Cooled radiofrequency ablation for pain related to Perthes’ disease: a novel application

Abstract

Perthes’ disease is a rare paediatric condition involving idiopathic avascular necrosis of the femoral head, leading to degenerative hip joint disease. While joint replacement surgery is considered as the definitive surgical choice of managing degenerative hip disease, alternative methods of pain relief are available, especially for young patients, to defer joint replacement to a later date. One method of reducing pain for 18–24 months is cooled radiofrequency ablation (CRFA). CRFA has been gaining recognition as an effective treatment option for chronic musculoskeletal-related pain in multiple joints. This is the first case report describing the successful use of CRFA in the non-surgical management of Perthes’ disease-related osteoarthritic hip pain in a man in his 40s. CRFA treatment led to a reported subjective improvement in pain of 60%–70%, with a documented objective improvement in the Oxford Hip Score from 18 to 40 within 6 weeks of the CRFA procedure.

Background

Perthes’ disease is a rare condition involving idiopathic avascular necrosis of the hip affecting up to 30 in every 100 000 children under the age of 15 years.¹ Even with early treatment, many patients are still left with symptomatic residual femoral head deformity, with hip pain, shortened lower limb and/or coxa vara resulting in a residual limp, reduced range of hip motion or hip flexor and/or adductor contractures.² In addition, these patients are at a higher risk of developing early-onset degenerative joint disease which can cause significant pain and morbidity.

Conservative management of degenerative joint diseases includes analgesia, physiotherapy and, more recently, nerve radiofrequency ablation (RFA). Since 2008, there have been increasing evidence supporting the use of cooled RFA (CRFA) for management of chronic hip, knee and back pain.³ Although there have been reports of successful treatment of avascular necrosis and osteoarthritis related hip pain, to our knowledge, this is the first case report describing the successful application of CRFA in the treatment of Perthes’ disease in a patient who developed secondary osteoarthritis following a late diagnosis at the age of 40 years.

Case presentation

A man in his 40s who had a previous history of Perthes’ disease was diagnosed with secondary osteoarthritis at the age of 40 years. On presentation, his Oxford Hip Score was 18.

Investigations

His pelvic X-ray showed flattening of the articular surface and collapse of the femoral head bilaterally with epiphysial sclerosis and evidence of joint space narrowing (figure 1).

Figure 1.

Antero-posterior (A), left lateral (B) and right lateral view (C) of pelvic X-ray showing flattening of the articular surface and collapse of the femoral head bilaterally with epiphysial sclerosis and evidence of joint space narrowing.

While the option of joint replacement surgery was offered, the patient was keen to try non-operative options, to delay the risks of surgery as well as possibility of revision surgery given his young age. He trialled simple analgesia and a period of physiotherapy without success and exhausted all conservative options.

Treatment

Instead, the patient opted for bilateral CRFA treatment, using the Coolief (Avanos, Alpharetta, GA) system. The procedure was performed under general anaesthetic with the patient positioned supine. Intraoperative imaging was used to obtain symmetrical obturator foramen views. A percutaneous approach was used superior and inferomedial to the hip joint. Femoral–accessory branches were targeted via the superior approach with the probe tip against the iliac bone superior to the hip joint. The obturator–accessory branches were targeted via an inferomedial approach, with the probe tip against the inferior ramus of pubis bone, adjacent to the pelvic tear drop (figure 2). Before CRFA was performed, a 2 Hz motor stimulation up to 2 V confirmed lack of muscle contraction to avoid iatrogenic injury to motor branches near the radio frequency probe tip.

Figure 2.

Fluoroscopic image of the right (A) and left hip (B) showing cooled radiofrequency ablation of the lateral femoral and lateral obturator nerves bilaterally.

CRFA was then performed at two closely related points superior to the hip joint and two closely related points adjacent to the pelvic tear drop. Local anaesthetic (2% lignocaine) was infiltrated to deep tissue. No complications related to the procedure were encountered.

Outcome and follow-up

The patient was reviewed 6 weeks after the procedure, with an Oxford Hip Score of 40 (increased from 18) and was found to have approximately 60%–70% subjective improvement in pain, mobilising well with intact range of motion of his hips bilaterally. Six months after the procedure, the patient had an Oxford Hip Score of 39 and was found to have approximately 60%–70% improvement in pain, mobilising well.

