DOI:10.2214/AJR.08.1590
AJR 2009; 192:526-531
© American Roentgen Ray Society
Idiopathic Chondrolysis of the Hip in Children: Early MRI Findings
Tal Laor1 and
Alvin H. Crawford2
1 Department of Radiology, Cincinnati Children's Hospital Medical Center, 3333
Burnet Ave., Cincinnati, OH 45229-3039.
2 Division of Pediatric Orthopaedic Surgery, Cincinnati Children's Hospital
Medical Center, Cincinnati, OH.
Received July 25, 2008;
accepted after revision September 6, 2008.
Address correspondence to T. Laor
(laor{at}cchmc.org).
Abstract
OBJECTIVE. The objective of our study was to identify the early MRI
findings characteristic of idiopathic chondrolysis of the hip in children.
CONCLUSION. A geometric region of abnormal signal intensity centered
in the proximal femoral epiphysis, accompanied by ipsilateral ill-defined
acetabular bone marrow edema, mild synovial hypertrophy, and minimal if any
joint fluid, in a child with a painful stiff hip are early MRI findings
characteristic of idiopathic chondrolysis.
Keywords: chondrolysis • hip • MRI • pediatric imaging
Introduction
Chondrolysis of the hip is a debilitating disorder that results in
extensive loss of articular cartilage of the proximal femoral epiphysis and
acetabulum with resultant joint space narrowing and restriction of motion. It
was first described by Waldenström
[1] in 1930 in the setting of a
slipped capital femoral epiphysis. Since that initial report, chondrolysis of
the hip also has been described in association with trauma; other disorders,
such as infection and monoarticular arthritis; and lengthy immobilization
[2]. First Jones
[3], then Duncan and colleagues
[4] and Wenger and colleagues
[5], described chondrolysis of
the hip without a definable cause. This entity, subsequently termed
"idiopathic chondrolysis," typically presents in preadolescents or
adolescents as a painful, stiff hip.
Confirmation of the clinical diagnosis of idiopathic chondrolysis of the
hip has historically relied on conventional radiography
[6,
7]. Joint space narrowing,
osteopenia, increased femoral head and neck width, protrusio acetabuli,
lateral femoral buttressing, marginal osteophytes, and premature physeal
fusion are frequently identified
[5,
7]. However, these radiographic
findings are typically seen several weeks to months after the onset of
symptoms [5,
6].
MRI of idiopathic chondrolysis of the hip has been described in a series of
six children imaged within 9 months of symptom onset. At the time of MRI,
these children all showed conventional radiographic signs of advanced disease.
We encountered several children with acute, severe hip pain, limited range of
motion, and limp who were referred for MRI within 6 weeks of symptom onset and
in whom the diagnosis of idiopathic chondrolysis was ultimately made. To our
knowledge, the early MRI characteristics of idiopathic chondrolysis have not
been reported. Therefore, the purpose of this study was to identify the early
MRI findings characteristic of idiopathic chondrolysis in children.
Materials and Methods
Institutional review board approval for this retrospective study was
obtained and informed consent was waived. Over a period of approximately 7
years (May 2000–March 2007), six children (four girls and two boys; age
range, 7 years 5 months–13 years 4 months; mean age, 10 years 8 months)
were referred for MRI evaluation of hip pain. Each child ultimately was
diagnosed with idiopathic chondrolysis. One child underwent imaging of each
hip at different times. Clinical history and presenting symptoms were obtained
from the clinic notes of the referring physician and from patient records in
the radiology information system. The side of pain and duration of symptoms
until the MRI examination were recorded.
