Spatial distribution of muscle fibers in a lumbrical muscle of the rat

The spatial distributions of two differnt populations of muscle fibers were measured in cross-sections taken from the mid-belly of adult 4DL muscles. Muscle fibers belonging to a single motor unit (identified by glycogen depletion) were distributed randomly in most muscles. Muscle fibers which contained slow myosin (identified immunohistochemically) were distributed nonrandomly, being evenly distributed throughout most of the muscle cross-section, but excluded from the edge of the muscle. Interpreted from a developmental perspective, the results are consistent with the proposals that slow myosin-containing fibers in the adult represent the original population of primary myotubes, and that the adult pattern of motor unit fiber type is achieved by synapse elimination from mismatched fibers rather than by conversion of fiber type. © 1993 Wiley-Liss, Inc.     

Three-headed reversed palmaris longus muscle: a case report and review of the literature

The palmaris longus muscle (PLM) is extremely variable both in number and form. We present the first reported case of three-headed reversed PLM in a 36-year old woman. The relevant literature is reviewed. Variations of the muscles of the forearm and specifically the PLM are not uncommon. However, different rates are given for the types and agenesis of PLM. In one study, the incidence of agenesis was 12.8% and other anomalies were 9%. 15 cases of reversed PLM have been reported in the literature. In our case, the three-headed PLM was resected. The patient’s symptoms resolved and at 1-year follow-up she remains symptom-free.     

Neurovascular anatomy and variation in the fourth, fifth, and sixth intercostal spaces in the mid-axillary line: a cadaveric study in respect of chest drain insertion

Chest drains are normally inserted in the fifth intercostal space in the mid-axillary line. The classical technique for chest drain insertion involves locating the drain in an interspace just superior to the inferior rib, so as to avoid the neurovascular bundle. While teaching thoracic wall anatomy on cadavers, considerable variation was noted in the position of the neurovascular bundles, frequently lying well away from the generally accepted subcostal groove. We endeavoured to perform a comprehensive cadaveric study of the neurovascular relationships in the mid-axillary line in the fifth and adjacent spaces to try to describe a 'Safe Zone' for drain insertion to minimise damage to associated structures. The idea that the neurovascular bundle is safely protected in the subcostal groove should be dispelled, as should the concept that there is nothing to damage in the zone immediately superior to the inferior rib. Clinicians should be aware that the Safe Zone is narrower than hitherto appreciated and should be between 50-70% of the way down an interspace to avoid the variably positioned superior intercostal neurovascular bundle and the inferior collateral artery.     

An accessory belly of the abductor digiti minimi muscle: a case report and embryologic aspects

Accessory fasciculi of the hypothenar muscles have been involved in vascular and nerve compressions. During a routine dissection an accessory belly of the abductor digiti minimi muscle arising from the tendon of the palmaris longus muscle was found in the lower third of the forearm. The accessory fasciculus ran through Guyon’s canal enclosing the ulnar nerve and vessels. It was attached by means of two tendons where the fibres of the abductor digiti minimi muscle ended in a single pennate form. This anatomic variation was associated with a marked reduction of the caliber of the fourth tendon of the flexor digitorum superficialis muscle and a split of the median nerve. The nerve supply arose from the ulnar nerve. A fibrous band originating from this accessory muscular belly was found covering the median nerve. Based on the development of muscles and fibrous structures within the hand and forearm, as well as on our results, we consider the present anomalies as an unusual persistence of an undifferentiated group of mesenchymal cells. These belong to the superficial muscular anlagen layer of the hand, just between the flexor digitorum superficialis muscle blastema (which has the capacity of migration) and that for the abductor digiti minimi muscle.     

