Fascia Iliaca Blocks: A Cadaveric Study Comparing the Suprainguinal Approach to the Loss of Resistance Technique

Background Local anesthetic fascia iliaca blocks (FIB) are used for peri- and post-operative analgesia in hip fracture patients. The loss of resistance technique (LORT) and the suprainguinal approach (SIA) are two techniques commonly used. We present a pilot, first cadaveric study model that compares both techniques. Methods Methylene blue dye was injected as a local anesthetic substitute. This dye is easily visible. Both hips on each of the seven cadavers were injected with one of the two techniques used per side. Single-blinded randomization was conducted to determine the technique to be administered in each hip. Ten minutes after injection, the dissection of the femoral, obturator, and lateral femoral cutaneous nerves (LFCN) revealed the dye spread around these nerves. The SIA and the LORT were compared in their area of dye distribution using the Wilcoxon matched-pairs signed-rank test. The hips of a single cadaver were matched, since these received the injection via a different technique. Results The area of dye spread was greater in the SIA for five cadavers. Dye spread was greater following the LORT in two cadavers. However, the Wilcoxon matched-pairs signed-ranked test revealed no statistically significant difference in the area of dye spread following both techniques (p= 0.866). The SIA showed that the femoral, obturator, and LFCN were stained in six, three, and seven cadavers, respectively. The LORT resulted in five, two, and five of these nerves being stained, respectively. Conclusion This study found no statistically significant difference in terms of the area of dye spread between the SIA and the LORT. The number of nerves stained was greater following the SIA. This suggests that the SIA may lead to superior anesthetic outcomes. This conclusion is limited by the low sample size in this study. This work warrants the collection of more data through the same method to support or challenge our findings.