Carpal Arch Changes in Response to Thenar Muscle Loading

Arch Height ◽

Thenar Muscle ◽

Morphometric Analyses ◽

Muscle Loading

Abstract 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 < 0.01), muscle combination (p < 0.05), and their interaction (p < 0.01). The changes to arch height and area were significantly dependent on the muscle combinations (p = 0.001 and p < 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 < 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 < 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.

Biomechanical interaction between the transverse carpal ligament and the thenar muscles

Journal of Applied Physiology ◽

10.1152/japplphysiol.01273.2012 ◽

2013 ◽

Vol 114 (2) ◽

pp. 225-229 ◽

Cited By ~ 8

Author(s):

Zhilei Liu Shen ◽

Zong-Ming Li

Keyword(s):

Carpal Tunnel Syndrome ◽

Carpal Tunnel ◽

Morphological Changes ◽

Maximum Voluntary Contraction ◽

Muscle Contractions ◽

Arch Height ◽

Thenar Muscle ◽

Pinch Force ◽

Tunnel Syndrome

The transverse carpal ligament (TCL) serves as the origin of the thenar muscles and is integral to thenar muscle contraction anatomically and biomechanically. TCL hypertrophy has been observed in patients with carpal tunnel syndrome and is potentially caused by repetitive hand use. The purpose of this study was to investigate the biomechanical interaction between the TCL and the thenar muscles. Specifically, the morphological changes of the carpal arch, formed by the TCL, in response to thenar muscle contractions were examined during isometric tip pinch between the thumb and index finger. Ultrasound videos of the carpal tunnel were recorded from 13 healthy subjects and were synchronized with the forces measured by a pinch dynamometer. The thenar muscles' ulnar point, trapezium, and hamate were tracked by a pattern-matching program. The pinch force significantly affected the carpal arch height, width, and area ( P < 0.005). As the pinch force increased from 0 to 100% maximum voluntary contraction force, the carpal arch height increased from 1.8 ± 1.0 to 2.3 ± 1.3 mm, the carpal arch width decreased from 23.9 ± 2.4 to 23.1 ± 2.4 mm, and the carpal arch area increased from 22.2 ± 13.6 to 27.3 ± 16.3 mm2. The TCL was pulled volarly during thenar muscle contractions, providing evidence for the biomechanical interaction between the ligament and muscles. Repetitive biomechanical stimulation on the TCL from thenar muscle contractions could lead to tissue remodeling and then TCL hypertrophy. This study sheds light on the potential cause of TCL hypertrophy, which may be an etiological factor for carpal tunnel syndrome.

Carpal Tunnel Expansion by Palmarly Directed Forces to the Transverse Carpal Ligament

Journal of Biomechanical Engineering ◽

10.1115/1.3148469 ◽

2009 ◽

Vol 131 (8) ◽

Cited By ~ 21

Author(s):

Zong-Ming Li ◽

Jie Tang ◽

Matthew Chakan ◽

Rodrigo Kaz

Keyword(s):

Carpal Tunnel ◽

Geometrical Model ◽

Arch Height ◽

Cross Sectional ◽

Arch Width ◽

Force Application ◽

Fresh Frozen ◽

Applied Forces ◽

Insertion Sites

This study investigated the expansion of the carpal tunnel resulting from the application of palmarly directed forces to the transverse carpal ligament (TCL) from inside the carpal tunnel. Ten fresh-frozen cadaveric hands were dissected to evacuate the carpal tunnel, and thus to expose the TCL. A custom lever device was built to apply forces, ranging from 10 N to 200 N, to the TCL. Without force application, the carpal tunnel area was 148.4±36.8 mm2. The force application caused the TCL to form arches with an increase in cross-sectional areas of 33.3±5.6 mm2 at 10 N and 48.7±11.4 mm2 at 200 N, representing respective increases of 22.4% and 32.8% relative to the initial carpal tunnel area. The TCL length remained constant under the applied forces. It was found that the TCL arch formation was due to the narrowing of the arch width, which resulted from the migration of the bony insertion sites of the TCL. A geometrical model of the carpal tunnel was then developed to elucidate the relationships among the arch width, TCL length, arch height, and arch area. The model illustrated the effectiveness of carpal tunnel expansion by TCL elongation or arch width narrowing.