The relationship of nerve to myoblasts and newly-formed secondary myotubes in the fourth lumbrical muscle of the rat foetus

Summary The formation of normal numbers of skeletal muscle fibres depends on functional innervation of the muscle before and during the period of secondary myotube formation, but little has been known about the physical relationship between nerve terminals and the myoblasts and secondary myotubes over the critical period. This paper reports the results of a serial-section electron microscopic study of the IVth lumbrical muscle of the rat hindlimb, studied on embryonic day 20 (E20), a time when all secondary myotubes are less than 24 h old, and new ones are rapidly forming. Most myoblasts lying within the endplate region of the muscle received some direct neural contact; in almost all cases, the contact originated from an extension of a differentiated nerve terminal present at the endplate of an adjacent primary myotube. At six of 15 neural contact sites on myoblasts, primitive synaptic specialization was present. The newly-formed secondary myotubes were also directly, although sparsely, innervated in nine of ten instances. One secondary myotube was never seen to be innervated, despite extensive serial tracing. Nerve terminals passing to secondary myotubes were also principally derived from the innervation zone of the earlier-formed primary myotubes. Primary myotubes were profusely innervated by multiple axons. The results suggest that most nerve terminals are initially accommodated on the primary generation of myotubes, but progressively transfer to pre-fusion myoblasts or to secondary myotubes as these appear. In general, very young secondary myotubes are innervated by only a single axon, rather than being polyneuronally innervated. The existence of some secondary myotubes which lack any direct innervation suggests that intimate nerve contact may not be obligatory for formation of new secondary myotubes.     

The effects of the communicating branch between medial and lateral plantar nerves on the innervations of the foot lumbrical muscles

Introduction

The communicating branches between the medial (MPN) and lateral (LPN) plantar nerves aren’t frequently observed in relation to the innervation of the foot muscles in previous studies. In this study, the number and localization of the communicating branch on the innervations of foot muscles were evaluated to open a new sight considering the innervations of lumbrical muscles.

The pattern of arrangement of the lumbrical muscles in an African population

The pattern of arrangement of the lumbrical muscles in the hand of an African population was studied. Sixty-four upper limb specimen from 32 male cadavers between the ages 18 and 40 were obtained from the Department of Anatomy, University of Calabar, Nigeria were used. Ethical approval was granted by the Ethics Committee of the University, and each of the limbs of the cadavers was labeled. Observations were grouped as A, B, C, D, and E and their incidence calculated using simple percentages. Group A constituted 50% and represented the standard pattern. In this group, the first and second bellies of lumbrical muscles arose each from the radial sides of the corresponding flexor digitorum profundus (FDP) tendons, while the third and fourth bellies of the lumbrical muscles arose each from the contiguous sides of the FDP tendons of the middle and ring fingers, and the ring and little fingers, respectively. All the bellies were inserted to their corresponding sides in the radial part of the dorsal digital expansion. Groups B and E constituting 12.5 and 6.25%, respectively, presented single origins and insertions in all the four bellies of the lumbrical muscles. Groups C and D constituting 18.75 and 12.5%, respectively, showed double origins in the third belly of the lumbrical muscle, with the first, second, and fourth having single origins. In conclusion, our study showed variations already reported, and peculiar pattern of lumbrical muscle arrangement in a single hand. Therefore, this study is of anatomical, anthropological, and clinical importance.     

Selectivity of voluntary finger flexion during ischemic nerve block of the hand

During ischemic nerve block of an extremity the cortical representations of muscles proximal to the block are known to expand, increasing the overlap of different muscle representations. Such reorganization mimics that seen in actual amputees. We investigated whether such changes degrade voluntary control of muscles proximal to the block. Nine subjects produced brief, isometric flexion force selectively with each fingertip before, during, and after ischemic block at the wrist. We recorded the isometric force exerted at the distal phalanx of each digit, along with electromyographic (EMG) activity from intrinsic and extrinsic finger muscles. Despite paralysis of the intrinsic hand muscles, and associated decrements in the flexion forces exerted by the thumb, index, and little fingers, the selectivity of voluntary finger flexion forces and of EMG activity in the extrinsic finger muscles that generated these forces remained unchanged. Our observations indicate that during ischemic nerve block reorganization does not eliminate or degrade motor representations of the temporarily deafferented and paralyzed fingers.     

