Ultrasound and Anatomical Study of Accessing the Nerves in the Knee by Fascial Planes

Abstract

The fascia is an undifferentiated mesenchymal tissue related to the peripheral nerves. Both can be identified by ultrasound, which is useful when performing 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 were to determine if ultrasound is accurate for identifying the fascial planes and the paraneural space of the nerves in the knee, infiltrating them, and achieving a correct anatomical diffusion, as well as for establishing 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, University of Barcelona. Nerves of the knee were injected with colorant guided by ultrasound after they were visualized. Correct location of the nerves by ultrasound was achieved in 98.75% of the cases, 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 cases. With these results, we can conclude that high‐definition ultrasound enables location of the peripheral nerves and adjacent structures as well as the fasciae that surround them, and therefore allows performance of infiltrations in the paraneural spaces.

The Tissue Plane

“…There have now been several studies examining nerves of the upper and lower extremities and the soft tissues which surround and envelope these nerves [146][147][148][149]. These have given rise to the term 'paraneural sheath' of the sciatic nerve [146] and brachial plexus [149] respectively.…”

<p>Reflections on the Development of Fascial Tissue: Starting from Embryology</p>

“…For example, in a recent article concerning the assessment of nerves in the knee by ultrasound, the fascia was stated to derive from undifferentiated mesenchymal tissue that develops between the 22nd and 35th weeks of gestation. 3 From an embryological point of view, the fascia has a double origin and derives from both the mesodermal and ectodermal leaflets. These leaflets are, in fact, apparent within the first few weeks of development.…”