Clinical Evaluation of the Hip With Focus on Assessment of Hip Instability

Abstract

Background:

Hip instability is a challenging clinical diagnosis, which often overlaps with the presentation of hip impingement and/or hip dysplasia. Many factors contribute to hip instability, including acetabular undercoverage, femoroacetabular-impingement-induced instability, and soft tissue laxity. It can cause significant pain and disability, either as a primary pathology or as a complication of surgery and if untreated can ultimately lead to early osteoarthritis.

Indications:

Hip dysplasia is often diagnosed with an anterior-posterior pelvic radiograph. The literature has supported a normal lateral center edge angle (LCEA) as ≥25°, borderline dysplasia an LCEA of 18° to 25°, and an LCEA <18° as true dysplasia, though some authors will diagnose borderline dysplasia as an LCEA of 20° to 25° and true dysplasia as an LCEA <20°. In addition, there are many radiographic measurements that have been described to aid in the diagnosis of hip instability beyond LCEA, including the acetabular inclination (or Tönnis angle), the femoro-epiphyseal acetabular roof (FEAR) index, and the cliff sign.

Technique Description:

Hip instability can be present even in the absence of radiographic findings, and many with insufficient coverage of the femoral head do not meet the radiographic definition of dysplasia. For this reason, it is important to have an understanding of the clinical assessment that may aid in the diagnosis of hip instability. Here, we present our preferred technique for clinical examination of the hip, focusing on the assessment of hip instability.

Results:

While no one maneuver is sufficient to diagnose hip instability, incorporation of multiple examinations in conjunction with radiographs can help to properly diagnose the presence of hip instability.

Discussion/Conclusion:

Hip instability is a challenging clinical diagnosis, and many examination maneuvers have been described to assess for hip instability. In this technical note, we describe our preferred technique for clinical examination of the hip, focusing on the assessment of hip instability.

Graphical Abstract

This is a visual representation of the abstract.

Video Transcript

We present our preferred technique for the clinical evaluation of the hip with a focus on assessment of hip instability.

Here are our disclosures.

Hip instability is a challenging clinical diagnosis and can be present in the absence of radiographically diagnosed hip dysplasia. Presentation of hip instability can overlap with presentation of hip impingement. Hip instability can cause significant pain and disability in patients either as a primary pathology or as a complication of surgery. Here, we present our preferred technique for clinical examination of the hip, focusing on the assessment of hip instability.

Patient evaluation of hip instability includes radiographic imaging of the hip with measurements of the lateral center edge angle, the anterior center edge angle, the acetabular inclination or Tönnis angle, the femoro-epiphyseal acetabular roof (FEAR) index, and the cliff sign.

The lateral center edge angle is measured by drawing a perfect circle around the femeral head. A line in then drawn across the ischia and a line perpendicular to this is drawn vertically. The angle between this vertical line with the center of the femeral head identified is then drawn out to the lateral edge of the sourcil, and this angle will be the lateral center edge angle.

Normal lateral center edge angle has been reported to be between 25-40°. Dysplasia is defined as a lateral center edge angle below 25°, and borderline dysplasia has been described to be between 20-25° or even between 18-25° of lateral center edge angle. The anterior center edge angle is measured on a false profile view of the hip. A line is drawn vertically to the center of the femeral head and then to the anterior most aspect of the sourcil. The angle formed here is the anterior center edge angle.

An anterior center edge angle of <25° may indicated inadequate anterior femoral head coverage. The acetabular inclination or Tönnis angle is drawn with the Cobb tool. A line is drawn from one teardrop to the other, and then the angle between this line and the line drawn from the medial to lateral sourcil is the Tönnis angle.

A normal Tönnis angle is described as between 0-10°. If >10°, this is a concern for possible dysplasia or instability of the hip.

