Left musculus sternalis

During routine dissection in the Morphological Sciences Department II of the Universidad Complutense de Madrid, the presence of a sternalis muscle was observed in the left hemithorax of a 70-year-old male cadaver. We report on its position, relationships, and innervation, as well as its clinical relevance, indicating some guidelines for its physical examination. We also present a brief overview of the existing literature regarding the nomenclature, historical reports, and incidence of this muscle.     

Innervation of the sternalis muscle accompanied by congenital partial absence of the pectoralis major muscle

In one case accompanied by congenital partial absence of the pectoralis major muscle the sternalis muscle was examined to confirm its innervation by means of analysis of intramuscular nerve distribution. It was proved that the sternalis muscle was supplied only by the pectoral nerves even in the case of sternalis in direct contact with the proper thoracic wall. These findings as well as the results of Ura (1937) and Morita (1944) favor the interpretation presented by Eisler (1901), in which the sternalis muscle was described as being supplied only by the pectoral nerves. However, the problem of double innervation of the sternalis requires continued discussion because the relationships between the pectoral nerves and the branches of the intercostal nerves or extramural nerves (Yamada & Mannen, 1985; Kodama et al., 1986) have not yet been resolved. The precise genesis of the sternalis muscle should be also examined though it has already been proved to be derived from the pectoralis muscle group including the subcutaneous trunci muscle.     

Bilateral sternalis with unusual left-sided presentation: a clinical perspective

An unusual variation creates interest among anatomists, but is a cause of concern among clinicians when it mimics a pathology. The sternalis muscle is one such variant of the anterior chest wall located subcutaneously over the pectoralis major, ranging from a few short fibers to a well-formed muscle. We observed a bilateral case, which was accompanied by an atypical presentation on the left side where a huge, bulky sternalis muscle was associated with the absence of the sternal fibers of the pectoralis major. The fibers arose as a lateral strip from the upper two-thirds of the body of the sternum and costal cartilages 2 through 6 with the intervening fascia and aponeurosis of the external oblique. The right sternalis was strap-like and was placed vertically over the sternal fibers of the pectoralis major, arising from the underlying fascia and aponeurosis of the external oblique. The sternalis muscles, on each side, converged into an aponeurosis over the manubrium that was continuous with the sternal heads of the right and left sternocleidomastoid muscle, respectively. This rare anomaly has puzzled radiologists and surgeons in confirming diagnosis, missing it all together or mistaking it for a tumor on mammography or CT scan. These findings prompted us to review its topography, development, and application in relation to the anterior chest wall.     

Unusual origin of the flexor digiti minimi brevis muscle

An unusual origin of the flexor digiti minimi brevis muscle of the right hand was discovered during cadaveric dissection. The muscle originated from the anterior aspect of the transverse fibers of the distal antebrachial fascia and inserted onto the base of the fifth proximal phalanx. When traction was applied to the proximal portion of the muscle, flexion was produced at the fifth metacarpophalangeal joint. Other intrinsic muscles of the hand and the muscles of the flexor forearm compartment had normal morphology. Although muscular anomalies in the hypothenar region have been described, the muscular variant described here was distinct in its origin and size from those previously reported. Knowledge of anomalous muscles in the hand has important clinical significance in routine surgery and in determining associated pathology.     

The sternalis muscle in the Bulgarian population: classification of sternales

The sternalis muscle (musculus sternalis) is the name usually given to this common anatomical variant, but the terms 'episternalis', 'presternalis', 'sternalis brutorum', 'rectus thoracis', 'rectus sterni', 'superficial rectus abdominis' and 'japonicus' have also been used in the literature (for reviews see Le Double, 1879; Calori, 1888; Pichler, 1911; Blees, 1968). According to Turner (1867), Cabrolius was the first, in 1604, to describe sternalis. Nevertheless this muscle is often unknown even in clinical practice (Bailey & Tzarnas, 1999; Vandeweyer, 1999).
Thus far, investigations on the incidence of sternalis have been made both in large populations such as the American (Barlow, 1935) and small populations, for example in Taiwan (Shen et al. 1992; Jeng & Su, 1998). In Europe, all studies on the frequency of this muscle have been made amongst subpopulations in Western (e.g. Cunningham, 1888; Le Double, 1890, 1897) and Northern Europe (Gruber, 1860) although the reported frequencies have been quite different. There is a lack of information about sternalis in Eastern European populations. We therefore present data from a study on the incidence of sternalis muscle in Bulgaria.     

