Measurements And Observations Of Common Pelvic Radiographic Parameters In More Than Two Thousands Normal Chinese Hips

ObjectiveThis study was aimed at disclosing the developmental process of normal hips reflected in pelvic radiographs and offering normal reference to clinical diagnosis and follow-ups of hip diseases. Regular radiographic parameters were measured on more than 2000 normal anterior-posterior pelvic radiographs of all age groups. The reference ranges of acetabular index, Sharp acetabular angle and the center-edge angle of Wiberg were obtained and corresponding line charts were drawn depicting their relationship with age.MethodsWe retrospectively selected 2333 standard anterior-posterior pelvic radiographs taken for exclusion of trauma or hip diseases in our hospital between September 2007 to March and proved normal by two radiological specialists and two orthopedists.1494 of them were of children older than age four. Acetabular indexes were measured on radiographs of children below age ten. The data were categorized by month before age one and by year afterwards. Sharp acetabular angle were measured after age ten. These were categorized by year before adulthood and by decade afterwards. Center-edge angle of Wiberg were measured in all children older than four. Statistical analysis was carried out on the data and line charts were drawn relating these parameters with age. Meanwhile the acetabula were categorized according to Ogata's classification and the relationship between different measurements of center-edge angle in typeⅢ,Ⅵacetabula were discussed.ResultsThe average acetabular index is 28.39±4.40°at birth which declines rapidly in the first three months. It declines to 22.17±3.56°at age one. Then another fast declination is observed during age 1-5 after which it becomes 15.57±3.95°at age five. This tendency goes smoother afterwards with a declination of about 3°. Generally the acetabular angle of girls is 1-2°greater than that of boys(P<0.05).The Sharp acetabular angle is 46.72±3.16°at ten which declines to 39.10±3.78°at eighteen. It fluctuates around 38-39±afterwards until another tendency downward appears after forty. In early adolescence the Sharp acetabular angle of the male is slightly larger than that of the female, while since late adolescence the Sharp angle of the female is obviously greater than that of the male.The center-edge angle of Wiberg is 21.62±6.23°at age four. It climbs steeply from 24.54±5.47°at age ten to 31.11±6.20°at age fourteen. Since adulthood it fluctuates around 30-32°until another rise to 34.94°at sixty. Generally no gender difference is significant while in some specific age groups this difference can be regarded as significant.Type III acetabula distributes in age group 4-9. The average difference between CCEA and MCEA is about 10-12°which does not vary with age.Conclusions1. Based on northeast Chinese population the reference ranges of acetabular index; Sharp acetabular angle and center-edge angle of Wiberg on pelvic radiographs are offered which back up clinical assessments and follow-ups.2. Acetabular index experiences a rapid declination in the first three months of life when early diagnosis and conservative treatments for developmental dysplasia of the hip can always provide fast recovery and diminished complications. The acetabulum remodels actively during age one to five which indicates a crucial time for surgical treatments.3. The Sharp acetabular is around 45°before the closure of Y-cartilage. After its closure it is less than 45°.4. The center-edge angle of Wiberg increases steeply during age and fluctuates around 30-32°in adulthood.5. Different types of acetabular roofs are observed. TypeⅢacetabulum is brought about by different developmental process between the anterior and posterior of the acetabulum rather than pelvic rotation, which is mainly observed on normal radiographs of age 4-9.6. In type III acetabula the classical center-edge angle above 25°and the modified center-edge angle above 15°can be regarded as normal in age 4-9.