AJR 2005; 184:1490-1494
© American Roentgen Ray Society
MRI of the Rotator Interval Capsule
Olivier P. Krief1
1 Service Radiologie, Polyclinique Atlantique, rue Claude Bernard Le Tillay
BP419, Saint Herblain cedex 44819, France.
Received May 12, 2004;
accepted after revision October 22, 2004.
Address correspondence to O. P. Krief
(okrief{at}yahoo.fr).
Introduction
The rotator cuff interval is a triangular space between the subscapularis
and supraspinatus tendons and the base of the coracoid process, covered by the
rotator interval capsule, whose main component is the coracohumeral ligament
(CHL). The rotator cuff interval contains the long head of the biceps tendon
(LBT) and the superior glenohumeral ligament (SGHL)
[1–6].
The relationships between the CHL, the SGHL, and the LBT are complex and may
be difficult to analyze on MRI because of the variable appearance of the
CHL.
This pictorial essay reviews the normal anatomy of the CHL and SGHL and the
lesions of these ligaments that may explain the occurrence of biceps
tendinopathy in the presence of full-thickness tears of the cuff.
Normal Anatomy of Rotator Interval Capsule
The rotator cuff interval is a triangular space created by the intervention
of the coracoid process between the subscapularis and supraspinatus muscles
and tendons. The floor of the rotator cuff interval is the cartilage of the
humeral head, and the roof of the rotator cuff interval is the rotator
interval capsule, which links the subscapularis and supraspinatus tendons and
is composed of two layers: the CHL on the bursal side and the fasciculus
obliquus on the articular side
[7]. These two layers cannot be
differentiated on macroscopic analysis or on imaging but only on the basis of
histologic examination from the different orientation of their bundles on
polarized light analysis.
CHL
The CHL bridges the rotator cuff interval and its content—that is,
the LBT and the SGHL (Fig. 1).
Gross and histologic analysis shows that the CHL does not correspond to a true
ligament but rather to a variable-thickness local capsular reinforcement with
a broad lateral insertion on the lesser and greater tubercles
[4,
8]. The CHL shows the typical
capsular, layered pattern of sheets and bundles of collagenous tissue
interspersed with strands of loose connective tissue and vascular channels and
has been compared with the iliofemoral ligament of the hip
[8].
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Fig. 1. —Drawing, according to Gohlke et al.
[7], of rotator cuff interval
in sagittal plane, with superior capsular complex (in green),
bridging subscapularis tendon (SSC), superior glenohumeral ligament (SGHL),
and long portion of biceps tendon (LPB) and passing beneath deep fibers of
supraspinatus (SSP). (Courtesy of F. Gohlke, Wuerzburg, Germany)
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Clark and Harryman [3]
described five histologic layers to the rotator cuff and showed that the CHL
blends with the most superficial layer (layer 1) and the deepest layer (layer
5) (Fig. 2A,
2B). Layers 2 and 3 are
composed of the dense collagenous fibers of the supraspinatus tendon, and
layer 4 is composed of loose connective tissue.
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Fig. 2A. —Histologic layers of rotator cuff as described by Clark and
Harryman [3]. Coracohumeral
ligament (CHL) encases anterior portion of supraspinatus tendon (SSP), with
most superficial layer (layer 1) and deepest layer (layer 5) above and beneath
SSP fibers arising from CHL. Drawing shows relationships between CHL,
subscapularis tendon (SSc), SSP, and infraspinatus tendon (IS). LPB = long
portion of biceps tendon.
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Fig. 2B. —Histologic layers of rotator cuff as described by Clark and
Harryman [3]. Coracohumeral
ligament (CHL) encases anterior portion of supraspinatus tendon (SSP), with
most superficial layer (layer 1) and deepest layer (layer 5) above and beneath
SSP fibers arising from CHL. Sagittal fast spin-echo T2-weighted MR image in
54-year-old man shows multilayered appearance of CHL with visible extension of
fibers to superficial and deep layers of SSP (arrows).
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The rotator cuff interval shrinks laterally, and the lateral portion of the
rotator cuff interval is much more difficult to analyze than is its mid
portion. The lateral portion of the CHL blends with fibers from the
supraspinatus and subscapularis tendons to form a homogeneous fibrous plate,
and even histologic differentiation of CHL fibers from the cuff tendon fibers
is difficult [4].
SGHL
The SGHL originates on the superior tubercle of the glenoid anterior to the
insertion of the biceps tendon, with a lateral insertion on the superolateral
portion of the lesser tubercle beneath the superior edge of the subscapularis
tendon [1]. The mid portion of
the rotator cuff interval appears as a front-oriented band with a T-shaped
link to the CHL (Figs. 3 and
4). The distal portion blends
with the CHL to form an anterior suspension sling anterior to the biceps
responsible for the stability of the LBT
[1]. The posterior attachment
of the CHL to the supraspinatus tendon pulls back the anterior sling and
provides stability to this sling, preventing subluxation of the LBT over the
anterior ridge of the intertubercular groove
[5].
