Adolescent and Young Adult Hip Dysplasia

David D. Spence, Derek M. Kelly, Marc J. Mihalko and James L. Guyton

Disclosures

Curr Orthop Pract. 2013;24(6):567-575. 

In This Article

Diagnosis

Presentation

Initially, hip pain may be mild enough to go unnoticed for years until the acetabular rim and labrum are damaged.[16,17] The most common presenting symptom in adolescent or adult hip dysplasia is pain that begins insidiously. Mostly, the pain occurs in the groin or anterolateral aspect of the hip, although it also has been described in the anterior aspect of the thigh or posteriorly. Nunley et al.,[18] in a study of clinical presentation of acetabular dysplasia in skeletally mature patients, found that pain was moderate to severe in 77% of patients and related to activity in 87% (walking, running, and standing). Pain was most common with forced hip flexion, adduction, and internal rotation. Most patients described an intermittent sharp or dull aching pain, with night symptoms being reported in more than half. Abductor fatigue also is a common finding. Rest and the use of antiinflammatory medications usually provided relief.

Physical Examination

Diagnosing end-stage hip disease is relatively straightforward, but diagnosing early hip dysplasia is more difficult. Range of motion usually is normal in early hip dysplasia, and often there are no areas of tenderness. Careful examination may reveal a positive Trendelenburg sign, or in some hips, a clunk can be felt from the iliopsoas tendon snapping over a protruding femoral head with external rotation of the hip in extension.[5] Nunley et al.[18] noted snapping or popping in the hip in 67% of patients, locking in 23%, subluxation in 22%, and no mechanical symptoms in 22%. Most patients had a limp to some degree (85%). Provocative tests that can be used to examine the hip include the impingement test, an apprehension test, or a bicycle test. Acetabular rim lesions often produce a positive impingement test, which will cause sharp groin pain if there is a labral tear or chondrolabral degeneration (Figure 2). A positive apprehension test produces instability in a patient with insufficient acetabular coverage of the femoral head (Figure 3). A bicycle test can help determine abductor muscle insufficiency and is done by placing the patient laterally on the examination table with the affected hip up and performing pedaling motions. In a positive test, pain occurs along the posterior border of the gluteus medius muscle, and crepitus may be noted over the trochanteric bursa.[5]

Figure 2.

Impingement test. The hip is internally rotated and passively flexed to 901 and adducted.

Figure 3.

Apprehension test will cause sharp groin pain if there is a tear or degeneration of the labrum. With the patient supine, the hip is extended, abducted, and externally rotated.

Imaging

Diagnosing a patient with a structural hip abnormality (especially if it is mild) remains a challenge, and radiographic examination is mandatory in the diagnosis, classification of the disease, and treatment decision-making. To evaluate a skeletally mature patient with symptoms of hip pain, radiographs to evaluate the acetabulum, proximal femur, and their relationship should be obtained and systematically reviewed. A standing pelvic anteroposterior view and false-profile view provide information about the acetabular morphology, and a 451 or 901 Dunn view, a crosstable view, and a frog-leg lateral view can be used to examine the proximal femur.[19] Information that can be gleaned from a plain pelvic anteroposterior radiographic view includes the acetabular index (acetabular depth-to-width measurement, see Figure 1) and the acetabular inclination, which is categorized as normal, increased, or decreased based on the Tönnis angle (see Figure 1). A Tönnis angle of more than 101 or less than 01 indicates increased or decreased inclination of the acetabulum, respectively. A lateral center-edge angle (Wiberg angle; see Figure 1) also can be measured on anteroposterior radiographs and is used to assess coverage of the femoral head by the acetabulum superolaterally. The anterior center-edge angle (angle of Lequesne; see Figure 1) is best determined on a false-profile view and estimates the anterior coverage of the femoral head. Acetabular retroversion or anteversion can be determined on anteroposterior radiograph using the cross-over sign (see Figure 1); the acetabulum is considered to be anteverted if the line of the anterior rim of the acetabulum does not cross the line of the posterior aspect of rim before reaching the sourcil. If the line crosses the rim, the acetabulum is considered to be retroverted. It is important that the anteroposterior pelvic radiograph is properly aligned (symmetrical obturator foramen, with coccyx pointing to the symphysis 0–2 cm) or the degree of retroversion can be overestimated or underestimated. If on an anteroposterior view of the pelvis, the ischial spine is prominent, this too is associated with retroversion.[20] In true acetabular retroversion, a deficient posterior wall is present, which is not so in isolated anterior overcoverage of the acetabulum.[19]

Additional information can be obtained by assessing the position of the hip center based on the position of the medial femoral head relative to the ilioischial line. If the femoral head is more than 10mm from the ilioischial line, it is considered to be lateralized. Another important observation is Shenton's line (Figure 4); if the arc is not smooth, hip dysplasia and early subluxation are likely.

Figure 4.

Shenton line.

The Dunn view, frog-leg lateral and cross-table lateral views along with the anteroposterior radiograph are used to determine whether or not the femoral head is spherical. The degree of osteoarthritis in each hip can be determined using the Tönnis classification system, which grades hips from 0 (no sign) to 3 (large femoral head, acetabular cysts, necrosis, severe narrowing, or deformity).

Use of CT and MRI can add additional information about the hip. CT is helpful in determining version of the hip. Magnetic resonance arthrography (MRA) with gadoliniumdiethylenetriamine pentaacetic acid (DTPA) contrast has been shown to improve intraarticular imaging, aiding in the detection of cysts or ganglions, labral tears, or degenerative changes.[5,21] This technique images the fixed charges associated with glycosaminoglycan in articular cartilage to determine if diseased cartilage is present; glycosaminoglycan will be lacking in degraded cartilage.[22] The delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) index is used to determine the presence of osteoarthritis and has been suggested to have a role in identifying patients who are most likely to have a poor outcome after osteotomy.[23]

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