AJR 2005; 184:1205-1211
© American Roentgen Ray Society
Sonographic Evaluation of Injuries to the Pectoralis Muscles
Amer Rehman and
Philip Robinson
Leeds Teaching Hospitals, St. James University Hospital, Chancellor Wing,
Beckett St., Leeds LS9 7TF, England.
Received April 28, 2004;
accepted after revision July 20, 2004.
Address correspondence to P. Robinson
(p.robinson{at}leedsth.nhs.uk).
Abstract
OBJECTIVE. Our aim was to show the application of high-resolution
sonography for grading and defining athletic and nonathletic injuries to the
pectoralis muscles.
CONCLUSION. Sonography provides dynamic high-resolution imaging for
the diagnosis and grading of injuries to the pectoralis muscles.
Introduction
High-grade injury of the pectoralis major muscle is uncommon and has
been predominantly reported as a sports injury among young male athletes
[1-3].
Studies describe forced external rotation, extension, and abduction of the
humerus while bench-pressing as the most common mechanism of injury
[1-4].
During this maneuver, the abdominal component of the muscle is maximally and
eccentrically stretched, undergoing more excessive loading with humeral
extension [3]. Forced abduction
and external rotation applied across the contracted muscle of an outstretched
arm while breaking a fall has also been reported as a mechanism of injury
[2,
4].
Clinically, injuries to the pectoralis muscles can be difficult to diagnose
acutely because of soft-tissue swelling, ecchymosis, tenderness, and muscle
spasm [3,
5]. The complex anatomy of the
muscle also makes clinical differentiation between partial and complete tear
difficult, which is important because the orthopedic consensus favors a
conservative approach for partial injuries and surgical repair for complete
tears [1,
3,
4,
6].
The MRI assessment of pectoralis major anatomy and injury in athletes has
been previously described [5,
7,
8]. These studies report that
complete tears are more common than partial tears, occurring predominantly at
the distal humeral insertion (enthesis) rather than at the myotendinous
junction [5,
7,
8]. A number of series have
also reported difficulty in defining the muscle components on conventional MRI
[5,
8].
Sonographic assessment of muscle anatomy and injury has been described but
not in relation to the grading of injuries to the pectoralis muscles
[9,
10]. The aim of this article
was to show the application of sonography for grading and defining injury of
the pectoralis muscles.
Subjects and Methods
Normal Anatomy
After obtaining institutional ethics committee approval, we performed
sonography in three asymptomatic volunteers (all men; age range, 22-28 years)
to define the normal sonographic appearances of the pectoralis muscles,
laminae, and tendons. The pectoralis major muscle has a broad origin from the
anterior chest wall, with three discernible heads
(Fig. 1A). The clavicular head
(which forms the anterior lamina of the tendon) arises from the anterior
surface of the medial two thirds of the clavicle and upper sternum
[3,
8,
11]. The "sternal
head" comprises the manubrial head (middle lamina) arising from the mid
portion of the sternum and the first-to-fifth costal cartilages with the more
caudal abdominal head (posterior lamina) arising from the fifth and sixth ribs
and the fasciae of the external oblique and transversus abdominis muscles
[3]
(Fig. 1B). The clavicular and
manubrial heads (Fig. 1C) have
a relatively horizontal orientation, whereas the abdominal head is more
vertically oriented. The laminae fuse to form a trilaminar tendon that twists
90° just before its insertion at the lateral lip of the bicipital groove
(Fig. 1D), where the posterior
lamina inserts cranially and the anterior lamina comprises the most caudal
part of the enthesis [3].
Microscopically the abdominal head consists of multipennate fibers, compared
with a unipennate structure of the remaining muscle
[3].
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Fig. 1D. —Normal anatomy. Transverse oblique extended-field-of-view
sonogram shows sternal muscle head of pectoralis major muscle (P) extending
from sternum (S), converging to distal myotendon (arrowheads), and
inserting into humerus (H).
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The pectoralis minor muscle originates (via a proximal tendon) from the
medial aspect of the coracoid process passing deep in relation to the
pectoralis major muscle (Fig.
1E), inserting into the third to fifth ribs at the costochondral
junctions [11].
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Fig. 1E. —Normal anatomy. Sagittal extended-field-of-view sonogram of
chest wall shows abdominal (Ab), sternal (S), and clavicular (C) muscle heads
of pectoralis major muscle. Pectoralis minor (PMi) muscle lies deep relative
to sternal and clavicular heads.
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Clinical Cases
We studied five consecutive patients (four men, one woman; median age, 38;
age range, 26-45 years) referred by emergency physicians for assessment of a
clinical pectoral muscle injury before orthopedic referral.
