The development of acetabular retroversion in children with Legg-Calvé-Perthes disease.
BACKGROUND
Ezoe et al showed that the prevalence of acetabular retroversion in adults with Legg-Calvé-Perthes disease (LCPD) was 42% versus 6% in normal controls. Our purpose was to study the development of acetabular retroversion in children with LCPD and perhaps draw conclusions regarding cause and effect.


METHODS
We reviewed all 271 patients with LCPD seen at our institution to identify those patients with axial imaging before closure of the triradiate cartilage. Fifty-three hips (44 patients) formed our study population; the 35 normal hips in those patients with unilateral disease served as an internal control. Acetabular version was measured on the axial cut with the largest femoral head cross-section. Diseased versus control hips were compared using a paired t test. Two disease-severity subgroups, Herring A or B (42 hips) and B/C or C (11 hips), were compared using an independent-samples t test. In those patients followed past skeletal maturity (16 of 53 hips), we evaluated final AP pelvic radiographs for acetabular retroversion (presence of a crossover sign).


RESULTS
Before skeletal maturity, all but 1 patient in our series demonstrated positive acetabular version (anteversion). We found no significant difference between the diseased and control hips: mean acetabular version in LCPD hips was 13.6 +/- 4.3 versus 15.4 +/- 5.4 degrees in unaffected hips. More severe cases (B/C or C) exhibited significantly more relative retroversion (10.8 degrees) than less severe cases (14.6 degrees, P = 0.047). Of the 16 hips followed past skeletal maturity, 5 demonstrated crossover signs on anteroposterior pelvic radiographs, indicating a 31% prevalence of acetabular retroversion.


CONCLUSIONS
Early after diagnosis, the prevalence of acetabular retroversion in our skeletally immature children with LCPD was extremely rare (1.8%), and there was no significant difference in version between the normal hips and hips with LCPD. However, over time, a child with a more deformed femoral head is more likely to develop acetabular retroversion, suggesting a cause-and-effect relationship.


METHODS
Level III (case-control).
Sankar
Wudbhav N
WN
Division of Orthopaedic Surgery, The Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA.
Flynn
John M
JM
D000077:Acetabulum; D002648:Child; D002675:Child, Preschool; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D006617:Hip Dislocation / Q000000981:diagnostic imaging / Q000209:etiology* / Q000473:pathology; D006801:Humans; D007223:Infant; D007873:Legg-Calve-Perthes Disease / Q000150:complications* / Q000175:diagnosis; D008279:Magnetic Resonance Imaging; D008297:Male; D010865:Pilot Projects; D011379:Prognosis; D014057:Tomography, X-Ray Computed