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IMAGING IN HIP DISORDERS
Dr. Sanjana B C
Resident,
JSS Medical College,Mysuru
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ANATOMY
• Ball and socket type
of Synovial joint
• One of most stable
joints in the body
• Articulation between
acetabulum and
femoral head.
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LINES AND ANGLES OF HIP
KLEIN’S LINE.
AP and frog-leg projections of the hip in slipped femoral capital
epiphysis. Note the lack of overlap across the line by the
femoral head.
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Coxa Vara.
Decreased angle
(double-headed
arrow).
Skinner’s Line
FEMORAL ANGLE.
LINES AND ANGLES OF HIP
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SHENTON’S LINE.
Hip Dislocation. Note the
interruption in the smooth arc
of Shenton’s line.
LINES AND ANGLES OF HIP
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Protrusio Acetabuli
The medial displacement
of the acetabulum and
femoral head in relation to
the line.
LINES AND ANGLES OF HIP
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ACETABULAR ANGLE. Observe the abnormally
wide angle (double-headed arrows) on the left
in association with congenital hip dislocation.
SYMPHYSIS PUBIS WIDTH- traumatic diastasis.
LINES AND ANGLES OF HIP
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LINES AND ANGLES OF HIP
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TEARDROP DISTANCE
The abnormality is the result of early Legg- Calvé-Perthes disease. Observe the crescent
sign in the femoral capital epiphysis (thick arrow).
LINES AND ANGLES OF HIP
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DEVELOPMENTAL DYSPLASIA
OF THE HIP
• Congenital or developmental deformation or misalignment of the hip
joint.
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DEVELOPMENTAL DYSPLASIA
OF THE HIP
• On radiography–
Disruption of Shenton’s line and/or
the iliofemoral line.
• CT arthrography with intra-
articular contrast to assess the
attempted concentric positioning
of the head within the acetabulum.
• MRI is employed in adult DDH to
assess for avascular necrosis and
for presurgical planning.
Small hypoplastic femoral capital epiphysis,
lateral and superior subluxation of the
femoral head, and a shallow acetabulum
(Putti’s triad ).
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PROXIMAL FOCAL FEMORAL DEFICIENCY
• Proximal focal femoral deficiency (PFFD) - a congenital disorder
characterized by varying severity of shortening and dysplasia of the
femur and acetabulum, and varus angulation of the proximal femur.
Classification system :
-In type A, the femur is shortened compared with the normal
size, but the femoral head is present and located within the
acetabulum.
-In type B, the femur is short with a varus angulation, and there
is a gap between the femoral head, which is located within the
acetabulum, and the femoral neck.
-In type C, the femoral head is rudimentary or absent. The femur
is markedly short, and the acetabulum is dysplastic.
-In type D, the entire femur is rudimentary, with absent femoral
head and acetabulum.
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•SCFE represents a Salter type I
fracture, through the physis,
resulting in the femoral head
“slipping” inferomedially with
respect to the femoral neck.
SLIPPED CAPITAL FEMORAL EPIPHYSIS
•Onset of a limp accompanied by hip pain referred to knee in
an obese adolescent boy.
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• Frayed metaphyseal margin
• Beaked inferior-medial epiphysis
• Increased teardrop distance
• Medial buttressing on the femoral neck
• Lateral buttressing on the femoral neck (Herndon’s hump)
• Curved contour of deformed proximal femur (pistol-grip deformity)
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LEGG-CALVÉ-PERTHES DISEASE
• An idiopathic avascular necrosis of the proximal femoral
epiphysis and occurs in the 3- to 12-year age group; 5:1 male
predominance.
