Adverse reaction to metal debris after Birmingham hip resurfacing arthroplasty

Figures & data

Table 1. Characteristics of 32 patients and results for 42 corresponding hips. Data on swelling, clicking, and subluxation sensation are given hipwise for 41 hips (the data on 1 hip are missing). Data on mean OHS (range) and the OHS classification are given hipwise for 40 hips (the data on 2 hips are missing). Data on mean (range) age, follow-up, and inclination angle of the cup are given hipwise for 42 hips

	Total	ARMD	Probable ARMD	ARMD not found
Patients, n	32	6	8	18
Males, n	24	6	7	11
Serum cobalt, µg/L^a	2.5 (0.8–14.9)	6.9 (1.2–14.9)	1.5 (0.8–2.6)	1.5 (0.8–2.6)
Serum chromium, µg/L^a	2.1 (0.6–7.6)	4.4 (1.1–7.6)	1.5 (1.0–2.4)	1.6 (0.6–2.5)
Hips, n	42	8	8	24
Age, years ^a	59 (26–77)	63 (49–70)	58 (26–76)	58 (38–77)
Follow-up, years ^a	6.7 (2.4–8.8)	6.0 (2.4–7.0)	6.8 (6.3–7.3)	7.0 (6.2–8.8)
Swelling, n	2	2	0	0
Clicking, n	2	2	0	0
Subluxation sensation, n	6	2	1	3
Inclination angle of the cup, degrees ^a	47 (37–64)	47 (42–61)	50 (39–64)	46 (37–60)
OHS ^a	44 (21–48)	40 (33–48)	45 (32–48)	44 (21–48)
OHS excellent, n	30	3	7	20
OHS good, n	6	4	0	2
OHS fair, n	2	1	1	0
OHS poor, n	2	0	0	2

^a Mean (range)

ARMD: adverse reaction to metal debris;

OHS: Oxford hip score (42–48 = excellent, 34–41 = good, 27–33 = fair, and 0–26 = poor).

Figure 1. A radiograph (panel A) and an MRI image (panel B) of a BHR hip with a pseudotumor.

Table 2. Data on the 6 patients (9 hips) with a definite adverse reaction to metal debris (ARMD). None of the patients had major muscle destruction. The 64 M, 69 M, and 62 M patients had both hips with ARMD. The ARMD diagnosis of the right hip of 64 M was based on operative findings in a revision operation in 2009

Age	Sex	Side	OHS	Pain	Clicking	Sublux.	Swelling	s-Cr, µg/L	s-Co, µg/L	Cup incl. (°)	MRI	Revision or follow-up
64	M	Right	NA	Moderate	No	Yes	No	NA	NA	48	NA	Revised
64	M	Left	35	Moderate	Yes	Yes	Yes	3.9	4.5	43	Solid and fluid	Revised 55 × 35 × 110 mm
69	M	Right	44	Mild	No	No	No	7.6	13.5	61	Fluid 30 × 40 × 65 mm	Revised and 85 × 80 × 30 and solid 20 × 20 × 50
69	M	Left	44	No	No	No	No	7.6	13.5	47	Fluid 57 × 46 × 10 mm	Follow-up
49	M	Right	33	Hard	Yes	Yes	Yes	4.3	4.5	42	Fluid 70 × 26 × 23 mm	Follow-up
62	M	Right	39	No	No	No	No	7.6	14.9	48	No findings	Follow-up
62	M	Left	39	No	No	No	No	7.6	14.9	43	Some fluid	Revised
59	M	Right	41	Moderate	No	No	No	1.6	2.9	47	Fluid 50 × 5 × 5 mm	Follow-up
67	M	Right	48	No	No	No	No	1.1	1.2	47	Fluid 13 × 19 × 50 mm	Follow-up

OHS: See Table 1. Sublux.: subluxation sensation; s-Cr: serum chromium level; s-Co: serum cobalt level; Cup incl.: cup inclination angle;

MRI: magnetic resonance imaging; NA: not available.

Table 3. Results of testing of associations between risk factors and ARMD using logistic regression with random intercept for patient, with crude odds ratios (ORs) and 95% confidence intervals (CIs)

	ARMD definite or probable (n = 17) vs. ARMD not found (n = 25)
	Risk factor	OR (95% CI)	p-value
Age at follow-up	1.03^a	(0.93–1.13)	0.5
Sex (male vs. female)	10.8	(0.7–165)	0.08
Inclination angle of the cup	1.05^a	(0.93–1.2)	0.4
Bilateral MoM	0.33	(0.05–2.1)	0.2
Bilateral THA	0.55	(0.09–3.4)	0.5
Diagnosis secondary vs. primary OA	2.0	(0.27–14)	0.5
Head size (≥ 54 vs. ≤ 50 mm)	4.1	(0.66–25)	0.1

ARMD: adverse reaction to metal debris;

MoM: metal-on-metal implant; THR: total hip arthroplasty

OA: osteoarthritis.

^a For 1 unit increase (continuous variable).

Table 4. Results of testing of associations between risk factors and ARMD using a multiple logistic regression model with random intercept for patient, with adjusted odds ratios (ORs) (including risk factors with p < 0.40 in bivariable model) and 95% confidence intervals (CIs)

	ARMD definite or probable (n = 17) vs. ARMD not found (n = 25)
	Risk factor	OR (95% CI)	p-value
Sex (male vs. female)	7.6	(0.29–204)	0.2
Bilateral MoM	0.40	(0.05–3.2)	0.3
Head size (≥ 54 vs. ≤ 50 mm)	1.6	(0.16–16)	0.7

For abbreviations: See Table 3.