The Biomechanics and Optimization of the Needle-Syringe System for Injecting Triamcinolone Acetonide into Keloids

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.

Effect of syringe size on severity of pain during local anesthesia administration

“…The 2nd component is dependent on composition of the agent, temperature, pH, technique etc The speed of infiltration affects the pain experienced by the patient. The injection flow rate, needle make, length, and internal diameter all have an impact on plateau injection pressures . This injection pressure is required to overcome the internal resistance of the tissues.…”

“…Thus, it is not the needle which determines the pain intensity rather, the syringe geometry also affects the pain severity. Moreover, the syringe caliber significantly affected the injection force required . And 3‐mL syringe required double the force than 1‐mL syringe for the similar volume to be injected .…”

“…It is sharp and more powerful due to presence of abundant pain fibers and nerve an impact on plateau injection pressures. 12 This injection pressure is required to overcome the internal resistance of the tissues. The pressure depends on the needle caliber, for example, 27-G needle was found to be more painful than 30-G needle.…”

“…The pressure depends on the needle caliber, for example, 27-G needle was found to be more painful than 30-G needle. 12 In many of the studies, the needle sizes have been compared, the smaller bore needles resulted in less pain. [13][14][15][16] However, the effect of syringe geometry remains another factor to be kept in consideration as well.…”

Airway topicalization—Beware of the MADgic™ “bullet”

“…Measures should be instituted to minimize this potential risk, which include testing the device ex vivo to ensure integrity; using Luer Lock connections (instead of Luer Slip) to reduce the risk of disconnection; using topicalization devices with long bent stylets, which facilitate easy retrieval in the event of an accidental disconnection; and using larger caliber syringes, which generate lower injection pressures compared to smaller caliber syringes when the same force is applied to the plunger …”