Dimensional changes of the carpal tunnel and median nerve during manual mobilization of the carpal bones — Anatomical study☆
Introduction
The carpal tunnel is a fibro-osseous entity bound by the scaphoid and trapezium bones on the radial side, the pisiform and hamate hook on the ulnar side and enclosed by the flexor retinaculum on the ventral side (Drake et al., 2009). The median nerve runs along tendons of the m. flexor digitorum superficialis and profundus and tendon of the m. pollicis longus through this tunnel. In this narrow passage, the median nerve is vulnerable to compression. Involvement of the median nerve at this level is known as carpal tunnel syndrome (CTS) and is the most common neuropathy of the upper limbs (Ibrahim et al., 2012; Keith et al., 2009). Its prevalence ranges between 3% and 6% of the general adult population and affects women more than men (Atroshi et al., 1999).
The space available for the median nerve in the carpal tunnel is influenced by the cross-sectional area (CSA) formed by the carpal bones and the transverse carpal ligament. The tunnel area can vary with flexion and extension of the wrist, during daily living activities (Garcia-Elias et al., 1992) and after surgical release of the carpal tunnel (Lee et al., 2005; Richman et al., 1989). These changes can be important because they may relate to the increase or decrease in CTS symptoms.
From cadaveric studies (Li et al., 2009; Li et al., 2011; Li et al., 2013), it has been observed that the dimensions of the carpal tunnel can increase when outwardly-directed forces are applied with a custom balloon device from inside the tunnel to apply controlled pressure to the carpal tunnel. This effect occurs when the carpal arch width narrows as the distance between the trapezoid and the hook of the hamate decreases, increasing the anteroposterior diameter (APD) and the circularity of the tunnel. Recently it has been shown using ultrasound in asymptomatic subjects that similar changes can also occur in vivo when applying a compressive force transverse to the carpal tunnel both with a pneumatic actuator (Marquardt et al., 2015) and manually (Bueno-Gracia et al., 2018). From these studies, it was hypothesized that these changes may assist transiently in relieving pressure around the median nerve in patients with CTS.
What is of value in contextualizing and establishing the extent to which non-invasive measurement approaches resemble the events that would occur anatomically is to perform such maneuvers in cadavers also. To our knowledge there are no studies on the effect of applying external compressive transverse forces to the carpal bones on carpal tunnel and median nerve dimensions in cadavers. Hence, the hypothesis of this study is that manual mobilization of the carpal bones can produce changes in the cross-sectional dimensions and area of the carpal tunnel and median nerve in cadavers.
Section snippets
Study design
This was a cross-sectional study designed to document and analyze the effect of manual mobilization of carpal bones on the dimensions of the carpal tunnel and median nerve at the wrist in cadaver specimens. Donations were made to the dissection laboratory of the Universitat Internacional de Catalunya. The local Ethical Committee approved the present study (reference number CBAS-2018-03). The sample size calculation was made with reference to data from a previous in vivo study (Bueno-Gracia et
Results
Reliability of tunnel and nerve with the ImageJ software was excellent. The ICC ranged from 0.98 to 0.99 for all measurements (Table 1).
The initial area of the tunnel was 186.33mm2 ± 47.44. The APD was 10.04 mm ± 2.00 and the TD 23.19 mm ± 3.12 (Table 2). The flattening ratio and circularity were 2.36 ± 0.34 and 0.72 ± 0.05, respectively. All the carpal tunnel shape descriptors were significantly modified by the mobilization of the carpal bones. The CSA increased by 5.93mm2 (p < 0.011) and the
Discussion
This study investigated the morphological changes of the carpal tunnel and median nerve during the application of manual and external forces at the wrist in cadavers. Initial values for the tunnel and median nerve were similar to other studies (Bueno-Gracia et al., 2017; Bueno-Gracia et al., 2018; Cobb et al., 1993; Hobson-Webb et al., 2008; Lange, 2013; Li et al., 2009; Pacek et al., 2010; Yazdchi et al., 2012). The results confirmed the hypotheses that pressure application to the tunnel
Conclusion
This study demonstrated that the application of a manually applied external compressive force across the wrist can increase the cross-sectional area (CSA) of the carpal tunnel and the median nerve in fresh-frozen cadavers. The carpal tunnel and median nerve became rounder, due to a reduction in the transverse diameter (TD) and an increase in the anterior-posterior diameter. This manual intervention is hypothesized to produce transient reductions in tunnel pressure which may be offered for pain
Conflict of interest
The authors certify that there are no conflicts of interest (or funding sources are explicitly declared in the paper, especially those that might pose a conflict of interest).
