DOI:10.2214/AJR.05.0319
AJR 2006; 187:W169-W174
© American Roentgen Ray Society
MRI Diagnosis of Contracture of the Gluteus Maximus Muscle
Clement K. H. Chen1,2,3,
LeeRen Yeh1,2,
Wei-Ning Chang4,5,
Huay-Ben Pan1,2 and
Chien-Fang Yang1,2
1 Department of Radiology, Kaohsiung Veterans General Hospital, 386 Ta-Chung 1st
Rd., Kaohsiung 813, Taiwan.
2 Department of Radiology, School of Medicine, National Yang-Ming University,
Taipei 112, Taiwan.
3 Yuh-Ing Junior College of Health Care and Management, Kaohsiung 807,
Taiwan.
4 Department of Orthopaedics, Kaohsiung Veterans General Hospital, Kaohsiung
813, Taiwan.
5 Department of Surgery, School of Medicine, National Yang-Ming University,
Taipei 112, Taiwan.
Received February 24, 2005;
accepted after revision April 6, 2005.
Supported by grant VGHKS90-57 from Kaohsiung Veterans General Hospital,
Taiwan.
Address correspondence to C. K. H. Chen
(ckhc6203{at}yahoo.com.tw).
WEB
This is a Web exclusive article.
Abstract
OBJECTIVE. The objective of our study was to describe MRI features
of contracture of the gluteus maximus muscle after providing a retrospective
review of the MRI studies of 21 patients.
CONCLUSION. Gluteal contracture manifests characteristic features on
MRI, including an intramuscular fibrotic cord extending to the thickened
distal tendon with atrophy of the gluteus maximus muscle and posteromedial
displacement of the iliotibial tract. In advanced cases, medial retraction of
the muscle and its tendon results in a depressed groove at the muscle-tendon
junction and external rotation of the proximal femur. Clinical correlation and
meticulous physical examination may confirm the MR diagnosis.
Keywords: buttocks • contracture • hip • MRI • muscles • musculoskeletal imaging
Introduction
Contracture of the gluteus maximus muscle (gluteal contracture) is well
documented in the orthopedics literature
[1-3].
Most of the patients reported are school-age children (6-18 years old) and the
lesions are secondary to multiple intramuscular injections in the buttocks
[1-4].
Intramuscular fibrosis with subsequent retraction of the scar tissue accounts
for the contracture of the hip. This is a clinical diagnosis characterized by
physical deformities and abnormal postures: extension, abduction, and external
rotation deformity and the resultant limitation of flexion and adduction of
the affected hip. Advanced imaging studies are not necessary to make the
diagnosis. We had, however, the opportunity to examine the MRI studies of 21
patients with gluteal contracture during a 7-year period. The characteristic
MRI features of gluteal contracture, to our knowledge, have never been
reported.
Materials and Methods
Patient Group
From April 1998 to December 2004, we performed MRI on 21 patients with a
clinical diagnosis of gluteal contracture. The patients included a 4-year-old
girl, two 23-year-old women, and 18 men (age range, 18-26 years; mean, 22
years). They complained of variable degrees of limitation in flexion and
adduction of both hips and thighs and difficulty in squatting. A history of
injections in the buttocks was obtained in all patients. Details about the
frequency, duration, and medications of the injections could not be traced,
however. Frontal radiographs and MR images of the pelvis were available for
all patients.
The diagnosis of gluteal contracture was made clinically by its
characteristic physical abnormalities. Contracture of the gluteus maximus
muscle results in variable degrees of extension, abduction, and external
rotation deformity and a limited flexion and adduction of the affected hip
[1,
2]. Orthopedists perform a
so-called squatting test, active or passive, to make the diagnosis. In the
active squatting test, the physician asks the patient to squat with both knees
close together. The test is positive if the patient fails to squat in this
posture and ultimately falls backward. The examiner then flexes one of the
patient's hips, bringing the knee to the chest. In the meantime, the
contralateral thigh is pushed onto the table. In healthy adults, this flexion
of the hip ranges 121° ± 13° (mean ± SD) degrees
[5]. If there is resistance and
hip flexion is limited to less than 90°, the test is positive. The factor
of femoral retroversion is excluded by examining the hip rotation in a prone
position. All 21 patients were reported positive for both the active squatting
test and the hip flexion test without femoral retroversion.