Patient 1 was a 41-year-old man, referred 56 days after falling down an
open manhole, resulting in forced abduction and extension of the left arm
(Figs. 2A,
2B, and
2C). Patient 2 was a
26-year-old male rackets athlete referred 10 days after a fall onto an
outstretched right arm, resulting in forced external rotation, extension, and
abduction (Figs. 3A,
3B, and
3C). Patient 3 was a
38-year-old man referred 7 days after feeling a left-sided chest wall tear
while trying to stop a rifle from falling, resulting in the arm undergoing
forced abduction and external rotation
(Fig. 4). Patient 4 was a
45-year-old man with hemophilia referred 4 days after developing a painful
right-sided chest wall swelling while lifting a car jack
(Fig. 5). Patient 5 was a
26-year-old woman referred 4 days after a fall across a store trolley onto an
outstretched right arm, resulting in forced abduction and external rotation of
the right arm (Fig. 6).
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Fig. 2A. —41-year-old male patient who suffered forced external and
abduction injury to left arm when falling down manhole. Transverse oblique
extended-field-of-view sonogram shows grade 3 tear with retracted and
echogenic (due to fat infiltration) sternal muscle belly (P) and subacute
hematoma (asterisk) adjacent to humerus (H). Note intervening linear
echogenic structure (arrowheads) that extends over hematoma inserting
into humerus deep relative to deltoid (D). Proximal aspect of this structure
did not contract on dynamic imaging and was presumed to be scar tissue.
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Fig. 2B. —41-year-old male patient who suffered forced external and
abduction injury to left arm when falling down manhole. Axial T1-weighted MR
image of left chest wall at same level as A shows retracted sternal
head of pectoralis major muscle (P) with some fatty infiltration present. It
is difficult to differentiate chronic hematoma of tendon from overlying
deltoid (D) at level of humerus, but intervening scar tissue can be identified
(arrowheads).
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Fig. 2C. —41-year-old male patient who suffered forced external and
abduction injury to left arm when falling down manhole. Corresponding
intraoperative photograph shows intact distal tendon (arrowhead) with
proximal scar tissue extending along border of subcutaneous fat
(arrows).
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Fig. 3A. —26-year-old male badminton player who had forced abduction
and external rotation (ABER) of right arm after fall during competition.
Transverse extended-field-of-view sonogram shows proximal sternal head of
pectoralis major muscle (P) with grade 3 tear of distal myotendon
(arrowheads) and acute hematoma (asterisks).
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Fig. 3B. —26-year-old male badminton player who had forced abduction
and external rotation (ABER) of right arm after fall during competition.
Transverse oblique sonogram shows partial (grade 2) tear (arrows) of
distal clavicular head myotendon with hematoma (asterisk).
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Fig. 3C. —26-year-old male badminton player who had forced abduction
and external rotation (ABER) of right arm after fall during competition.
Sonogram of same region (B) with arm in ABER position shows elongation
of hematoma (asterisk) at its margins (arrows) with
surrounding muscle myotendon remaining intact, confirming grade 2 injury.
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Fig. 4. —38-year-old male patient who suffered forced external
rotation and abduction injury to left arm while trying to stop a rifle from
falling. Longitudinal extended-field-of-view sonogram of sternal head of
pectoralis major muscle (P) under active contraction shows grade 3 tear at
distal myotendon with intervening hematoma (asterisks). Distal tendon
(arrowheads) is heterogeneous but intact, inserting into humerus (H)
deep to overlying deltoid (D).
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Fig. 5. —45-year-old male patient with hemophilia who presented with
chest wall swelling after lifting injury. Sagittal oblique
extended-field-of-view sonogram shows normal pectoralis major muscle
(asterisk). Pectoralis minor muscle (Mi) is swollen and
heterogeneous, especially at its proximal myotendinous origin
(arrowheads) at coracoid process (Co), with hypoechoic hematoma
(arrow) occupying 50% of myotendon, indicating grade 2 tear.
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Fig. 6. —26-year-old female patient with acute central chest pain
after fall involving forced external rotation and abduction of right arm.
Transverse extended-field-of-view sonogram obtained at level of sternum (S)
shows asymmetry between right (R) and left (L) sternal origins of pectoralis
major (see Fig. 1B). Note
normal left-sided muscle and enclosing echogenic aponeurosis
(arrows). In comparison, right-sided aponeurosis
(arrowheads) is ill-defined, displaced, and hypoechoic (edematous).
Diagnosis was partial (grade 2) muscle injury with acute muscle hematoma
(asterisk).
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Sonography
An experienced musculoskeletal radiologist performed the sonographic
examinations of the chest wall and proximal arm using a linear 9.4-13.5-MHz
transducer (Elegra and Antares, Siemens Ultrasound). The three heads of
pectoralis major and pectoralis minor, biceps brachii, and deltoid muscles and
the rotator cuff were assessed in the long and short axes of the muscle and
tendon, both at rest and dynamically (Figs.
