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

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.

Keywords: acetabulum; femur head; hip dislocation.

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.

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.

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.

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).