Fundamentals of Skeletal Radiology (Fundamentals of Radiology)

247 Pages·2013·107.061 MB·English

by  Clyde A. Helms MD

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FUNDAMENTALS
OF SKELETAL
RADIOLOGY
Fourth Edition
Clyde A. Helms, MD
Professor of Radiology and Orthopaedic Surgery
Department of Radiology
Duke University School of Medicine
Durham, North Carolina
1600 John F. Kennedy Blvd.
Ste 1800
Philadelphia, PA 19103-2899
FUNDAMENTALS OF SKELETAL RADIOLOGY, ISBN: 978-1-4557-5154-9
FOURTH EDITION
Copyright © 2014 by Saunders, an imprint of Elsevier Inc.
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broaden our understanding, changes in research methods, professional practices, or medical treatment
may become necessary.
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This book is dedicated to Jason, Benjamin, and Austin.
Like medical students and
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joy to teach.
v
Foreword to the Second Edition
Clyde Helms, as a radiologist in training during increasingly large number of young radiologists
the mid-1970s, was, in many ways, the ideal radi- (his residents and former residents) will attest that,
ology resident. Able, perceptive, informed, and indeed, they do work. The teaching may be un-
responsible, he progressed through the various orthodox, but the learning is real and substantial.
stages of residency training in superb fashion. On This volume is also unorthodox. Several excel-
the other hand, he was different. Whereas the lent, superbly researched and crafted treatises on
traditional “best resident” always had at hand ex- skeletal radiology are available to the radiology
haustive lists of differential diagnoses, Dr. Helms resident and practicing radiologist. This volume
quietly ignored the trivial, the esoteric, and the is not intended as an exhaustive compendium of
information that was not likely to serve him in his skeletal radiology. Rather it is, as indicated by the
work as a radiologist in the “real world,” some- title, an exposition of the basics of skeletal radiol-
times to the discomfiture of the radiology faculty ogy. In keeping with his personalized, unusual
of the University of California, San Francisco approach to teaching, he begins with a discussion
(of which I was then a junior member). Whereas of radiologic examinations that should not be per-
the traditional “best resident” was suitably in formed. The remainder of the book deals with
awe of the faculty (many of whom were truly skeletal conditions that radiologists are likely to
awesome), Dr. Helms fearlessly challenged what encounter any day of the week. The reader who
he perceived as unsupportable dogma. Not one to wishes to become familiar with Scheie syndrome
sit still for pretension, he poked gentle (and or trichorhinophalangeal dysplasia type II must
sometimes not so gentle) fun at the faculty. look elsewhere.
Occasional pranks were perpetrated, sometimes Rather than the usual, formal language found
at the expense of members of the faculty. No one in other radiology texts, the reader will encounter
was immune, no matter how lofty his status. the vernacular used by all radiologists when they
Dr. Helms, as the Sinatra song goes, did it his discuss their work with other radiologists. The
way. Irreverent, witty, occasionally outrageous, text is much like Dr. Helms himself—witty,
and a superb radiologist, he completed his irreverent, unpretentious, and fast-paced. The
residency and went on to fulfill his military reader will find the book refreshing, eminently
commitment. readable, and highly informative.
He returned to UCSF 3 years later as a faculty
member in the skeletal radiology section. That he The ideal condition
had not changed was immediately apparent. Would be, I admit, that men should be
Faculty meetings are disrupted by his irreverent
right by instinct;
remarks, frequently hilarious. Now a mentor, his
But since we are all likely to go astray,
teaching reflects the same realistic, nontraditional
The reasonable thing is to learn from
approach he used as a resident. He emphasizes not
those who can teach.
the exotic or esoteric but the practical, the infor-
mation that is critical in the day-to-day practice of —SOPHOCLES
radiology. Incorporated into his teaching method
are mnemonics, one or two of which might not Clyde Helms can teach!
be recommended for family viewing. On the
other hand, if they work, why not use them? An Hideyo Minagi, M.D.
vi
Preface
The fourth edition of this book, much like the it was irreverent and superficial, but now,
third, shows little substantial change from prior 25 years later, those criticisms wouldn’t bother
editions (how many ways can you say or illus- me. In fact, this book is irreverent and superfi-
trate that the damn bone is broken?); however, it cial! It’s meant to be. It’s not meant to be
has refinements and subtle corrections that make disrespectful to a profession that is worthy
it a more accurate reflection of my experience as of the highest respect – it’s merely a style of
a bone radiologist for the past nearly 35 years. teaching that makes learning easier for many of
The chapters on magnetic resonance imaging us. Once the basics of a subject are mastered,
(MRI) have been considerably updated to reflect one can delve more deeply into a topic. Other
the ongoing improvements in that area. books have been written to address that aspect
In keeping with the previous editions and of bone radiology. Use this book to get started
my basic personality, I have kept the style of and to have some fun while you learn. This
writing very informal and casual. When the book is purposely short and succinct, which is
first edition was written I was concerned that hard to accomplish with such a weighty topic.
