Rhomboid Major Anatomy
The Rhomboid major or Rhomboideus major is also called (in latin) the musculus rhomboideus major and is one of the deep extrinsic shoulder muscles (the deep posterior thoracoappendicular muscles) the others being levator scapulae and rhomboid minor. The two rhomboids (major and minor) lie deep to the trapezius muscle and form parallel bands that pass inferior and laterally from the vertebrae to the medial border of the scapula. The Rhomboid major muscle is thin and flat but twice wider than Rhomboid minor which is thicker and lies superior to the rhomboid major. There could be variations in some persons in which the two rhomboid muscles fuse to form a single muscle.
Rhomboid Major Action/Function
The two rhomboids: Rhomboid major and Rhomboid minor all retract the scapula and also rotate it in order to depress the glenoid cavity. The Rhomboids also fix the scapula to the thoracic wall by assisting the serratus anterior to carry out the same function of fixing the scapula during movements of the upper limb.
Rhomboid Major Origin and Insertion
Rhomboid major originates from the spines of the T2, T3, T4 and T5; it also originates from the supraspinous ligaments of the corresponding vertebrae. The point of insertion of the rhomboid major is at the medial border of the scapula from level of spine to inferior angle of the scapula. The insertion of rhomboid major into the scapula extends from the inferior angle to the upper part of the triangular area at the base of the scapular spine; a fibrous arch receives the fibers of the muscle between these two points. The fibrous arch is often only loosely attached to the vertebral border of the scapula except at its ends like the bony origin of levator ani.
Rhomboid Major Nerve Supply
Rhomboid major is supplied by the Dorsal scapular nerve, also known as the nerve to the rhomboids (supplied by C4 and C5 cervical segments of the spinal cord). The dorsal scapular nerve is a branch of the brachial plexus from the C5 root of the brachial plexus, it passes through scalenus medius muscle and then runs down deep but anterior to levator scapulae to supply it; this nerve lies on the serratus posterior superior muscle to the medial side of the descending branch of the transverse cervical artery. The dorsal scapular nerve supplies each rhomboid muscle on the deep surface.
Rhomboid Major Blood Supply
The rhomboid major muscle as well as the rhomboid minor are supplied by the dorsal scapular artery
Rhomboid major Test
The Rhomboid major muscle test is carried out with the hand on the hip or behind the back, then, the elbow is pushed backwards against resistance while bracing the shoulder back. The muscles are palpated at the vertebral border of the scapula. If the rhomboids of one side are paralyzed, the scapula of the affected side remains further from the midline than that of the normal side.
Clinical importance of Rhomboid major muscle
Any injury to the dorsal scapular nerve affects the rhomboid major and minor muscles and this can lead to paralysis of the muscles which then causes scapula instability such as scapula winging during depression of the scapula or protraction.
Differences between Rhomboid major and minor
- The rhomboid major is wider than the rhomboid minor
- The rhomboid major is thinner than the minor (the rhomboid minor is thicker)
- The rhomboid minor lies superior to the rhomboid major