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[Radiological assessments of proximal femoral geometry and its clinical significance in hip arthroplasty].

OBJECTIVE
To explore the reliability of the relationship between the tip of greater trochanter and the center of femoral head in restoring leg length discrepancy during hip arthroplasty.


METHODS
From June 2013 to October 2013, 370 standard anterior-posterior pelvic radiographs were performed. There were 160 males and 210 females with a mean age of 47.6 years. Landmarks were selected by Picture Archiving and Communication Systems (PACS) as follows: the center of femoral head of concentric circles, anatomic axis of proximal femur, the lines perpendicular to anatomic axis of proximal femur through the tip of greater trochanter and the center of femoral head. The distance between two intersected points, i.e. vertical distance between the tip of greater trochanter and the center of femoral head, aka greater trochanter height (GTH), was measured by two orthopedic surgeons respectively. If the tip of greater trochanter was above the center of femoral head, the distance was defined as positive. And the distance was negative if the tip of greater trochanter fell below the center of femoral head. The distance of male and female and that of right and left femurs were compared.


RESULTS
Only 6 tips of greater trochanter were below the center of femoral head, 9 at the same level and 725 above the center of femoral head. And 96.89% of tips of the greater trochanter were at 0-15 mm above the center of femoral head. The difference between male and female (P = 0.032) and the difference between right and left sides were statistically significant (P < 0.001).


CONCLUSION
The center of femoral head is not at the same level as the tip of greater trochanter. And the distances of right and left tips of greater trochanter to the ipsilateral center of femoral head are not always at the same level. So it should be cautious to employ the relationship between the tip of greater trochanter and the center of femoral head in restoring leg length discrepancy during hip arthroplasty.