Increased risk of revision for infection in rheumatoid arthritis patients with total hip replacements

Figures & data

Table 1. Patient characteristics

	RA	OA	p-value
No. of THRs	13,384	377,287
Mean age (SD), years	62 (14)	69 (9.6)	< 0.001
% females	76%	60%	< 0.001
No. of primary THRs			< 0.001
1995–2001	7,047	130,613
2002–2010	6,337	246,674
Type of fixation, n (%)			0.3
Cemented	8,633 (65)	245,464 (65)
Uncemented	3,034 (23)	83,547 (22)
Hybrid^a	1,143 (8.5)	31,619 (8.4)
Inverse hybrid	574 (4.3)	16,657 (4.4)
Mean follow-up (SD), years	7.0 (4.3)	6.1 (4.1)	< 0.001

^a Hybrid: cemented stem and uncemented cup.

Figure 1. Kaplan-Meier failure curves with revision for infection as the endpoint for rheumatoid arthritis (RA) and osteoarthritis (OA) patients.

Figure 3. Log relative risk (RR) estimates of revision for infection in patients with rheumatoid arthritis (solid line) vs. osteoarthritis (0-line, reference) are shown by year after the primary surgery. Broken lines show the 95% confidence intervals.

Table 2. Relative risk of revision for infection according to sex, age, diagnosis, year of surgery, and type of fixation, calculated using Cox regression analysis

	No. of revisions	RR	95% CI	p-value
Age	2,315	1.0	0.99–1.01	0.1
Sex
Female	1,044	1 (ref.)
Male	1,271	1.9	1.8–2.1	< 0.001
Diagnosis
OA	2,228	1 (ref.)
RA	87	1.3	1.0–1.6	0.04
Year of primary surgery
1995–2001	858	1 (ref.)
2002–2010	1,457	1.4	1.3–1.5	< 0.001
Fixation
AB+ cement ^a	1,632	1 (ref.)
Uncemented	490	0.9	0.8–1.0	0.1
AB– cement ^a	193	1.4	1.2–1.6	< 0.001

^a AB+ cement: antibiotic-loaded cement. AB– cement: cement without antibiotics.

Figure 2. Kaplan-Meier failure curves for rheumatoid arthritis (RA) and osteoarthritis (OA) patients in the periods 1995–2001 and 2002–2010 with revision for infection as the endpoint.

Table 3. Relative risk of revision for infection according to age, sex, and type of fixation for both diagnoses and time periods, calculated using Cox regression analysis

	No. of revisions	RR	95% CI	p-value
RA 1995–2001	44	1 (ref.)
RA 2002–2010	43	1.9	1.2–3.1	0.006
OA 1995–2001	814	1 (ref.)
OA 2002–2010	1,414	1.4	1.3–1.5	< 0.001
OA 1995–2001	814	1 (ref.)
RA 1995–2001	44	1.1	0.8–1.5	0.5
OA 2002–2010	1,414	1 (ref.)
RA 2002–2010	43	1.4	1.0–1.8	0.05