The sternalis muscle: an uncommon anatomical variant among Taiwanese

The sternalis muscle is an uncommon anatomical variant. It is located on the human anterior pectoral wall, superficial to pectoralis major. This muscle has been reported both in males and females, and in whites, blacks and Asians (Barlow, 1934; Kida & Kudoh, 1991; Shen et al. 1992; Bradley et al. 1996).
Although the importance of this muscle is still a mystery, various different interpretations have been made. Clemente (1985) considered sternalis to be a misplaced pectoralis major, although some embryologists have viewed it as part of a ventral longitudinal column muscle layer arising at the ventral tip of the hypomeres (Sadler, 1995). Sadler claimed that this muscle is represented by rectus abdominis in the abdominal region and by the infrahyoid musculature in the cervical region; in the thorax, this layer usually disappears but occasionally remains as a sternalis muscle. Kitamura et al. (1985) reported a case of congenital partial deficiency of pectoralis major accompanied by an enormous sternalis. Barlow (1934), on the other hand, claimed that sternalis represents the remains of a panniculus carnosus.     

游离背阔肌皮瓣的感觉神经支配应用解剖

目的：为形成带感觉神经的游离背阔肌皮瓣提供解剖学基础。方法：在20例40侧成人躯干标本上，观测了分布于背阔肌区域的肋间神经、胸脊神经的来源、走行及分布规律。结果：T5～10神经外侧支的后支在腋前线1～2cm相应肋间穿出，呈节段性重叠性分布肩胛线以外的背阔肌区皮肤；其中T6～8分布于皮瓣范围较大、神经蒂较长并距血管蒂接近。第6～11胸脊神经后支穿出骶棘肌后，在胸腰筋膜中走行4～5cm距离，后穿出在背阔肌浅层行3～5cm，呈重叠性节段性分布于肩胛线内侧的背阔肌区的皮肤。其中以第8、9胸脊神经后支在皮瓣中分布较大。结论：可设计以第6～8肋间神经外侧支的后支和/或以第8、9胸脊神经后支为神经蒂的感觉背阔肌皮瓣。     

Sternalis muscle: importance in surgery of the breast

Mastectomy is a commonly performed surgery for carcinoma of breast. During surgery, pectoral fascia is removed and pectoralis major muscle is laid bare. Sternalis is a rare muscle encountered in the subcutaneous plane. We examined the operative records of 1,152 patients who underwent modified radical mastectomies between 1990 and 2000. Patients who underwent conservative breast surgery or radical mastectomy were excluded. Among 1,152 patients who underwent modified radical mastectomy, eight were identified as having sternalis, a subcutaneously placed muscle oriented craniocaudally. The thickness of the muscle varied. The muscle was spared in all patients. Sternalis is a rare muscle in the subcutaneous plane. It should not be mistaken for a mass on mammography. During surgery it is important to be aware of this rare entity and identify the muscle early so that the dissection plane is appropriate. The depth at which internal mammary nodes are irradiated may also vary in the presence of the muscle. In addition, it should not be mistaken for recurrence on follow-up.

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Electronic Supplementary Material The french version of this article is available in the form of electronic supplementary material and can be obtained by using the Springer Link server located at .

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Le muscle sternal: importance dans la chirurgie du sein

Résumé La mastectomie est le procédé chirurgical le plus souvent réalisé pour traiter le cancer du sein, comportant l'ablation du fascia du muscle grand pectoral qui est mis à nu. Le muscle sternal est rarement retrouvé dans le plan sous-cutané. Sur un total de 1,152 mastectomies radicales modifiées (1990–2000), excluant les gestes de conservation mammaire et les mastectomies radicales classiques, un muscle sternal sous-cutané, à orientation crânio-caudale et d'épaisseur variable, a été trouvé dans 8 cas et toujours préservé. Le muscle sternal peut être confondu avec une tumeur sur la mammographie. Il est important de le repérer rapidement dans le plan sous-cutané pour utiliser le bon plan de clivage. Il peut modifier la technique d'irradiation des noeuds lymphatiques parasternaux et être considéré à tort comme une récidive tumorale.

