DOI:10.2214/AJR.07.3590
AJR 2008; 191:490-498
© American Roentgen Ray Society
Medial Patellofemoral Ligament: Cadaveric Investigation of Anatomy with MRI, MR Arthrography, and Histologic Correlation
Berna Dirim1,2,
Parviz Haghighi3,
Debra Trudell1,
Gisele Portes1 and
Donald Resnick1
1 Department of Radiology (114), University of California, San Diego, Veterans
Affairs San Diego Healthcare System, San Diego, CA.
2 Present address: Izmir Ataturk Egitim ve Arastirma Hastanesi, Radyoloji
Servisi, Yesilyrt, Izmir, Turkey.
3 Department of Pathology, University of California, San Diego, Veterans Affairs
San Diego Healthcare System, San Diego, CA.
Received December 26, 2007;
accepted after revision February 20, 2008.
Address correspondence to B. Dirim
(bernadirim{at}gmail.com).
Abstract
OBJECTIVE. The purpose of this study was to use MRI with gross
anatomic and histologic correlation in cadavers to define the anatomic details
of the medial patellofemoral ligament.
MATERIALS AND METHODS. MRI of seven cadaveric knees was performed
before and after intraarticular administration of a gadolinium solution.
T1-weighted spin-echo MR images with and without fat suppression were acquired
in three planes. Correlation was made between findings derived from MRI and
cadaveric sections. Histologic analysis was performed on five specimens.
RESULTS. The bilaminar and trilaminar appearance of the medial
patellar ligamentous complex was defined on axial images. The medial
patellofemoral ligament and the medial patellotibial ligament were best
visualized on axial images. In three of five knees, the superficial fibers of
the medial patellofemoral ligament were attached to the epicondyle in a
position posterior to the attachment point of the tibial collateral ligament.
In all three knees, the deep fibers of the medial patellofemoral ligament
merged with and attached to the tibial collateral ligament. In two of these
five knees, all fibers of the medial patellofemoral ligament were attached to
the tibial collateral ligament. These findings were confirmed at histologic
examination.
CONCLUSION. The medial patellofemoral ligament can attach only to
the tibial collateral ligament or to both the tibial collateral ligament and
the femoral epicondyle. The bilaminar and trilaminar appearances of the medial
patellar ligamentous complex and the course of the medial patellofemoral,
medial patellomeniscal, and medial patellotibial ligaments were best defined
on axial images.
Keywords: medial patellofemoral ligament • medial patellomeniscal ligament • medial patellotibial ligament • MRI • trilaminar
Introduction
Patellofemoral joint instability is extremely common. Muscle activity,
articular factors, and passive soft-tissue restraint are important for
patellar stability [1,
2]. The medial and lateral
patellar ligamentous complexes (medial and lateral patellar retinacula) that
form the soft-tissue restraints provide patellofemoral joint stability
throughout the range of knee motion
[1]. The medial patellar
retinaculum represents condensations in tissue planes rather than discrete
structures that course obliquely and transversely from the patellar margin.
The medial patellofemoral ligament is the largest part of the medial patellar
ligamentous complex. Studies
[2–6]
have shown that the medial patellofemoral ligament provides most of the
restraining force to lateral displacement of the patella. The medial
patellotibial and medial patellomeniscal ligaments are the other important
parts of the medial patellar ligamentous complex of the patellofemoral
articulation.
Cadaveric studies have focused on the function of the medial patellofemoral
ligament and surgical techniques to repair it. Surgical treatment is commonly
recommended for recurrent patellar dislocation
[2,
4,
7]. Some of the recommended
operative procedures have addressed injury to the medial patellofemoral
ligament itself
[8–10].
Several studies have focused on the anatomic details of the medial
patellofemoral ligament [3,
4,
6,
11–14].
Although descriptions of the MRI characteristics of the injured medial
patellofemoral ligament related to patellar dislocation have appeared
[15–20],
these reports have not included anatomic details regarding the course and the
femoral and patellar attachments of the normal medial patellofemoral
ligament.
Our study was designed on the basis of observations in multiple clinical
cases in which a major MRI finding has been apparent detachment of the medial
patellofemoral ligament from the tibial collateral ligament (TCL) without
other evidence of recent patellar dislocation (Figs.
1A and
1B). This observation
stimulated us to investigate the anatomic details of the course and femoral
and patellar attachments of the medial patellofemoral ligament with MRI and to
perform anatomic and histologic correlation in cadavers. To our knowledge,
only one other study [13] has
been conducted with MRI and anatomic correlation of the normal anatomic
features of the medial and lateral patellar ligamentous complexes of cadaveric
knee specimens. Those investigators, however, did not specifically address the
anatomic features of the medial patellofemoral ligament. Definition of the
specific MRI characteristics of the normal medial patellofemoral ligament
should facilitate diagnosis of traumatic lesions of this ligament.
