Introduction to limb imaging 1. Download the presentation for best effect (animations don't function properly online).

1. Introduction to Limb
Imaging 1
RAH Radiology

2. Topics for today
Overview:
– Film quality
– Anatomy
– Fractures
Case examples/quiz
Warnings:
This is a big topic. Important phrases and
concepts are bolded.
Many of these topics have been
simplified. The intent is to deliver useful
basic skills, which can be later refined.

3. Topics for next session
Overview:
– Other modalities
– Soft tissues
– Osteoarthritis
– Bone tumours?
Case examples/quiz

4. Overview:
– Film quality
– Anatomy
– Fractures
This is a frontal x-ray of the left
upper arm.
While there are standard techniques
(the humerus is imaged antero-
posterior by convention),
magnification is not an issue,
because the whole limb is so close to
the detector. The x-ray beam barely
diverges at all.

5. Overview:
– Film quality
– Anatomy
– Fractures
Instead, most limb x-ray quality
issues relate to positioning.
Musculoskeletal injuries limit
movement, so many positions are
hard to achieve.
Most limb x-rays are taken in the
neutral or anatomic position. In the
example here, the arm is abducted,
which may limit assessement at the
shoulder joint.

6. Overview:
– Film quality
– Anatomy
– Fractures
This is often worse in children.
Achieving diagnostic views in young
children with fractures can be very
difficult, and often traumatic.
In this example the elbow is almost
lateral in orientation, but the wrist
appears like a frontal view. Many
subtle features can be missed.

7. Overview:
– Film quality
– Anatomy
– Fractures
The general rule of thumb is that
every study of a limb or joint should
have two orthogonal (at right
angles) views.
This usually means a frontal and
lateral view.
Oblique views reveal anatomy that is
obscured by other structures. For
example, the radial head view lifts
the radius from behind the ulna.

8. Overview:
– Film quality
– Anatomy
– Fractures
The anatomy of the long bones is
fairly simple.
Every long bone has the same
features, although they are
confusingly called different things.
The major “parts” are all defined in
relation to the developmental
anatomy.

9. Overview:
– Film quality
– Anatomy
– Fractures
Each part of a bone develops from an
ossification centre. Non-calcified
matrix is formed first, and this later
calcifies.
These growth centres are usually:
• Shaft (in utero)
• Proximal and distal, articular
and ligament attachments
In this wrist there is partial
ossification of the distal radius, and
no ossification of the distal ulna.

10. Overview:
– Film quality
– Anatomy
– Fractures
There are several different methods
to describe the long bones. The
easiest way is to identify the shaft
and the proximal and distal “ends”.
The shaft is the roughly parallel
portion of the bone, before it flares
at either end.
The shaft is easiest to describe by
splitting it into proximal, middle and
distal thirds.

11. Overview:
– Film quality
– Anatomy
– Fractures
The “ends” of the bones are a but
trickier because they have specific
names in different bones.
The flaring portion is called the
metaphysis, although most doctors
are happy for you to include this in
the shaft if that is hard to remember.
The most important part of the end
of a long bone is the articular
surface.

12. Overview:
– Film quality
– Anatomy
– Fractures
The articular surfaces are covered in
cartilage, which protects the joint.
The adjacent bone can always be
described as sub-articular.
Otherwise, the various ends of bones
have a range of names, and most of
the associated bony lumps have
names too, so there isn’t an easy way
to learn these details.
Examples are labelled to the left.
Femoral condyles
Tibial plateau
Fibular head

13. Overview:
– Film quality
– Anatomy
– Fractures
A good rule of thumb:
If it is a single rounded bulge, call it
the head.
If it has multiple bulges … rote
learning is the only way. Use Google
as needed.
Humeral head
Radial head
Humeral condyles
Olecranon

14. Overview:
– Film quality
– Anatomy
– Fractures
The other bones are also a bit more
complex, and have named parts.
In the hands and feet:
• The carpals and tarsals are all
uniquely named (for
example, the “lunate”).
• The metacarpals / tarsals and
phalanges are small “long
bones”, with a base
(proximal), a shaft, and a
head (distal).

15. Overview:
– Film quality
– Anatomy
– Fractures
The flat bones are quite difficult to
assess, because they have many
overlapping parts.
The pelvis can be divided into broad
regions:
• Iliac wing
• Acetabular
• Pubic rami
• Sacrum

16. Overview:
– Film quality
– Anatomy
– Fractures
The scapula can be divided into
broad regions:
• Scapula spine
• Supraspinus
• Scapula body / infraspinus
• Glenoid
Not shown: coracoid process and
acromion.

17. Overview:
– Film quality
– Anatomy
– Fractures
The neck of femur is a common site
of fracture of the elderly, as injuries
here have poor outcomes without
surgical management.
There are multiple named regions,
but the important distinction in
trauma is whether the fracture is
within the joint capsule. The head
and proximal neck of femur are intra-
capsular. The distal neck and
trochanteric region are not.

