Accepted : 27 April Published : 15 May Issue Date : November Anyone you share the following link with will be able to read this content:. Sorry, a shareable link is not currently available for this article. Provided by the Springer Nature SharedIt content-sharing initiative. Skip to main content. Search SpringerLink Search. Abstract Introduction Double innervation of the brachialis muscle has been previously reported in anatomical studies.
Materials and methods 1 The existence, origin and pattern of distribution of a branch from the radial nerve to brachialis were dissected on 20 cadaveric arms. Conclusions Variations in the relative percentage of innervation from the radial nerve could be due to the different sizes and shapes of this branch.
References 1. Louis, Mosby, pp — 5. New York, Oxford University Press, pp Orthop Clin North Am, pp — Clin Anat 24 4 — Google Scholar Anat Anz — Google Scholar Longman, Madrid, pp — Google Scholar Download references.
Conflict of interest The authors declare that they have no conflict of interest. Bianchi Authors M. Bendersky View author publications. View author publications. Rights and permissions Reprints and Permissions. The presence or absence of the muscular branches of the radial nerve to the brachialis and their number, length, site of entry into the brachialis and the distance from the lateral epicondyle to the site of emergence of these branches were studied.
The average length of the muscular branches was about 4. Surgical dissection should be done through the mid muscle belly of the brachialis muscle to preserve the musculocutaneous nerve on its medial and radial nerve on its lateral border.
Therefore, this study will be useful to the orthopaedic surgeons in avoiding iatrogenic injury to the radial and the musculocutaneous nerves. Introduction Fractures of the shaft of the humerus constitute three percent of all the fractures and sometimes, may require surgical intervention. This requires an adequate knowledge about the anatomy of the humerus, the muscles and the neurovascular structures in the arm.
The brachialis is the workhorse of elbow flexion 1 , with two different views about its innervation. The common view is that it has a dual innervation from the musculocutaneous nerve on the medial part and the radial nerve on the lateral part 2 , 3 , 4.
Another view states that it is supplied only by the musculocutaneous nerve 5. These nerves are at a risk of injury, either during a fracture or during the surgical reduction, unless the brachialis is split longitudinally through the mid muscle belly. Hence , this study was carried out tostudy the nerve supply to the brachialis and its importance in the surgical treatment of the fractures of the shaft of the humerus. Material and Methods The materials which were used in this study consisted of fifty upper limbs of both the sides.
The brachialis muscle was exposed by routine dissection. The radial nerve was exposed from its origin from the posterior cord of the brachial plexus, then in the spiral groove and beyond it upto the lateral epicondyle. The following parameters were studied and observed: The presence or absence of the muscular branches of the radial nerve to the brachialis and the number of muscular branches of the radial nerve to the brachialis were recorded.
The results were statistically analyzed. Results 1. Discussion The dual innervation of the brachialis can be explained by its development. The limb musculature is observed in the seventh week of development as a condensation of the mesenchyme near the base of the limb buds.
With the elongation of the limb buds, the muscle tissue splits into the flexor and the extensor components 6 which are innervated by the ventral and dorsal rami of the spinal nerves of the corresponding segment. Each ventral ramus gives a ventral and a dorsal branch. Thus, the radial nerve which supplies the extensor musculature, is formed by a combination of the dorsal segmental branches, whereas the ulnar and the median nerves which supply the flexor musculature are formed by a combination of the ventral branches 7 , 8.
Though the brachialis is a flexor, the radial nerve gives a minor branch C7 to the brachialis muscle. This is explained by the derivation of the lateral portion of the muscle from the extensor premuscle mass 9. The double nerve supply of the brachialis by the musculocutaneous nerve and the radial nerve has been generally explained to be the result of the fusion of two muscular primordia, the extensor pre-muscular mass and the flexor pre-muscular mass.
There is another view that the brachialis muscle has only one origin from the ventral pre-muscular mass. The branch from the radial nerve derives from the anterior division of the brachial plexus and it uses the radial nerve only as a route to the brachialis muscle by unknown mechanisms The radial nerve branch is proprioceptive. The brachialis muscle contains a great deal of mechanoreceptors and thus, coupled with its innervation pattern, it plays a key role in the kinesthetic awareness and the proprioception concerning the elbow Mahakkanukrauh 10 , in his cadaveric study which was done in specimens in an east Asian Thai population, reported that A cadaveric study which was done on 70 specimens of the Indian population showed In a cadaveric study which was done on 70 specimens, the radial nerve branch to brachialis was found to pierce the muscle in the lower one third in The radial nerve contributed one to three branches to the brachialis in 10 out of 20 specimens In our study also, the radial nerve branches to the brachialis was one to three in number.
The variation in the branch number may be due to the differences in the muscle architecture, the number of joints which a muscle crosses, and the variations which are in need for the isolated control of different parts of a common muscle belly Linell 14 , in , studied the levels of the muscle innervations for the radial nerve with respect the lateral epicondyle as the bony landmark.
