Transcript Joint capsule

MRI Anatomy of the Shoulder
Functional Anatomy
Glenohumeral joint is a ball and socket synovial.
Glenoid cavity inherently unstable.
Stability provided by:
i)Static constraints
- 3 glenohumeral ligaments
- glenoid labrum
- joint capsule
ii)Dynamic constraints,
rotator cuff muscles
counteract the action of the deltoid by preventing the head of the humerus
from moving superiorly when the arm is raised
The glenohumeral joint has the following supporting structures:
Superiorly
Coraco-acromial arch
Long head of the biceps tendon
Tendon of supraspinatus muscle
Anteriorly
Anterior labrum
3 Glenohumeral ligaments
-SGHL, MGHL, IGHL
(anterior band)
Subscapularis tendon
Posteriorly
Posterior labrum
Posterior band of the IGHL
Infraspinatus tendon
Teres minor tendon
Articular surfaces
The shoulder joint is composed of 3 bones and five
articulations.
Bones:
Scapula
Humerus
Clavicle
Articulations:
Glenohumeral joint
Acromio-clavicular joint
Scapulothoracic joint
Sternoclavicular joint
Coracoclavicular joint
Joint capsule
• Attached proximally to the glenoid labrum
• Attached distally to the anatomical neck of the humerus
• Capsule is thickened anteriorly by glenohumeral
ligaments
• Herniation of synovial membrane through an anterior
defect in capsule & glenohumeral ligaments forms the
subscapular bursa
Subdeltoid
Between joint capsule and
deltoid muscle
Subcoracoid
Between joint capsule and
coracoid process
Coracobrachial
Between subscapularis and
coracobrachialis
Subacromial
Between joint capsule and
acromion
Subscapular bursa
Between joint capsule and
subscapularis tendon
Bursae
Rotator Interval
• Triangular space between the supraspinatus and
subscapularis tendons
– Contains long head of biceps and SGHL
– Acts to prevent anterior dislocation of the shoulder
Ligaments
• 3 glenohumeral ligaments
– Superior
– Middle
– Inferior
• Coracohumeral ligament
• Transverse humeral ligament
– Between greater and lesser tuberosities of
humerus, maintains long head of biceps in bicipital
groove
Superior glenohumeral ligament
Coracohumeral ligament
Long head biceps tendon
SGHL Sagittal
SGHL Axial
Middle glenohumeral ligamant
MGHL Sagittal
MGHL Axial
Inferior glenohumeral ligament
Axillary recess
Subacromialsubdeltoid
bursa
Glenoid labrum
•
The glenoid labrum is a
fibrocartilaginous structure that
attaches to the glenoid rim and is
about 4 mm wide.
•
increases the superior-inferior
diameter of the glenoid by 75%
and the anterior-posterior
diameter by 50%
•
Anteriorly, the glenoid labrum
blends with the anterior band of
the inferior glenohumeral
ligament.
•
Superiorly, it blends with the
biceps tendon and the superior
glenohumeral ligament.
•
It is usually rounded or triangular
on cross-sectional images.
Labral anatomy: Axial
• The normal labrum
demonstrates low signal
intensity on all pulse
sequences, due to the
lack of mobile protons in
this dense fibrocartilage.
• On cross sectional
imaging, the normal
labrum is most commonly
triangular, but can also be
round, cleaved, notched,
flat, or absent.
Labral Anatomy: Coronal
• A fat suppressed
oblique coronal T2weighted MR image
demonstrates
homogeneously low
signal intensity in the
normal superior
labrum.
Labral variants
• These normal variants are all located in the
11-3 o'clock position.
• It is important to recognise these variants, because they
can mimick a SLAP tear.
• These normal variants will usually not mimick a Bankartlesion, since these are located at the 3-6 o'clock position,
where these normal variants do not occur.
Sublabral recess
Synovial recess between the superior labrum and the glenoid rim created by the
attachment of the biceps tendon on the supraglenoid tubercle. Because of this recess,
the labrum does not attach to the glenoid rim at the 12 o'clock position.
