ACLR=anterior cruciate ligament reconstruction
SS=single shot (single injection)
THJR= total hip joint replacement
TKJR=total knee joint replacement
UGRA=ultrasound-guided regional anesthesia
Out-of-plane: Block needle orientation perpendicular to the long axis (or "plane") of the ultrasound beam. Needle tip approximation is through observation of tissue displacement and/or injectate spread.
In-plane: Block needle orientation parallel to the long axis (or "plane") of the ultrasound beam. The entire needle shaft and tip may be visualised with this orientation.
Short axis imaging: Orientation of the ultrasound beam perpendicular to the long axis of the nerve. Most ultrasound guided regional anesthesia is conducted using this approach.
Long axis imaging: Orientation of the ultrasound beam parallel to the long axis of the nerve. Nerve imaging can be challenging using this approach, and therefore, it is rarely used.