AJR 2005; 184:1486-1489
© American Roentgen Ray Society
MRI Appearance of Chondral Delamination Injuries of the Knee
Scott D. Kendell1,
Clyde A. Helms,
John W. Rampton,
William E. Garrett and
Laurence D. Higgins
1 All authors: Department of Radiology, Duke University, Box 3808, Durham, NC
27710.
Received June 16, 2004;
accepted after revision August 12, 2004.
Address correspondence to S. D. Kendell
(kende002{at}yahoo.com).
Abstract
OBJECTIVE. We describe the MRI appearance of five cases of chondral
delamination of the knee.
CONCLUSION. Chondral delamination injuries of the knee show
increased linear signal abnormality at the junction of the articular cartilage
and subchondral bone on T2-weighted (fast spin-echo) images of the knee.
Identifying and treating these lesions results in an improved prognosis for
patients with this injury.
Introduction
Chondral delamination is the separation of the articular cartilage from the
underlying subchondral bone at the tidemark
[1]. These injuries have been
reported as the result of shearing stress that is concentrated at the junction
of the noncalcified and calcified cartilage
[1–3].
The delamination line runs parallel to the joint surface, but the overlying
articular cartilage remains initially intact
(Fig. 1). Unrecognized and/or
untreated chondral delamination injuries of the knee have a poor prognosis
[1]. Identifying these lesions
preoperatively is important, as they alert the orthopedic surgeon that the
extent of cartilage injury and, therefore, the extent of débridement
necessary to treat the lesion is more significant than it may first appear
during routine arthroscopic inspection of the knee. To our knowledge, a
description of this injury has not been reported in the English-language
radiology literature. We describe the MRI appearance of five cases of chondral
delamination of the knee.
Materials and Methods
Two board-certified musculoskeletal radiologists retrospectively reviewed
the MR images of five surgically proven cases of chondral delamination of the
knee. T2-weighted (fast spin-echo, TR/TE, 2,000–2,500/60–80; field
of view, 14–16; 1.5 T) images with fat saturation in the sagittal,
coronal, and axial planes were used. Linear signal intensity near or equal to
that of joint fluid on T2-weighted images at the interface of the articular
cartilage and underlying subchondral bone was used to identify a chondral
delamination injury. The largest dimension of each injury was measured using
the MR images and compared with the largest surgically measured lesion length.
The subchondral bone and the overlying cartilage were examined for abnormal
signal. The location of each injury on the knee surface was recorded. The
menisci and primary ligaments of the knee were examined for associated
injuries.
The mean patient age was 26.4 years (range, 16–37 years). The
patients' ages in cases 1–5 were 23, 16, 37, 25, and 31 years,
respectively. Four of the patients were men (cases 1, 2, 4, and 5) and one
patient was a woman (case 3).
The mean time between the MRI examination and surgery was 35.8 days (range,
1–64 days). The time intervals in cases 1–5 were 64, 56, 20, 1,
and 38 days, respectively.
Results
All five of our cases showed linear signal abnormality near or equal to the
intensity of joint fluid at the junction of the articular cartilage and
subchondral bone on T2-weighted (fast spin-echo) MR images (Figs.
2,
3A,
3B,
4A,
4B,
4C,
5,
6). In each case, the areas of
signal abnormality corresponded to the location of delamination discovered
during arthroscopic débridement of the lesion. All patients presented
with knee pain referable to the lesion, and all patients' symptoms improved
after surgical treatment. Our results are summarized in
Table 1.
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Fig. 2. —Sagittal T2-weighted (fast spin-echo) image of knee in
23-year-old man with acute onset of medial knee pain after running injury
shows delamination of posterior aspect of medial femoral condyle measuring 2.5
cm with increased signal in subchondral bone and in articular cartilage
overlying injury.
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Fig. 3A. —16-year-old boy with patellar pain after twisting injury.
Axial T2-weighted (fast spin-echo) image of knee shows delamination of central
patella measuring 2 cm, with increased signal in subchondral bone and in
articular cartilage overlying lesion.
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Fig. 3B. —16-year-old boy with patellar pain after twisting injury.
Sagittal T2-weighted (fast spin-echo) image of knee shows delamination of
central patella with increased signal in subchondral bone and in articular
cartilage overlying lesion.