Unusual variation of a third head of the biceps brachii muscle

A human cadaver was studied which presented a biceps brachii with three heads of origin in the left arm. The third or humeral head presented an unique area of insertion into the bicipital aponeurosis (lacertus fibrosus).     

Strain distribution on a finger link: a static simulation study

Functional prosthetics hands which have the ability to help amputees perform tasks in daily life have been developed over many years. These hands need a control system which is fed information from sensors mounted on a prosthetic hand and human–machine interface. A variety of sensors therefore been developed for the prosthetic hand to measure fingertip force, joint angle (position), object slip, texture and temperature. However, most of the strain/stress sensors are attached to the fingertip. In this paper, the potential positions for strain sensors on the side of the finger link of the prosthetic hand are investigated that, in the future, will allow for force control in a lateral or key grip. With modified links of a Southampton Hand, some promising positions for strain sensors have been determined. On some of the links, the strain sensor can be used as an indicator to show the angle of the finger during a curling operation.     

13C MRS reveals a small diurnal variation in the glycogen content of human thigh muscle

There is marked diurnal variation in the glycogen content of skeletal muscles of animals, but few studies have addressed such variations in human muscles. ¹³C MRS can be used to noninvasively measure the glycogen content of human skeletal muscle, but no study has explored the diurnal variations in this parameter. This study aimed to investigate whether a diurnal variation in glycogen content occurs in human muscles and, if so, to what extent it can be identified using ¹³C MRS. Six male volunteers were instructed to maintain their normal diet and not to perform strenuous exercise for at least 3 days before and during the experiment. Muscle glycogen and blood glucose concentrations were measured six times in 24 h under normal conditions in these subjects. The glycogen content in the thigh muscle was determined noninvasively by natural abundance ¹³C MRS using a clinical MR system at 3 T. Nutritional analysis revealed that the subjects' mean carbohydrate intake was 463 ± 137 g, being approximately 6.8 ± 2.4 g/kg body weight. The average sleeping time was 5.9 ± 1.0 h. The glycogen content in the thigh muscle at the starting point was 64.8 ± 20.6 mM. Although absolute and relative individual variations in muscle glycogen content were 7.0 ± 2.1 mM and 11.3 ± 4.6%, respectively, no significant difference in glycogen content was observed among the different time points. This study demonstrates that normal food intake (not fat and/or carbohydrate rich), sleep and other daily activities have a negligible influence on thigh muscle glycogen content, and that the diurnal variation of the glycogen content in human muscles is markedly smaller than that in animal muscles. Moreover, the present results also support the reproducibility and availability of ¹³C MRS for the evaluation of the glycogen content in human muscles. Copyright © 2015 John Wiley & Sons, Ltd.     

Finger skin cooling on contact with cold materials: an investigation of male and female responses during short-term exposures with a view on hand and finger size

This study investigated the independent effects of hand anthropometry and gender upon contact cooling responses. Subjects were selected for matching hand/finger size between genders, with equal variation between individuals of each group. Fourteen volunteers (7 male, 7 female) participated, touching blocks of aluminium and stainless steel using the first phalanx of the index finger with a contact force of 1.0 N and 9.8 N, at surface temperatures of –2°C and –10°C. Conditions were selected in order to elicit varying rates of skin cooling upon contact. Contact temperature (T _C) of the finger-pad was measured over time using a T-type thermocouple. Overall, no significant difference was found between the cooling responses of males and females. In order to investigate whether differences in hand anthropometry correlated with contact cooling response, a multiple regression approach was used. Analyses of the residual variance in contact cooling data, after the effects of material type, surface temperature and finger contact force had been accounted for, showed that, under slow cooling conditions (>45 s to reach T _C=1°C), hand size correlated significantly with contact cooling response only when represented by index finger volume (P<0.05), but gender did not. Whilst under fast cooling conditions (<25 s to reach T _C=1°C), hand size did not correlate significantly with contact cooling response at all, but gender had a significant effect (P<0.001). Under slow cooling conditions, a larger finger (and in most cases hands) provides a higher heat content, thus giving a slower skin cooling speed. Under fast cooling conditions, the significantly longer time required for males to reach a T _C of 1°C, despite matching hand and finger size, is attributed to higher epidermal insulation provided by the thicker stratum corneum, combined with the higher starting skin temperature observed in the slightly cool environment.     