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Fig. 1A —40-year-old man with history of knee pain. Axial T1-weighted
spin-echo (TR/TE, 516/14) (A) and T2-weighted fat-suppressed (4,000/61)
(B) images show apparent detachment (thick arrows) of medial
patellofemoral ligament (thin arrows) without other evidence of
recent patellar dislocation.
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Fig. 1B —40-year-old man with history of knee pain. Axial T1-weighted
spin-echo (TR/TE, 516/14) (A) and T2-weighted fat-suppressed (4,000/61)
(B) images show apparent detachment (thick arrows) of medial
patellofemoral ligament (thin arrows) without other evidence of
recent patellar dislocation.
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Materials and Methods
Cadaver and Specimen Preparation
Seven fresh frozen anatomic specimens of knees (two left knees, five right
knees) were obtained from the cadavers of three women and four men (mean age
at death, 83.4 years; range, 74–93 years). The specimens were derived
from legs cut through the distal portion of the femur and proximal portion of
the tibia and fibula. Routine radiographs were obtained to ensure that the
knee joint was not affected by surgical alterations or the presence of gross
pathologic abnormalities such as fractures. The cadaveric specimens were
immediately frozen at –40°C (Bio-Freezer unit, Forma Scientific).
They were allowed to thaw for 24 hours at room temperature before MRI. The
knee specimens were obtained and used according to institutional guidelines,
and informed consent for research was obtained from relatives of the
deceased.
MRI and MR Arthrography
MR images were acquired with a 1.5-T superconducting unit (Signa, LX
Horizon, software version 8.3, GE Healthcare) with a 6.5-in (16.5 cm) standard
knee coil (Dia Coil, Medical Advances). All fresh frozen anatomic knee
specimens were imaged in a neutral supine position. Imaging was performed in
the coronal, axial, and sagittal planes. The MRI protocol consisted of
T1-weighted spin-echo sequences (TR/TE, 550/20–21). For acquisition of
high-spatial-resolution images, a section thickness of 2.5 mm, intersection
gap of 0.5 mm, field of view of 12 x 12 cm, and data acquisition matrix
of 512 x 256 pixels were used. T1-weighted spin-echo MR images in the
sagittal, coronal, and transverse planes were acquired without fat suppression
before intraarticular administration of a dilute gadolinium-containing
contrast agent. After contrast admini stration, T1-weighted spin-echo MR
images were acquired with and without fat suppression in the sagittal,
coronal, and transverse planes. To distend the joint and its recesses fully,
approximately 55–60 mL of a mixture of gadopentetate dimeglumine
(Magnevist, Bayer Schering Pharma) and saline solution (1:200 dilution) was
injected into the joint under manual pressure through an 18-gauge needle
inserted anterolaterally. MRI was begun within 5 minutes after the
injection.
MRI and Anatomic Correlation
After completion of the MRI examination, the cadaveric knee specimens were
again frozen at –40°C for more than 120 hours. The frozen knee
specimens were sectioned with a band saw (model B12, Butcher Boy) into
3-mm-thick slices in the axial (five knees), coronal (one knee), and sagittal
(one knee) planes corresponding closely to the MR images. After debris was
rinsed from the surface of the specimens, the sections were thawed, and each
slice was imaged with high-spatial-resolution radiography (Faxitron unit,
Hewlett Packard) and photographed under flood-lighting with a digital camera
(Coolpix 990, Nikon). To determine the anatomic details and attachment
patterns of the medial patellofemoral ligament, the findings on MR images of
each specimen were compared with the findings derived from visual inspection
of the anatomic slices.
For histopathologic analysis of the medial patellofemoral ligament, samples
of this ligament and the patellar and femoral attachment areas of the ligament
were collected from five knee specimens. These specimens were sectioned in the
axial plane because the course and both attachment sites of the medial
patellofemoral ligament were best observed in this plane. The samples were
suspended in a 10% formalin solution, embedded in paraffin, and sectioned into
slices 5 µm thick. Histologic slices were stained with H and E and analyzed
with light microscopy (magnification, x2 to x4) in consensus with
a musculoskeletal radiologist and an orthopedic pathologist with 30 years of
experience. The examiners recorded the characteristics of the medial
patellofemoral ligament.
