Hum Vaccin Immunother. 2020; 16[1]: 189–196. Yukari Nakajima,a,* Taiga
Fujii,b,* Kanae Mukai,a Asami Ishida,c
Moeka Kato,c Mao Takahashi,c Mihiro
Tsuda,c Nanami Hashiba,c Namiko Mori,c
Ayaka Yamanaka,c Noriyuki Ozaki,d and Toshio
Nakatania
ABSTRACT
The anatomical safety of intramuscular injections at the deltoid and ventrogluteal sites has been investigated; however, the anatomical relationship between intramuscular injection sites in the thigh and major blood vessels and nerves remains unclear. We aimed to compare intramuscular injection sites in the rectus femoris and vastus lateralis with those at the deltoid and ventrogluteal sites and identify safe intramuscular injection sites in the thigh. Twenty-seven young adult volunteers were recruited, and the thicknesses of subcutaneous tissue and muscle as well as the number of blood vessels present were evaluated at two sites on the deltoid, ventrogluteal, and thigh using ultrasound equipment. The right thighs of 24 cadavers were used, and the thickness of muscle, number of blood vessels or nerves present, and the distance between each examined site and major blood vessels or nerves were evaluated in the rectus femoris and vastus lateralis. A major blood vessel was observed in the middle of the rectus femoris in young adults. In cadavers, the descending branch of the lateral circumflex femoral artery and muscle branch of the femoral nerves to the vastus lateralis were observed at the middle point, distal two-thirds point, and middle point between the middle and distal two-thirds points of the rectus femoris, but not at the middle of the vastus lateralis. The middle of the vastus lateralis is an appropriate site for intramuscular injections because of the low risk of vascular or nerve damage. The present results support good practices for site selection for intramuscular injections.
KEYWORDS: Intramuscular injections, thigh, safety, femoral nerve, femoral artery
Introduction
Intramuscular [IM] injections are a technique used to deliver vaccines, hormonal agents, antibiotics, and high viscosity medication deep into the muscles of patients.1 When considering IM injection sites, a clinician needs to select a site that is [1] a safe distance from nerves, large blood vessels, and bones, [2] free from injury, abscesses, tenderness, necrosis, abrasions, and other pathologies, and [3] sufficiently large to accommodate the volume of medication to be administered.2 Based on these three conditions, deltoid, ventrogluteal, and thigh sites are considered to be safe and, thus, commonly used for IM injections.
The deltoid site has been used in clinical settings and is preferred in Japan because it is easily accessible for clinicians and also for patients to expose.3 Since this area has a small mass, clinicians may only administer small amounts of medication. Although the site located at a one to three finger breadth below the acromion is generally recommended for an IM injection at the deltoid site,4,5 we previously reported that the site at a three finger breadth [approximately 5 cm] below the acromion was not acceptable for IM injections because it is close to the axillary nerve and posterior circumflex humeral artery [PCHA].6,7 Therefore, we proposed the intersection between the anteroposterior axillary line [the line between the upper end of the anterior axillary line and upper end of the posterior axillary line] and the perpendicular line from the mid-acromion as the most appropriate site for IM injections with a low risk of axillary nerve and PCHA damage [This site is shown in Figure 1 [A] in reference].8
Locations of six examined sites in young adults. A: In the deltoid muscle, three finger breadths below the mid-acromion [MA] was defined as [a], and the point on the anteroposterior axillary line [b] was defined as that located at the intersection of the perpendicular line from MA and the horizontal line between the upper end of the anterior axillary line [AAL] and upper end of the posterior axillary line [PAL]. B: In the gluteus medius, the point of Clark [c] was defined as that located at the anterior one-third point between the anterior superior iliac spine [ASIS] and posterior superior iliac spine [PSIS], and the novel point on the gluteus medius [d] was defined as that located at the intersection of the horizontal line from ASIS and the perpendicular line from the middle portion of the trochanter major [TM]. C: In the rectus femoris, the middle point of the rectus femoris [e] was defined as that located at the middle point between ASIS and the center of the patella [cPa]. In the vastus lateralis, the middle point of the vastus lateralis [f] was defined as that located at the middle point between the TM and lateral epicondyle [LE].
A ventrogluteal site is the most commonly used and recommended site for IM injections in adults and children of walking age because of the large muscle mass. This site is located away from the superior and inferior gluteal arteries as well as the sciatic and superior gluteal nerves,9 and is also the least painful.2 Hochstetter10 initially suggested that this site was appropriate for IM injections. The V method is often used to identify IM injection sites in this area.1,11,12 The V method is performed as follows: when the injection site is on the left side, the palm of the right hand is placed over the greater trochanter. The index finger is placed on the anterior superior iliac spine. The middle finger is then positioned towards the iliac crest. The index and middle fingers create a V-shape, and the injection site is in the middle of the V-shape. In Japan, the point of Clark is the most popular IM injection point at the ventrogluteal site.13 This point is defined as the anterior one-third between the anterior and posterior superior iliac spines. However, the posterior superior iliac spine may be difficult to palpate when locating the point of Clark. Therefore, we previously established a novel IM injection point located at the intersection of the horizontal line from the anterior superior iliac spine and the perpendicular line from the middle portion of the trochanter major, and this novel point was shown to be as safe as the point of Clark with a low risk of damage to the superior and inferior gluteal artery as well as the sciatic and superior gluteal nerves.9,14–16
In Japan, IM injections into the thigh are rarely performed in adults because of the outbreak of quadriceps contracture among children in the 1970s. This outbreak was attributed to the repeated administration of antibiotics and antipyretics, and not to vascular or nerve damage.17 Therefore, IM injections into the thigh may be used for Japanese adults. The vastus lateralis site is generally the preferred site for young infants, particularly those not yet walking.18 Moreover, this site is often used by patients who self-administer IM injections because it is easy to access.19 The middle third of the lateral thigh between the trochanter major and the knee is an injection site in the vastus lateralis and is not in close proximity to any major blood vessels or nerves.2,20 However, limited information is currently available on blood vessels or nerves traveling in IM injection sites in the vastus lateralis. Additionally, the rectus femoris [the middle third of the rectus femoris] is no longer a recommended site because it may cause discomfort and pain.1,2,18 A previous study reported that one disadvantage of this site is that nerves and numerous blood vessels run very close to it.21 Although blood vessels and nerves traveling close to or in IM injection sites in the deltoid and ventrogluteal sites have been extensively examined,6,7,9,15 those in the vastus femoris have not.
An evidence-based approach is needed for site selection for successful IM injections and the avoidance of vascular or nerve damage. In order to identify safe IM injection sites in the thigh, the anatomical relationship between IM injection sites and major blood vessels and nerves needs to be elucidated in more detail. Therefore, in the present study, we compared IM injections in the thigh to those at the deltoid and ventrogluteal sites in young adults, observed blood vessels and nerves traveling close to or in IM injection sites in the vastus lateralis and rectus femoris in cadavers, and clarified what site in the thigh is anatomically safe for IM injections.
Materials and methods
Study design and setting
This was a cross-sectional study that was conducted at a university in Japan. It commenced on August 18, 2017 and was completed on December 12, 2018.
Subjects
Thirty healthy volunteers participated in the present study and met the following inclusion criteria: age >17 y old, no history of buttock or upper/lower limb injury/surgery or neurological or muscular diseases of the buttocks or upper/lower limbs, no allergies to the implements used in this study, and a body mass index [BMI] >17 and