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大鼠眼上直肌神经的生后发育

取生后两天、两周和两月的雄性Ｗｉｓｔａｒ大鼠双眼上直肌，进行硝酸银染色和乙酰胆碱酯酶染色，用光镜观察大鼠眼上直肌神经在生后的发育情况。在大鼠生后两天时，动眼神经的分支从眼上直肌的中后三分之一交界处由眶面进入该肌，它向该肌的球面区发出细小的神经纤维束，这些神经束抵达同一条肌纤维上。眶面层神经纤维细小，单条并且平行于肌纤维方向走行。此时，眼上直肌对乙酰胆碱酯酶染色着色浅，反应区未形成某一特定轮廓，说明此时运动神经的发育是不成熟的。在生后两周时，动眼神经的分支开始向眼上直肌的眶面层发出神经纤维；球面区中的神经纤维有明显的粗细两种。这时眼上直肌中的运动神经轴索对乙酰胆碱酯酶染色反应，出现葡萄状运动神经末梢及斑点状运动终板的雏形。生后两月时，眼上直肌中出现了肌梭及典型的葡萄状运动神经末梢和斑点状运动终板。生后两周是大鼠睁眼初期，由此可见，大鼠从闭眼至睁眼的时期，是运动神经发育的关键时期，此时，运动神经形成一些特定神经末梢，而睁眼后运动神经的发育主要在此基础上运动神经末梢日趋完善和成熟。     

Surgical anatomy of the pectoral nerves and the pectoral musculature

The pectoral nerves (PNs) may be selectively injured through various traumatic mechanisms such as direct trauma, hypertrophic muscle compression, and iatrogenic injuries (breast surgery and axillary node dissection, pectoralis major muscle transfers). The PN may be surgically recovered through nerve transfers. They may also be used as donors to the musculocutaneous, axillary, long thoracic, and spinal accessory nerves and for reinnervation of myocutaneous free flaps. Thus, in this article, we reviewed the surgical anatomy of PN. A meta-analysis of the available literature showed that the lateral pectoral nerve (LPN) arises most frequently with two branches from the anterior divisions of the upper and middle trunks (33.8%) or as a single root from the lateral cord (23.4%). The medial pectoral nerve (MPN) usually arises from the medial cord (49.3%), anterior division of the lower trunk (43.8%), or lower trunk (4.7%). The two PN are usually connected immediately distal to the thoracoacromial artery by the so-called ansa pectoralis. The MPN may also show communications with the intercostobrachial nerve. In 50%-100% of cases, it may pass, at least with some branches, through the pectoralis minor muscle. The LPN supplies the upper portions of the pectoralis major muscle; the MPN innervates the lower parts of the pectoralis major and the pectoralis minor muscle. Among the accessory muscles of the pectoral girdle, the LPN may also innervate the tensor semivaginae articulationis humero-scapularis, pectoralis minimus, sternoclavicularis, axillary arch, sternalis, and infraclavicularis muscles; the MPN may innervate the pectoralis quartus, chondrofascialis, axillary arch, chondroepitrochlearis, and sternalis muscles.     

Development of the rectus abdominis and its sheath in the human fetus

Purpose: Although the rectus abdominis and its sheath are well known structures, their development in the human fetus is poorly understood. Materials and Methods: We examined rectus abdominis and sheath development in semiserial horizontal sections of 18 fetuses at 5-9 weeks of gestation. Results: Rectus muscle differentiation was found to commence above the umbilicus at 6 weeks and extend inferiorly. Until closure of the anterior chest wall via fusion of the bilateral sternal anlagen (at 7 weeks), the anterior rectal sheath originated from the external oblique and developed towards the medial margin of the rectus abdominis at all levels, including the supracostal part. After formation of the anterior sheath, fascial laminae from the internal oblique and transversus abdominis contributed to formation of the posterior rectus sheath. However, the posterior sheath was absent along the supracostal part of the rectus abdominis, as the transversus muscle fibers reached the sternum or the midline area. Therefore, it appeared that resolution of the physiological umbilical hernia (8-9 weeks) as well as chest wall closure was not required for development of the rectus abdominis and its sheath. Conversely, in the inferior part of the two largest fetal specimens, after resolution of the hernia, the posterior sheath underwent secondary disappearance, possibly due to changes in mechanical stress. Conclusion: Upward extension of the rectus abdominis suddenly stopped at the margin of the inferiorly developing pectoralis major without facing the external intercostalis. The rectus thoracis, if present, might correspond to the pectoralis.     

