The difference between the radiographic and the operative angle of inclination of the acetabular component in total hip arthroplasty: use of a digital protractor and the circumference of the hip to improve orientation.
A high radiographic inclination angle (RI) contributes to accelerated wear and has been associated with dislocation after total hip arthroplasty (THA). With freehand positioning of the acetabular component there is a lack of accuracy, with a trend towards a high radiographic inclination angle. The aim of this study was to investigate whether the use of a digital protractor to measure the operative inclination angle (OI) could improve the positioning of the acetabular component in relation to a 'safe zone'. We measured the radiographic inclination angles of 200 consecutive uncemented primary THAs. In the first 100 the component was introduced freehand and in the second 100 a digital protractor was used to measure the operative inclination angle. The mean difference between the operative and the radiographic inclination angles (∆RI-OI) in the second cohort was 12.3° (3.8° to 19.8°). There was a strong correlation between the circumference of the hip and ∆RI-OI. The number of RI outliers was significantly reduced in the protractor group (p = 0.002). Adjusting the OI, using a digital protractor and taking into account the circumference of the patient's hip, improves the RI significantly (p < 0.001) and does not require additional operating time.
Lievensberg Hospital, 4624 VT Bergen Op Zoom, The Netherlands.
G
G
Meermans
Lievensberg Hospital, 4624 VT Bergen Op Zoom, The Netherlands.
I
I
Goetheer-Smits
Lievensberg Hospital, 4624 VT Bergen Op Zoom, The Netherlands.
R F
RF
Lim
Lievensberg Hospital, 4624 VT Bergen Op Zoom, The Netherlands.
W J
WJ
Van Doorn
Lievensberg Hospital, 4624 VT Bergen Op Zoom, The Netherlands.
J
J
Kats
D000077:Acetabulum / Q000033:anatomy & histology* / Q000000981:diagnostic imaging* / Q000601:surgery; D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000295:instrumentation / Q000379:methods; D001837:Body Weights and Measures; D061827:Dimensional Measurement Accuracy; D005260:Female; D006615:Hip / Q000033:anatomy & histology; D006621:Hip Joint / Q000033:anatomy & histology* / Q000000981:diagnostic imaging* / Q000601:surgery; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D055641:Mathematical Concepts; D008875:Middle Aged; D011446:Prospective Studies; D011859:Radiography
Acetabular component; Hip arthroplasty; Inclination