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Fig. 3. —Drawing of anatomy of rotator cuff interval and relationships
between coracohumeral ligament (CHL), superior glenohumeral ligament (SGHL),
supraspinatus tendon (SSP), and long portion of biceps tendon (LBT). In mid
portion of rotator cuff interval, SGHL appears as front-oriented band with
T-shaped link to CHL. In distal portion, SGHL and CHL form anterior sling
around LBT, responsible for stability of biceps at entrance of intertubercular
groove. (Reprinted with permission from
[5])
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Fig. 4. —Appearance of normal anatomy of mid rotator cuff interval in
presence of intraarticular effusion on sagittal fast spin-echo T2-weighted MR
image in a 49-year-old woman. Coracohumeral ligament (arrowhead)
appears flat, with homogeneous, low signal intensity, and coracohumeral
ligament and superior glenohumeral ligament (long arrow) are
perpendicular, with T-shaped link anterior to long portion of biceps tendon
(short arrow).
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MRI Anatomy of Rotator Interval Capsule and SGHL
CHL
The CHL is always well identified in the mid portion of the rotator cuff
interval and is visualized on all planes, but sagittal images are the most
useful for analysis of this structure. Because the CHL does not correspond to
a true ligament but rather to a capsular fold, its appearance depends on the
presence or absence of intraarticular fluid. In the presence of intraarticular
effusion, the CHL appears flat, with homogeneous, low signal intensity
[9] (Fig.
2A,
2B). In the absence of
effusion, the CHL and the SGHL fill the anterior portion of the rotator cuff
interval between the subscapularis and the LBT and display a heterogeneous
signal intensity that reflects the capsular nature of the CHL (Figs.
1 and
5). Then, the CHL bridges the
biceps to pass beneath the supraspinatus tendon, blending with the capsular
layer. The CHL cannot be differentiated at this level from the capsule on
images and on histologic study, because both structures display the same
histologic features. The high-signal-intensity interface that is between the
layer arising from the CHL and the supraspinatus
(Fig. 5) could correspond to
the layer 4 made of loose connective tissue described by Clark and Harryman
[3]. They showed that the CHL
extension blends with the superficial and deep layers of the supraspinatus. A
clearly multilayered appearance of the CHL as described by Clark and Harryman
is seen on MR images in fewer than 10% of patients (Fig.
2A,
2B). On MR images, the
insertion of the CHL on the greater tubercle cannot be differentiated from the
insertion of the supraspinatus tendon.
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Fig. 5. —Appearance of normal anatomy of rotator cuff interval in
absence of intraarticular effusion on sagittal fast spin-echo fat-suppressed
proton density–weighted MR image in a 63-year-old woman. Coracohumeral
ligament (CHL) and superior glenohumeral ligament (black arrowhead)
fill anterior portion of rotator cuff interval between subscapularis tendon
and long portion of biceps tendon, and the two ligaments cannot be
differentiated. CHL bridges biceps tendon and appears to pass beneath
supraspinatus tendon (thick white arrow), to blend with capsular
layer (white arrowhead) (compare with Fig. 1). Interface of high
signal intensity (thin white arrow) is always visible between fibers
of CHL and supraspinatus tendon and may correspond to layer 4 of Clark and
Harryman [3], made of loose
connective tissue, between these two layers.
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SGHL
The SGHL is visualized on MRI only in the presence of intraarticular
effusion. In the absence of effusion, both the CHL and the SGHL fill the
anterior portion of the rotator cuff interval and cannot be differentiated
(Fig. 6A,
6B). In the presence of
effusion, the SGHL appears on sagittal images as a front-oriented band having
a T-shaped link with the CHL anterior to the LBT
(Fig. 4). On axial images, in
the presence of intraarticular effusion, the SGHL appear as an anterior convex
band anterior to the LBT (Fig.
6A,
6B).
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Fig. 6A. —Appearance of normal superior glenohumeral ligament on
sagittal and axial fast spin-echo fat-suppressed proton density–weighted
MR images in a 45-year-old woman. On sagittal (A) and axial (B)
slices, superior glenohumeral ligament (arrowheads) is well outlined
by intraarticular contrast material. Axial slice is at level of black line on
sagittal slice, through upper portion of rotator cuff interval. Superior
glenohumeral ligament (white arrows) is seen on axial slice as
anterior convex band anterior to long portion of biceps tendon.
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Fig. 6B. —Appearance of normal superior glenohumeral ligament on
sagittal and axial fast spin-echo fat-suppressed proton density–weighted
MR images in a 45-year-old woman. On sagittal (A) and axial (B)
slices, superior glenohumeral ligament (arrowheads) is well outlined
by intraarticular contrast material. Axial slice is at level of black line on
sagittal slice, through upper portion of rotator cuff interval. Superior
glenohumeral ligament (white arrows) is seen on axial slice as
anterior convex band anterior to long portion of biceps tendon.