18. Overview:
– Film quality
– Anatomy
– Fractures
The blood supply to the head of the
femur is mostly via capsular vessels.
These can be disrupted by trauma,
leading to avascular necrosis (AVN).
This case shows early AVN after an
inadequately treated subcapital
fracture. The femoral head is
deformed and sclerotic.
Case contributed by Dr Chris O’Donnell at Radiopaedia.org

19. Overview:
– Film quality
– Anatomy
– Fractures
The most common reason to perform
limb imaging is to look for fractures.
Dislocations are less common and
are usually more clinically apparent,
so the imaging is more for prognosis
than diagnosis; looking for associated
fractures.

20. Overview:
– Film quality
– Anatomy
– Fractures
• Identifying fractures
• Displaced fractures can be seen
with a cortical step. Jagged or
angular lines are rarely seen
anatomically.
• Fracture “lines”, seen as linear low
densities crossing the bone are
untrustworthy. Our brains
misinterpret them. Note the black
lines over the pelvis on this study,
which are not fractures.

21. Overview:
– Film quality
– Anatomy
– Fractures
• Identifying fractures
• Undisplaced fractures are difficult
to appreciate, even for
radiologists. The most useful sign
will always be a tiny bit of cortical
displacement.
• Associated features like joint
effusions and soft tissue swelling
can help. There is an elbow joint
effusion in this study, consistent
with an occult fracture.

22. Overview:
– Film quality
– Anatomy
– Fractures
• Identifying fractures
• Repeat imaging in two weeks
usually reveals an occult fracture
as the edges of the fracture
becomes denser while healing.
• This is usually performed if there
is no risk to delaying diagnosis.
• If the diagnosis cannot wait, CT,
MRI or bone scan imaging is
performed.

23. Overview:
– Film quality
– Anatomy
– Fractures
• Describing fractures
The major treatment decision for
fractures is whether they can be
managed conservatively, or if they
have to be fixed with an operation.
This decision is about the predicted
long-term function of the limb.
There are many ways to describe
fractures, but only some of the are
relevant to this decision.

24. Overview:
– Film quality
– Anatomy
– Fractures
“Important” features:
• Degree of displacement
• Location of fracture
• Comminution / fragmentation
• Open / compound injury
“Less important” features:
• Direction of displacement
• Tilt
• Location of fracture
• Fracture orientation

25. “Important” features:
• Degree of displacement
A significantly displaced fracture will
not heal well (or at all if the fracture
margins don’t touch). Such a fracture
may require internal fixation if
reduction cannot be achieved
otherwise.
The most universal way to describe
displacement is by reference to the
bone itself.
“There is half a bone width of
displacement”.

26. “Less important” features:
• Direction of displacement
The direction of displacement may
suggest something about the
mechanism of injury. For example,
posterior displacement in a distal
radius fracture usually suggests a “fall
onto an outstretched hand” (FOOSH).
That said, the direction of displacement
will almost never alter management.
If you want to mention it, displacement
is always described in reference to the
distal fragment.
“There is medial displacement by
around half a bone width”.

27. “Less important” features:
• Tilt
The angulation or tilt through the
fracture is rarely important.
Most radiologists don’t mention the
degree or direction of tilt unless it is
clearly non-anatomic, in which case the
degree of displacement is a better
feature for prognosis.
If you want to mention it, tilt is
described in reference to the distal
portion of the distal fragment.
“There is mild medial tilt without
displacement.”

28. “Important / less important” features:
• Location of fracture
The part of the bone involved almost
never decides management.
There are several exceptions, however.
• Intra-articular - Disruption of
the cartilage results in severe
degeneration at the joint.
• Growth plate - In a child with
unfused growth plates,
unrepaired damage here will
impair future growth (or even
halt it completely).
• Blood supply - Some fractures
can impair blood supply to the
bone, leading to AVN.

29. “Important” features:
• Comminution / fragmentation
Fractures with multiple fragments
often heal poorly. These injuries are
often treated with surgery.
The most common term used is
comminution, however this can be
easy to confuse with the word
compound.
Alternative descriptive terms include
fragmentation and multi-part.
“There is a multi-part fracture of the
mid tibia with a full bone width of
medial displacement.”

30. “Important” features:
• Compound / open
High impact trauma can push the
fracture through the skin.
These injuries require surgical
management even if they can be
reduced. The protective skin barrier is
broken, so the wound is soiled and at
high risk of infection.
Open is often used as a descriptive
term instead of compound.

31. “Less important” features:
• Fracture orientation
The orientation of a fracture is often
described, but has very little impact on
management.
Like the direction of displacement, they
can imply a mechanism of injury.
Common descriptive terms are:
• Transverse
• Oblique
• Spiral
“There is a multi-part spiral fracture of
the distal humerus, with one cortical
width of posterior displacement.”

32. Overview:
– Film quality
– Anatomy
– Fractures
• Special cases
The best way to assess the flat bones
is to follow the curving lines of cortex
wherever you can. These lines often
cross between bones (because they
represent bone thickening along the
plane of mechanical loading).
Jagged or angular contours suggest
fracture.
“There is a cortical step in the right
acetabular region”.

33. Overview:
– Film quality
– Anatomy
– Fractures
• Special cases
Like the pelvis, the scapula is best
assessed by following the curving
lines of cortex.
Jagged or angular contours suggest
fracture.
“There are multiple cortical steps
involving the scapula spine, coracoid
process and glenoid”.