Muscular Variations Research Articles

Multiple muscular variations in the neck, upper extremity, and lower extremity biased toward the left side of a single cadaver.

Although numerous reports have found accessory or supernumerary muscles throughout the human body, multiple appearances of these variations biased toward one side of body are rare. We report a 76-yr-old male cadaver with an accessory head of the biceps brachii and palmaris profundus, and a muscular slip between the biceps femoris and semitendinosus on the left side in addition to a bilateral accessory belly of the digastric muscle. No remarkable nervous, vascular, or visceral variation accompanied these variations. An interruption of normal somitogenesis or myogenesis may be a cause of these variations.

Supraclavicularis proprius muscle associated with supraclavicular nerve entrapment.

Entrapment neuropathy of the supraclavicular nerve is rare and, when it occurs, is usually attributable to branching of the nerve into narrow bony clavicular canals. We describe another mechanism for entrapment of this nerve with the aberrant muscle; supraclavicularis being found during the routine dissection of an embalmed 82-year-old cadaver. Our report details a unique location for this rare muscular variation whereby the muscle fibres originated posteriorly on the medial aspect of the clavicle before forming a muscular arch over the supraclavicular nerve and passing laterally towards the trapezius and acromion. We recommend that in clinical instances of otherwise unexplained unilateral clavicular pain or tenderness, nerve compression from the supraclavicularis muscle must be borne in mind.

Sternalis muscle, what every anatomist and clinician should know

The sternalis muscle is a well documented but rare muscular variation of the anterior thoracic wall. It lies between the superficial fascia and the pectoral fascia and is found in about 8% of the population. It presents in several morphological variants both unilaterally and bilaterally and has no apparent physiological function. There is still much disagreement about its nerve supply and embryological origin. With the advent of medical imaging and thoracic surgery the clinical importance of this muscle has been re-emphasized. It has been implicated in misdiagnosis of breast masses on routine mammograms owing to its parasternal location and relative unfamiliarity among radiologists. When undetected before any thoracic surgery, it has the potential to interfere with and prolong such procedures. When present and detected preoperatively it can be used as a muscular flap in reconstructive surgeries of the breast and neck. This article will present the sternalis muscle with special emphasis on its morphology, homology, and clinical significance.

A morphological study of third head of biceps brachii in human cadavers with its clinical implications

Background: Muscular variations are relatively fewer when compared to vascular variations. A few muscles show extra heads of origin apart from their original heads. One such muscle which has extra heads of origin is biceps brachii (BB). Understanding of these extra heads is significant in handling injuries of the muscle and in tendon reconstruction operations. So, the aim of this study was to look for the incidence of the third head of the biceps brachii. Materials and Methods: The study was carried out on 24 cadaveric upper limbs. Dissection of the front of arm was done and the origin and insertion of the BB was looked. Any additional head if present was particularly looked for and photographed. Results: We found the three headed BB unilaterally in three male cadavers, one belonging to the left side and two to right side. The third head of BB originated near the insertion of the CB and at the origin of the brachialis in two cases and in both cases it goes and merges with the other two heads and insert into the posterior part of radial tuberosity. In one case it originates along with the long head of BB and its tendon goes and insert into the deep fascia of the arm. Conclusion : These all variations in the study should be known to the orthopedic surgeons during treatment of the bones fractures in this region because sometime the presence of third head may cause unusual bone displacement subsequent to fracture.

Bilateral Absence of Flexor Digitorum Superficialis Tendon of the Little Finger: Clinical Significance

The flexor digitorum superficialis (FDS/sublimis) is a flexor of the digits of the hand and has been reported to have varying degrees of agenesis. During routine cadaveric dissection for undergraduates at SRMS-IMS Bareilly, India, we observed bilateral absence of the FDS tendon to little finger in the upper limbs of a 45-year-old male cadaver. The muscle was normally supplied by a branch of median nerve in the forearm. Variants of the FDS muscle of the little finger have been reported in the literature. Proper knowledge of muscular variations is essential not only for anatomists but also for orthosurgeons, plastic surgeons and neurologists especially when evaluating possible tendon laceration/dysfunction. The FDS has been used as a motor for a wide variety of tendon transfer operations in the hand.

