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OP050 Ultrasound-guided subpectineal approach of the obturator nerve: An anatomical study
  1. Hipólito Labandeyra1,2 and
  2. Xavier Sala-Blanch1,3
  1. 1Laboratory of Surgical Neuroanatomy (LSNA). Human Anatomy and Embryology Unit , Faculty of Medicine and Health Sciences, Universitat de Barcelona, Barcelona, Spain
  2. 2Anesthesiology, Parc Sanitari Sant Joan De Déu, Sant Boi de Llobregat, Spain
  3. 3Anesthesiology, Hospital Clínic de Barcelona, Barcelona, Spain


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Background and Aims Ultrasound-guided obturator nerve (ON) block was initially described by Helayel, utilizing adductor muscles as anatomical landmarks. However, more proximal subpectineal approaches to ON block lack clear ultrasound references. The objective of our study is to describe the subpectineal ultrasound-guided technique, employing precise ultrasound references for accurate localization of the nerve.

Methods We conducted an anatomical study on eight cadaveric models (16 blocks). Using ultrasound and a linear probe positioned sagittally over the pubis, we performed a medial-to-lateral sweep to identify the complete obturator foramen. On the lateral side of the obturator foramen, the neurovascular bundle was located beneath the superior pubic ramus and above the obturator external muscle, covered by the pectineus muscle (figure 1). An out-of-plane approach (lateral to medial) was performed using an 80 mm needle, targeting the region adjacent to the obturator membrane (figure 1 – gray circle). A 5 ml solution (0.02% methylene blue) was injected. Anatomical dissection of the samples was conducted to assess the involvement of the ON at different levels (intrapelvic, common trunk, anterior and posterior branches of the ON).

Results Anatomical dissection revealed methylene blue staining of the ON at the intrapelvic level in nine cases (56%), as well as in the obturator foramen (common trunk) and the anterior and posterior branches in all cases (16, 100%) (figure 2).

Abstract OP050 Figure 1

Subpectineal approach for ultrasound-guided obturator nerve block: A descriptive technique

Abstract OP050 Figure 2

Visualization of the stained obturator nerve following ultrasound-guided subpectineal obturator nerve block with 5 ml of solution. (Add.- Adductor; FA- Femoral Artery; ON- Obturator Nerve; AB- Anterior branch of obturator nerve; PB-Posterior Branch of obturator nerve)

Conclusions Consistently, the ON displayed staining when employing a subpectineal approach, located caudal to the superior pubic ramus and cranial to the obturator external muscle, in close proximity to the obturator membrane.

  • Ultrasound-guided regional anesthesia
  • Subpectineal approach of the obturator nerve
  • Obturator nerve
  • Anatomical study

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