The fascia of the limbs and back – a review

Although fasciae have long interested clinicians in a multitude of different clinical and paramedical disciplines, there have been few attempts to unite the ensuing diverse literature into a single review. The current article gives an anatomical perspective that extends from the gross to the molecular level. For expediency, it deals only with fascia in the limbs and back. Particular focus is directed towards deep fascia and thus consideration is given to structures such as the fascia lata, thoracolumbar fascia, plantar and palmar fascia, along with regional specializations of deep fascia such as retinacula and fibrous pulleys. However, equal emphasis is placed on general aspects of fascial structure and function, including its innervation and cellular composition. Among the many functions of fascia considered in detail are its ectoskeletal role (as a soft tissue skeleton for muscle attachments), its importance for creating osteofascial compartments for muscles, encouraging venous return in the lower limb, dissipating stress concentration at entheses and acting as a protective sheet for underlying structures. Emphasis is placed on recognizing the continuity of fascia between regions and appreciating its key role in coordinating muscular activity and acting as a body-wide proprioceptive organ. Such considerations far outweigh the significance of viewing fascia in a regional context alone.     

Arcuate line of the rectus sheath: clinical approach

The rectus sheath has been extensively described in gross anatomic studies but there is very little information available regarding the arcuate line (AL). The aim of the present study therefore was to explore and delineate the morphology, topography and morphometry of the arcuate line and provide a comprehensive picture of its anatomy across a broad range of specimens. The AL was present in all specimens examined. In addition, the AL was found to be located at a mean of 70.2% (67.3–75.2%) of the distance between the pubic symphysis and the umbilicus, and at 33.9% (30.2–35.4%) of the distance between the pubic symphysis and the xiphoid process. This location was found to be at a mean of 2.1 ± 2.3 cm superior to the level of the anterior superior iliac spines. Furthermore, there were three distinct types of AL morphology. In type I (65%), the fibers of the posterior rectus sheath (PRS) gradually disappeared over the transversalis fascia, creating an incomplete demarcation of the actual location of the AL. In type II (25%) the termination of the fibers of the PRS was acutely demarcated over the transversalis fascia, creating a clear border with the AL. In type III (10%) the fibers of the PRS created a double and thickened aponeurotic line. In these cases a double AL was observed. Better preoperative knowledge of the location of the AL may, in some cases, help preoperative planning to facilitate primary fascial repair, which can then be supported with on-lay mesh, depending on the clinical situation.     

A Taiwanese with a pair of sternalis muscles.

A pair of sternalis muscles have been found on both sides of the chest in an adult Taiwanese male. The muscles are located superficial to the medial part of the pectoralis major, arising from the sternum and are inserted into the sheaths of the rectus abdominis. They are innervated by the intercostal nerve. It should be emphasized that the sternalis muscle is rarely found in Taiwan.     

Prevalence and variance of the sternalis muscle: a study in the Chinese population using multi-detector CT

Objective

To analyze the prevalence, anatomical features, as well as variance of the sternalis muscle in the Chinese population using multi-detector computed tomography (MDCT).

Methods

We retrospectively reviewed 6,000 adult axial MDCT images to determine the overall and gender prevalence of the sternalis muscles. We also analyzed the side prevalence and anatomical features, including shape, size, location and course.