A Variant Accessory Belly of Extensor Indicis Muscle: An Anatomical Variation

Muscular variations of the extensor compartment of the forearm are generally encountered during surgical and dissection procedures. Additional bellies, extra tendons, and abnormal attachment are such reported variations. Knowledge of these kinds of variation are important for hand surgeons to plan the surgical procedure and modify their approach to that case, or the surgeon can take the advantage of these variations during muscle graft and tendon transplantation procedures. Here we report a case of an additional belly of the extensor indicis muscle. The additional belly arose from the interosseous membrane. Its tendon passed through the fourth compartment deep into the extensor retinaculum and divided into two tendinous slips on the dorsum of the hand. One of these slips attached to the ulnar side of the tendon of the extensor digitorum for the middle finger; the other slip was merged with fascia over the dorsum of the hand. The additional belly was supplied by the posterior interosseous nerve.

Sonographic diagnosis of anatomical variations associated with carpal tunnel syndrome

Bifid median nerve is an anatomic variation that occurs in about 18% of patients with symptoms suggestive of carpal tunnel syndrome and in about 15% of symptom-free subjects. Reversed palmaris longus is a rare anatomic muscular variation. The simultaneous presence of a bifid median nerve and a reversed palmaris longus has been very rarely described, usually during surgical exploration or in cadavers. We present two cases where ultrasound showed the presence of both abnormalities, allowing a correct diagnosis and influencing the treatment plan.

A rare muscular variation in the superficial region of the popliteal fossa

We found a rare muscular variation in the superficial region of the popliteal fossa in a 61-year-old Korean male cadaver whose cause of death was laryngeal carcinoma during routine dissection course for medical students. The muscle ran transversely between the medial head of the gastrocnemius muscle and the tendon of the long head of biceps femoris muscle, covering the neurovascular structures in the popliteal fossa. The muscle received its nerve supply from the tibial nerve. Based on its innervation, we speculated that the anomalous muscle might be a very specific type of variation related to the gastrocnemius tertius rather than another superficial muscle in the popliteal fossa.

Genetic variations in the myostatin gene (MSTN) in New Zealand sheep breeds

Myostatin, which is also known as growth and differentiation factor 8 (GDF8), acts as a negative regulator of skeletal muscle growth. Variation in the myostatin gene (MSTN) has been associated with variation in muscularity in many animals including sheep. Polymerase chain reaction-single strand conformational polymorphism (PCR-SSCP) analysis was used to investigate MSTN in a diverse range of sheep breeds including the New Zealand (NZ) Romney, Coopworth, Corriedale, Dorper, Perendale, Suffolk, Merino, Dorset Down, Poll Dorset, Texel and other NZ cross-bred sheep. A total of 28 nucleotide substitutions were identified from nucleotide c.-1199 in the promoter region to c.*1813 (based on NCBI GenBank accession number DQ530260) and including the well-described substitution c.*1232G>A (MSTN g+6223G>A). Of these 28 substitutions, 3 were located in the promoter region, 3 in the 5'UTR, 11 in intron 1, 5 in intron 2 and 5 in the 3'UTR. One substitution in exon 1 (c.101G>A) potentially results in an amino acid substitution of glutamic acid (Glu) with glycine (Gly) at codon 34. Ten of these substitutions have not been reported previously. The genetic variation revealed in this study suggests this gene is more variable than hitherto reported and provides a foundation for future research into how this variation affects muscle and growth traits.

Unilateral Third Head of Biceps Brachii with Associated Neurovascular Variants in both the Upper Limbs of a Single Cadaver

During routine undergraduate dissection in the upper extremities of a 65 years old male cadaver in the department of Anatomy at Dr. PSIMS & RF, coexistence of muscular and neurovascular variants were identified .Muscular variations included presence of additional head(third) of biceps brachii in the left arm, accompanied with medially positioned median nerve in relation to brachial artery bilaterally . Teres minor muscle was not identified and the origin of long head of triceps brachii extended upto the lateral border of scapula on the left side. Both the medial cutaneous nerves of arm and forearm arouse from a single trunk bilaterally. In the right limb the axillary artery showed only four branches instead of six branches, with common trunk for thoraco-acromial and lateral thoracic artery and common trunk for subscapular and posterior circumflex humeral artery. Knowledge of coexistence of these variations would of profound importance surgically and clinically, especially in limb injuries and surgical repairs. DOI: http://dx.doi.org/10.3126/ajms.v5i1.7391 Asian Journal of Medical Science Vol.5(1) 2014 pp.81-85

Investigation of the mechanical properties of the human crural fascia and their possible clinical implications

