A new tilt on pelvic radiographs: a pilot study.
OBJECTIVE
The aim of this study was to evaluate pelvic tilt on commonly performed measurements on radiography in primary protrusio acetabuli and developmental dysplasia of the hip.


METHODS
A dry assembled pelvis and spine skeleton was positioned in an isocentric skull unit and films exposed with increasing degrees of angulation of pelvic tilt. The films were then read by two independent readers for seven different measurements used to evaluate the hips and acetabular: acetabular line to ilioischial line, teardrop appearance, intercristal/intertuberous ratio, co-ordinates of femoral head, centre edge angle, acetabular depth/width ratio and acetabular angle.


RESULTS
There was so much variation in the protrusio results that no formal recommendation of any standard radiographic test can be given. Only the inter tuberous distance is not effected by pelvic tilt. The acetabular angles for developmental dysplasia of the hip showed the most potential with pelvic tilt below 15 degrees.


CONCLUSIONS
As pelvic tilt increases, measurements used in protusio become unreliable, and computed tomography/magnetic resonance imaging are probably going to be more accurate as one can directly visualise pelvic intrusion. We recommend a lateral view to assess the degree of pelvic tilt in patients with protrusion to ensure these measurements are valid.
Department of Radiology, North Staffordshire Royal Infirmary, Princes Road, Hartshill, Stoke-on-Trent, Staffordshire ST4 7LN, UK. paula.richards@uhns.nhs.uk
P J
PJ
Richards
J M
JM
Pattison
J
J
Belcher
R W
RW
Decann
Suzanne
S
Anderson
C
C
Wynn-Jones
D000077:Acetabulum / Q000002:abnormalities / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D002102:Cadaver; D006618:Hip Dislocation, Congenital / Q000000981:diagnostic imaging*; D006621:Hip Joint / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D006801:Humans; D010865:Pilot Projects; D011859:Radiography; D012016:Reference Values