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Fig. 2A —Cadaver of 74-year-old woman. Serial axial T1-weighted
spin-echo MR images (TR/TE, 550/20–21) from superior to inferior aspect
show attachment site of adductor magnus tendon (arrow, A)
immediately above attachment site of medial patellofemoral ligament (black
arrows, B and C) and tibial collateral ligament (open
arrow, B and C). Arrowheads in A and B
indicate synovium without distention of joint.
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Fig. 2B —Cadaver of 74-year-old woman. Serial axial T1-weighted
spin-echo MR images (TR/TE, 550/20–21) from superior to inferior aspect
show attachment site of adductor magnus tendon (arrow, A)
immediately above attachment site of medial patellofemoral ligament (black
arrows, B and C) and tibial collateral ligament (open
arrow, B and C). Arrowheads in A and B
indicate synovium without distention of joint.
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Fig. 2C —Cadaver of 74-year-old woman. Serial axial T1-weighted
spin-echo MR images (TR/TE, 550/20–21) from superior to inferior aspect
show attachment site of adductor magnus tendon (arrow, A)
immediately above attachment site of medial patellofemoral ligament (black
arrows, B and C) and tibial collateral ligament (open
arrow, B and C). Arrowheads in A and B
indicate synovium without distention of joint.
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Results
Table 1 summarizes the
descriptive statistics of the fresh frozen knee specimens. In all cases, the
medial patellofemoral ligament was visualized on T1-weighted images as a band
of low signal intensity extending from the medial margin of the superior half
of the patella to the posterior part of the medial femoral epicondyle. The
course and both the femoral and patellar attachment sites of the medial
patellofemoral ligament were best visualized on sequential axial images (Figs.
2A,
2B, and
2C). Coronal images were better
than sagittal images for visualizing the course and patellar attachment site
of the medial patellofemoral ligament. Differentiation of the femoral
attachment point of the medial patellofemoral ligament and the femoral
attachment point of the TCL was difficult on the coronal images. The medial
patellofemoral ligament, however, was seen at the level of the second anatomic
layer on the medial side of the knee in all cases (Figs.
3A,
3B,
3C,
3D,
3E,
3F,
3G,
3H,
4A,
4B,
4C,
4D, and
4E).
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Fig. 3A —Cadaver of 80-year-old-woman. Serial coronal T1-weighted
spin-echo MR images (TR/TE, 550/20–21) from anterior to posterior
(A–D) aspect and correlative anatomic photographs
(E–H) show medial patellofemoral ligament (solid black
arrows) as thin band of low signal intensity attaching in anterior aspect
to patella (P) and continuous under tendinous fibers (white arrows)
of vastus medialis obliquus (VMO) muscle. Differentiation of femoral
attachment point of medial patellofemoral ligament from femoral attachment
point of tibial collateral ligament (open black arrows) is not
clear.
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Fig. 3B —Cadaver of 80-year-old-woman. Serial coronal T1-weighted
spin-echo MR images (TR/TE, 550/20–21) from anterior to posterior
(A–D) aspect and correlative anatomic photographs
(E–H) show medial patellofemoral ligament (solid black
arrows) as thin band of low signal intensity attaching in anterior aspect
to patella (P) and continuous under tendinous fibers (white arrows)
of vastus medialis obliquus (VMO) muscle. Differentiation of femoral
attachment point of medial patellofemoral ligament from femoral attachment
point of tibial collateral ligament (open black arrows) is not
clear.
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Fig. 3C —Cadaver of 80-year-old-woman. Serial coronal T1-weighted
spin-echo MR images (TR/TE, 550/20–21) from anterior to posterior
(A–D) aspect and correlative anatomic photographs
(E–H) show medial patellofemoral ligament (solid black
arrows) as thin band of low signal intensity attaching in anterior aspect
to patella (P) and continuous under tendinous fibers (white arrows)
of vastus medialis obliquus (VMO) muscle. Differentiation of femoral
attachment point of medial patellofemoral ligament from femoral attachment
point of tibial collateral ligament (open black arrows) is not
clear.
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Fig. 3D —Cadaver of 80-year-old-woman. Serial coronal T1-weighted
spin-echo MR images (TR/TE, 550/20–21) from anterior to posterior
(A–D) aspect and correlative anatomic photographs
(E–H) show medial patellofemoral ligament (solid black
arrows) as thin band of low signal intensity attaching in anterior aspect
to patella (P) and continuous under tendinous fibers (white arrows)
of vastus medialis obliquus (VMO) muscle. Differentiation of femoral
attachment point of medial patellofemoral ligament from femoral attachment
point of tibial collateral ligament (open black arrows) is not
clear.
