The importance of ulnar side approach in carpal tunnel syndrome surgical treatment – anatomic variations of the median nerve and surrounding structures

Introduction. Surgical treatment of carpal tunnel syndrome, using endoscopic as well as open procedures, is a well established treatment method with good clinical results. However, complications may occur, mostly due to congenital variation of the median nerve. The purpose of this study was to determine and describe the anatomical variations of the median nerve thenar motor branch and structures accompanying the median nerve in the carpal tunnel region. Materials and Methods. This study has been conducted on cadavers stored at the Department of Anatomy (Jagiellonian University Medical College) as well as cadavers from the Department of Forensic Medicine (Jagiellonian University Medical College). The examination took place during routine dissections or autopsies. The cadavers were examined bilaterally. Median nerve and its motor branch variations were classified according to Poisel and Lanz classifications. Results. The studied group consisted of 8 (26,7%) women and 22 men (age between 23 and 92 years), yielding a total o 60 median nerves (30 right vs. 30 left). Examination showed that 47 (78,3%) nerves were type I according to Poisel (extraligamentous), 12 (20%) were type II (subligamentous) and 1 (1,7%) was type III (transligamentous). Seventeen hands (28,3%) presented anatomical variations other than Lanz type I. Conclusions. The surgeon should keep in mind that the extraligamentous type of motor branch is the most common. Surgical incision should be made at the ulnar side of palmaris longus tendon to avoid iatrogenic injury of the thenar motor branch.