MRI of the pelvis including buttocks and hips was performed with a 1.5-T
scanner (Signa, GE Healthcare), with a standard torso coil and the patient
lying in a supine position. The following pulse sequences were used: spin-echo
T1-weighted axial images (TR/TE, 500/minimal; 7-mm section thickness; 7-mm
intersection gap; 44 cm field of view; 256 x 192 matrix; and 1
acquisition); fat-saturated fast spin-echo proton density-weighted axial
images (3,500/42, 4-mm section thickness, 0.5-mm intersection gap, 256 x
192 matrix, 44-cm field of view, 2 signals averaged); spin-echo T1-weighted
coronal (or oblique coronal along the axis of gluteus maximus muscle) images
of both buttocks (400/minimal, 4-mm section thickness, 0.5-mm intersection
gap, 34-cm field of view, 256 x 160 matrix, and 1.5 acquisitions);
fat-saturated fast spin-echo proton density-weighted coronal (or oblique
coronal along the axis of gluteus maximus muscle) images of both buttocks
(3,000/42, 4-mm section thickness, 0.5-mm intersection gap, 256 x 160
matrix, 34-cm field of view, 2 signals averaged); and spin-echo T1-weighted
sagittal images (500/minimal, 8-mm section thickness, 6-mm intersection gap,
34-cm field of view, 256 x 192 matrix, 1 acquisition).
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Fig. 1A —19-year-old man as healthy volunteer. Spin-echo T1-weighted
coronal image (TR/TE, 567/16) shows coarsely fasciculated healthy gluteus
maximus muscle (Gmax) in superficial portion of buttock. It is quadrilateral
with its fasciculi directed downward and outward obliquely. Fat streaks are
evenly distributed in muscle. In muscle portion medial to greater trochanter,
low-signal-intensity tendon is barely seen.
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Fig. 1B —19-year-old man as healthy volunteer. Spin-echo T1-weighted
coronal image (567/16) shows healthy gluteus maximus muscle (Gmax) inserts on
iliotibial tract of fascia lata (black arrow) around lateral aspect
of greater trochanter. Lowermost portion of its tendon (white arrow)
curves medially and posteriorly to gluteal ridge of femur. Gmed = gluteus
medius muscle.
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Fig. 2A —21-year-old man with unilateral (right-side) gluteal
contracture. Healthy left buttock can be used for comparison. Spin-echo
T1-weighted coronal image (TR/TE, 567/16) of both buttocks discloses thin
low-signal-intensity fibrotic cord (white arrows) coursing obliquely
in atrophic right gluteus maximus muscle.
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Fig. 2B —21-year-old man with unilateral (right-side) gluteal
contracture. Healthy left buttock can be used for comparison. Spin-echo
T1-weighted axial image (600/16) at lower portion of both buttocks shows
atrophic and medial retraction of right gluteus maximus muscle
(arrowhead), thickening and mild retraction of its tendon and
iliotibial tract (black arrows), and depressed groove at
muscle-tendon junction. More anteverted axis of right femoral neck
(double-headed arrows) suggests mild external rotation of right
femur. Healthy left gluteus maximus muscle extends to lateral aspect of
greater trochanter and inserts on iliotibial tract (white arrow).
Gmax = gluteus maximum muscle.
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Control Group
We performed MRI on 10 age-matched women (age range, 19-22 years; mean, 21
years) and 10 age-matched men (age range, 19-27 years; mean, 22 years) as the
control population to set up the normal reference standards of MRI. The MRI
protocol and parameters were the same as those used for imaging the patient
group. This investigation was conducted with the approval of the institutional
review boards of our hospital. Informed consent for MRI was obtained from the
volunteers.
Results
Among the 21 patients, 17 had a contracture of the bilateral gluteus
maximus muscles. The remaining four patients had lesions on the right buttock
only. Thus 38 muscles (or buttocks) were affected in total. Frontal
radiographs of the pelvis are not helpful for the diagnosis of gluteal
contracture. According to the medical records, none of the patients had a
surgical correction in our hospital after the MRI study.
Healthy MRI Appearance of the Gluteus Maximus Muscle
The gluteus maximus muscle is a heavy, coarsely fasciculated muscle in the
superficial portion of the buttock. It is quadrilateral with its fasciculi
directed downward and outward obliquely
(Fig. 1A) from the medial
superior aspect of the buttock to its insertions into the iliotibial tract and
gluteal tuberosity of the femur around the greater trochanter
(Fig. 1B). On the MRI of the
healthy control group, this muscle was symmetric in size, shape, and signal
intensity on both sides. Fat streaks were evenly distributed in the muscle
(Fig. 1A) that should not be
mistaken for fibrotic bands on fat-suppressed images. The muscle extends
inferiorly to the lateral aspect of the greater trochanter and inserts on the
iliotibial tract (Figs. 1B and
2B, left side). The tendon
portion is only visible over the lateral inferior aspect of the muscle around
the greater trochanter. The lowermost portion of the tendon curves medially
and posteriorly to the gluteal ridge of the femur
(Fig. 1B). In the muscle
portion medial to the greater trochanter, the low-signal-intensity tendon is
barely seen.