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Fig. 3E —Cadaver of 80-year-old-woman. Serial coronal T1-weighted
spin-echo MR images (TR/TE, 550/20–21) from anterior to posterior
(A–D) aspect and correlative anatomic photographs
(E–H) show medial patellofemoral ligament (solid black
arrows) as thin band of low signal intensity attaching in anterior aspect
to patella (P) and continuous under tendinous fibers (white arrows)
of vastus medialis obliquus (VMO) muscle. Differentiation of femoral
attachment point of medial patellofemoral ligament from femoral attachment
point of tibial collateral ligament (open black arrows) is not
clear.
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Fig. 3F —Cadaver of 80-year-old-woman. Serial coronal T1-weighted
spin-echo MR images (TR/TE, 550/20–21) from anterior to posterior
(A–D) aspect and correlative anatomic photographs
(E–H) show medial patellofemoral ligament (solid black
arrows) as thin band of low signal intensity attaching in anterior aspect
to patella (P) and continuous under tendinous fibers (white arrows)
of vastus medialis obliquus (VMO) muscle. Differentiation of femoral
attachment point of medial patellofemoral ligament from femoral attachment
point of tibial collateral ligament (open black arrows) is not
clear.
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Fig. 3G —Cadaver of 80-year-old-woman. Serial coronal T1-weighted
spin-echo MR images (TR/TE, 550/20–21) from anterior to posterior
(A–D) aspect and correlative anatomic photographs
(E–H) show medial patellofemoral ligament (solid black
arrows) as thin band of low signal intensity attaching in anterior aspect
to patella (P) and continuous under tendinous fibers (white arrows)
of vastus medialis obliquus (VMO) muscle. Differentiation of femoral
attachment point of medial patellofemoral ligament from femoral attachment
point of tibial collateral ligament (open black arrows) is not
clear.
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Fig. 3H —Cadaver of 80-year-old-woman. Serial coronal T1-weighted
spin-echo MR images (TR/TE, 550/20–21) from anterior to posterior
(A–D) aspect and correlative anatomic photographs
(E–H) show medial patellofemoral ligament (solid black
arrows) as thin band of low signal intensity attaching in anterior aspect
to patella (P) and continuous under tendinous fibers (white arrows)
of vastus medialis obliquus (VMO) muscle. Differentiation of femoral
attachment point of medial patellofemoral ligament from femoral attachment
point of tibial collateral ligament (open black arrows) is not
clear.
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Fig. 4A —Cadaver of 74-year-old woman. Serial axial T1-weighted
spin-echo MR images, (TR/TE, 550/20–21) (A and B) and
correlative anatomic photograph (C) show crural fascia (curved
arrows, B), outer tendinous fibers of vastus medialis obliquus
muscle (VMO) (arrowheads), and superior fibers of medial
patellofemoral ligament (straight arrows).
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Fig. 4B —Cadaver of 74-year-old woman. Serial axial T1-weighted
spin-echo MR images, (TR/TE, 550/20–21) (A and B) and
correlative anatomic photograph (C) show crural fascia (curved
arrows, B), outer tendinous fibers of vastus medialis obliquus
muscle (VMO) (arrowheads), and superior fibers of medial
patellofemoral ligament (straight arrows).
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Fig. 4C —Cadaver of 74-year-old woman. Serial axial T1-weighted
spin-echo MR images, (TR/TE, 550/20–21) (A and B) and
correlative anatomic photograph (C) show crural fascia (curved
arrows, B), outer tendinous fibers of vastus medialis obliquus
muscle (VMO) (arrowheads), and superior fibers of medial
patellofemoral ligament (straight arrows).
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Fig. 4D —Cadaver of 74-year-old woman. Photomicrograph of histologic
section shows fibers of medial patellofemoral ligament (white arrows)
intertwined and bridged (curved arrows) with fibers of vastus
medialis obliquus muscle (straight open arrows). (H and E,
x2)
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Fig. 4E —Cadaver of 74-year-old woman. Photomicrograph of histologic
section shows crural fascia (curved arrows), tendinous fibers of
vastus medialis obliquus muscle (arrowheads), and superior fibers of
medial patellofemoral ligament (straight arrows). (H and E,
x2)
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The vastus medialis obliquus (VMO) muscle was seen as a relatively small
set of muscle fibers located at the inferior aspect of the vastus medialis
muscle. The VMO muscle extended distally to insert in the superior and
superomedial aspects of the patella. The medial patellofemoral ligament was
partially covered by the VMO muscle and attached to the superior part of the
medial aspect of the patella. Some of the superior fibers of the medial
patellofemoral ligament intertwined with the fibers of the VMO muscle, and the
two were impossible to separate on MR images of all specimens. At histologic
examination, the medial patellofemoral ligament and the fibers of VMO muscle
also were anatomically intimate (Figs.