There are 3 types of attachments of the superior labrum: Type I No recess between
glenoid cartilage and labrum Type II Small recess. Type III Large sublabral recess.
Sublabral Foramen
An unattached anterosuperior
labrum at the 1-3 o'clock
position.
Anterior to biceps tendon
It is seen in 11% of individuals.
Not to be confused with a
sublabral recess or SLAP-tear,
which are also located in this
region.
Differences between an sublabral recess and a SLAP-tear:
A recess more than 3-5 mm is always abnormal and should be regarded as a SLAPtear.
Buford complex
Congenital labral variant
2 Features: Anterosuperior labrum is absent in the 1-3
o'clock position
Middle glenohumeral ligament is usually thickened.
It is present in approximately 1.5% of individuals.
Os Acromiale
Results from failure of one of the acromial ossification
centers to fuse.
5% of the population.
Usually an incidental finding, regarded as a normal
variant.
May cause impingement because if it is unstable, it
may be pulled inferiorly during abduction by the
deltoid, which attaches here.
On MR an os
acromiale is best seen
on superior axial
images.
Acromion: 3 types
Type 1 is a flat undersurface with a high angle of inclination.
Type 2 is a curved arc and decreased angle of inclination.
Type 3 is hooked anteriorly with a decreased angle of inclination.
Axial Anatomy
The axillary artery begins at the lateral border of the first rib as a
continuation of the subclavian artery. It changes its name to brachial
artery at lower inferior border of the teres major muscle (8).
Axial
Deltoid
1)Anterior clavicular fibres – arise from
superior anterior aspect of lateral
clavicle
1)Lateral acromial fibres – arise from
superior aspect of acromion process
1)Posterior fibres – arise from posterior
border of spine of scapula
Supraspinatus
muscle
Relatively small muscle
Runs from the
supraspinatous fossa of
scapula to the greater
tubercle of the humerus
Axial
Axis of supraspinatous tendon
The supraspinatus tendon is the
most important structure of the
rotator cuff and subject to
tendinopathy and tears.
Tears of the supraspinatus tendon
are best seen on coronal oblique and
ABER-series.
In many cases the axis of the
supraspinatus tendon (arrowheads)
is rotated more anteriorly compared
to the axis of the muscle (yellow
arrow).
When you plan the coronal oblique
series, it is best to focus on the axis
of the supraspinatus tendon.
The attachments of the 3 rotator
cuff muscles that insert onto the
greater tubercle of the humerus
Sagittal
can be abbreviated SIT when
viewed from superior to inferior:
post
Supraspinatus
Infraspinatus
Teres minor
post
SITS inlcudes Subscapularis which inserts
onto the lesser tubercle of the humerus
Axial
Pec major
Deltoid anterior
Pec minor
Supraspinatus inserts
most superiorly to
greater tuberosity
humeral head
Subscapularis
Infraspinatus
Deltoid posterior
Infraspinatus (SIT)
•
•
•
Thick triangular muscle which
occupies most of the infraspinatous
fossa
Attaches medially to the infraspinatus
fossa and laterally to the middle facet
of the greater tubercle of the humerus
Trapezoidal insertion of infraspinatus
onto humerus is much larger than the
insertion of the supraspinatus
*Tip*
Coronal oblique MRI
• Supraspinatus – fibres run horizontally
• Infraspinatus – fibres have a slightly oblique orientation
Subscapularis
Large triangular muscle which fills the subscapular fossa
Inserts onto the lesser tubercle of the humerus
Subscapular fossa = anterior
Infraspinatous fossa = posterior
ant
post
Axial
Deltoid as
one
Coracobrachialis
Teres minor
Coracobrachialis is the
smallest of the three
muscles that attach to the
coracoid process. The other
2 muscles are pectoralis
minor and biceps brachii.
Distal insertion upper
medial aspect of arm
Teres
minor
(SIT)
Origin:
Superior part of lateral border of scapula
Insertion:
Inferior facet of greater tuberosity of
humerus
The short head of the biceps
originates from the coracoid
process (2)
Axial
The long head
originates from the
supraglenoid tubercle
(3)
Tendon of long head passes down along the
intertubercular/bicipital groove of the
humerus into the joint capsule
Both heads arise on the scapula and join
to form a single muscle belly which is
attached to the upper forearm.
