How to assess for adduction or abduction deformity in a patient with bilateral hip Avascular Necrosis (AVN)?

Assessment of Adduction or Abduction Deformity in Bilateral Hip AVN

In bilateral hip AVN, assess for adduction or abduction deformity by comparing each hip's position relative to the body's midline with the patient supine and legs straight—the affected hip(s) will deviate from parallel alignment with the table edge, requiring passive correction to achieve neutral positioning.

Clinical Examination Technique

Patient Positioning

• Place the patient supine on the examination table with legs initially straight and parallel, toes pointing upward 1
• Align the limbs and trunk to the body's midline as closely as possible to establish a neutral reference position 1
• Ensure the pelvis is level and not rotated, as pelvic obliquity can create false impressions of hip deformity 1

Identifying the Deformity

• Observe resting position: In bilateral AVN, one or both hips may rest in an adducted (legs crossed toward midline) or abducted (legs splayed away from midline) position 1
• Assess alignment: The leg should normally be parallel to the edge of the examination table when properly positioned 1
• Deviation from neutral: Any hip that cannot be passively positioned parallel to the table edge without resistance indicates a fixed deformity 1

Range of Motion Assessment

• Active range of motion: Have the patient actively abduct and adduct each hip while noting any limitation, pain, or asymmetry 2, 3
• Passive range of motion: Gently move each hip through abduction and adduction to identify:
  • Fixed deformities (structural limitation that cannot be overcome)
  • Contractures (soft tissue restriction)
  • Pain-limited motion 2, 3
• Key finding in AVN: Limitation of the final phase of hip movement, especially inward rotation and abduction, is characteristic 2

Bilateral Assessment Considerations

Comparing Both Hips

• In bilateral AVN, carefully examine both hip joints to reveal asymmetry in the range of movement, even when both are affected 2
• One hip may demonstrate more severe deformity than the other despite bilateral disease 2
• Document the degree of deviation from neutral for each hip separately to track progression 1

Measurement Technique

• Adduction deformity: Measure the angle between the leg's long axis and the body's midline when the hip cannot be brought to neutral—the leg remains crossed toward the opposite side
• Abduction deformity: Measure the angle when the leg remains splayed away from midline despite attempts at neutral positioning
• Use a goniometer for objective measurement and serial comparison 1

Clinical Pitfalls and Important Considerations

Common Examination Errors

• Pelvic compensation: Patients may tilt their pelvis to compensate for hip deformity, creating false neutral positioning—always stabilize the pelvis during assessment 1
• Bilateral symmetry misconception: In bilateral AVN, symmetric deformities may appear "normal" if not compared to true anatomic neutral 2
• Pain-related guarding: Distinguish between true structural deformity and pain-limited positioning by gentle passive manipulation 2, 3

Physical Examination Limitations

• Physical examination has limited sensitivity (0-50%) for detecting early AVN, though specificity is higher (67-92%) 4
• Negative physical examination findings do not exclude AVN, with negative predictive values >90% but positive predictive values <17% for single tests 4
• In early AVN, only subtle limitations of hip movement may be present, particularly in the final degrees of rotation and abduction 2, 3

Associated Clinical Findings

• Pain patterns: AVN characteristically causes hip, groin, buttock, or low back pain that worsens with activity and at night 2, 3
• Gait abnormalities: Observe for limping, waddling gait, or compensatory movement patterns that suggest hip pathology 5
• Functional limitations: Reduced extension and abduction by 25% or more during active range of motion is significant 3

Diagnostic Confirmation

When Physical Examination is Insufficient

• If even slight limitation of hip movement range is detected, obtain hip radiographs in two projections 2
• For suspected early-stage AVN with equivocal radiographs, MRI is the gold standard for diagnosis 4, 3
• Scintigraphy can be decisive when suspicion exists for early radionegative disturbances of femoral head blood supply 2

Documentation Requirements

• Record specific degrees of adduction/abduction deformity for each hip separately
• Note whether deformity is fixed (structural) or flexible (positional)
• Document any compensatory pelvic positioning or leg length discrepancy
• Serial measurements allow tracking of deformity progression or response to treatment 1