Prosthesis survival after revision knee arthroplasty for “pain without loosening” versus “aseptic loosening”: a Danish nationwide study

Figures & data

Table 1. Characteristics of TKA revisions for 2 selected indications between 1997 and 2018. Values are count (%) unless otherwise specified

	Pain without loosening
	without other	with other	Aseptic
	indications	indications	loosening	Total
TKA revisions	1,111 (26)	674 (16)	2,514 (58)	4,299 (100)
Female sex	709 (64)	428 (63)	1,533 (61)	2,670 (62)
Mean age at 1st revision (range)	63 (29–92)	65 (32–88)	66 (22–96)	65 (22–96)
Age groups
≥ 80 years	60 (5)	62 (9)	259 (11)	381 (9)
70–79 years	275 (25)	200 (30)	736 (29)	1,211 (28)
60–69 years	362 (33)	217 (32)	882 (35)	1,461 (34)
50–59 years	277 (25)	137 (20)	486 (19)	900 (21)
< 50 years	137 (12)	58 (9)	151 (6)	346 (8)
Mean age at primary knee arthroplasty (CI)
	60 (60–61)	62 (61–63)	62 (61–62)	61 (61–62)
Charlson Comorbidity Index
0 (low risk)	839 (76)	508 (76)	1,513 (60)	2,860 (66)
1–2 (medium risk)	239 (21)	137 (20)	812 (32)	1,188 (28)
≥ 3 (high risk)	33 (3)	29 (4)	189 (8)	251 (6)
Surgical subgroups
1. Total revision TKA–TKA	365 (33)	283 (42)	1,649 (66)	2,297 (53)
2. Partial revision	127 (11)	67 (10)	480 (19)	674 (16)
4. UKA–TKA	477 (43)	140 (21)	385 (5)	1,002 (23)
5. Secondary patellar button	142 (13)	184 (27)	–	326 (8)
Total number of re-revisions	252 (23)	128 (19)	476 (19)	856 (20)
Years from 1st to 2nd revision (CI)	3.4 (2.9–3.8)	4.5 (3.8–5.3)	2.9 (2.6–3.2)	3.3 (3.1–3.6)

TKA = total knee arthroplasty; UKA = unicompartmental knee arthroplasty.

Figure 1. Flowchart of TKA revision cases identified and included in the study analysis.

Figure 2. Incidence of TKA revision surgery for indications of “pain without loosening” with and without other indications and “aseptic loosening” without other indications. Data source = Danish Knee Arthroplasty Register, 1997–2018.

Figure 3. Kaplan–Meier survival curves with 95% confidence interval for the indications “pain without loosening” (without other indications) and “aseptic loosening” (without other indications).

Table 3. Cumulated proportion of TKA re-revision after 2, 5, 10, 15, and 20 years by surgical indication. Values are count and percentage (CI)

Indication	n	2 years	5 years	10 years	15 years	20 years
“Pain without loosening” without other indications	1,111	12 (10–14)	18 (16–20)	21 (19–23)	23 (20–25)	23 (20–25)
“Pain without loosening” with other indications	674	9 (7–11)	12 (10–15)	17 (14–20)	19 (16–22)	19 (16–22)
Aseptic loosening without other indications	2,514	11 (9–12)	16 (14–17)	18 (17–20)	19 (17–20)	19 (18–21)

Table 4. Cumulated proportion of TKA re-revision after 2, 5, 10, 15, and 20 years by surgical subgroup and indications of “pain without loosening” (without other indications) and “aseptic loosening” (without other indications). Values are count and percentage (CI)

Subgroup	n	2 years	5 years	10 years	15 years	20 years
1: TKA–TKA	2,014
“Pain”		11 (8–15)	16 (12–20)	19 (15–23)	20 (16–24)	20 (16–24)
“Aseptic loosening”		9 (8–10)	14 (12–15)	15 (14–17)	16 (14–18)	16 (15–18)
2: Partial revision	607
“Pain”		14 (9–21)	20 (14–28)	24 (17–32)	26 (19–34)	27 (20–35)
“Aseptic loosening”		14 (11–17)	22 (19–26)	27 (23–31)	28 (24–32)	28 (24–32)
4: UKA–TKA	862
“Pain”		12 (10–16)	19 (16–23)	22 (18–26)	24 (20–28)	24 (20–28)
“Aseptic loosening”		13 (10–17)	17 (14–21)	19 (16–24)	19 (16–24)	20 (16–24)
5: Secondary patellar button	142
“Pain”		9 (5–14)	18 (12–25)	21 (15–29)	23 (16–30)	23 (16–30)
“Aseptic loosening”		–	–	–	–	–

TKA = total knee arthroplasty; UKA = unicompartmental knee arthroplasty.

