Abstract
Purpose. Injecting triamcinolone acetonide (TA) into a keloid is physically challenging due to the density of keloids. The purpose was to investigate the effects of various syringe and needle combinations on the injection force to determine the most ergonomic combination. Materials and Methods. A load cell was used to generate and measure the injection force. Phase 1: the injection force of 5 common syringes was measured by injecting water into air. The syringe that required the lowest injection force was evaluated with various needle gauges (25, 27, and 30 G) and lengths (16, 25, and 38 mm) by injecting TA (40 mg/mL) into air. The needle-syringe combination with the lowest injection force (CLIF) was deemed the most ergonomic combination. Phase 2: comparisons between the CLIF and a standard combination (SC) were performed by injecting TA into air and tap water into a keloid specimen. Intraclass Correlation Coefficient (ICC) and independent t-test were used. Results. Increasing the syringe caliber, injection speed, and needle gauge and length significantly increased the injection force (p value < 0.001). The SC required a maximum force of 40.0 N to inject water into keloid, compared to 25.0 N for the CLIF. Injecting TA into keloid using the SC would require an injection force that was 103.5% of the maximum force female thumbs could exert compared to 64.8% for the CLIF. ICC values were greater than 0.4. Conclusions. The 1 mL polycarbonate syringe with a 25 G, 16 mm needle (CLIF) was the most ergonomic combination. The SC required a substantial injection force, which may represent a physical challenge for female thumbs.
Highlights
A keloid scar represents an overly aggressive response to wound healing
High needle gauges are recommended for managing keloids because they inflict less pain [3, 7]
25 G, 16 mm needles were attached to the syringes to create a constant and reproducible flow resistance in order to accentuate the differences between the syringes
Summary
A keloid scar represents an overly aggressive response to wound healing. It is characterized by the presence of large, dense, and broad collagen fibers arranged in nodular formations [1]. On examination, it is seen as an elevated fibrous scar that extends beyond the original injury site, which does not regress with time. It is seen as an elevated fibrous scar that extends beyond the original injury site, which does not regress with time It can be accompanied by itchiness, pain, restricted mobility, and disfiguring dermatoses. Injecting into the lesion is often difficult because a substantial amount of injection pressure is required to deliver the medication into the dense keloid
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