Background
Avascular necrosis (AVN) of the femoral head is most commonly seen in children 1.5 to 10 years. AVN is caused by a disruption of blood supply to the hip joint leading to micro osteonecrosis and eventual collapse of the femoral head.
Two types of AVN occur in childhood. The first is an idiopathic process commonly known as Legg-Calvé-Perthes' disease. The second is an acquired condition. Etiologies include trauma, chemotherapy, synovitis, hypothyroidism, hemoglobinopathy, epiphysial dysplasia, and steroid therapy.
In children, AVN commonly presents as a limp and is often associated with hip or referred knee pain. While the hip joint is innervated by the sensory articular branches of the obturator and femoral nerves, referred pain may be from the activation of the obturator nerve which innervates both the hip and the distal thigh or knee.
For pediatric patients, chronic hip/knee pain can be debilitating. In adults, there are case reports of pulsed radiofrequency ablation (RFA) as a beneficial alternative pain treatment of last resort. Coolief is a new cooled RFA technique that uses cooled circulating water to create a larger treatment area than conventional RFA. A PubMed search revealed no prior reports of RFA for children, and no prior reports of cooled RFA for children or adults as treatment for hip/knee pain associated with AVN.
Case description
Patient LG is a 15 yo female with h/o sickle cell SS disease and alpha thalassemia with chronic bilateral hip pain from AVN. Despite several corrective surgeries, her chronic pain has lead to worsening physical function and increasing opioid use. Patient and parent consented to this procedure. Parent verbal consent was obtained for this case report.
This procedure was conducted under GA. After femoral and obdurator nerves were identified under fluoroscopy, motor stimulation to 2 V was negative to ensure that there was no motor involvement. Local anesthetics were injected and then 2 minutes of 60 degs Celsius thermal (cooled) radiofrequency ablation were performed on each nerve (Halyard Cooled RF System, Alpharetta, Georgia). This same procedure was carried out on the contralateral side.
Two month post procedure, patient’s mother feels that bilateral hip pain is 80% improved. Patient is now able to play tennis again and uses less opioids. Pain relief appears to be sustained.
Discussion
Chronic hip pain from AVN can be a debilitating problem for children. Cooled RFA of the obturator and femoral sensory nerves may be a treatment option in this pediatric population. It may help reduce opioid consumption, improve function, and reduce hospitalizations. Further studies are warranted to assess the utility of cooled RFA for hip/knee pain in children with AVN of femoral head.
Reference
Divi S, Bielski R. Legg. Legg-Calvé-Perthes' Disease. Pediatric Annals 2016; 45:4:e144-199.
Malik A, Simopolous T, Elkersh M, Aner M, Bajwa Z. Percutaneous Radiofrequency Lesioning of Sensory Branches of the Obturator and Femoral Nerves for the Treatment of Non-Operable Hip Pain. Pain Physician. 2003;6:499-502, ISSN 1533-3159
