Hypothenar Muscles

*Muscle Cell and Tissue - Novel Molecular Targets and Current Advances*

on FoxO1 transcription factor in pulmonary hypertension. Nat Med.

[28] Feng W, Wang J, Yan X, Zhai C, Shi W, Wang Q, Zhang Q, Li M. Paclitaxel alleviates monocrotalineinduced pulmonary arterial hypertension via inhibition of FoxO1-mediated autophagy. Naunyn Schmiedebergs Arch Pharmacol.

[29] Zhao J, Yang M, Wu X, Yang Z, Jia P, Sun Y, Li G, Xie L, Liu B, Liu H. Effects of paclitaxel intervention on pulmonary vascular remodeling in rats with pulmonary hypertension. Exp Ther

[30] Kassa B, Mickael C, Kumar R,

Hernandez-Saavedra D, Tuder RM, Graham BB. Paclitaxel blocks Th2 mediated TGF-β activation in Schistosoma mansoni-induced pulmonary hypertension. Pulm Circ.

2014;20:1289-1300.

2019;392:605-613.

Med. 2019;17:1163-1170.

Sanders L, Koyanagi D,

2019;9:2045894018820813.

[31] Xiao J, Zhao H, Liang D, Liu Y, Zhang H, Liu Y, Li J, Peng L, Zhou Z, Chen YH. Taxol, a microtubule stabilizer, improves cardiac contractile function during ischemia in vitro. Pharmacology. 2010;**85**:301-310.

2019;8:e011227.

[32] Shults NV, Kanovka SS, Ten Eyck JE, Rybka V, Suzuki YJ. Ultrastructural changes of the right ventricular myocytes in pulmonary arterial hypertension. J Am Heart Assoc.

**70**

**73**

**Chapter 5**

Canal

**Abstract**

clinical significance

**1. Introduction**

*Georgi P. Georgiev*

Hypothenar Muscles and Guyon's

The increased number of articles in the last years about hypothenar variations and some misdescriptions and the role of the additional structures to ulnar nerve and artery compression, as well as my unostentatious contribution in the field, provoked me to write this chapter. The aim of it is to present in detail the usual hypothenar muscular anatomy, including the origins and insertions of the hypothenar muscles, their relations to each other, the vascular supply and innervation, the function of the muscles, the reported variations and their possible clinical implications. Herein, I also presented briefly the Guyon's canal anatomy and some interesting comments about it. Presenting the compendium about hypothenar muscles and the canal to my opinion will help the anatomists and the clinicians to better understand the clinically oriented anatomy. They also will be more qualified in the anatomical dissection course as well as during the surgical interventions. The detailed knowledge of the anatomy in the region would be also useful to medical

Muscular variations of the hypothenar have been well described in the medical literature [1–3]. In most cases, these muscles are asymptomatic and are found during anatomical dissections, surgical interventions or imaging modalities. In some cases, variant hypothenar muscles may cause ulnar nerve and artery compression, as presented in some surgical case reports [4–10]. Shea and McClain [11] reported

At the region of the wrist, the ulnar nerve passes through a fibro-osseous tunnel known as "Guyon's canal" or "distal ulnar tunnel", in which the ulnar nerve could be compressed [4, 6, 8, 12–14]. Different causes as trauma, lipoma, false aneurysm of the ulnar artery, ganglion cyst and rarely aberrant muscular slips have been reported [3, 15]. In some surgical reports, different variant muscles, usually abductor digiti minimi, followed by flexor digiti minimi brevis have been reported, as a cause of ulnar nerve compression [4, 6, 8, 12–14]. In all cases the excision of the additional muscle was curative. However, it should be pointed out that the clinical appearance of the variant muscles should be related to two factors: the anatomical site and the muscle hypertrophy [4]. According to Turner and Caird [16],

students in better understanding the hypothenar region.

**Keywords:** hypothenar muscles, anatomy, variations, Guyon's canal,

that around 3% of compression neuropathies are due to variant muscle.

#### **Chapter 5**

## Hypothenar Muscles and Guyon's Canal

*Georgi P. Georgiev*

#### **Abstract**

The increased number of articles in the last years about hypothenar variations and some misdescriptions and the role of the additional structures to ulnar nerve and artery compression, as well as my unostentatious contribution in the field, provoked me to write this chapter. The aim of it is to present in detail the usual hypothenar muscular anatomy, including the origins and insertions of the hypothenar muscles, their relations to each other, the vascular supply and innervation, the function of the muscles, the reported variations and their possible clinical implications. Herein, I also presented briefly the Guyon's canal anatomy and some interesting comments about it. Presenting the compendium about hypothenar muscles and the canal to my opinion will help the anatomists and the clinicians to better understand the clinically oriented anatomy. They also will be more qualified in the anatomical dissection course as well as during the surgical interventions. The detailed knowledge of the anatomy in the region would be also useful to medical students in better understanding the hypothenar region.

**Keywords:** hypothenar muscles, anatomy, variations, Guyon's canal, clinical significance

#### **1. Introduction**

Muscular variations of the hypothenar have been well described in the medical literature [1–3]. In most cases, these muscles are asymptomatic and are found during anatomical dissections, surgical interventions or imaging modalities. In some cases, variant hypothenar muscles may cause ulnar nerve and artery compression, as presented in some surgical case reports [4–10]. Shea and McClain [11] reported that around 3% of compression neuropathies are due to variant muscle.