The femoro-epiphyseal acetabular roof (FEAR) index is determined by drawing 2 lines. The first line is the line drawn in the central third of the physeal scar, and the second line is drawn between the most medial and lateral aspect of the sourcil. The FEAR index is positive if the angle diverages laterally and its negative if the angle diverges medially.

If the femoral head does not completely fill a perfect circle on the anterior-posterior pelvis, this is a positive cliff sign.

The first step in evaluating patients is to determine ligamentous laxity. We do this by assessing the Beighton test score. We check hyperextension of the elbow, the ability to bring the thumbs to the ipsilateral forearm and the ability to hyperextend the small fingers. We also check if patients can place their palms flat on the floor with knees straight, and hyperextension of the knee. The patient gets one point for each of these items that are positive. A score greater than 4 is considered hypermobility.

To begin the hip examination, it is important to stand on the side of the hip that is being examined. We begin with a log roll and then gently bring the hip up into flexion. With the hip flexed to 90° and axial pressure to stabilize the pelvis, internal rotation is assessed and then external rotation. The leg is then placed in extension where external rotation and internal rotation in extension are assessed using the tibial crest as our neutral. The leg is then abducted, and here the knee is dropped down off the table with slight external rotation as one way to measure anterior apprehension.

We then perform the Stinchfield test asking the patient to perform a straight leg raise. Resistance is applied, and if the patient has anterior pain, this is a positive Stinchfield test. We then palpate the greater trochanter and, if pain is replicated here, the patient may have abductor tendonitis or greater trochanteric bursitis. A lower extremity sensory examination is then performed, and dorsiflexion and plantarflexion are assessed. Pulses are palpated, and then the examination is performed on the other side. Supine adduction and abduction strength is then assessed, and the patient is then asked to perform a crunch or sit up in order to assess for core muscle injury. We then have the patient roll on to their stomach for a prone examination of the hips. We begin with assessment of thigh foot angle. Internal and external rotation in the prone position are then assessed.

The Prone Apprehension Relocation Test (PART) is performed with the patient’s leg slightly extended and abducted. The patient is asked to relax their knee into the examiner’s hand, and anterior pressure is applied on the femur. A positive PART is replication of the anterior hip pain with anterior force on the femur that is relieved when the pressure is removed.

The posterior apprehension test is performed with the patient supine. The hip is flexed to approximately 90° and then slightly abducted with internal rotation of the hip and posterior force applied. The patient’s pain will be replicated if they have posterior instability.

The hip dial test is performed with the patient supine. The feet are brought into internal rotation and then allowed to fall out to the side. In this patient, the right foot falls into more external rotation than the left, indicating possible instability of the right hip.

The axial distraction test is performed with the patient supine. The hip is flexed to approximately 30° as well as the knee flexed to approximately 30°. The examiner puts his or her leg beneath the patient’s thigh and pulls axial distraction on the hip. A positive finding is replication of the pain.

The hyperextension external rotation test is performed with the patient first sitting at the edge of the table and then lying supine. The patient flexes the unaffected leg to the chest which hyperextends the affected leg. The examiner then rotates the affected leg into external rotation, and a positive test is replication if there is pain in the anterior groin.

The abduction hyperextension external rotation test is performed with the patient lying in the lateral decubitus position. The hip is abducted approximately 30°, extended, and then externally rotated. Anterior pressure is placed with the hand against the posterior aspect of the greater trochanter. A positive finding is replication of pain.

The prone external rotation test is performed with the patient prone. The knee is flexed to approximately 90°. The hip is then externally rotated, and pressure is placed on the greater trochanter. If the patient has replication of pain, this is a positive test finding.

Here is a summary of how to perform each of the included maneuvers to test for hip instability.

In summary, many examination maneuvers have been described to assess for hip instability, which is a challenging clinical diagnosis. No single test can be used to diagnose instability. Incorporation of these examinations in evaluation of the patient, in conjunction with hip and pelvis radiographs, can help to identify the presence of hip instability.

Thank you.