4A,
4B,
4C,
4D, and
4E). At the patellar
attachment site of the medial patellofemoral ligament, the parallel course of
the superior fibers of the medial patellofemoral ligament and the inferior
fibers of the VMO muscle led to a bilaminar appearance on axial MR images of
all knees (Figs. 5A,
5B,
5C,
5D, and
6). More posteriorly on the
medial side of the knee, the crural fascia coursed parallel to the outer
fibers of the VMO muscle and the superior fibers of the outer aspect of the
medial patellofemoral ligament. Because of this course, a trilaminar
appearance was seen on the medial side of the knee at the level of the
superior half of the patella (Figs.
4A,
4B,
4C,
4D,
4E and
6). The synovium of the
suprapatellar bursa and the patellofemoral joint was seen as a thick band of
low signal intensity in the inner portion of the anterior part of the medial
patellofemoral ligament on standard MR images without distention of the joint
(Figs. 2A,
2B, and
2C). When the joint was
distended after MR arthrography, this synovial lining and the medial
patellofemoral ligament were found to course closely together (Figs.
7A,
7B,
7C,
7D,
7E, and
7F).
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Fig. 6 —Diagram shows normal anatomic details of medial
patellofemoral ligamentous complex seen on serial axial MR images. VMO =
vastus medialis obliquus muscle, QT = quadriceps tendon, PT = patellar tendon.
Single straight arrow indicates inferior fibers of VMO; open arrow (B),
medial patellofemoral ligament; double arrows (C), crural fascia; open
arrow (D), tibial collateral ligament; arrowhead (E), medial
patellomeniscal ligament; curved arrow (E), medial patellotibial
ligament.
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Fig. 7A —Cadaver of 79-year-old man. Axial T1-weighted spin-echo MR
arthrographic image (TR/TE, 550/20–21) (A), anatomic photograph
(B), and photomicrograph of histologic section (H and E, x2)
(C) show fibers of medial patellofemoral ligament (black
arrows) merging with tibial collateral ligament (white straight
arrows). Open arrow (C) indicates attachment between medial
patellofemoral ligament and tibial collateral ligament. Arrowhead indicates
joint capsule; curved arrow (A and B), crural fascia. B =
bone.
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Fig. 7B —Cadaver of 79-year-old man. Axial T1-weighted spin-echo MR
arthrographic image (TR/TE, 550/20–21) (A), anatomic photograph
(B), and photomicrograph of histologic section (H and E, x2)
(C) show fibers of medial patellofemoral ligament (black
arrows) merging with tibial collateral ligament (white straight
arrows). Open arrow (C) indicates attachment between medial
patellofemoral ligament and tibial collateral ligament. Arrowhead indicates
joint capsule; curved arrow (A and B), crural fascia. B =
bone.
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Fig. 7C —Cadaver of 79-year-old man. Axial T1-weighted spin-echo MR
arthrographic image (TR/TE, 550/20–21) (A), anatomic photograph
(B), and photomicrograph of histologic section (H and E, x2)
(C) show fibers of medial patellofemoral ligament (black
arrows) merging with tibial collateral ligament (white straight
arrows). Open arrow (C) indicates attachment between medial
patellofemoral ligament and tibial collateral ligament. Arrowhead indicates
joint capsule; curved arrow (A and B), crural fascia. B =
bone.
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Fig. 7D —Cadaver of 79-year-old man. Axial T1-weighted spin-echo MR
arthrographic image (550/20–21) (D), anatomic photograph
(E), and photomicrograph of histologic section (H and E, x4)
(F) immediately below A–C show inner fibers of medial
patellofemoral ligament (arrowheads, F) merging with tibial
collateral ligament (straight arrows) and outer fibers of medial
patellofemoral ligament (curved arrows) wrapping over tibial
collateral ligament and coursing posteriorly. B = bone.
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Fig. 7E —Cadaver of 79-year-old man. Axial T1-weighted spin-echo MR
arthrographic image (550/20–21) (D), anatomic photograph
(E), and photomicrograph of histologic section (H and E, x4)
(F) immediately below A–C show inner fibers of medial
patellofemoral ligament (arrowheads, F) merging with tibial
collateral ligament (straight arrows) and outer fibers of medial
patellofemoral ligament (curved arrows) wrapping over tibial
collateral ligament and coursing posteriorly. B = bone.