Financial disclosure and conflict of interest
Authors of the manuscript affirm that they have no financial affiliation (including research funding) or involvement with any commercial organization that has a direct financial interest in any matter included in this manuscript, except as disclosed in an attachment and cited in the manuscript. Any other conflict of interest (i.e., personal associations or involvement as a director, officer, or expert witness) is also disclosed in an attachment.
Acknowledgements
We express our sincere gratitude for the opportunity to make use of the materials and resources of the Body Donation from UIC-Barcelona. Body donors are fundamental for the evolution of science, both in terms of teaching and research. Thanks to these donations, the present study has been possible. We also thank Judith Pascual for their help and assistance in the laboratory.
References (32)
- et al.
Reliability of measurement of the carpal tunnel and median nerve in asymptomatic subjects with ultrasound
Musculoskelet. Sci. Pract.
(2017) - et al.
Dimensional changes of the carpal tunnel and median nerve during manual mobilization of the carpal bones
Musculoskelet. Sci. Pract.
(2018) Carpal tunnel syndrome: reconciling “demand management” with clinical need
J. Hand. Surg. (Br.)
(2000)- et al.
Anatomy of the flexor retinaculum
J. Hand. Surg. [Am.]
(1993) - et al.
The responsiveness of the Hamilton depression rating scale
J. Psychiatr. Res.
(2000) - et al.
Dynamic changes of the transverse carpal arch during flexion-extension of the wrist: effects of sectioning the transverse carpal ligament
J. Hand. Surg. Am.
(1992) - et al.
The ultrasonographic wrist-to-forearm median nerve area ratio in carpal tunnel syndrome
Clin. Neurophysiol.
(2008) - et al.
Narrowing carpal arch width to increase cross-sectional area of carpal tunnel—a cadaveric study
Clin. Biomech.
(2013) - et al.
Morphological and positional changes of the carpal arch and median nerve during wrist compression
Clin. Biomech.
(2015) - et al.
Effects of traditional cupping therapy in patients with carpal tunnel syndrome: a randomized controlled trial
J. Pain
(2009)
Carpal tunnel syndrome: morphologic changes after release of the transverse carpal ligament
J. Hand. Surg. [Am.]
Ultrasonography for diagnosing carpal tunnel syndrome: a meta-analysis of diagnostic test accuracy
Ultrasound Med. Biol.
Prevalence of carpal tunnel syndrome in a general population
JAMA
Statistical Power Analysis for the Behavioral Sciences
Anatomía de Gray Para Estudiantes
How sample size influences research outcomes
Dental Press. J. Orthod.
Cited by (6)
The cross-sectional morphology of median nerve in carpal tunnel of healthy, adult population: A systematic review and meta-analysis
2023, MorphologieCitation Excerpt :MN-CSA outlet in male, i.e., 7.74 mm2 [6.86–8.62 mm2], was higher than female, i.e., 7.30 mm2 [6.91–7.61 mm2]. Thirty-six studies have reported FR in 2189 wrists [1–5,7,9–11,14,15,18,23,34,37,40,41,46–48,51,52,58,62,64,66–68,73,74,81,83,89,95,96,99] (Table 4). The pooled estimate of FR was 2.78 [2.55–3.01].
Dimensional Changes of the Tarsal Tunnel During Foot and Ankle Positions: Anatomical Study
2020, Journal of Foot and Ankle SurgeryCitation Excerpt :In this way, the lens of the camera was kept perpendicular to the specimen during the whole procedure (27). The images were analyzed (E.B.) using ImageJ (v2.0) (27,28). The limits of the tarsal tunnel were identified by means of corporal landmarks.
Diacutaneous Fibrolysis Intervention in Patients with Mild to Moderate Carpal Tunnel Syndrome May Avoid Severe Cases in Elderly: A Randomized Controlled Trial
2022, International Journal of Environmental Research and Public HealthCarpal tunnel syndrome conservative treatment: A literature review
2022, Postepy Psychiatrii i NeurologiiCross-sectional changes of the distal carpal tunnel with simulated carpal bone rotation
2022, Computer Methods in Biomechanics and Biomedical Engineering
- ☆
Ethics Committee approval of the study protocol – Universitat Intenacional de Catalunya – reference number CBAS-2018-03.
- 1
Equal contribution.