Increasing risk of prosthetic joint infection after total hip arthroplasty

Figures & data

Table 1. Patient and procedure characteristics for the primary THAs included, and number of primary THAs excluded over the 3 time periods

	1995-1999	2000-2004	2005-2009	1995-2009
Number of THAs included	113,280	147,823	171,065	432,168
Age (%)
<40 years	2	1	1	1
40–59 years	17	18	17	17
60–69 years	29	29	32	30
70–79 years	38	37	35	36
80–89 years	14	15	15	15
≥90 years	1	1	1	1
Sex (%) Female	63	62	61	61
Diagnosis (%)
Osteoarthritis	76	80	83	80
Hip fracture	10	7	6	8
Inflammatory disease	5	4	2	4
Childhood hip disease	4	4	3	3
Femoral head necrosis	2	2	2	2
Other diagnoses	2	3	3	3
Prosthesis (%)
Monoblock	22	10	2	10
Modular	78	90	98	90
Fixation (%)
Uncemented	13	16	30	21
Cemented	76	71	56	67
Hybrid	10	10	6	9
Inverse hybrid	1	3	8	4
Cement (%)
No????	13	16	30	21
With antibiotics	71	79	69	73
Without antibiotics	15	5	1	6
Country (%)
Denmark	14	20	22	21
Norway	23	21	19	20
Sweden	45	42	41	42
Finland	19	17	18	18
Number of THAs excluded	10,540	3,303	6,169	9,922 (4.4%)

Table 2. Relative risk of revision due to infection of primary THAs in the NARA with 1-16 years of follow-up. Adjusted for age, sex, diagnosis, prosthesis, and cement

	Period	Number of THAs included	Number of THAs revised due to infection	Adjusted risk ratio for revision due to infection	95% confidence interval	p-value
All THAs	1995–1999	113,280	778	1
	2000–2004	147,823	937	1.1	1.0–1.2	0.03
	2005–2009	171,065	1,063	1.6	1.4–1.7	<0.001
Uncemenxted THAs	1995–1999	15,177	87	1
	2000–2004	23,553	147	1.4	1.0–1.8	0.03
	2005–2009	51,445	308	1.9	1.5–2.5	<0.001
Cemented THAs	1995–1999	86,177	538	1
	2000–2004	105,421	641	1.2	1.1–1.3	0.006
	2005–2009	96,455	619	1.7	1.5–2.0	<0.001
Hybrid THAs	1995–1999	11,369	149	1
	2000–2004	15,163	125	0.8	0.6–1.0	0.02
	2005–2009	10,390	63	0.8	0.6–1.1	0.2
Inverse hybrid THAs	1995–1999	556	4	1
	2000–2004	3,685	24	1.3	0.4–4.0	0.6
	2005–2009	12,775	73	1.6	0.5–4.6	0.4
Cemented modular THAs with antibiotics in cement inserted due to OA ^a	1995–1999	37,848	208	1
	2000–2004	69,052	374	1.1	0.9–1.3	0.2
	2005–2009	75,929	467	1.7	1.4–2.0	<0.001

^a Adjusted for age and sex.

Figure 1. Adjusted cumulative revision rates for THAs revised due to infection in 3 time periods of primary surgery, for all THAs (upper left panel) and 5 subgroups of THAs. Adjusted for age, sex, diagnosis, prosthesis, and cement. *Adjusted for age and sex only.

Figure 2. Graphical display of the relationship between year of primary surgery and relative risk of revision due to infection (with 95% CI), for all THAs (upper left panel) and 5 subgroups of THAs. The broken lines represent no difference in relative risk from the beginning of the period (RR = 1). Adjusted for age, sex, diagnosis, prosthesis, and cement. *Adjusted for age and sex.

Table 3. Adjusted cumulative 5-year revision rates of primary THAs in the NARA. Adjusted for age, sex, diagnosis, prosthesis, and cement

