Table 1 Characteristics of patients with and without pseudotumor

Age at surgery*

58.0 ± 9.8

60.2 ± 10.0

54.0 ± 8.2

0.029

0.29^†

Gender (female: male)

54: 10

37: 5

17: 5

0.292

n/a

Diagnosis (OA: ION)

58: 6

40: 2

18: 4

0.169

n/a

BMI (kg/m²)*

22.3 ± 3.0

22.7 ± 2.9

21.6 ± 2.9

0.109

n/a

Preoperative hip extension limitation (+ : -)^†††

(16: 48)

(7: 35)

(9: 13)

0.033

0.27^††

Head material (metal: ceramic)

34: 30

22: 20

12: 10

 > 0.999

n/a

Cup diameter (mm)*

50.9 ± 2.5

50.8 ± 2.5

51.2 ± 2.5

0.620

n/a

Polyethylene liner thickness (mm)*

6.9 ± 1.3

6.8 ± 1.3

7.0 ± 1.4

0.471

n/a

HHS (points)*

87.2 ± 5.9

89.6 ± 5.8

85.4 ± 6.7

0.184

n/a

Cup inclination (°) at 5y*

42.9 ± 6.0

43.7 ± 5.9

41.4 ± 6.1

0.242

n/a

Cup inclination (°) at 15y*

45.4 ± 5.8

45.7 ± 5.9

44.7 ± 5.4

0.625

n/a

Change in cup inclination between 5 and 15y (°)*

2.4 ± 2.1

2.0 ± 1.6

3.3 ± 2.6

0.025

0.28^†

Cup anteversion (°) at 5y*

16.6 ± 10.3

15.9 ± 10.7

18.0 ± 9.4

0.466

n/a

Cup anteversion (°) at 15y*

20.2 ± 10.8

18.7 ± 11.2

23.4 ± 9.0

0.096

n/a

Change in cup anteversion between 5 and 15y (°)*

3.7 ± 2.6

2.9 ± 1.9

5.4 ± 2.8

0.001

0.43^†

PT (°) at 5 y*

10.9 ± 6.5

10.4 ± 7.3

11.9 ± 4.5

0.336

n/a

PT (°) at 15 y*

16.1 ± 6.9

14.5 ± 6.4

19.0 ± 6.7

0.041

0.26^†

Change in PT between 5 and 15y (°)**

5.2 ± 3.8

4.1 ± 2.9

7.2 ± 4.5

0.008

0.33^†

Frequency of osteolysis (cup)

15 (23%)

6 (14%)

9 (41%)

0.028

0.33^††

Frequency of osteolysis (stem)

14 (22%)

6 (14%)

8 (36%)

0.058

n/a

Cobalt ion level (μg/L)**

0.2 (0.2–0.3)

0.2 (0.2–0.3)

0.3 (0.2–0.5)

0.200

n/a

Chromium ion level (μg/L)**

0.3 (0.2–0.4)

0.3 (0.2–0.4)

0.4 (0.3–0.5)

0.259

n/a

Cobalt chrome ratio**

1.0 (0.6–1.2)

1.0 (0.5–1.0)

1.0 (0.8–1.3)

0.248

n/a