An infant managed in a Pavlik harness develops an absent patellar reflex on the affected side with weakness of knee extension. Radiographs show no change in hip position. What is the most likely cause?

• A Excessive abduction producing avascular necrosis
• B Excessive flexion compressing the femoral nerve ✓
• C Traumatic dislocation of the knee
• D Common peroneal nerve stretch from harness straps

Explanation

Excessive hip flexion beyond 100 to 110 degrees in a Pavlik harness can cause inferior displacement of the femoral head against the obturator ring and compression of the femoral nerve beneath the inguinal ligament, producing quadriceps weakness and loss of the knee jerk. This resolves with reducing the flexion angle. Avascular necrosis results from forceful wide abduction, which threatens the circumflex vessels, not the femoral nerve.

Reference: Lovell and Winter's Pediatric Orthopaedics, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.