Long head forms biceps-labral complex with
superior glenohumeral ligament
When the humerus is in motion, the
tendon of the long head is held firmly
in place in the bicipital groove by the
greater and lesser tubercles and the
overlying transverse humeral
ligament.
Coronal
Long head
Coronal anatomy
Coronal
Trapezius
Posterior humeral
circumflex artery and
axillary nerve
Triceps
Teres major
extends
longitudinally from
the occipital bone
to the lower
thoracic vertebrae
and laterally to
spine of the scapula
Teres major
It arises from the dorsal surface of
the inferior angle of the scapula
Inserts onto intertubercular sulcus of
humerus
(Teres minor)
Coronal
Infraspinatus
Teres minor
Triceps
Teres major
Coronal
Supraspinatus
Subscapularis
Teres major
Sagittal Anatomy
Sagittal
P
A
Acromioclavicular joint
Axial: Clavicle medial
Acromion lateral
Sagittal: Acromion posterior
Coracoid anterior
The undersurface of the
acromion should align with the
undersurface of the clavicle
Cl
Ac
Ant
Co
Post
Sagittal: SIT
MR shoulder arthrogram
• Technique whereby injection of contrast media into
the joint allows for evaluation of capsule and internal
joint structures.
• Originally performed using plain radiography.
• Now injection of gadolinium allows MR
arthrography.
• CT arthrograms can also be performed.
Advantages
• Joint distension, outlining intra-articular
structures
• Improved detection of tears, including
articular surface partial tears
• Demonstration of communication between
joint and extra-articular abnormalities eg.
Paralabral cysts and bursae.
Disadvantages and pitfalls
• Risks assoc with needle placement into joint:
infection, haemorrhage, synovial reaction.
• Avoid oblique position – glenoid in profile –
aiming for joint space places the labrum at risk
• Correct needle positioning is essential
– Extra articular contrast can complicate findings on MR
and simulate tears
Technique
• Fluoroscopically guided anterior approach is
most widely performed.
• Perform routine preparation
–
–
–
–
–
Correct patient
Correct side
No iodine allergies
Explain procedure to patient, obtain consent
Confirm indication
Indications
•
•
•
•
Assessment of integrity of rotator cuff
Evaluation of shoulder instability
Diagnosis of labral pathology
Diagnosis of adhesive capsulitis
Technique
• Sterile procedure
• Fluoroscopically guided
• Obtain control images of shoulder
– Patient supine, AP view
– Arm in external and internal rotation
– Angle tube to view acromion in profile – clear
visualisation of sub-acromial space
– Evaluate for calcium deposition in tendons
Patient Positioning
•
•
•
•
•
•
Supine position creates
oblique orientation of
glenoid surface.
Posterior glenoid overlaps
humeral head on AP
Anterior glenoid lies medial
to humeral head
Thus needle directed AP at
humeral head will not injure
anterior labrum
External rotation exposes a
larger articular surface
anteriorly
Placing a sandbag in the
patient’s hand may help
maintain the position
Technique
• Determine skin entry site
using fluoroscopy
• Just lateral to the medial
cortex of the humeral head
(never medial)
• At junction of middle and
lower third of humeral head
• Ideally central in
fluoroscopic image
• Locally anaesthetise skin
and subcutaneous tissue
Technique
•
Prepare contrast whilst allowing local anaesthetic to take effect (can
also be done before procedure starts)
•
Bloem protocol:
–
–
–
–
–
20 ml syringe
10 ml sterile water
5 ml iodine based non-ionic LOCM (eg.Ultravist, Omnipaque)
5 ml lignocaine
0.1 ml gadolinium
•
Other:
•
Syringe connected to connecting catheter(line)
– Test injection with 1-2 ml of lignocaine
– Contrast: 10 ml saline, 10 ml Iodine LOCM, 0.1 ml gadolinium, 0.3 ml
1:1000 adrenaline
Technique
•
•
•
•
•
•
Advance needle (usually 20G
spinal needle with stylet) in
direct AP direction
posteriorly.
