LATISSIMUS DORSI MUSCLE: CHARACTERISTICS, FUNCTIONS, SYNDROMES - ANATOMY AND PHYSIOLOGY - 2025

The latissimus dorsi muscle is a muscle of great proportions, being both long and wide, in fact it is the largest in the human body and is located at the level of the trunk in its posterior part.

It is a pair muscle, one on the left side and the other on the right side of the body. Its triangular shape resembles a fan. Its fibers are born from various anatomical structures along the medial line of the trunk. Part of the spinous processes of vertebrae T6 to L5, and reaches the middle sacral crest.

Graphic representation of the latissimus dorsi muscle. Source: User: Mikael Häggström. Edited image.

Along the way it touches the last ribs (X-XII) and the iliac crest laterally. Eventually, all the muscle fibers are brought together or inserted into one place. For this, its fibers are arranged in a single direction from their respective origins to the bicipital groove in the humerus, where it is inserted.

This muscle is useful for lifting weights from the ground, for climbing, swimming in butterfly or backstroke, or walking in a quadruped position, among other activities. However, at present very little is exercised this muscle, so it can weaken and shorten. To avoid this, it is recommended to include exercises in the daily routine that help to strengthen and stretch it.

characteristics

As its name suggests it is a wide muscle and also quite long. It is superficial and flattened, with a triangular shape that covers two-thirds of the back, joining the shoulder girdle with the pelvic girdle.

The latissimus dorsi is a paired muscle, that is, there is a muscle on each side of the body (right and left) arranged symmetrically. It is the largest muscle in the thoracic area and in the human body in general. Its size goes hand in hand with its strength.

It is characterized by having muscle fibers that travel towards a common point of insertion. To do this, the upper muscle fibers move horizontally from the inside out, the intermediate fibers upward and obliquely, and the lower ones upward and almost vertically.

Because it is a large muscle, it is very useful in the area of ​​reconstructive surgery. Surgeons can take part of this muscle to restore limbs deformed by traumatic accidents, burns, tumor removal or any other cause. An example of this occurs in breast reconstruction.

For this there are many reconstructive surgery techniques, but Díaz-Ontiveros et al. Recommend the latissimus dorsi muscle flap technique in its reverse form, for extensive reconstructions in the thoraco-lumbar area. According to them, it is a simple procedure, with few complications.

On the other hand, Peña et al. In 2010 described a latissimus dorsi muscle transposition to correct the consequences of high obstetric brachial palsy (PBOA).

It should be noted that this pathology leads to a malfunction of shoulder movements, limiting abduction and external rotation. Then it progresses causing a contracture in adduction and internal rotation, as well as a possible dislocation of the shoulder with deformation of the glenoid.

Origin

Its origin is complex since it involves numerous anatomical structures due to its large size.

The upper portion of the lower and dorsal trunk muscle, in the spinous processes, starting from the sixth thoracic vertebra to the number 12 thoracic vertebra. The first part of the latissimus dorsi muscle is covered by the trapezius muscle.

The origin of the middle part of the muscle continues towards the middle zone (thoracolumbar fascia of L1-L5). Along the way it involves the outer face of the last ribs (IX-XII). And finally, the lower part of the muscle passes laterally through the outer lip of the iliac crest and reaches the midline of the median sacral crest.

Insertion

All the fibers of the latissimus dorsi muscle converge at a single site. The fibers travel from the inside out and upward until they reach the insertion site in the humerus.

The insertion takes place in the bicipital canal, also known as the bicipital groove or intertubercular canal of the humerus, that is, between the lesser tubercle (troquín) and the greater tubercle (troquiter). The fibers culminate in a spiral and tendon shape.

Innervation

The latissimus dorsi muscle is innervated by the thoracodorsal nerve (C6-C8) which corresponds to the brachial plexus.

Irrigation

The main blood supply is received from the thoracodorsal artery but it also welcomes small arteries that come from posterior intercostal branches and from the lumbar, such as: the subscapular artery and the dorsal scapular artery.

Features

The functions can be studied in the following way: when the trunk is motionless and when the arm is fixed.

Fixed trunk

Under this condition, the muscle allows the following movements: extension, abduction and internal rotation of the upper limb. It is also capable of depressing the shoulder to prevent superior displacement of the humerus head.

