Please confirm that an ethics committee approval has been applied for or granted: Not relevant

Background and Aims A significant portion of patients experience posterior pain after hip surgery. Vermeylen et al. established a new approach to alleviate this pain by the development of the posterior pericapsular deep-gluteal block (PPD). Since the relatively recent development of this approach, the clinical characteristics lack further research. It is hypothesized that the volume of the injection plays a crucial role in determining the success of the block. In this cadaveric study, the spread of different volumes of dye is compared.

Methods Two fresh-frozen human specimens (specimen 821 & 823: both men, 91 and 81 years old respectively) were obtained from the human body donation program of the university and included in the study. Using ultrasound guidance, 5 ml, 10 ml, 15 ml or 20 ml of dye (10% latex, 1.5% methylene blue 10 mg/ml and 88.5% water) was injected in the targeted area. Each of the four hip regions were dissected. Dimensions of the dye spread were obtained.

Results The sciatic nerve was affected by dye above the branch of the nerve going to the quadratus femoris (NQF) in two of the four injections. The injected volume of the dye doesn’t seem to matter. The sciatic nerve was only stained with the injection of 20 ml and 5 ml of dye. Following PPD injection, none of the hip regions showed staining of the NQF itself.

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Abstract EP136 Figure 1

Picture of the posterior dye spread in specimen 821 (20 ml). Dye was found right under the sciatic nerve at the level of the infrapiriform foramen. The sciatic nerve was affected above the branch which goes to the quadratus femoris. All of the posterior hip capsule was coloured

Conclusions There was an inconsistent staining of the sciatic nerve, which was unrelated to the injection volume. The effectiveness of the PPD block requires further anatomical and clinical validation.