257 ankle arthroplasties performed in Norway between 1994 and 2005

Figures & data

Figure 1. A. Distribution of prosthesis types per year. B. Distribution of diagnoses per year.

Table 1. Diagnosis leading to ankle replacement

Diagnosis ^a	No. of patients	No. of women %)	Age mean SD)
Primary osteoarthritis	53	30 (57)	63 (14)
RA	129	100 (78)	58 (14)
Fracture sequelae	57	37 (65)	59 (13)
Ankylosing spondylitis	4	1	43 (13)
Psoriatic arthritis	5	3	54 (17)
Sequelae of ligament damage	5	2	61 (9.0)
Other ^b	13	7	52 (15)
P-value ^c		0.02	0.02

^a More than one diagnosis was allowed.

^b Includes hemophilia, hemocromatosis, Crohn's disease, arthritis urica, and others.

^c Calculated using chi-square test (sex) or ANOVA (age).

Table 2. Comparison of the Norwegian TPR and the STAR prostheses according to age, gender, diagnosis, number of hospitals using (or having used) the prosthesis, and year of surgery

	Norwegian TPR (n = 32)	STAR (n = 216)
Age, mean (SD)	61 (15)	58 (13)
No. of women (%)	24 (75)	146 (68)
Diagnosis, n (%)
IA ^a	31 (97)	106 (49)
OA ^b	1 (3)	97 (45)
Other	0	13 (6)
No. of hospitals	7	10
Year of surgery
1994–1999	32	36
2000–2005	0	180
Observation time,
mean years (SD)	7.7 (3.2)	3.1 (2.3)

^aIA: Inflammatory arthritis, including rheumatoid arthritis, psoriatic arthritis, and ankylosing spondylitis.

^bOA: Osteoarthritis, including primary osteoarthritis, fracture sequelae and sequelae after ligament damage.

Figure 2. Unadjusted Kaplan-Meier curves with revision as endpoint: A. All; B. According to age category; C. According to gender; D. According to diagnosis; E. According to type of prosthesis; F. Revisions due to aseptic loosening, according to version of STAR prosthesis.

Table 3. Causes of revision by type of prosthesis

Cause ^a	Norwegian TPR n = 32	STAR n = 216
Aseptic loosening of either
or both components	6	7
Instability	0	3
Incorrect axis (malalignement)	0	7
Deep infection	0	2
Fracture	0	1
Pain	0	5
Defect/wear of polyethylene insert	0	2
Other	0	2
Total number of revisions	6	21

^aMore than one cause may be given for each ankle, but pain was included only when it was the sole cause of revision.

Table 4. Causes of revision for single- and doublecoated STAR prostheses

Cause ^a	Single-coated n = 35	Double-coated n = 177
Aseptic loosening	5	1
Instability	1	1
Incorrect axis (malalignement)	3	3
Deep infection	0	2
Fracture	1	0
Pain	0	5
Defect/wear of polyethylene insert	2	0
Other	0	2
Total number of revisions	8	13

^aMore than one cause may be given for each ankle, but pain was included only when it was the sole cause of revision.

Table 5. Survival analysis (Kaplan-Meier and Cox regression) for revision after ankle arthroplasty according to potential explanatory factors

	No. of ankle replacements	No. of revisions	S5(%)	95% CI	RR	95% CI
All	235 ^a	26 ^b	89	84–93
Age					1	1–1
Sex
Men	71	6	93	86–100	1.2	0.5–3
Women	164	20	87	82–93	1
Type of prosthesis
TPR	32	6	90	80–100	1
STAR	203	20	89	84–94	1.2	0.6–2
Diagnosis
OA	98	6	90	83–98	1
IA	137	20	88	82–94	1.5	0.6–4
Year of surgery
1994–1999	68	12	90	82–97	1
2000–2005	167	14	89	83–95	1.1	0.4–3

^aN = 235 because only Norwegian TPR and STAR prostheses were included and only patients with OA (primary and secondary osteoarthritis) or IA (inflammatory arthritis including RA, psoriatic arthritis, and ankylosing spondylitis) were included in the analysis.

^bOnly 26 of 27 revisions were included because the diagnosis was unknown in 1 case. S5: Kaplan-Meier 5-year survival probabilities with 95% confidence intervals.