Clinical Examination of Hip Dysplasia/Instability
by Mike Reiman, PT, PhD, ATC
Patients with hip dysplasia and instability are reported to have similar patient presentations as those with femoroacetabular impingement (FAI) syndrome.(1,2) While other non-arthritic hip related pathologies, namely FAI syndrome, are undergoing unprecedented growth in surgical treatment(3) and outcome reporting,(4) hip dysplasia and instability continue to be poorly understood and reported.(1,2)
Developmental dysplasia of the hip (DDH) is reported to be involved in 20 to 40% of patients with hip osteoarthritis,(5-7) demonstrating a stronger relationship with osteoarthritis than FAI syndrome. Despite widespread screening for dysplasia at birth and infancy, several cases are not diagnosed until adulthood.(8,9) There has been a 40-fold variation in prevalence reporting of DDH in part due to variable definitions.(8)
The diagnosis of acetabular dysplasia in the adult has traditionally focused on radiography, with a lateral center-edge angle measurement of <20 to 25 deg and/or anterior center-edge angle of <20 deg as primary definitions.(1) The clinical diagnosis of dysplasia has traditionally focused on described risk factors, specifically related to developmental dysplasia of the hip (e.g. female sex, history of low birth weight and breech birth, family history).(10-12) The clinical diagnosis of hip dysplasia and instability is challenging due to a lack of specific signs and symptoms and a typical subtle presentation.(13)
Hip dysplasia is suggested as a condition of instability in the hip;(14) an extra-physiological hip motion causing pain and impairing function.(15) Hip instability is a term encompassing a broad range of causes from trauma, generalized ligamentous laxity, collagen disorders, bone abnormalities and soft tissue laxity.(16) Currently there are no established objective or radiological signs specific to hip instability.(17)
A principle purpose of the diagnostic process is to provide the practicing clinician with enough information to make optimal decisions for subsequent treatment.(18) Therefore, the purpose of this post is to report the current evidence regarding the clinical and radiographic diagnosis of hip dysplasia and instability.
The current physical examination procedures for the diagnosis of hip dysplasia and/or instability are reported as ‘instability’ tests; although it is worth repeating that hip dysplasia, by nature, is a condition of hip instability.(14) There have been a few reports, mostly in conference presentations, of various physical examination tests for hip instability. The following physical examination tests for hip instability are divided into tests with and without reported diagnostic accuracy.
Physical Examination Tests without Reported Diagnostic Accuracy
Movement: With the hip in a neutral flexion/extension and abduction/adduction position, the clinician grasps the patient’s lower extremity (LE) at the femur and tibia and is passively rolled into full internal rotation. The LE is released and allowed to externally rotate.
Assessment: Evaluate side-to-side range-of-motion (ROM) differences and for the presence of mechanical clicking. Patients with passive external rotation (ER) greater than 45° are considered to have a positive (+) test.
Diagnostic Accuracy: Not reported.
LOG ROLL TEST
Movement: With the hip in a neutral flexion/extension and abduction/adduction position, the patient’s LE is passively rolled into full IR and ER.
Assessment: Evaluate side-to-side ROM differences and clicking. A click reproduced during the test is suggestive of labral tear, while increased ER ROM may indicate iliofemoral ligament laxity.
Diagnostic Accuracy: Not reported.
Physical Examination Tests with Reported Diagnostic Accuracy
Two current studies report enough information to provide the reader with the capability of calculating the diagnostic accuracy of various physical examination tests for this diagnosis.(19,20) The physical examination tests reported in these studies are the following:
ABDUCTION-HYPEREXTENSION-EXTERNAL ROTATION (AB-HEER) TEST
Movement: Patient is in the lateral decubitus position with the affected hip on top of the non-affected hip. The clinician then abducts the hip to 30 to 45 deg, extends and ER the hip while providing an anteriorly directed force to the posterior greater trochanter.
Assessment: A (+) test is reproduction of the patient’s anterior hip pain.
Sensitivity (SN) 80.6, specificity (SP) 89.4, positive likelihood ratio (+LR) 7.6, negative likelihood ratio (-LR) 0.22.
