First, we will review the flexor carpi radialis anatomy. It originates at the medial epicondyle of the humerus. It then travels to the base of the second metacarpal. The flexor carpi radialis is innervated by the median nerve. It flexes the hand at the wrist joint and abducts the hand. Now we will review the cross-sectional anatomy of the flexor carpi radialis muscle. The flexor carpi radialis is highlighted here. The injection will be performed in the proximal forearm. The flexor carpi radialis muscle is located superficial to the ulnar artery, median nerve, and common interosseous artery. Located deep and lateral to the flexor carpi radialis is the radial artery and the superficial branch of the radial nerve. Here the tip of the needle has been placed in the flexor carpi radialis muscle, traveling from medial to lateral. It has traveled through the palmaris longus muscle. Note the location of the ulnar artery, median nerve, and common interosseous artery deep to the target muscle. Also note the radial artery and superficial branch of the radial nerve lateral to the flexor carpi radialis muscle. Let's discuss the anatomy we expect to see on ultrasound. Note the position of the radius and ulna. Outlined here is the flexor carpi radialis muscle and palmaris longus muscle. Note the location of the neurovascular bundle deep to the flexor carpi radialis. Several steps should be carried out prior to injection to ensure patient safety and procedure success. Explain the procedure to the patient. After explaining the risks and benefits of the procedure, obtain informed consent. Check for contraindications. Examine the patient to determine the appropriate muscular targets and dosing plan following manufacturer recommendations. Take time before the procedure to set up the room and make sure that you have adequate assistance. Depending on skill level and comfort with ultrasound guided injections, one to two assistants may be required for this procedure. Assistants may help with operation of the ultrasound machine and the handheld device for electromyography and electrical stimulation. Gather the necessary equipment as described earlier in this video. Position the patient to optimize patient comfort and provider ergonomics. During the procedures demonstrated in this video, the practitioner may not be in the ideal ergonomic position. This is due to filming constraints to ensure proper visualization of the injection for demonstration purposes. Practitioners performing ultrasound guided botulinum toxin injections should follow the ergonomic principles presented in Section 3 of this video. Disinfect the target site per institutional protocol. Conduct a timeout per institutional protocol prior to starting the procedure. You will first need to orient yourself by scanning the target muscle region. The target muscle, flexor carpi radialis, is circled in red here. In Color Flow Doppler imaging, identify the vasculature to avoid during the injection. Here, the needle is being inserted from medial to lateral through the pulmonary solangus muscle to the flexor carpi radialis. The needle remains superficial to the neurovascular bundle. Electrical stimulation can now be used to ensure proper needle tip positioning. Three key images are needed to confirm needle placement. These include the cross-sectional view of the target muscle, cross-sectional view of the vasculature adjacent to the target muscle, and length of the needle traversing to the target muscle. Once needle position is confirmed, botulinum toxin is injected into the target muscle. Finally, the needle is withdrawn and post-injection scanning may be conducted to assess for hematomas.

flexor carpi radialis muscle

needle placement

ultrasound

patient safety

complications