At the region of the wrist, the ulnar nerve passes through a fibro-osseous tunnel known as "Guyon's canal" or "distal ulnar tunnel", in which the ulnar nerve could be compressed [4, 6, 8, 12–14]. Different causes as trauma, lipoma, false aneurysm of the ulnar artery, ganglion cyst and rarely aberrant muscular slips have been reported [3, 15]. In some surgical reports, different variant muscles, usually abductor digiti minimi, followed by flexor digiti minimi brevis have been reported, as a cause of ulnar nerve compression [4, 6, 8, 12–14]. In all cases the excision of the additional muscle was curative. However, it should be pointed out that the clinical appearance of the variant muscles should be related to two factors: the anatomical site and the muscle hypertrophy [4]. According to Turner and Caird [16],

a provoking factor, such as acute injury or repetitive minor trauma, as well as the type of the work, could predispose to hypertrophy of the variant muscles. There are reports of ulnar nerve compression syndromes provoked by anomalous muscles in which additional factors exist [1, 4, 17]. In addition to nerve compression, a hypothenar muscle variation could be also associated with thrombosis of the ulnar artery in Guyon's canal [7, 18].

In recent years the increased interest and numerous articles about hypothenar variants and Guyon's canal provoke me to make a brief review and make a compendium of normal anatomy of the muscles in the hypothenar region as well to present the reported variations and their possible clinical significance. I hope that this chapter will make future studies on this theme easier and help anatomist, hand surgeons and medical students for better knowledge of anatomy and for better clinical practice.

#### **2. Anatomy, variations and clinical significance**

#### **2.1 Palmaris brevis muscle (Pbm)**

Pbm is a small cutaneous hand muscle, located superficially to the hypothenar eminence and considered to be atavistic remnant of the panniculus carnosus. The Pbm is usually presented by a thin, quadrilateral in form muscle body, lying beneath the skin of the ulnar aspect of the palm. It has been reported to start from the flexor retinaculum and palmar aponeurosis and insert in the skin and fascia of the medial palm (**Figure 1**) [19–24].

#### *2.1.1 Variations*

The variations of the Pbm are rarely reported in the literature. This muscle could vary in size and may be absent or duplicated; it could also insert to flexor digiti minimi brevis muscle or the pisiform bone [25, 26].

**75**

**Figure 2.**

*Hypothenar Muscles and Guyon's Canal DOI: http://dx.doi.org/10.5772/intechopen.91477*

neurovascular bundle at the wrist [21].

**2.2 Abductor digiti minimi muscle (ADMm)**

This muscle and its variants could simulate soft tissue tumor [27] or provoke ulnar nerve compression at the wrist [17, 28]; Pbm flap could be used in the treatment of recurrent carpal tunnel syndrome [29] and Pbm spasm syndrome [30].

Pbm deepens the hollow of the palm and presents muscular barrier of the ulnar

The Pbm is innervated by the motor component of the superficial branch of the

The ADMm is situated more ulnarly of the hypothenar muscles and arises from the pisiform bone and from the tendon of the flexor carpi ulnaris muscle; it attaches as a flat tendon that finally divides into two parts: one that inserts to the ulnar side of the base of the proximal phalanx of the little finger and the other to the ulnar border of the aponeurosis of the extensor digiti quinti proprius

Different variations of ADMm have been reported in the anatomical and surgical literature. They include the absence and presence of a second head, variant origin (from the pisiform bone, fascia of the forearm, palmaris longus tendon,

*Schematic anterior view of the wrist and hand presenting the ADMm (asterisk).*

*2.1.2 Clinical application*

*2.1.3 Actions*

*2.1.4 Innervation*

ulnar nerve [24].

(**Figure 2**) [20, 21].

*2.2.1 Variations*

**Figure 1.** *Schematic anterior view of the wrist and hand presenting the Pbm (asterisk).*

#### *2.1.2 Clinical application*

This muscle and its variants could simulate soft tissue tumor [27] or provoke ulnar nerve compression at the wrist [17, 28]; Pbm flap could be used in the treatment of recurrent carpal tunnel syndrome [29] and Pbm spasm syndrome [30].

#### *2.1.3 Actions*

*Muscle Cell and Tissue - Novel Molecular Targets and Current Advances*

**2. Anatomy, variations and clinical significance**

minimi brevis muscle or the pisiform bone [25, 26].

*Schematic anterior view of the wrist and hand presenting the Pbm (asterisk).*

**2.1 Palmaris brevis muscle (Pbm)**

palm (**Figure 1**) [19–24].

*2.1.1 Variations*

in Guyon's canal [7, 18].

clinical practice.

a provoking factor, such as acute injury or repetitive minor trauma, as well as the type of the work, could predispose to hypertrophy of the variant muscles. There are reports of ulnar nerve compression syndromes provoked by anomalous muscles in which additional factors exist [1, 4, 17]. In addition to nerve compression, a hypothenar muscle variation could be also associated with thrombosis of the ulnar artery

In recent years the increased interest and numerous articles about hypothenar variants and Guyon's canal provoke me to make a brief review and make a compendium of normal anatomy of the muscles in the hypothenar region as well to present the reported variations and their possible clinical significance. I hope that this chapter will make future studies on this theme easier and help anatomist, hand surgeons and medical students for better knowledge of anatomy and for better

Pbm is a small cutaneous hand muscle, located superficially to the hypothenar eminence and considered to be atavistic remnant of the panniculus carnosus. The Pbm is usually presented by a thin, quadrilateral in form muscle body, lying beneath the skin of the ulnar aspect of the palm. It has been reported to start from the flexor retinaculum and palmar aponeurosis and insert in the skin and fascia of the medial

The variations of the Pbm are rarely reported in the literature. This muscle could

vary in size and may be absent or duplicated; it could also insert to flexor digiti

**74**

**Figure 1.**

Pbm deepens the hollow of the palm and presents muscular barrier of the ulnar neurovascular bundle at the wrist [21].

#### *2.1.4 Innervation*

The Pbm is innervated by the motor component of the superficial branch of the ulnar nerve [24].

