The angular course of the median nerve in the distal forearm and its anatomical importance in preventing nerve injury in a modern era of carpal tunnel release

© AANS, 2017. OBJECTIVE: A thorough understanding of anatomy is critical for successful carpal tunnel release. Several texts depict the median nerve (MN) as taking a course parallel to the long axis of the forearm (LAF). The authors report on their attempt to formally assess the course of the MN as it travels to the carpal tunnel in the distal wrist and discuss its potential clinical significance. METHODS: The width of the wrist, the distance from the radial wrist to the MN, and the distance from the distal volar wrist crease to the point where the MN emerges between the flexor carpi radialis (FCR) tendon and the flexor digitorum superficialis (FDS) tendons were recorded during cadaveric dissection of 76 wrist specimens. The presence or absence of palmaris longus was documented. Finally, the angles between the MN and FCR tendon and between the MN and the LAF were measured using ImageJ. RESULTS: The relative position of the MN at the distal wrist crease, as determined by the ratio of the distance from the MN to the radial wrist divided by wrist width, revealed a mean value of 0.48, indicating that the nerve was usually located just radial to midline. The mean distance between the distal wrist crease and the MN\u27s emergence was 34.6 mm. The mean angle between the MN and the FCR tendon was 14.1°. The angle between the MN and the LAF had a mean value of 8.8° (range 0.0°-32.2°). The nerve was parallel to the LAF in only 10.7% of the studied wrists. Palmaris longus was absent in 14 (18.4%) of the 76 wrists. CONCLUSIONS: The MN takes an angular approach to the carpal tunnel in the distal wrist in the vast majority of cases. This newly described finding will be useful to both clinicians and anatomists

A radiologic and anatomic assessment of injectate spread following transmuscular quadratus lumborum block in cadavers

© 2016 The Association of Anaesthetists of Great Britain and Ireland We performed bilateral transmuscular quadratus lumborum blocks in six cadavers using iodinated contrast and methylene blue. Computed tomography imaging was performed in four cadavers and anatomical dissection was completed in five. This demonstrated spread to the lumbar paravertebral space in 63% of specimens, laterally to the transversus abdominis muscle in 50% and caudally to the anterior superior iliac spine in 63% of specimens. There was no radiographic evidence of spread to the thoracic paravertebral space. Anatomical dissection revealed dye staining of the upper branches of the lumbar plexus and the psoas major muscle in 70% of specimens. Further clinical studies are required to confirm if the quadratus lumborum block might be a suitable alternative to lumbar plexus block