What is a Pectoralis Muscle?

The pectoralis major is shallow in the anterior upper part of the thorax.

The pectoralis major is shallow in the anterior upper part of the thorax.

Chinese name

Pectoralis major

Foreign name

pectoralis major

nickname

Pectoral muscle

Shape

Sector

Pectoralis major muscle overview

The pectoralis major is shallow in the anterior upper part of the thorax.

Starting end: the clavicle (the inner half of the clavicle), the sternum (the sternum and the upper 5-6 rib cartilage), and the abdomen (the front wall of the rectus sheath).

Stop: the large tuberosity of the humerus (the clavicle and the abdominal muscles cross up and down).

The muscular abdomen is fan-shaped, and the "U" -shaped flat tendon is concentrated on the large nodule ridge (outer lip of nodular groove).

Pectoralis major anatomy and function

One of the pectoralis major structural features: different starting fibers have different ends. The fibers of the clavicle portion form an anterior layer of the flat tendon, the fibers on the outside stop at the upper end of the lateral lip, and the fibers at the inside stop at the lower end of the lateral lip. The fibers in the sternum and abdomen go up and out, and are located below and below the clavicle fibers. This structure makes the upper and lower muscle bundles stretch the same when the upper arm is abducted. When the pectoralis major muscle is contracted, the humerus can be retracted and rotated. The thoracic rib can extend the raised upper limbs to help breathing. The clavicle contraction can flex the shoulder joint.

Pectoralis major auxiliary structure

1. Between the pectoralis major and deltoid muscles, there is an obvious palpable triangle between the pectoralis major muscles. There is a cephalic vein in the groove. It is located in front of the shoulder joint. A local area that you should pay attention to when you are walking is also a useful indicator of the natural boundary between the deltoid and pectoralis major. When the surgical repair is performed at the joint where the deltoid muscle is separated from the pectoralis major, attention should be paid to the cephalic vein that enters the subclavian vein along the triangular pectoralis major groove. Once damaged, the proximal end may be retracted and it is not easy to stop bleeding.

a) There are multiple sources of blood supply to the pectoralis major, including the superior and inferior pectoralis branches of the thoracic acromion artery, the pectoralis branch from the axillary artery, and the anterior intercostal artery and perforating branch of the internal thoracic artery. The pectoral muscle branch of the most superior artery. Vascular vessels of different origin have rich anastomosis in the muscle.

b) innervating nerves: lateral thoracic nerve and medial thoracic nerve originating from the spinal nerve brachial plexus.

Clinical Technology and Application of Pectoralis Major

1. In 1979, some scholars introduced the application of the pectoralis major muscle flap in the repair of head and neck tumor defects. Later, the flap quickly replaced other pedicled flaps at that time and became the most commonly used tissue flap after head and neck tumor resection. However, the blood supply of the pectoralis major flap is not very reliable. It is reported that the proportion of necrosis and partial necrosis of the flap is as high as 7% to 20%. However, because the preparation of the pectoralis major flap is simple, it is not necessary to change the position during the operation. Moreover, it is not necessary to perform anastomosis of the blood vessels, and the donor area can be directly pulled and sutured. Therefore, for units without microsurgical technology and patients who are not suitable for free flap transplantation, the pectoralis major skin flap is still a reliable repair method.

