CC BY-NC-ND 4.0 · Rev Bras Ortop (Sao Paulo) 2020; 55(02): 239-246
DOI: 10.1055/s-0039-3400516
Artigo Original
Quadril
Sociedade Brasileira de Ortopedia e Traumatologia. Published by Thieme Revinter Publicações Ltda Rio de Janeiro, Brazil

Pelvic Bone Deformity and Its Correlation with Acetabular Center-edge Angle[*]

Article in several languages: português | English
1  Grupo de Quadril do Hospital Ortopédico de Passo Fundo, Faculdade de Medicina da Universidade de Passo Fundo, Passo Fundo, RS, Brasil
,
Milton Valdomiro Roos
1  Grupo de Quadril do Hospital Ortopédico de Passo Fundo, Faculdade de Medicina da Universidade de Passo Fundo, Passo Fundo, RS, Brasil
,
Antero Camisa Júnior
1  Grupo de Quadril do Hospital Ortopédico de Passo Fundo, Faculdade de Medicina da Universidade de Passo Fundo, Passo Fundo, RS, Brasil
,
Ezequiel Moreno Ungaretti Lima
1  Grupo de Quadril do Hospital Ortopédico de Passo Fundo, Faculdade de Medicina da Universidade de Passo Fundo, Passo Fundo, RS, Brasil
,
Darby Lira Tisatto
1  Grupo de Quadril do Hospital Ortopédico de Passo Fundo, Faculdade de Medicina da Universidade de Passo Fundo, Passo Fundo, RS, Brasil
,
Marcel Cruz Argoud
1  Grupo de Quadril do Hospital Ortopédico de Passo Fundo, Faculdade de Medicina da Universidade de Passo Fundo, Passo Fundo, RS, Brasil
› Author Affiliations
Further Information

Endereço para correspondência

Bruno Dutra Roos, MD
Grupo de Quadril do Hospital Ortopédico de Passo Fundo, Faculdade de Medicina da Universidade de Passo Fundo
Av. Sete de Setembro, 817, Centro, Passo Fundo, RS 99010-121
Brasil   

Publication History

30 November 2018

22 January 2019

Publication Date:
28 January 2020 (online)

 

Abstract

Objective The purpose of the present study was to evaluate the pelvic bone deformities and its correlation with the acetabular center-edge (CE) angle.

Methods Between August 2014 and April 2015, we prospectively evaluated patients aged between 20 and 60 years old. The exclusion criteria were: metabolic disease, previous hip or spine surgery, radiograph showing hip arthrosis ≥ Tönnis two, severe hip dysplasia, global acetabular overcoverage, acetabular crossover sign, hip deformities from slipped capital femoral epiphysis (SCFE) or Leg-Perthes-Calveé, and bad quality radiographs. At anteroposterior (AP) pelvic radiographs, we have evaluated: the CE angle, the acetabular index (IA), the acetabular crossover sign, the vertical and horizontal superior and inferior pelvic axis (H1: Horizontal line 1, superior pelvic axis; H2: Horizontal line 2, superior pelvic axis; V1: Vertical line, superior pelvic axis; HR: Horizontal line, inferior pelvic axis; VR: Vertical line, inferior pelvic axis). The superior and inferior pelvic axis were considered asymmetric when there was a difference ≥ 5 mm between both sides. Patients were divided into two groups: control and group 1.

Results A total of 228 patients (456 hips) were evaluated in the period. According to the established criteria, 93 patients were included. The mean age was 39.9 years old (20 to 60 years old, standard deviation [SD] = 10,5), and the mean CE angle in the right hip was 31.5° (20 o to 40°), and in the left 32.3° (20 o to 40°). The control group had 38 patients, with asymmetric H1 in 4 cases (10.5%), H2 in 5 (13.1%), V1 in 7 (18.4%), HR in 5 (13.1%) and VR in 1 (2.63%). Group 1 had 55 patients, with asymmetric H1 in 24 cases (43.6%), H2 in 50 (90.9%), V1 in 28 (50.9%), HR in 16 (29.09%) and VR in 8 (14.5%). Comparing both groups, there was statistical significance for H1, H2 and V1 asymmetry (p < 0.001).

