Anteversion of the Acetabular Cup Determined by Digital Radiographic Software as Compared to CT-Based Measurement

Abstract

AIM: Precision in determining cup positioning in patients after total hip arthroplasty (THA) is critical, especially in seek for the cause of symptoms in cases of postoperative pain, excessive wear and instability. Computed tomography scans (CT) were found to be superior at measuring the anteversion of the acetabular cup as compared to measurements performed on printed radiographs. The purpose of the present study was to compare acetabular anteversion measured on digital radiographs with dedicated software to measurements carried out via CT.

METHODS: CT scans and radiograph exams were obtained from 62 patients after THA. Acetabular cup anteversion was measured from CT by CT-based image analysis software (Amira©) and from digital radiographs using dedicated measurement tool of a digital software (TraumaCAD©). Anteversion angles of the acetabular cup were calculated and compared.

RESULTS: Radiographic calculated acetabular anteversion angles were significantly lower than CT measurements (average difference of -13.8, p < 0.001), with a moderate correlation between methods (r = 0.534; p < 0.001). There was a significant correlation between radiographic error and anteversion angle (r = 0.910; p < 0.001), with the radiographs showing greater underestimation of the angle at greater angles.

CONCLUSIONS: Digital radiographic shows imprecision in measuring acetabular cup anteversion. Clinicians must consider this when making clinical decisions based on these radiographs.