my peers and mentors would have judged me To paraphrase Mark Twain, “I would have
to be too irreverent and superficial in dealing written a shorter book if I had more time.”
with a very serious and weighty subject. To my Enjoy it.
surprise the first edition was well received and
became quite popular. I’m sure many did think Clyde A. Helms
vii
C H A P T E R 1
Unnecessary Examinations
Before beginning to learn how to interpret There is virtually no finding on a skull series that
pathologic skeletal films, it is important to briefly will alter the next step in the patient’s workup.
consider unnecessary skeletal radiographic ex- Presence or absence of a fracture should not in-
aminations. Dr. Ferris Hall from Boston first fluence whether the patient receives a computed
brought to my attention the idea that just be- tomography (CT) scan or a magnetic resonance
cause we could x-ray something didn’t mean that imaging (MRI) examination. A CT or MRI scan
we should. His article titled “Overutilization of is obtained for other reasons: continued uncon-
Radiologic Examinations” in the August 1976 sciousness or focal neurologic signs. The plain
issue of Radiology1 details many examples of over- films only delay the eventual diagnosis, and in a
use and misuse of radiologic examinations. This patient with a subdural or an epidural hema-
article, even though it is more than 35 years old, toma, that delay could be fatal.3 The mortality
and a similar one by Dr. Herbert Abrams in the from intracranial bleeding is significantly in-
New England Journal of Medicine2 should be man- creased as the time to surgical decompression is
datory reading for every intern before he or she increased; therefore any delay caused by obtain-
begins to order examinations. ing unnecessary examinations (skull films) is
There are many reasons why it is undesir- potentially harmful. There are no findings on a
able to have unnecessary radiologic examina- plain skull series to indicate (or not indicate)
tions: excess cost, excess radiation, waste of the subdural or epidural hematoma (Figure 1-1).
patient’s time, waste of the technician’s and Fewer than 10% of patients with fractures have
radiologist’s time, and false hopes and expecta- subdural or epidural hematomas, and up to 60%
tions based on the outcome of the examination. of patients with subdural or epidural bleeding
In addition, and not least of all, they indicate a have no fractures.4 Therefore, why order the
breakdown in the logical thought pattern con- examinations? Medicolegal reasons? On the
cerning the patient’s workup. contrary! It is well documented that delays in
Many examinations are ordered because of diagnosis in this setting can be fatal, so ordering
so-called medicolegal considerations. It is be- unnecessary examinations might in fact be ask-
lieved that if a certain finding (e.g., a broken rib) ing for a lawsuit. The American College of Ra-
is not documented, the physician could be sued. diology has published appropriateness criteria
In fact, few, if any, examples of medicolegal for when to order particular examinations and
“covering yourself” types of examinations are has endorsed CT scans of the head as the initial
valid. With the move toward greater consumer study of choice in trauma.5
awareness, lawsuits in the future are more likely Despite much documentation in the radiology
to result from unnecessary radiation exposure and emergency department literature that show
because of needless examinations rather than skull films’ lack of utility in trauma, they still are
from too few examinations. commonly routinely ordered in many emergency
departments throughout North America. A sur-
vey performed in 1991 by Hackney and published
EXAMPLES OF UNNECESSARY
in Radiology6 reported that more than 50% of the
EXAMINATIONS hospitals in the study “often or always” obtained
skull films for trauma. Every hospital had CT
Skull Series available. What are they thinking? Obviously
they are not thinking about what a skull film will
Except for a depressed skull fracture or the pres- show them that might affect their treatment, be-
ence of intracranial metallic fragments, there is cause it won’t change a thing whether it is positive
no reason to order a skull series for trauma. This or negative.
was once one of the most abused examinations in
radiology, costing millions of dollars per year Sinus Series
unnecessarily. Although the number of unneces-
sary skull films has decreased, they remain a It is true that an opaque sinus or an air-fluid level
costly burden in many emergency departments. can be seen in a sinus series when sinusitis is
Copyright © 2014 Elsevier, Inc. All rights reserved. 1
2 1  Unnecessary Examinations
FIGURE 1-1 ​n Skull fracture. A thin radiolucent line char- FIGURE 1-2 n  Waters’ view of the sinuses. This film is
acteristic of a skull fracture is noted (arrow) extending
obtained with the patient’s head tilted slightly up-
obliquely across the temporal bone. A fracture in this
ward (as if he or she were drinking water—apologies
area is often associated with an epidural hematoma
to Dr. Waters). It is an excellent film to obtain when
because the middle meningeal artery lies here. This
the maxillary sinuses need to be seen. When done
finding by itself, however, has little or no significance
in an upright position, air-fluid levels can be seen
and must be correlated with clinical findings.