2A,
2B,
2C,
3A,
3B,
3C,
4,
5,
6). In particular, the
pectoralis muscles were evaluated with the arm abducted and externally rotated
(ABER position) to stress the myotendinous region (Figs.
2A,
2B, and
2C). Extended-field-of-view
images were obtained to show to clinicians the anatomy surrounding
abnormalities.
Injuries were prospectively graded according to a recognized muscle tear
classification system [9,
10,
12] into grades 1, 2, or 3.
Grade 1 was defined as less than 5% of the muscle involved; grade 2, as a
partial tear of the muscle (> 5% involvement) (Figs.
3A,
3B,
3C,
5, and
6); and grade 3, as a complete
tear of the muscle head (Figs.
2A,
2B,
2C,
3A,
3B,
3C,
4). If detected, the location
of the tear was recorded as origin (Fig.
6), peripheral (aponeurotic), myotendinous junction (Figs.
2A,
2B, and
2C), or enthesis.
Clinical Follow-Up
The clinical course of all patients was followed up retrospectively by case
note review at 6 weeks, 3 months, and 6 months. Patient 2 also underwent MRI
consisting of axial, coronal, and sagittal T1-weighted conventional spin-echo
(TR/TE, 764/14) and T2-weighted turbo spin-echo fat-suppressed (4,120/75;
echo-train length, 7) sequences obtained 5 days after sonography was performed
(Figs. 2A,
2B, and
2C).
Results
In four patients, injuries of the pectoralis major muscle and, in one
patient, an injury to pectoralis minor muscle were recorded. Four (80%) of
five injuries were at the myotendinous junction, and one injury (20%) was at
the proximal sternal origin of the pectoralis major muscle. No isolated
enthesis injuries were identified. In all patients, no injuries were recorded
of the deltoid, biceps brachii, subscapularis, supraspinatus, or infraspinatus
muscle.
The sonography grading and subsequent management for each case are
summarized in Table 1.
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TABLE 1 Summary of Injury Mechanism, Sonography Grading, and Treatment of
Injuries to the Pectoralis Muscles in Five Patients
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Three patients had complete (grade 3) tears of the sternal head (abdominal
and manubrial heads) at the myotendinous junction. In one case (patient 3),
this was isolated, but in the two other cases, further high-grade injuries to
the clavicular components (one grade 3 and one grade 2) were identified.
Patient 1 underwent surgery, which confirmed the grade 3 myotendinous tear of
the abdominal and manubrial heads and the grade 2 tear of the clavicular
component. Scar tissue and adhesions were noted between the retracted proximal
components and the overlying deltoid fascia. The findings on MRI for this case
were identical to those of sonography. Surgical repair was performed with a
good functional outcome at 6 months. In the other two cases, both patients
(patients 2 and 3) declined surgery and were satisfied with the functional
outcome at 6 months (patient 2 had already decided to retire from the
sport).
The fourth case was found to have a partial (grade 2) tear at the proximal
myotendinous junction of pectoralis minor with a large hematoma. There was
subsequent clinical concern for a compartment syndrome, and the hematoma was
evacuated surgically with confirmation of a grade 2 pectoralis minor
myotendinous tear.
The fifth case had a partial (grade 2) tear at the origin of the sternal
head of the pectoralis major muscle involving the muscle and investing
aponeurotic fascia at its attachment to the sternum. The patient recovered
full function after physiotherapy and was discharged at 3 months.
Discussion
To our knowledge, the sonographic features in relation to injuries to the
pectoralis muscles have not been described. The complex anatomy of the
pectoralis major muscle with its twisting trilaminar tendon and differing
fiber lengths make it a very efficient muscle, requiring relatively large
force vectors to produce injury
[1,
3].
Three previous studies have reviewed MRI in the assessment of pectoralis
major muscle injury before surgery
[5,
7,
8]. In total, these series
reported 29 cases collected over periods of 5-8 years
[5,
7,
8]. The patients were
predominantly young male athletes with no women reported, and weight lifting
(usually bench-pressing) was the most common mechanism of injury (24/29).
Carrino et al. [5] reviewed
nine cases; however, partial tears were not reliably graded and complete tears
were not characterized by the head/lamina involved. Most injuries occurred at
the enthesis (7/9), compared with only two (2/9) at the myotendinous junction
[5]. The authors stated that it
was difficult to differentiate separate areas of the muscle and tendon on MRI
and hypothesized that an ABER position may better show the distal myotendinous
junction and enthesis [5]. This
position was evaluated on sonography in all our patients because it helped to
stress dynamically the myotendinous junction, allowing accurate tear grading
(Fig. 3C).