CARPAL TUNNEL SYNDROME IN PATIENT WITH HEMIHYPERTROPHY: CASE REPORT

Hand Surgery ◽

10.1142/s021881041372026x ◽

2013 ◽

Vol 18 (03) ◽

pp. 411-412

Author(s):

Takashi Shimoe ◽

Yasunori Taniguchi ◽

Munehito Yoshida

Keyword(s):

Magnetic Resonance Imaging ◽

Carpal Tunnel Syndrome ◽

Carpal Tunnel ◽

Common Condition ◽

Resonance Imaging ◽

Thenar Muscle ◽

Left Hand ◽

Tunnel Syndrome

Carpal tunnel syndrome is a common condition; however, it has not been previously reported in patients with hemihypertrophy. A 67-year-old woman with left-sided hemihypertrophy presented with carpal tunnel syndrome of the left hand. Magnetic resonance imaging showed enlargement of the median nerve proximal to the transverse carpal ligament. Carpal tunnel decompression was performed, and pain was immediately relieved by decompression of the carpal tunnel. At the six-month follow-up examination, the patient experienced relief from numbness and improvement in thenar muscle atrophy was noted.

THUMB OPPOSITION IN SEVERE CARPAL TUNNEL SYNDROME WITH UNDETECTABLE APB-CMAP

Hand Surgery ◽

10.1142/s0218810414500208 ◽

2014 ◽

Vol 19 (02) ◽

pp. 199-204 ◽

Cited By ~ 5

Author(s):

Tatsuki Ebata ◽

Katsumi Imai ◽

Susumu Tokunaga ◽

Yuji Takahasi ◽

Yoshihiro Abe

Keyword(s):

Carpal Tunnel Syndrome ◽

Muscle Atrophy ◽

Carpal Tunnel ◽

Compound Muscle Action Potential ◽

Thenar Muscle ◽

Needle Electromyography ◽

Muscle Action Potential ◽

Muscle Innervation ◽

Tunnel Syndrome

Thumb opposition does not always represent the function of the median nerve due to variations in thenar muscle innervation. One hundred and thirty hands of 109 idiopathic carpal tunnel syndrome (CTS) patients with an undetectable compound muscle action potential of the abductor pollicis brevis (APB-CMAP) were classified into one of four groups; Type 1 (86.2%) had thenar muscle atrophy and could not perform thumb opposition; Type 2 (10.8%) had thenar muscle atrophy but could perform thumb opposition; Type 3 (2.3%) did not have thenar muscle atrophy and could perform thumb opposition, but needle electromyography of the APB showed neurogenic changes and Type 4 (0.8%) had no thenar muscle atrophy, could perform thumb opposition, and needle electromyography showed no neurogenic changes. Over 10% of severe CTS patients have mild or no muscle atrophy and intact thumb opposition. The purpose of this study was to investigate the variations in thenar muscle innervation in patients with severe CTS.

Thenar and Hypothenar Muscle Coverage on the Transverse Carpal Ligament

Journal of Wrist Surgery ◽

10.1055/s-0041-1735887 ◽

2021 ◽

Author(s):

Farah Alsafar ◽

Zong-Ming Li

Keyword(s):

Carpal Tunnel ◽

Carpal Tunnel Release ◽

Thenar Muscle ◽

Cross Sectional ◽

Tunnel Syndrome ◽

Carpal Tunnel Release Surgery ◽

Automated Algorithms ◽

Hypothenar Muscle

Abstract 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.

Anomalous Thenar Musculature Associated with Aberrant Median Nerve Motor Branch Take-off: An Anatomic and Clinical Study

The Duke Orthopaedic Journal ◽

10.5005/jp-journals-10017-1013 ◽

2012 ◽

Vol 2 (1) ◽

pp. 18-22 ◽

Cited By ~ 1

Author(s):

Gary M Lourie ◽

R Glenn Gaston ◽

Allan E Peljovich ◽

Jason J Marshall ◽

Lee Patterson

Keyword(s):