Table 5. Risk of re-revision for secondary covariates adjusted for the effect of the primary exposure “indication”, calculated by Cox regression

Risk factor	Hazard ratio (95% CI)	p–value
Male sex	1.2 (1.06–1.4)	0.01
Female sex	1 reference
≥ 80 years	0.51 (0.34–0.75)	0.001
70–79 years	0.73 (0.59–0.90)	0.003
60–69 years	1 reference
50–59 years	1.3 (1.1–1.6)	0.01
≤ 50 years	1.9 (1.5–2.4)	< 0.001
CCI = 0	1 reference
CCI = 1–2	0.96 (0.8–1.2)	0.7
CCI ≥ 3	1.3 (0.87–1.9)	0.2
Subgroup 1: TKA–TKA	1 reference
Subgroup 2: Partial revision	1.5 (1.3–1.8)	< 0.001
Subgroup 4: UKA–TKA	1.1 (0.93–1.4)	0.2

CI = confidence interval; CCI = Charlson Comorbidity Index; TKA = total knee arthroplasty; UKA = unicompartmental knee arthroplasty.

Table 6. Cumulated proportion of TKA re-revision in 2 time-periods after 2, 5, and 8 years. Values are count and percentage (CI)

Indication	n	2 years	5 years	8 years
1997–2009
“Pain without loosening”	533	11 (9–14)	18 (15–22)	22 (19–26)
“Aseptic loosening”	1,023	12 (10–14)	19 (17–21)	22 (20–25)
2010–2018
“Pain without loosening”	578	12 (10–15)	18 (15–21)	18 (15–22)
“Aseptic loosening”	1,491	10 (8–11)	14 (12–15)	14 (13–16)

Figure 4. Kaplan-Meier curves over 2 time-periods for the indications “pain without loosening” (without other indications) and “aseptic loosening” (without other indications). Aseptic loosening 1997–2009 reference (HR 1); Aseptic loosening 2010–2018: HR 0.87 (CI 0.72–1.04), p = 0.1; Pain 1997–2009: HR 1.06 (CI 0.87–1.30), p = 0.6; Pain 2010–2018: HR 1.19 (CI 0.88–1.62), p = 0.3.

Table 7. Cumulated proportions of re-revision in 2 time-periods by subgroups and indications “pain without loosening” and “aseptic loosening” without any other indications. Values are count and percentage (CI)

Indication and subgroup	n	2 years	5 years	8 years
1997–2009	1,556
	Subgroup 1 (TKA–TKA)	819
	“Pain without loosening”		12 (7–18)	18 (12–25)	23 (17–31)
	“Aseptic loosening”		11 (9–13)	17 (14–20)	20 (17–23)
	Subgroup 2 (partial revision)	262
	“Pain without loosening”		15 (8–27)	20 (12–33)	27 (18–40)
	“Aseptic loosening”		12 (8–17)	25 (20–32)	29 (23–35)
	Subgroup 4 (UKA–TKA)	382
	“Pain without loosening”		10 (7–14)	18 (13–23)	21 (16–26)
	“Aseptic loosening”		15 (10–22)	18 (13–26)	21 (15–29)
	Subgroup 5 (secondary patellar button)	93
	“Pain without loosening”		11 (6–19)	18 (12–28)	20 (13–30)
	“Aseptic loosening”		–	–	–
2010–2018	2,069
	Subgroup 1 (TKA–TKA)	1,195
	“Pain without loosening”		11 (7–15)	14 (10–20)	15 (11–20)
	“Aseptic loosening”		8 (6–9)	11 (9–13)	12 (10–14)
	Subgroup 2 (partial revision)	345
	“Pain without loosening”		13 (7–24)	19 (11–30)	19 (11–30)
	“Aseptic loosening”		15 (11–20)	20 (16–25)	22 (18–28)
	Subgroup 4 (UKA–TKA)	480
	“Pain without loosening”		15 (11–20)	20 (16–26)	21 (16–27)
	“Aseptic loosening”		12 (9–17)	17 (12–22)	17 (13–22)
	Subgroup 5 (Secondary patellar button)	49
	“Pain without loosening”		4 (1–15)	16 (8–30)	18 (10–32)
	“Aseptic loosening”		–	–	–

TK = total knee arthroplasty; UKA = unicompartmental knee arthroplasty.

Table 8. Reasons for re-revision for knee arthroplasties primarily revised for respectively “pain without loosening” and “aseptic loosening”. Values are count and percentage with [CI] in parentheses

	Indication for primary revision
	Pain without	Aseptic
	loosening	loosening
Indication for re-revision	n = 252	n = 476
1. Aseptic loosening	78 (31 [26–37])	159 (33 [29–38])
2. Pain without loosening	40 (16 [12–21])	57 (12 [9–15])
3. Instability	70 (28 [23–34])	99 (21 [17–25])
4. Infection	15 (6 [4–10])	57 (12 [9–15])
5. Secondary patellar button	14 (6 [3–9])	18 (4 [2–6])
6. Polyethylene failure	6 (2 [1–5)	14 (3 [2–5])
Unknown indication	29 (11 [8–16])	72 (15 [12–19])

Supplementary data