Aberrant nerve in limited open carpal tunnel release.

n s ( t c n h p fi m i e f n aberrant nerve pierced the distal margin of the transverse carpal ligament during a carpal tunnel release (CTR) through a limited open pproach. Through a small incision distal to the pillar egion, the nerve was dissected between 2 leaflets of he transverse carpal ligament. The incision was exended in the proximal direction when it became clear hat the nerve did not join the main trunk of the median erve within the distal third of the carpal canal. Coninued dissection showed an intraligamentous motor ranch of the median nerve that split from the median erve proximal to the carpal canal (Figs. 1–3). In 1977 Lanz classified variations of the median erve into 4 groups: group I, variations of the course of he motor branch; group II, accessory branches of the edian nerve at the distal carpal tunnel; group III, high ivisions of the median nerve; and group IV, accessory ranches proximal to the carpal tunnel. Not all median erve anomalies, however, fit into these categories. In ddition to the Lanz groupings the thenar motor branch an be categorized based on 3 components: (1) the rigin of the recurrent motor branch (ulnar, radial, voar); (2) the relationship of the transverse carpal ligaent to the thenar motor branch (extraligamentous, ubligamentous, transligamentous, intraligamentous); nd (3) the number of thenar motor branches. Of the ocumented anomalies, extraligamentous variants ccur most frequently (46%), followed by subligaentous (31%) and transligamentous (23%). Although Poisel found a 54% prevalence of nomalies of the median nerve, more recent studies ave found varying results. Lanz looked at 246 ands and found variations in the branch patterns of he median nerve in 29 hands (12%). Of those 29 ands 18 had accessory branches of the median nerve t the distal carpal tunnel (7%), 7 had high division f the median nerve (3%), and 4 were accessory ranches proximal to the carpal tunnel (2%). Variaions of the course of the motor branch were not ncluded in the study. Lindley et al conducted a tudy looking at all anatomic variations encountered n elective CTR and found only 5 anomalies of the edian nerve in 526 hands studied (1%). A study by tancic et al looked at 65 patients with carpal tunnel yndrome, 10 patients with a median nerve injury, nd 25 cadaver specimens; they discovered findings imilar to Poisel’s results. Of these 100 hands, 52 had nomalies. Forty of the anomalies were classified as aving variations in the course of the motor branch, ccessory branches of the median nerve at the distal arpal tunnel were found in 7 hands, high divisions f the median nerve were found in 1 hand, and 4 ands were categorized as having accessory branches roximal to the carpal tunnel. The data from the study by Tountas et al were otably different from those of Poisel. They included a urgical retrospective group, in which 30 hands of 535 6%) has anomalies; a surgical prospective group conaining 40 anomalies out of 286 hands (14%); and a adaver group in which 21 of 92 hands had median erve anomalies (22%). Tountas found that 96% of the ands were considered normal, whereas Poisel reorted only 46%. In the study by Poisel, 54% of cases t into Lanz group I, variations of the course of the otor branch; only 1% of cases in the Tountas study fit nto group I. Tountas was unable to explain the considrable difference in anomalies found and called for urther studies.