BACKGROUND: Accurate measurement of acetabular component position is crucial for evaluating instability, impingement, accelerated wear, pain, and component failure after total hip arthroplasty (THA). Acetabular anteversion remains difficult to accurately determine, even though inclination is readily evaluated on radiographs. Numerous radiographic and computed tomography (CT)-based techniques have been described, each with distinct advantages and limitations.
METHODS: The commonly used radiographic and CT-based techniques for assessing acetabular component anteversion and inclination after THA were evaluated by a narrative review of the literature. Measurement technique, precision, repeatability, technological constraints, and the impact of the pelvic position and spino-pelvic mechanics were emphasized.
RESULTS: The Woo and Morrey, Lewinnek, Liaw, and Widmer radiographic techniques are frequently used. While there is conflicting information regarding the superiority of any one of these radiographic techniques, some studies have shown reasonable correlation between radiographic and CT-based assessments. In patients who have abnormal spino-pelvic mechanics or component malposition, CT-based examination may offer more accuracy and reproducibility. However, as unilateral hip CT scans do not sufficiently establish the pelvic reference plane required for accurate determination of version or inclination, proper CT assessment necessitates imaging of the complete pelvis.
CONCLUSIONS: After THA, acetabular component position can be evaluated using a variety of imaging techniques. While radiographs remain the most widely available modality, CT may provide the most reproducible assessment of component orientation when whole-pelvis imaging is obtained using an appropriate pelvic reference frame. Understanding the strengths and limitations of each approach is essential when evaluating painful, unstable, or mechanically failing THA.
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