New cross-table lateral radiography method for measuring acetabular component anteversion in total hip arthroplasty: a prospective study of 93 primary THA.
BACKGROUND
Various methods have been described for measuring acetabular component anteversion. However, accurate measurement of anteversion is difficult. We herein propose a new method using cross-table lateral (CL) radiography performed with the contralateral hip flexed to 45° (45° flexed CL radiography). The main purpose of this study was to evaluate the reliability and validity of this new method.


METHODS
The study group included 93 patients who underwent total hip arthroplasty (THA). All hips were evaluated with computed tomography (CT) and both standard and 45° flexed CL radiographs to measure acetabular component anteversion the week after THA. The intraobserver and interobserver reliability of each measurement was assessed. Plain radiography measurements were compared with reference CT measurements to evaluate their validity.


RESULTS
All measurements had excellent intraobserver and interobserver reliability, and plain radiography measurements correlated well with CT measurements. The mean measurements were 21.9° (3°-39°) with CT, 24.9° (7°-47°; p<0.001) with standard CL radiographs, and 22.5° (7°-43°; p = 0.112) with 45° flexed CL radiographs.


CONCLUSIONS
The anteversion values measured with our new method were closer to the CT values used as a reference standard than those with standard CL radiographs. Our new method appears to be reliable and valid for measuring acetabular component anteversion.
 Department of Orthopaedic Surgery, Fukuoka University Faculty of Medicine, Nanakuma, Fukuoka - Japan.
Hajime
H
Seo
 Department of Orthopaedic Surgery, Fukuoka Sanno Hospital, Momochihama, Fukuoka - Japan.
Masatoshi
M
Naito
 Department of Orthopaedic Surgery, Iida Hospital, Miyakonojo, Miyazaki - Japan.
Yoshinari
Y
Nakamura
 Department of Orthopaedic Surgery, Fukuoka University Faculty of Medicine, Nanakuma, Fukuoka - Japan.
Koichi
K
Kinoshita
 Department of Orthopaedic Surgery, Fukuoka University Chikushi Hospital, Chikushino, Fukuoka - Japan.
Tomohiro
T
Nomura
 Department of Orthopaedic Surgery, Fukuoka University Faculty of Medicine, Nanakuma, Fukuoka - Japan.
So
S
Minokawa
 Department of Orthopaedic Surgery, Fukuoka University Faculty of Medicine, Nanakuma, Fukuoka - Japan.
Tomohiko
T
Minamikawa
 Department of Orthopaedic Surgery, Fukuoka University Faculty of Medicine, Nanakuma, Fukuoka - Japan.
Takuaki
T
Yamamoto
D000077:Acetabulum / Q000000981:diagnostic imaging* / Q000601:surgery; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D056888:Patient Positioning / Q000379:methods*; D011446:Prospective Studies; D012372:ROC Curve; D015203:Reproducibility of Results; D014057:Tomography, X-Ray Computed / Q000379:methods*; D055815:Young Adult