Results

The sternalis muscle was present in 347 (5.8 %) of 6,000 adults. This muscle was more common in males (6.0 %, 187/3091) than in females (5.5 %, 160/2909). Among the 347 adults, 118 (34.0 %) had bilateral sternalis muscles; 148 (42.7 %) had right sternalis muscles; and 81 (23.3 %) had left sternalis muscles. The sternalis muscle was either flat or nodular and located superficial to the major pectoral muscles on CT axial transverse images. According to the muscle morphology and course, we classified sternalis muscles as three different types and nine subtypes. The muscles appeared with a single head and single belly in 58.5 %, double or multiple heads in 18.1 %, and double or multiple bellies in 23.4 %. The mean length, width and thickness were 111.1 ± 33.0, 17.7 ± 9.9 and 4.1 ± 1.7 mm measured on MDCT.

Conclusion

The sternalis muscle was highly prevalent in normal Chinese adults. MDCT is an effective method to demonstrate this muscle in vivo.     

Morphological characteristics of the posterior brachial cutaneous nerve--a consideration of the development of cutaneous nerves in man

The posterior brachial cutaneous nerve (Cbp) has certain characteristic features, being different from adjacent cutaneous nerves such as the medial brachial cutaneous nerve (Cbm) and the intercostobrachial nerve (Icb). These features are summarized as follows. 1) At the dorsal surface of the arm, the Cbp passes deeply beneath the fascia of the arm covering the dorsal surface of the long head of the triceps brachii, whereas the Cbm and the Icb pass superficial to it. In this area, the Cbp is accompanied in its course by a small artery. 2) The Cbp has no communication with the Cbm and the Icb on its way to the arm. 3) A precise and more detailed examination using a stereoscopic microscope reveals that the Cbp supplies the branches to the fascia of the dorsal surface of the arm, before passing through it. 4) The Cbp arises from the stem of the radial nerve forming a common trunk with the muscular branch to the long head of the triceps brachii. 5) In the brachial plexus, the Cbp is derived from segments C7 and C8, mainly the latter, and is composed of the most caudal elements of the radial nerve. According to the dermatome map, it would be unreasonable to consider that the Cbp (C8) is distributed in the skin, being intercalated between the Cbm (T1) and the Icb (T2). 6) Comparative anatomically, the Cbp cannot be observed in the monkey, dog, cat, rabbit or rat. Instead, in these animals, the muscular branch to the dorsoepitrochlearis arises from the radial nerve and takes the same course as that of the Cbp in man. According to Eisler (1901, 1912), when a muscle degenerates during the process of phylogeny or ontogeny, the supplying nerve sometimes remains in loco, as if representing the site where the muscle previously existed. As examples of these cases, Eisler described the following findings. 1) A fine branch arises from the loop of the cervical nerve and supplies the fascia, which extends between the clavicle and the omohyoid muscle. Eisler considered the fascia to be a remnant of the cleidohyoid muscle, which normally exists in lower mammals. 2) A branch sometimes arises from the lateral cutaneous branch of the upper intercostal nerve and passes along the ventral thoracic wall. Eisler considered this branch to be derived from the nerve supplying the external oblique abdominal muscle. 3) The interosseous nerve of the legs shows a remnant of the nerve supplying the pre-existing posterior interosseous muscle.(ABSTRACT TRUNCATED AT 250 WORDS)     

Architectural design, fiber-type composition, and innervation of the rat rectus abdominis muscle.

The rectus abdominis muscle is architecturally compartmentalized by tendinous intersections and is supplied by multiple thoracic nerves. In this study, the rectus abdominis of the rat has been qualitatively and quantitatively examined with regard to muscle dimensions, fiber organization, fiber-type composition, and innervation. The muscle exhibits architectural heterogeneity and different patterns of innervation among its thoracic, epigastric, and hypogastric parts. The epigastric part, adherent to the rectus sheath via tendinous intersections, represents relatively simple design. It is formed by serially arranged compartments with shorter fibers, compared with the other parts. These compartments are segmentally supplied by thoracic nerves. The hypogastric part is more complex, forms an interdigitation of muscular slips, and has segmental distribution of thoracic nerves in mediolateral direction. The thoracic part much differs from the other parts. It has smaller cross-sectional areas, compartments composed of abundant nonspanning fibers with intrafascicular termination, and non-segmental distribution of thoracic nerves. In addition to these craniocaudal specializations among the three parts, the muscle exhibits mediolateral differences in fiber-type composition. Slow-twitch oxidative fibers are more densely distributed in the medial half region than the lateral, whereas fast-twitch glycolytic fibers follow an inverse pattern. The mediolateral differences in fiber-type composition as well as the craniocaudal specializations in architectural design and innervation imply regionally differentiated recruitments of the muscle in various behaviors.     