Continue until contact with
humeral head.
Consider test injection with
lignocaine.
Should only meet low
resistance when in joint
space
If high resistance – possibly
in hyaline cartilige – carefully
manipulate needle by
rotation and minimal
retraction (few mm)
Loss of resistance indicates
either intra-articular or
bursal location
Technique
• Inject iodinated contrast
to distinguish between
intra-articular and bursal
location
• Intra-articular contrast will
collect in glenohumeral
joint space
• If intra-articular position is
confirmed, continue with
proper contrast injection
• Usually inject 14 – 16 ml
of contrast, depending on
patient and pathology.
Alternative: Posterior approach
•
•
•
When suspecting anterior pathology.
Avoids the interpretative difficulties that may be associated with
anterior extracapsular contrast extravasation
Aim for the inferomedial quadrant of humeral head within
boundary of anatomic neck (interrupted line).
Other techniques
• Inject only water, no gadolinium
– Achieves effect of distension
– Need to use T2 sequences
– Disadvantage:
• Difficult to distinguish between small full thickness and partial
tears
• Indirect arthrogram
–
–
–
–
–
1 mmol/kg Gd IV
Exercise joint for 5 to 5 minutes
Gd passes into joint space
Can perform T1 images
Disadvantages:
• Joint not distended
• Extra-articular structures will also enhance
MR technique
• Three plane T1 with fat sat
• T2 with fat sat axial and coronal oblique (Consider Ax
GRE to evaluate for calcification)
• Sagittal oblique T1/PD without fat suppression
• Some protocols suggest pre contrast T2 sequences.
– Detection of intra-substance and bursal surface tears.
– Pre-existing fluid collections and cysts
• Coronal oblique parallel to supraspinatus tendon (not
muscle)
• Sagittal oblique perpendicular to glenoid surface
• (ABER – Abduction and External rotation sometimes
used for evaluation of anterior and inferior GHL’s)
ABER view
Images in the ABER position are
obtained in an axial way 45º off the
coronal plane (figure).
In that position the 3-6 o'clock
Labral tears The abduction external
rotation (ABER) view is excellent for
assessing the anteroinferior labrum at
the 3-6 o'clock position, where most
labral tears are located.
Inferior glenohumeral ligament
stretched resulting in tension on the
anteroinferior labrum, allowing intraarticular contrast to get between the
labral tear and the glenoid.
Rotator cuff tears Very useful for both
partial- and full-thickness tears of the
rotator cuff. Releases tension on the
cuff relative to the normal coronal view
obtained with the arm in adduction.
Rotator cuff tears
• Arthrography improves detection of
tears as the joint is being distended
and contrast forced into small
defects.
• T1 (quicker) sequences with
improved SNR can be used
• Diagnoses full thickness tears and
articular surface partial thickness tear
• Not of value in intra-substance or
bursal surface partial thickness tears
• Full-thickness tear will demonstrate the
gadolinium contrast solution extending first
through a defect in the cuff and then into the
subacromial-subdeltoid bursa.
• Articular-surface partial-thickness tears show a
focal extension of the contrast solution into the
substance of the tendon.
• Fat suppression is necessary as peribursal fat may
mimic contrast.
References
•
•
•
•
•
•
Ryan S, McNicholas M, Eustace S. Anatomy for diagnostic imaging.
CT and MR Arthrography of the Normal and Pathologic Anterosuperior
Labrum and Labral-Bicipital Complex. October 2000 RadioGraphics, 20,
S67-S81.
www.radiologyassistant.nl Radiology Assistant: MR Shoulder Part I.
http://musculoskeletal-radiology.blogspot.com/2006/09/glenohumoralligaments.html
Jacobson et al. Aids to Successful Shoulder Arthrography Performed with a
Fluoroscopically Guided Anterior Approach. Radiographics. 2003; 23:373–
379
Beltran et al. MR Arthrography of the Shoulder: Variants and Pitfalls.
Radiographics. 1997; 17:1403-14 12