(arrow).
present. However, the patient with these find- CT scan to search for additional fractures might
ings is often asymptomatic, and just as often, the be in order, but not a nasal series.
sinus series is interpreted as normal in another
patient who has typical clinical findings of sinus- Rib Series
itis. Both of these patients are treated based on
their clinical, not radiographic, presentation, Fractured ribs are commonly seen in any radio-
which is appropriate. Therefore the information logic practice. The significance of the finding
from the sinus series is ignored. If that is the of a fractured rib or ribs is not well appreciated
way you practice—and many recommend that as by most physicians. If the truth be known, the
being proper—don’t order the sinus series: treat finding of a rib fracture after trauma has almost
the patient. Reserve the sinus series for the no clinical significance and does not alter treat-
patient who doesn’t respond to treatment or has ment. One must rule out a pneumothorax and
an unusual presentation. Also, if it is only sinus- even a lung contusion, both of which are uncom-
itis you are concerned with, most times a simple mon and are best done on chest films, not a rib
upright Waters’ view (Figure 1-2) to examine series. In older patients with chest wall pain
the maxillary and frontal sinuses, rather than a and rib fractures from undetermined causes, it
full sinus series, will suffice, saving money and is extremely difficult and often impossible to dif-
decreasing the patient’s exposure to radiation.7 ferentiate a pathologic rib fracture through a
metastatic focus from a posttraumatic rib frac-
Nasal Bone ture. Hence, obtaining x-ray films in a patient
with focal rib pain to find a fracture serves little
A nasal series is often requested to see if a patient purpose other than to find a cause for the pain.
has suffered a broken nose after trauma to the Most rib series can be eliminated without chang-
face. What if the nasal bone is fractured? It ing the way the patient is treated.
won’t be casted. It won’t be reduced. In other
words, no treatment will be given regardless of Coccyx
what the x-ray shows. Therefore don’t order the
films in the first place. Occasionally a nasal bone Although not a common x-ray examination, we
is badly enough displaced to warrant interven- have occasional requests to x-ray the coccyx
tion, but even then an acute, posttraumatic x-ray to rule out a fracture. As with the nasal bone
study adds nothing for the patient except ex- and ribs, a fracture in this location will not be
pense and radiation exposure. A facial series or a casted or reduced. Also, this examination has
Copyright © 2014 Elsevier, Inc. All rights reserved.
1  Unnecessary Examinations 3
significantly more gonadal radiation dose than renal osteodystrophy to look for Looser’s frac-
a rib or nasal series. Because no treatment is tures, brown tumors, and subperiosteal bone
predicated on the x-ray results, don’t order the resorption. Most institutions have replaced the
x-ray study for routine trauma to the coccyx. bone survey with hand films, which is preferable
in regard to patient expense and radiation dose.
Lumbar Spine Subperiosteal bone resorption is seen earliest
and easiest on the middle phalanges, radial sides
Plain films of the lumbar spine are probably the (Figure 1-3), and is virtually pathognomonic for
most abused examinations in radiology. They hyperparathyroidism. Looser’s fractures are rare
give the highest gonadal radiation dose of any and not treated. Brown tumors are uncommon
plain film examination, and in most cases they and also are not treated. Therefore, if no treat-
offer no diagnostic information that will be acted ment is based on the x-ray findings, the survey
on by the physician. A significant number of only satisfies curiosity and is not worth the pa-
lumbar spine films are done in persons younger tient’s money or radiation exposure.
than age 40 who have acute onset of back pain
after lifting or straining. There is virtually no Metastatic Bone Survey
plain film x-ray finding in this patient subgroup
that can be responsible for the acute problem or Little useful information is obtained from the
that can be treated with intervention. Even the majority of metastatic bone surveys. Occult le-
severest spondylolisthesis cannot unequivocally sions that are not found on radionuclide bone
be said to be the origin of the symptoms. Disc scans are seldom encountered. Radionuclide
herniation cannot be identified. Tumors and in- scans are more effective at picking up most
fections are not clinical considerations in this metastatic lesions and could be substituted for
setting. Treatment invariably consists of rest, bone surveys with less cost and better diagnostic
nonsteroidal antiinflammatory drugs (NSAIDs), yield.11 Many investigators believe that search-
overall relaxation of the muscle groups, and then ing for bone metastases is not warranted in every
flexion and extension exercises to strengthen the patient with a primary tumor unless finding
muscles. Radiographs have nothing to offer un- metastatic disease (mets) will obviate surgery or
less the pain is very atypical or the clinical picture otherwise change the patient’s therapy. Radionu-
is clouded by other considerations (e.g., intrave- clide bone scans with x-rays of questionable or
nous drug use, in which case infection must be clinically suspicious areas makes more sense than
ruled out). a complete metastatic bone survey. An exception
The gonadal radiation dose from a lumbar
spine film is the same as that from a daily chest
x-ray for 6,8 16,9 or 98 years,10 depending on
which study you choose to believe. These studies
were based on a three-view lumbosacral spine
series and do not include the oblique views rou-
tinely obtained in many practices. Subtle osseous
changes found on oblique views are thought by
many orthopedists to be insignificant in most
cases anyway.