The mechanical properties of deep fasciae strongly affect muscular actions, development of pathologies, such as acute and chronic compartment syndromes, and the choice of the various fascial flaps. Actually, a clear knowledge of the mechanical characterization of these tissues still lacks. This study focuses attention on experimental tests of different regions of human crural fascia taken from an adult frozen donor. Tensile tests along proximal-distal and medial-lateral direction at a strain rate of 120%/s were performed at the purpose of evaluating elastic properties. Viscous phenomena were investigated by applying incremental relaxation tests at total strain of 7, 9 and 11% and observing stress decay for a time interval of 240s. The elastic response showed that the fascia in the anterior compartment is stiffer than in the posterior compartment, both along the proximal-distal and medial-lateral directions. This result can explain why the compartment syndromes are more frequent in this compartment with respect to posterior one. Furthermore, the fascia is stiffer along the proximal-distal than along medial-lateral direction. This means that the crural fascia can adapt to the muscular variation of volume in a transversal direction, while along the main axis it could be considered as a structure that contributes to transmitting the muscular forces at a distance and connecting the different segments of the limb. The stress relaxation tests showed that the crural fascia needs 120s to decrease stress of 40%, suggesting a similar time also in the living so that the static stretching could have an effect on the fascia.

Occlus-o-Guide®versus Andresen activator appliance: neuromuscular evaluation

BackgroundThe aim of the present study was to assess the muscular variations at the electromyography (EMG) level for the anterior temporalis muscles and masseter muscles during treatment with Occlus-o-Guide® and Andresen activator appliances.MethodsEighty-two patients (35 males and 47 females) aged between 8 and 12 years (mean age, 10.5 ± 0.8 years) participated in the study. Fifty patients underwent treatment with an Occlus-o-Guide® and 32 patients with an Andresen activator. All patients underwent EMG examination using a Freely EMG (De Gotzen, Legnano, Italy) and surface bipolar electrodes when the appliances were worn for the first time (T0), and after 6 months (T1) and after 12 months (T2) of appliance use.ResultsStatistical analysis showed that both at T0 and T2, the percent overlapping coefficient (POC) of the anterior temporalis muscles was not statistically different between the appliance groups. At T0, the POC of the masseter muscles was significantly lower for the Andresen appliance as compared to the Occlus-o-Guide® (p = 0.02), while at T2 this significance was lost.ConclusionsAt insertion of an appliance, all patients show neuromuscular balance that does not correspond to orthognathic occlusion. Both appliances work by creating muscular imbalance. With the appliances in situ, EMG responses were generally analogous for the Occlus-o-Guide® and the Andresen activator; however, the imbalance was greater and the recovery of the orthological muscular balance was slower in patients under treatment with the Andresen activator as compared to those with the Occlus-o-Guide®.

The sternalis muscle and its clinical significance

The sternalis muscle is a well documented but rare muscular variation of the anterior chest wall. It lies between the superficial fascia and the pectoral fascia, and is found in 3–6% of the population. It presents in varied morphological variants both in unilateral and bilateral fashion and has no apparent physiological function. Much disagreement still exists about its nerve supply and embryological origin. With the advent of medical imaging and thoracic surgery the clinical importance of this muscle has been re‐emphasized. The sternalis muscle has been implicated in misdiagnosis of breast masses on routine mammograms due to its parasternal location and relative unfamiliarity with radiologists. When undetected prior to any thoracic surgery, it has the potential to interfere with and prolong such procedures. When present and detected it can be used as a muscular flap in reconstructive surgeries of the breast and neck. The aim of this study was to conduct a meta‐analysis on the sternalis muscle with special emphasis on its anatomy, embryology, clinical implications and potential iatrogenic complications.Grant Funding Source: SGU

Analysis of functional electrical stimulation parameters by muscular contraction time and knee joint angular variation

In the present study, five FES profiles were compared in order to find the best combination of activeperiod and burst frequency that might artificially sustain muscle contraction for the longest time with the lowest knee joint variation. Spinal cord injured volunteers (N=10) participated in this study. The frequency of each FES profile was 1 kHz with variable pulse active period (100 μs or 200 μs) and pulse inactive period (900 μs or 800 μs). The setup burst frequencies had either 50 Hz (3 ms active time and 17 ms rest time) or 70 Hz (3 ms active time and 11 ms rest time). The best results were obtained to FES profiles P2 (burst frequency of 70 Hz and pulse active period of 100 μs), P3 (burst frequency of 50 Hz and pulse active period of 200 μs) and P4 (burst frequency of 70 Hz and pulse active period of 200 μs). In order to maintain the SCIV’s knee angle with minimal variation, the best results occurred with the application of P2, P3 and P4 FES profiles.

