Measuring Acetabular Cup Orientation on Antero-Posterior Radiographs of the Hip after Total Hip Arthroplasty with a Vector Arithmetic Radiological Method. Is It Valid and Verified for Daily Clinical Practice?
OBJECTIVE
The aim of this prospective study is to validate a vector arithmetic method for measuring acetabular cup orientation after total hip arthroplasty (THA) and to verify the clinical practice.


METHODS
We measured cup anteversion and inclination of 123 patients after cementless primary THA twice by two examiners on AP pelvic radiographs with a vector arithmetic method and compared with a 3D-CT based reconstruction model within the same radiographic coronal plane.


RESULTS
The mean difference between the radiographic and the 3D-CT measurements was - 1.4° ± 3.9° for inclination and 0.8°± 7.9° for anteversion with excellent correlation for inclination (r = 0.81, p < 0.001) and moderate correlation for anteversion (r = 0.65, p < 0.001). The intraclass correlation coefficient for measurements on radiographs ranged from 0.98 (95 %-CI: 0.98; 0.99) for the first observer to 0.94 (95 %-CI: 0.92; 0.96) for the second observer. The interrater reliability was 0.96 (95 %-CI: 0.93; 0.98) for inclination and 0.93 (95 %-CI: 0.85; 0.96) for anteversion.


CONCLUSIONS
The largest errors in measurements were associated with an extraordinary pelvic tilt. In order to get a valuable measurement for measuring cup position after THA on pelvic radiographs by this vector arithmetic method, there is a need for a correct postoperative ap view, with special regards to the pelvic tilt for the future.


CONCLUSIONS
• Measuring acetabular cup orientation on anteroposterior radiographs of the hip after THA is a helpful procedure in everyday clinical practice as a first-line imaging modality• CT remains the golden standard to accurately determine acetabular cup position.• Future measuring on radiographs for cup orientation after THA should account for integration of the pelvic tilt in order to maximize the measurement accuracy. Citation Format: • Craiovan B, Weber M, Worlicek M et al. Measuring Acetabular Cup Orientation on Antero-Posterior Radiographs of the Hip after Total Hip Arthroplasty with a Vector Arithmetic Radiological Method. Is It Valid and Verified for Daily Clinical Practice?. Fortschr Röntgenstr 2016; 188: 574 - 581.
Orthopedic Surgery, University Medical Center Regensburg, Bad Abbach/Regensburg, Germany.
B
B
Craiovan
Orthopedic Surgery, University Medical Center Regensburg, Bad Abbach/Regensburg, Germany.
M
M
Weber
Orthopedic Surgery, University Medical Center Regensburg, Bad Abbach/Regensburg, Germany.
M
M
Worlicek
Orthopedic Surgery, University Medical Center Regensburg, Bad Abbach/Regensburg, Germany.
M
M
Schneider
Orthopedic Surgery, University Medical Center Regensburg, Bad Abbach/Regensburg, Germany.
H R
HR
Springorum
Center for Clinical Studies, University Medical Center Regensburg, Germany.
F
F
Zeman
Orthopedic Surgery, University Medical Center Regensburg, Bad Abbach/Regensburg, Germany.
J
J
Grifka
Orthopedic Surgery, University Medical Center Regensburg, Bad Abbach/Regensburg, Germany.
T
T
Renkawitz
D000077:Acetabulum / Q000000981:diagnostic imaging* / Q000601:surgery*; D006622:Hip Prosthesis; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008432:Mathematical Computing; D015588:Observer Variation; D011183:Postoperative Complications / Q000000981:diagnostic imaging*; D011446:Prospective Studies; D011474:Prosthesis Design; D017755:Prosthesis Fitting / Q000379:methods*; D015203:Reproducibility of Results; D025321:Surgery, Computer-Assisted / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000379:methods*