INDEX
- Achondroplasia
- Aneurysmal Bone Cyst
- Ankylosing spondylitis
- Caffey disease
- Fibrous dysplasia (FD)
- Galeazzi fracture-dislocation
- Kienbock disease
- Maisonneuve fracture
- McCune-Albright syndrome (Polyostotic FD)
- Paget disease of the bone
- Patella alta
- Patella baja
- Tillaux fracture
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MSK:
McCune-Albright syndrome (polyostotic FD)
ACHONDROPLASIA
A form of dwarfism; Most common skeletal dysplasia
Autosomal dominant
Clinical features:
MSK:
- Prominent forehead, depressed nasal bridge
- Short limbs, short trunk
- Bowed legs
- Narrow thorax => respi.distress
Neuro:
Neuro related complication rate 40-50%
- Hydrocephalus
- Cord compression usually at Thoracolumbar region - Cauda equina (onset at average age 38yo)
*(worsens as narrowing progresses, degeneration & lumbar hyper-lordosis)
- Brainstem / Cord compression at Cervical spine or Foramen magnum (in neonate / childhood)
Pathology:
- Decreased cartilage matrix production
- Decreased endochondral ossification
Radiograph:
MSK:
Calvarium
- Large skull (frontal bonew), short skull base, small foramen magnum
- Flat nasal bridge
- Broad mandible
Spine & Pelvis
- Scoliosis
- Anterior beaking of vertebra body
- Short pedicles => Narrow cervical canal => Spinal stenosis
- "Bullet-shaped" vertebral bodies, Posterior vertebral scalloping
- Decreased interpedicular distance caudally
- "Tombstone" appearance: Squared iliac wings, small sciatic notch & flat acetabular roof
- "Champagne glass" pelvic inlet
- Horizontal sacrum on lateral view
Limbs
- Rhizomelia: short proximal limb
- Metaphyseal flaring in the long bones
- Short and wide long bones
- Trident hands
- Short femoral necks
- Fibular growth > Tibia growth
- "Chevron deformity" = V-shaped notches in growth plates
- a/w patella baja
Thorax
- Short, anteriorly flared concave ribs
- Narrow thorax, decreased AP distance
Neuro:
- Lateral ventricles dilatation
- As mentioned in MSK section:
-- Spinal stenosis
________________________________________________________________
Findings:
DDx:
Clinical feature:
ANEURYSMAL BONE CYST
Benign reactive vascular process
5-20yo
Findings:
- Expansile, lytic lesion
- Thin septations within the lytic lesion => "soap bubble" appearance
- Circumscribed
- Metadiaphyseal, Posterior elements of vertebrae
- +/- Codman triangle periostitis
MRI:
- Multiple cysts with thin contrast enhancing septations
- Fluid-fluid levels within the cysts
- Fluids within may demonstrate different signal intensities (due to haemorrhage)
- Negative findings: NO ossification / calcification within the lesion
- Negative findings: Does NOT extend to the physis
*ABC may represent a secondary hemorrhagic process related to antecedent solid tumor eg chondroblastoma, GCT, fibrous dysplasia
Rx:
- currettage
________________________________________________________________5-20yo
Findings:
- Expansile, lytic lesion
- Thin septations within the lytic lesion => "soap bubble" appearance
- Circumscribed
- Metadiaphyseal, Posterior elements of vertebrae
- +/- Codman triangle periostitis
MRI:
- Multiple cysts with thin contrast enhancing septations
- Fluid-fluid levels within the cysts
- Fluids within may demonstrate different signal intensities (due to haemorrhage)
- Negative findings: NO ossification / calcification within the lesion
- Negative findings: Does NOT extend to the physis
*ABC may represent a secondary hemorrhagic process related to antecedent solid tumor eg chondroblastoma, GCT, fibrous dysplasia
Rx:
- currettage
ANKYLOSING SPONDYLITIS
Shown here are frontal and lateral projections of the lumbosacral spine.
