May 1, 2022
adductor canal block for knee arthritis

Adductor Canal Block for Knee Osteoarthritis

Knee osteoarthritis (Knee OA) is one of the most common musculoskeletal diseases in the world, affecting at least 250 million people globally.[1]Hunter D.J., Bierma-Zeinstra S. Osteoarthritis. Lancet. 2019;393:1745–1759. doi: 10.1016/S0140-6736(19)30417-9.. It’s prevalence continues to rise, affecting between 10% and 15% of men and women over the age of 60.[2]Zhang Y., Jordan J.M. Epidemiology of Osteoarthritis. Clin. Geriatr. Med. 2010;26:355–369.. In the United States, knee OA has an economic burden of nearly 90 billion dollars[3]GBD 2015 Disease and Injury Incidence and Prevalence Collaborators Global, regional, and national incidence, prevalence, and years lived with disability for 310 diseases and injuries, 1990–2015: A … Continue reading and is the #2 musculoskeletal disorder in Disability Adjusted Life Years (DALYs) in elderly population following back pain.[4]Prince M.J., Wu F., Guo Y., Gutierrez Robledo L.M., O’Donnell M., Sullivan R., Yusuf S. The burden of disease in older people and implications for health policy and practice. Lancet. … Continue reading

Image 1. Normal knee (left) and knee arthritis (right). Note the joint space narrowing, subchondral sclerosis and osteophyte formation on the right image.[5]Image courtesy of orthobullets, https://www.orthobullets.com/recon/12287/knee-osteoarthritis

Treatment for knee osteoarthritis generally begins with non-surgical management consisting of some combination of analgesic medications, physical therapy, exercise therapy, and emphasis on weight loss. When these treatments fail to control symptoms, physicians will often begin initiating injections including corticosteroids, platelet rich plasma (PRP) and other regenerative therapies. If these do not work, then the patient will often need to consider a total knee arthroplasty.

Image 2. Anatomy of the adductor canal (click to enlarge)[6]Image courtesy of https://anatomyqa.com/, “adductor canal”

The adductor canal block (ACB) is an ultrasound guided procedure that targets the saphenous nerve within the adductor canal to provide analgesia in that distribution. The adductor canal is a cone-shaped anatomic pathway in the distal two thirds of the medial thigh. It extends from the femoral triangle to the adductor hiatus and is about 10 cm in length (range 8 to 15). It contains the femoral artery, femoral vein and saphenous nerve. The saphenous nerve (L3, L4) is a terminal cutaneous branch of the femoral nerve which provides innervation to the anteromedial surface of the leg. At the knee, the infrapatellar branch comes off the saphenous nerve and contributes to the peripatellar plexus and innervates the anteroinferior and medial aspects of the knee.
Image 3. Insertion of needle and advancement under sonographic guidance. White arrowheads indicating the acoustic shadow of spinal needle. SN: saphenous nerve, VM: vastus medialis, FA: femoral artery; *Injectate. (click to enlarge). [7]Ming, Lee Hwee, et al. “Adductor canal block versus intra-articular steroid and lidocaine injection for knee osteoarthritis: a randomized controlled study.” The Korean Journal of Pain … Continue reading

Studies

In 2017, Lee published the first paper looking at the ACB as a treatment option for knee OA.[8]Lee, Doo-Hyung, et al. “Effect of adductor canal block on medial compartment knee pain in patients with knee osteoarthritis: Retrospective comparative study.” Medicine 96.12 (2017). In this 3-month retrospective case-controlled comparative study, they included 200 patients with anteromedial knee OA who had not responded to other conservative treatments. 92 patients received the ACB (9 mL 1% lidocaine, 1 mL 10 mg triamcinolone) and the rest served as a control. At 3 months of follow up, they found improvement of visual analog scale (VAS) and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) at month 1, and decreased opioid consumption per day at 2 months in the ACB group. No adverse events were reported.
Image 4. The image shows the needle (arrows) positioned at 12 o’clock above the femoral artery after injecting the local anesthetic (*) resulting in the formation of the ‘double bubble’ above the FA.[9]Fusco, Pierfrancesco, et al. “‘Inverse Double Bubble’sign for an effective adductor canal block: a novel approach for the ultrasound confirmation of being on the right site.” Regional … Continue reading
In 2021, Salihovic et al published another paper looking at ACB for Knee OA.[10]Salihovic, Mensur, et al. “Effectiveness of Ultrasound-Guided Canal Adductor Blockade for Chronic Pain and Functioning in Knee Osteoarthritis: A Prospective Longitudinal Observational … Continue reading In this single arm study, they treated 77 patients with chronic knee OA with the ACB (14 ml 0.25% levobupivacaine and 100 mcg clonidine). At 1 month, they noted a decrease in pain severity, improved range of motion, improved ambulation, improved quadricep muscle strength. The Knee Injury and Osteoarthritis Outcome Score (KOOS) for pain, activities of daily living, symptoms and quality of life all improved.
Most recently, Lee et al published a randomized, single-blinded trial comparing ACB versus intra-articular steroid injection (CSI) for knee osteoarthritis.[11]Ming, Lee Hwee, et al. “Adductor canal block versus intra-articular steroid and lidocaine injection for knee osteoarthritis: a randomized controlled study.” The Korean Journal of Pain … Continue reading In this study, they recruited 66 patients with knee OA for longer than 6 months and randomized them to either an US guided CSI or US guided ACB. For the ACB, they used 5 mL bupivacaine 0.5%, 5 mL lidocaine 1%, and 10 mL of 0.9% saline. Greater pain relief was seen in the CSI group at 1 month, however the ACB group had better pain relief at 3 months. The ACB group also had greater functional improvement and quality of life scores at 3 months. No side effects were noted.

Summary

In summary, these three studies provide some compelling evidence that the ACB may be a useful tool in the management of knee OA. Identifying which patients will benefit most, likely patients with medial knee OA based on the anatomy of the saphenous nerve, needs to be clarified. Further, where the ACB fits in the treatment algorithm and how it truly compares head-to-head with other non-surgical options requires further research. The optimal injectate for long lasting relief also requires clarification.

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