Conclusion In the present paper, we observed the correlation between variation in the acetabular CE angle and asymmetry of the superior hemipelvis. The present authors believe that a better understanding of the pelvic morphologic alterations allows a greater facility in the diagnosis of hip articular deformities.


#

Introduction

There is growing evidence in the literature of the association of changes in the morphology of the hip bone and the development of symptoms, as well as the possibility of evolution to chondral joint degeneration. These changes may be related to the femur, the acetabulum, or both.[1] On the acetabular side, frequent morphological alterations include overcoverage (Pincer femoroacetabular impingement [FAI]) and coverage deficiency (developmental dysplasia of the hip [DDH]).[2] [3]

Acetabular overcoverage can be global or focal. Global overcoverage is defined by anteroposterior (AP) pelvis radiography of the center-edge angle (CE)[4] > 40° associated with excess femoral head coverage by the anterior and posterior wall of the acetabulum.[5] Focal overcoverage is defined by the presence of acetabular retroversion, which is a morphological change in which there is structural deviation of the acetabulum in the sagittal plane towards the posterolateral direction. Radiographically, acetabular retroversion is represented by the presence of the sign of the intersection of the acetabular lines.[3] [6] [7] Both changes have been associated with the dynamic impact between the acetabular edge and the femoral head-neck transition, which may result in acetabular lesions of the posteroinferior cartilage and lip, as well as pain.[8]

In acetabular coverage deficiency, a reduced contact area between the femoral head and the acetabulum generates excessive shear force at the acetabular chondrolabral junction, which may lead to the emergence of symptoms and chondral degeneration in the long run. This deficiency is most commonly anterosuperior in the acetabulum, and the diagnosis of DDH is made when the CE angle[4] is < 25° on pelvic AP radiography.[4] [9]

Some authors have proposed that hip development disorders not only affect the proximal femur and the acetabulum, as evidenced by pathologies such as FAI and DDH, but throughout the pelvis.[1] [10] However, there is no consensus on which pelvic bone deformities correlate with acetabular morphological changes. We believe that pelvic bone structural changes and acetabular abnormalities are not isolated findings but are instead part of a continuum of structural changes in pelvic development.

The aim of the present study is to evaluate the pelvic bone deformity and its correlation with the CE angle.


#

Materials and Methods

A prospective case-control study was conducted between August 2014 and April 2015. The study was approved by the Research Ethics Committee, and all of the participants signed the informed consent form.

Participants were invited to the study voluntarily. Inclusion criteria were consecutive patients aged 20 to 60 years old. The exclusion criteria were: metabolic disease, previous hip or spine surgery, radiograph showing hip arthrosis ≥ Tönnis two, severe DDH (CE angle < 20°),[4] [9] global acetabular overcoverage (CE angle > 40° and/or acetabular index [AI] < zero°),[5] sign of acetabular lines intersection (suggesting acetabular retroversion), CE angle asymmetry < 5°, hip deformities from slipped capital femoral epiphysis (SCFE) or Leg-Perthes-Calveé, and bad quality radiographs.[11]

The selected patients underwent pelvic radiography at AP incidence with their feet at 15° of internal rotation, with the tube 120 cm away from the film, and with the radius directed to the center point between the upper edge of the pubic symphysis and a horizontal line connecting both anterosuperior iliac spines. The distance between the coccyx and the pubic symphysis, besides its alignment, were factors considered to evaluate the quality of the radiographs.[11]

The following radiographic studies were evaluated in both hemipelves: CE angle, AI, sign of intersection of acetabular lines, measurement of horizontal and vertical axis of upper hemipelvis (iliac wings - H1, H2 and V1), measurement of the horizontal and vertical axis of the lower hemipelvis (ischium and ilium pubic branches - HR and VR). The definition of the method for measuring the pelvic axes is exemplified in [Figure 1].

