The Branching and Innervation Pattern of the Radial Nerve in the Forearm: Clarifying the Literature and Understanding Variations and Their Clinical Implications

Background: This study attempted to clarify the innervation pattern of the muscles of the distal arm and posterior forearm through cadaveric dissection. Methods: Thirty-five cadavers were dissected to expose the radial nerve in the forearm. Each muscular branch of the nerve was identified and their length and distance along the nerve were recorded. These values were used to determine the typical branching and motor entry orders. Results: The typical branching order was brachialis, brachioradialis, extensor carpi radialis longus, extensor carpi radialis brevis, supinator, extensor digitorum, extensor carpi ulnaris, abductor pollicis longus, extensor digiti minimi, extensor pollicis brevis, extensor pollicis longus and extensor indicis. Notably, the radial nerve often innervated brachialis (60%), and its superficial branch often innervated extensor carpi radialis brevis (25.7%). Conclusions: The radial nerve exhibits significant variability in the posterior forearm. However, there is enough consistency to identify an archetypal pattern and order of innervation. These findings may also need to be considered when planning surgical approaches to the distal arm, elbow and proximal forearm to prevent an undue loss of motor function. The review of the literature yielded multiple studies employing inconsistent metrics and terminology to define order or innervation.

Clinical Anatomy for the Innervated Pattern and Boundary of the Subdeltoid Bursa

The aim of this study was to accurately identify the distribution of sensory nerve branches running to bursa with mesoscopic dissection and boundaries following the injection of gelatin into the bursa. Eighteen shoulders of 11 Korean soft cadavers (average age, 65 years; age range, 43 - 88 years) were dissected. The most prominent point of greater tubercle of the humerus (GT) was used as a reference point. The horizontal line passing through GT was used as the x-axis while the vertical line passing through the GT was used as the y-axis. Average distances of the anterior, posterior, superior, and inferior from the GT were 1.9±0.6, 2.4±1.3, 2.1±0.7, and 3.2±1.5 cm, respectively. In 15 cases of 18 shoulders, the anterior branch of the axillary nerve was distributed to the subdeltoid bursa that was running posteriorly. The muscular branch of the anterior and middle parts of the deltoid was distributed to the branch of nerve that was running into the subdeltoid bursa. A branch of the posterior cord of brachial plexus was distributed to the subdeltoid bursa that was running anteriorly in three cases. Most of the branches of the axillary nerve were distributed into the posterolateral area. The branches of the posterior cord of brachial plexus were distributed in the anterolateral area. These results might be useful for preventing residual pain on the anterior shoulder region following an injection for the relief of shoulder pain.

A study on variations of branching patterns of median nerve in the carpal tunnel

Background & aims: The carpal tunnel, located on the palmar surface of the wrist, is a common site of median nerve compression. The median nerve, on passing through the carpal tunnel, divides into lateral and medial branches. The lateral branch then gives off proper palmar digital branches to the thumb and the radial aspect of the index finger, and a recurrent muscular branch to the thenar muscles. The recurrent muscular branch shows different types of variations of the median nerve. Also, there are other variations of the median nerve in the carpal tunnel. These variations greatly influence the symptoms, as well as the treatment of the carpal tunnel syndrome. So, the present work is carried out to study the variations of branching patterns of median nerve in the carpal tunnel. Materials and methods: 40 wrists [20 right and 20 left] from 20 formaldehyde fixed human perinatal fetuses of 34 - 38 weeks of gestation were dissected in the Department of Anatomy, Gauhati Medical College and Hospital, Guwahati. Due ethical clearance was obtained from the Institutional Ethical Committee, Gauhati Medical College and Hospital, Guwahati. Results: In the present study, 24 [66.7%] hands [11 right and 13 left] showed extraligamentous and 12 [33.3%] hands [8 right and 4 left] showed transligamentous variety of thenar branch of median nerve. Also, 4 [10%] hands showed accessory thenar branch of median nerve, all of which took origin within the flexor retinaculum. The comparisons of numbers of variations of thenar branch of median nerve between right and left hands were found to be statistically non significant [P > 0.05]. Conclusion: A detailed knowledge of the median nerve variations in the carpal tunnel is required for successful diagnosis and treatment of the carpal tunnel syndrome and its complications.

An extensive study and review of literature about multiple variations of the lumbar plexus

Introduction: Lumbar plexus involves the L1 - L5 spinal segments for the formation of the nerves which supply parts of the abdominal wall, pelvis and the upper part of the thigh (both sensory and motor). Our aim in this study was to compile all the rare variations found in a single cadaver, which is of the rarest possible kind. Methods: During the dissection of the abdomen and pelvis in approximately 70 year old cadaver, there were multiple variations observed in the anatomy of the lumbar plexus. The entire region was cleaned for visibility of the variations and all those were clearly documented for compiling purpose. Results: The following variations in the formation of the lumbar and sacral nerves were observed. 1. The genitofemoral nerve bifurcated at a higher level; genital branch of genitofemoral nerve gave branches to the anterior abdominal wall muscles, 2. A communicating branch was given from the lateral cutaneous nerve of thigh to the medial cutaneous nerve of thigh, 3. A muscular branch was given from femoral nerve to psoas major, 4. There was absence of contribution of L4 spinal nerve in the formation of the lumbosacral trunk, and 5. Lumbosacral trunk gave communicating branches to the femoral and obturator nerves. Most of the variations found were rare and finding all the above said variations in a single cadaver is even rare. Conclusion: Knowledge of the normal anatomy and any possible variations would help the clinicians and surgeons dealing with this region and avoid possible complications beforehand.

Study of muscular branch of median nerve to the pronator teres

Background and aims : Disorders of the peripheral nervous system are common among which entrapment neuropathies are frequently encountered by the clinician. The knowledge of innervation pattern of median nerve to pronator teres are of considerable importance in understanding the various presentations of pronator teres syndrome, in investigating the lesions of median nerve, to plan adequate treatment and to avoid iatrogenic injuries during surgeries there by increasing the perfection of surgical approach. The aim of present study is to study the point of origin of muscular branches of median nerve to pronator teres muscle with respect to interepicondylar line and to study the number of branches of median nerve to the pronator teres muscle. Materials and methods : Fifty upper limbs procured from embalmed cadavers aged about 20 to 50 years were used for the study. Results : Out of total 50 specimens, nerve to pronator teres was arising at a mean distance of 1.31 ± 0.58 cm proximal to the interepicondylar line (range 0.5 - 3cm) and 1.2 ± 1.27 cm distal to the interepicondylar line (0-3.5cm). Conclusion: In greater number of the specimens, the nerve to the pronator teres was arising from the median nerve proximal to the interepicondylar line. In majority of the specimens the pronator teres was innervated by either single branch or two branches.