Skin-to-deltoid-muscle distance at three recommended sites for intramuscular vaccination in a population with obesity: an observational study.

AIM: Worldwide, immunisation guidelines variably locate the deltoid injection site based on anatomical landmarks. This may influence the skin-to-deltoid-muscle distance and therefore the needle length required to achieve intramuscular injection. Obesity is associated with increased skin-to-deltoid-muscle distance, but it is unknown whether the injection site location chosen in individuals with obesity impacts the needle length required for intramuscular injection. The aim of the study was to estimate the differences in skin-to-deltoid-muscle distance between three different vaccine injection sites recommended by the national guidelines of the United States of America (USA), Australia and New Zealand, in obese adults. The study also explored i) the associations between skin-to-deltoid-muscle distance across the three recommended sites with sex, body mass index (BMI), and arm circumference, and ii) the proportion of participants with a skin-to-deltoid-muscle distance >20 millimetres (mm), in whom the standard 25mm needle length would not ensure deposition of vaccine within the deltoid muscle. METHOD: Non-interventional cross-sectional study in a single site, non-clinical setting in Wellington, New Zealand. Forty participants (29 females), aged ≥18 years, with obesity (BMI>30 kilograms [km]/m[[2]]). Measurements included distance from acromion to injection sites, BMI, arm circumference, and skin-to-deltoid-muscle distance measured by ultrasound at each recommended injection site. RESULTS: Mean (SD) skin-to-deltoid-muscle distances for USA, Australia and New Zealand sites were 13.96mm (4.54), 17.94mm (6.08) and 20.26mm (5.91) respectively, with a mean (95% confidence interval) for the distance between Australia minus New Zealand -2.7mm (-3.5 to -1.9), P<0.001; and USA minus New Zealand -7.6 mm (-8.5 to -6.7); P<0.001. Skin-to-deltoid-muscle distance was greater in females and was positively associated with BMI and arm circumference. The proportions with a skin-to-deltoid-muscle distance >20 mm were 45%, 40% and 15% for the New Zealand, Australia and USA sites respectively. However, the sample size was relatively small, limiting interpretation in specific sub-groups. CONCLUSION: There were marked differences in the skin-to-deltoid-muscle distance between the three recommended injection sites studied. When choosing the required needle length to achieve intramuscular vaccination in obese vaccine recipients, consideration needs to be given to the injection site location, sex, BMI and/or arm circumference, as these factors all influence the skin-to-deltoid-muscle distance. A standard needle length of 25mm may be insufficient to ensure deposition of vaccine into the deltoid muscle in a substantive proportion of adults with obesity. Research is urgently required to determine anthropometric measurement cut-points that can be used to enable appropriate needle length selection to ensure intramuscular vaccination.

COVID-19 vaccination and the skin to deltoid MUSCLE distance in adults with diabetes.

Objectives: To estimate the proportion of adult diabetics with a skin to deltoid muscle distance (SDMD) of > 25 mm, representing a distance greater than the standard needle length used for intramuscular COVID-19 vaccination, and to assess whether anthropometric measurements predict ultrasound SDMD measurements. Design: Non-interventional cross-sectional study. Setting: Single site, non-clinical setting, Wellington, New Zealand. Participants: One hundred participants (50 females) aged at least 18 years diagnosis with diabetes. All participants completed the study. Main outcome measures: The proportions of participants with a SDMD > 25 mm and a SDMD > 20 mm (indicating that the needle would not have penetrated at least 5 mm into the deltoid, which is considered necessary to ensure deposition of vaccine into muscle); the relationship between anthropometric measurements (body weight, body height, body mass index (BMI), skinfold thickness, arm circumference) and SDMD measured by ultrasound. Results: The proportion (95 %CI) of participants with a SDMD > 25 mm was 6/100; 6 % (2.2 to 12.6), and the proportion with a SDMD > 20 mm was 11 % (5.6 to 18.8), of which 9/11 had a BMI ≥ 30 kg/m2 and 9/11 were female. The strongest relationships between anthropometric measurements and SDMD were with arm circumference (r = 0.76, P < 0.001) and BMI (r = 0.73, P < 0.001). Arm circumference and BMI were the best predictors of SDMD measurements with AUC for ROC curves of 0.99 and 0.94 above the 25 mm cut point, 0.97 and 0.89 above the 20 mm cut point respectively. Conclusions: The standard needle length of 25 mm is likely to be insufficient to ensure deposition of COVID-19 vaccine within the deltoid muscle in a small but important proportion of obese adults with diabetes. Arm circumference and BMI are simple measurements that could identify those that need a long needle to ensure successful intramuscular vaccine administration. Funding: Ruth Maud Ring Spencer Estate; Health Research Council of New Zealand (Independent Research Organisation).

Slipping rib syndrome.

Slipping rib syndrome (SRS) is an underdiagnosed condition that can lead to debilitating lower chest and upper abdominal pain (Am J Med Sci 2019; 357: 168). It is caused by hypermobility of the anterior ends of the costal cartilages of false ribs, allowing the eighth to tenth ribs to slip under the rib above, giving its name (Semin Pediatr Surg 2018; 27: 183). Failure to recognize this syndrome can expose patients to extensive and unnecessary investigations for unclear symptoms. Although more commonly reported in adults, SRS is a relatively uncommon but recognized cause of lower chest or upper abdomen pain in adolescence (Pediatr Anesth 2001; 11: 740). It is important for clinicians to familiarize themselves with and consider the diagnosis of SRS when assessing and managing adolescents with persistent thoracic pain. We present a case of a 14-year-old girl with unresolved thoracic pain for more than 4 years and was ultimately diagnosed with SRS.