A Review on Carpal Tunnel Injections
Carpal tunnel syndrome is due to the compression of the median nerve at the level of the wrist (1). Nonoperative treatment typically involves corticosteroid injection into the carpal tunnel to help with hand pain. Ultrasound guided injections are preferred in order to reduce the risk of median nerve injury. Studies have shown that upwards of 79% of patients have relief of symptoms six weeks after the injection (3). Patients with diabetes have been identified to be at risk for recurrent symptoms within one year of the injection (3).
Injections of corticosteroids can be done under ultrasound or palpation guidance into the carpal tunnel. A palpation guided injection is done at the level of the wrist crease. The palmaris longus is identified and an injection is guided just ulnar to the palmaris longus (1).
Ultrasound injection can be done using an in-plane ulnar approach (1). The patient is typically seated and the wrist is supinated and slightly dorsiflexed (2). The preferred transducer is 15-7 MHz or 17-5 MHz (2). Typical injection includes 1cc of 1% Lidocaine and 1cc of 40mg/mL Triamcinolone using a 27g needle (1). The probe will be placed in a transverse position at the level of the wrist crease (1). The median nerve is a hypoechoic structure with a hyperechoic rim that is found superficial to the flexor tendons (4). If there is still confusion regarding whether the provider is evaluating the nerve or a flexor tendon, the probe can be moved more proximal and the median nerve should move deep and radial (6). Providers should first identify the ulnar artery, ulnar nerve, and median nerve all in one view (2). The needle angle is superficial and the needle should travel superiorly to the ulnar artery and nerve to enter the carpal tunnel(2). The medication should be first injected superiorly to the nerve and then repositioned deep to the nerve to hydrodissect the nerve and break up any adhesions (2).
In addition to injections of corticosteroid into the carpal tunnel, a study published in the Archives of Physical Medicine and Rehabilitation looked at platelet rich plasma injections for the treatment of carpal tunnel syndrome. Using the ulnar approach described above, the study randomized patients to either a normal saline or PRP injection into the carpal tunnel with median nerve hydrodissection (5). Both groups showed improvement of symptoms, but the PRP injection had a larger improvement in pain at one year compared to saline (5).
Ulnar sided carpal tunnel injections under ultrasound guidance have been proven to be safe and effective in the treatment of carpal tunnel syndrome. Patients should be aware that blind injections have a higher risk of median nerve injury.
By Gregory Rubin, DO
1) Lee, Jin Young, et al. “Effectiveness of Ultrasound-Guided Carpal Tunnel Injection Using in-Plane Ulnar Approach: A Prospective, Randomized, Single-Blinded Study.” Medicine, vol. 93, no. 29, Dec. 2014, p. e350. PubMed, https://doi.org/10.1097/MD.0000000000000350.
2) Smith, Jay, et al. “Sonographically Guided Carpal Tunnel Injections: The Ulnar Approach.” Journal of Ultrasound in Medicine: Official Journal of the American Institute of Ultrasound in Medicine, vol. 27, no. 10, Oct. 2008, pp. 1485–90. PubMed, https://doi.org/10.7863/jum.2008.27.10.1485.
3) Blazar, Philip E., et al. “Prognostic Indicators for Recurrent Symptoms After a Single Corticosteroid Injection for Carpal Tunnel Syndrome.” The Journal of Bone and Joint Surgery. American Volume, vol. 97, no. 19, Oct. 2015, pp. 1563–70. PubMed, https://doi.org/10.2106/JBJS.N.01162.
4) McDonagh, Cara, et al. “The Role of Ultrasound in the Diagnosis and Management of Carpal Tunnel Syndrome: A New Paradigm.” Rheumatology (Oxford, England), vol. 54, no. 1, Jan. 2015, pp. 9–19. PubMed, https://doi.org/10.1093/rheumatology/keu275.
5) Chen, Si-Ru, et al. “One-Year Efficacy of Platelet-Rich Plasma for Moderate-to-Severe Carpal Tunnel Syndrome: A Prospective, Randomized, Double-Blind, Controlled Trial.” Archives of Physical Medicine and Rehabilitation, vol. 102, no. 5, May 2021, pp. 951–58. PubMed, https://doi.org/10.1016/j.apmr.2020.12.025.
6) Jacobson, Jon. “Wrist and Hand Ultrasound.” Fundamentals of Musculoskeletal Ultrasound, Elsevier.