The concept of greater trochanter tilting index and its radiologic measurement in clinic

Abstract

ObjectiveTo propose the concept of greater trochanter tilting index (GTTI) and to explore its association with femoral rotation.MethodsTwenty healthy adult volunteers were enrolled in the present study. They were 10 men and 10 women, aged from 20 to 58 years (average, 39.2 years). Their average height was 167. 1 cm (from 158 to 183 cm) . Posteroanterior radiographs of both of their proximal femurs were taken with their legs at the following positions: neutral position, internal rotations at 5°, 10°, 15° and 20°, external rotations at 5°, 10°, 15° and 20°. The GTTIs were measured and calculated at different rotation angles. The GTTI =the shortest distance between the intertrochanteric crest and the medial wall of greater trochanter / diameter of the femoral shaft. Statistical analyses were performed to explore GTTIs.ResultsThere were no significant differences between genders or between the left and right sides in GTTI at the same rotation angle ( P ＞ 0. 05). The average GTTIs at internal rotations at 20°, 15°, 10°, 5°, neutral position, external rotations at 5°, 10°, 15° and 20° were respectively 0. 18 ±0. 06, 0. 21 ±0. 07, 0. 25 ±0.07, 0.27±0.07, 0.30±0.08, 0.34±0.09, 0.38±0.09, 0.42±0.12, 0.47±0.12, significantly increasing with the increased external ration ( F =19. 737, P =0. 000) . The GTTIs were significantly different when their difference in rotation was greater than 15° ( P ＜ O. 05). There was a positive linear correlation between the GTTIs and external rotation angles.ConclusionSince the GTTIs increase with increased external rotation of the proximal femur and decrease with decreased internal rotation, they can be used to prevent malalignment during closed reduction. Key words: Femur; Rotation; X-rays; Tilting index