• Guilherme Ferreira-Dos-Santos, HurdleMark-Friedrich BMBDepartment of Pain Medicine, Mayo Clinic, Jacksonville, FL, USA., Sahil Gupta, John Tran, Anne M R Agur, and Steven R Clendenen.
• Department of Physical Medicine and Rehabilitation, Central Lisbon University Hospital Center, Lisbon, Portugal; NOVA Medical School, NOVA University of Lisbon, Lisbon, Portugal.
• Pain Physician. 2021 Mar 1; 24 (2): E177-E183.

BackgroundOver the last decade, several authors have reported that percutaneous peripheral nerve stimulation (PNS) can be used to assist in verifying the position of the procedure needle tip in relation to nerve structures, and that the combined technique using both ultrasound (US) guidance and PNS may serve as a reliable method for confirmation of the correct position of the procedure needle tip. It has also been reported that, when combined with US guidance, PNS may increase the success rate of pain management interventions.ObjectivesThe aim of this technical report was to standardize an effective and easy to learn illustrated step-by-step technical approach to nerve identification during US-guided genicular nerve blocks, using percutaneous PNS as a verification instrument for procedure needle tip location.Study DesignThis technical protocol was developed based on the results of the authors' most recent cadaveric study on the innervation of the knee joint capsule. The technique was developed and tested by 4 different interventionists with different levels of expertise in US-guided procedures.SettingThe cadaveric study of the knee joint capsule innervation was performed at the laboratory of the Division of Anatomy of one institution. The technical protocol using US and PNS was later developed at the medical simulation center of a different institution.MethodsA team of anatomists from a division of anatomy of one institution performed the cadaveric study on the innervation of the knee joint capsule. A team of physicians then developed the step-by-step approach to this technical protocol at the medical simulation center of  a different institution. Finally, the illustrated step-by-step approach was tested by 4 different interventionists with different levels of expertise in US-guided procedures (1 beginner-level user; 1 intermediate-level user; 2 expert-level users), using a portable percutaneous PNS and 2 different US transducers at 2 different institutions.ResultsThis technical protocol was successfully developed based on the results of the cadaveric study on the innervation of the knee joint capsule. Additionally, it was later successfully tested by interventionists with various levels of expertise utilizing different US equipment at separate institutions.LimitationsBy combining US and nerve stimulation, this protocol requires the availability of both US equipment and necessary equipment for nerve stimulation that must all be made available in the sterile field. Another potential disadvantage is that nerve stimulation controls and the US image screen are generally located on 2 separate display panels, which could cause difficulty with visualization and simultaneous calibration for 2 individual devices.ConclusionsOur illustrated step-by-step technical protocol can be effectively and safely utilized as a reliable method of training, by which physicians with little to moderate US experience can improve their skills in accurately identifying the genicular nerves while performing US-guided examinations with the intent of executing a peripheral nerve block.

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