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Fig. 7F —Cadaver of 79-year-old man. Axial T1-weighted spin-echo MR
arthrographic image (550/20–21) (D), anatomic photograph
(E), and photomicrograph of histologic section (H and E, x4)
(F) immediately below A–C show inner fibers of medial
patellofemoral ligament (arrowheads, F) merging with tibial
collateral ligament (straight arrows) and outer fibers of medial
patellofemoral ligament (curved arrows) wrapping over tibial
collateral ligament and coursing posteriorly. B = bone.
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The femoral attachment of the medial patellofemoral ligament was well
visualized in the anatomic sections of only five of the specimens sectioned in
the axial plane. The femoral attachment of the medial patellofemoral ligament
was at the posterior part of the medial epicondyle in those knees. The
posterior fibers of the medial patellofemoral ligament, TCL, and adductor
magnus tendon all converged toward the same region of the femur. The medial
patellofemoral ligament attached to the epicondyle just below the attachment
site of the adductor magnus tendon in all knees (Figs.
2A,
2B, and
2C). In three of these five
knees, the superficial fibers of the medial patellofemoral ligament were
wrapped over the femoral attachment of the TCL, which itself attached to the
epicondyle in a position posterior to the attachment point of the TCL. In all
three knees, the deep fibers of the medial patellofemoral ligament merged with
and attached to the TCL (Figs.
7A,
7B,
7C,
7D,
7E, and
7F). In two of these five
knees, all fibers of the medial patellofemoral ligament were attached to the
TCL. These findings were confirmed at histologic examination (Figs.
8A,
8B, and
8C).
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Fig. 8A —Cadaver of 93-year-old man. Axial T1-weighted spin-echo MR
arthrographic image (TR/TE, 550/20–21) (A), anatomic photograph
(B), and photomicrograph of histologic section (H and E, x4)
(C) show all fibers of medial patellofemoral ligament (open
arrows) merging with tibial collateral ligament (solid arrows).
Curved arrow (A and B) indicates crural fascia.
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Fig. 8B —Cadaver of 93-year-old man. Axial T1-weighted spin-echo MR
arthrographic image (TR/TE, 550/20–21) (A), anatomic photograph
(B), and photomicrograph of histologic section (H and E, x4)
(C) show all fibers of medial patellofemoral ligament (open
arrows) merging with tibial collateral ligament (solid arrows).
Curved arrow (A and B) indicates crural fascia.
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Fig. 8C —Cadaver of 93-year-old man. Axial T1-weighted spin-echo MR
arthrographic image (TR/TE, 550/20–21) (A), anatomic photograph
(B), and photomicrograph of histologic section (H and E, x4)
(C) show all fibers of medial patellofemoral ligament (open
arrows) merging with tibial collateral ligament (solid arrows).
Curved arrow (A and B) indicates crural fascia.
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The medial patellomeniscal ligament extended from the medial margin of the
inferi- or pole of the patella obliquely and inferiorly and attached to the
anterior horn of the medial meniscus and coronary ligament on MR images of all
specimens. The course of this ligament was well observed in the axial and
sagittal planes (Figs. 6,
9A,
9B, and
9C).
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Fig. 9A —Cadaver of 85-year-old man. Serial axial T1-weighted
spin-echo MR arthrographic images (TR/TE, 550/20–21) show medial
patellomeniscal ligament (curved arrows, A and B),
medial patellotibial ligament (open arrows), and tibial collateral
ligament (solid arrows, A and B). M = anterior horn of
medial meniscus, T = tibia.
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Fig. 9B —Cadaver of 85-year-old man. Serial axial T1-weighted
spin-echo MR arthrographic images (TR/TE, 550/20–21) show medial
patellomeniscal ligament (curved arrows, A and B),
medial patellotibial ligament (open arrows), and tibial collateral
ligament (solid arrows, A and B). M = anterior horn of
medial meniscus, T = tibia.
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Fig. 9C —Cadaver of 85-year-old man. Serial axial T1-weighted
spin-echo MR arthrographic images (TR/TE, 550/20–21) show medial
patellomeniscal ligament (curved arrows, A and B),
medial patellotibial ligament (open arrows), and tibial collateral
ligament (solid arrows, A and B). M = anterior horn of
medial meniscus, T = tibia.
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The medial patellotibial ligament was attached to the medial aspect of the
tibia immediately below the joint line. Some fibers of the medial
patellotibial ligament merged with the TCL at this level. In the inferior
aspect this ligament attached to the medial surface of the patella and coursed
obliquely upward. Specifically, it attached to the lower part of the patella
and proximal part of the patellar tendon. The course, tibial attachment site,
and patellar attachment site of the medial patellotibial ligament were best
visualized immediately below the joint line on axial images (Figs.
6,
9A,
9B, and
9C).