2. The improved method uses the medial approach of the pectoralis major muscle. Since the medial side of the pectoralis major muscle is thinner than the lateral side and there is a clear layer between the pectoralis major muscle and the chest wall, it is very easy to turn up. The positioning is faster, easier and safer than the outside approach. In addition, only part of the muscles inside the pectoralis major muscle were cut during the preparation of the flap, so that most of the muscle fibers outside the pectoralis major muscle were retained, thereby maximizing the function of the pectoralis major muscle. The pedicle of a traditional pectoralis major flap is a muscular vascular pedicle. When it passes over the surface of the clavicle, the bloated muscles will cause compression of the vascular pedicle, which will affect the blood supply of the myocutaneous flap. In fact, many pectoralis major flaps The cause of the flap failure can be attributed to the compression of the pedicle of the blood vessel. In addition, the length of the vascular pedicle is limited when the bloated muscular vascular pedicle passes over the clavicle surface. In order to extend the length of the vascular pedicle, the traditional method is to design the skin island farther from the distal end of the pectoralis major muscle, or even located in the rectus abdominis. The surface of the sheath. However, because the thoracic acromion artery's blood supply to the skin of the rectus abdominis sheath surface spans a vascular unit, according to Taylor's theory, the blood supply in this area is not very reliable, which has caused the randomness and unreliability of the blood supply to the island. , Which increases the chance of flap necrosis. In order to prevent compression of the vascular pedicle and prolong the length of the vascular pedicle, our method is to prepare the pectoralis major muscle flap into a true island flap, that is, the vascular pedicle 5 cm below the clavicle does not carry any muscle, so that the vascular pedicle passes over the clavicle. The surface is not easy to be compressed, and the length of the vascular pedicle of the myocutaneous flap is greatly extended. At the same time, because the skin islands are all designed on the surface of the pectoralis major muscle, the blood supply is very reliable, and the success rate of the pectoralis major flap is improved. . If a longer vascular pedicle is needed, we can also use the method of vascular pedicle passing behind the clavicle. This method can further lengthen the vascular pedicle by 4cm. However, you should be very careful during operation to prevent accidental injury to the pedicle root and subclavian arteriovenous, so as not to cause serious consequences.

Pectoralis major related diseases

In recent years, with the increase of amateur sports and bodybuilding enthusiasts, the incidence of pectoralis major muscle injuries has increased year by year. Pectoralis major injury is most common in men aged 20 to 40, and has nothing to do with armdominance. The causes of injury include weightlifting, basketball and football, wrestling, and direct impact. The injury mechanism is caused by excessive stretching or impact on the muscles when the upper limbs are fully abducted and extended. The clinical manifestations of patients with pectoralis major muscle injury include local pain, skin bruising, edema, and restricted movement. Without the help of imaging, it is difficult to determine the type of injury clinically.

Judging the degree of pectoralis major muscle injury is very important. Partial tears can choose conservative treatment, while those with complete rupture require surgery. According to the degree of injury, they can be divided into partial tear and complete rupture. Part of the pectoralis major muscle tear shows swelling of muscle fibers in the injured area, showing irregular hypoechoic or no echo, muscle tendon continuity is intact, and some are accompanied by hematoma formation; tendon injury shows uneven tendon echo in the lesion area, and some appear Wavy appearance. It has been reported that a pectoralis major muscle tear can cause the biceps brachii longus tendon to be elevated, and the surface of the bone cortex can be uneven and accompanied by avulsion fractures, which are helpful for diagnosis. A complete rupture is manifested as a rupture of a tendon or muscle fiber. When the tendon is completely ruptured, the local tendon is absent, and the ruptured muscle abdomen can be locally raised; if accompanied by a hematoma, you can see hypoechoic, non-echo or mixed echo masses. Can have a placeholder effect. The stump muscle abdomen retracts to the medial side. Over time, the adhesion between the retracted muscle and the stump of the tendon can form a false tendon, which may cause difficulties in ultrasound diagnosis of the type and scope of pectoralis major muscle injury. Attention should be paid to the actual work. High-frequency ultrasound can locate the anatomical part of pectoralis major muscle and tendon injury, determine the extent and scope of the tear, and provide assistance in the selection of clinical treatment options. However, the anatomy of the pectoralis major muscle is complicated, and it is necessary for the ultrasound physician to accumulate rich anatomical knowledge and muscle scanning experience, and to master the echo characteristics, locations and continuity judgment points of muscle and tendon injury in order to correctly assess the damage of the pectoralis major muscle and its tendon. .