How Do Metal Ion Levels Change over Time in Hip Resurfacing Patients? A Cohort Study

Table 2

Ion values expressed as ng/mL (nanograms per milliliter, mean ± standard error, median, and minimum–maximum range) in metal-on-metal hip resurfacing at short [15], medium [15] and long term, as whole cohorts and split by gender. Reference ranges are reported, too.

	Group  1 [15]; (2-year follow-up)	Group  2; (5-year follow-up)	Group  3; (9-year follow-up)		^*	^**
Chromium	Reference range: 0.06–0.67 ng/mL
Whole cohort	2.18 ± 0.51 (1.53); 0.69–7.24	2.26 ± 0.49 (1.63); 0.49–10.47	1.82 ± 0.33 (1.27); 0.56–6.19	0.64	0.38	0.17
Males	1.12 ± 0.12 (1.09); 0.69–1.79	1.44 ± 0.17 (1.30); 0.88–2.47	1.49 ± 0.36 (1.06); 0.56–6.19	0.16	0.79	0.46
Females	3.61 ± 0.93 (2.46); 1.73–7.24	3.17 ± 0.96 (2.36); 0.49–10.47	2.52 ± 0.69 (2.06); 0.93–6.01	0.63	0.20	0.56
Cobalt	Reference range: 0.08–0.59 ng/mL
Whole cohort	1.17 ± 0.61 (0.55); 0.08–8.96	1.13 ± 0.27 (0.72); 0.30–5.60	0.90 ± 0.12 (0.77); 0.29–2.45	0.14	0.12	0.86
Males	0.39 ± 0.09 (0.39); 0.08–0.76	0.82 ± 0.18 (0.63); 0.30–2.27	0.72 ± 0.08 (0.68); 0.29–1.54	0.05	0.01	0.75
Females	2.22 ± 1.36 (0.85); 0.41–8.96	1.47 ± 0.53 (1.20); 0.30–5.60	1.28 ± 0.30 (0.93); 0.32–2.45	>0.1	0.89	0.67
Nickel	Reference range: 0.10–1.32 ng/mL
Whole cohort	0.64 ± 0.06 (0.69); 0.10–0.99	0.95 ± 0.09 (0.93); 0.34–1.95	0.38 ± 0.06 (0.31); 0.10–1.50	0.01	0.001	<0.001
Males	0.62 ± 0.1 (0.72); 0.1–0.99	0.78 ± 0.09 (0.78); 0.34–1.25	0.40 ± 0.09 (0.32); 0.17–1.50	0.33	0.04	0.001
Females	0.67 ± 0.06 (0.66); 0.48–0.94	1.14 ± 0.15 (0.94); 0.72–1.95	0.35 ± 0.09 (0.29); 0.10–0.79	0.08	0.03	0.002
Molybdenum	Reference range: 0.20–2.75 ng/mL
Whole population	0.89 ± 0.03 (0.83); 0.83–1.23	0.84 ± 0.01 (0.83); 0.83–0.96	0.85 ± 0.01 (0.83); 0.82–0.97	0.06	0.001	0.001

= group 1 versus group 2, ^* = group 1 versus group 3, and ^** = group 2 versus group 3.