Discussion
Dislocation of the patella often results in disruption of the medial
patellofemoral ligament [7,
21]. Dislocation is thought to
recur in 20–44% of conservatively treated patients
[14,
22–24].
In reports of several studies
[2,
4,
7], surgical treatment has been
recommended for recurrent patellar dislocation. The importance of the medial
patellofemoral ligament in preventing patellar dislocation has been
established in several studies
[3,
5–7,
9]. MRI may have an important
role in directing surgical management if the precise site and extent of injury
to the medial patellofemoral ligament are depicted. Although a few
descriptions of the MRI characteristics of the medial patellar ligamentous
complex in cases of patellar dislocation have appeared in the literature, the
anatomic details of the medial patellofemoral ligament on MR images have been
largely ignored
[15–20].
To our knowledge, only one study
[13] has resulted in a
detailed description of the MRI appearance of the ligament.
Three anatomic layers on the medial side of the knee were described by
Warren and Marshall [11]. The
superficial, or first, layer invests the crural fascia; the middle, or second,
layer includes the TCL and various structures posterior to this ligament,
including those located in the posteromedial corner of the knee; the deepest,
or third, layer includes the deep portion of the medial collateral ligament
complex and joint capsule. The medial patellofemoral ligament lies within the
second layer as observed in all of our knee specimens
[11,
12].
In our investigation, the anatomic details of the medial patellofemoral
ligament and its relation to the other medial patellar supporting ligaments
were best seen on axial MR images, findings similar to those made by Starok et
al. [13] and Sanders et al.
[16]. The coronal plane was
better than the sagittal plane for visualizing the course of the medial
patellofemoral ligament. The patellar attachment of the medial patellofemoral
ligament was wider than the femoral attachment of this ligament in all knees.
The medial patellofemoral ligament was partially covered by the VMO muscle,
and some superior fibers of the medial patellofemoral ligament were
intertwined with the fibers of the VMO muscle close to its patellar insertion,
as depicted on MR images and at visual inspection of the anatomic sections.
Panagiotopoulos et al. [6]
confirmed these findings using dissections of knee specimens. However, that
study did not include histologic correlation of the findings. We visualized a
very close course of and even contact between the superior fibers of the
medial patellofemoral ligament and the inner fibers of the VMO muscle.
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Fig. 5A —Cadaver of 88-year-old man. Serial axial T1-weighted
spin-echo MR images (TR/TE, 550/20–21) (A–C) and anatomic
photograph (D) show parallel course of superior part of medial
patellofemoral ligament (white arrow) and inferior fibers of vastus
medialis obliquus (VMO) muscle and tendon (black arrows).
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Fig. 5B —Cadaver of 88-year-old man. Serial axial T1-weighted
spin-echo MR images (TR/TE, 550/20–21) (A–C) and anatomic
photograph (D) show parallel course of superior part of medial
patellofemoral ligament (white arrow) and inferior fibers of vastus
medialis obliquus (VMO) muscle and tendon (black arrows).
|
|
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Fig. 5C —Cadaver of 88-year-old man. Serial axial T1-weighted
spin-echo MR images (TR/TE, 550/20–21) (A–C) and anatomic
photograph (D) show parallel course of superior part of medial
patellofemoral ligament (white arrow) and inferior fibers of vastus
medialis obliquus (VMO) muscle and tendon (black arrows).
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Fig. 5D —Cadaver of 88-year-old man. Serial axial T1-weighted
spin-echo MR images (TR/TE, 550/20–21) (A–C) and anatomic
photograph (D) show parallel course of superior part of medial
patellofemoral ligament (white arrow) and inferior fibers of vastus
medialis obliquus (VMO) muscle and tendon (black arrows).
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At the patellar attachment site of the medial patellofemoral ligament, the
parallel course of the outer fibers of the medial patellofemoral ligament and
the inner fibers of the VMO muscle led to a bilaminar appearance on axial MR
images. At the level of the patella, a bilaminar appearance of the medial
ligamentous structures on MR images was described in a previous radiologic
study [13]. Unfortunately,
this appearance was attributed to the parallel course of the superficial
retinaculum and the medial patellofemoral ligament. In the knees in our study,
the bilaminar appearance of the medial ligamentous complex was related to the
parallel course of the fibers of the VMO muscle and medial patellofemoral
ligament.