On the other hand, thanks to the latissimus dorsi, the retraction or retropulsion movement is possible, which consists of moving the shoulders back, for example: backstroke or when dragging an object towards you.

Finally, this muscle is also active in quadruped gait or crawl and to stabilize the pelvis.

Fixed arm (hanging position)

If both muscles are stimulated, the trunk can be raised, which leads to the elevation of the ribs, due to the distension of the dorsal lumbar spine. For this reason, it is considered an accessory or secondary muscle in the inspiratory movement.

If only one of the muscles is stimulated, lateral movement of the trunk is possible, that is, pulling the trunk to one side or the other (same side of the muscle in action). As well as the rotation of the trunk.

Latissimus dorsi syndromes

Back pain

Characterized by a pain in the back. It has multiple causes, but one of them may be the injury of the latissimus dorsi muscle. A muscle tear can occur from lifting excessive weight without warming up. Maintaining bad postures for a long time produces contractures and painful trigger points in this muscle.

Pain in the shoulder

Due to its insertion in the bicipital groove of the humerus, an injury to this muscle affects the stability of the shoulder and consequently will cause limitation of joint movement and pain.

Low back pain

It is characterized by pain in the lumbar part of the spine. It can have various causes, but one of them is an increase in the tone of the latissimus dorsi muscle, which can be accompanied by a psoas contracture. This pathology can cause hyperlordosis.

Thoracodorsal nerve palsy

This nerve innervates the latissimus dorsi muscle and if it suffers alterations the muscle becomes paralyzed. Therefore, the involvement of the thoracodorsal nerve has a direct influence on the dysfunction of the shoulder girdle.

Exploration

Palpation

Because this muscle covers a large area, it can be palpated from five anatomical points. From top to bottom these points would be the following:

The first point corresponds to the outside of the armpit. By pressing at this point, the upper area of ​​the latissimus dorsi muscle can be touched, before its narrowing and insertion into the humerus.

The second point would be at the level of the spinous processes corresponding to the dorsal 7 to the lumbar vertebrae 5. To locate them, the patient is asked to bend the trunk towards the front.

In this position it is possible to palpate the aforementioned vertebrae. As a guide, the primary location of the C7 or D1 vertebrae, which are the most protruding, is used.

The third point is at the level of the IX-XII ribs. To locate them, we measure two fingers above the iliac crest, where the last rib (XII) is palpated and following the sequence the rest can be located.

The fourth point is located on the iliac crest, which is easy to palpate when placing the hand on the waist. The muscle is located at the back of the ridge.

The fifth point is on the sacrum, just on the middle sacral ridge. To locate it, climb from the coccyx up the midline.

Muscle stretching

With the patient seated, one arm of the patient is grasped and the shoulder is brought into full abduction with the elbow flexed and the iliac crest is fixed with the other hand.

In this position, the patient's arm is carried in a forced bird movement behind the head, with a contralateral tilt of the trunk (opposite side of the arm in action).

The position should be held for 15 to 30 seconds and then return to the starting position. Repeat the procedure 3 to 5 times and then do the same on the other side.

Strengthening exercises

Several can be mentioned: the reindeer, dominated, the âsanas.

References

1. Díaz-Ontiveros J, Moreno-Villalba R, Santoyo-Gil F. Closure of thoraco-lumbar defect using a reverse latissimus dorsi flap: on the subject of a case. Ibero-Latin American Plastic Surgery, 2013; 39 (3): 299-303. Available at: scielo.isciii.es/
2. Costa A. Latissimus dorsi. Yoga Synthesis Teacher training school. Available in:
3. Peña L, López I, Remón X, Albisus E, Cañizares D, Pereda O. Transposition of the latissimus dorsi and teres major muscles for the treatment of obstetric brachial palsy. International Orthopedic Scientific Complex. 2010; 59 (19603): 196-202. Available at: scielo.sld.cu
4. Saldaña E. (2015). Manual of human anatomy. Available at: oncouasd.files.wordpress
5. Barrios G, Tejada A. Digital maneuver on the latissimus dorsi muscle to facilitate axillary dissection. Rev. venez. oncol. 2010; 22 (3): 205-210 Available at: scielo.org-
6. Domínguez-Gasca, L, Domínguez-Carrillo L. Shoulder girdle dysfunction due to isolated paralysis of thoracic muscles. Grupo Ángeles Medical Acta, 2011; 9 (4): 1-5. Available at: mediagraphic.org.