Discussion

Perthes’ disease, short for Legg-Calve-Perthes disease, was first described in 1910 and refers to idiopathic avascular necrosis of the head of femur. It predominantly affects the paediatric population aged 4–8 years, with a male-to-female ratio of 4:1.^{1 4} Diagnosis is via plain hip X-rays, using the frog leg lateral view in addition to the conventional antero-posterior and lateral views. MRI may be required for very subtle cases. Treatment can be conservative (physiotherapy, activity restriction and non-steroidal anti-inflammatories) or surgical depending on age of diagnosis and severity of the avascular necrosis, where patients diagnosed earlier than 6 years old have a better prognosis and undiagnosed patients are at increased risks of developing secondary osteoarthritis, which may be debilitating.⁵

RFA refers to the use of radiofrequency waves to cauterise tissue. It was first described in 1891 by d’Arsonval, who discovered the thermal effects of radiofrequency waves passing through tissue.⁶ It was then integrated into modern medicine in 1928 as a Bovie knife used for cauterising and cutting tissue. Then in 1931, RFA was first used by a German surgeon named Kirschner to treat trigeminal neuralgia via thermocoagulation of the Gasserian ganglion.⁷ The first case series describing the successful use of CRFA for management of chronic pain from sacroiliitis and knee osteoarthritis was in 2008 and 2015, respectively.^{8 9} Since then, there have been increasing reports of the use of CRFA for treating chronic hip pain from avascular necrosis or osteoarthritis.^{10 11}

CRFA is often performed percutaneously using an electrode probe with a thermocouple that measures the temperature changes throughout the procedure. It functions by delivering a small radiofrequency current from a generator and peristaltic pump through an insulated electrode, converting the energy into frictional heat from charged molecules (known as ionic heating), causing destruction via intracellular fluid loss and protein denaturation.¹² This is done under fluoroscopy with a radiopaque marker located at the proximal end of the active tip. Standard RFA causes an elliptically shaped lesion with a size limited by the charred tissue acting as a significant insulator.¹³ In comparison, CRFA transmits radiofrequency waves through water-cooled electrodes, maintaining lower temperatures at the interface between the tip and tissue, enabling more radiofrequency energy to be delivered to the target nerves, creating lesions that are spherically shaped with a volume that is five times larger than standard RFA. As per the manufacturer, other potential benefits include greater projection of >45% beyond the probe tip and probe angle independence where operators are free to use the best angle to approach target nerves with complicated pathways, without being limited to parallel probe placement.¹⁴

There are several clinical uses of RFA, including endoscopic RFA for treatment of gastrointestinal and hepatobiliary diseases such as Barrett’s oesophagus, catheter RFA for treatment of cardiac arrhythmias and varicose veins and percutaneous RFA for treatment of benign, premalignant and malignant lesions of the musculoskeletal, thyroid, hepatic, renal and respiratory systems, including primary and metastatic disease.^15–19 Similarly, there has been increasing evidence in the literature suggesting the successful use of CRFA in reducing chronic pain in degenerative disc diseases, lumbar facet joint pain, sacroiliac joint pain, chronic degenerative hip, knee and back pain and even trigeminal neuralgia facial pain.^20–22 CRFA does this by targeting specific nerves that cause the pain, using heat to disrupt the pain pathways, much like performing a nerve block.²³ Studies have reported that CRFA is clinically superior to other treatments for chronic knee pain such as intra-articular steroid or hyaluronic acid injections, where patients reported >65% pain relief lasting >12 months after receiving CRFA.¹³ Naber et al found that in 11 patients suffering from chronic hip pain from avascular necrosis, combined fluoroscopy and ultrasound-guided anterior CRFA of the lateral femoral and lateral obturator nerves resulted in a reduction in pain scores on the visual analogue scale from a mean of 7.6–2.3 with 5 patients reporting more than 50% pain relief from the CRFA.¹¹ In comparison, the patient in this article reported a subjective improvement of 60%–70%, with a documented improvement in the Oxford Hip Score from 18 to 40 within 6 weeks, demonstrating its efficacy in the short term. Efficacy of CRFA has been reported in the literature to last from 12 to 24 months, with some papers describing benefits up to 36 months.^24–29 During this time, ongoing review with treating clinician is important.

CRFA procedure is relatively safe with minimal complications. The main risks associated are damage to surrounding structures depending on the location of CRFA, which can be avoided using image guidance such as combining ultrasound with fluoroscopy. Specifically for the hip, the main risk is inadvertent puncture of the femoral artery and vein, which can potentially lead to pseudoaneurysm, arteriovenous fistula, haemarthrosis and/or osteonecrosis.³⁰ Other potential complications include failure of procedure, infection and bleeding. However, there are many strategies used to prevent these complications, hence the risk is very minor.

Overall, CRFA is a promising modern technique with multiple applications in medical treatment of chronic pain without significant complications. Research in this specialised field is currently limited and further exploration in this area will be beneficial for future patients suffering from chronic hip pain secondary to Perthes’ disease.

Learning points.

• Cooled radiofrequency ablation (CRFA) refers to the delivery of a small radiofrequency current through water-cooled electrodes and converting the energy into frictional heat to cauterise tissues, which can be effectively used for nerve ablation and pain relief.

• Perthes’ disease refers to a paediatric condition involving idiopathic avascular necrosis of the femoral head and can result in premature degenerative joint disease with resulting pain and morbidity.

• CRFA is a promising modern technique with multiple applications in medical treatment of chronic pain without significant complications. It can be an interim measure for pain control prior to definitive joint replacement surgery later on. Patients with chronic hip pain refractory to simple analgesia and/or physiotherapy who are not suitable or willing to undergo definitive surgical management would benefit most from cooled radiofrequency.

Ethics statements

Patient consent for publication

Consent obtained directly from patient(s).