Dislocation of a femur fracture after femoral nerve block.

Abstract

Femoral nerve block (FNB) is increasingly used as an analgesic modality in patients with femoral fracture both in the emergency department and preoperatively. We describe an occurrence of unexpected dislocation of the fracture after FNB. An FNB was administered to treat pain in a 48-year-old patient with metastatic breast carcinoma and multiple bone metastases. A diagnostic FNB with 20 mL of 0.25% levobupivacaine resulted in analgesia but also in unexpected gross deformity in the proximal right femur. An x-ray revealed a pathologic fracture of the proximal third femur diaphysis, with reduction and angulation of fragments, necessitating urgent surgery. Femoral nerve block confers effective analgesia for femur fracture. However, relaxation of the quadriceps femoris muscle may destabilize the fracture because of an unopposed tone of the hamstrings and/or thigh adductors.