[Preoperative diagnostic imaging and planning]

A correctly chosen radiographic technique, good image quality and correct image interpretation are the basis of all surgical planning. It is only when the cause and extent of the hip pathology are evaluated carefully based on radiologic imaging that the long-term surgical success of hip and pelvis osteotomy is possible.

This article gives an overview over performance, quality criteria and interpretation of the most important radiographic images of the hip.

The anterior-posterior pelvic view is the most important radiograph for planning an osteotomy of the hip. Besides the evaluation of the underlying cause, the caput-collum-diaphyseal angle (CCD) can be calculated from the pelvic view. For the evaluation of the real femoral antetorsion angle (AT-angle) a Rippstein II projection needs to be performed. Lequesne's false-profile view is important to assess the ventral part of the joint, especially to measure the anterior coverage of the femoral head. In neonates and children, the pelvic hip view is important to assess hip dysplasia. The relevant characteristic lines and angles that should evaluated in the pelvic hip view are the Hilgenreiner line, of the Perkin line, the acetabular angle (AC-angle) and Reimers migration index. Computed tomography allows 3D surgical planning and is the most accurate technique for measuring the AT-angle.

Magnet resonance imaging is of help for the evaluation of hip pathologies such as labrum and cartilage injuries. MRI for this purpose should always be performed as an MR-arthrography.