#### **2.2 Abductor digiti minimi muscle (ADMm)**

The ADMm is situated more ulnarly of the hypothenar muscles and arises from the pisiform bone and from the tendon of the flexor carpi ulnaris muscle; it attaches as a flat tendon that finally divides into two parts: one that inserts to the ulnar side of the base of the proximal phalanx of the little finger and the other to the ulnar border of the aponeurosis of the extensor digiti quinti proprius (**Figure 2**) [20, 21].

#### *2.2.1 Variations*

Different variations of ADMm have been reported in the anatomical and surgical literature. They include the absence and presence of a second head, variant origin (from the pisiform bone, fascia of the forearm, palmaris longus tendon,

**Figure 2.** *Schematic anterior view of the wrist and hand presenting the ADMm (asterisk).*

fascia of the flexor carpi radialis, intermuscular fascia, flexor carpi ulnaris, flexor retinaculum, both from the flexor retinaculum and antebrachial fascia), fusion with the flexor digiti minimi brevis, presence of a "deep abductor-flexor"(m. abductorflexor digiti minimi profundus), triple origin and also coexistence with reversed palmaris longus muscle [4, 5, 9, 15, 25–27, 31–38].

#### *2.2.2 Clinical application*

Hypertrophied ADMm could simulate soft tissue tumor [5] or ulnar nerve compression at the wrist [13, 14] and may be associated with ulnar artery thrombosis in Guyon's canal [7]; ADMm myocutaneous flap can be used for opponensplasty [39].

#### *2.2.3 Actions*

The ADMm abducts the little finger from the ring finger and contributes to the fifth metacarpophalangeal joint flexion and interphalangeal extension [20, 21].

#### *2.2.4 Innervation*

ADMm is innervated by the deep branch of the ulnar nerve (C8, Th1) [20, 21].

#### **2.3 Flexor digiti minimi brevis muscle (FDMBm)**

The FDMBm is situated more radially than the ADMm. It starts from the hamulus of the hamate bone, and the anterior surface of the flexor retinaculum, and inserts into the ulnar side of the base of the phalanx of the little finger (**Figure 3**) [20, 21].

**77**

**Figure 4.**

*Hypothenar Muscles and Guyon's Canal DOI: http://dx.doi.org/10.5772/intechopen.91477*

The reported variations of the FDMBm in the available literature are absence and presence of an accessory slip from the palmaris longus tendon, presence of a slip to the metacarpal, replacement by a tendinous band arising from the flexor carpi ulnaris muscle and inserting into the fifth proximal phalanx and the hamate bone, presence of accessory FDMBm, fusion with ADMm or opponens digiti minimi muscles, origin from the antebrachial fascia, deep abductor-flexor of little finger, FDMBm with triple

Hypertrophied FDBMm could simulate soft tissue tumor [44] or ulnar nerve

The FDBMm flexion of the proximal phalanx, also with some lateral rotation

FDBMm is innervated by the deep branch of the ulnar nerve (C8, Th1) [20, 21].

The ODMm has a triangular form, lying beneath the ADMm and FDMBm. It starts from the hamulus of the hamate bone and near part of the flexor retinaculum and attaches to the ulnar margin and palmar surface of the fifth metacarpal bone

origin and origin from flexor carpi radialis muscle [25, 26, 33, 40–43].

*2.3.1 Variations*

*2.3.2 Clinical application*

*2.3.3 Actions*

*2.3.4 Innervation*

(**Figure 4**) [20, 21].

[20, 21].

compression at the wrist [8, 12].

**2.4 Opponens digiti minimi muscle (ODMm)**

*Schematic anterior view of the wrist and hand presenting the ODMm (asterisk).*

**Figure 3.** *Schematic anterior view of the wrist and hand presenting the FDMBm (asterisk).*

#### *2.3.1 Variations*

*Muscle Cell and Tissue - Novel Molecular Targets and Current Advances*

palmaris longus muscle [4, 5, 9, 15, 25–27, 31–38].

**2.3 Flexor digiti minimi brevis muscle (FDMBm)**

*Schematic anterior view of the wrist and hand presenting the FDMBm (asterisk).*

*2.2.2 Clinical application*

opponensplasty [39].

*2.2.3 Actions*

*2.2.4 Innervation*

(**Figure 3**) [20, 21].

fascia of the flexor carpi radialis, intermuscular fascia, flexor carpi ulnaris, flexor retinaculum, both from the flexor retinaculum and antebrachial fascia), fusion with the flexor digiti minimi brevis, presence of a "deep abductor-flexor"(m. abductorflexor digiti minimi profundus), triple origin and also coexistence with reversed

Hypertrophied ADMm could simulate soft tissue tumor [5] or ulnar nerve

The ADMm abducts the little finger from the ring finger and contributes to the fifth metacarpophalangeal joint flexion and interphalangeal extension [20, 21].

ADMm is innervated by the deep branch of the ulnar nerve (C8, Th1) [20, 21].

The FDMBm is situated more radially than the ADMm. It starts from the hamulus of the hamate bone, and the anterior surface of the flexor retinaculum, and inserts into the ulnar side of the base of the phalanx of the little finger

compression at the wrist [13, 14] and may be associated with ulnar artery thrombosis in Guyon's canal [7]; ADMm myocutaneous flap can be used for

**76**

**Figure 3.**

The reported variations of the FDMBm in the available literature are absence and presence of an accessory slip from the palmaris longus tendon, presence of a slip to the metacarpal, replacement by a tendinous band arising from the flexor carpi ulnaris muscle and inserting into the fifth proximal phalanx and the hamate bone, presence of accessory FDMBm, fusion with ADMm or opponens digiti minimi muscles, origin from the antebrachial fascia, deep abductor-flexor of little finger, FDMBm with triple origin and origin from flexor carpi radialis muscle [25, 26, 33, 40–43].

#### *2.3.2 Clinical application*

Hypertrophied FDBMm could simulate soft tissue tumor [44] or ulnar nerve compression at the wrist [8, 12].

