Analysis of Mechanoreceptors and Free Nerve Endings of the Transverse Carpal Ligament

Background: The treatment of carpal tunnel syndrome (CTS) by sectioning the transverse carpal ligament (TCL) is not exempt from complications. Some nerve branches may be damaged by the incision. The aim of this study is to identify and map the TCL nerve endings, serving as a guide for sectioning this structure in a zone with less nerve ending density. Methods: Ten TCLs were obtained from fresh frozen cadavers. The TCLs were measured, divided into 3 equal bands (radial, central, and ulnar), and submitted to cryostat sectioning. The sections were subjected to immunofluorescence with the protein gene product (PGP) 9.5 and confocal microscopy analysis. Results: All the specimens contained type I and type IV mechanoreceptors. Neural elements occupied 0.695 ± 0.056% of the ligament area. The density of the neural elements was greater in the radial, followed by the ulnar and central bands, with 0.730 ± 0.083%, 0.686 ± 0.009%, and 0.669 ± 0.031%, respectively. Conclusion: The present findings suggest that the region with the least potential for neural element injury during TCL release is the central third near the transition with the ulnar third. When performed distally to proximally with a slight inclination from the radial to the ulnar, this release compromises the lowest nerve element density. Topographically, the proximal limit of the release is the distal wrist crease, while the distal limit is the intersection of Kaplan cardinal line and the axis of the third webspace.

Thenar and Hypothenar Muscle Coverage on the Transverse Carpal Ligament

Background The purpose of the study was to examine the coverage of thenar and hypothenar muscles on the transverse carpal ligament (TCL) in the radioulnar direction through in vivo ultrasound imaging of the carpal tunnel. We hypothesized that the TCL distance covered by the thenar muscle would be greater than that by the hypothenar muscle, and that total muscle coverage on the TCL would be greater than the TCL-alone region. Methods Ultrasound videos of human wrist were collected on 20 healthy subjects. Automated algorithms were used to extract the distal cross-sectional image of the trapezium-hamate level. Manual tracing of the anatomical features was conducted. Results Thenar muscles covered a significantly larger distance (11.9 ± 1.8 mm) as compared with hypothenar muscles (1.7 ± 0.8 mm) (p < 0.001). The TCL covered by thenar and hypothenar muscles was greater than the TCL-alone length (p < 0.001). The thenar and hypothenar muscle coverage on the TCL, as normalized to the total TCL length, was 61.0 ± 7.5%. Conclusions More than 50% of the TCL at the distal carpal tunnel is covered by thenar and hypothenar muscles. Knowledge of muscular attachments to the TCL improves our understanding of carpal tunnel syndrome etiology and can guide carpal tunnel release surgery.

Carpal Arch Changes in Response to Thenar Muscle Loading

This study investigated the biomechanical effects of thenar muscles (abductor pollicis brevis, APB; superficial head of flexor pollicis brevis, sFPB; opponens pollicis, OPP) on the transverse carpal ligament formed carpal arch under force application by individual or combined muscles (APB, sFPB, OPP, APB-sFPB, sFPB-OPP, APB-OPP, and APB-sFPB-OPP). In ten cadaveric hands, thenar muscles were loaded under 15% of their respective maximal force capacity, and ultrasound images of the cross section of the distal carpal tunnel were collected for morphometric analyses of the carpal arch. The carpal arch height and area were significantly dependent on the loading condition (p &lt; 0.01), muscle combination (p &lt; 0.05), and their interaction (p &lt; 0.01). The changes to arch height and area were significantly dependent on the muscle combinations (p = 0.001 and p &lt; 0.001, respectively). The arch height and area increased under the loading combinations of APB, OPP, APB-sFPB, APB-OPP or APB-sFPB-OPP (p &lt; 0.05), but not under the combinations of sFPB (p = 0.893) or sFPB-OPP (p = 0.338). The carpal arch change under the APB-sFPB-OPP or APB-OPP loading was greater than that under the loading of APB-sFPB (p &lt; 0.001). This study demonstrated that thenar muscle forces exert biomechanical effects on the transverse carpal ligament to increase carpal arch height and area, and these increases were different for individual muscles and their combinations.