English

Biceps brachii is a double headed muscle. In terms of number and morphology of its head, it is one of the most variable muscles in the human body. Most common variation is third head, but four, five or even seven heads have been reported. In the present case report third head of biceps brachii was found on the flexor compartment of left arm of an adult female cadaver .The third head of biceps brachii originated from the anteromedial surface of the humerus below the insertion of coracobrachialis and which descended and merged with the other two heads to form common tendon and was inserted on to the radial tuberosity . Third heads might be significant in producing the strong flexion as well as supination of forearm. They may cause compression of neurovascular structures because of their close relationship to brachial artery and median nerve. Variant biceps brachii may confuse a surgeon who performs procedures on the arm and may lead to iatrogenic injuries. The surgeons and traumatologists have to keep such muscular variations in mind.

Unusual unilateral multiple muscular variations of back of thigh

During routine cadaveric dissection for the undergraduate students in the Department of Anatomy, we noted multiple muscular variations in a middle-aged male cadaver. All the variations were seen at the back of thigh (flexor compartment) of right lower limb. An anomalous muscle of 17 cm length with average width of 1.5 cm. was inserted to the semitendinosus, a third head of biceps femoris of 6.5 cm length with an average width of 3.5 cm was inserted to the semitendinosus and ununited short and long heads of biceps femoris, both heads were inserted to the head of fibula. To the best of our knowledge, such muscular variations have not been reported in the recent medical literature. A comprehensive knowledge of such rare anatomical variations will be important for surgeons and Traumatologists as this might cause compression of the sciatic nerve.

A rare muscular variation: the third of the rhomboids

During superficial back dissection of a 72-year-old male cadaver, an interesting aberrant muscle was observed bilaterallybelow the lower border of the rhomboideus major. The unusual muscle arose by a thin aponeurosis from the spinousprocesses of the mid-thoracic vertebrae and was attached laterally to the lowest part of the medial border of the scapula.Because of its characteristics the authors proposed the term – the third rhomboid (m. rhomboideus tertius)

Extensor pollicis et indicis communis or extensor indicis radialis muscle

Anatomical variations of the fingers extensor tendons are not uncommon and have been described by several authors. Participation of intertendinous band of fascia in this kind of variation can change muscle functionality. However, this element is scarcely described in the literature. In this case report, we describe the finding of an accessory tendon located between the extensor digitorum communis muscle tendon, destined for the index finger, and the extensor pollicis longus tendon. In an anatomical analysis, we observed a connection between the radial portion of the accessory tendon and the ulnar portion of the extensor pollicis longus tendon by intertendinous fascia. This finding corresponds anatomically to the supernumerary muscle denominated extensor indicis radialis, but due to the fascial connections observed with the extensor pollicis longus, this muscle would behave functionally as a supernumerary muscle denominated extensor pollicis et indicis communis. This report suggests that participation of fascia in muscular variation in this anatomical segment is essential to establish the correct morpho-functional denomination of muscular variants.

A STUDY ON MORPHOLOGY OF THE BICEPS BRACHII MUSCLE

AbstractThe anatomical variations and abnormalities of the muscles of the upper limb have become significant because of new imaging techniques, such as computed tomography and magnetic resonance imaging. Among the three muscles of the anterior compartment of the arm, a very uncommon anomaly of the biceps is having three or more heads. Knowledge of the existence of the three headed or four headed biceps brachii may become significant in preoperative diagnosis and during surgery of the upper limb. The present study was undertaken to observe the anomalous origin, insertion and the incidence of three or more heads biceps brachii in the adult human cadavers. This study was carried out on 24 human cadavers at Dr. Pinnamaneni Siddhartha institute of medical sciences & research foundation (Dr. PSIMS & R.F) Gannavaram; Krishna Dist; A.P. Variant biceps brachii may cause compression of neurovascular structures because of their close relationship to brachial artery and median nerve. The surgeons and traumatologists have to keep such muscular variations in mind.

Muscle Mass Scaling in Primates: An Energetic and Ecological Perspective

Body composition is known to vary dramatically among mammals, even in closely related species, yet this issue has never been systematically investigated. Here, we examine differences in muscle mass scaling among mammals, and explore how primate body composition compares to that of nonprimate mammals. We use a literature-based sample of eutherian and metatherian mammals, and combine this with new dissection-based data on muscularity in a variety of strepsirrhine primates and the haplorhine, Tarsius syrichta. Our results indicate an isometric scaling relationship between total muscle mass and total body mass across mammals. However, we documented substantial variation in muscularity in mammals (21-61% of total body mass), which can be seen both within and between taxonomic groups. We also found that primates are under-muscled when compared to other mammals. This difference in body composition may in part reflect the functional consequences of arboreality, as arboreal species have significantly lower levels of muscularity than terrestrial species.