#### *2.3.3 Actions*

The FDBMm flexion of the proximal phalanx, also with some lateral rotation [20, 21].

#### *2.3.4 Innervation*

FDBMm is innervated by the deep branch of the ulnar nerve (C8, Th1) [20, 21].

#### **2.4 Opponens digiti minimi muscle (ODMm)**

The ODMm has a triangular form, lying beneath the ADMm and FDMBm. It starts from the hamulus of the hamate bone and near part of the flexor retinaculum and attaches to the ulnar margin and palmar surface of the fifth metacarpal bone (**Figure 4**) [20, 21].

**Figure 4.** *Schematic anterior view of the wrist and hand presenting the ODMm (asterisk).*

#### *2.4.1 Variations*

The reported variations of the ODMm are rarely described in the literature and include absence, splitting into two parts and merging with ADMm [25, 26].

#### *2.4.2 Clinical application*

There is no clinical application reported.

#### *2.4.3 Innervation*

The ODMm is innervated by the deep branch of the ulnar nerve (C8, Th1) [20, 21].

#### *2.4.4 Actions*

The ODMm flexes and laterally rotates the fifth metacarpal bone at the carpometacarpal joint, brings the fifth finger into opposition with the thumb and together with the ADMm and FDMBm absorbs forces on the ulnar border of the hand [20, 21].

#### **3. Anatomy of Guyon's canal**

The Guyon's canal or ulnar canal is a fibro-osseous tunnel situated between the pisiform and the hook of the hamate and measured around 40–45 mm in length [45, 46]. In 1861, it is first described by the French surgeon Jean Casimir Félix Guyon. He presented it as an intra-aponeurotic compartment which the anterior wall is constituted by a fibrous layer and its posterior wall by the anterior carpal ligament [47]. Guyon's canal is situated between the proximal edge of the palmar carpal ligament to the fibrous arch of the hypothenar muscles at the level of the hook of the hamate (**Figure 5**). Through this canal the ulnar nerve and artery pass from the forearm to the palm, as the nerve is lying deep and ulnar to the artery. Of course, the vena comitans and connective fatty tissue fill up this space [48, 49].

Guyon's canal has been described as a space with complex and variable anatomy [48]. It should be pointed out that the canal is not a rigid structure and varying in its dimensions [50]. According to Ombaba et al. [49], it has dynamic space, and its relationships are changed during wrist movement.

Precise knowledge of the anatomy of Guyon's canal is essential in understanding the diagnosis and treatment of ulnar tunnel syndrome [51]. This tunnel is a potential entrapment site that could provoke compression of the ulnar nerve, presented by paresthesia or numbness, or both, to the ulnar two digits, as well as hand weakness, atrophy and ungainliness [51]. The compression could be localized in three zones [11, 52]:

Zone I: compression occurs proximal to or within Guyon's canal, before the nerve bifurcation, and presents with combined motor and sensory deficits.

Zone II: compression involves only the deep motor branch and occurs as the ulnar nerve exits Guyon's canal or at the hook of the hamate level.

Zone III: compression, with isolated superficial sensory branch involvement, may also occur as the nerve exits Guyon's canal or at the hook of the hamate distal to the bifurcation.

Importantly during surgical interventions, all three compartments should be decompressed, including the pisohamate hiatus, by releasing the pisohamate arcade [49].

Different muscular variations have been reported as the most common anatomical predispositions that might contribute to the ulnar nerve compression

**79**

canal [38, 53].

**Figure 5.**

**4. Conclusion**

ulnar nerve compression.

**Acknowledgements**

ings illustrated in the chapter.

*Hypothenar Muscles and Guyon's Canal DOI: http://dx.doi.org/10.5772/intechopen.91477*

in Guyon's canal [51]. Different muscular variations related to the ADMm, followed by FDMBm, are reported [8, 12–14]. In these cases, ultrasonography or MRI could help clinicians to clearly identify the muscular variants in Guyon's

*pisiform bone (Pis.); hamate bone (ham.); ulnar nerve (UN); ulnar artery (UA).*

*Anatomy of Guyon's canal. Pisohamate ligament (asterisk); deep motor branch of the ulnar nerve (arrow);* 

This chapter summarizes the existing data in the literature concerning the anatomy of the hypothenar muscles, as well as its variants and the anatomy of Guyon's canal. I hope that the presented literature data will help students in learning anatomy, help the anatomists and hand surgeons during their works, as well as for better scientific production and to better understand, describe and classify the muscular variations and Guyon's canal. Using the chapter, they will avoid mistakes in classifying different variations of the hypothenar muscles. I think that the knowledge of reported variants will ensure self-confidence and avoid confusions during wrist and palm procedures, especially during releasing Guyon's canal, extended carpal tunnel release, or palmar fasciectomy. Precise knowledge of the anatomy and its variant also would help radiologist in their routine work on ultrasonography and MRI, where different variations could be evaluated in cases of soft tissue tumor or in diagnosis of primary or recurrent

The author would like to thank Mr. Ahmed Hashim Mohamed Ali (Student at Medical University of Sofia, Bulgaria) for the kind help through his excellent draw*Hypothenar Muscles and Guyon's Canal DOI: http://dx.doi.org/10.5772/intechopen.91477*

#### **Figure 5.**

*Muscle Cell and Tissue - Novel Molecular Targets and Current Advances*

There is no clinical application reported.

relationships are changed during wrist movement.

The reported variations of the ODMm are rarely described in the literature and

The ODMm is innervated by the deep branch of the ulnar nerve (C8, Th1) [20, 21].

The ODMm flexes and laterally rotates the fifth metacarpal bone at the carpometacarpal joint, brings the fifth finger into opposition with the thumb and together with the ADMm and FDMBm absorbs forces on the ulnar border of the hand [20, 21].