Clinical Study ◽

Median Nerve ◽

Carpal Tunnel ◽

Carpal Tunnel Release ◽

Anatomic Study ◽

Thenar Muscle ◽

High Association ◽

Motor Branch ◽

Endoscopic Techniques

ABSTRACT Introduction Iatrogenic laceration of the median nerve motor branch during carpal tunnel release is a devastating complication that has been reported with both open and endoscopic techniques. The purpose of this study is to highlight a previously underreported relationship between an aberrant course of the median nerve motor branch and an anomalous thenar muscle that places the motor branch at high risk. Materials and methods This was a two part study. The first part was a retrospective review of over 500 cases of carpal tunnel release over a 7 year period. There were 530 carpal tunnel releases performed and 20/530 cases were found to have a characteristic anomalous thenar muscle associated with a consistent aberrant course of the motor branch of the median nerve. Part two was an anatomic study in which 42 cadaveric wrists were dissected to determine median nerve branching patterns, dimensions of the transverse carpal ligament, and thenar musculature dimensions. Results Twenty patients (3.8%) in the clinical arm were found to have anomalous musculature. In each case, the characteristics of the muscle were similar; the muscle was triangular in shape, was distal to the FPB, and had minimal fascial covering. In 100% of the cases the motor branch was found to be more anterior/central or ulnar in its take-off. In the anatomic study, two hands (5%) had aberrant musculature extending distal to the transverse carpal ligament (TCL). Both were associated with an anterior/central or ulnar median motor branch take-off with recurrent course. Larger thenar musculature dimensions and anomalous thenar muscle were associated with more anterior and ulnar motor branch take-off. Conclusion There appears to be a high association between anomalous thenar musculature and an aberrant course of the motor branch of the median nerve placing it a greater potential risk for iatrogenic injury. Lourie GM, Gaston RG, Peljovich AE, Marshall JJ, Patterson L. Anomalous Thenar Musculature Associated with Aberrant Median Nerve Motor Branch Take-off: An Anatomic and Clinical Study. The Duke Orthop J 2012;2(1):18-22.

Minimally invasive modified Camitz opponensplasty for severe carpal tunnel syndrome

Journal of Orthopaedic Surgery ◽

10.1177/2309499018770914 ◽

2018 ◽

Vol 26 (2) ◽

pp. 230949901877091

Author(s):

Mitsuhiko Nanno ◽

Norie Kodera ◽

Yuji Tomori ◽

Shinro Takai

Keyword(s):

Carpal Tunnel Syndrome ◽

Minimally Invasive ◽

Carpal Tunnel ◽

Modified Technique ◽

Thenar Muscle ◽

Painful Wrist ◽

Tunnel Syndrome ◽

Group 2 ◽

Group 1

Purpose: We aimed to compare the clinical results and the complications between the minimally invasive modified Camitz opponensplasty and the conventional Camitz opponensplasty for severe carpal tunnel syndrome (CTS), and to evaluate the efficacy of the modified technique for CTS. Methods: Twenty-eight hands in 24 patients with severe CTS who had disorder of the thumb opposition with thenar muscle atrophy (group 1) were treated by minimally invasive modified Camitz opponensplasty, passing the transferred palmaris longus (PL) tendon under the abductor pollicis brevis (APB) fascia using only palm and thumb incision, and no incision to either wrist crease or forearm. Ten hands in 10 patients (group 2) were treated by the conventional Camitz opponensplasty. Clinical evaluation was made by comparing the results before and after surgery for the angle of the thumb palmar abduction, pinch power, and grip strength. Results: All clinical findings significantly improved after surgery compared with before surgery in all patients. In group 1, there were no complications including transferred tendon bowstring, painful wrist scar, or injury to the palmar cutaneous branch of the median nerve in all hands. Conversely, patients in group 2 had four painful wrist scars and nine bowstrings of the transferred tendon. Conclusions: Several complications have been considered to attribute to the long incision and an extensive dissection crossing the wrist crease from the palm to the wrist in the conventional Camitz procedure. The current modified Camitz opponensplasty by minimally invasive incision without straddling the wrist crease is a simple and effective procedure that can decrease the risk of painful scar around the wrist crease in severe CTS patients with disorder of thumb opposition. Additionally, this technique, by passing the transferred PL tendon under the APB fascia, is useful in restoring the thumb opposition immediately, and in preventing the bowstringing of the transferred tendon.

