Anatomical Relationships between Muscles Overlying Distal Transverse Carpal Ligament and Thenar Motor Branch of the Median Nerve

Abstract

BackgroundThe purpose of the current study is to investigate anatomical relationships between the muscle overlying the distal transverse carpal ligament (TCL) and the thenar motor branch of the median nerve.MethodsOf the 192 wrists that underwent open carpal tunnel release, a muscle belly overlying the TCL was observed on the distal margin of TCL in 25 wrists and ligament exposure could not be achieved without transection of it. We recorded surgical findings of these 25 wrists. The origin of the recurrent motor branch arising from the major median nerve was marked on the axial and coronal section diagrams of the wrist.ResultsThe presence of muscle overlying the TCL was seen in 25 wrists (21 patients, 13%). The locations of origin were distributed not only on the radial side but anterior or ulnar side of the major median nerve. Abnormal branches originated from the unusual side in 14 cases (56% of those with a muscle overlying the TCL): central-anterior side in eight cases, ulnar-anterior side in five cases, and ulnar side in one case. These anomalous branches were frequently associated with the muscle belly overlying the TCL in our study regardless of the origin site. The branches were prone to cut if careless midline incision along the third web space was performed. Unusual origin and aberrant pathway of the recurrent thenar motor branch were associated with the presence of a muscle overlying the TCL.ConclusionsA thorough knowledge of the standard and variant anatomy of the muscle belly and recurrent motor branch in the carpal tunnel is fundamental to prevention of complications such as muscle wasting or atrophy by iatrogenic motor branch injury during carpal tunnel release.

Supraretinacular endoscopic carpal tunnel release: A safe alternative method for treatment of carpal tunnel syndrome

“…10 The overlying muscle on the distal transverse carpal ligament has been reported as an anatomic variation and occurs in 13-36% of cases. 16,17 Jegal et al mentioned that the presence of this overlying muscle indicated that the thenar motor branch originated from not only the radial side but also the anterior or ulnar side. 17 They warned of the possibility of thenar motor branch injury during transverse carpal ligament transection.…”

“…16,17 Jegal et al mentioned that the presence of this overlying muscle indicated that the thenar motor branch originated from not only the radial side but also the anterior or ulnar side. 17 They warned of the possibility of thenar motor branch injury during transverse carpal ligament transection. 16,17 In our experience, we did not observe the thenar motor branch in the overlying muscle during separation.…”

A Preligamentous Variant of the Thenar Motor Branch of the Median Nerve

“…Among 272 subjects whose carpal tunnels were examined bilaterally, Green and Morgan 5 noted that less than one-third of subjects had a purely unilateral anomalous TMB. More recently, Jegal et al 6 assessed 192 open carpal tunnel releases, finding 25 wrists with muscle overlying the TCL—four of which were bilateral cases. Fourteen of the 25 were found to have an ulnar course of the TMB that tracked into this hypertrophic muscle overlying the TCL.…”

Assessment of the Results of Two Different Incision Techniques, Severity of the Symptoms and Functional Status in the Surgical Treatment of Carpal Tunnel Syndrome (CTS)

“…CTS is the most common pathology among the peripheral nerve lesions [1][2][3]. Nowadays, it is increasingly seen in persons who work with computers at desk [1][2][3][4][5]. CTS should be initially treated with medical and physical therapy modalities [1][2][3].…”

“…Classical medical literature suggests longitudinal incision as the standard method [1][2][3]. Various techniques have been developed aiming at minimal skin incision concerning complications and healing problems [4,5].…”