X-ray of the hip joint in two projections

The most informative methods of instrumental diagnostics of articular and bone pathologies are visualization, and the most accessible of them is an x-ray of the hip joint.

A simple radiographic examination is a fundamental approach to diagnosing and deciding on the treatment of a hip joint. [1]

Indications for the procedure

Directing the patient to radiography, a traumatologist, orthopedic surgeon, surgeon or rheumatologist are able to assess the state of structures of this bone joint.

The most common indications for X-ray diagnostics of the hip joints relate to:

• traumatic damage to the hip area, in particular, femoral neck fractures;
• congenital dislocation or dysplasia of the hip joints;
• juvenile epiphysiolitis of the femoral head ;
• arthritis,  arthrosis of the hip joint , deforming arthrosis or coxarthrosis;
• coxitis (inflammation of the hip joint);
• necrosis of the femoral head;
• osteoarthritis, osteomyelitis and osteochondromatosis;
• articular cysts and other formations;
• affected bone marrow tuberculosis.

In principle, the patient's complaints about the felt  pain in the hip joint  are considered sufficient reason for the appointment of radiography - to establish their exact cause. If the above diseases and conditions are absent, the protocol (description) of the x-ray image will indicate that the x-ray is normal. This means that the images obtained of all articular elements have no anatomical abnormalities, for more details see -  Hip Joint

An X-ray of the hip joints in children is carried out according to strict indications - only after the child reaches nine months. The main pathology is congenital dislocation of the hip. In addition, x-rays can be prescribed for  pain in the hip joint in children of  different ages.

Preparation

For radiography, preparation consists in limiting food intake that causes flatulence, and cleansing the intestines (with an enema) - a few hours before visiting an X-ray room.

Immediately before the start of the procedure, the patient is put on protection - in the form of special shielding coatings that prevent the penetration of x-ray radiation into other parts of the body and internal organs.

Technique of the x-ray of the hip

The standardized radiography technique is little dependent on the method used - analog or digital. If in the first case the procedure lasts about 10 minutes, and the picture is taken on film, then in the second method the time is halved, and the image can be in two formats, including digital.

The maximum visual information is given by the x-ray of the hip joint in two projections: in the direct projection (or frontal) obtained by focusing the x-ray tube perpendicular to the body plane - front or rear, and axial (transverse or horizontal plane), fixing the elements of the joint from top to bottom - along the femur. Also, a picture can be taken with a lateral projection, that is, the patient should lie on his side, bending his leg in the knee and hip joints.

With conventional radiography, an anteroposterior and lateral radiography of the thigh is usually done. The anteroposterior x-ray of the thigh includes images of both sides of the thigh on the same film and protrudes in the direction of the middle of the line connecting the upper part of the symphysis pubis and the anteroposterior iliac spine; the distance between the x-ray tube and the film should be 1.2 meters. If radiographs of the anteroposterior thigh are made while lying on your back, one of the most common errors is image distortion when you turn the hips outside.  

Thus, either both kneecaps should be directed forward, or the lower limbs should be turned inward by 15-20 ° in order to adapt the femoral anti -version on radiographs of the anteroposterior femur.

If an X-ray of the hip joints is performed according to Launstein (Lauenstein), then the patient’s position looks like this: lying on his back, one leg in the knee bends (at an angle of 30, 45 or 90 °), while its foot rests on the shin of a straightened leg; the hip of the bent limb is pulled aside as far as possible so that the hip joint takes the position of external rotation (that is, the head of the femur rotates in the acetabulum).

It should be borne in mind that the x-ray of the pelvic and hip joints in young children does not show the exact shape of the joint structures, since their main tissue is cartilage, which the x-rays do not display. Therefore, the interpretation of the obtained x-ray — with the determination of the displacement of the femoral head in relation to the acetabulum of the pelvic bone — is carried out by applying a special mesh to the image, the main and auxiliary lines of which correspond to the anatomically normal arrangement of the joint structures. Using these lines, various parameters are measured, including the center of the acetabulum and the degree of inclination of its roof (acetabular angle), the angle of the femoral neck forward, etc.

And if there is a suspicion of a violation of the development of ossification nuclei (especially in premature babies), one and a half to two-month-old baby should do an ultrasound examination of the hip joint.

Contraindications to the procedure

X-rays are not carried out for any acute infections, fever, bleeding, as well as for inflammation of the synovial bursa of this joint and periarticular muscle tendons.

Radiography is strictly contraindicated for pregnant women and children of the first nine months of life (although in pediatrics the prohibition on x-ray is valid for up to 14 years).

Normal performance

Each x-ray provides important information necessary for the accurate diagnosis of diseases of the hip joint [2]. Typically, the anteroposterior profile provides information about the shape of the acetabulum, while other lateral images provide information about the proximal femur, including the femoral head. 

On radiographs of the anteroposterior femur, the following information can be obtained: 

• leg length, 
• neck angle 
• acetabulum coverage: the angle of inclination of the lateral central edge (CE) and the index of extrusion of the femoral head, 
• acetabulum depth, 
• acetabulum tilt, 
• acetabulum version, 
• sphericity of the head and 
• the width of the joint space.

