Ultrasound and anatomical study of accessing the nerves in the knee by fascial planes.

The fascia is an undifferentiated mesenchymal tissue related to the peripheral nerves. Both can be identified by ultrasound, which is useful to perform peripheral nerve blocks. However, there is no unanimity about the approaching point of each nerve nor is there a consensus on how to name the appropriate infiltration zone, although the paraneural zone is frequently mentioned. The aims of this study is to determine if ultrasound is accurate to identify the fascial planes and the paraneural space of the nerves in the knee, infiltrate them and achieve a correct anatomical diffusion, as well as establish access routes to avoid intraneural infiltration. The study was performed in 16 cryopreserved lower extremities of the dissection room of the Faculty of Medicine and Health Sciences. Nerves of the knee were injected with colourant guided by ultrasound after they were visualized. Correct location of the nerves by ultrasound was achieved in 98,75% of the cases, the correct visualization of the needle by ultrasound in 82,5%, the hypoechogenic image around the nerve after infiltration in 82,5% and a correct paraneural infiltration in 76,25% of the cases. With these results we can conclude that high definition ultrasound enables locating the peripheral nerves and adjacent structures as well as the fasciae that surround them and, therefore allows performing infiltrations in the paraneural spaces.