Abnormal MRI Features of the Gluteus Contracture
Table 1 summarizes the
abnormal MRI findings of the 21 patients. All 38 buttocks showed primary
features of muscle atrophy (Figs.
3A,
3C,
4A, and
4B) and intramuscular fibrotic
cord (Figs. 2A,
3A,
3B,
3C,
3D,
3E,
4A, and
4B) contiguous to the
iliotibial tract (Figs. 3A,
3B,
3C,
3D,
3E,
4A, and
4B). The fibrotic cord
manifested low signal intensity on all sequences and was most obvious on
fat-suppressed images. Severe cases with evident atrophy over the upper and
middle thirds of the muscle and thick retracted fibrotic cord and tendon
(Figs. 3A,
3B,
3C,
3D, and
3E) were noted in nine buttocks
of six patients. The upper third of the muscle was affected in 23 buttocks of
15 patients. The middle third of the muscle was affected in the remaining six
buttocks of four patients. Retraction of the thickened tendon and fibrotic
cord accounted for the secondary MRI features: medial posterior displacement
of the iliotibial tract behind the greater trochanter (Figs.
3A,
3B,
3C,
3D,
3E,
4A, and
4B), medial retraction of the
affected gluteus maximus muscle, depressed groove at the muscle tendon
junction (Figs. 2B,
3A,
3B,
3C,
3D,
3E,
4A, and
4B), and external rotation of
the hip (Figs. 2B,
3D, and
4B). These secondary features
were evident in 13 buttocks of nine patients.
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Fig. 3A —20-year-old man with bilateral gluteal contracture. Spin-echo
T1-weighted oblique coronal image (TR/TE, 400/16) of right buttock discloses
thick fibrotic cord (black arrow) and surrounding atrophic gluteus
maximus muscle (arrowhead).
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Fig. 3C —20-year-old man with bilateral gluteal contracture. Spin-echo
T1-weighted axial image (600/11) of both buttocks discloses atrophic and
medial retraction of gluteus maximus muscles (arrowheads), fibrotic
cords (white arrows), and thickening and retraction of distal tendons
and iliotibial tracts (black arrows).
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Fig. 4A —23-year-old woman suffering from bilateral gluteal
contracture that is more severe on left side. Patient related history of
repeated injections in both buttocks since adolescence. Spin-echo T1-weighted
axial image (TR/TE, 566/16) discloses atrophic and medial retraction of left
gluteus maximus muscle (arrowhead), thickening and retraction of
fibrotic cord and distal tendon (white arrow), and displacement of
iliotibial tract (black arrow).
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Fig. 4B —23-year-old woman suffering from bilateral gluteal
contracture that is more severe on left side. Patient related history of
repeated injections in both buttocks since adolescence. Spin-echo T1-weighted
axial image (566/16) inferior in relation to A discloses atrophic left
gluteus maximus muscle (arrowhead), thickening and retraction of
distal tendon and iliotibial tract (black arrows) posterior to left
femur. Angle formed by lines of connecting ischia (black line) and
axis of femoral necks (double-headed arrows) measures 9° on right
side and 36° on left side. Exaggerated anteverted axis of left femoral
neck suggests external rotation of left proximal femur.
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Fig. 3B —20-year-old man with bilateral gluteal contracture.
Fat-saturated fast spin-echo proton density-weighted oblique coronal image
(2,000/48) anterior to A shows marked thickening, shortening, and
straightening of gluteus maximus muscle tendon and iliotibial tract (black
arrow).
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Fig. 3D —20-year-old man with bilateral gluteal contracture. Spin-echo
T1-weighted axial image (600/11) inferior in relation to C discloses
atrophic and medial retraction of gluteus maximus muscles, thickening and
retraction of distal tendons and iliotibial tracts (black arrow)
posterior to proximal femurs, and resultant depressed grooves at muscle-tendon
junctions. Exaggerated anteverted axis of femoral neck (double-headed
arrow) suggests external rotation of proximal femur.
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Fig. 3E —20-year-old man with bilateral gluteal contracture. Spin-echo
T1-weighted sagittal image (500/16) discloses thick fibrotic cord (white
arrow) and surrounding muscle atrophy (arrowheads).
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Discussion
Fibrous muscular contracture with deformity and dysfunction of the adjacent
joint is well documented in the orthopedics literature. The disorder can be
congenital [6,
7], for example, of the
sternocleidomastoid muscle in congenital torticollis
[8], or injection myopathy
secondary to repeated intramuscular injections
[1-3,
9-12].
A constitutional fibrogenic diathesis has also been reported as an important
factor in the latter condition
[13,
14]. The commonly affected
muscles are the quadriceps femoris
[15], deltoid brachii
[12], gluteus maximus
[2], and triceps brachii
[16]. All are common sites of
intramuscular injection.