Zoom Image
Fig. 1 Exemplification of bilateral pelvic axis measurement method. All lines (H1, H2, V1, HR and VR) are referenced to the line between the teardrops. a) H1 and H2 correspond to the measurement of the horizontal axis of the upper hemipelvis. Initially, a line is defined connecting the upper points of the acetabular roofs (supra-acetabular line). H1 is 2cm above it; H2 is 7cm above it. b) V1 corresponds to the measurement of the vertical axis of the upper hemipelvis. It is the measurement from the highest point of the iliac bone to the supra-acetabular line. c) HR corresponds to the measurement of the horizontal axis of the lower hemipelvis, having as reference a midpoint of the pubic symphysis joint. d) VR corresponds to the measurement of the vertical axis of the lower hemipelvis, having as reference a midpoint of the measurement of the HR.

The measurements of the axis of hemipelves (H1, H2, V1, HR and VR) were considered asymmetrical when, in comparing a hemipelvis in relation to its contralateral side, a difference > 5 mm was found.

The selected patients were separated into two groups: control and group 1.

The control group included patients whose hips had a CE angle with a difference of < 5°, with no sign of acetabular line intersection. Group 1 included patients with CE angle asymmetry ≥ 5°, comparing one hip to the contralateral side, with no sign of acetabular line intersection.

The aim of the present study is to evaluate the correlation between CE angle variation and pelvic bone deformity (H1, H2, V1, HR and/or VR asymmetry), comparing both groups.

The hypothesis is that the presence of CE angle variation correlates with the upper hemipelvis asymmetry (suggesting rotational change of the upper hemipelvis).

To assess homogeneity between the groups, the chi-squared test was applied for age, gender, CE angle and AI. The Fisher exact test was used to analyze the intergroup qualitative variables (H1, H2, V1, HR and VR). In the present study, differences were considered statistically significant when p < 0.05. The software PASW Statistics for Windows, Version 18.0 (SPSS Inc. Chicago, IL, USA) was used in the statistical analysis. A total of 50 radiographs were randomly selected to measure the κ coefficient. Two authors, Roos B. D. and Lima E. M. U., evaluated the radiographs at different times, with an interobserver agreement of 0.72.


#

Results

The total number of patients evaluated during the period was 228 (456 hips). According to the established criteria, 93 patients were included in the present study, 49 males and 44 females. The excluded patients are represented in [Table 1]. The average age was 39.9 years old (ranging from 20 to 60 years old, standard deviation [SD] = 10.52), the mean right hip CE angle was 31.5° (ranging from 20° to 40°, SD = 5.30) and the left was 32.3° (ranging from 20° to 40°, SD = 5.11). The mean AI was 5.14 (ranging from 0 to 10, SD = 2.97) in the right hip and 5.17 (ranging from 0 to 10, SD = 3.09) in the left hip.

Table 1

Exclusion Criteria

Excluded

Previous hip or spine surgery

6

Arthrosis ≥ Tönnis 2

12

Severe DDH

8

Global acetabular overcoverage

14

Sign of intersection of acetabular lines

60

Asymmetry of CE angle 1° or 2°

11

Asymmetry of CE angle + unilateral acetabular retroversion

9

SCFE or Legg-Perthes-Calveé

3

Radiography without adequate quality

12

Total

135

There were 38 patients included in the control group, with mean axes measurements of H1, H2, V1, HR and VR presented in [Table 2]. Regarding H1, asymmetric measurement was found in 4 cases (10.5%), 5 cases in H2 (13.1%), 7 cases in V1 (18.4%), 5 cases in HR (13.1%), and 1 case in VR (2.63%).