Anatomic study of the tendinous insertion lamina of the temporalis muscle

Lengthening temporalis myoplasty is indicated in long-standing and congenital facial paralysis. Its principle is the transfer of the coronoid tendinous insertions onto the lip and the nasolabial fold. Knowledge of the anatomy of this strong and wide tendon is necessary for successful use of its anatomic advantages. A study on 10 cadavers (20 temporalis muscles) confirmed the surgical anatomy found during lengthening temporalis myoplasty procedures: the strong tendon, when freed from the coronoid process, is 4–6 cm wide.     

手内在肌的血供与肌瓣设计的解剖学基础

目的:研究手内在肌的血供为肌瓣的设计提供解剖学基础。方法:(1)红色乳胶灌注的上肢标本20侧,解剖并观测手内各动脉的起始部位,测量其管径及其走行,分支、分布情况等。(2)动脉灌注明胶-氧化铅混悬液的新鲜成人整尸标本10具,解剖取下各手内在肌,拍摄X线片。利用Photoshop与ScionImage对X线影像进行分析处理,观测营养动脉在肌内的分布、分型及彼此间的吻合情况等。结果:18块手内在肌共有(58.0±5.9)支动脉供血,平均(3.0±1.0)支,平均外径及其供血区域的长度与宽度分别为:(0.8±0.2)mm,(2.2±0.4)cm,(1.0±0.2)cm。结论:(1)手内在肌的血运丰富,其起、止点处的血管网亦丰富,具备切取肌瓣或肌骨(膜)瓣的解剖学基础。(2)其中有9块肌肉的主供血动脉之管径较粗大且恒定,易于解剖与取瓣,可供临床选用。     

Anatomic variations in a cleft hand of an elder cadaveric specimen

Cleft hand is a rare and complex malformation in which the central part of the hand is missing. Since the nineteenth century, a very small number of dissections in cleft hand have been reported and very few reports describe the soft-tissue abnormalities. We report a case of an elderly cadaveric specimen with bilateral cleft hand. X-ray, CT-scan with 3D reconstruction and dissection were performed on the right hand and forearm. On both the sides, we noted the absence of the index, middle and ring finger. Malformation and degenerative arthrosis at the carpal bones level have been identified. The flexor and extensor tendons of the absent fingers fuse with one another over the end of the remaining carpal bones, forming a radial and an ulnar tendinous plexus and two tendon loops. Data concerning intrinsic muscles, vessels and nerves are entirely recorded. Soft-tissue abnormal distribution is due to the abnormal bony configuration. Correction of the bone abnormalities does not resume the surgical treatment of a cleft hand. Hand surgeons need to be aware of the soft-tissue disorders and their surgical implications.     

Clinical aspects of muscle imbalance in the hand due to ulnar nerve lesions

Summary This study deals with the anatomical and clinical bases of the thumb-index finger grip, emphazising not only its general importance, but also its ergonomie role. A classification according to the different functions of two muscular groups (extrinsic and intrinsic), with special reference to muscular imbalance due to ulnar nerve lesions is proposed.After some general considerations on the function of the hand practical conclusions are drawn.

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Aspects cliniques du déséquilibre musculaire de la main après lésion du nerf cubitalEssai de classification de la préhension pouce-index

Résumé Cette étude rapporte les bases anatomocliniques de la préhension pouce-index, insistant, non seulement sur ses aspects généraux, mais aussi, sur son rôle ergonomique. Une classification permettant d'apprécier les différentes fonctions des deux groupes musculaires (intrinsèques et extrinsèques), insistant surtout sur le déséquilibre musculaire après lésion du nerf cubital, est proposée. Après des considérations générales sur l'importance de la main, des conclusions pratiques sont tirées.