A study on the communication between the pectoral nerve and the extramural nerve branches of the intercostal nerves]

Kumaki et al. (1979) defined the extramural nerve as the rudimentary sensory nerve which appeared on the upper thoracic wall; it branched off the root of the lateral cutaneous nerve of the second, third or fourth intercostal nerve, ran inferomedially adhering to the fascia of the intercostalis externus muscle and ended supplying the membrane covering the adjacent rib. They also stated that the extramural nerve (Rxm) occasionally became a cutaneous nerve which pierced the pectoralis muscles and supplied the skin covering the thoracic wall similar to the lateral cutaneous nerve (Rcl) or the anterior cutaneous nerve (Rca). Further, they proposed that the muscular nerves to the obliquus externus abdominis muscle which are usually situated below the fifth rib might be considered a part of this Rxm series. Although the definition of Rxm is still not widely accepted, Rxm is thought to be a key morphological factor influencing the variations of peripheral nerve arrangement on the thoracic wall. In the student course of gross anatomy dissection at Iwate Medical University School of Medicine during the years 1987-1991, three cases of Rxm communicating with the pectoral nerve and supplying the pectoralis major muscle were observed. Some cases have been reported in which Rcl innervates part of the pectoral muscles. However, the communication between the pectoral nerve and Rxm has not yet been discussed. Therefore, to clarify the morphological significance of the communication between Rxm and the pectoral nerve, the branching pattern and the distribution of the pectoral nerves were extensively investigated and the intramuscular nerve supply of some pectoral nerves, especially the pectoral nerves which communicated with Rxm, was examined in detail under a stereomicroscope. The results are summarized as follows: 1. In the first case, Rxm of the second intercostal nerve originated from Rcl, ran inferomedially adhering to the fascia of the intercostalis externus muscle and pierced the origin of the pectoralis minor muscle at the third intercostal space. Then Rxm turned superolaterally to communicate with a pectoral nerve which originated from the loop composed of the lateral and medial pectoral nerves and passed inferior to the pectoralis minor muscle. After communication, the pectoral nerve with Rxm supplied the caudalmost part of the sternocostal portion of the pectoralis major muscle. In the second case, a similar branch of Rxm of the second intercostal nerve passed inferior to the pectoralis minor muscle.(ABSTRACT TRUNCATED AT 400 WORDS)     

Successful management of apical abscess after Nipro left ventricular assisted device explantation by removal of apical cuff and omentopexy

Nipro-Toyobo-paracorporeal pulsatile flow VAD (Nipro VAD; Nipro, Osaka, Japan) has been used most commonly as a paracorporeal VAD (p-VAD) in Japan. There are few reports describing clinical course of post LVAD explantation and its complication. We herein present two cases of apical abscess after the explantation of the device. SSI is a main risk factor of formation of the apical abscess at the time of LVAD explantation. It is mandatory to perform sufficient debridement and closure of the layers including abdominal muscle and anterior abdominal fascia at exit sites in the explantation surgery. Omentopexy is also helpful for prevention from infection. Routine removal of apical cuff and outflow graft could be considered as one of the options when LVAD is explanted as bridge to recovery.     

The panniculus carnosus muscle: an evolutionary enigma at the intersection of distinct research fields

The panniculus carnosus is a thin striated muscular layer intimately attached to the skin and fascia of most mammals, where it provides skin twitching and contraction functions. In humans, the panniculus carnosus is conserved at sparse anatomical locations with high interindividual variability, and it is considered of no functional significance (most possibly being a remnant of evolution). Diverse research fields (such as anatomy, dermatology, myology, neuroscience, surgery, veterinary science) use this unique muscle as a model, but several unknowns and misconceptions remain in the literature. In this article, we review what is currently known about panniculus carnosus structure, development, anatomical location, response to environmental stimuli and potential function(s), with the aim of putting together the evidence arising from the different research communities and raising interest in this unique muscle, which we postulate as an ideal model for both vascular and muscular research.