The Significance Of The Tilt Rate Of Greater Trochanter During The Closed Locked Intramedullary Nailing Of The Femur

Objective: Femoral shaft fracture is the most common orthopedic clinical fractures. Closed interlocked intramedullary nailing is the main treatment. In the closed reduction and internal fixation if the rotational malalignment is excessive , it often causes traumatic arthritis with a series of clinical symptoms, severely affects the daily life of patients. Therefore, the judgment on the rotational malalignment during the closed locked intramedullary nailing of the femur is particularly important. Clinically,beause of the lack of objective data that judge the rotational malalignment of the femur, the operators depend mainly on visual observation in surgery and make judgments based on experience to minimize the occurance of rotational malalignment, resulting many patients in rotational deformity after the operation. The study on the different rotational states of the femur is less in the anatomy. Femoral greater trochanter and the lesser trochanter is the significance landmarks of proximal femoral anatomic. The lesser trochanter has earlier applied to judge the rotational alignment of the femur, beause of the rule shape and the corresponding changes that accompany by the femoral rotation. But the relevance between the corresponding change of the greater trochanter and the rotational state of femur is not measured and researched. Through this experiment, 20 healthy volunteers were taked the radiographs of proximal femurs in the following position : neutral position, 5°, 10°, 15°, 20°internal rotation, 5°, 10°, 15°, 20°external rotation . Then make a study of morphological changes of greater trochanter in different rotational angles, introduce this concept of"the tilt ratio of the greater trochanter". Every radiograph is recorded the rates of greater trochanter tilt , and summarized the correlation between the tilt rates of the greater trochanter and rotational angle. According to the laws that between the tilt rates of the greater trochanter and rotational angle to judge the rotational malalignment to achieve optimum rotational alignment during the closed locked intramedullary nailing of the femur.Methods: 20 healthy adult volunteers, 10 men, 10 women, mean age of 39 years(range20-58), mean height of 167.13cm, the average weight of 68.94Kg. Lying at the level of inspection stage, to determine the neutral position of femur, the subject was supine with knee flexed at 90°and the lower leg hanging vertically down over the edge of examining table. The distance between the bilateral femoral condyles was equal to that between the bilateral proximal femurs at the greater trochanter level, with the protection clothing to protect non-observed parts of the volunteers. Rotate the tube launcher of the X ray film machine digital radiography (DR) , so the proximal femurs of the volunteers at a relatively rotational state, such as when the tube launcher of the X-ray films is 5°internal rotation , the radiograph is 5°external rotation of femoral. Taking the radiograph in turns with men first , right leg first, each volunteer were taken radiograph of proximal femurs at the following position: neutral position, 5°, 10°, 15°, 20°internal rotation, 5°, 10°, 15°, 20°external rotation and the radiographs were obtained by tilting of the radiographic system whose window could show the angle simultaneously, sex, age, height, weight of the volunteers. With the SIENET Magicview 300 measurement software to measure the vertical distance between the greater trochanteric anterior tubercle and intertrochanteric line, subtrochanteric femoral diameter at the different rotational angles, recorded the average value of all the data that measured three times by the same observer and then calculate the tilt rate of the greater trochanter. The change of the tilt rate of the greater trochanter different sexes, different limbs at the same rotational angle was did statistical analysis. The change of the tilt rate of the greater trochanter at different rotationl angles was did statistical analysis. Statistical correlation analysis was did between the femur rotational angles and the tilt rate of the greater trochanter. Calculated the 95% reference range of the the tilt rate of the greater trochanter at different rotational angles. By the radiological landmark of the tilt rate of the greater trochanter to judge femoral position so as to prevent rotational deformity , twenty patients of the proximal femoral shaft 1 / 3 were did closed locked intramedullary nailing of the femur. The results were evaluated from the patient's operation time, blood loss, rotational deformity of the femur, hip and knee function, fracture healing time and other aspects.Results: From 20°internal rotatation to 20°external rotation at the same rotational angle of the same volunteers, the tilt rate of the greater trochanter was no statistical significance between the left leg and the right leg (P> 0.05), the same rotation angle was not statistical significance between the sexes (P> 0.05). The same volunteers, 5°rotation angle of adjacent two intervals the tilt rate of the greater trochanter changes was statistical significant (p <0.05), for every 5°external rotation when the tilt rate of the greater trochanter was gradually increasing . From 20°internal rotation to 20°external rotation , the average of the tilt rate of the greater trochanter increased from 0.18 to 0.47. The tilt rate of the greater trochanter when 20°internal rotation was 0.18±0.06, 15°internal rotation was 0.21±0.07, 10°internal rotation was 0.25±0.07, 5°internal rotation was 0.27±0.07, neutral position was 0.30±0.08, 5°external rotation was 0.34±0.09, 10°external rotation was 0.38±0.09, 15°external rotation was 0.42±0.12, 20°external rotation was 0.47±0.12. The 95% reference range of the tilt rate of the greater trochanter of different rotation angles: 20°internal rotation was [0.06,0.3], 15°internal rotation was [0.07,0.35], 10°internal rotation was [0.11,0.39], 5°internal rotation was [0.13,0.41], neutral position was [0.14,0.46], 5°external rotation was [0.16,0.52], 10°external rotation was [0.20,0.56] ,15°external rotation was [0.28,0.66], 20°external rotation was [0.23,0.71]. The relationship between the tilt rate of femoral greater trochanter and the external rotation angles was a positive linear correlation, we can use linear regression equation: the tilt rate of the greater trochanter = 0.31 +0.01 * rotation angle (internal rotation is negative, external rotation is positive. R = 0.993 P < 0.00001), rotational angle = -22.85 +73.18 * the tilt rate of the greater trochanter (internal rotation is negative, external rotation is positive, r = 0.719 P <0.00001) , indicating the relationship between the tilt rate of the greater trochanter and the rotational angles. When the tilt rate of the greater trochanter was as a technique to obtain the correct rotational alignment during closed interlocked intramedullary nailing, the operation average time was 1.2h, the average amount of bleeding was 150ml. Deformity of the femoral rotation was 4 cases less than 5°, accounting for 20% of the total; was 11 cases less than 10°, accounting for 55% of the total; was 3 cases less than 15°, accounting for 15% of the total; was 2 cases less than 20°,accounted for 10% of the total. The hip joint function of the Sanders score, 18 cases were excellent, 2 cases were good. The knee function of the Hohl score, 19 cases were excellent, 1 case were good. The healing time of fracture was 4.2 months on average.Conclusion: The tilt rate of greater trochanter in the same rotational angle between the sexes, left and right legs, was no significant difference. The change of the tilt rate of the greater trochanter when the rotation angle increasing 5°was a significant difference. The tilt rate of the greater trochanter increased when the femoral was external rotation, and decreased when internal rotation. From 20°internal rotation to 20°external rotation, the tilt rate of the greater trochanter increased as the angle of femoral external rotation increases. The 95% reference range of the tilt rate of the greater trochanter at different rotation angle is overlap, so it is not suitable to judge the rotational malalignment. Based on linear regression equation: rotational angle = -22.85 +73.18 * the tilt rate of the greater trochanter (internal rotation is negative, external rotation is positive, r = 0.719 P <0.00001) , calculate the tilt rate of the greater trochanter to judge the rotational malalignment so as to restore the rotation alignment of the femur shaft fracture, and achieved good effect. But to accurately restore the femoral rotational alignment should first take the anterior radiograph at neutral position of the contralateral proximal femur. Take the contralateral tilt rate of the greater trochanter to restore the femur rotational alignment.