From the Guidelines
Trapezius intramuscular injections are not recommended for medication administration due to the risk of serious complications and the availability of safer alternative sites. The trapezius muscle, located in the upper back and neck, is not considered a safe or appropriate site for intramuscular injections due to its proximity to critical neurovascular structures and limited muscle mass. Instead, healthcare providers should use established injection sites such as the vastus lateralis (thigh), ventrogluteal (hip), dorsogluteal (buttock), or deltoid (shoulder) muscles. These sites offer better absorption, reduced risk of injury, and more consistent medication delivery. The vastus lateralis is often preferred for its accessibility, large muscle mass, and distance from major nerves and blood vessels, as supported by studies such as 1, which notes that intramuscular injection into the anterolateral thigh (vastus lateralis) produces higher and more rapid peak plasma levels compared with injections administered intramuscularly or subcutaneously in the arm.
When administering any intramuscular injection, proper technique includes:
- Using appropriate needle length (typically 1-1.5 inches)
- Selecting the correct gauge (20-23G for most medications)
- Aspirating before injection to avoid intravascular administration
- Following aseptic technique, as recommended by guidelines such as 1 and 1. The trapezius should be avoided because accidental injection into nearby structures could cause serious complications including nerve damage, vascular injury, or inadequate medication absorption.
From the Research
Trapezius Intramuscular Injection
- The trapezius muscle is a common site for myofascial trigger points (MTrPs), which can cause chronic neck pain 2.
- Studies have shown that lidocaine injection in the intramuscular innervation zone (IZ) can effectively treat chronic neck pain caused by MTrPs in the trapezius muscle 2.
- The efficacy of lidocaine injection in the IZ has been compared to injection in the MTrPs, with results showing that IZ injection is more effective in reducing pain and improving function 2.
- Other studies have compared the effects of lidocaine injection to radial extracorporeal shock wave therapy (rESWT) for treating MTrPs in the upper trapezius muscle, with results showing that rESWT is safe and effective in reducing pain and improving muscle elasticity 3.
Techniques and Guidelines
- Intramuscular injections are a common technique used to deliver medication deep into the large muscles of the body, but unsafe injection practices can have significant impacts on patient morbidity and mortality 4.
- Guidelines for evidence-based practice of intramuscular injections have been developed to maximize the therapeutic effects of administered medication while minimizing patient injury and discomfort 4.
- The use of topical 5% lidocaine patch has been shown to be effective in relieving pain and reducing associated neck disability in patients with myofascial pain syndrome of the upper trapezius 5.
- The choice of needle size for trigger point injection in myofascial pain syndrome of the upper- and middle-trapezius muscle has been investigated, with results showing that injections with 21- or 23-gauge needles were found to be more effective in terms of health-related quality of life 6.
Key Findings
- Lidocaine injection in the IZ is a effective treatment for chronic neck pain caused by MTrPs in the trapezius muscle 2.
- rESWT is a safe and effective treatment for MTrPs in the upper trapezius muscle 3.
- Guidelines for evidence-based practice of intramuscular injections can help minimize patient injury and discomfort 4.
- Topical 5% lidocaine patch can be an effective treatment for myofascial pain syndrome of the upper trapezius 5.
- The choice of needle size can affect the efficacy of trigger point injection in myofascial pain syndrome of the upper- and middle-trapezius muscle 6.