On lateral radiographs of the hip joints, the shape and displacement of the joint of the femoral head and femur, as well as the angle displacement alpha, are evaluated.[3]

Given the Idelberg-Frank angle, the Wiberg angle, and the MZ-decentralization distance, statistical methods can be used to identify normal and pathological joints: in adults, values of the hip joint from 6 to 15 indicate the normal shape of the joint; values between 16 and 21 indicate a slight deformation, and values from 22 and above indicate a serious deformation, in children values of 15 and above are pathological. [4]

It is important to emphasize the need to use radiographs in combination with the results of a physical examination, since the results of imaging are not always associated with the presence of pain, and vice versa. [5]

X-ray signs of dislocation of the hip joint

On an X-ray, signs of dislocation or dysplasia of the hip joints are visualized as vertical and lateral displacements of the femoral head from the acetabulum of the pelvic bone (measured on the resulting image and compared with the anatomical norm). The surface of the femoral head often does not correspond to the acetabulum of the pelvic bone, for example, with a large head size and insufficient depth of the cavity. And the angle of inclination of the plane of entry into it exceeds the norm.

There is also a shift in the center of the acetabulum, a decrease or increase in the cervical-diaphyseal angle (defined between the vertical axes of the femoral neck and its body, the diaphysis).

Another important x-ray sign of this pathology is an excessive forward inclination of a narrow part of the femur (neck of the thigh), which radiologists call an exaggerated antetorsia.

More information in the article -  Congenital Hip Dislocation

X-ray signs of Perthes disease of the hip in children

The main x-ray signs of Perthes disease (osteochondrosis and aseptic necrosis of the femoral head) depend on its stage. If at the beginning of the disease a slight change in the shape of the femoral head and an uneven increase in the width of the joint space of the hip joint are visible, then at the second stage a distinct deformation of the contours of the femoral head is visualized and it becomes flatter.

At the third stage, the image of the joint shows shadows from areas of dead bone (sequesters) and the area of replacement of the destroyed bone with cartilaginous tissue. In this case, the expansion of the slit of the epiphyseal cartilaginous plate, the change in the shape of the acetabulum and the displacement of the tip of the femur are displayed.

Read more in detail -  Legg-Calve-Perthes disease

X-ray signs of coxarthrosis of the hip joint

The main indication for an X-ray examination of the pelvic organs in adults is the detection of osteoarthritis or the conditions that precede it. Arthrosis is the most common joint disease. [6] It is characterized by progressive degeneration of articular cartilage. [7]

Signs of arthrosis of the hip joint, which are referred to as coxarthrosis and deforming hip osteoarthritis in orthopedics, are also associated with specific stages of this destructive joint pathology.

Signs on the radiograph: narrowing of the joint space as a result of damage to the cartilage, subchondral sclerosis corresponding to the reparative reaction of the bone, the formation of osteophyte in the areas of the joint with low pressure, which corresponds to the reparative attempt to maintain stability of the joint and subchondral cysts, the etiology of which is discussed, and are found as in the femoral head and in the acetabulum.

All the necessary information on this issue is contained in the publication - X -  ray diagnosis of osteoarthritis of the hip joints (coxarthrosis)

X-ray signs of arthritis of the hip joint

As with most joint diseases, a phased development is common for inflammation of the hip joint - arthritis or coxitis.

At the initial stage, the main x-ray sign is the areas of damage to the hyaline cartilage on the surface of the femoral head and bone erosion in the form of roughness, indicating destruction of bone tissue.

Over time, the picture shows changes in the joint space (it can be seen that it narrows); the roundness of the femoral head is smoothed out; intraarticular foci of bone proliferation and proliferation of bone tissue on the surface of the joint can be detected.

Care after the procedure

Any care after the procedure is not needed.

Which is better, an ultrasound or an x-ray of the hip joints?

Experts read both visualization methods informative, but radiography does not allow you to see cartilage weave and tendon fibers and assess the condition of the articular cartilage and ligamentous apparatus of the joints. Therefore, in this regard, ultrasound has clear advantages. Patient reviews also indicate that they prefer ultrasound over x-rays. In addition, with ultrasound diagnostics, the body is not irradiated, and such an examination can be carried out monthly.

And how often can you do x-rays of your hip joints? When determining the optimal number of x-ray examinations in terms of safety, radiologists take into account the maximum permissible dose of ionizing radiation on bone tissue for one year (50 mSv), as well as the average single dose of radiation to one hip joint (not higher than 1.2 mSv). An X-ray is considered safe no more than four times a year (that is, once a quarter), and the number of examinations and the dose received should be recorded in the patient’s medical record.

Despite the fact that large doses of x-ray radiation are harmful, modern x-ray machines reduce the harm of x-rays of the hip joints to almost zero.

However, a certain risk remains: the main consequences after the procedure are the excessive exposure of x-rays to bone growth zones in children and adolescents - epiphyseal cartilage plates. Therefore, in foreign clinics, they try to avoid children of any age not only having x-rays, but also computed tomography accompanied by irradiation, replacing them with ultrasound whenever possible, and for older children and adolescents - MRI.

The method of choice for evaluating bone marrow, acetabulum, cartilage and periarticular soft tissues is magnetic resonance imaging (MRI).

Ultrasound (ultrasound) also plays a role in evaluating periarticular soft tissues and detecting effusion in the joint or thickening of the synovial membrane, which allows a dynamic assessment of the joint. It can also be used as a guide for diagnostic and / or therapeutic procedures.

MRI with intraarticular contrast (MR Arthrography) has better performance than conventional MRI for evaluating intraarticular pathology, especially articular bags and cartilage. It can also be used, for example, to administer a local anesthetic and to perform a “lidocaine test” of clinical diagnostic value.

To assess cartilage on MRI, in addition to morphological information, dGEMRIC T1 and T2 maps were used, which provide information on its composition of water and glycosaminoglycans (GAG). Computed tomography (CT), which uses ionizing radiation, has a greater spatial and contrast resolution than x-ray. [8]

In adults, irradiation during x-ray examination of the hip joints can lead to a decrease in the level of mineralization of adjacent bone tissues or induce mitosis of cells of the anatomical structures of the lower pelvis.