1.Shenton line
Also known as the pubic neck line, the lower arc, the upper edge of the closed hole and the femoral neck inner lower edge of the line, normal for smooth, continuous arc shadow, discontinuous suggests hip dislocation or femoral neck fracture displacement.
2.Iliac neck line (calve upper arc)
It is a smooth arc between the outer edge of the iliac bone and the outer edge of the femoral neck; if it is not continuous, it suggests hip dislocation or femoral neck misalignment fracture.
3.perkin’s square
In pelvic orthopantomograph, a horizontal line AB is drawn through the Y-shaped cartilage center of the acetabulum bilaterally, and then vertical lines CD and EF are drawn through the outer upper edge of the acetabulum. The center of the normal femoral epiphysis is located in the inner lower region, and the femoral epiphysis is located in the outer upper region when the hip is dislocated.
4.Acetabular angle and iliac angle
Acetabular angle (a) also called acetabular index: orthopantomograph of the pelvis, the angle formed by the line connecting the center of the Y-shaped cartilage on both sides and the line connecting the upper and lower edges of the acetabulum. The angle is 30° in newborns; should not exceed 25° after 1 year of age; 20° at 2 years of age; 10° in adults with congenital hip dislocation, the acetabulum becomes shallow and the angle increases.
Iliopsoas angle (b): the angle between the line connecting the anterior inferior iliac spine and the external superior border of the acetabulum and the horizontal line of the Y-shaped cartilage. The angle is 55° in newborns, and the normal range is 43-67°. A decrease in the angle is considered abnormal.
5.Neonatal hip joint gap
In the neonatal pelvic orthopantomograph, the Y-shaped cartilage of the acetabulum on both sides is called the Hilgenreiner line, or H-line for short. The distance between the upper femur and the H line is the upper gap, and the distance between the upper femoral beak and the outer edge of the sciatic branch is the medial gap, with a normal average value of 9.5mm for the upper gap and 4.3mm for the medial gap. If the upper gap is less than 7.5mm and the medial gap is greater than 6.1mm, hip dislocation can be diagnosed.
6.Epiphyseal index and epiphyseal quotient
Epiphyseal index: epiphyseal height ÷ epiphyseal width × 100
Epiphyseal quotient: the epiphyseal index of the affected side divided by the epiphyseal index of the healthy side.
Epiphyseal index and epiphyseal quotient: both indices indicate the degree of flattening of the femoral epiphysis and are used to evaluate the treatment effect of developmental hip dislocation. The epiphyseal quotient is mainly used to compare with the key side to determine the degree of lesion and treatment effect.
7.Epiphyseal angle
The angle between the epiphysis of the upper femur and the Y-shaped cartilage line on both sides. The normal value is 20°-35°, and the angle increases with hip inversion.
8.Sharp (sharp) angle
The angle between the line connecting the inferior edge of the teardrop and the line connecting the inferior edge of the teardrop to the superior edge of the acetabulum on both sides. Normal is 33°-38°, greater than 40° can be diagnosed as acetabular dysplasia.
9.Center edge angle (CE angle)
The angle between the center of the femoral head and the line connecting the outer upper edge of the acetabulum and the vertical line of the center of the femoral head. The normal angle is 22° at age 2, 28° at age 4, 30° at age 6, and 35° at age 15. The angle becomes smaller when the acetabulum is dysplastic, the hip is dislocated, or the femoral head is displaced.
10.Depth of acetabulum
The maximum distance between the upper border of the pubic symphysis and the outer upper border of the acetabulum to the acetabular floor. In normal adults, it is 13 (7-18) mm for men and 12 (9-18) mm for women, and is often used clinically in conjunction with the CE angle to indicate the degree of acetabular development.
11.Acetabular coverage
The transverse diameter A of the femoral head covered by the acetabulum divided by the transverse diameter B of the femoral head, normally greater than 0.75, can be used to determine the displacement of the femoral head.
12.Skinner’s line
In adult hip orthopantomograph, the vertical line CD of the femoral longitudinal axis AB is made from the top of the greater trochanter. normally, this line should pass through the round ligament fossa or below it, and the distance from the round ligament fossa to the intersection of the above two lines is 4-5 cm. if the Skinner’s line exceeds the round ligament fossa, it indicates a misaligned fracture of the femoral neck or greater trochanter.
13.Kline line
A line drawn along the upper edge of the femoral neck and extended toward the femoral head is the Kline line. Normally this line should cut part of the femoral epiphysis. When the femoral epiphysis slips inward and downward, the epiphysis moves to the inner side of this line.
14.Kohler (KOhler) line
It is also called the iliac situs line. The line between the tangent line of the inner edge of the iliac bone and the inner edge of the situs is the Kohler line. When the acetabulum is caught in the disease, the acetabulum protrudes to the medial side of this line.
15.Powell’s (Power) angle
On the pelvic orthopantomograph, make a horizontal line through the anterior superior iliac spine on both sides, and then draw the extension line of the femoral neck fracture line, and the angle made by the intersection of the two lines is called the Powell angle. If the angle is less than 30°, it is an abductor fracture and the fracture is easy to heal; if it is as large as 30°-90°, it is an adductor fracture and needs to be corrected surgically.
16.Linton angle
On the hip orthopantomograph, draw the vertical line with the longitudinal axis of the femoral stem, then draw the extension line of the femoral neck fracture line, and the angle formed by the intersection of the two is called the Linton angle. If the angle is less than 30°, it is an abductor fracture and the fracture will heal easily; if it is 30°-90°, it is an adductor fracture and requires surgery.