All hips were scanned on a 1.5- or 3-T clinical imaging system. Each MRI
study included at least a coronal fat-suppressed fast spin-echo T2-weighted
sequence (1.5 T: TR range/TE range, 2,366–3,820/76–96; echo-train
length or turbo factor, 6–8; matrix, 512–256 x 192; slice
thickness, 3–4 mm; slice gap, 0.5–1 mm; 3 T: TR/TE, 3,000/58;
turbo factor, 7; matrix, 320 x 256; slice thickness, 3 mm; slice gap,
0.5 mm), a coronal T1-weighted sequence (1.5 T: TR range/TE range;
300–450/14–22; matrix, 512–256 x 192; slice thickness,
3–4 mm; slice gap, 0.5–1 mm; 3 T: TR/TE, 800/6.9; turbo factor, 3;
matrix, 320–256 x 192; slice thickness, 3 mm; slice gap, 0.5 mm),
and a coronal fat-suppressed T1-weighted sequence after IV injection of a
gadolinium-based contrast agent (0.2 mL/kg). All coronal sequences included
both hips.
The MRI examinations were reviewed by a staff pediatric musculoskeletal
radiologist with 17 years' experience at the time of the study to document the
following: configuration, location, and average width of marrow signal
abnormality of the proximal femoral epiphysis; marrow signal abnormality of
the adjacent acetabulum; signal intensity and bulk of surrounding musculature;
enhancement pattern of the proximal femoral epiphysis; subjective assessment
of joint space narrowing; maximal synovial thickness; and amount of joint
fluid after IV contrast administration. Conventional radiographs obtained for
evaluation of each patient's symptoms as well as follow-up radiographs were
reviewed. Findings on reports from any additional radiologic imaging performed
within 5 days of the MRI examination were noted.
Results
Table 1 summarizes the
patients' clinical information and MRI findings. Hip pain was present from 10
days to 6 weeks before presentation for MRI in all patients. One child also
had ipsilateral thigh pain and one also had leg pain. Patient 1 had
metachronous symptoms in each hip presenting 10 months apart. Hip stiffness
specifically was described by five patients. No child had an underlying
disorder, acute infection, or known rheumatologic disorder. Two children
underwent bone scintigraphy to further evaluate the pain, and both
examinations were interpreted as "nonspecific synovitis."
MRI examinations showed a geometric configuration of hypointense
T1-weighted and hyperintense T2-weighted signal abnormality centered in the
middle one third of the proximal femur in all patients (Figs.
1A,
1B,
1C,
1D,
2A,
2B,
2C,
3A,
3B,
3C,
4A,
4B). This signal abnormality
extended from the articular surface to the proximal physis and measured
between 5 and 14 mm in average width. After IV contrast administration, six of
the seven abnormal proximal femoral geometric foci showed mild to moderate
diffuse enhancement. The remaining portions of the affected proximal femur
showed a normal enhancement pattern. In one patient, the rectangular area of
signal abnormality showed a predominantly peripheral outline of mild
enhancement (Fig. 4A,
4B). All ipsilateral iliac
bones superomedial to the affected femoral epiphysis showed ill-defined signal
abnormality, and in six of seven hips, this signal abnormality extended into
the ischium. Five hips showed subjective joint space narrowing. All hips
showed synovial thickening and little to no joint effusion. Muscles
surrounding the affected side were considered normal in all children.
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Fig. 1B —10-year-4-month-old girl (patient 2 in
Table 1) with right hip and leg
pain, stiffness, and limp for 2–3 weeks. Coronal T1-weighted image
(TR/TE, 800/6.9) of pelvis obtained at 3 T shows geometric focus of abnormal
signal intensity (arrow) in middle one third of proximal right
femoral epiphysis.
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Fig. 1C —10-year-4-month-old girl (patient 2 in
Table 1) with right hip and leg
pain, stiffness, and limp for 2–3 weeks. Coronal fast spin-echo
T2-weighted image (3,000/58) with fat suppression obtained at 3 T shows that
same abnormal focus depicted in A now appears with increased signal
intensity (long arrow). Minimal abnormal increased signal intensity
is seen in ipsilateral supraacetabular iliac bone (short arrow), just
superior to triradiate cartilage. Minimal abnormal increased signal intensity
is present within joint.
