RU2441586C1 - Method for determination of pull-through angle of acetabular hood at its correction - Google Patents

Abstract

FIELD: medicine.

SUBSTANCE: invention is referred to the field of medicine, namely to orthopedics, and can be used for correction of acetabular hood in femor subluxation. Before the surgery on the pelvis X-ray image in posterior view using the Mose concentric circles or compasses the circle of head of femoral bone is drawn (conditional center - point D) and acetabulum circle (conditional center - point O). There is two possibilities of location for the centers of drawn circles: centers match and centers do not match. The rays are drawn on the X-ray image from conditional centers to Y-cartilage (point C) and from Y-cartilage to upper outer edge of acetabular hood (point A). The point B is determined - presumable position of upper outer edge of acetabluar hood in the end of correction. The resulting angles are measured: ∠ACO, ∠BCO, ∠BCD, ∠DCO and necessary value of pull-through angle of acetabular hood б is calculated in degrees: if point D matches point O б= ∠ACO -∠BCO, if point D is inside the ACO triangle made by rays between the center of circle of present acetabelum, Y-cartilage and upper outer edge of acetabular hood then б= ∠ACO -(∠BCD+∠DCO), if point D is outside the ACO triangle then б= ∠ACO -(∠BCD-∠DCO). EFFECT: method provides for individual approach to acetabular hood correction increasing the loaded surface of femoral head and provides for creation of congruent articular surface of acetabelum for femoral head.

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Description

The invention relates to medicine, namely to orthopedics, and can be used to correct the arch of the acetabulum with hip subluxation.

In the known methods of plastic surgery of the roof of the acetabulum with subluxation of the thigh in children in the external fixation apparatus (US Pat. RF No. 2033099, 2275173), a bone-cartilaginous flap is gradually corrected. Before the operation, the standard angles of the ACL of the acetabulum are measured by the radiograph, and their compliance indicators are calculated. In the postoperative period, when correcting the position of the vault of the acetabulum, they strive to achieve radiological indicators corresponding to the age norm.

However, in cases where the relationship between the pelvic and femoral components is broken in the joint, and the femoral head is deformed, the achievement of normal, from the point of view of anatomy, relationships in the hip joint due to the reduction of the acetabulum arch does not always ensure congruence of their surfaces. In addition, the used radiological parameters and indices of the hip joint characterize violations of the anatomical and spatial relationships of the pelvic and femoral components of the joint, but do not allow to determine the individual angle of correction of the acetabulum arch to increase the area of the loaded surface of the femoral head during subluxation.

A known method for determining the x-ray spatial relationships of the components of the hip joint (Sadofieva V.I. X-ray functional diagnostics of diseases of the musculoskeletal system in children. - L., Medicine, 1986. - 240 p. Fig. 62). The data of these criteria are taken into account at the stage of determining indications for surgical treatment on the pelvic component of the hip joint.

However, these indicators do not determine the angle by which it is necessary to tilt the bone-cartilaginous flap, with a gradual correction in the postoperative period.

The technical problem is to increase the area of the loaded surface of the femoral head and to restore the congruency of the articular surface of the acetabulum for the contour of the femoral head by determining the individual angle of descent of the arch of the acetabulum is solved as follows.

In the method for determining the angle of descent of the vault of the acetabulum according to the x-ray according to the invention, prior to surgery, the condition of the femoral head D and the acetabulum O is determined on the radiograph of the pelvis in the rear projection, taking into account the contour of the lower part, the arch and the bottom of the acetabulum, DC and OS segments are constructed, connecting these centers with the Y-cartilage — point C, draw a segment CA from the Y-cartilage to the upper-outer edge of the acetabular arch (point A). On a circle with a radius of OS, which is the contour of the assumed normal surface of the acetabulum vault for a given femoral head, find point B — the position of the upper outer edge of the acetabulum vault, which must be achieved during correction, for which from point C to the intersection with this circle draw a segment CB equal to segment C A, the conditional center of the femoral head — point D is connected to point B — segment DB and measure the obtained angles ∠ACO, ∠BCO, ∠BCD, ∠DCO and, depending on the position of the conditional centers of the femoral head and circumference ty of the acetabulum on the x-ray, determine the required angle of reduction of the arch of the acetabulum according to the formulas:

