Arm or Leg? The best site for injections in pediatric patients

Infants, toddlers, children, and even adults receive injections for preventive health and illness. The current rule of thumb for the site of injections for children is that for those of two years of age and younger to administer injections in their anterolateral thigh since the deltoid area is still maturing and involved in the brachial plexus development (1). After three years of age, there may be a transition to administering injections in the deltoid area. For adults and children of the appropriate age, it is much easier to roll up your sleeve than drop your pants for an injection. However, the anterolateral thigh may remain the best option and site for injections even for those older than two years of age.

Pain after injection is the most frequent complaint when using the deltoid injection site (2). The pain response in infants may be quantified by monitoring heart rate, blood pressure, and breathing changes and has been noted to be similar for infants with injections in the deltoid and vastus lateralis muscle group (3). Due to the extent of their nervous system development, their perception and processing of painful stimuli may be more dull than acute. However, it was observed that the duration of crying in pediatric patients was statistically shorter with injections in the vastus lateralis compared to the deltoid muscle (3). Because of the function of maintaining our upright position, the thigh has a much larger muscle mass compared to the arm and a greater number of motor neurons compared to somatic pain-perceiving neurons. In adults, the thickness of the deltoid muscle ranges between 0.15–1.40 cm depending on which area of the muscle you are measuring (4), compared to around 2.41 cm mean thickness of the vastus lateralis (anterolateral thigh) muscle in adults (5). A greater muscle mass for intramuscular injections optimizes the immunogenicity of vaccines (6). The larger muscle mass may also produce a buffering effect reducing the level of somatic nerve pain. Additionally considering function, the thigh has gross motor function compared to the arm and hand, which have fine motor activity.

Specific information has been reported with the acellular Diphtheria-Tetanus-Pertussis (DPT) vaccination comparing pain in the deltoid vs. vastus lateralis muscle groups (3, 7, 8). In multiple studies in children between one and six years of age, less pain was noted with injections given in the thigh over the deltoid. For those 4 to 6 years of age, the fifth DPT dose produced less local reaction when given in the thigh vs. the deltoid region. Although research has been conducted to show that antibody responses to the DPT vaccine do not differ when administered over the deltoid vs. the anterolateral thigh, it has been reported that the DTP-containing vaccinations are better tolerated when administered at the anterolateral thigh and produce fewer local reactions (9).

In the early months of life, the vastus lateralis is recommended as the injection site since the deltoid muscle mass is insufficient for injections and may also cause nerve damage (10). Compared to the vastus lateralis, the deltoid muscle contains many nearby blood vessels and nerves. This increases the risk of intramuscular injections at this site causing nerve damage. Comparatively, the vastus lateralis muscle is free of major blood vessels and nerves which reduces the potential for damage when used as the injection site. the size of the muscle and nerve density at the injection site are important factors for the perception of pain and discomfort (3). This would carry over for this being the recommended site for injections in young children and the preferred site for any injection at any age. Muscle mass has been shown to deteriorate with age, thus, this may be another important consideration for injections in the anterior lateral thigh for the elderly population (11).

Considering the potential for nerve damage, injury, and adverse reactions, the anterolateral thigh should be considered as a preferred site for vaccinations and injections for all aged individuals.

Author contributions

KS: Formal analysis, Writing – original draft. MS: Supervision, Writing – review & editing.

Funding

The author(s) declare that no financial support was received for the research, authorship, and/or publication of this article.

Conflict of interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Publisher's note

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.

References

1. Ask the experts: administering vaccines. Immunize.org. (2010). Available at: https://www.immunize.org/askexperts/administering-vaccines.asp

2. Rodger MA, King L. Drawing up and administering intramuscular injections: a review of the literature. J Adv Nurs. (2000) 31(3):574–82. doi: 10.1046/j.1365-2648.2000.01312.x

PubMed Abstract | Crossref Full Text | Google Scholar

3. Celebioglu A, Balci Akpinar R, Tezel A. The pain response of infants in Turkey to vaccination in different injection sites. Appl Nurs Res. (2010) 23(2):101–5. Available at: https://www.sciencedirect.com/science/article/pii/S0897189708000359 (Cited June 25 2021). doi: 10.1016/j.apnr.2008.03.003

PubMed Abstract | Crossref Full Text | Google Scholar

4. Kim YG, Chung YH, Ahn HJ, Jeon A, Kim YS, Hwang K, et al. Thickness of the deltoid muscle and location of the anterior branch of the axillary nerve and the posterior circumflex humeral artery for deltoid injections. BioMed Res Int. (2022) 2022:e1784572. doi: 10.1155/2022/1784572

Crossref Full Text | Google Scholar

5. Rodrigues P, Trajano GS, Wharton L, Minett GM. Muscle temperature kinetics and thermoregulatory responses to 42 °C hot-water immersion in healthy males and females. Eur J Appl Physiol. (2020) 120(12):2611–24. doi: 10.1007/s00421-020-04482-7

PubMed Abstract | Crossref Full Text | Google Scholar

6. Zuckerman JN. The importance of injecting vaccines into muscle. BMJ. (2000) 321(7271):1237–8. doi: 10.1136/bmj.321.7271.1237

PubMed Abstract | Crossref Full Text | Google Scholar

7. Jackson LA, Peterson D, Nelson JC, Marcy SM, Naleway AL, Nordin JD, et al. Vaccination site and risk of local reactions in children 1 through 6 years of age. Pediatrics. (2013) 131(2):283–9. doi: 10.1542/peds.2012-2617

PubMed Abstract | Crossref Full Text | Google Scholar

8. O’Connor A. Thigh beats arm for childhood vaccine. Well. (2013). Available at: https://archive.nytimes.com/well.blogs.nytimes.com/2013/01/15/thigh-beats-arm-for-childhood-vaccine/ (Cited October 16, 2023).

9. Scheifele D, Bjornson G, Barreto L, Meekison W, Guasparini R. Controlled trial of haemophilus influenzae type B diphtheria toxoid conjugate combined with diphtheria, tetanus and pertussis vaccines, in 18-month-old children, including comparison of arm versus thigh injection. Vaccine. (1992) 10(7):455–60. doi: 10.1016/0264-410x(92)90394-y

PubMed Abstract | Crossref Full Text | Google Scholar

10. Drehobl P. Quadriceps contracture. AJN. (1980) 80(9):1650. Available at: https://journals.lww.com/ajnonline/citation/1980/09000/quadriceps_contracture.38.aspx (Cited October 16, 2023).6905669

PubMed Abstract | Google Scholar

11. Wilkinson DJ, Piasecki M, Atherton PJ. The age-related loss of skeletal muscle mass and function: measurement and physiology of muscle fibre atrophy and muscle fibre loss in humans. Ageing Res Rev. (2018) 47(47):123–32. doi: 10.1016/j.arr.2018.07.005

PubMed Abstract | Crossref Full Text | Google Scholar