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MRI of Lesions of Rotator Interval Capsule in Presence of Supraspinatus Tendon Tears
Anterior extension of supraspinatus tendon tears involves the rotator
interval capsule. This involvement explains the occurrence of biceps
tendinopathies associated with cuff tears, because, as previously described,
the CHL covers and protects the intraarticular portion of the long portion of
the biceps and assumes with the SGHL the stability of the biceps tendon. MRI
allows accurate identification of the CHL and SGHL in the presence of
full-thickness tears (Figs. 7,
8,
9,
10,
11A,
11B). Biceps tendinopathy may
occur at the level of the intertubercular groove, in its intraarticular
portion, or at both locations
[10]. The causes of biceps
tendinopathy in the presence of a cuff tear are multiple
[10,
11]: With a full-thickness
tear of the supraspinatus with respect to the CHL, the CHL still covers the
superficial aspect of the LBT and protects it from direct impingement with the
acromion and the coracoacromial ligament
(Fig. 7). When anterior
extension of the tear occurs, the biceps is no longer covered by the CHL and
may impinge with the coracoacromial ligament (Figs.
8 and
9). Moreover, release of the
anterior sling leads to LBT instability over the anterior ridge of the
intertubercular groove [5,
7] (Figs.
10 and
11A,
11B).
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Fig. 7. —Appearance of full-thickness tear of supraspinatus tendon
with respect to coracohumeral ligament (arrowhead) on sagittal fast
spin-echo T2-weighted MR image in a 58-year-old man. Coracohumeral ligament
continues to cover superficial aspect of long portion of biceps tendon
(arrow) and to protect long portion of biceps against direct
impingement with coracoacromial ligament.
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Fig. 8. —Appearance of full-thickness tear of SSP with discontinuity
of coracohumeral ligament (black arrow) on sagittal fast spin-echo
T2-weighted MR image in a 66-year-old man. Long portion of biceps tendon
(white arrow) appears flattened and is no longer covered by remnant
of coracohumeral ligament.
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Fig. 9. —Appearance of full-thickness tear of supraspinatus tendon
involving coracohumeral ligament (white arrows) on sagittal fast
spin-echo T2-weighted MR image in a 59-year-old woman. Humeral head ascends,
although long portion of biceps (black arrow) remains continuous, and
biceps appears squeezed between humeral head and coracoacromial ligament.
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Fig. 10. —Drawing of release of anterior sling. Coracohumeral ligament
(straight arrow) and superior glenohumeral ligament form U-shaped
sling anterior to long portion of biceps tendon, and release of sling at
junction of coracohumeral ligament and SSP allows anterior subluxation of long
portion of biceps tendon over anterior ridge of intertubercular groove. Curved
arrow indicates coracohumeral ligament torn and retracted (Reprinted with
permission from [5])
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Fig. 11A. —Appearance of rupture of anterior sling with anterior
subluxation of long portion of biceps tendon on MR images in a 71-year-old
woman. On sagittal fast spin-echo T2-weighted image, superior glenohumeral
ligament (thin arrow) and anterior portion of coracohumeral ligament
(thick arrow) remain continuous, but sling is ruptured at junction of
coracohumeral ligament and supraspinatus fibers.
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Fig. 11B. —Appearance of rupture of anterior sling with anterior
subluxation of long portion of biceps tendon on MR images in a 71-year-old
woman. On axial fat-suppressed proton density–weighted image, long
portion of biceps tendon is flattened, with subluxation on anterior ridge of
intertubercular groove (arrowhead), abnormal signal on its anterior
part, and fluid into bicipital sheath. Articular side lesions of subscapularis
tendon are clearly seen, with high signal intensity (arrow). For such
a subluxation to occur, anterior sling must be torn, and humeral transverse
ligament may remain continuous.
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Conclusion
The anatomy of the rotator interval capsule is complex and may be confusing
on MRI because of the variable appearance of the CHL, depending on the
presence of intraarticular effusion. The CHL covers and protects the
intraarticular portion of the LBT, and the CHL and SGHL stabilize the biceps
at the entrance of the intertubercular groove. MRI provides a unique
perspective on the anatomy of the rotator cuff capsule, and radiologists
should assess these ligaments on MRI because lesions of the CHL and SGHL
explain the occurrence of biceps tendinopathies associated with rotator cuff
tears. An understanding of the pertinent anatomy of the rotator cuff interval
is necessary for analysis of the tendinopathies of the LBT occurring in the
presence of full-thickness tears of the rotator cuff.
Acknowledgments
Special acknowledgments are due to Frank Gohlke from Wuerzburg University
for Figure 1 and for his much-appreciated comments and to Pierre-Alain Cohen
for manuscript review.
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Introduction
Normal Anatomy of Rotator...