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Fig. 1D —10-year-4-month-old girl (patient 2 in
Table 1) with right hip and leg
pain, stiffness, and limp for 2–3 weeks. Coronal T1-weighted image
(800/6.9) with fat suppression after IV contrast administration. Geographic
abnormal signal in right proximal femoral epiphysis shows diffuse enhancement.
There is mild synovial hypertrophy (arrow), but very little
unenhanced joint fluid.
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Fig. 2A —9-year-8-month-old girl (patient 3 in
Table 1) with 10 days of right
hip pain and stiffness. Coronal T1-weighted image (TR/TE, 338/14) of pelvis
shows pelvic tilt and geographic area of abnormal signal intensity in right
proximal femoral epiphysis (arrow). Surrounding muscles are
considered normal.
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Fig. 2B —9-year-8-month-old girl (patient 3 in
Table 1) with 10 days of right
hip pain and stiffness. Coronal fast spin-echo T2-weighted image (3,820/76)
with fat suppression of pelvis shows geographic area of abnormal signal
intensity similar to that seen in A. Mild ill-defined abnormal signal
is seen in ilium and ischium centered about triradiate cartilage and within
joint space.
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Fig. 2C —9-year-8-month-old girl (patient 3 in
Table 1) with 10 days of right
hip pain and stiffness. Coronal contrast-enhanced T1-weighted image (422/14)
with fat suppression shows enhancement of abnormal focus in right proximal
femoral epiphysis, adjacent acetabulum, and synovium. Note tiny amount of
unenhanced joint fluid laterally (arrow).
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Fig. 3A —11-year-3-month-old girl (patient 1 in
Table 1) with bilateral hip
chondrolysis. Patient presented with left hip pain and stiffness of 3 weeks'
duration. Coronal T1-weighted image (TR/TE, 350/22) of pelvis shows geographic
focus of abnormal signal intensity in proximal left femoral epiphysis
(arrow). Muscle bulk is normal.
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Fig. 3B —11-year-3-month-old girl (patient 1 in
Table 1) with bilateral hip
chondrolysis. Patient presented 8 months after A with right hip pain.
Coronal T1-weighted image (450/14) of pelvis shows similar, but larger,
geographic focus of abnormal signal intensity centered in middle one third of
proximal right femoral epiphysis. Extensive bony irregularity of proximal left
femoral epiphysis has developed in interval.
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Fig. 3C —11-year-3-month-old girl (patient 1 in
Table 1) with bilateral hip
chondrolysis. Radiograph obtained when patient was 14 years 2 months shows
bilateral degenerative changes of both hips. Patient subsequently underwent
bilateral total hip replacements at age of 17 years.
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Fig. 4A —13-year-4-month-old boy (patient 6 in
Table 1) who presented after 6
weeks of right hip pain and stiffness. Coronal T2-weighted image (TR/TE,
3,500/96) with fat suppression of pelvis shows geographic area of increased
signal intensity extending from articular surface to physis in middle one
third of right proximal femur (arrow). Minimal increased signal
intensity is seen in medial acetabulum.
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Fig. 4B —13-year-4-month-old boy (patient 6 in
Table 1) who presented after 6
weeks of right hip pain and stiffness. Coronal T1-weighted image (300/8) with
fat suppression after administration of IV contrast material shows
predominantly peripheral enhancement of abnormal focus in proximal right
femoral epiphysis. Mild ipsilateral synovial enhancement also is seen.
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Conventional radiographs available in all children within 4 days of the MRI
examination showed a pelvic tilt toward the side of pain. Varying degrees of
osteoporosis and joint space narrowing of the affected hip were present.
All children were ultimately diagnosed with idiopathic chondrolysis.
