The association between metal allergy, total knee arthroplasty, and revision

Figures & data

Figure 1. The process of selection of the study population.

Table 1. Characteristics of patients who underwent primary total knee replacement and revision surgery between 1997 and 2009

	Patients from the DKAR (2013) (n = 43,910) n (%)	Dermatitis patients from the DKAR ^a (n = 327) n (%)	Odds ratio (95% CI) ^b
Female gender	27,367 (62.3)	234 (71.6)	0.7 (0.5–0.8)
Age groups:
10–49	2,224 (5.1)	15 (4.6)	1.1 (0.7–1.9)
50–59	7,383 (16.8)	68 (20.8)	0.8 (0.6–1)
60–69	14,721 (33.5)	111 (33.9)	1 (0.8–1.2)
70–79	14,161 (32.2)	108 (33.0)	1 (0.8–1.2)
> 79	5,421 (12.3)	25 (7.6)	1.7 (1.1–2.6)
Primary diagnosis:
Primary idiopathic osteoarthritis	36,694 (83.6)	281 (85.9)	0.8 (0.6–1.1)
Secondary osteoarthritis	4,190 (9.5)	24 (7.3)	1.3 (0.9–2)
Sequelae of trauma	1,029 (2.3)	3 (0.9)	2.6 (0.8–8.1)
Rheumatoid arthritis	1,389 (3.2)	16 (4.9)	0.6 (0.9–1.1)
Sequelae of other arthritides	211 (0.5)	0
Hemophilia	21 (0)	1 (0.3)	0.2 (0.02–1.2)
Other diagnoses	376 (0.9)	2 (0.6)	1.4 (0.4–5.7)
Type of operation:
Total arthroplasty	40,773 (92.9)	301 (92.0)	1.1 (0.8–1.7)
Unicompartmental arthroplasty	3,137 (7.1)	26 (8.0)	0.9 (0.6–1.3)
Previously operated in the same knee	13,261 (30.2)	86 (26.3)	1.2 (1–1.6)
Cause of revision:
Aseptic loosening	883 (2.0)	7 (2.1)	0.9 (0.4–2)
Pain but no loosening	669 (1.5)	13 (4.0)	0.4 (0.2–0.7)
Instability of the knee	587 (1.3)	9 (2.8)	0.5 (0.3–0.9)
Deep infection	622 (1.4)	7 (2.1)	0.7 (0.3–1.4)
Secondary insertion of patella component	340 (0.8)	5 (1.5)	0.5 (0.2–1.2)
Polyethylene failure, patella/tibia	223 (0.5)	3 (0.9)	0.6 (0.2–1.7)
Other	443 (1.0)	1 (0.6)	3.3 (0.5–23.7)
Postoperative complications	2,023 (4.6)	11 (3.4)	1.4 (0.8–2.5)

^a Patients who were examined for metal allergy at Gentofte Hospital

^b Comparison of patients from the Danish Knee Arthroplasty Register (DKAR) (reference category) and patients from the DKAR who were also examined for metal allergy at Gentofte Hospital, Copenhagen (chi-square test). Fisher’s exact test was used when the expected frequency in 1 of the cells was lower than 5.

Table 2. Nickel, cobalt, and chromium (+metal*) allergy stratified by patient status. Values are n (%) and (95% CI)

	n	Nickel allergy	Cobalt allergy	Chromium allergy	Metal allergy^a
Adults from the general population (Thyssen et al. 2009c)	3,460	204 (5.9) (5.2–6.8)	8 (0.2) (0.1–0.5)	5 (0.1) (0.1–0.3)	345 (9.7) (9–11)
Dermatitis patients from between 1977 and 2009 (Thyssen et al. 2010)	22,506	2,341 (10.4) (10–10.8)	856 (3.8) (3.6–4.1)	608 (2.7) (2.5–2.9)	Not available
Dermatitis patients who underwent knee arthoplasty	327	39 (12) (8.9–16)	9 (2.8) (1.5–5.1)	14 (4.3) (2.6–7.1)	50 (15) (12–20)
Dermatitis patients who underwent knee arthoplasty but not revision surgery	295	37 (13) (9.2–16)	12 (4.1) (2.3–7)	8 (2.7) (1.4–5.3)	46 (16) (12–20)
Dermatitis patients who underwent knee arthoplasty and had revision surgery	32	2 (6.3) (1.7–20)	2 (6.3) (1.7–20)	1 (3.1) (0.6–16)	4 (13) (5–28)

^a defined as nickel, cobalt, and/or chromium allergy.

Table 3. The prevalence of metal allergy in 327 patients who underwent primary TKA and/or revision surgery. Values are n (%) and (95% CI)

	Operated once once	Revised^a (n = 32)	Revised once (n = 24)	Revised 2 or more times (n = 8)	OR^a	p-value
Metal allergy ^b	46 (16) (12–20)	4 (13) (5–28)	2 (8) (2–26)	2 (25) (7–59)	0.8 (0.3–2)	1
Nickel allergy	37 (13) (9–17)	2 (6) (2–20)	2 (8) (2–26)	0 (0)	0.5 (0.1–2)	0.05
Cobalt allergy	8 (3) (1–6)	1 (3) (1–16)	0	1 (13) (2–47)	1.2 (0.1–9.6)	1
Chromium allergy	12 (4) (2–7)	2 (6) (2–20)	0	2 (25) (7–59)	1.5 (0.3–7)	0.06

^a For comparison of cases without revision and those with any revisions (chi-square test). Fisher’s exact test was used when the expected frequency in one of the cells was lower than 5.

^b Metal allergy was defined as a positive patch test reaction to nickel, cobalt, or chromium.

OR: odds ratio.

Thyssen JP, Linneberg A, Menne T, Nielsen NH, Johansen JD. Contact allergy to allergens of the TRUE-test (panels 1 and 2) has decreased modestly in the general population. Br J Dermatol 2009c; 161: 1124-9.

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Thyssen JP, Ross-Hansen K, Menne T, Johansen JD. Patch test reactivity to metal allergens following regulatory interventions: a 33-year retrospective study. Contact Dermatitis 2010; 63: 102-6.

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