When should a lumbosacral spine series be
ordered? In cases of severe trauma, possible pri-
mary or metastatic tumor, and possible infec-
tion. Acute low back pain with radicular signs is
no indication for a spine series. An MRI scan
will show disc herniation and would be the pre-
ferred examination over plain films if clinically
warranted. Generally a lumbar spine MRI ex-
amination is performed only after a failed course
of conservative therapy if disc disease is clinically
suspected.
Metabolic Bone Survey FIGURE 1-3 ​n Phalanges with subperiosteal bone resorp-
tion. Subperiosteal bone resorption is seen as a subtle
irregularity or interruption of the cortex. It is best seen
Many institutions routinely order metabolic bone
on the radial aspect of the middle phalanges (arrows)
surveys in patients with hyperparathyroidism or and is pathognomonic for hyperparathyroidism.
Copyright © 2014 Elsevier, Inc. All rights reserved.
4 1  Unnecessary Examinations
to this is in patients with multiple myeloma.
Radionuclide bone scans are often negative in
multiple myeloma, even with marked skeletal
involvement; hence a plain film bone survey is
warranted in these patients.
Ankle Series
The most common cause for presentation to
emergency departments in North America is an
ankle sprain, with more than 30,000 ankle sprains
reported each day.12 Ligamentous injuries can
easily be clinically differentiated from significant
fractures. One study reported that a 50% reduc-
tion of ankle films resulted in no fractures being
missed when the radiology resident simply exam-
ined the patients.13 Another study revealed that if
the patient were able to walk three steps immedi-
ately after the injury or during the examination
in the emergency room there was almost zero
chance of a fracture.14 This study was one of sev-
eral to use what has been called the Ottawa ankle
rules for when to obtain ankle x-ray films. They
are so named after the hometown of the first
authors to implement them and are in wide- FIGURE 1-4 n  Ankle after trauma. Calcific densities
spread use today in most emergency departments around the ankle that can be mistaken for avulsions
are often seen (arrow). When rounded and smoothly
in North America. Small bony avulsions receive
corticated, as in this example, they are either acces-
the same treatment as ligament tears and are
sory ossicles or old avulsions. An acute avulsion is
often difficult to differentiate from accessory best diagnosed clinically by noting point tenderness
ossicles (Figure 1-4). Therefore in most cases the at ligament insertion sites. Because a ligament can
x-ray film is not a factor in determining the avulse with or without a fragment of bone being
attached, the x-ray finding will not influence the
patient’s treatment and should be skipped.
patient’s treatment.
Lumbar Myelograms
One of the most painful radiologic examina- (Figure 1-6). We can hope that the myelogram
tions extant is the lumbar myelogram, in which will go the way of the pneumoencephalogram
a spinal needle is placed into the subarachnoid and the epidural venogram.
space of the lumbar spine and contrast material So far as choosing between a CT and an MRI
is injected (Figure 1-5). Although this is done scan of the lumbar spine for disc disease and spi-
for tumors, it is most commonly performed in nal stenosis, an MRI examination will give much
the workup of lumbar disc disease. Many studies more diagnostic information and is considered
show that a CT or MRI scan of the lumbar the state-of-the-art imaging examination for the
spine is more accurate than myelography in di- spine, although, as the next section shows, an
agnosing disc disease and emphasize that a CT MRI scan of the lumbar spine is one of the most
or MRI scan should be the study of choice. overused imaging tests in the country.
Many surgeons, however, still request myelo-
grams in addition to the CT or MRI study when MRI Lumbar Spine
only the CT or MRI need be performed. In ad-
dition to being painful, the myelogram pro- Much has been written in the lay press in the
duces side effects in some people that can be past few years concerning the overuse of medical
pronounced and debilitating; the myelogram testing at a time when our economy is reeling
occasionally necessitates overnight hospitaliza- from skyrocketing medical costs. One of the
tion; the radiation dose from the myelogram is imaging tests mentioned near the top of every
higher overall than with CT; and perhaps most list is an MRI study of the lumbar spine. Multi-
important, the myelogram is not as accurate and ple studies have shown that as many as one third
does not give as complete a picture of additional of asymptomatic individuals older than age 50
back structures as the CT or MRI examination will have one or more focal disc protrusions.15
Copyright © 2014 Elsevier, Inc. All rights reserved.