Treatment for each patient included subtotal capsulectomy and muscle release,
when necessary, to relieve the joint contracture
[8]. Synovial biopsy at the
time of surgery showed hyperplastic synovium, chronic inflammation, and
fibrosis. In three children, follow-up conventional radiography ranging from 4
months to 2 years after the MRI examination showed normal hips. Moderate joint
space narrowing was seen in one child at 1-month follow-up and was more severe
in another child at 4 years 8 months after MRI. Patient 1 with bilateral hip
involvement developed severe loss of joint space (Fig.
3A,
3B,
3C) and subsequently underwent
bilateral total hip replacements at the age of 17 years.
Discussion
Idiopathic chondrolysis of the hip is an uncommon pediatric disorder
characterized by the ultimate loss of articular cartilage of the femoral head
and acetabulum. In this form of chondrolysis, the affected child has no
history of a slipped capital femoral epiphysis, infection, prolonged
immobilization, or other previously described dis order
[2]. Although classically
reported in African-American females in the second decade of life, this
disorder, as in our study group, is seen in both males and
non-African-Americans [6] and
often presents in preadolescents
[7].
The clinical presentation of patients with chondrolysis of the hip
typically is of an insidious onset of pain around the hip, progressive
stiffness, and limp [6]. The
range of motion of the affected hip is limited in all directions. There often
is progression rapidly to a flexion contracture of the hip, a lumbar lordosis,
and difficulty standing [9].
Involvement can be uni- or bilateral. Early diagnostic considerations include
septic ar thritis, toxic synovitis, pauciarticular juvenile idiopathic
arthritis, slipped capital femoral epiphysis, Legg-Calvé-Perthes dis
ease, pigmented villonodular synovitis, and posttraumatic arthritis
[10]. Most of these disorders
can be excluded on the basis of clinical presentation, physical examination
findings, conventional radiographic findings, and laboratory results. Juvenile
idiopathic arthritis often remains a consideration, and some authors suggest
that the two entities are one and the same and thus should be treated as such
[11].
The results of laboratory evaluation, including complete blood count and
WBC differential count, erythrocyte sedimentation rate, rheumatoid factor,
antinuclear antibody, and human leukocyte antigen-B27 surface antigen
[6], in patients with
idiopathic chondrolysis usually are normal. Histologic sampling of the
articular cartilage consistently reveals loss and thinning of the superficial
layer [12]. Synovial biopsy
shows chronic nonspecific inflammation with perivascular infiltrates of
lymphocytes, plas ma cells, and monocytes
[9,
13], but immunofluorescent
studies for immune complex deposition are normal. Synovial fluid is
unrevealing [9].
The cause of idiopathic chondrolysis of the hip remains elusive. Several
authors have proposed an immunologic cause for chondrolysis
[12,
14]. Mankin et al.
[15] suggested that
chondrolysis of the hip associated with a slipped epiphysis is an autoimmune
response to articular cartilage antigens instituted possibly by autolytic
degradation of cartilage. A self-perpetuating synovitis results in further
articular cartilage destruction.
Conventional radiographic hallmarks include a concentrically narrowed joint
space < 3 mm without the osteophyte formation typical of osteoarthritis,
accompanied by osteopenia
[13]. Other findings include
protrusio acetabuli, subchondral cysts, widening of the femoral head and neck,
and premature physeal fusion
[6]. Bone scinti graphy, as was
performed in two of our patients, shows normal bone uptake but shows diffuse
periarticular uptake suggestive of a diffuse inflammatory reaction
[16].
Johnson et al. [17]
reported the MRI findings of idiopathic chondrolysis of the hip in six girls
imaged within 9 months of symptom onset. Their findings included cartilage
loss in the affected hip joint, most severe centrally and on the femoral side;
bone remodeling; and widespread marrow edema of the femoral head, neck, and
acetabulum. They did not find synovial thickening, but they did see small
joint effusions. In addition, they reported marked muscle wasting in all
children, primarily of the gluteal and abductor muscles, likely reflecting the
functional joint disability
[17].
