Table 1. Mean and median metal levels at standard time points.

	preop	4 weeks postop	1 year postop	2 years postop	bar removal
Nickel in blood (μg/l)	0.74* (±0.39) ---------- 0.5 [0.00–0.62]	0.64* (±0.35) ---------- 0.24 [0.00–0.79]	1.21* (±0.26) ---------- 1.26* [0.68–1.65]	1.48* (±0.46) ---------- 1.01* [0.98–1.33]	2.32* (±0.47) ---------- 1.83* [1.45–2.09]
Nickel in urine (μg/l)	1.39 (±0.31) ---------- 0.91 [0.68–2.00]	3.34* (±0.63) ---------- 3.37* [2.10–4.54]	11.87* (±3.72) ---------- 8.07* [4.78–10.60]	10.91* (±3.34) ---------- 7.26* [4.13–18.07]	7.24* (±1.61) ---------- 5.16* [3.44–10.89]
Chromium in plasma (μg/l)	0.23 (±0.15) ---------- 0.00 [0.00–0.47]	0.39 (±0.09) ---------- 0.40 [0.29–0.50]	1.32* (±0.16) ---------- 1.40* [0.90–1.70]	2.48* (±0.38) ---------- 2.48* [2.11–2.58]	1.88* (±0.34) ---------- 1.60* [1.10–2.60]
Chromium in urine (μg/l)	0.15 (±0.05) ---------- 0.15 [0.00–0.25]	0.56 (±0.10) ---------- 0.51 [0.41–0.63]	3.50* (±1.00) ---------- 2.57* [1.55–3.26]	5.25* (±1.79) ---------- 4.60* [1.81–6.90]	3.64* (±0.97) ---------- 2.46* [1.65–4.98]
Nickel in tissue (μg/g)	0.7 (±0.20) ---------- 0.65 [0.61–0.91]				5168.40 (±700.10) ---------- 5709.28 [4353–6198]
Chromium in tissue (μg/g)	1.56 (±0.62) ---------- 1.28 [1.12–1.47]				6410.78 (±750.24) ---------- 6473.21 [5780–7354]

Mean metal levels (± standard error of the mean) are shown in the upper part of each table element. Median metal levels and [interquartile range] are mentioned below. *Value above the reference value. Postop = postoperative