The Guyon's canal or ulnar canal is a fibro-osseous tunnel situated between the pisiform and the hook of the hamate and measured around 40–45 mm in length [45, 46]. In 1861, it is first described by the French surgeon Jean Casimir Félix Guyon. He presented it as an intra-aponeurotic compartment which the anterior wall is constituted by a fibrous layer and its posterior wall by the anterior carpal ligament [47]. Guyon's canal is situated between the proximal edge of the palmar carpal ligament to the fibrous arch of the hypothenar muscles at the level of the hook of the hamate (**Figure 5**). Through this canal the ulnar nerve and artery pass from the forearm to the palm, as the nerve is lying deep and ulnar to the artery. Of course, the vena comitans and connective fatty tissue fill up this space [48, 49].

Guyon's canal has been described as a space with complex and variable anatomy [48]. It should be pointed out that the canal is not a rigid structure and varying in its dimensions [50]. According to Ombaba et al. [49], it has dynamic space, and its

Precise knowledge of the anatomy of Guyon's canal is essential in understanding the diagnosis and treatment of ulnar tunnel syndrome [51]. This tunnel is a potential entrapment site that could provoke compression of the ulnar nerve, presented by paresthesia or numbness, or both, to the ulnar two digits, as well as hand weakness, atrophy and ungainliness [51]. The compression could be localized in three zones [11, 52]: Zone I: compression occurs proximal to or within Guyon's canal, before the nerve bifurcation, and presents with combined motor and sensory deficits.

Zone II: compression involves only the deep motor branch and occurs as the

Zone III: compression, with isolated superficial sensory branch involvement, may also occur as the nerve exits Guyon's canal or at the hook of the hamate distal to

Importantly during surgical interventions, all three compartments should be decompressed, including the pisohamate hiatus, by releasing the pisohamate

Different muscular variations have been reported as the most common anatomical predispositions that might contribute to the ulnar nerve compression

ulnar nerve exits Guyon's canal or at the hook of the hamate level.

include absence, splitting into two parts and merging with ADMm [25, 26].

*2.4.1 Variations*

*2.4.3 Innervation*

*2.4.4 Actions*

*2.4.2 Clinical application*

**3. Anatomy of Guyon's canal**

**78**

the bifurcation.

arcade [49].

*Anatomy of Guyon's canal. Pisohamate ligament (asterisk); deep motor branch of the ulnar nerve (arrow); pisiform bone (Pis.); hamate bone (ham.); ulnar nerve (UN); ulnar artery (UA).*

in Guyon's canal [51]. Different muscular variations related to the ADMm, followed by FDMBm, are reported [8, 12–14]. In these cases, ultrasonography or MRI could help clinicians to clearly identify the muscular variants in Guyon's canal [38, 53].

#### **4. Conclusion**

This chapter summarizes the existing data in the literature concerning the anatomy of the hypothenar muscles, as well as its variants and the anatomy of Guyon's canal. I hope that the presented literature data will help students in learning anatomy, help the anatomists and hand surgeons during their works, as well as for better scientific production and to better understand, describe and classify the muscular variations and Guyon's canal. Using the chapter, they will avoid mistakes in classifying different variations of the hypothenar muscles. I think that the knowledge of reported variants will ensure self-confidence and avoid confusions during wrist and palm procedures, especially during releasing Guyon's canal, extended carpal tunnel release, or palmar fasciectomy. Precise knowledge of the anatomy and its variant also would help radiologist in their routine work on ultrasonography and MRI, where different variations could be evaluated in cases of soft tissue tumor or in diagnosis of primary or recurrent ulnar nerve compression.

#### **Acknowledgements**

The author would like to thank Mr. Ahmed Hashim Mohamed Ali (Student at Medical University of Sofia, Bulgaria) for the kind help through his excellent drawings illustrated in the chapter.

### **Conflict of interest**

The author declares no conflict of interest.

#### **Abbreviations**


#### **Author details**

Georgi P. Georgiev Department of Orthopedics and Traumatology, University Hospital Queen Giovanna-ISUL, Medical University of Sofia, Sofia, Bulgaria

\*Address all correspondence to: georgievgp@yahoo.com

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

**81**

1994;**306**:120-123

*Hypothenar Muscles and Guyon's Canal DOI: http://dx.doi.org/10.5772/intechopen.91477*

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[4] Jeffery AK. Compression of the deep palmar branch of the ulnar nerve by an anomalous muscle. Case report and review. Journal of Bone and Joint Surgery. British Volume (London).

[5] Simodynes EE, Cochran RM 2nd. Anomalous muscles in the hand and wrist--report of three cases. The Journal of Hand Surgery. 1981;**6**(6):553-554. DOI: 10.1016/s0363-5023(81)80129-3

[6] James MR, Rowley DI, Norris SH. Ulnar nerve compression by an accessory abductor digiti minimi muscle presenting following injury. Injury. 1987;**18**:66-67. DOI: 10.1016/0020-1383(87)90393-7

[7] Pribyl CR, Moneim MS. Anomalous hand muscle found in the Guyon's canal at exploration for ulnar artery thrombosis. A case report. Clinical Orthopaedics and Related Research.

[8] Spinner RJ, Lins RE, Spinner M. Compression of the medial half of the deep branch of the ulnar nerve by an

**References**

jhsa.2004.01.006

1971;**53**:718-723

*Hypothenar Muscles and Guyon's Canal DOI: http://dx.doi.org/10.5772/intechopen.91477*

#### **References**

*Muscle Cell and Tissue - Novel Molecular Targets and Current Advances*

The author declares no conflict of interest.

