Median nerve deformation and displacement in the carpal tunnel during index finger and thumb motion

Abstract

The purpose of this study was to investigate the deformation and displacement of the normal median nerve in the carpal tunnel during index finger and thumb motion, using ultrasound. Thirty wrists from 15 asymptomatic volunteers were evaluated. Cross-sectional images during motion from full extension to flexion of the index finger and thumb were recorded. On the initial and final frames, the median nerve, flexor pollicis longus (FPL), and index finger flexor digitorum superficialis (FDS) tendons were outlined. Coordinate data were recorded and median nerve cross-sectional area, perimeter, aspect ratio of the minimal-enclosing rectangle, and circularity in extension and flexion positions were calculated. During index finger flexion, the tendon moves volarly while the nerve moves radially. With thumb flexion, the tendon moves volarly, but the median nerve moves toward the ulnar side. In both motions, the area and perimeter of the median nerve in flexion were smaller than in extension. Thus, during index finger or thumb flexion, the median nerve in a healthy human subject shifts away from the index finger FDS and FPL tendons while being compressed between the tendons and the flexor retinaculum in the carpal tunnel. We are planning to compare these data with measurements in patients with carpal tunnel syndrome (CTS) and believe that these parameters may be useful tools for the assessment of CTS and carpal tunnel mechanics with ultrasound in the future. The carpal tunnel contains nine flexor tendons and the median nerve. These structures are surrounded by the subsynovial connective tissue (SSCT), which functions as a sliding interface among these structures. 1 The major pathological finding in carpal tunnel syndrome (CTS) is fibrosis of the SSCT, which changes the motion characteristics of the SSCT, tendon excursion, and median nerve, as noted during intraoperative inspection in cases of carpal tunnel release. 1-4 These changes may also cause elevated strain and pressure in the carpal tunnel, which ultimately can lead to CTS. 2,5 We hypothesize that due to fibrosis of the SSCT, the kinematics of the nerve and tendons in the carpal tunnel change in patients with CTS. We further hypothesize that these changes are associated with the evolution of CTS and that these changes can be monitored noninvasively by ultrasound. A first step in testing our hypotheses is to identify the normal motion pattern of the tendons and the median nerve in the carpal tunnel. These data can then be used as a baseline against which to compare CTS patients' data. If, as we hypothesize, detectable differences exist in the SSCT and tendon and nerve kinematics in patients with CTS, then these differences could be sought in individuals at risk for CTS. If our hypotheses are supported, then ultrasound could be a useful noninvasive tool to study the genesis of CTS and to monitor at risk individuals.Ultrasonography is a good imaging technique for the structures in the carpal tunnel. Several parameters within the carpal tunnel have been assess...

Ultasonographic indicators of carpal tunnel syndrome demonstrate reversibility following carpal tunnel release

“…They observed movement of approximately 1.5 mm in healthy individuals and a smaller value in patients with CTS. Van Doesburg reported transverse sliding motion of 2 mm during active middle finger movements [4], whereas Hsieh reported that a gripping action caused the median nerve to enter between the flexor digitorum superficialis and flexor pollicis longus in the hands of healthy individuals, but not in patients with CTS [8]. The present results show that finger movements produced a mean transverse sliding motion of about 6.6 mm in healthy individuals, which was significantly less in patients with CTS (4.9 mm).…”

“…In open carpal tunnel release surgery, the enlarged median nerve is recognized as a pseudoneuroma. The location and shape of the median nerve change with passive and active finger movements, and these changes can be observed in real-time with ultrasonography [2][3][4][5]. Toge et al [6] have further investigated median nerve motion in normal subjects during active flexion of each finger.…”

Geo-stress Characteristics of Schist of Erdaoya Tunnel and Physical Properties of Rock Masses

“…These deficiencies mainly include undeveloped supporting theory system of surrounding rock deformation, weak link of tunnel design and construction with geological conditions, low mechanization level of construction, and uncontrollable safety risk in complex geological conditions (Wang 2010). The mechanical properties and deformation control in the construction process of schist tunnels under complex geological environment are the frontier research topics in the field of tunnel projects (Lindenbergh et al 2005;Tsesarsky and Hatzor 2006;Van Doesburg et al 2010). Owing to schist is broken with poor quality, and B. Zhang (&) Á H. Hu Á S. Liang Á T. Niu Á Z. Guo Á G. Song Zhangjiakou Vocational and Technical College, Zhangjiakou 075000, Hebei, China e-mail: huh075@163.com shows large deformation volume and long deformation time, it is likely to be deformed significantly and even collapses in the excavation of tunnels.…”

Transverse Ultrasound Assessment of the Displacement of the Median Nerve in the Carpal Tunnel during Wrist and Finger Motion in Healthy Volunteers

“…In addition, little research has examined in detail the specific location of the median nerve as a coordinate within the carpal tunnel, although several previous studies have used ultrasonography to evaluated the directions and vectors of the median nerve during finger motion 3,4,7,8 . Demonstrating the location of the median nerve as a coordinate helps provide a more accurate understanding of nerve orientation within the carpal tunnel, such as the start and end points of nerves during wrist and finger motion.…”

“…1 Ultrasound examination setup at the wrist neutral position of the median nerve at the wrist 3 8 . During movements of the fingers or wrist, the median nerve moves longitudinally and transversely in response to the motion of the adjacent tendons that move actively in the carpal tunnel 3,7,9 . Some studies using transverse ultrasonography have demonstrated that the median nerve is displaced palmarly in active finger flexion and becomes compressed between the transverse carpal ligament and the flexor tendons in both healthy persons and patients with CTS 3 7 .…”