No association between blood count levels and whole-blood cobalt and chromium levels in 1,900 patients with metal-on-metal hip arthroplasty

Figures & data

Table 1. Metal-on-metal hip implant brands of the implant included in this study

Hip resurfacing implants				Total hip implants				Total hip and resurfacing implants
unilateral		bilateral		unilateral THA		bilateral THA
n = 536		n = 156		n = 998		n = 189		n = 21
ASR	198	BHR/BHR	52	ASR	278	ASR/ASR	52	BHR/BHR	6
BHR	194	ASR/ASR	52	Pinnacle	259	Pinnacle/Pinnacle	50	ReCap/BHR	3
Durom	92	Durom/Durom	9	ReCap	157	BHR/BHR	11	ASR/ASR	2
Other	52	Other	43	Other	304	Other	76	Other	10

ASR = Articular Surface Replacement (Depuy Orthopaedics, Warsaw, IN, USA);

BHR = Birmingham Hip Resurfacings (Smith & Nephew, Memphis, TN, USA);

Durom (Zimmer, Warsaw, IN, USA); Pinnacle (Depuy), ReCap (Biomet, Warsaw, IN, USA) .

Table 2. Spearman’s correlation coefficients (ρ) and 95% confidence intervals among whole-blood cobalt, chromium levels, hemoglobin concentration, and leukocyte and platelet counts

Factor	Cobalt	Chromium
Leukocytes	–0.05 (–0.09 to 0.000)	–0.08 (–0.12 to –0.03)
Hemoglobin	–0.09 (–0.13 to –0.05)	–0.12 (–0.16 to –0.07)
Platelets	0.06 (0.02 to 0.11)	0.13 (0.09 to 0.18)
ΔLeukocytes	–0.05 (–0.10 to –0.01)	–0.05 (–0.09 to –0.002)
ΔHemoglobin	0.02 (–0.02 to 0.07)	0.05 (0.007 to 0.10)
ΔPlatelets	0.02 (–0.03 to 0.07)	0.05 (0.003 to 0.09)

Δ = change from preoperative to last postoperative value.

Table 3. Spearman’s correlation coefficients (ρ) and 95% confidence intervals among whole-blood cobalt, chromium levels, and leukocyte differentials

Factor	Cobalt	Chromium
Lymphocytes	–0.09 (–0.21 to 0.03)	–0.09 (–0.21 to 0.03)
Neutrophils	–0.05 (–0.17 to 0.07)	–0.07 (–0.19 to 0.06)
Eosinophils	0.11 (–0.01 to 0.23) ^a	0.05 (–0.07 to 0.17)
Basophils	–0.02 (–0.14 to 0.11)	0.003 (–0.12 to 0.13)
Monocytes	–0.06 (–0.18 to 0.06)	–0.08 (–0.20 to 0.42) ^a

^a95% confidence interval of the Spearman correlation coefficient includes value of 0.225, indicating that 5% variance for blood eosinphils explained by whole blood cobalt concentration, and 5% variance for blood monocytes explained by whole blood chromium concentrations cannot be ruled out by this analysis.