Type:
Educational Exhibit
Keywords:
Performed at one institution, Not applicable, Education and training, Dysplasias, Technical aspects, Education, Diagnostic procedure, Ultrasound, Paediatric, Musculoskeletal joint, Anatomy
Authors:
J. K. Soares1, M. S. Takahashi1, F. Gual2, T. D. GASPARETTO1, G. MOTTA3, M. T. Moreira3, L. B. Q. Rodrigues 3; 1Sao Paulo/BR, 2São José do Rio Preto/BR, 3SÃO PAULO/BR
DOI:
10.26044/ecr2020/C-08463
Findings and procedure details
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Ultrasonography has been used since the 1980s for the evaluation of DDH:
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See below, the main ultrasound methods used nowadays. These methods are not exclusive and can be used together for more complete hip evaluation.
Graf Method
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The static method described by Reinhard Graf in 1990.
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It uses only one coronal plane.
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Classification based on alpha and beta angles (Fig. 9 - Fig. 10).
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Patient and transducer position: Fig. 2.
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Standard plane: contains the lower limb of the bony ilium, the labrum and the straight iliac wing contour (Fig. 3 - Fig. 4).
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Based on three lines:
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the baseline: goes from the origin of the rectus femoris tendon to the caudal edge of the iliac surface (Fig. 5).
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the bony roof line: is drawn from the lower edge of the iliac bone to the lateral edge of the acetabulum bone ceiling (Fig. 6).
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the cartilage roof line: goes from the upper extremity of the acetabular edge to the central portion of the labrum (Fig. 7).
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α angle: is formed between the bony roof line and the baseline.
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β angle: is formed between the cartilage roof line and the baseline.
These errors can be related to:
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Technique: when the transducer is not aligned with the middle plane of the acetabulum, the iliac tends to become curved, making it impossible to see the main anatomical repairs (Fig. 2).
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Bone Anatomy: the ligament of the femur head that fits into the femoral apex of the femur head can sometimes be confused with the medial and lower extremity of the iliac bone (Fig. 6). When this happens the bone roof line is dislocated and the alpha angle can be underestimated.
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Cartilage roof anatomy:
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In dysplastic hips, the upper extremity of the acetabular edge (a reference to draw the cartilage roof line) is the point in which the concavity becomes convexity. If it is not taken into consideration, the beta angle could be underestimated (Fig. 8);
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Confusion between the labrum and the synovial fold. In these cases, there may be an underestimation of the beta angle (Fig. 8).
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Classification:
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Most hips classified as IIa (50º ≤ alpha ≤ 59º) are expected to become a type I hip (alpha ≥ 60º) by 3 months of age. Type IIa is subdivided to try to separate patients with properly developed joints for the age group (IIa +) from those with delayed maturation (IIa -). Angle progression is considered linear with time. This subdivision takes into account not only the alpha angle but also the age of the patient (Fig. 11).
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In cases where the hip joint is luxated and the femoral head is dislocated, the loss of congruence of the anatomical repairs may make it impossible to correctly measure the angles for classification. In such cases, it is not necessary to measure alpha and beta angles (as this may lead to hip misclassification). So, it can automatically be considered a type III or IV hip (Fig. 12).
Degree of acetabular coverage
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The static method described by Morin in 1985 and modified by Terjesen in 1989 and by Harcke et al. in 2017.
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The degree of femoral head coverage by the acetabulum is evaluated and the result is given as a percentage.
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Patient and transducer position: Fig. 13.
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Measure: Relationship between acetabulum depth (d) and femoral head level (D).
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Coverage Degree = d / D * 100 (Fig. 14).
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There are a few variations on how to take measurements and in general:
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Normal> 55%
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Undetermined 45-55%
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Altered <45%
Pubo-femoral distance
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The static method described by Couture et al. in 2011 and modified by Tréguier et al. in 2013.
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Patient and transducer position: Fig. 15 .
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Measure: the distance between the medial end of the femoral head and the ossified portion of the pubic bone (Fig. 16).
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Harcke Method
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The static and dynamic method described by Harcke et al. in 1990.
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The joint is evaluated in the neutral and flexed positions, in the coronal and transverse planes, at rest and during the stress maneuver.
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A hip exam should contain 16 images.
Coronal View
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Patient and transducer position: Fig. 17 - Fig. 18.
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Dynamic examination: gentle push in the posterior direction is made against the knee (instability = portion of the femoral head over the posterior lip of the triradiate cartilage).
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Average acetabular and the posterior lip should be examined.
Transverse View
Three-Dimensional Ultrasound (3DUS)
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This method was applied to DDH by Graf and Lercher for the first time in 1996.
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Patient and transducer position: Fig. 21.
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3DUS has some advantages over the 2-Dimensional Ultrasound (2DUS), particularly by novice users:
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requires less time of exam;
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shows greater inter-rater reliability for detecting DDH;
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is less dependent on operator experience;
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is easier to master;
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produces better image quality (Fig. 22).
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3D probe has an internal motor that quickly sweeps through a range of angles inside while the person holding the probe keeps it still.
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This takes a few seconds to generate a stack of ultrasound images which can then be used to generate a 3D model of the hip.
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Acetabular contact angle (Fig. 23).