ADMm abductor digiti minimi muscle FDMBm flexor digiti minimi brevis muscle ODMm opponens digiti minimi muscle

Pbm palmaris brevis muscle

**Conflict of interest**

**Abbreviations**

**80**

**Author details**

Georgi P. Georgiev

Department of Orthopedics and Traumatology, University Hospital Queen

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

Giovanna-ISUL, Medical University of Sofia, Sofia, Bulgaria

\*Address all correspondence to: georgievgp@yahoo.com

provided the original work is properly cited.

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[6] James MR, Rowley DI, Norris SH. Ulnar nerve compression by an accessory abductor digiti minimi muscle presenting following injury. Injury. 1987;**18**:66-67. DOI: 10.1016/0020-1383(87)90393-7

[7] Pribyl CR, Moneim MS. Anomalous hand muscle found in the Guyon's canal at exploration for ulnar artery thrombosis. A case report. Clinical Orthopaedics and Related Research. 1994;**306**:120-123

[8] Spinner RJ, Lins RE, Spinner M. Compression of the medial half of the deep branch of the ulnar nerve by an

anomalous origin of the flexor digiti minimi. A case report. The Journal of Bone and Joint Surgery. American Volume. 1996;**78**:427-430

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[16] Turner MS, Caird DM. Anomalous muscles and ulnar nerve compression at the wrist. The Hand. 1977;**9**:140-142. DOI: 10.1016/s0072-968x(77)80007-7

[17] Tonkin MA, Lister GD. The palmaris brevis profundus. An anomalous muscle associated with ulnar nerve compression at the wrist. The Journal of Hand Surgery. 1985;**10**:862-864

[18] Moss DP, Forthman CL. Ulnar artery thrombosis associated with anomalous hypothenar muscle. Journal of Surgical Orthopaedic Advances. 2008 Summer;**17**(2):85-88

[19] von Lanz T, Wachsmuth W. Arm. In: Praktische Anatomie. 1. Bd, 3. Teil. Berlin: Verlag von Julius Springer; 1935. p. 193

[20] Clemente CD. Anatomy of the Human Body. 30th ed. Philadelphia: Lea and Febiger; 1985. pp. 553-554

[21] Standring S, Borley NR, Gray H. Gray's Anatomy: The Anatomical Basis of Clinical Practice. 40th ed. Edinburgh: Churchill Livingstone/Elsevier; 2008. pp. 857-898

[22] Nayak SR, Krishnamurthy A. An unusually large palmaris brevis muscle and its clinical significance. Clinical Anatomy. 2007;**20**:978-979. DOI: 10.1002/ca.20542

[23] Moore CW, Beveridge TS, Rice CL. Fiber type composition of the palmaris brevis muscle: Implications for palmar function. Journal of Anatomy. 2017;**231**:626-633. DOI: 10.1111/joa.12652

[24] Moore CW, Rice CL. Structural and functional anatomy of the palmaris brevis: Grasping for answers. Journal of Anatomy. 2017;**231**:939-946. DOI: 10.1111/joa.12675

[25] Macalister A. Additional observations on muscular anomalies in human anatomy (third series), with a catalogue of the principal

muscular variations hitherto published. Transactions of the Royal Irish Academy. 1875;**25**:1-130

[26] Bergman RA, Afifi AK, Miyauchi R. Part I: Muscular system. In: Illustrated Encyclopedia Of Human Anatomic Variations. 2019. Available from: http://www.anatomyatlases.org/ AnatomicVariants/AnatomyHP.shtml [Accessed: 26 November 2019]

[27] Lipscomb PR. Duplication of hypothenar muscles simulating softtissue tumor of the hand. Report of a case. The Journal of Bone and Joint Surgery. American Volume. 1960;**42**:1058-1061

[28] Robinson D, Aghasi MK, Halperin N. Ulnar tunnel syndrome caused by an accessory palmaris muscle. Orthopaedic Review. 1989;**18**:345-347

[29] Rose EH. The use of the palmaris brevis flap in recurrent carpal tunnel syndrome. Hand Clinics. 1996;**12**: 389-395

[30] Eswaradass PV, Kalidoss R, Ramasamy B, Gnanashanmugham G. Familial palmaris brevis spasm syndrome. Annals of Indian Academy of Neurology. 2014;**17**:141-142. DOI: 10.4103/0972-2327.128597

[31] Wood J. Variations in human myology observed during the winter session of 1866-1867 at King's college, London. In Variations in Human Myology. Vol IV. Proceedings of the Royal Society of London. 1867;**15**:518-546

[32] Wood J. Variations in human myology observed during the winter season of 1867-1868 at King's college, London. In Variations in Human Myology. Vol XVII. Proceedings of the Royal Society of London. 1868;**16**:483-525

[33] Le Double A. Muscles de la main. In: Traité des variations du système musculaire de l'homme. Tome II. Paris: Schleicher Frères; 1897. pp. 153-218

**83**

*Hypothenar Muscles and Guyon's Canal DOI: http://dx.doi.org/10.5772/intechopen.91477*

[35] Sañudo JR, Mirapeix RM,

1993;**182**(3):439-442

aanat.2006.11.003

2008;**13**:313-315

477-479

[34] Gloobe H, Pecket P. An anomalous muscle in the canal of Guyon (a possible ulnar nerve compression). Anatomischer Anzeiger. 1973;**133**:

wrist. Clinical Anatomy. 2007;**20**: 976-977. DOI: 10.1002/ca.20529

[44] Harvie P, Patel N, Ostlere SJ.

Prevalence and epidemiological variation of anomalous muscles at Guyon's canal. Journal of Hand Surgery (British). 2004;**29**:26-29. DOI: 10.1016/j.