Table 2

Groups

H1 R

H1 L

H2 R

H2 L

V1 R

V1 L

HR R

HR L

VR R

VR L

Control

1

71

71

94

93

101

102

67

67

67

68

2

57

65

91

92

92

91

96

92

55

51

3

55

58

85

87

103

100

90

88

80

79

4

51

52

86

89

95

98

93

91

58

57

5

43

43

90

80

115

115

80

88

55

55

6

49

49

97

98

112

112

90

90

57

57

7

66

67

88

88

110

110

76

76

68

69

8

55

61

92

100

126

124

91

100

66

68

9

50

50

111

113

134

134

83

84

60

60

10

73

75

108

106

133

131

91

91

65

67

11

88

88

106

106

131

139

81

90

77

77

12

64

62

100

99

131

133

85

85

53

53

13

72

72

102

100

126

121

76

78

88

90

13

58

60

105

105

137

137

90

88

51

53

15

57

60

110

115

105

107

87

85

75

73

16

55

57

85

87

133

134

85

83

52

50

17

78

78

108

109

132

127

91

90

69

67

18

62

60

126

124

137

143

88

87

60

61

19

72

70

100

100

142

142

80

82

80

80

20

57

55

105

105

151

141

96

97

59

59

21

60

60

103

102

112

112

84

82

77

76

22

58

59

94

92

110

110

94

86

67

66

23

56

56

98

97

97

98

89

89

77

77

24

51

53

102

101

110

110

98

98

78

78

25

50

50

98

98

111

112

89

91

57

56

26

56

57

88

88

110

110

76

76

69

69

27

65

68

86

88

104

101

89

88

81

80

28

50

52

87

90

95

97

93

93

58

56

29

50

50

112

113

134

134

83

83

60

61

30

64

65

108

108

132

131

90

89

66

67

31

64

63

99

98

132

133

85

86

54

53

32

58

60

105

105

137

137

82

84

53

54

33

55

57

85

86

130

131

85

85

52

51

34

82

82

100

100

140

138

81

82

77

77

35

56

55

103

102

112

112

82

80

76

76

36

55

54

99

100

97

96

90

90

77

77

37

63

64

102

101

107

109

95

95

75

75

38

80

80

100

99

140

142

80

80

82

82

Mean

60.68

61.53

99.05

119.89

119.84

86.34

86.55

66.61

66.45

98.89

Standard Deviation

10.212

10.01

9.291

16.256

16.045

6.671

6.5

10.612

10.84

9.282

In group 1, 55 patients were included. The average axis measurements of H1, H2, V1, HR and VR are presented in [Table 3]. Regarding H1, asymmetric measurement was found in 24 cases (43.6%), 50 cases in H2 (90.9%), 28 cases in V1 (50.9%), 16 cases in HR (29.09%), and 8 cases in VR (14.5%) ([Figure 2]).

