In cases of orbital blowout fracture of the orbital floor, which clinical sign on elevation test (forced duction test) distinguishes entrapment of the inferior rectus from pure contusion palsy?

• A Normal forced duction test with diplopia on upward gaze
• B Enophthalmos greater than 3 mm
• C Positive forced duction test (resistance to passive elevation of the globe) ✓
• D Periorbital emphysema on Valsalva

Explanation

The forced duction test (FDT) is the definitive bedside test to distinguish mechanical restriction (entrapment) from neural palsy. In inferior rectus entrapment in an orbital floor fracture, the inferior rectus muscle and/or periorbital fat is trapped in the fracture line. When the globe is passively elevated with forceps under topical anesthesia, there is palpable resistance — positive FDT. In a contusion palsy (nerve or muscle damage without entrapment), the FDT is negative (no resistance) but active elevation is limited. Enophthalmos and emphysema confirm fracture presence but do not distinguish entrapment from palsy.

Reference: Khurana Comprehensive Ophthalmology, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.