Pelvic Osteotomy for Acetabular Dysplasia Workup

Updated: Sep 22, 2017
  • Author: Dinesh Thawrani, MBBS, D'Ortho, DNB(Orth), MNAMS; Chief Editor: Jeffrey D Thomson, MD  more...
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Workup

Plain Radiography

Assessment of the acetabular anatomy via an appropriate radiographic view is the most essential preoperative step in the planning of any pelvic osteotomy. [23]  Radiographic evaluation starts with a plain anteroposterior (AP) radiograph of the pelvis with both hips in weightbearing position (standing view), followed by frog-leg lateral and abduction–internal rotation (AIR) views of both hips and a false-profile view of the affected hip.

The AP standing radiograph is analyzed with respect to the intactness of Shenton’s line, the quality and the location of the acetabular sourcil, the acetabular index of the weightbearing zone, the lateral center-edge angle of Wiberg, joint-space narrowing, and the shape of the corresponding articular surfaces.

Shenton’s line is a continuous arc extending from the proximal medial femoral metaphysis onto the superior border of the obturator foramen. Any disruption in the continuity of this line indicates that the femoral head is proximally and laterally subluxated or dislocated.

The sourcil (French for “eyebrow”) is a dense layer of subchondral bone that normally appears as a smooth curve of uniform thickness and is a sensitive indicator of the location of loading of the hip joint. Any side-to-side asymmetry in the thickness of the sourcil indicates abnormal focal loading of the hip due to underlying acetabular dysplasia or joint malalignment.

The acetabular index of the weightbearing zone [24]  and the acetabular angle of Sharp [25]  help quantitate the steepness of the acetabular wall (ie, the severity of the acetabular dysplasia).

The lateral center-edge angle of Wiberg [24]  indicates the amount of femoral head covered by the acetabular roof.

Joint-space narrowing is a rough guide to the loss of cartilage thickness on either of the articulating surfaces.

The AIR view neutralizes the femoral anteversion and simulates the coverage possible with either rotational pelvic osteotomy or proximal femoral varus osteotomy; it is essential for demonstrating a concentric reduction before the performance of a reorientation procedure.

The frog-leg lateral view gives a true lateral view of the proximal femur and helps assess any abnormal abutment of acetabular rim to the proximal femur in the flexed and externally rotated position of the limb. Quantitative assessment of head neck offset in this view is helpful for understanding the presence of any abnormal femoroacetabular impingement.

The false-profile view of Lequesne and de Sèze [26]  is a true lateral view of the acetabulum made with the pelvis rotated 25° towards the x-ray beam. The anterior center edge angle measured on this false-profile view indicates the anterior extent of the acetabulum covering the femoral head. [26, 27]

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Arthrography

Arthrography is a dynamic hip study that is performed by injecting contrast medium into the hip joint and then examining the hip directly under the image intensifier. The authors prefer a medial subadductor approach to injection of the dye. General anesthesia is usually required.

Arthrography is sometimes performed in the operating room immediately before the operation to provide a better understanding of the cartilaginous profile and a more accurate assessment of hip joint stability. The dynamic component of the test is sometimes useful for mimicking the coverage anticipated by the pelvic osteotomy.

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Computed Tomography

Computed tomography (CT) with three-dimensional (3D) reconstruction has contributed to a more precise understanding of the pathoanatomy of acetabular dysplasia. It gives the surgeon a 3D representation depicting the shape, orientation, and extent of the margins of the acetabulum, as well as the fit of the femoral head in the acetabulum. In this way, it can help the surgeon select the type of pelvic osteotomy that best matches the identified pelvic deficiencies. [28]

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Magnetic Resonance Imaging

Magnetic resonance imaging (MRI) and magnetic resonance arthrography are also indicated when associated labral pathology or cartilage damage is suspected. Magnetic resonance arthrography is the most sensitive indicator of the location and extent of a labral tear, [22]  which can be clinically evidenced by anterior groin pain or a positive anterior impingement test result. [21]

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Ultrasonographic Screening of Newborns

All newborns should have a clinical examination for hip instability. Beyond that, however, newborn screening is controversial, with a spectrum of diagnostic tests available.

In North America, it is more common to rely on the initial history and physical examination and to refer for orthopedic evaluation and ultrasonography only in the presence of a significant risk factor (eg, a first-born female with a breech presentation) or a significant physical examination abnormality (eg, a positive Barlow, Ortolani, or Galeazzi test result). In 2000, the American Academy of Pediatrics issued a practice guideline that generally followed these recommendations. [29, 30]

Others, especially in Europe, advocate ultrasonographic examination of every newborn to decrease the incidence of late dysplasia. The disadvantages of this approach include the substantial cost and the large number of infants with ultrasonographic abnormalities that then require treatment.

In the literature, the incidence of ultrasonographic abnormalities ranges from a low of 0.4% [31]  to a high of 50%. [32]  This wide range calls into question the utility of ultrasound screening of all newborns, especially when these radiographic abnormalities are associated with a normal physical examination, in which case nearly all of them resolve with time. [33]

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