The crural fascia (superficial layer) was observed as a distinct band from
the fibers of the VMO muscle, which led to a trilaminar appearance on the
medial side of the knee on axial images in all of the knees in our study. To
the best of our knowledge, this trilaminar appearance has not been described
previously. We observed the bilaminar and trilaminar configurations of the
medial patellar ligamentous complex with a larger field of view and reduced
matrix on T1-weighted axial images in most of the routine knee MR examinations
in clinical cases. Although fat-saturated or non-fat-saturated T2-weighted
axial images are more commonly used for routine MRI of the knee to describe
the pathologic signal intensity of the patellar ligaments, our results suggest
that addition of T1-weighted axial images to MRI examinations of possibly
injured patellar supporting ligaments may lead to better investigation of
these ligaments. When the joint was distended for MR arthrography, the
synovium of the suprapatellar bursa was seen on axial images as a band of low
signal intensity coursing close and parallel to the medial patellofemoral
ligament.
The femoral attachment of the medial patellofemoral ligament was not well
visualized in coronal and sagittal anatomic sections. This attachment was well
seen in five specimens sectioned in the axial plane. The femoral attachment of
the medial patellofemoral ligament was at the posterior part of the medial
epicondyle immediately below the attachment site of the adductor magnus tendon
in all five knees sectioned in the axial plane. The medial patellofemoral
ligament, TCL, and adductor magnus tendon all converged toward the same
location.
The anatomic details of the femoral attachment of the medial patellofemoral
ligament remain controversial. Conlan et al.
[3] and Tuxoe et al.
[25], who performed cadaveric
studies, described the attachment as occurring at the adductor tubercle in
common with the attachment sites of the TCL and adductor magnus tendon. Feller
et al. [12] reported the
femoral attachment to be just anterior to the epicondyle, a finding not made
in any of the knees in our study. Nomura et al.
[9] reported that some of the
deep fibers of the medial patellofemoral ligament attached at a position
anterior to the proximal attachment of the TCL in the epicondyle. Other
superficial fibers of the medial patellofemoral ligament were found to wrap
over the epicondyle, passing in a position immediately distal to the adductor
tubercle to attach in a position immediately posterior to the epicondyle.
Desio et al. [5] and Amis et
al. [2] reported that the
femoral attachment was spread by decussating fibers that attached to both the
adductor tubercle and the TCL and had a more direct attachment to the
epicondyle.
In all of the aforementioned studies, cadaveric specimens were dissected to
delineate the anatomic details. None of the studies included MRI and
histologic correlation. In our study, the superficial fibers of the medial
patellofemoral ligament were wrapped over the femoral attachment of the TCL,
which itself attached to the epicondyle at the posterior attachment of the MCL
in three of five knees. In those three knees, the deep fibers of the medial
patellofemoral ligament merged with the TCL. This observation is identical to
those of Desio et al. [5] and
Amis et al. [2]. We believe the
superficial fibers of the medial patellofemoral ligament, which may wrap over
the femoral attachment of the TCL, cause a detachment-like appearance at the
femoral attachment of the normal medial patellofemoral ligament in MRI
examinations in clinical cases. In two of five knees, all fibers of the medial
patellofemoral ligament were attached to the TCL. This pattern of femoral
attachment of the medial patellofemoral ligament was reported by Tuxoe et al.
[25] and Conlan et al.
[3].
The medial patellomeniscal ligament was found to course from the medial
margin of the patella to the anterior horn of the medial meniscus and coronary
ligament on sagittal images of all of the knees in our study. On axial images,
this ligament was located deep in relation to the inferior part of the medial
patellofemoral ligament and superior part of the medial patellotibial
ligament. The medial patellotibial ligament extended from the medial margin of
the tibia to the inferior aspect of the patella and proximal part of the
patellar tendon in all of the knees. The course and both attachment sites of
the medial patellotibial ligament were best visualized immediately below the
level of the joint on axial images.
One of the limitations of our study was the small number of cadaveric
specimens. Thus it was difficult to extrapolate these results to an entire
population. Although only seven knees were studied, we believe the findings
are significant because we correlated our findings with findings at histologic
analysis of the specimens and because results of anatomic studies
[11,
13] with larger numbers of
specimens have consistently defined the anatomic features of the medial
patellofemoral ligament with minor variations. The other limitations of our
investigation were the absence of clinical history and the advanced age at
death (mean, 83.4 years) of the persons from whom the specimens were acquired,
which may have increased the incidence of degenerative changes.
Despite the limitations, the main aim of this study was achieved, which was
to use MRI to show the anatomic details of the medial patellofemoral ligament.
The bilaminar and trilaminar appearance of the medial patellar supporting
ligamentous complex and the medial patellofemoral ligament was best visualized
on axial images. The medial patellotibial ligament also was best visualized on
axial images. The medial patellomeniscal ligament was well visualized on axial
and sagittal images.
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Abstract
Introduction
