to −46)
Knee-related care costs ($)*	17,512 (17,392 to 17,633)	17,632 (17,563 to 17,701)	−120 (−259 to 19)

Note: Differences were significant (p < 0.05) for all variables except for the ones marked with *

mTKA, manual total knee arthroplasty; rTKA, robotic total knee arthroplasty.

* Sensitivity analyses involved directly matched on additional variables including congestive heart failure, peripheral vascular disorders, hypertension, uncomplicated diabetes, renal failure, fluid and electrolyte disorders, deficiency anemia, depression, arthritis, osteoporosis and marital status in addition to age categories, Elixhauser comorbidity score, year of surgery, hospital volume, hospital bed size, hospital teaching status, hospital urban or rural location, and geographic subdivision. Patients were matched on other demographic and clinical characteristics based on propensity scores.