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Fig. 4A. —37-year-old woman with patellofemoral pain after twisting
injury. Axial T2-weighted (fast spin-echo) image of knee shows delamination of
medial femoral trochlea (arrow) measuring 1 cm. Note prominent medial
patellar plica.
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Fig. 4B. —37-year-old woman with patellofemoral pain after twisting
injury. Sagittal T2-weighted (fast spin-echo) image of knee shows delamination
of medial femoral trochlea (arrow) with increased signal in overlying
articular cartilage. Note prominent medial patellar plica.
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Fig. 4C. —37-year-old woman with patellofemoral pain after twisting
injury. Axial T2-weighted (fast spin-echo) image of knee shows grade 3
cartilage injury of patellar apex (arrow) across patellofemoral joint
from delamination injury. Note prominent medial patellar plica.
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Fig. 5. —25-year-old man with acute onset of medial knee pain after a
running injury. Sagittal T2-weighted (fast spin-echo) image of knee shows
grade 4 defect of medial femoral condyle (between small arrows). Just
posterior to full-thickness defect is short delamination injury (large
arrow) measuring 0.5 cm with increased signal in overlying articular
cartilage.
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Fig. 6. —31-year-old man with patellofemoral pain after a running
injury. Axial T2-weighted (fast spin-echo) image of knee shows grade 2–3
cartilage injury of medial femoral trochlea (small arrow), which
terminates in short delamination (large arrow) measuring 0.5 cm.
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Discussion
Cartilage injuries of the knee are thought to arise from chronic abrasive
wear resulting in superficial fibrillation of the cartilage or from acute
shear forces
[1–4].
The former mechanism of injury produces lesions that are usually asymptomatic
until the full thickness of the articular cartilage is eroded
[1]. The latter mechanism of
cartilage injury usually results in a painful lesion
[1]. Delamination injuries are
thought to be produced by the second mechanism of injury and involve a
separation of the uncalcified articular cartilage from the calcified cartilage
at the tidemark [1].
Identifying these injuries is important, as they have a poor prognosis when
unrecognized or untreated. The treatment for delamination consists of surgical
débridement to the subchondral bone
[1]. Depending of the size and
location, a cartilage restorative procedure can then be performed when
appropriate.
The incidence of chondral delamination injuries of the knee has not been
reported in the literature. A prospective study would be useful to answer this
question.
Several studies have addressed the ability of MRI to detect and classify
cartilage injuries
[5–8].
A description of chondral delamination injuries, however, has not appeared in
the English-language radiology literature to our knowledge.
Our results indicate that delamination lesions are observable on MRI. Our
cases showed excellent correlation between the size of the lesion identified
on MRI and the size of the lesion measured during surgery. An orthopedic study
in 1996, however, reported only a 21% sensitivity of MRI in detecting this
type of injury [1]. Whether the
poor sensitivity in that study related to lack of awareness of the diagnosis
on the part of the radiologists, inappropriate MRI techniques, or inherent
limitations of MRI to detect this lesion is unknown. Further work is necessary
to clarify this issue using modern MRI techniques and radiologists who are
trained to identify delamination injuries.
This study shows that delamination injuries can occur as an isolated
chondral injury or in association with a second cartilage injury such as our
cases 4 and 5, which showed Outerbridge
[9] grade 4 and grade 3
lesions, respectively, associated with the delamination injuries. Case 3
showed an isolated delamination injury of the medial femoral trochlea, but
there was an Outerbridge grade 3 injury of the adjacent patellar apex.
Chondral injuries have been reported in association with meniscal tears
[2]. None of the delamination
injuries in this study were associated with meniscal pathology.
One case in this study was associated with a transient patellar
dislocation, but there was not a consistent pattern of ligamentous injury with
the delamination lesions.
In conclusion, chondral delamination injuries of the knee show linear
T2-weighted signal near the intensity of joint fluid at the interface of the
articular cartilage and subchondral bone. Identifying and appropriately
treating these injuries result in an improved prognosis for patients with
chondral delamination.
Acknowledgments
We express our thanks to Lee Cothran for his illustration of a chondral
delamination injury.
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Abstract
Introduction