A moderate shift in post-test probability was determined with a positive (+) test (helping to rule in the diagnosis) and a small shift in post-test probability was determined with a negative (-) test (helping to rule out the diagnosis) in one study of low quality.
PRONE INSTABILITY TEST
Movement: Patient is in prone with legs relaxed. The hip is ER’d, while the clinician applies a downward force on the posterior greater trochanter.
Assessment: Reproduction of anterior hip pain is consistent with a (+) result for instability.
SN 34, SP 98, +LR 15.9, -LR 0.68
A large shift in post-test probability was determined with a positive (+) test (helping to rule in the diagnosis) and a very small shift in post-test probability was determined with a negative (-) test (helping to rule out the diagnosis) in one study of low quality.
HYPEREXTENSION-EXTERNAL ROTATION (HEER) TEST
Movement: Patient is supine at the foot of the table with the LE’s hanging of the edge of the table. The contralateral leg is held in full flexion with the knee to the chest by the patient. The clinician applies an anteriorly directed force at the hip by performing hyperextension and ER of the hip to be assessed.
Assessment: A (+) test is reproduction of the patient’s anterior hip pain.
SN 71, SP 85, +LR 4.8, -LR 0.34
A small shift in post-test probability was determined with a positive (+) test (helping to rule in the diagnosis) and a small shift in post-test probability was determined with a negative (-) test (helping to rule out the diagnosis) in one study of low quality.
FOOT PROGRESSION ANGLE WALK (FPAW) TEST
Movement: The patient is instructed to ambulate at their baseline functional pattern for approximately 20 feet. During this baseline gait assessment, categorization of their ipsilateral foot progression angle was characterized as neutral, out-toeing, or in-toeing. The patient is then instructed to ER their foot 15 deg from their baseline pattern. The gait assessment is then repeated. The patient is to maintain the equivalent abduction/adduction of the LE with the assigned rotation. Measurements were standardized by having patients stand on a blank sheet of paper, measuring 15 deg with a goniometer, and marking the location for their reference.
Assessment: (+) test was the presence of hip pain during testing or exacerbation of symptoms if pain was present at their baseline gait assessment.
SN 67, SP 70, +LR 2.2, -LR 0.5
A small shift in post-test probability was determined with a positive (+) test (helping to rule in the diagnosis) and a very small shift in post-test probability was determined with a negative (-) test (helping to rule out the diagnosis) in one study of high quality.
FLEXION-ABDUCTION-EXTERNAL ROTATION (FABER) TEST
Movement: The patient is supine with LE’s relaxed. The clinician moves the LE to be assessed into the combined motions of hip flexion, abduction and ER; placing (if possible) the foot of the LE to be assessed just superior and lateral to the patella of the non-assessed LE.
Assessment: (+) test was the presence of hip pain during testing.
SN 54, SP 90, +LR 5.4, -LR 0.5
A moderate shift in post-test probability was determined with a positive (+) test (helping to rule in the diagnosis) and a small shift in post-test probability was determined with a negative (-) test (helping to rule out the diagnosis) in one study of high quality.
Take home points:
The diagnosis of hip instability/microinstability is currently vague and its specific relationship to an imaging diagnosis of acetabular dysplasia is still unclear.
Currently, the physical examination is limited to a few tests of reported diagnostic accuracy. The tests described here should be utilized as one small component of a more comprehensive examination to include assessment of physical impairments, patient-reported outcome measures (including a generalized ligamentous laxity scale), personal and psychosocial contextual factors, as well as imaging.
The reporting studies examining these tests generally report these tests as having a little greater capacity to help rule in the diagnosis of hip instability than to rule it out.
The prone instability test, when positive, is a promising test to help determine the diagnosis of hip instability/microinstability.
Caution is warranted in interpretation of the log roll test due to the confounding issue of femoral and tibial torsion.
Anecdotally, I find the AB-HEER and HEER tests (despite the diagnostic accuracy) clinically useful in athletes complaining of symptoms with rotational activities, especially overhead throwing and batting. I also find varying the frontal plane motion (abduction/adduction) during these tests can be helpful in these clients.
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