Findings:
- Bilateral symmetrical SIJs ankylosis
- Squaring of the vertebral bodies on the lateral view
- Bamboo spine: Syndesmophytes bridging the vertebral bodies
- Dagger sign: Dense ossification of the interspinous ligament
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Seronegative spondyloarthropathy
Chronic
Inflammatory
15-35yo male
Some HLA-B27 +ve
Distribution:
- Axial skeleton
- Synovial/ cartilaginous joints
- Entheses
SIJs: one of the earliest manisfestation. Bilateral, symmetric. Erosion => Subchondral sclerosis => Ankylosis
Vertebral body:
MRI - shiny corners due to erosion along the corners
Squaring of the vertebral bodies
Ossification and ankylosis along the annulus (bamboo spine)
Ossification and ankylosis along the interspinous ligament (dagger sign)
+/- Posterior scalloping of the vertebral body
Hip joints:
Axial migration of femoral head
Joint space loss
Osteophyte and head-neck junction
Osteoporosis (advanced stage)
DDx:
- Crohn disease (sacroiliitis can be identical to that of Ank.Spond. ie bilateral symmetrical erosion & ankylosis)
- Psoriatic arthropathies (SIJs: bilateral, assymetric)
- Reactive arhtropathies (SIJs: bilateral, assymetric)
________________________________________________________________CAFFEY DISEASE
aka: Infantile cortical hyperostosis
Unknown aetiology
Mandible > Clavicle > Upper limbs
Onset:
first few (5) months of life
Clinical feature:
- Fever
- Irritability
- Soft tissue swelling
Radiograph:
- Coarse, irregular, asymmetric periosteal reaction (diaphysis)
- Cortical thickening (diaphysis)
- Soft tissue swelling over the affected areas
- Ulna, clavicle, mandible > long bones, ribs, scapula
DDx:
- Physiologic periosteal reacion (only occurs in up to 6mth old, symmetry, does not involve metaphysis)
- Infection (periosteal reaction at metaphyseal region); (in virus eg variola: hyperostosis)
- Prostaglandin Rx (for congenital heart disease)
- Trauma
- Hypervitaminosis A (mandible typically not affected)
________________________________________________________________FIBROUS DYSPLASIA
Developmental disorder
Benign
Intramedullary lesion
Polyostotic (less common) or Monostotic
- Note McCune-Albright's syndrome in some polyostotic cases
- Rib is the most common site in monostotic disease
Asymptomatic, or painful when it is large
Pathology:
Normal trabecular bone replaced by (1) mainly fibrous tissue (2) Osteoid (3) Woven bone.
Complication:
- Pain
- Pathological fracture
- Bone deformity
- Malignant transformation to Fibrosarcoma (Polyostotic 5-10%, Monostotic rare)
Distribution:
- Craniofacial (Giving lion's face appearance - leontiasis ossea)
- Ribs
- Long bones
- Pelvis
Plain radiographs:
- Intramedullary
- Metadiaphyseal
- Expansile lytic lesion +/- internal calcification
- Ground-glass appearance of the lesion (due to fibrous tissue and immature bones)
- 'Sheperd's crook' - bent proximal femur (also happens in other weight-bearing bones)
Scintigraphy:
- increased activity of the lesion
DDx:
- Primary bone tumor
- Hyperparathyroidism (?brown tumor)
- Cherubism (in facial bone FD)
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Galeazzi fracture-dislocation
Patient with painful right forearm after fall.
 |
| Do not forget to check the joints proximal and distal of a fracture site. Note widening of DRUJ and a short oblique radial shaft fracture. Additionally, an avulsion of the ulnar styloid. |
 |
| Dorsal dislocation of the distal ulna, this can be easily missed, especially in rotated lateral projection. |
Galeazzi fracture-dislocation = Radial shaft (diaphysis) fracture + Distal RadioUlnar Joint (DRUJ) dislocation.
- Fracture is typically transverse or short oblique.
- Dislocation of the distal ulnar is typically dorsal.
- +/- Other radiographically evident injury: Ulnar styloid fracture
Mechanism:
Fall on outstretched hand + Pronated arm (imagine this will load all the weight on the radius = fracture)
Clinical features:
Piano key sign (where the dorsally dislocated distal ulna can be felt - like a piano key)
Specific complication:
- Extensor Carpi Ulnaris (ECU) tendon entrapment
- Ulnar nerve injury
- Triangular fibrocartilage complex (TFCC) injury
Rx:
Surgical - ORIF.
