Complications and re-revisions after revisions of 528 metal-on-metal hips because of adverse reaction to metal debris

Figures & data

Figure 1. Flow chart of patient inclusion. MoM = metal-on-metal; Co = cobalt; Cr = chromium; ARMD = adverse reaction to metal debris. ^aNo preoperative imaging or Co/Cr measurements.

Table 1. Patients’ pre-revision characteristics

	Total hip arthroplasty	Hip resurfacing
Factor	n = 420	n = 108
Women, n (%)	230 (55)	72 (67)
Age at revision, mean (SD)	67 (8.5)	57 (9.7)
Pre-revision Co, µg/L
median (range)	11.8 (0.2–192)	11.8 (0.4–225)
(IQR)	(7.0–20)	(2.1–36)
Pre-revision Cr, µg/L
median (range)	7.9 (0.4–156)	7.4 (0.8–125)
(IQR)	(2.3–6.5)	(2.2–20)
Any symptoms n (%)	272 (65)	79 (73)
Imaged with
MRI, n (%)	301 (72)	83 (77)
ultrasound, n (%)	119 (28)	25 (23)
Head size, median mm (range)	47 (28–59)	49 (42–63)
Years between primary and
revision surgery, mean (SD)	6.3 (2.4)	6.7 (2.4)
BMI, mean (SD)	28 (4.7)	28 (4.5)
ASA class at primary
1/2/3/4/NA	40/219/144/3/14	42/51/10/2/3

SD = standard deviation; IQR = interquartile range; NA = not available.

Table 4. Pre-revision imaging findings with MRI or ultrasound

	Total hip arthroplasty		Hip resurfacing
Grade	n (%)	Size, cm median (range)	n (%)	Size, cm median (range)
0	203 (48)		50 (46)
1	82 (20)	5.7 (1.2–25)	22 (20)	4.9 (2.4–10)
2A	48 (11)	6.4 (3.0–17)	8 (7)	7.5 (4.3–11)
2B	68 (16)	8.4 (3.6–30)	25 (23)	7.9 (2.5–19)
3	19 (5)	6.0 (2.4–13)	3 (3)	10.7 (5.4–13)
Total	420		108

Imaging findings are classified according to a previously described grading system (Matthies et al. 2012). Grade 0 represents normal imaging finding; grade 1 represents thin-walled fluid-filled pseudotumor; grade 2A a fluid-filled pseudotumor with thick or irregular walls; 2B a pseudotumor with atypical contents; and grade 3 a predominantly solid pseudotumor.

Figure 2. Non-linear association was seen between pre-revision blood cobalt (Co) concentration and risk for revision. Preoperative Co between approximately 20 and 90 µg/L was associated with increased risk for re-revision. Hazard ratios are presented in relation to median Co of 11.8 µg/L. Gray area represents 95% confidence interval.

Table 5. Indications for re-revisions and complications after the revisions of metal-on-metal total hip arthroplasty (THA) and resurfacing arthroplasties

	THA	Resurfacing
after closed reduction	18	2
Re-revision indication
Mechanical reasons
Recurrent dislocation or instability
Periprosthetic femoral fracture	1	3
Acetabular fracture	2	0
Fracture of stem component	0	1
Aseptic loosening of stem	1	1
Non-mechanical reasons
Recurrent ARMD	1	1
Infection	4	1
Total	27	9
Complication
Mechanical complication
Dislocation(s) treated with
closed reduction	11	2
Acetabular fracture ^a	3	0
Trochanteric fracture ^b	1	0
Fascial rupture ^c	2	1
Hernia	1	0
Non-mechanical complication
Residual pseudotumor	0	2
Pulmonary embolism	1	0
Deep vein thrombosis	1	1
Bowel occlusion	1	0
Total	21	6

ARMD = adverse reaction to metal debris;

^anon-operative treatment;

^boperated with titanium plate without change of components;

^cre-suture without change of components.

Matthies A K, Skinner J A, Osmani H, Henckel J, Hart A J. Pseudotumors are common in well-positioned low-wearing metal-on-metal hips. Clin Orthop Relat Res 2012; 470(7): 1895–906.

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