Ecoguided Genicular Nerve Block

Osteoarthritis affects approximately 302 million people worldwide, with the knee, hip, and hands being the most commonly affected areas. Knee osteoarthritis is highly prevalent and increasing in the region due to aging, obesity, and the progressive sedentary lifestyle of the population. According to recent epidemiological studies, it has a prevalence of 29.3% in the Spanish population.

Currently, multiple treatment options are available, ranging from conservative measures to surgical procedures. Within conservative treatment, various tools benefit patients and may even avoid the need for surgery. These non-surgical options include patient education, weight control, physical exercise, orthotics, oral analgesics, topical anti-inflammatories, and interventional procedures. However, there are no prior studies demonstrating the advantages of one over another, and many do not follow up beyond three months.

When conservative treatment is ineffective, surgical intervention is usually considered. Therapeutic options include knee arthroscopy, high tibial osteotomy, total knee replacement, and unicompartmental knee replacement in patients without lateral compartment disease.

Traditionally, rest and caution in exercise were recommended for knee osteoarthritis pain. However, this paradigm has been strongly rejected. One of the current first-line treatments for knee osteoarthritis is physical exercise, with quadriceps strengthening being the most indicated. Most patients seek recommendations on what type of exercise to perform, including the duration, intensity, and frequency for better adherence. No exercise has been shown to be superior to another, with the most studied being yoga and tai chi exercises.

Despite the well-documented benefits of exercise for this condition, one emerging procedure for pain management is the genicular nerve block. This treatment option can facilitate progress in the exercise program. It is also indicated for patients who have previously had successful genicular block, those who do not wish to undergo surgery, those not eligible for surgery, or even post-surgical patients for better pain control.

The term "genicular nerves" refers to a group of nerves responsible for the sensory innervation of the knee joint capsule and the internal and external ligaments. The superior and inferior medial genicular nerves are sensory branches of the tibial nerve, whereas the superior and inferior lateral genicular nerves are branches of the common peroneal nerve. These nerves are named after the arteries they accompany, which are located using ultrasound during the procedure.

Genicular nerve block is a simple technique that significantly reduces opioid consumption in patients undergoing total knee arthroplasty within the first 24 hours. It also provides temporary relief that allows progression in the rehabilitation program through a structured exercise regimen. This technique involves injecting medication into the genicular nerves, locating the genicular artery using Doppler ultrasound. Various cadaveric studies have investigated the anatomical distribution of the descending genicular artery and the nerves accompanying its branches.

Some authors suggest that up to 10 points may need to be blocked for complete coverage. However, this is not feasible in routine clinical practice. Most studies target three sensory nerves of the knee: the superior lateral genicular nerve, the superior medial genicular nerve, and the inferior medial genicular nerve. In most studies, 2 to 3 ml of local anesthetic is administered per point. It has been shown that 0.5 ml of injected fluid spreads within the tissue over an area of 6 cm², likely covering more nerve targets with 2 ml. Typically, the procedure involves infiltrating local anesthetic (lidocaine, bupivacaine, ropivacaine, levobupivacaine) and 20 mg of corticosteroid (triamcinolone).

In this study, bupivacaine is chosen as the local anesthetic, as it inhibits prostaglandin production by binding to the E2 receptor, providing an anti-inflammatory effect. It is a lipophilic amide-type anesthetic with 100% bioavailability and a longer duration than other local anesthetics. Additionally, it produces a more significant blockade of sensory and sympathetic nerve fibers than motor fibers, differentiating it from other local anesthetics.

Recent guidelines for the treatment of knee osteoarthritis highlight the recommendation of intra-articular corticosteroid injections. However, several studies mention that systemic and local corticosteroid effects can cause adverse effects such as skin atrophy, hypertension, insulin resistance, decreased bone mineralization, and septic arthritis, among others. Nonetheless, these effects have not demonstrated a direct relationship with pain, functionality, or radiological changes.

The clinical benefit of corticosteroid administration compared to local anesthesia alone remains unclear. Given the potential adverse effects, corticosteroids may not be suitable as adjuvants. Therefore, genicular nerve block using local anesthetic alone proves to be a promising technique, avoiding the use of corticosteroids and not being an intra-articular procedure.

A study is proposed at a tertiary hospital in the Community of Madrid (Hospital Universitario Fundación Alcorcón). Considering the absence of previous studies that evaluate and quantify the three described treatment options, this study aims to address this objective through a pilot experimental randomized controlled trial. All patients will receive guidelines for an exercise program, and the outcomes of adding genicular nerve block with and without corticosteroid will be assessed. This unprecedented study could identify the optimal treatment for this prevalent and debilitating condition in a significant portion of the population. Additionally, it will help optimize resource allocation for these patients by identifying the best therapeutic target, thus avoiding unnecessary resource consumption

Inclusion criteria

• Age over 18 years
• Anterior knee pain of patellofemoral origin and/or femorotibial compartment osteoarthritis with no previous response to pharmacological treatment (oral and/or topical)
• Pain duration of 3 months
• Pain assessment scale (Numerical Rating Scale) ≥ 5
• Radiological study with Kellgren-Lawrence classification > 2

Exclusion criteria

• Allergy to the active ingredients and excipients of: bupivacaine, triamcinolone, or saline solution
• Patients who have undergone total or unicompartmental knee replacement surgery
• Viscosupplementation or intra-articular corticosteroid injection within the last 3 months
• Pregnant women or those suspected of being pregnant
• Cognitive impairment or additional neuropsychiatric symptoms
• Failure to sign informed consent or revocation of it
• Patients with heart disease requiring blockade with levobupivacaine
• Inability to write, speak, or read in Spanish
• Active tumoral or infectious pathology
• Osteoarthritis secondary to inflammatory pathology