Inferior outcome after hip resurfacing arthroplasty than after conventional arthroplasty

Figures & data

Table 1. The total study group of 174,192 THA patients up to 73 years of age (those with femoral fractures excluded) who were operated 1995 through 2007

	HRA	THA	p-value
	n = 1,638	n = 172,554
Percentage males	68	43	< 0.001 ^a
Mean age, years (range)	51 (15–73)	62 (12–73)	< 0.001 ^b
Age groups, %
< 30	2.1	0.6
30–39	8.9	1.8
40–49	31	6.1
50–59	42	23
60–74	17	69	< 0.001 ^a
Operated side, % (no.)
Right	53 (861)	54 (93,866)	0.1 ^a
Diagnosis, %
Primary osteoarthritis	89	85
Inflammatory arthritis	2.2	4.3
Childhood diseases	6.5	6.1
Idiopathic femoral head necrosis	0.9	2.7
Other	1.0	2.1	< 0.001 ^a

^a Chi-squared test.

^b Non-parametric.

Table 2. HRA implant designs in the NARA database, 1995–2007

Implant design	%	n
BHR	48	780
Durom	21	344
ASR	18	296
ReCap	12	191
Adept	0.9	14
Cormet (+/- HA)	0.4	7
McMinn	0.4	6
Total		1,638

Table 3. Unadjusted revision rates and reasons for aseptic revision up to 2 years

	HRA	THA	p-value
	n=1,638	n=172,554
Crude aseptic revision rate, % (no.)
1 year	1.6 (26)	0.7 (1251)
2 years	2.4 (40)	1.1 (1954)
Kaplan-Meier unadjusted non-septic cumulative revision rate, % (95% CI)
1 year	1.8 (1.1–2.4)	0.8 (0.7–0.8)
2 years	3.3 (2.2–4.3)	1.2 (1.2–1.3)	< 0.001 ^a
Reason for revision up to 2 years, % (no.)
Aseptic loosening	25 (10)	25 (497)
Fracture	40 (16)	9 (176)
Dislocation	0	50 (967)
Pain only	5 (2)	4 (88)
Other	30 (12)	12 (226)	< 0.001 ^b

^a Log-rank test.

^b Chi-squared test.

Figure 1. Unadjusted Kaplan-Meier-estimated cumulative survival (CS ± 1.96 SE) for 1,638 HRAs with estimated 2-year CS of 96.7% (95% CI: 95.7–97.8; no. remaining = 547) and 172,554 THAs with estimated 2-year CS of 98.8% (95% CI: 98.7–98.8; no. remaining = 135,173); p < 0.001 (log-rank test).

Table 4. Age- and sex-stratified relative risk of aseptic revision within 2 years after primary operation. HRA was compared to all other types of conventional THA or only to the all-cemented (all-c THA) subpopulation. Data are based on a Cox regression model adjusted for operated side, nationality, diagnosis, and type of implant

	Adjusted revision risk (95% CI)				Number of cases (No. of revisions)
	HRA/THA	p-value	HRA/all-c THA	p-value	HRA	THA	all-c THA
Age < 50 years
Males	1.9 (1.0–3.9)	0.07	2.4 (1.1–5.3)	0.04	460 (9)	7,183 (109)	1,782 (18)
Females	4.7 (2.6–8.5)	< 0.001	7.4 (3.7–15)	< 0.001	221 (13)	7,486 (114)	2,242 (21)
Age 50–73 years
Males	1.7 (0.9–3.1)	0.1	2.1 (1.1–3.9)	0.02	653 (10)	67,134 (807)	43,725 (387)
Females	3.2 (1.6–6.5)	0.001	4.0 (2.0–8.1)	< 0.001	304 (8)	90,751 (924)	64,308 (482)

Table 5. Relative risk of aseptic revision up to 2 years (RR) with 95% confidence interval (CI) in 1,611 hip resurfacings (35 revisions). Data are based on a Cox regression model including age (< 50 or ≥ 50 years), sex, diagnosis, hospital production volume, and the 4 most common HRA designs with BHR as reference

	RR	95% CI	p-value
Hospital production volume:
< 70 / ≥ 70 procedures	3.7	1.5–8.9	0.003
Hip resurfacing design:
BHR (reference)	1	–	0.02
Durom	3.1	1.2–7.8	0.02
ASR	2.7	1.0–7.4	0.06
ReCap	5.4	1.8–16	0.003
Male / female	0.5	0.2–0.9	0.03
Age (< 50 / 50–73 years)	1.5	0.8–3.1	0.2
Primary / secondary OA	1.0	0.4–2.8	0.9

Table 6. The same type of analysis as in Table 5 except that femoral head diameter (categorized as ≤ 44mm, 45–49 mm, 50–54 mm, and ≥ 55 mm) has been added, resulting in 1,552 hip resurfacings (35 revisions) available for analysis

	RR	95% CI	p-value
Hospital production volume:
< 70 / ≥ 70 procedures	3.7	1.5–8.8	0.004
Hip resurfacing design:
BHR (reference)	1	–	0.02
Durom	3.1	1.2–7.8	0.02
ASR	2.3	0.8–6.5	0.1
ReCap	5.4	1.8–17	0.003
Male / female	0.7	0.3–1.8	0.5
Femoral head diameter
< 44 mm (reference)	1	–	0.3
45–49 mm	0.8	0.3–2.4	0.8
50–54 mm	0.4	0.1–1.4	0.2
> 55 mm	0.9	0.2–4.2	0.9
Age (< 50 / 50–73 years)	1.4	0.7–3.0	0.3
Primary / secondary OA	1.2	0.4–3.4	0.7

Figure 2. Unadjusted Kaplan-Meier-estimated cumulative survival (CS) of the group of the 4 most common types of HRA, subgroups with significant influence on early non-septic revision rate (CS ± 1.96SE). A. Hospital with ≥ 70 HRAs: n = 820, 2-year CS = 98.8% (95% CI: 97.9–99.8; no. remaining at 2 years = 269). Hospital with < 70 HRA: n = 791, 2-year CS = 95.5% (95% CI: 93.7–97.2; no. remaining at 2 years = 272); p < 0.001 (log-rank test). B. BHR: n = 780, 2-year CS = 98.8% (95% CI: 97.9–99.7; no. remaining at 2 years = 341). Non-BHR: n = 831, 2-year CS = 95.6% (95% CI: 93.8–97.3; no. remaining at 2 years = 200); p < 0.001 (log-rank test).