Adverse reactions to metal debris occur with all types of hip replacement not just metal-on-metal hips: a retrospective observational study of 3340 revisions for adverse reactions to metal debris from the National Joint Registry for England, Wales, Northern Ireland and the Isle of Man

Table 1 Risk of ARMD revision surgery for the three most commonly implanted primary hip replacement bearing surfaces by femoral head size

Hip bearing surface	Femoral head size (mm)	Number of hips implanted	Number of hips revised for ARMD	Risk of ARMD revision surgery (%) (95% CI)	Relative risk (95% CI) of ARMD revision with 36 mm head size (vs. 28/32 mm)	p-value (36 mm vs. 28/32 mm for same bearing surface)
MoP	28 & 32	407,412	85	0.021 (0.017–0.026)	2.80 (1.74–4.36)	<0.001
MoP	36	46,258	27	0.058 (0.038–0.085)	2.80 (1.74–4.36)	<0.001
CoC	28 & 32	61,937	35	0.057 (0.039–0.079)	0.92 (0.56–1.51)	0.725
CoC	36	67,373	35	0.052 (0.036–0.072)	0.92 (0.56–1.51)	0.725
CoP	28 & 32	96,286	24	0.025 (0.016–0.037)	0.82 (0.24–2.19)	0.683
CoP	36	24,513	5	0.020 (0.007–0.048)	0.82 (0.24–2.19)	0.683

ARMD Adverse reactions to metal debris, CoC Ceramic-on-ceramic, CoP Ceramic-on-polyethylene, MoP Metal-on-polyethylene, CI Confidence interval

ISSN: 1471-2474