Could an injection administered 2 inches medial and above the antecubital fossa in the deltoid area cause nerve damage, specifically to the musculocutaneous nerve or a branch of the radial nerve?

Injection Site Assessment: Risk of Nerve Injury

An injection administered 2 inches medial and above the antecubital fossa is NOT in the deltoid area and carries significant risk of injuring the lateral antebrachial cutaneous nerve (terminal branch of the musculocutaneous nerve), not the radial nerve. 1

Anatomical Clarification

Your described injection site is anatomically inconsistent with proper deltoid injection technique:

• The deltoid muscle is located in the upper arm, specifically recommended for intramuscular injections in adults as the preferred site 2, 3
• An injection "2 inches medial and above the antecubital fossa" places the needle in the cubital fossa region, not the deltoid 1, 4
• This location is near the biceps brachii tendon and the area where the lateral antebrachial cutaneous nerve (LACN) emerges 1

Nerve at Risk: Musculocutaneous Nerve Branch

The lateral antebrachial cutaneous nerve (LACN), which is the terminal sensory branch of the musculocutaneous nerve, is the structure most at risk in this location:

• The LACN consistently emerges from the lateral margin of the biceps brachii tendon and pierces the deep fascia distal to the interepicondylar line in 84.4% of cases, at mean distances of 1.8 ± 1.1 cm in males and 1.2 ± 0.9 cm in females 1
• At the level of the interepicondylar line, the LACN is located medial to the lateral epicondyle by approximately 5.9 ± 1.1 cm in males and 5.2 ± 0.9 cm in females 1
• The LACN runs medially within 1 cm of the cephalic vein at the interepicondylar line level in 78.7% of cases, and in some specimens lies directly beneath the cephalic vein 1

Radial Nerve Injury Risk

While radial nerve injury from injections has been documented, it typically occurs from:

• Injections into the lateral aspect of the upper arm (actual deltoid region), not the cubital fossa 5, 6
• Four cases of radial nerve palsy following intramuscular injections into the arm have been reported, with recovery occurring in all cases 5
• Radial nerve palsy from injections is considered an avoidable injury with proper training 6

Proper Deltoid Injection Technique

To avoid nerve injury, proper deltoid injections should be administered:

• At a 90-degree angle into the deltoid muscle of the upper arm, which is located in the shoulder region, not near the antecubital fossa 2, 3
• Using a 1 to 1½ inch, 22-25 gauge needle for adults 2, 3
• The needle must be long enough to reach muscle mass but not so long as to involve underlying nerves, blood vessels, or bone 2
• Injectable medications should be administered where the likelihood of local, neural, vascular, or tissue injury is limited 2

Critical Pitfall

The location you describe (2 inches medial and above the antecubital fossa) is NOT an appropriate site for intramuscular injection and places the patient at risk for:

• Lateral antebrachial cutaneous nerve injury (musculocutaneous nerve branch) 1
• Potential vascular injury given proximity to the cephalic vein and other cubital fossa vessels 1, 4
• The medial cutaneous nerve of the forearm also traverses this region and can be injured during procedures in the cubital fossa 4