Pectoralis Major Injury

Fig. 27.1

These figures show how MRI is acquired for the pectoralis major muscle in sagittal (a), axial (b), coronal (c), and abduction and external rotation (ABER) (d) planes

An abduction and external rotation (ABER) sequence can be added to the protocol for estimating the tendinous gap in the proper anatomic axis of the tendon (Fig. 27.1d).

In 2000, Lee et al. published a cadaveric study, and described important anatomical landmarks of the pectoralis major insertion on MRI [4].

The superior margin of the pectoralis insertion is the quadrilateral space. Another reliable landmark of the superior aspect of tendon insertion is the origin of the lateral head of the triceps muscle, identifying the tendon approximately 5–10 mm superior to the level at which the lateral head of the triceps is first identified (Fig. 27.2).

The inferior boundary of tendon insertion is the superior aspect of the deltoid tuberosity (Fig. 27.3).

Fig. 27.2

Insertion of the pectoralis major tendon and superior anatomic landmarks. Axial T1-weighted MRI show the quadrilateral space (a), the origin of the lateral head of the triceps (arrow, b, c) and the superior aspect of the tendon insertion (c).

Fig. 27.3

Insertion of pectoralis major tendon and inferior anatomic landmarks. Axial T1-weighted MRI show the normal aspect of pectoralis tendon insertion (arrow, a) at the lateral edge of the intertubercular groove, and also show the deltoid tuberosity (arrow, b) an anatomical landmark for the inferior aspect of insertion

27.4 Pectoralis Major Tears

Pectoralis major tears can be described by anatomic location as muscle origin (clavicular and sternocostal head), muscle belly, musculotendinous junction, intratendinous, humeral insertion, and bony avulsion [5–7].

27.5 Muscle Origin and Muscle Belly Tears or Sprains

Less common than other sites and usually due to direct trauma, as in an automobile accident or a blow against the chest. In general they are incomplete tears, with the muscular damage restricted to the area of direct contact and are treated conservatively.

27.5.1 Musculotendinous Junction, Intra-tendinous, Humeral Insertion and Bony Avulsion

Pectoralis tendon tears occur primarily at the tendon insertion and musculotendinous junction. Bony avulsions can occur in 2–5 % cases.

In MRI complete tears are characterized by tendon disruption and muscle fiber edema with subsequent proximal retraction, usually superficial to the biceps brachii tendon short head and coracobrachialis. A fluid collection usually is interposed between the torn tendon and the humerus (Figs. 27.4 and 27.5).

Fig. 27.4

A 32-year-old man with a complete myotendinous junction tear after bench press exercise. Axial T1-weighted MRI show a complete distal pectoralis major tear (arrow, a–d) retracted proximally, superficial to biceps brachii short head. Axial fat-suppressed T2-weighted MRI demonstrate the fluid collection filling the tendinous gap and muscle fiber edema (arrow, e–h)

Fig. 27.5

A 39-year-old man with a complete myotendinous junction tear after bench press exercise, 1 week later. Axial fat-suppressed T2-weighted MRI shows a complete distal pectoralis major tear (arrow, a). Axial T1-weighted image shows the tendon retracted proximally, superficial to biceps brachii short head and coracobrachialis (arrow, b). Sagittal fat-suppressed T2-weighted MRI demonstrates tendon discontinuity in the distal third (arrow, c)

Incomplete tears also are better visualized on MRI. In the acute phase, the tear is characterized by edema of the tendon with focal discontinuity. In the chronic phase the diagnosis is made by focal rupture and tendon retraction or even by fibroscar thickening of the tendon (Figs. 27.6, 27.7 and 27.8). In chronic extensive ruptures a thin tendon without frank discontinuity at the humeral insertion is commonly seen that leads to aesthetic deformity of the chest wall (Fig. 27.9)

Fig. 27.6

A 26-year-old-man with a partial tear of the myotendinous junction after a jiu-jitsu blow. Coronal fat-suppressed T2-weighted MRI shows focal discontinuity of myotendinous junction (arrow, a). Axial fat-suppressed T2-weighted MRI shows tendon retraction and a small fluid collection (arrow, b). Sagittal fat-suppressed T2-weighted MRI demonstrates tendon discontinuity in the distal third (arrow, c)

Fig. 27.7

A 23-year-old-man with complete pectoralis major tear at humeral insertion after bench press exercise. Coronal fat-suppressed T2-weighted MRI shows complete tendon retraction (arrow, a) and a fluid collection. Axial (b) and sagittal (c) fat-suppressed T2-weighted MRIs show complete discontinuity at humeral insertion (arrow)

Fig. 27.8

A 37-year-old-man with chronic pain during weight lifting. Coronal T1-weighted MRI (a) shows focal tendon discontinuity and proximal retraction suggestive of a chronic partial tear of the musculotendinous junction (arrow). Coronal fat-suppressed T2-weighted MRI shows fibroscar alterations of the retracted tendon (arrow, b)

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