Not to confuse with Monteggia fracture-dislocation, remember "MUGR"- which always indicates the fractured bone:
- Monteggia => Ulnar fracture
- Galeazzi => Radial fracture
Kienbock disease
Osteonecrosis of lunate / Lunatomalacia
20-40yo male (M:F = 2:1) / labourer
3rd-5th decade
Usually unilateral (dominant hand)
progressive pain and swelling of wrist, usually of the right
Risk factor: ulnar minus variance in ~75% due to microtrauma
Clinical features:
- Pain on passive dorsiflexion of 3rd finger
- Wrist pain radiating to forearm
- Wrist stiffness, swelling
Investigation:
Tc scintigram (3-phase)
- Highly accurate, but current practice more in favor of MRI
Radiographic Staging (of Lichtman's) (via plain radiograph and MRI)
*note traditionally staging done via Clinical features & Plain radiograph
Plain radiograph
|
MRI
| |
Stage I
|
Bone oedema
Disruption of the trabecular pattern | |
Stage II
|
Sclerotic changes of lunate
+/- Reduced lunate height on the radial side |
All sequences: Low signal exception of +/- marrow oedema
Bone morphology still normal
|
Stage III
|
Lunate collapses
ð Proximal migration of Capitate
|
As in plain radiograph
|
IIIA
|
No rotatory Scaphoid subluxation
| |
IIIB
|
Rotatory Scaphoid subluxation
(due to Scapholunate ligament injury) | |
Stage IV
|
Surrounding carpal joints/bone/radius degeneration/arthritis
|
No more bone marrow oedema
Lunate collapse
As in plain radiograph |
Rx:
- Conservative
- Symptomatic + Splinting
- Surgical
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MAISONNEUVE FRACTURE
Young patient came in after twisted ankle in soccer.
 |
| Fracture of the medial malleolus |
Based on ankle radiograph alone, this would be a fracture that can be treated outpatient follow-up.
But always check the joint above. So here's the tibia/fibula radiograph...
 |
| Note fibular fracture in the proximal 1/3 |
Now, it's not just medial malleolar fracture.
Proximal 1/3 fibular fracture + Disruption of deltoid ligament / Medial malleolar fracture
= Maisonneuve fracture
Mechanism: External rotatory injury of the leg (Eversion injury)
Ankle injury in this entity can be subtle, sometimes present with widened medial space of the tibio-talar joint alone (>5mm)
Associated with ligamentous injury:
- Anterior talofibular ligament (ATFL)
- Tibia-fibula syndesmosis
- Interosseous membrane (Tibia-Fibula)
- Deltoid ligament
Rx:
- Surgical fixation as it is an unstable injury
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McCune-Albright syndrome (polyostotic FD)
Rare. Genetic disorder (Gs alpha gene)
? incidence M:F = 1:1
no predilection to specific ethnicity
Classic triad:
- Polyostotic fibrous dysplasia (FD)
- Endorine disorder
- Café au lait spots (unilateral: ie does not cross midline)
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Polyostotic FD accounts for ~2/3 of the FD. (as opposed to monostotic FD)
- Tend to be unilateral
- Bony deformity - usually the long bones (lower limbs > upper limbs). Also facial bones with craniofacial deformity
- Pathological fracture
- Nerve impingement from the bony growth
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Endocrine disorder most commonly manifest in the form of precocious puberty. Other endocrine disorder that may occur includes increased activity (hyper-) Thyroid, Cortisol, Growth Hormone (acromegaly).
These are independent (peripheral cause) instead of intracranial hypothalamic (central cause)
- Gonadotrophin: Precocious puberty - cyclical vaginal bleeding, breast development (more common in female, and can happen at very early age ie few months old)
- Thyroid: Hyperthyroidism, tachycardia, osteoporosis
- ACTH: Cushing syndrome (less common), adrenal nodule, hypertension
- Growth hormone: Gigantism, acromegaly
=================================================
Café au lait spots
- Unilaterality ie does not cross midline
- border of the spots are described as coast of Maine (irregular), different from that of Neurofibromatosis (smaller size and smooth border)
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Others:
- Hypophosphatemia => Rickets
=================================================
Complications:
- Bony deformity, Rickets
- Nerve impingement
- Risk of thyroid malignancies
- Risk of breast Ca from prolonged exposure to oestrogen in precocious puberty
- Risk of other malignancies from irradiation therapy
- Sudden death
=================================================
Investigations:
- Skeletal radiograph survey: aid by Bonescan
- Pelvic US: unilaterally enlarged ovarian cyst
- Bonescan: detecting presence of other sites for FD (99m Tc-methylene diphosphonate)
- CT: bilateral enlarged adrenal glands (as opposed to unilateral in adenoma / Ca)
==================================================
Differential Diagnosis:
- Neurofibromatosis: Café au lait spots, Precocious puberty as a potential manifestation of hypothalamic optic glioma
_________________________________________________
PAGET DISEASE OF THE BONE
Shown here is frontal and lateral view of lumbosacral spine x-ray.