STAGE I: EARLY
asymmetric femoral epiphyseal size (smaller on affected side)
apparent increased density of the femoral head epiphysis
widening of the medial joint space
blurring of the physeal plate
radiolucency of the proximal metaphysis
STAGE II: FRAGMENTATION
subchondral lucency
femoral epiphysis fragments
femoral head outline is difficult to make out
mottled density
thickened trabeculae
STAGE III: REPARATIVE
re-ossification begins
shape of the femoral head becomes better defined
bone density begins to return
STAGE IV: HEALED
changes depend on severity the femoral head may be nearly
normal or
may demonstrate flattening of the articular surface, especially
superiorly
widening of the head and neck of the femur
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• MRI excellent for early detection and identifying status of articular cartilage. Diminished
bright signal of marrow fat following loss of normal ciculation and thickening of non ossified
femoral cartilage and acetabular labrum.
• Coronal T1-weighted spin-echo MR
image shows flattening and
fragmentation of left proximal femoral
ossific nucleus (arrowheads) as well as
mild loss of containment. All ossific
fragments show abnormal signal
hypointensity.
• Isotopic scans cold in early phase
before plain film changes.
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TRANSIENT SYNOVITIS
• An aseptic inflammation of the hip, presumably of post viral etiology.
• It is the most common cause of hip pain or a limp in children under the age of ten years.
• The condition is self-limiting and treated with rest and analgesics.
• Ultrasound - presence of a joint effusion.
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• Septic joint occurs most commonly from pyogenic infection and may result
from haematogenous dissemination, contiguous spread of infection from
local tissues, direct inoculation, or contamination at surgery.
SEPTIC ARTHRITIS
• Radio graphically with increased teardrop distance or elevation of the gluteus
minimus fat stripe.
• Sub acute or chronic infections demonstrate bone erosions, loss of joint space and
areas of avascular necrosis.
• MRI is sensitive and more specific for early
cartilaginous damage
T1: low signal within subchondral bone
T2: perisynovial edema
C+ (Gd): synovial enhancement
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ACETABULAR FRACTURES
• Signs of capsular distension.
• widening of the teardrop space, and distorted fascial planes of
the psoas and gluteus medius muscles.
• obturator internus sign.
• Approximately 20% of all pelvic fractures in adults involve
the acetabulum.
• Almost all acetabular fractures are the result of indirect injury (injury
to the foot, knee, or greater trochanter of the femur).
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POSTERIOR DISLOCATION
• Most commonly caused by impact of
dashboard on knee.
• Hip flexed, internally rotated, adducted.
• X Ray - femoral head is usually displaced
posterior, superior, and slightly lateral to the
acetabulum and also internally rotated
hence the lesser trochanter is usually
obscured on AP view.
• Generally results from axial load applied to femur, while
hip is flexed.
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ANTERIOR DISLOCATION
• Extreme external rotation, less-pronounced abduction and
flexion.
X-ray signs –
• The lesser trochanter being more visible
due to external rotation.
• The hip is abducted and the femur head is
usually inferior to the acetabulum.
• Shenton's line is also broken.
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AVASCULAR NECROSIS
NECROSISAVASCULAR NECROSIS
• Most commonly seen on
anterolateral aspect
• Causes – trauma, fat
embolism, caissons disease,
alcoholism, steroid therapy,
collagen vascular diseases
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AVASCULAR NECROSIS
Femoral head AVN represents ischemic injury of femoral head.
The Ficat classification :
stage 0
plain radiograph: normal
MRI: normal
clinical symptoms: nil
stage I
plain radiograph: normal or minor osteopaenia
MRI: oedema
bone scan: increased uptake
clinical symptoms: pain typically in the groin
stage II
plain radiograph: mixed osteopenia and/or sclerosis and/or subchondral cysts, without any subchondral
lucency (crescent sign: see below)
MRI: geographic defect
bone scan: increased uptake
clinical symptoms: pain and stiffness
stage III
plain radiograph: crescent sign and eventual cortical collapse
MRI: same as plain film
clinical symptoms: pain and stiffness+/- radiation to knee and limp
stage IV
plain radiograph: end stage with evidence of secondary degenerative change
MRI: same as plain radiograph
clinical symptoms: pain and limp
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• MRI –
focal lesion in the anterosuperior portion of femoral head that
is well demarcated but is inhomogeneous
T1- low signal intensity
T2- double line sign, made of two concentric low signal
intensity bands with central hyperintense line which may
represent hypervascular granulation tissue.