[45] Depukat P, Mizia E, Kuniewicz M, Bonczar T, Mazur M, Pełka P, et al. Syndrome of canal of Guyon - definition, diagnosis, treatment and complication. Folia Medica Cracoviensia. 2015;**55**:17-23

Konopka T, et al. Anatomical variability and histological structure of the ulnar nerve in the Guyon's canal. Archives of Orthopaedic and Trauma Surgery. 2017;**137**:277-283. DOI: 10.1007/

[47] Guyon F. Note sur une disposition anatomique propere a la face anterieure de la region du poignet et non encore decrite. Bulletins de la Société Anatomique de Paris. 1861;**6**:184-186

[48] Bachoura A, Jacoby SM. Ulnar tunnel syndrome. The Orthopedic Clinics of North America. 2012;**43**: 467-474. DOI: 10.1016/j.ocl.2012.07.016

[49] Ombaba J, Kuo M, Rayan G. Anatomy of the ulnar tunnel and the influence of wrist motion on its morphology. The Journal of Hand Surgery. 2010;**35**:760-768. DOI: 10.1016/j.jhsa.2010.02.028

[50] Fadel ZT, Samargandi OA, Tang DT. Variations in the anatomical

structures of the Guyon canal. Plastic Surgery. 2017;**25**:84-92. DOI:

10.1177/2292550317694851

[46] Depukat P, Henry BM, Popieluszko P, Roy J, Mizia E,

s00402-016-2616-4

jhsa.2011.09.002

jhsb.2003.08.004

[43] Georgiev GP, Jelev L. An aberrant flexor digiti minimi brevis Manus muscle. The Journal of Hand Surgery. 2011;**36**:1965-1967. DOI: 10.1016/j.

Ferreira B. A rare anomaly of abductor digiti minimi. Journal of Anatomy.

[36] Georgiev GP, Jelev L, Surchev L. Undescribed variant muscle - "deep abductor-flexor" of the little finger, in relation to ulnar nerve compression at the wrist. Annals of Anatomy. 2007;**189**:276-282. DOI: 10.1016/j.

[37] Georgiev GP, Jelev L, Surchev L. Variations of the hypothenar muscles. Acta Morphologica et Anthropologica.

[38] Georgiev GP, Jelev L, Kinov P. Aberrant muscles at the Guyon's canal. International Journal of Anatomical

[39] Upton J, Taghinia AH. Abductor digiti minimi myocutaneous flap for opponensplasty in congenital hypoplastic thumbs. Plastic and Reconstructive Surgery. 2008;**122**:1807-1811. DOI: 10.1097/

[40] Saadeh FA, Bergman RA. An unusual accessory flexor (opponens) digiti minimi muscle. Anatomischer

Variations. 2010;**4**:67-69

PRS.0b013e31818cc260

Anzeiger. 1988;**165**:327-329

10.1002/ca.10122

[41] Wingerter S, Gupta S, Le S, Shamasunder S, Bernstein R, Rabitaille W, et al. Unusual origin of the flexor digiti minimi brevis muscle. Clinical Anatomy. 2003;**16**:531-533. DOI:

[42] Georgiev GP, Jelev L. Variant triple origin of the flexor digiti minimi brevis (Manus) muscle in relation to ulnar nerve and artery compression at the

*Hypothenar Muscles and Guyon's Canal DOI: http://dx.doi.org/10.5772/intechopen.91477*

*Muscle Cell and Tissue - Novel Molecular Targets and Current Advances*

muscular variations hitherto published.

[26] Bergman RA, Afifi AK, Miyauchi R. Part I: Muscular system. In: Illustrated Encyclopedia Of Human Anatomic Variations. 2019. Available from: http://www.anatomyatlases.org/ AnatomicVariants/AnatomyHP.shtml [Accessed: 26 November 2019]

Transactions of the Royal Irish Academy. 1875;**25**:1-130

[27] Lipscomb PR. Duplication of hypothenar muscles simulating softtissue tumor of the hand. Report of a case. The Journal of Bone and Joint Surgery. American Volume.

[28] Robinson D, Aghasi MK, Halperin N. Ulnar tunnel syndrome caused by an accessory palmaris muscle. Orthopaedic

[29] Rose EH. The use of the palmaris brevis flap in recurrent carpal tunnel syndrome. Hand Clinics. 1996;**12**:

[30] Eswaradass PV, Kalidoss R, Ramasamy B, Gnanashanmugham G. Familial palmaris brevis spasm syndrome. Annals of Indian Academy of Neurology. 2014;**17**:141-142. DOI:

[31] Wood J. Variations in human myology observed during the winter session of 1866-1867 at King's college, London. In Variations in Human

Myology. Vol IV. Proceedings of the Royal Society of London. 1867;**15**:518-546

[32] Wood J. Variations in human myology observed during the winter season of 1867-1868 at King's college, London. In Variations in Human Myology. Vol XVII. Proceedings of the Royal Society of London. 1868;**16**:483-525

[33] Le Double A. Muscles de la main. In: Traité des variations du système musculaire de l'homme. Tome II. Paris: Schleicher Frères; 1897. pp. 153-218

10.4103/0972-2327.128597

1960;**42**:1058-1061

Review. 1989;**18**:345-347

389-395

[16] Turner MS, Caird DM. Anomalous muscles and ulnar nerve compression at the wrist. The Hand. 1977;**9**:140-142. DOI: 10.1016/s0072-968x(77)80007-7

[17] Tonkin MA, Lister GD. The palmaris brevis profundus. An anomalous muscle associated with ulnar nerve compression

at the wrist. The Journal of Hand

[18] Moss DP, Forthman CL. Ulnar artery thrombosis associated with anomalous hypothenar muscle. Journal of Surgical Orthopaedic Advances. 2008

[19] von Lanz T, Wachsmuth W. Arm. In: Praktische Anatomie. 1. Bd, 3. Teil. Berlin: Verlag von Julius Springer; 1935. p. 193

[20] Clemente CD. Anatomy of the Human Body. 30th ed. Philadelphia: Lea

[21] Standring S, Borley NR, Gray H. Gray's Anatomy: The Anatomical Basis of Clinical Practice. 40th ed. Edinburgh: Churchill Livingstone/Elsevier; 2008.

