Table 3. Characteristics of 18 articles focusing on deltoid intramuscular injection.

AXN: axillary nerve; IMI: intramuscular injection

Sr. no.	Title of the article	Authors and publication year & country of publication	Study design	Number of participants & gender	Participants age group	Ethnicity of participants	Observations/Recommendations
1	The right site for IM injections	Winslow, 1996 [8]; USA	Survey	Not available	Not available	American Indian population	Of IMI sites (deltoid, vastus lateralis, dorsogluteal, ventrogluteal), only the ventrogluteal site was not associated with any adverse effects
2	Appropriate site for intramuscular injection in the deltoid muscle evaluated in 35 cadaverous arms	Nakatani et al., 2000 [9]; Japan	Cadaveric study	35	Not available	Asian population	AXN is frequently positioned 5 cm below the midpoint of lateral border of acromion; therefore, this site is unsuitable for IMI due to risk of injury to this nerve
3	The deltoid intramuscular injection site in the adult. Current practice among general practitioners and practice nurses	McGarvey and Hooper, 2005 [10]; Ireland	Public survey	Not available	Adults	White population	Injury to structures underneath the deltoid muscle can be avoided using appropriate needle lengths. Current IMI techniques at the deltoid site are deficient in many respects. Both general practitioners and practice nurses have a poor understanding of structures are at risk from IMI in the deltoid region
4	The problem of using deltoid muscle for intramuscular injection	Fujimoto, 2007 [11]; Japan	Cadaveric study	14	Not available	Asian population	The deltoid muscle is not necessarily safe or appropriate for IMI due to the possibility of AXN injury; instead, the ventrogluteal site is the first choice
5	Iatrogenic axillary neuropathy after intramuscular injection of the deltoid muscle	Davidson et al., 2007 [12]; USA	Case report	Male	26 years old	American Indian population	Deltoid IMI may result in direct mechanical trauma to the anterior branch of the AXN resulting in axillary mononeuropathy with axonal loss
6	Deltoid contracture: a case with multiple muscle contractures	Chen et al., 2008 [13]; Taiwan	Case report	Not available	Not available	Asian population	The case-patient experienced muscular contracture induced by needle injection, regardless of age, medication, and injection site
7	An evidence-based protocol for the prevention of upper arm injury related to vaccine administration (UAIRVA)	Cook, 2011 [14]; Australia	Cadaveric study	Not available	Adults > 65 years	White population	The midpoint of the deltoid muscle, defined as the middle point between the acromion and the deltoid tuberosity with the arm abducted to 60°, is a safe site for IMI
8	Post-vaccination frozen shoulder syndrome. Report of three cases	Degreef and Debeer, 2012 [15]; Belgium	Case report	Three	Not available	White population	Frozen shoulder syndrome can be a severe manifestation of vaccination-related shoulder dysfunction
9	Teaching best evidence: Deltoid intramuscular injection technique	Davidson and Rourke, 2013 [16]; Canada	Case report	Three	Not available	White population	The “axillary triangle method” was proposed. Three modifications should be urgently implemented in nursing training programs: Nursing students must be taught about structures at risk with IMIs. Nursing students should measure their own fingers to decide a 4-cm range to use for landmarking the deltoid site. Nursing students must be educated to choose needle length based on the client’s body weight
10	Influence of skin-to-muscle and muscle-to-bone thickness on depth of needle penetration in adults at the deltoid intramuscular injection site	Shankar et al., 2014 [17]; India	Analytical cross-sectional study	200 (100 male and 100 female)	Adult age group	Asian population	Over-penetration of deltoid IMI is more prevalent compared with under-penetration; thus, modification of technique of IMI is recommended based on the individual patient’s body type
11	Best vaccination practice and medically attended injection site events following deltoid intramuscular injection	Cook, 2015 [18]; Australia	Review study	Not available	Not available	White population	Best practice recommendations are proposed: Selection of a “safe” site for injection. Individualizing needle length for muscle penetration. Using a standardized injection technique and skin preparation before injection
12	Risk of bursitis and other injuries and dysfunctions of the shoulder following vaccinations	Martín et al., 2017 [19]; Spain	Review study	Not available	Adults	White population	Subdeltoid or subacromial bursitis and other shoulder lesions are more likely to result from a poor injection technique, including site, angle, needle size, and failure to consider patient’s characteristic (i.e., sex, body weight, and physical constitution)
13	Establishing a new appropriate intramuscular injection site in the deltoid muscle	Nakajima et al., 2017 [1]; Japan	Prospective study	30 (15 male, 15 female)	Age > 17 years	Asian population	A perpendicular/vertical line extending from the midpoint of lateral border of acromion and intersecting with another line that connects the upper ends of the anterior axillary line and the posterior axillary line is the intersection point proposed as the safe site for IMI
14	Upper limb nerve injuries caused by intramuscular injection or routine venipuncture	Kim et al., 2017 [20]; Korea	Review study	Not available	Not available	Asian population	The recommended injection site is the midpoint of the deltoid muscle (the densest part of the muscle) or approximately 3–5 cm below the lower edge of the acromion midway between acromion and deltoid tuberosity
15	Efficacy and safety in intramuscular injection techniques using ultrasonographic data	Tanioka et al. 2018 [21]; Japan	USG-based study	136	Not available	Asian population	Use of a 23-G 25-mm injection needle is proposed in the case of a deltoid IMI site, in the absence of notable obesity
16	Shoulder injury related to vaccine administration and other injection site events	Bancsi et al., 2019 [22]; USA	Review study	Not available	Not available	White population	The proposed general guidelines to identify the upper border of the injection site by placing two or three fingers across the deltoid muscle below the acromion process
17	Intramuscular injections	Polania Gutierrez and Munakomi, 2021 [23]	Book chapter	Not applicable	Not applicable	Not applicable	Use these selection techniques for deltoid IMI: Site: 2.5–5 cm below the acromion process; needle length: 16–32 mm (children), 25–38 mm (adults); Drug volume: 2 mL or less
18	Statistical estimation of deltoid subcutaneous fat pad thickness: implications for needle length for vaccination	Sebro 2022 [24]; USA	Retrospective cohort study	386	The age range was 19 to 93	White population	Per the current Centers for Disease Control and Prevention guidelines, deltoid IMI may result in subcutaneous injection and thereby reducing the vaccine efficacy in females and overweight persons