Linell measured the ratios of the innervation distances to the forearm length. The muscular branches to the brachialis fromthe radial nerve arose 24 cms from the tip of the acromion. The forearm distance between the acromion and lateral epicondyle was considered as 30cms.
Our study has made the actual measurements of the muscular branches of the radial nerve to the brachialis, which showed an average of 4. The radial nerve branch to the brachialis in Our study showed that all the branches entered with a relatively straight course into the brachialis. In the operative treatment of humeral shaft fractures, the radial nerve may be injured during the reduction of the fracture fragments or the application of plates and screws Conclusion Summary and Conclusion The present study has revealed that the radial nerve invariably gives branches to the brachialis, which enter the muscle on theinferolateral border.
They vary from one to three in number. The average length of these muscular branches is 4. They emerge at a distance which ranges from 4. Key Message The constancy of the radial nerve supply is controversial.
It has been quoted in some of the literature, that the brachialis is supplied only by the musculocutaneous nerve 5. Knowledge about the presence, the site of entry and the length of the radial nerve branches to the brachialis and their distance from a fixed bony landmark, helps surgeons in preserving the dual innervation of the brachialis during surgical reduction for the fractures of the shaft of the humerus. Acknowledgement I thank The Head of the Dept. Moore KL. Clinically Oriented Anatomy, 5th edition.
Williams et al. London: Churchill Livingstone. A study on the radial supply of the human brachialis muscle. Anat Rec ; Last RJ. Compartment syndrome is a surgical emergency that requires an immediate fasciotomy. A fasciotomy is a surgical procedure where an incision is made in the skin, and blunt dissection is conducted to reach the fascia surrounding all the compartments of the forearm. The fascia is then cut to release the tension created by the swelling.
Understanding the innervation of the muscles of the forearm and the action of the forearm muscles is important clinically. When there is a lesion to a nerve, the normal function of the muscles that specific nerve innervates will be abnormal. This abnormality is deducible through proper history and physical exam, which allows the physician to provide treatment effectively.
Journal of wrist surgery. American journal of roentgenology. Turkish neurosurgery. Hand clinics. Free Review Questions. Introduction The nerves of the forearm are complex due to the various nerve branches and the muscles that reside in the upper extremities.
Structure and Function The entire upper limb consists of the shoulder, arm, forearm, and hand. Embryology The entire human body derives from either ectoderm, mesoderm, or endoderm.
Blood Supply and Lymphatics Blood Supply The radial and ulnar arteries supply most of the blood to the forearm. Lymphatic The majority of lymphatic drainage from the upper limb drains into the axillary lymph nodes.
Nerves The brachial plexus carries the majority of the innervation to the forearm; however, a small amount of sensory innervation comes from the medial antebrachial cutaneous nerve. Medial Antebrachial Cutaneous Nerve The medial antebrachial cutaneous nerve forms as a branch of the medial cord from nerve roots C8-T1. Radial Nerve The radial nerve forms from the C5-T1 nerve roots. Median Nerve The median nerve forms from the C5-T1 nerve roots.
Ulnar Nerve The ulnar nerve forms from the C8-T1 nerve roots. Physiologic Variants The musculocutaneous nerve may be bilaterally absent; the median nerve can innervate muscles that are usually innervated by the musculocutaneous nerve or a portion of the lateral cord of the brachial plexus. Surgical Considerations In surgery, knowledge of the anatomy of the forearm nerves is crucial when it comes to repairing or reconstructing boney or muscular defects.
Clinical Significance Damage to nerves that supply the forearm could originate anywhere along the brachial plexus. Click Image to Enlarge Muscles and Arteries of the right forearm and hand, Biceps, Brachial Artery, Racial recurrent, Brachioradialis, Pronator teres, Flexor carpi radialis, Palmaris longus, Flexor digitorum sublimis, Flexor carpis, Extensor pollicis brevis, Superficial volar, Abductor pollicis brevis, Adductor pollicis transversus, Abductor digiti quinti, Flexor digit quinti brevis, Yellow lines represent nerves.
Contributed by Gray's Anatomy Plates. Feedback: Send Us Your Comments. Cambridge University Press. Read it at Google Books - Find it at Amazon 5. Susan Standring. Gray's Anatomy. ISBN: 6. Robert H. Whitaker, Neil R. Instant Anatomy. ISBN: Related articles: Anatomy: Upper limb. Promoted articles advertising. Figure 1: radial nerve Figure 1: radial nerve.
Figure 2: brachial plexus Figure 2: brachial plexus. Figure 3: at the axilla Figure 3: at the axilla. Figure 4: in the spiral groove Figure 4: in the spiral groove. Figure 5: lateral intermuscular septum Figure 5: lateral intermuscular septum. Figure 6: arm anatomy Gray's illustration Figure 6: arm anatomy Gray's illustration.
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