The gluteus maximus muscle is a coarsely fasciculated muscle in the
superficial portion of the buttock. It is quadrilateral, and its fasciculi are
directed downward and outward. The muscle arises from the posterior gluteal
line of the ilium and the area of the bone above and behind it, the posterior
surface of the sacrum and coccyx, the sacrotuberal ligament, and the gluteal
aponeurosis overlying the gluteus medius muscle. The larger upper portion and
the superficial fibers of the lower portion insert into the iliotibial tract
of the fascia lata; the deeper fibers of the lower portion reach the gluteal
tuberosity of the femur and the lateral intermuscular septum. This muscle
functions as a powerful extensor, abductor, and lateral rotator of the thigh
[17].
The diagnosis of fibrous muscular contracture, including gluteal
contracture, is made clinically by the characteristic physical deformities and
limited motions of the adjacent joint or limb
[1,
2]. MRI, however, may be
requested for evaluation of the affected muscle, including the extent of
fibrosis and degree of muscle atrophy. In 1998, Chen et al.
[12] reported the radiographic
and MRI features of deltoid muscle contracture. Many points in their report
are also applicable to gluteal contracture. Retraction of the fibrotic cord in
the deltoid muscle results in abduction and internal rotation deformity of the
proximal humerus. Similarly, retraction of the fibrotic cord in the gluteus
maximus muscle can induce abduction, extension, and external rotation
contracture with limited flexion and adduction of the proximal femur and hip
joint. As a result, the patient can only squat or sit in the frogleg position
with the legs wide apart, hips externally rotated and abducted. Inspection and
palpation may disclose tight, atrophic, and medially displaced gluteus maximus
muscle, focal skin retraction, and a palpable hard cordlike mass in the
buttock [2]. A positive
squatting test is clinically diagnostic.
Intramuscular fibrotic cord and muscle atrophy are the two major MRI
features of fibrous muscular contracture
[12]. These features were
present in all of our patients. The muscle atrophy affected most commonly the
upper third of the gluteus maximus (84%; 32/38 buttocks), which is related to
the injection technique. To avoid injury to the sciatic nerve, intramuscular
injection to the buttock is most commonly given at its superolateral
portion.
The muscle atrophy of gluteal contracture involves mainly the superior
portion of the gluteus maximus surrounding the intramuscular fibrotic band
(Figs. 3A,
3B,
3C,
3D, and
3E). These features can be
easily distinguished from atrophy occurring in other disease entities such as
disuse, denervation, chronic inflammatory myopathy, chronic compartment
syndrome, and so on.
None of our patients had surgical correction in our hospital. In cases of
severe contracture or for cosmetic reasons, however, surgery is the only way
to correct the deformity [2].
Conservative measures such as passive stretching are usually not helpful.
Surgery may be accomplished by division of the fibrotic cords and transverse
fasciotomy of the iliotibial tract. A Z-plasty may also be performed to
lengthen the gluteus maximus tendon
[1,
2]. Surgical results are
positive in the literature.
The retraction of the fibrotic cord, resultant shortening of the tendon,
and the extent of muscle atrophy are important determinants of the degree of
the lesion. MRI can both establish the diagnosis for inexperienced clinicians
and also provide an evaluation of lesion severity. In our opinion, the more
thickening and retraction of the fibrotic cord, the more severe is the
clinical abnormality. Because this is a retrospective study, detailed
measurements of the restriction of motion were not available in the medical
records. Therefore the relationship of the degree of clinical abnormality with
the degree of MRI abnormality could not be confirmed in our study.
Our study had limitations. The first was the absence of histologic
correlation of the intramuscular low-signal-intensity bands. The shape of the
lesion, the homogeneous low signal intensity, surrounding muscle atrophy, and
characteristic physical deformity, however, may exclude diagnosis of
fibromatosis or posttraumatic hemosiderin deposition
[12]. Second, a detailed
history of injections into the buttocks could not be obtained in most cases.
The relationship between gluteal contracture and intramuscular injections is
at best speculative. Third, obvious selection bias was apparent in our patient
population. We did not have results of MRI for patients with mild deformity to
validate the efficacy of MRI for early cases.
In conclusion, gluteal contracture manifests characteristic features on
MRI, including intramuscular fibrotic cord extending to the thickened distal
tendon and iliotibial tract with atrophy of the gluteus maximus muscle. In
advanced cases, medial retraction of the muscle and its tendon results in a
depressed groove at the muscle-tendon junction and external rotation of the
proximal femur. Clinical correlation and meticulous physical examination may
confirm the MR diagnosis.
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Abstract
Introduction