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

Journal of Wrist Surgery ◽

10.1055/s-0040-1721437 ◽

2021 ◽

Author(s):

Trevor Simcox ◽

Lauren Seo ◽

Kevin Dunham ◽

Shengnan Huang ◽

Catherine Petchprapa ◽

...

Keyword(s):

Carpal Tunnel Syndrome ◽

Correlation Coefficient ◽

Carpal Tunnel ◽

Case Control Study ◽

Anatomical Variation ◽

Case Control ◽

Large Variability ◽

Tunnel Syndrome ◽

Control Study

Abstract 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.

Soft tissue abnormalities in Wassel Type VI radial polydactyly: a detailed anatomical study

Journal of Hand Surgery (European Volume) ◽

10.1177/1753193421990212 ◽

2021 ◽

Vol 46 (4) ◽

pp. 352-359

Author(s):

Susumu Saito ◽

Itaru Tsuge ◽

Hiroki Yamanaka ◽

Naoki Morimoto

Keyword(s):

Soft Tissue ◽

Three Dimensional ◽

Anatomical Study ◽

Metacarpophalangeal Joint ◽

Level Of Evidence ◽

Thenar Muscle ◽

Pulley System ◽

Radial Deviation ◽

Tissue Abnormalities

Wassel VI radial polydactyly is associated with metacarpal adduction and radial deviation of the metacarpophalangeal joint of the ulnar duplicate. The soft tissue abnormalities responsible for these deformities were characterized using preoperative multi-planar three-dimensional ultrasound and intraoperative observation in four patients. In all patients, the abductor pollicis brevis and superficial head of the flexor pollicis brevis inserted into the radial first metacarpal, whereas the adductor pollicis and deep head of the flexor pollicis brevis inserted into the ulnar thumb. Aberrant location of the flexor pollicis longus and absence of the A1 pulley system was associated with severe radial deviation. An additional superficial thenar muscle along the ulnar metacarpal was associated with minimal metacarpal adduction. Uneven forces on the ulnar duplicate could be associated with these characteristic deformities and joint instability. Knowledge of these abnormalities allows better planning of surgery and further insight into this rare radial polydactyly configuration. Level of evidence: II

The Variable Insertional Anatomy of the Abductor Pollicis Longus: Functional Relevance and Relationship to Adjacent Thumb Extensors

Hand ◽

10.1177/1558944721999734 ◽

2021 ◽

pp. 155894472199973

Author(s):

Shruthi Deivasigamani ◽

Ali Azad ◽

S. Steven Yang

Keyword(s):

Cross Sectional Area ◽

Sectional Area ◽

Thenar Muscle ◽

Cross Sectional ◽

Extensor Pollicis Longus ◽

Abductor Pollicis Longus ◽

Branching Patterns ◽

Functional Relevance ◽

And Function

Background The abductor pollicis longus (APL) is classically described as inserting on the base of the first metacarpal. This study analyzed APL insertional anatomy and quantified the size of various elements of the extensor side of the thumb to determine associations with size and function. Methods Twenty-four formalin-preserved upper limbs were dissected. The insertional anatomy of the APL, extensor pollicis brevis, and extensor pollicis longus were characterized, and the capacity of APL tendon slips to perform palmar abduction of the first digit was quantified based on slip size and insertion. Results The mean number of APL tendon slips observed was 2.3. Abductor pollicis longus insertion sites included the base of the first metacarpal, trapezium, abductor pollicis brevis, and opponens pollicis. Only 4 specimens had a solitary metacarpal slip, while 83% of specimens had insertions onto at least 1 thenar muscle. A total of 62.5% of APL tendons exhibited some form of branching that we categorized into “Y” and “Z” patterns. In assessing palmar abduction capacity, we found that APL tendon slips inserting into the base of the first metacarpal were larger in cross-sectional area than nonmetacarpal slips and reproduced complete palmar abduction of the digit in the absence of nonmetacarpal slips. The abduction capacity of APL tendon slips was not correlated to the cross-sectional area. Conclusions There is significant variability in APL tendon slips, branching patterns, and insertional anatomy. These findings provide further understanding of the function of the APL and its surgical implications.