Radiographic anatomic structure of the arthritic acetabulum and its influence on total hip arthroplasty

Acetabular bone structure is not the same in all patients and can be define d by the radiolucent triangle superior to the acetabulum. Of 132 hips, 81 h ad an isosceles triangular shape, which was named type A acetabulum. Forty- six hips had an extension of the triangle into the teardrop, which created a thickened medial wall and was named type B. Five hips had a right-angle t riangle, which was found only with congenital disease of the hip and was na med type C. The density of the superior acetabular bone in the triangle cou ld be normally radiolucent (stage I), have vertical and transverse trabecul ae throughout the triangle (stage II), or have the triangle filled with bon e and cysts (stage III). The relationship between progressive radiolucent l ines and acetabular type showed that type A3 (thin medial wall with dense t riangle bone) had the highest incidence of progressive radiolucent lines (P < .05).