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FEMOROACETABULAR IMPINGEMENT
• The theory behind femoroacetabular impingement is that certain
anatomic variations lead to impingement between the proximal femur and
acetabular rim with flexion and internal rotation.
• Two types-
Cam type
Pincer type
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Laterally prominent femoral head margins create femoral head asphericity bilaterally.
The superior portions of the acetabular labra are partially detached bilaterally
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HERNIATION PIT OF THE FEMORAL NECK
• The majority of these lesions are
asymptomatic, though larger lesions,
especially in runners, have been linked with
hip symptoms
It represents a herniation of synovium or soft tissues into the bone
through a cortical defect, hence the alternate name synovial
herniation pit
Radiologic Features- a discrete, sharply marginated geographic lesion at the antero-superior
aspect of the femoral neck.
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Thin-section CT - subcortical cyst with a thin sclerotic border
but may demonstrate defects in the cortical surface. Hounsfield
values vary from 30 to 50 HU with no significant contrast
enhancement.
MRI shows features consistent with fluid (high signal on
T2- and intermediate on T1-weighted images.)
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Thank You
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Editor's Notes
ACETABULUM Y-shaped epiphyseal cartilage Start to ossify at 12 years Fuse 16-17 years The articular surface of the acetabulum is horseshoe shaped and is deficient inferiorly at the acetabular notch
Nonarticular floor is called acetabular fossa
Head of femur 2/3rd of sphere, Pit just below and behind the centre of the head called fovea for ligamentum teres
The capsule encloses the joint and is attached to the acetabular labrum medially, Laterally it is attached to the intertrochanteric line of the femur in front and along the posterior aspect of the neck of the bone behind
Iliofemoral Ligaments- It is a strong, inverted Y-shaped ligament Its base is attached to the anterior inferior iliac spine above. Below the two limbs of Y are attached to the upper and lower parts of the intertrochanteric line of the femur.The strong ligament prevents overextension during standing
Pubofemoral Ligament- It is a triangular ligament. The base of the ligament is attached to the superior ramus of the pubis. The apex is attached below to the lower part of the intertrochanteric line. This ligament limits extension and abduction
Ischiofemoral Ligament-It is a spiral shaped ligament. Attached to the body of the ischium near the acetabular margin. Fibers pass upward and laterally and attached to the greater trochanter.This ligament limits the extension
Ligament of Head of Femur- It is flat and triangular ligament. It is attached by its apex to the pit on the head of the femur (fovea capitis), Attached by its base to the transverse ligament and the margins of the acetabular notch.
The cavity of acetabulum is deepened by the presence of a fibrocartilaginous rim called acetabular labrum
Transverse Acetabular Ligament- It is formed by the acetabular labrum as it bridges the acetabular notch. It converts the notch into a tunnel through which blood vessels and nerves enter the joint
Nerve supply- Femoral nerve, Obturator nerve, Sciatic nerve and Nerve to the quadratus femoris
Blood supply- obturator artery, medial and lat circumflex fem art, two gluteal arteries
On physical examination of the newborn, a palpable hip “click” can be elicited when combined external rotation–abduction and internal rotation–adduction are alternately applied to the flexed hip
(Ortolani’s test and Barlow’s test). Diagnostic ultrasound is the first choice for imaging investigation.
The pathophysiology of DDH is multifactorial, including shallow bony margin; delayed ossification of the acetabulum or femoral head; ligamentous laxity; and neuromuscular disease with shortening, weakness, or contractures. (6). Hip flexion associated with breech presentation induces DDH by causing shortening of the psoas and decentering of the femoral head, a mechanism that also results from other deformities and neuromuscular disorders.
