An infant with developmental dysplasia of the hip is treated in a Pavlik harness. At follow-up the mother reports the baby will not kick the legs. On examination there is absent spontaneous knee extension and weakness of quadriceps bilaterally. The most likely cause is:

• A Excessive abduction causing femoral head ischemia
• B Excessive flexion compressing the femoral nerve ✓
• C Brachial plexus traction from tight shoulder straps
• D Common peroneal nerve compression at the fibular head

Explanation

The Pavlik harness holds hips flexed near 90 degrees and abducted. If flexion exceeds about 100 to 110 degrees, the femoral nerve is compressed beneath the inguinal ligament, producing quadriceps weakness and loss of knee extension, which parents notice as reduced kicking. This resolves promptly once flexion is reduced below the safe range. Excessive forced abduction is instead associated with avascular necrosis of the femoral head.

Reference: Tachdjian's Pediatric Orthopaedics, 5th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.