[22] Nayak SR, Krishnamurthy A. An unusually large palmaris brevis muscle and its clinical significance. Clinical Anatomy. 2007;**20**:978-979. DOI:

[23] Moore CW, Beveridge TS, Rice CL. Fiber type composition of the palmaris

[24] Moore CW, Rice CL. Structural and functional anatomy of the palmaris brevis: Grasping for answers. Journal of Anatomy. 2017;**231**:939-946. DOI:

brevis muscle: Implications for palmar function. Journal of Anatomy. 2017;**231**:626-633. DOI: 10.1111/joa.12652

[25] Macalister A. Additional

observations on muscular anomalies in human anatomy (third series), with a catalogue of the principal

and Febiger; 1985. pp. 553-554

Surgery. 1985;**10**:862-864

Summer;**17**(2):85-88

pp. 857-898

10.1002/ca.20542

10.1111/joa.12675

**82**

[34] Gloobe H, Pecket P. An anomalous muscle in the canal of Guyon (a possible ulnar nerve compression). Anatomischer Anzeiger. 1973;**133**: 477-479

[35] Sañudo JR, Mirapeix RM, Ferreira B. A rare anomaly of abductor digiti minimi. Journal of Anatomy. 1993;**182**(3):439-442

[36] Georgiev GP, Jelev L, Surchev L. Undescribed variant muscle - "deep abductor-flexor" of the little finger, in relation to ulnar nerve compression at the wrist. Annals of Anatomy. 2007;**189**:276-282. DOI: 10.1016/j. aanat.2006.11.003

[37] Georgiev GP, Jelev L, Surchev L. Variations of the hypothenar muscles. Acta Morphologica et Anthropologica. 2008;**13**:313-315

[38] Georgiev GP, Jelev L, Kinov P. Aberrant muscles at the Guyon's canal. International Journal of Anatomical Variations. 2010;**4**:67-69

[39] Upton J, Taghinia AH. Abductor digiti minimi myocutaneous flap for opponensplasty in congenital hypoplastic thumbs. Plastic and Reconstructive Surgery. 2008;**122**:1807-1811. DOI: 10.1097/ PRS.0b013e31818cc260

[40] Saadeh FA, Bergman RA. An unusual accessory flexor (opponens) digiti minimi muscle. Anatomischer Anzeiger. 1988;**165**:327-329

[41] Wingerter S, Gupta S, Le S, Shamasunder S, Bernstein R, Rabitaille W, et al. Unusual origin of the flexor digiti minimi brevis muscle. Clinical Anatomy. 2003;**16**:531-533. DOI: 10.1002/ca.10122

[42] Georgiev GP, Jelev L. Variant triple origin of the flexor digiti minimi brevis (Manus) muscle in relation to ulnar nerve and artery compression at the

wrist. Clinical Anatomy. 2007;**20**: 976-977. DOI: 10.1002/ca.20529

[43] Georgiev GP, Jelev L. An aberrant flexor digiti minimi brevis Manus muscle. The Journal of Hand Surgery. 2011;**36**:1965-1967. DOI: 10.1016/j. jhsa.2011.09.002

[44] Harvie P, Patel N, Ostlere SJ. Prevalence and epidemiological variation of anomalous muscles at Guyon's canal. Journal of Hand Surgery (British). 2004;**29**:26-29. DOI: 10.1016/j. jhsb.2003.08.004

[45] Depukat P, Mizia E, Kuniewicz M, Bonczar T, Mazur M, Pełka P, et al. Syndrome of canal of Guyon - definition, diagnosis, treatment and complication. Folia Medica Cracoviensia. 2015;**55**:17-23

[46] Depukat P, Henry BM, Popieluszko P, Roy J, Mizia E, Konopka T, et al. Anatomical variability and histological structure of the ulnar nerve in the Guyon's canal. Archives of Orthopaedic and Trauma Surgery. 2017;**137**:277-283. DOI: 10.1007/ s00402-016-2616-4

[47] Guyon F. Note sur une disposition anatomique propere a la face anterieure de la region du poignet et non encore decrite. Bulletins de la Société Anatomique de Paris. 1861;**6**:184-186

[48] Bachoura A, Jacoby SM. Ulnar tunnel syndrome. The Orthopedic Clinics of North America. 2012;**43**: 467-474. DOI: 10.1016/j.ocl.2012.07.016

[49] Ombaba J, Kuo M, Rayan G. Anatomy of the ulnar tunnel and the influence of wrist motion on its morphology. The Journal of Hand Surgery. 2010;**35**:760-768. DOI: 10.1016/j.jhsa.2010.02.028

[50] Fadel ZT, Samargandi OA, Tang DT. Variations in the anatomical structures of the Guyon canal. Plastic Surgery. 2017;**25**:84-92. DOI: 10.1177/2292550317694851

Section 3

Mathematical Model of

Contraction in Vascular

Smooth Muscle

**85**

[51] Bozkurt MC, Tağil SM, Ozçakar L, Ersoy M, Tekdemir I. Anatomical variations as potential risk factors for ulnar tunnel syndrome: A cadaveric study. Clinical Anatomy. 2005;**18**:274-280. DOI: 10.1002/ca.20107

[52] Gross MS, Gelberman RH. The anatomy of the distal ulnar tunnel. Clinical Orthopaedics and Related Research. 1985;**196**:238-247

[53] Zeiss J, Guilliam-Haidet L. MR demonstration of anomalous muscles about the volar aspect of the wrist and forearm. Clinical Imaging. 1996;**20**:219-221. DOI: 10.1016/0899-7071(95)00013-5

### Section 3
