Estimation of pelvic tilt on anteroposterior X-rays--a comparison of six parameters.
OBJECTIVE
To compare six different parameters described in literature for estimation of pelvic tilt on an anteroposterior pelvic radiograph and to create a simple nomogram for tilt correction of prosthetic cup version in total hip arthroplasty.


METHODS
Simultaneous anteroposterior and lateral pelvic radiographs are taken routinely in our institution and were analyzed prospectively. The different parameters (including three distances and three ratios) were measured and compared to the actual pelvic tilt on the lateral radiograph using simple linear regression analysis.


METHODS
One hundred and four consecutive patients (41 men, 63 women with a mean age of 31.7 years, SD 9.2 years, range 15.7-59.1 years) were studied.


RESULTS
The strongest correlation between pelvic tilt and one of the six parameters for both men and women was the distance between the upper border of the symphysis and the sacrococcygeal joint. The correlation coefficient was 0.68 for men (P<0.001) and 0.61 for women (P<0.001). Based on this linear correlation, a nomogram was created that enables fast, tilt-corrected cup version measurements in clinical routine use.


CONCLUSIONS
This simple method for correcting variations in pelvic tilt on plain radiographs can potentially improve the radiologist's ability to diagnose and interpret malformations of the acetabulum (particularly acetabular retroversion and excessive acetabular overcoverage) and post-operative orientation of the prosthetic acetabulum.
Tannast
M
M
Department of Orthopedic Surgery, Inselspital, University of Bern, Bern, Switzerland.
Murphy
S B
SB
Langlotz
F
F
Anderson
S E
SE
Siebenrock
K A
KA
D000293:Adolescent; D000328:Adult; D019644:Arthroplasty, Replacement, Hip; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D049451:Nomograms; D010384:Pelvic Bones / Q000000981:diagnostic imaging*; D011446:Prospective Studies; D011859:Radiography