Surgical Treatment of Carpal Tunnel Syndrome and Lymphedema in Advanced-Stage Upper Extremity Lymphedema

Background Recent advances in supermicrosurgery have evolved to treat lymphedema surgically. For patients with carpal tunnel syndrome (CTS) and advanced-stage lymphedema, lymphovenous anastomosis (LVA) may effectively improve lymphedema after carpal tunnel release in patients with CTS and advanced stage lymphedema. However, no studies have reported simultaneous carpal tunnel release and LVA surgeries for patients with CTS and advanced-stage lymphedema.Case Presentation A 60-year-old female with carpal tunnel syndrome and International Society of Lymphology late stage 2 right upper extremity lymphedema following right mastectomy and axillary lymph node dissection and adjuvant chemoradiotherapy for treating breast cancer was admitted to our lymphedema clinic. She developed carpal tunnel syndrome four years after breast cancer surgery. She underwent release of the transverse carpal ligament, followed by four lymphovenous anastomoses at the wrist, forearm, and antecubital area. After two simultaneous surgeries, she had less neuropathic pain and volume reduction in her hand.Conclusion The authors recommend simultaneous LVA and release of the transverse carpal ligament as the first treatment option for patients with advanced-stage lymphedema and concurrent CTS.

Palmar Musculature: Does It Affect the Development of Carpal Tunnel Syndrome? A Pilot Study

Background The etiology of carpal tunnel syndrome (CTS) is multifactorial. Static mechanical characteristics of CTS have been described, but dynamic (muscular) parameters remain obscure. We believe that musculature overlying the transverse carpal ligament may have an effect on carpal tunnel pressure and may explain the prevalence of CTS in manual workers. Questions/Purposes To utilize magnetic resonance imaging (MRI) imaging to estimate the amount of muscle crossing the area of the carpal tunnel and to compare these MRI measurements in patients with and without documented CTS. Methods A case–control study of wrist MRI scans between January 1, 2018, and December 1, 2019, was performed. Patients with a diagnosis of CTS were matched by age and gender with controls without a diagnosis of CTS. Axial MRI cuts at the level of the hook of the hamate were used to measure the thenar and hypothenar muscle depth overlying the carpal tunnel. Muscle depth was quantified in millimeters at three points: midcapitate, capitate–hamate border, capitate–trapezoid border. Average depth was calculated by dividing the cross-sectional area (CSA) by the transverse carpal ligament width. Statistical analysis included Student's t-test, chi-square test, and Pearson's correlation coefficient calculation. Results A total of 21 cases and 21 controls met the inclusion criteria for the study. There were no significant differences in demographics between case and control groups. The location and depth of the musculature crossing the carpal tunnel were highly variable in all areas evaluated. A significantly positive correlation was found between proximal median nerve CSA and muscle depth in the capitate–hamate area (correlation coefficient = 0.375; p = 0.014). CSA was not significantly associated with chart documented CTS. Conclusions We found large variability in our measurements. This likely reflects true anatomical variation. The significance of our findings depends on the location of the muscles and the line of pull and their effect on the mechanics of the transverse carpal ligament. Future research will focus on refining measurement methodology and understanding the mechanical effect of the muscular structure and insertions on carpal tunnel pressure. Level of Evidence This is a Level 3, case–control study.

A New Palmo-Shoulder Compression Association

Carpal tunnel syndrome is a most common peripheral compression neuropathy (1). It is caused by mechanical compression of the median nerve as it traverses the carpal tunnel of the wrist. Classic signs and symptoms are numbness of the lateral three digits and weakness of the thenar muscles due to atrophy (2). Important diagnostic tests in- clude electromyography (EMG) and nerve con- duction studies. The gold standard for the surgical treatment is transection of the transverse carpal ligament.