Our findings were dissimilar, likely reflecting the earlier time in the
disease process when imaging was performed. We uniformly observed a geometric
or polygonal focal marrow edema pattern centered in the middle one third of
the affected proximal femoral epiphysis on coronal images. This area of edema
extended from the physis to the articular surface in all hips and was
associated in most cases with ill-defined superomedial adjacent marrow edema
in the iliac and ischial bones. Why this pattern of marrow signal abnormality
is seen early in the disorder is unclear. One possibility is that this
geometric focus is a watershed-type vascular territory where the vascular
supply from the medial femoral circumflex artery and the posterior branch of
the obturator artery entering along the ligamentum teres meet. An insult to
blood flow or an anomaly of vasculature might first manifest in this area.
Chung [18] noted separate, but
an-astomotic, arterial supplies to the proximal femoral epiphysis. A
disruption or persistent separation of this vascular supply might explain the
segmental nature of the signal abnormality characteristic of early idio pathic
chondrolysis. A subsequent reactive inflammatory reaction in the hip joint can
result in synovial hypertrophy and adjacent marrow edema of the acetabulum. In
a study of children with juvenile idiopathic arthritis, investigators
[19] noted that synovial
hypertrophy and inflammation are accompanied by adjacent marrow edema in the
affected joints.
We did not see the more extensive marrow edema pattern in the femoral head,
neck, and acetabulum that has been described by Johnson et al.
[17] in any child. These
changes might occur later in the disease process as the reaction to the
initial insult becomes amplified. All children in our group showed mild to
moderate synovial enhancement and little to no joint fluid. This pattern was
seen after IV contrast administration. All surrounding muscles were considered
normal, again likely reflecting the shorter time course between symptom onset
and imaging. Mild cartilage loss was seen in most of the children, suggesting
that this finding is an early consequence of the disease process.
The differential diagnosis is often easily narrowed down on the basis of
clinical history, physical examination findings, laboratory results, and
radiologic findings. The geographic marrow abnormality of the femoral
epiphysis was central and focal unlike the diffuse homogeneous or
heterogeneous marrow abnormality characteristic of Legg-Calvé-Perthes
disease [20]. MRI findings of
toxic synovitis include contralateral (asymptomatic) joint effusions and
absent bone marrow signal abnormalities
[21]. Normal laboratory values
exclude a septic joint, and imaging usually can exclude a slipped capital
femoral epiphysis. The hallmark limited range of motion in all directions of
idiopathic chondrolysis is more extensive than the restriction of internal
rotation and abduction found in the hip of children with
Legg-Calvé-Perthes disease. The unusual focal marrow edema pattern in
the femoral epiphysis that we observed has not been described in juvenile
idiopathic arthritis.
Therapy for idiopathic chondrolysis remains controversial, and none has
been clearly effective [2].
Conservative treatment includes analgesics and antiinflammatory medications.
Load reduction of the hip with passive motion, intermittent traction, or
forced ankylosis in a functional position has also been used
[2,
4,
6,
22]. Surgical therapy, which
includes a subtotal capsulectomy with muscle release as needed to relieve
joint contracture, followed by aggressive non-weight-bearing range-of-motion
rehabilitation has been successful in a small cohort of patients
[8]. All patients in our group
underwent a subtotal capsulectomy, muscle release as needed, and aggressive
rehabilitation with varying results. To date, three patients in our study have
a normal or near-normal hip joint on radiography, two have moderate space
narrowing of the affected side, and one with bilateral chondrolysis underwent
total hip replacements.
In summary, a geometric region of abnormal signal intensity centered within
the proximal femoral epiphysis in a child with a painful, stiff hip
accompanied by ipsilateral ill-defined adjacent acetabular bone marrow edema,
mild synovial hypertrophy, and little or no joint fluid are characteristic
early MRI findings of idiopathic chondrolysis. In a child in whom the
diagnosis is considered but is uncertain, confirmation of the clinical
suspicion might help to direct therapy and potentially improve prognosis.
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Abstract
Introduction
