Corpus: Brachioradialis muscle
Definition
The brachioradialis muscle is an elongated, spindle-shaped muscle that belongs to the radial muscles of the forearm. It is the most superficially located muscle on the radial side of the forearm and delineates the cubital fossa (Fossa cubitalis).
Anatomy
Origin
The muscle originates from the lateral edge (Margo lateralis) of the humerus, more precisely from the upper 2/3 of the supracondylar ridge and the lateral supracondylar line, as well as from the lateral intermuscular septum of the arm. Proximally, its origin is limited by the radial nerve groove.
Insertion
The tendinous insertion of the brachioradialis muscle is the styloid process of the radius. The flat tendon is crossed just before this point by the tendons of the abductor pollicis longus muscle and the extensor pollicis brevis muscle.
Innervation
The innervation of the brachioradialis muscle is provided by the radial nerve from the brachial plexus (segments: C5-C6).
Blood supply
The blood supply of the brachioradialis muscle is provided by branches of the radial artery.
Function
The brachioradialis muscle causes flexion in the elbow joint and, depending on the position of the radius, pronation or supination. From a fully extended elbow position, it can supinate about 20° from an extreme pronation position and pronate about 100° from a fully supinated position. The muscle's influence on the flexion of the forearm is strongest when it is in a semi-pronated position (neutral position). The brachioradialis muscle acts as a synergist to the brachialis muscle and the biceps brachii muscle. Its antagonists are the triceps brachii muscle and the anconeus muscle.
Clinic
The brachioradialis muscle serves as a key muscle for the spinal cord segment C6. For clinical examination, the distal tendon end is tapped, and the contraction is observed (radial periosteal reflex). An insertion tendinopathy with tears at the insertion tendon of the brachioradialis muscle is referred to as radial styloiditis.