Plain films are most useful from 2 to 8 months (4,5) and reliable depiction of DDH can often be made after 4–6 months.
In adolescents and adults, long-standing dislocation manifests as a shallow acetabulum and a large, flattened femoral head with
superior and lateral displacement. The head is at risk for complicating avascular necrosis. On occasions a neo- or pseudoacetabulum
is formed on the posterosuperior surface of the iliac wing. (Figs. 3-106 and 3-107) The degree of secondary osteoarthritis
is often surprisingly low grade or even absent.
Ultrasound allows visualization of the bony and cartilaginous acetabular margins, the cartilaginous femoral head, the
amount of femoral head coverage by the acetabulum, and with stress testing assessment of hip stability. (3–5,7)
The hip is scanned in the coronal plane, and the bony (α) and cartilaginous (β) roof angles are measured. The critical measurement is the cartilaginous (α) angle and is the basis for classifying the degree of dysplasia. (3) (Table 3-4) Dynamic hip ultrasound may show no movement, slight movement, true subluxation, and frank dislocation. (7) Following the application of the harness sonographic reassessment at 4- to 6-week intervals over 2–3 months are performed to monitor and document the therapeutic response.
Causes - Frohlich;s syndrome, renal osteodystrophy, trauma, rickets and radiotherapy.
Complications – AVN, OA, chondrolysis, coxa vara deformity.
Metaphyseal blanch sign of steel
According to the degree of epiphyseal involvement as assessed radiographically.
Group I and II patients have good prognosis.
Affected children are only mildly ill or have recently sustained a low grade respiratory tract infection.
A joint aspiration is
typically necessary to confirm the diagnosis.
The fat plane overlying the obturator internus muscle should be observed for medial displacement or asymmetry. This
indicates a hematoma beneath or within the obturator internus.
Judet and letournel classification
type I: fracture inferior to the fovea capitis, a small fracture not involving the weightbearing surface
type II: fracture superior to the fovea capitis, a large fracture involving the weightbearing surface
type III: type I or II fracture with a fracture of the femoral neck, has an increased risk of AVN
type IV: type I or II fracture with a fracture of the acetabular wall, usually the posterior wall
Posterior dislocation may have associated fractures of the posterior lip of the acetabulum and/or injury to the acetabular labrum.
AP x-rays will usually be sufficient for the diagnosis, although associated acetabular fractures will require CT to fully characterise.
Anterior and posterior dislocations may appear similar as both demonstrate loss of the normal joint congruency between the femoral head and the acetabulum.
In a well centred AP film the posteriorly dislocated femoral head will appear smaller than the contralateral hip, and vice versa, on account of geometric magnification 2
CT Most helpful after hip reduction. Reveals: Non-displaced fractures.
Congruity of reduction.
Intra-articular fragments.
Size of bony fragments.
By convention, the term avascular (ischemic) necrosis generally is applied to areas of epiphyseal or subarticular involvement, whereas "bone infarct" usually is reserved for metaphyseal and diaphyseal involvemen
Avascular necrosis is characterized by osseous cell death due to vascular compromise [1]. Avascular necrosis of bone results generally from corticosteroid use, trauma, pancreatitis, alcoholism, radiation, sickle cell disease, infiltrative diseases (e.g. Gaucher’s disease), and Caisson disease
This leads to shearing and impaction of the anterior articular cartilage of the femoral head, as well as anterior
labral tears.
The first is the “, thought to be caused by an enlarged femoral head or an abnormal contour of the femoral head/neck junction, which causes impingement anteriorly against a normal acetabulum (Fig. 6). The second, or “, is thought to be due to “over-coverage” of the femoral head anteriorly from either coxa profunda or a retroverted acetabulum
There is some evidence that they may result from femoroacetabular impingement