Table 3

Groups

H1 R

H1 L

H2 R

H2 L

V1 R

V1 L

HR R

HR L

VR R

VR L

Acetabular inclination

1

45

45

90

80

100

99

105

105

68

66

2

84

81

90

92

170

170

76

76

72

70

3

60

50

110

100

100

100

80

80

72

74

4

50

45

100

94

100

105

96

96

64

63

5

62

62

107

100

113

115

87

87

72

72

6

55

50

104

100

102

104

88

88

77

75

7

53

58

72

89

105

109

75

73

63

70

8

60

54

92

86

112

110

88

86

67

66

9

56

57

110

117

110

115

97

107

64

62

10

50

50

90

98

100

100

70

74

67

65

11

73

64

107

97

112

112

69

70

65

65

12

57

51

92

93

107

107

80

79

70

68

13

50

58

92

97

128

123

90

92

47

47

13

82

73

114

110

134

139

93

90

77

77

15

69

69

120

124

138

143

90

80

84

75

16

55

60

118

128

146

145

88

87

52

50

17

52

58

76

80

127

124

89

89

59

59

18

70

70

112

119

135

138

90

90

58

60

19

55

48

115

100

128

108

85

83

40

42

20

67

83

116

120

136

136

75

66

55

53

21

61

62

118

109

135

143

85

75

87

72

22

51

40

85

92

124

127

83

86

57

57

23

49

49

148

123

144

146

95

93

60

60

24

80

82

104

97

119

120

73

75

85

83

25

47

46

82

88

118

116

86

84

57

55

26

53

53

101

96

109

132

82

84

75

73

27

69

69

102

98

138

129

92

90

60

58

28

62

60

95

94

134

135

95

94

62

61

29

42

42

94

102

144

149

102

95

72

67

30

55

55

98

90

145

153

94

92

85

84

31

60

60

75

81

113

112

82

83

85

73

32

62

55

104

94

98

104

70

62

66

64

33

57

61

102

108

108

104

86

88

77

77

34

60

61

96

102

102

102

68

68

72

72

35

44

44

83

91

97

97

77

76

65

65

36

72

72

119

124

137

143

90

82

83

81

37

55

61

120

128

145

145

87

87

51

45

38

52

59

75

80

127

123

89

89

72

71

39

67

67

113

119

135

139

92

90

58

60

40

56

48

110

100

128

108

85

83

41

42

41

66

83

116

121

136

136

71

67

54

44

42

61

63

117

109

136

143

85

76

74

72

43

51

41

86

92

124

127

82

86

60

60

44

49

48

140

123

144

144

95

95

58

58

45

80

82

104

96

119

121

73

74

85

83

46

48

46

82

89

118

116

87

84

55

58

47

54

53

101

95

109

132

82

84

74

73

48

70

69

102

98

138

129

92

91

59

58

49

44

42

94

101

143

149

98

92

65

66

50

50

50

98

89

145

153

94

93

70

69

51

60

61

76

81

113

113

83

83

75

73

52

62

55

104

93

98

104

70

62

62

61

53

57

62

101

108

108

104

86

86

72

72

54

61

61

96

101

103

103

68

66

60

63

55

45

44

83

92

97

96

77

77

60

59

Mean

58.49

58.04

100.51

122.44

123.62

84.85

83.45

66.8

64.29

100.93

Standard Deviation

10.011

11.41

13.179

17.359

18.27

9.093

9.867

11.453

10.544

15.608

Zoom Image
Fig. 2 Case example of group 1. a) Asymmetry of the measurements of the horizontal axis of the upper hemipelvis (H1 and H2) is evinced. b) Asymmetry of the vertical axis measurement of the upper hemipelvis (V1) is evdenced. c) Symmetry of the measurements of the horizontal and vertical axes of the lower hemipelves (HR e VR) is evinced.

The groups were considered homogeneous, since they did not differ in relation to gender, age, CE angle and AI (p = 0.086). In the comparison between the control group and group 1 ([Table 4]), a statistically significant difference was observed for the asymmetry of the measurements in H1 (p < 0.001), H2 (p < 0.001) and V1 (p = 0.005). For the measures HR and VR, no statistically significant difference was observed (p = 0.082; p = 0.077).

Table 4

H1

H2

V1

VR

HR

Asymmetry

Yes

No

Yes

No

Yes

No

Yes

No

Yes

No

Total

Inclination

24

31

50

5

28

27

0

0

16

39

55

Acetabular

85.70%

47.70%

90.90%

13.20%

77.80%

47.40%

0.00%

0.00%

76.20%

54.20%

59.10%

Control

4

34

5

33

8

30

0

0

5

33

38

14.30%

52.30%

9.10%

86.80%

12.20%

52.60%

0.00%

0.00%

13.80%

45.80%

40.90%

Total

28

65

55

38

36

57

0

0

21

69

88

100%

100%

100%

100%

100%

100%

100%

100%

100%

100%

100%

Significance

p = 0.001

p < 0.001

p = 0.005

p = 000

p = 0.82


#

Discussion

There is growing evidence in the literature of the association of bone morphological changes in the hip region and the development of symptoms, as well as the possibility of evolution to joint chondral degeneration. These changes may be related to the femur, the acetabulum, or both.[1] Considering the acetabulum, as frequent morphological alterations we can find the overcoverage (FAI) and poor coverage (DDH).[2] [3]

Some authors have proposed that hip development disorders not only affect the proximal femur and the acetabulum, as evidenced by pathologies such as FAI and DDH, but throughout the pelvis.[1] [10] However, there is no consensus on which pelvic bone deformities correlate with acetabular morphological changes. We believe that a better understanding of these dysmorphisms may lead to easier diagnosis of hip joint pathologies.

Fujii et al[12] performed a study evaluating the axial plane rotational alignment of the iliac bone in CT scans of patients with DDH, and questioned whether rotational deformity was present in the DDH; whether rotation angles were correlated with acetabular version and inclination; and whether the rotation angles were correlated with the acetabulum deficiency region. The results showed that the internal rotation (IR) of the upper third of the hemipelvis (from upper part of the iliac bone to the anterior inferior iliac spine [AIIS]) correlates with the diagnosis of DDH.[12] Iliac bone IR in patients with DDH was also observed by authors as Kumeta et al[13] and Suzuki,[14] and it is believed that, with this deformity, the acetabulum tends to rotate anterosuperiorly, resulting in decreased anterosuperior coverage and increased posterior coverage.

