Pectoralis Major Tendon Rupture
By Joe de Beer
Introduction
The Pectoralis Major (large pectoral) is a large muscle on the front of the upper chest and arm.
Detail
The Pectoralis Major tendon ruptures off it’s insertion on the humerus with strong contraction when the arm is forced backwards (horizontal extension). That could happen with Bench Press, and other forceful movements.
A sudden pain will be felt in the chest and upper arm and there will be blue discoloration in the upper arm due to bleeding. The pec major will form a bulge on the chest.
Fig 1. Outside view of the large muscles around the shoulder.
Fig 2. The two parts of the pectoralis major muscle: Sterno-costal and clavicular. With the arm moving backwards (as in the Bench Press exercise) there will be more strain on the horizontal part (which tears more commonly) than on the oblique part.
Anatomy
There are two “heads” – the clavicular and sterno-costal. The clavicular head originates from the clavicle (collar bone) and runs obliquely downwards and laterally to the upper arm (humerus). The sterno-costal runs more horizontally slightly behind the clavicular head and originates from the sternum (breast bone) and ribs. The two heads blend to form one tendon in two layers with the sterno-costal head slightly deeper to the clavicular head.
Function
The action of the muscle is to bring the arm in from a stretched out position towards the body. This action is well understood if one considers that in gorillas the pectoralis major is extremely well developed due to the fact that they hang and pull themselves up on branches continuously. In a human the muscle pulls the humerus (upper arm) towards the body and this action is often done in exercises like pull-ups from an overhead bar (in conjunction with the latissimus dorse) as well as other exercises like the bench press and dumb bell flyes.
Injuries
The tendon usually ruptures when it is loaded with the arm being extended to the back. One has to note that this large and powerful muscle inserts with a tendon, which is only 1.5 cm wide where it inserts on the humerus and the muscle then overpowers its insertion and it tears off the humerus.
The sternocostal head of the muscle, which runs more horizontally than the oblique clavicular head tears most commonly.
Steroid use as in bodybuilding may promote such tears as the muscle growth is more than the tendon strengthening.
Fig 3. A tear of the sterno costal part of the Pec major muscle. This part tears more commonly than the clavicular part. In rare instances both parts omay tear together.
Clinical picture
After such a rupture there is immediate intense pain, which may gradually subside. Blue discolouration might be seen in the upper arm due to the fact that the tendon was severed from the upper humerus. There is a defect over the lateral aspect of the pectoralis major with the pectoralis major appearing deformed and bulky closer to the breastbone.
Pec Major rupture on the left side: the muscle is retracted medially and forms a bulge
Bleeding in the upper arm, due to the avulsion of the tendon of the Pec Major off it’s insertion on the humerus
Management
This is a massive muscle and it is the opinion of this author that it should always be repaired as soon as possible. If this tear is left for too long the muscle slowly retracts towards the breastbone and it could become very difficult to mobilise it again to its insertion.
Chronic ruptures
In “neglected” tears muscle and tendon can be mobilised and if it does not reach its original insertion in spite of extensive surgical mobilisation the surgeon may be forced to insert a tendon graft between the end of the tendon and the site of bony insertion.
Fig 4. A chronic, long-standing tear of the tendon – the muscle retracts and due to this shortening it may become difficult or impossible to repair.
Surgical repair
The technique of repair requires attention to detail as this massive muscle pulls on a very slender tendon and good fixation techniques by the surgeon is mandatory. We use a very strong artificial ligament (LARS Ligament), which is woven through the muscle and tendon, and attached to the bone with drill holes. Following this surgical repair the arm is kept in a sling in internal rotation for at least 3-4 weeks to allow healing. Gradual mobilisation is then permitted and heavy loads on this muscle and tendon should not be done before three months following the surgery.
The torn sternal head of the Pec Major with woven LARS
Fig 5. Repair of Pec major. The muscle is large compared to its tendon – the repair done by the surgeon must be strong enough to withstand the pull of the muscle till the tendon has healed to the bone.