Comparison of Intraneural and Extraneural Young's Modulus Using Shear Wave Elastography

Comparison of Intraneural and Extraneural Young's Modulus Using Shear Wave Elastography in Patients Undergoing Regional Anaesthesia

The investigators would like to compare the stiffness inside and outside nerves using a special type of ultrasound imaging called shear wave elastography. Shear wave elastography is a special form of ultrasound as the pictures taken are in colour. An ultrasound machine has different ways of taking pictures of inside the body: one is by measuring the brightness of different body parts (often referred to as the B-Mode scan), the pictures taken in this way are the same as those you may have seen of unborn babies inside their mum's tummies; another way is by measuring the stiffness of different body structures which is how shear wave elastography works. The investigators hope that this new technology will help doctors to see the parts of the body that are important to them.

Shear wave elastography is a quantitative ultrasound modality increasingly used to differentiate between "hard" breast cancer masses and "soft" normal tissue. Unlike strain elastography, shear wave elastography applies a non-compressive longitudinal acoustic radiation force to underlying tissues, inducing transverse shear waves. Studies in Thiel embalmed human cadavers have shown significant differences in Young's modulus between intraneural and extraneural tissue, and ready colour differentiation between tissues.

The investigators own pilot studies have shown a 3-fold greater Young's modulus within nerve in Thiel embalmed cadavers and human volunteers. The investigators hypothesis is that shear wave elastography can differentiate between nerve and adjacent tissue in patients before nerve block for surgery. If so, this technology has the potential to reduce the incidence of complications with UGRA and encourage parallel applications such as cancer node biopsy.

Inclusion Criteria:

• All patients presenting for elective orthopaedic surgery >16 years of age.
• ASA score 1, 2 or 3.
• Capacity to provide informed consent.

Exclusion Criteria:

• Patients not undergoing ultrasound guided regional anaesthesia.
• ASA score 4 or above.
• Patients without the capacity to provide informed consent.
• Pregnant women.
• Patients currently participating in another research project or patients who have participated in a research project in the 6 months