1. conditional geometric centers of the femoral head (point D) and the acetabulum (point O) coincide

where α is the required angle of reduction of the vault of the acetabulum in degrees;

2. conditional geometric centers of the femoral head and acetabulum do not match:

- point D is inside the ASO triangle formed by the segments between the center of the circumference of the existing acetabulum, the Y-cartilage and the upper-outer edge of the acetabulum

- point D is outside the triangle ASO

The parameters used to build on the x-ray, characterize the spatial position of the femoral head in the cavity, take into account the configuration of the femoral head and acetabulum, allow you to calculate the angle by which you must tilt the bone-cartilaginous flap to increase the area of the loaded surface of the femoral head, and create the maximum possible congruent articular surface of the cavity for the contour of the head (i.e., to ensure the coincidence of the centers of the circumferences of the femoral head and acetabulum) . Theoretical calculations and X-ray diagrams carried out by the authors prove the correctness of the choice of the point of the proposed position of the upper outer edge of the acetabular arch at the end of correction, which was confirmed by studying 46 radiographs of children aged 5-11 years with hip subluxation. The final results of surgical treatment also confirm the correct choice of parameters that allow to determine the value of the individual angle of correction of the arch of the acetabulum.

The proposed method is used as follows. Before an operation, a hip circumference is made using a radiograph of the pelvis in the rear projection using concentric circles Mose or a compass (point D is the center of the circumference and the conditional center of the femoral head). Next, build a circle taking into account the contour of the lower part, arch and bottom of the acetabulum and mark its center (the center of the circumference of the acetabulum - point O is the conditional geometric center of the acetabulum) (Figure 1).

There are two possible locations of the centers built on the x-ray of the circles: 1) point O coincides with point D (Fig. 1; 2) points O and D do not coincide (Fig. 2A, B).

From the conditional centers to the Y-cartilage (point C), segments of the OS and DC are built, as well as from the Y-cartilage (point C) to the upper-outer edge of the acetabular arch (point A), the segment CA. The OS segment is the radius of the circumference of the acetabulum, at which point B is the estimated position of the upper-outer edge of the acetabular arch at the end of the correction (CA = CB), and then ОВ≈ОС is the radius of the contour of the estimated surface of the acetabulum for this femoral head (Fig. .one). Consider the obtained triangles and angles (the angles are measured on a radiograph by a protractor) and calculate the required value of the angle of descent of the vault of the acetabulum, taking into account the location of the conditional center of the acetabulum (point O) with respect to the conditional center of the femoral head (point D). If the x-ray of the point O coincides with the point D (Figure 1), the required angle of lowering of the arch of the acetabulum α in degrees is calculated by the formula (1)

If the conditional centers: point O and point D on the roentgenogram do not coincide (Fig.2A, B), then consider the location of point D relative to the triangle ASO. Point D is inside the ASO triangle, then the desired angle of descent of the acetabulum is calculated by formula 2, if outside the triangle ASO - by formula 3

Clinical example 1. Patient S., 7 years old, and. 90648.

Diagnosis: Subluxation of the left thigh. The outcome of a closed reduction in congenital dislocation of the left thigh. In FIG. 3 presents a radiograph of patient C. at the stage of preoperative planning. The acetabular angle before surgery was 48 °.

On the roentgenogram, geometric constructions are made and angles are measured. Since the conditional centers coincide, the required angle α, by which it is necessary to lower the bone-cartilaginous flap of the vault of the acetabulum, is calculated by the formula 1

α = ∠ACO-∠BCO = 87 ° -58 ° = 29 °.

