The upper limb comprises many muscles which are organized into anatomical compartments. These muscles act on the various joints of the hand, arm, and shoulder, maintaining tone, providing stability and allowing precise fluid movement.
Axioappendicular groups of muscles arise from the axial skeleton to act upon the pectoral girdle. Scapulohumeral muscles originate from the scapula and insert into the proximal humerus. Included in this category are the rotator cuff muscles which provide stability to the glenohumeral joint. In the arm, the muscles of the anterior compartment are involved in flexion of the forearm, and the posterior comprises of the forearm extensors. Similarly, the anterior compartment of the forearm contains the flexors of the hand and posterior has extensors. The hand is divided into the thenar, the hypothenar, the adductor compartment, as well as the short muscles of the hand.
Mesenchyme (mesodermal in origin) condenses into sets of dermatomes and myotome complexes. Myotomes migrate into the developing limb buds, to give rise to myoblasts. Elongation of the limb buds, along with muscle formation from myoblasts, compartmentalizes the muscles into their respective muscle groups.
The arterial supply to the muscles of the upper limb is primarily from the axillary artery (of subclavian artery) and its branches. The brachial artery supplies to the anterior compartment of the arm, and the profunda brachii supplies the posterior. In the arm, the radial artery supplies the lateral forearm and the ulnar is responsible for the medial aspect. Beyond the wrist, the radial and ulnar arteries form the superficial and deep palmar arterial arches. The deoxygenated blood drains into the cephalic vein and the basilic vein. Lymphatics of the right upper limb drain into the right lymphatic duct, and the left drains into the thoracic duct.
Anterior Axioappendicular Muscles (Thoracoappendicular Muscles)
Posterior Axioappendicular Muscles
Scapulohumeral (Intrinsic Shoulder Muscles)
*Rotator cuff muscles: supraspinatus, infraspinatus, teres minor, subscapularis
Muscles of Anterior Compartment of Arm (Flexors of Arm)
Muscles of Posterior Compartment of Arm (Extensors of Arm)
Muscles of Anterior Compartment of Forearm (Flexors of Forearm)
Flexor carpi radialis
Flexor carpi ulnaris
Flexor digitorum superficialis
Flexor digitorum profundus
Flexor pollicis longus
Muscles of Posterior Compartment of Forearm
Extensor carpi radialis longus
Extensor carpi radialis brevis
Extensor digiti minimi
Extensor carpi ulnaris
Abductor pollicus longus
Extensor pollicus longus
Extensor pollicus brevis
Intrinsic Muscles of Hand
Abductor pollicus brevis
Flexor pollicus brevis
Abductor digiti minimi
Flexor digiti minimi brevis
Opponens digiti minimi
Rotator Cuff Disease
Involves impingement, tendonitis, as well as tearing of the tendons of the muscles of the rotator cuff. Majority of the cases involve the tendon of the supraspinatus muscle. This is thought to be due to its poor blood supply. The patient complains of pain, especially while lying down on the affected arm or when doing overarm activities. In the clinic, it can be tested by the Hawking’s test and Neer test. The drop test is confirmatory. An MRI is also advised to rule out or confirm a tendon tear. Treatment depends on severity. Management involves NSAIDs, physiotherapy, and arthroscopic repair.
This is the congenital ipsilateral absence or hypoplasia of pectoralis major and pectoralis minor muscles with hypoplasia of the corresponding ribs. It is hypothesized to be caused by an in-utero defect of blood supply to the developing chest. Poland syndrome is commonly associated with defects in breast and/or upper limb development.
Winging of the Scapula
Denervation of the serratus anterior muscle causes palsy of the long thoracic nerve. This causes lateral and posterior movement of the scapula, away from the underlying ribs, giving it a wing-like appearance.
Lateral epicondylitis (tennis elbow) is caused by a combination of repetitive or sustained contraction of the extensor muscles of the forearm leading to inflammation of the common extensor origin. Medial epicondylitis (golfers elbow) is due to repetitive or sustained contraction of the flexor muscles of the forearm leading to inflammation of the common flexor origin. Patients present with pain and tenderness over the affected epicondyle that worsens with extension (in the case of lateral epicondylitis) or flexion (when suspecting medial epicondylitis). Treatment involves avoiding exacerbating activities, physical therapy, and pain relief.
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