Total ankle replacement: a population-based study of 515 cases from the Finnish Arthroplasty Register

Figures & data

Table 1.  Implants used for primary total ankle replacement in Finland during the period 1980–2006

Brand of implant	n	Used during years	Included in analysis
AES	298	2002–2006	yes
S.T.A.R.	217	1997–2006	yes
ICLH	32	1980–1987	no
Hintegra	11	2005–2006	no
Thompson-Parkridge- Richards	6	1980–1984	no
Oregon	4	1980–1985	no
RCM	3	1981–1984	no
Other	2	1980–1986	no
Total	573

Figure 1.  Number of ankle prostheses implanted per year in Finland during the period 1997–2006.

Table 2.  Ankle replacements related to diagnosis during the period 1997–2006

	Rheumatoid arthritis	Other indications	All indications
Mean follow-up time in years (range)	3.4 (0.1–9.6)	2.9 (0.1–9.1)	3.2 (0.1–9.6)
Mean age at operation (range)	53 (17–81)	56 (18–86)	55 (17–86)
% Women	78%	50%	63%
Total number of
TARs	252	263	515
S.T.A.R.	128	89	217
AES	124	174	298
No. of patients with bilateral operations	18	8	26

Table 3.  Survival rates and Cox-adjusted risk ratios for revision of S.T.A.R. and AES total ankle replacements during the period 1997–2006 in Finland. The endpoint was defined as revision for any reason, and revision for aseptic loosening of one or both of the prosthesis components

A	B	C	D	E	F	G	H	I
Revision for any reason
S.T.A.R.	31 / 217	4.8 (0–9.6)	199 96 (94–99)	180 92 (88–96)	112 85 (80–90)	24 80 (73–88)	1.0	–
AES	28 / 298	2.0 (0–4.7)	227 96 (93–98)	69 88 (84–93)	– –	– –	7 (0.9–3.0)	1. 0
Aseptic loosening
S.T.A.R.	9 / 217	4.8 (0–9.6)	199 100 (99–100)	180 98 (97–100)	112 96 (93–99)	24 91 (84–98)	1.0	–
AES	5 / 298	2.0 (0–4.7)	227 100 (99–100)	69 98 (97–100)	– –	– –	2.7 (0.7–10.9)	0.2

A Implant design

B No. of revisions / no. of total operations.

C Mean follow-up in years (range)

D At risk at 1 year, 1-year survival (%) and (95% CI)

E At risk at 3 years, 3-year survival (%) and (95% CI)

F At risk at 5 years, 5-year survival (%) and (95% CI)

G At risk at 7 years, 7-year survival (%) and (95% CI)

H Adjusted risk ratio from the Cox regression analysis (adjustment was made for age and sex) for revision (95% CI)

I p-value

Figure 2.  Kaplan-Meier survival curves for 217 S.T.A.R. and 298 AES total ankle replacements (with a mean follow-up of 4.8 and 2.0 years, respectively). The endpoint was defined as revision for aseptic loosening of one or both of the prosthesis components, and revision for any reason. The difference between survival rates for aseptic loosening of the 2 kinds of ankle replacements is not statistically significant (Log-rank test; p = 0.2).

Figure 3.  Kaplan-Meier survival curves for 217 S.T.A.R. and 298 AES total ankle replacements (with a mean follow-up of 4.8 and 2.0 years, respectively). The endpoint was defined as revision for any reason. The difference between survival rates is not statistically significant (Log-rank test; p = 0.08).

Table 4.  Reasons for 59 revisions in 217 S.T.A.R. and 298 AES total ankle replacements (with a mean follow-up time of 4.8 and 2.0 years, respectively)

	S.T.A.R.	AES	All
Aseptic loosening	16	7	23
tibia	10	2	–
talus	3	5	–
both	3	0	–
Infection	3	1	4
Instability^a	6	17	23
Fracture of the meniscal implant	2	1	3
Periprosthetic fracture	0	1	1
Primary malalignment of the prosthesis	4	1	5
Total	31	28	59

^a With or without dislocation of the meniscal implant.