Mixing of components from different manufacturers in total hip arthroplasty: prevalence and comparative outcomes

Figures & data

Figure 1. Diagram to show mixing of stem, head, and cup components between different manufacturers (modular stems only), where A, B, and C are manufacturers

Table 1. Mixed stem and cup manufacturers in cemented modular stem, or monobloc stem, used with a polyethylene cemented cup

Mix-and-match status	n (%)	Men (%)	Age at primary operation median (IQR)	Observed revisions	Expected revisions^a	Approximate patient-years (x100)	PTIR ^b [95% CI] per 100 patient-years
Matched	158,178 (77)	34	74 (68–80)	2,155	2,080	6,800	0.32 [0.30–0.33]
Different stem and cup	48,156 (23)	34	74 (68–80)	586	662	2,200	0.27 [0.25–0.29]

^a Calculated under the assumption of no difference in implant survival between the 2 mix-and-match subgroups, correcting for differences in group size and sex/age composition.

^b PTIR: patient-time incidence rates.

Figure 2. Effect of stem and cup manufacturer mismatch on revision of cemented modular stem or monobloc stem used with a polyethylene cemented cup. Kaplan-Meier estimates of cumulative % probability of revision. Shaded bands indicate point-wise 95% CI.

Figure 3. Effect of stem and head manufacturer mismatch on revision of cemented modular stem used with cemented polyethylene cup. Kaplan-Meier estimates of cumulative % probability of revision. Shaded bands indicate point-wise 95% CI.

Table 3. Mixed stem, head, and cup manufacturers in modular stems with a metal head and a metal shell with a polyethylene liner

Stem fixation
Mix-and-match status	n (%)	Men (%)	Age at primary operation median (IQR)	Observed revisions	Expected revisions^a	Approximate patient-years (x100)	PTIR ^b [95% CI] per 100 patient-years
(i) Cemented (n = 60,167)
All matched	35,588 (59)	35	74 (68–79)	469	477	1,200	0.38 [0.35–0.41]
Different cup	24,004 (40)	36	73 (67–78)	386	385	1,000	0.38 [0.34–0.42]
Different stem	136 (0.2)	32	79 (74–82)	2	1	4	0.54 [0.13–2.15]
All mixed	439 (0.7)	26	77 (72–81)	11	5	13	0.88 [0.49–1.58]
(ii) Uncemented (n = 79,117)
All matched	72,742 (92)	40	71 (65–77)	1,386	1,379	2,500	0.55 [0.52–0.58]
Different cup	5,906 (7.5)	39	72 (65–78)	107	114	205	0.52 [0.43–0.63]
Different stem	317 (0.4)	39	71 (65–77)	5	5	85	0.59 [0.24–1.41]
All mixed	152 (0.2)	38	71 (65–77)	3	3	4	0.69 [0.22–2.12]

^a Calculated under the assumption of no difference in implant survival between the 2 mix-and-match subgroups, correcting for differences in group size and sex/age composition.

^b PTIR: patient-time incidence rates.

Table 6. The mixing of head and cup manufacturers in modular stems using a ceramic head and a metal shell with a ceramic liner

Stem fixation
Mix-and-match status	n (%)	Men (%)	Age at primary operation median (IQR)	Observed revisions	Expected revisions^a	Approximate patient-years (x100)	PTIR ^b [95% CI] per 100 patient-years
(i) Cemented (n = 16,045)
Matched	14,836 (93)	40	61 (54–66)	192	186	622	0.31 [0.27–0.36]
Different head and cup	1,209 (7.5)	44	62 (54–69)	5	11	32	0.16 [0.06–0.37]
(ii) Uncemented (n = 71,111)
Matched	68,459 (96)	46	61 (54–67)	1,250	1250	2100	0.59 [0.55–0.62]
Different head and cup	2,652 (3.7)	39	62 (55–68)	41	41	63	0.65 [0.48–0.88]

^a Calculated under the assumption of no difference in implant survival between the 2 mix-and-match subgroups, correcting for differences in group size and sex/age composition.

^b PTIR: patient-time incidence rates.

Table 8. Mixed stem, head, and cup in modular stems with metal heads used with a metal monobloc cup designed for use in hip resurfacing

Stem fixation
Mix-and-match status	n (%)	Men (%)	Age at primary operation median (IQR)	Head size (mm) median (IQR)	Observed revisions	Expected revisions^a	Approximate patient-years (x100)	PTIR ^b [95% CI] per 100 patient-years
(i) Cemented (n = 1,467)
All matched	952 (65)	52	64 (56–75)	48 (46–50)	87	94	54	1.63 [1.32–2.01]
Different cup	1 (0.1)	0	64	28	0	c	0.03	–^c
Different stem	514 (35)	52	61 (55–67)	46 (46–50)	75	68	32	2.37 [1.89–2.98]
All mixed	0	–	–	–	–	–	–	–
(ii) Uncemented (n = 12,847)
All matched	11,350 (88)	55	61 (54–68)	46 (44–50)	1,507	1434	595	2.53 [2.41–2.67]
Different cup	0	–	–	–	–	–	–	–
Different stem	1,492 (12)	57	61 (54–67)	46 (44–50)	109	183	78	1.40 [1.16–1.69]
All mixed	5 (<0.1)	60	52 (50–56)	48 (46–48)	2	–^c	0.1	–^c
(iii) Uncemented excluding the ASR resurfacing cup (n = 9,881)
All matched	8,391	56	61 (54–68)	48 (44–50)	609	609	437	1.40 [1.29–1.51]
Different cup	0	–	–	-	–	–	–	–
Different stem	1,485	57	61 (54–67)	46(44–50)	108	109	77	1.40 [1.16–1.69]
All mixed	5	60	52 (50–56)	48 (46–48)	2	–^c	0.1	–^c

^a Calculated under the assumption of no difference in implant survival between the 2 mix-and-match subgroups, correcting for differences in group size and sex/age composition.

^b PTIR: patient-time incidence rates.

^c Excluded from analysis as numbers too small.