Description:
- Coarse vertical trabeculae and expansion at L4 body
- Picture frame appearance: Sclerotic periphery, relative lucent centre of the vertebral body
- L3 over L4 Grade1 retrolisthesis
- Incidental left renal lower pole calculus
X-ray appearances:
- Decreased bone density
- Increased density of trabeculae (prominent coarse or fine trabeculae)
- Enlarged intertrabecular spaces (ballooning of the vertebral body): expanded and become square-ish
- The posterior elements may be affected
- Description: "jail house striations" "accordian" "honeycomb" "corduroy" appearance
Diagnosis:
- Paget disease of vertebral body
Bone scintigraphy:
- Abnormal intense radiotracer uptake; Subcortical region
- During active phase of the disease, there may be increased uptake in all 3 phases of the bonescan (usually uptake at the delayed phase)
- Used to assess response to therapy (in which case shows reduced radiotracer uptake)
Discussion:
- Middle-aged and elderly (5th - 6th decade)
- M > F (slightly)
- Predominantly polyostotic
- Skull, spine, pelvis, lower limbs
- Malignant transformation may occur
3 phases:
(1) Osteolytic
- radiolucent changes of the bone
- eg "osteoporosis circumscripta" of the calvarium
- eg "blade of grass" appearance of the tibia
(2) Mixed
- mixture of bone resorption & formation, ie radiolucent change with prominent trabeculae
- ie "cotton wool" appearance
(3) Osteoblastic
- increased bone density, cortical thickening, bone deformity
- eg thickening of the iliopectineal & ilioischial lines of the pelvis
- eg hemipelvic asymmetry and enlargement
a/w "Banana fracture" - Looser lines
a/w "Flame shape lucency towards diaphysis"
Pathology:
- Excessive abnormal bone remodelling
=> increased Osteoblastic activity => increased ALP level
=> increased Osteoclastic activity => high hydroxyproline in urine
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PATELLA ALTA
Abnormally high lying patella.
Associated conditions including acute rupture of the patellar tendon and abnormally long patellar tendon.
Acute rupture of the patellar tendon usually happens in young population, with a sudden extension of the knee. (sudden contraction of the quadriceps, pulling the patellar tendon)
Also related to quadriceps atrophy, subluxation, chondromalacia and cerebral palsy.
 |
| Normal patella location |
 |
| Abnormally high patella: Patella alta |
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Insall-Salvati ratio =
Diagonal length of patella / Length of patellar tendon
Normal figure: 1
Patella alta: < 0.8
Advantage: This measurement is relatively independent of the degree of the flexion of the knee.
 |
| Insall-Salvati ratio: Diagonal length of patella / Length of patella tendon |
 |
| Patella alta. |
==========================================
Another method:
Using the Blumensaat's line, although this requires the knee to be flexed 30 degrees.
 |
| Blumensaat's line. Patella crosses the line in patella baja |
 |
| Blumensaat's line: Patella does not cross the line |
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PATELLA BAJA
Abnormally low lying patella = Patella baja/infera
Usually occurs in elderly
(note the level of tendon rupture / patellar fracture goes up superiorly as one ages, eg from tibial tubercle at young age, to patellar tendon, to patella, to the quads tendon)
Determine if it is post-surgical changes; if it is symptomatic.
Associated conditions include poliomyelitis and achondroplasia.
Remember, when there's low lying patella, means there's also high lying patella (Patella alta).
 |
Patella Baja / Patella Infera:
note the abnormally low lying patella.
|
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TILLAUX FRACTURE
12yo boy presented with painful swollen ankle after soccer injury.
 |
| Skeletally immature bone. Clear fracture line is seen in the middle. |
 |
| Fracture line is seen in the anterior aspect of the distal tibial epiphysis. |
Diagnosis: Tillaux fracture:
This fracture is specific for the paediatric population (12-15yo). Why?
- Because this is an injury due to maturation (closing of the epiphysis) of the distal tibial epiphyses at different timing.
- Distal tibial epiphysis: 3 centers. The anterolateral center closes last (which is the avulsed segment in Tillaux fracture).
- ATFL attaches to this part of the bone, therefore in the event of forced external rotation, this anterolateral segment is avulsed.
Salter-Harris type 3 fracture: part of the epiphysis broken off from at the physis.
Mechanism:
External rotation of the foot - avulsing the epiphyseal fragment laterally (by ATFL)
DDx:
- Triplane fracture: where an oblique projection may help to distinguish both
Rx:
- Accurate closed reduction.
Prognosis:
- Good with accurate closed reduction. Deformity happens more often when the insult occurs earlier in life, when the physis are still growing!
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