Ha Figure 4 presents the x-ray of the patient C. after surgery and the gradual correction of the bone-cartilaginous flap at the calculated angle. The contours of the articular surfaces of the hip joint have a single geometric center, the surfaces are congruent, an acetabular angle of 13 °.

Clinical example 2. Patient T., 6 years old, and. 88146.

Diagnosis: Subluxation of the right thigh. The outcome of a closed reduction of a congenital dislocation of the right femur complicated by aseptic necrosis of the femoral head. Figure 5 presents the x-ray of the patient T. at the stage of preoperative planning with geometric constructions. Acetabular angle before surgery 35 °.

On the roentgenogram, the angles obtained during the construction are measured. Since the conditional geometric center of the femoral head - point D is located inside the ASO triangle, the required angle of lowering of the acetabulum is calculated by the formula 2

α = ∠ACO- (∠BCD + ∠DCO) = 64 ° - (45 ° + 4 °) = 15 °.

Ha Figure 6 presents the x-ray of the patient T. after correction of the acetabulum. The contours of the joint surfaces of the hip joint have a single geometric center, the surfaces are congruent, the acetabular angle is 19 °.

Clinical example 3. Patient K., 6 years old, and. 94596.

Diagnosis: Subluxation of the left thigh. The outcome of open reduction of a congenital dislocation of the left femur with a derotational-varicating, shortening osteotomy of the left femur. Figure 7 presents the x-ray of the patient K. at the stage of preoperative planning with geometric constructions. Acetabular angle before surgery 35 °.

The conditional center of the femoral head - point D relative to the ASO triangle is outside the ASO triangle; therefore, the angle by which the bone-cartilaginous flap of the arch of the cavity must be reduced is determined by formula 3. We measure the angles and calculate the angle α

α = ∠АСО- (∠BCD-∠DCO) = 62 ° - (51 ° -9 °) = 20 °.

On Fig presents a x-ray of the patient K. after correction of the arch of the acetabulum. The contours of the joint surfaces of the hip joint have a single geometric center, the surfaces are congruent, the acetabular angle is 15 °.

Thus, the proposed method allows individually at the stage of preoperative planning to determine the angle of descent of the fornix of the acetabulum, which as a result will increase the area of the loaded surface of the femoral head, as well as with the gradual lowering of the bone-cartilaginous flap in the postoperative period to create a congruent articular surface of the acetabulum for thigh heads.

Claims (1)

A method for determining the angle of descent of the vault of the acetabulum during its correction, including radiography, characterized in that prior to surgery on the x-ray of the pelvis in the rear projection, conditional geometric centers of the femoral head are determined - point D and acetabulum - point O, taking into account the contour of the lower part, arch and the bottom of the acetabulum, build segments of DC and OS, connecting these centers with the Y-cartilage - point C, draw from the Y-cartilage to the upper-outer edge of the arch of the acetabulum - point A segment CA, build a circle with a radius of OS , which is a contour of the assumed normal surface of the acetabulum vault for a given femoral head, at which point B is located - the position of the upper-outer edge of the acetabulum vault, which must be achieved during correction, for which a segment CB is drawn from point C to the intersection with this circle equal to the segment CA, then the conditional center of the femoral head - point D is connected to point B - segment DB and the obtained angles ∠ACO, ∠BCO, ∠BCD, ∠DCO are measured and, depending on the position of the conditional centers of the femoral head (point D) and about the acetabulum circles (point O) on the roentgenogram, determine the required angle of descent of the acetabulum arch α, in degrees, using the formulas: if point D coincides with point O α = ∠ACO-∠BCO, if point D is inside the ASO triangle formed by the segments between the center of the circumference of the existing acetabulum, the Y-cartilage and the upper-outer edge of the acetabulum, then
α = ∠ACO- (∠BCD + ∠DCO),
if point D is outside the triangle ASO, then
α = ∠ACO- (∠BCD-∠DCO).

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