A study of cadavers, volunteers, and five clinical cases presented by Lee
et al. [8]. concluded that it
was difficult on routine MRI to differentiate the tendons and muscle laminae
in cadavers and volunteers. The predominance of clinical injuries was at the
distal enthesis (4/5) with the remaining injury affecting the myotendinous
area. In our study, we found that sonography could differentiate the three
main muscle heads originating to form the tendon laminae of the pectoralis
major muscle (Figs. 1A,
1B,
1C,
1D, and
1E). More distally, the
myotendinous junction and tendon could be easily identified, but the separate
components of the tendon could not be differentiated. This is not surprising
for either imaging technique because the three laminae blend with no
significant separating connective tissue to provide contrast resolution.
Connell et al. [7]
retrospectively reviewed 15 cases with most injuries (9/15) at the distal
insertion, which were usually complete and involving both heads, whereas the
other six injuries were predominantly partial myotendinous junction tears
involving only one head (sternal). Connell et al., along with other authors
[4], propose that more severe
injuries result in complete tears of the enthesis, whereas lower grade forces
lead to a partial myotendinous tear of that head.
Our study does not support this hypothesis because although complete tears
did occur more frequently, these were all myotendinous tears involving at
least the sternal head, consistent with the proposed injury biomechanics of
Wolfe et al. [3], that this
area is the first to undergo strain. We suspect that injuries of the enthesis
may occur with the severe exaggerated loading seen in bench-pressing injuries,
the predominant mechanism in many series but absent in ours. Our study also
emphasizes the importance of the nonathletic mechanisms involved in falling
and lifting, which may also produce complete tears but may be of a
sufficiently different vector that it does not affect the enthesis.
Four clinical series have reported a good functional outcome, with both
early and delayed surgery for complete pectoralis major tears
[2-4,
6]. These series presented 43
clinical injuries (male athletes) with surgical findings in 34 cases. The most
common mechanism of injury was bench-pressing, and one article proposed that
pectoralis major tears were almost exclusively athletic injuries
[6]. All these studies
confirmed difficulty in clinically differentiating partial and complete tears
because injuries at the distal abdominal and manubrial myotendinous junction
(or enthesis) can be masked by the overlying intact clavicular fibers (because
of the tendon twist) [3,
6,
8].
Pavlik et al. [4] reviewed
the reports of seven athletes collected over 15 years and mentioned sonography
in two cases, but no specific details were provided
[4]. At surgery, most injuries
were myotendinous (5/7) in comparison with enthetic injuries (2/7). McEntire
et al. [2] reviewed the
literature (as it was in 1972), and although athletic injuries were most
commonly reported, injuries due to falls and direct blows were also described.
They presented six complete tears with an equal incidence of myotendinous and
injuries of the enthesis. Wolfe et al.
[3] presented seven surgical
cases with four tears at the distal myotendinous junction of the sternal head
and three tears at the humeral enthesis. One of their cases was a chronic
presentation, with diffuse adhesions found at surgery, similar to patient 1 in
our series. These adhesions coalesced to form a pseudotendon (between the
retracted muscle and actual tendon), which they described as being important
to recognize and dissect for effective surgical repair
[1,
3,
4]. This pseudotendon and its
adherence were easily identified on sonography in our series (Figs.
2A,
2B, and
2C).
Overall these clinical series describe complete tears occurring slightly
more commonly at the myotendinous junction, concurring with our series but
contradicting other imaging series. Perhaps this difference is due to chance
because a similar distribution should be expected, given that the MRI and
clinical series both consisted of young male athletic injuries. A unique
feature of our series is a female patient with a proximal muscular and
aponeurotic injury of the sternal head, which, to our knowledge, has not been
previously reported in either the clinical or imaging literature
(Fig. 6).
Limitations in this report include the number of patients and the relative
lack of surgical correlation. However, we believe that our patient population
was different from those in previously reported series with the spectrum of
injuries consisting of forced abduction and extension of the humerus while
breaking a fall. Although all patients were being considered for orthopedic
referrals, they were imaged at a much earlier stage in treatment, therefore
reducing the potential bias of studying only surgical candidates. This feature
could also explain the relatively high number of cases obtained over this
2-year period.
In conclusion, we report the use of high-frequency sonography in the
assessment of injuries to the pectoralis muscles and have shown it to
accurately assess the separate muscular components, myotendinous junction, and
enthesis of the muscles. This article shows that sonography should be
considered for initial assessment or as a complement to MRI in this region
because it allows accurate and rapid dynamic evaluation, which is essential
for defining surgical intervention in these complex injures.
Acknowledgments
We thank D. Limb (orthopedic surgeon). S. Riley (sonographer), and the
medical illustration department (Leeds Teaching Hospitals) for their help in
preparing this manuscript.
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Abstract
Introduction