	Period	Number of THAs included	Cumulative 5-years revision rate
			Kaplan-Meier infection		Adjusted infection		Adjusted aseptic loosening		Adjusted all revisions
All THAs	1995–1999	113,280	0.54	(0.49–0.58)	0.46	(0.42–0.50)	1.41	(1.34–1.49)	3,34	(3.22–3.45)
	2000–2004	147,823	0.57	(0.53–0.61)	0.54	(0.50–0.58)	0.81	(0.77–0.86)	3.01	(2.92–3.10)
	2005–2009 ^b	171,065	0.73	(0.68–0.77)	0.71	(0.66–0.76)	1.00	(0.93–1.07)	3.30	(3.19–3.41)
Uncemented THAs	1995–1999	15,177	0.36	(0.26–0.45)	0.34	(0.25–0.44)	1.32	(1.13–1.50)	4.39	(4.05–4.72)
	2000–2004	23,553	0.55	(0.45–0.65)	0.52	(0.43–0.61)	0.85	(0.73–0.97)	4.28	(4.02–4.54)
	2005–2009 ^b	51,445	0.70	(0.61–0.78)	0.65	(0.57–0.74)	1.21	(1.08–1.34)	4.24	(4.02–4.45)
Cemented THAs	1995–1999	86,177	0.51	(0.47–0.56)	0.43	(0.38–0.48)	1.34	(1.25–1.43)	2.82	(2.70–2.94)
	2000–2004	105,421	0.56	(0.51–0.60)	0.52	(0.48–0.57)	0.74	(0.68–0.79)	2.53	(2.43–2.63)
	2005–2009 ^b	96,455	0.74	(0.68–0.81)	0.74	(0.67–0.80)	0.85	(0.77–0.94)	2.93	(2.80–3.07)
Hybrid THAs	1995–1999	11,369	0.94	(0.76–1.12)	0.88	(0.70–1.06)	1.82	(1.55–2.09)	4.92	(4.50–5.34)
	2000–2004	15,163	0.72	(0.58–0.85)	0.67	(0.53–0.80	0.98	(0.81–1.14)	3.79	(3.48–4.10)
	2005–2009 ^b	10,390	0.72	(0.54–0.90)	0.67	(0.50–0.85)	1.00	(0.75–1.25)	3.86	(3.41–4.31)
Inverse hybrid THAs	1995–1999	556	0.77	(0.02–1.51)	0.36	(0–1.38)	2.36	(0.97–3.75	5.59	(3.65–7.54)
	2000–2004	3,685	0.53	(0.29–0.77)	0.34	(0–1.27)	1.64	(1.19–2.09)	3.98	(3.31–4.64)
	2005–2009 ^b	12,775	0.66	(0.50–0.83)	0.43	(0–1.58)	1.37	(1.02–1.72)	3.67	(3.20–4.14)
Modular THAs with antibiotics in cement in patients with OA^a	1995–1999	37,848	0.43	(0.36–0.49)	0.40	(0.33–0.46)	1.18	(0.67–1.69)	2.60	(2.44–2.77)
	2000–2004	69,052	0.49	(0.44–0.55)	0.47	(0.41–0.52)	0.69	(0.39–0.99)	2.21	(2.10–2.32)
	2005–2009 ^b	75,929	0.71	(0.64–0.77)	0.67	(0.60–0.73)	0.78	(0.44–1.12)	2.60	(2.46–2.75)

^a Adjusted for age and sex.

^b Cumulative 5-year revision rates probably were underestimates due to incomplete 5-year follow-up.

Table 4. Adjusted relative risks of revision due to infection for 4 different time intervals after primary surgery, for the 3 time periods. Adjusted for age, sex, diagnosis, prosthesis, and cement

Time after primary surgery	Number of THAs included	Number of THAs revised due to infection	Adjusted risk ratio for revision due to infection	95% CI	p-value
0–3 months
1995–1999	113,280	74	1
2000–2004	147,823	175	1.9	1.4–2.4	<0.001
2005–2009	171,065	535	4.8	3.7–6.2	<0.001
3–12 months
1995–1999	111,607	142	1
2000–2004	145,625	206	1.3	1.0–1.6	0.05
2005–2009	168,019	216	1.2	1.0–1.5	0.09
1–2 years
1995–1999	109,178	164	1
2000–2004	142,589	195	1.1	0.9–1.3	0.6
2005–2009	164,758	175	1.0	0.8–1.3	0.9
> 2 years
1995–1999	105,338	398	1
2000–2004	138,270	361	0.9	0.8–1.1	0.5
2005–2009	126,131	137	0.9	0.7–1.1	0.2

Figure 3. A graphical display of the relationship between relative risk of revision due to infection and time after primary THAs for the period 2000–2004 (left panel) and 2005–2009 (right panel) compared to 1995–1999 (blue lines). Smoothed Schoenfeld residuals adjusted for age, sex, diagnosis, prosthesis and cement (solid lines) with 95% confidence intervals (broken lines).

Table 5. Adjusted relative risks and adjusted cumulative 5-year revision rates for risk factors for revision due to infection. All risk factors were adjusted mutually for the other risk factors in addition to the year of primary surgery. Follow-up in the risk analyses was 1-16 years

	Number of THAs included	Number of THAs revised due to infection	Adjusted risk ratio for revision due to infection	95% confidence interval	p-value	Adjusted cumulative 5-years revision rate, infection
Age (years)
<40	5,590	39	1			0.47
40–51	74,107	515	1.1	0.8–1.5	0.6	0.59
60–69	129,134	854	1.1	0.8–1.5	0.7	0.58
70–79	157,292	1,021	1.1	0.8–1.5	0.6	0.62
80–89	63,034	337	0.9	0.7–1.3	0.8	0.52
≥90	3,011	12	0.7	0.4–1.4	0.3	0.32
Sex
Female	266,42	1,312	1			0.46
Male	165,748	1,466	1.9	1.8–2.1	<0.001	0.87
Diagnosis
Osteoarthritis	345,925	2,090	1			0.54
Hip fracture	33,572	327	2.1	1.9–2.4	<0.001	1.12
Inflammatory disease	15,771	118	1.4	1.1–1.7	0.001	0.72
Childhood hip disease	14,983	80	0.9	0.7–1.2	0.6	0.51
Femoral head necrosis	9,671	92	1.7	1.4–2.1	<0.001	0.87
Other diagnoses	12,246	71	1.3	1.0–1.6	0.06	0.65
Prosthesis
Modular	388,371	2,475	1			0.58
Monoblock	43,797	303	1.1	1.0–1.3	0.09	0.69
Fixation
Uncemented	90,177	542	1			0.54
Cemented	288,053	1,798	1.1	1.0–1.2	0.09	0.58
Hybrid	36,922	337	1.6	1.4–1.8	<0.001	0.79
Inverse hybrid	17,016	101	1.0	0.8–1.3	0.7	0.53
Cement
With antibiotics	316,072	1,997	1			0.58
Without antibiotics	25,921	239	1.5	1.3–1.8	<0.001	0.96