Acetabular retroversion

Last revised by Henry Knipe on 26 Jul 2022

Acetabular retroversion denotes an abnormal posterior angulation of the superolateral acetabular rim, resulting in excessive coverage of the femoral head and metaphysis along the anterior border 1,2.

Acetabular retroversion is a common abnormality affecting 5 to 20% of the general population. It occurs in 16 to 25% of dysplastic hips and affects 31 to 49% of patients with Legg-Calvé-Perthes disease, and 36 to 76% of those diagnosed with slipped femoral epiphysis 2.

The condition is most often caused by an abnormal prominence of the anterosuperior part of the acetabular rim, rather than a shallow posterosuperior rim, entailing a partial overcoverage of the femoral head. Acetabular retroversion is a form of pincer morphology and predisposes to femoroacetabular impingement. It is also a risk factor for early-onset osteoarthritis of the hip, as the decreased area and poor orientation of the posterior acetabular wall result in the formation of stress zones with increased wear and inhomogeneous load distribution throughout the articular surface 1,2

Major forms of acetabular retroversion:

Proper assessment of the acetabular configuration necessitates perfectly centered AP radiographs of the pelvis, which should be the first diagnostic imaging test to assess acetabular retroversion. 

Signs of acetabular retroversion:

Quantitative measures of acetabular orientation and coverage (on radiographs):

  • lateral center-edge angle (Wiberg angle): <20° indicates dysplasia, whilst >30–40° signals acetabular overcoverage
  • acetabular index (Tönnis angle):  >13° indicates hip dysplasia, while values close to or less than 0° is caused by acetabular overcoverage
  • alpha angle: >55° indicates a cam morphology
  • anterior center-edge angle (Lequesne angle): >20° indicates anterior overcoverage

The acetabular version can be measured precisely on CT/MRI in the axial plane, where it is formed by a line perpendicular to the horizontal axis of the pelvis, and a line connecting the most anterior and posterior points of the acetabular margin. Normal range is between 12-20° 1,2

The main goal of treatment is to prevent degenerative sequelae by early correction of the biomechanical integrity of the joint. It is primarily surgical: periacetabular osteotomy or acetabular rim reconstruction (osteochondroplasty) are the most commonly performed surgical interventions 1,2

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