Also, Fujii et al[12] correlated external rotation of the lower third of the hemipelvis (between the iliac bone and the ischiopubic branch) with acetabular retroversion in patients with DDH. This finding is corroborated by Kalberer et al.,[15] who observed the prominence of the ischial spine in patients with acetabular retroversion.

These observations suggest that pelvic bone structural changes and acetabular abnormalities are not isolated findings, but are instead part of a continuum of structural developmental changes.

In our study, correlation between CE angle variation and upper hemipelvis asymmetry was found. Like Fujii et al,[13] we can see that upper hemipelvis dysmorphisms, resulting from bone development disorders, may influence acetabular morphology. However, we sought to analyze these findings in a group of patients without severe DDH (CE angle < 20°).

To our knowledge, this is the first study that seeks to establish correlations between pelvic dysmorphisms and variation of the CE angle, in the 90th percentile, for the CE angle of the general population (20-40°).[16]


#

Conclusion

In the present study, a correlation between CE angle variation and upper hemipelvis asymmetry was found. These findings suggest that upper hemipelves dysmorphism due to bone development disorders may influence acetabular morphology.


#
#

Conflito de Interesses

Os autores declaram não haver conflito de interesses.

* Study conducted at the Hip Group of the Hospital Ortopédico de Passo Fundo, Faculdade de Medicina da Universidade de Passo Fundo, Passo Fundo, RS, Brazil.



Endereço para correspondência

Bruno Dutra Roos, MD
Grupo de Quadril do Hospital Ortopédico de Passo Fundo, Faculdade de Medicina da Universidade de Passo Fundo
Av. Sete de Setembro, 817, Centro, Passo Fundo, RS 99010-121
Brasil   


Zoom Image
Fig. 1 Exemplificação do método de aferição dos eixos pélvicos bilateralmente. Todas as linhas (H1, H2, V1, HR e VR) têm como referência a linha entre as gotas de lágrima. a) H1 e H2 correspondem à aferição do eixo horizontal da hemipelve superior. Inicialmente é definida uma linha ligando os pontos mais superiores dos tetos acetabulares (linha supra-acetabular). H1 localiza-se 2 cm acima desta; H2 localiza-se 7 cm acima desta. b) V1 corresponde à aferição do eixo vertical da hemipelve superior. É a medida do ponto mais superior do osso ilíaco até a linha supra-acetabular. c) HR corresponde à aferição do eixo horizontal da hemipelve inferior, tendo como referência um ponto médio da articulação da sínfise púbica. d) VR corresponde à aferição do eixo vertical da hemipelve inferior, tendo como referência um ponto médio da aferição HR.
Zoom Image
Fig. 1 Exemplification of bilateral pelvic axis measurement method. All lines (H1, H2, V1, HR and VR) are referenced to the line between the teardrops. a) H1 and H2 correspond to the measurement of the horizontal axis of the upper hemipelvis. Initially, a line is defined connecting the upper points of the acetabular roofs (supra-acetabular line). H1 is 2cm above it; H2 is 7cm above it. b) V1 corresponds to the measurement of the vertical axis of the upper hemipelvis. It is the measurement from the highest point of the iliac bone to the supra-acetabular line. c) HR corresponds to the measurement of the horizontal axis of the lower hemipelvis, having as reference a midpoint of the pubic symphysis joint. d) VR corresponds to the measurement of the vertical axis of the lower hemipelvis, having as reference a midpoint of the measurement of the HR.
Zoom Image
Fig. 2 Exemplificação de caso do grupo 1. a) Evidencia-se assimetria das aferições do eixo horizontal da hemipelve superior (H1 e H2). b) Evidencia-se assimetria da aferição do eixo vertical da hemipelve superior (V1). c) Evidencia-se simetria das aferições dos eixos horizontal e vertical da hemipelve inferior (HR e VR).
Zoom Image
Fig. 2 Case example of group 1. a) Asymmetry of the measurements of the horizontal axis of the upper hemipelvis (H1 and H2) is evinced. b) Asymmetry of the vertical axis measurement of the upper hemipelvis (V1) is evdenced. c) Symmetry of the measurements of the horizontal and vertical axes of the lower hemipelves (HR e VR) is evinced.