MSK - Odds & Ends Flashcards
Most important predisposing factors to patellar instability (3)
1) Femoral trochlear dysplasia
2) Patella alta
3) Lateralization of the tibial tuberosity
Which measurements can be used to measure femoral trochlear dysplasia?
1) Lateral trochlear inclination (<11 degrees)
2) Trochlear facet asymmetry (<40 percent)
3) Trochlear depth (<3 mm)
Normal signal intensity of red marrow on T1WI
40% fat in red marrow - appears slightly hyperintense compared to skeletal muscle and intervertebral discs.
May see mild enhancement post-contrast.
Pathologic processes replace normal fatty marrow with water (so appear bright on fluid sensitive sequences).
Describe the typical sequence of marrow conversion
Starts in epiphysis, then moves to diaphysis and progresses bidirectionally but faster distally so only remaining red marrow is in the proximal femurs, humeri and axial skeleton
Yellow to red conversion occurs in opposite direction.
Causes of red marrow hyperplasia
Hypoxemic states (impaired delivery, increased demand)
- anemia, sickle cell, thalessemia
- smoking
- cyanotic heart disease
- athletes
What is the flip-flop sign? and what condition is this commonly seen in
Diffuse, heterogenous replacement of normal fatty marrow so appears dark on T1 and bright on fluid-sensitive sequences.
- Seen in ALL
CRMO - common sites, findings on MRI, ddx
Sites: medial clavicle, metaphyses of long bones, spine, pelvis
MRI: active areas are T2 hyper and enhance, quiescent are dark on T1 and T2 (variable appearance on x-ray)
DDx: other multifocal processes - acute bacterial osteomyelitis, LCH, mets, primaries- Ewings, Lymphoma, Leukemia
FIndings in Erdheim Chester-Disease
Multi-systemic histiocytosis (non langerhans cell)
Bone pain most common presenting sx
Bilateral, symmetric metaphyseal and diaphyseal sclerosis, cortical thickening, increased uptake on bone scan
Hairy kidney sign (soft tissue infiltration in pararenal space)
Soft tissue encasing aorta - IVC and ureters spared
Findings of LCH in the lung
DDx. for bone infarcts
PLASTIC RAGS Pregnancy Lupus Alcohol Steroids Trauma Idiopathic, infection Collagen vascular disease Radiation Amyloid Gauchers Sickle Cell
DDx. Erlenmeyer flask deformity (undertubulation)
CHONG Craniometaphyseal dysplasia Hemoglobinopathy (thalassemia, sickle cell) Osteopetrosis, osteochondromatosis/HME Niemann-Pick disease Gauchers
DDx Diffuse Sclerosis
3 M'S PROOF Myelofibrosis Mastocytosis Malignancy (diffuse blastic mets) Sickle cell Paget's Renal osteodystrophy Osteopetrosis Other: osteopoikilosis, osteopathia striata, hyperthyroidism, normal variant (athletes) Fluorosis
Ddx Ivory vertebra
Osteoblastic mets (adult - prostate, breast, child - medulloblastoma, neuroblastoma) Paget's Lymphoma Chronic infection*** Hemangioma Children: add osteoblastoma
DDx expansile or lytic rib lesion
“FAME-B”
- Fibrous dysplasia
- ABC
- Mets/MM/Plasmacytoma
- Enchondroma
- Brown tumour
Most common cause of acquired flat foot
Posterior tibial tendon tear
Spring ligament also maintains arch of foot
Signs of talocalcaneal coalition & calcaneonavicular coaltion
- C sign, talar beak
2. Anteater sign
Haglund syndrome findings
- Insertional achilles tendinopathy
- Retrocalcaneal bursitis
- Haglund deformity
What structures make up the posterolateral corner?
LCL complex (LCL, biceps femoris, IT band)
Popliteus muscle
Popliteal fibular ligament
Arcuate ligament
What structures make up the rotator interval?
CHL, LHBT, SGHL (located between the supraspinatus and the subscapularis)
What structures make up biceps pulley?
CHL + SGHL + distal fibres of subscapularis
NB: CHL is the roof of the rotator interval, SGHL is the floor, biceps runs in the middle
Most important component of capsulolabral complex for stability during abduction/rotation
IGHL
What does TUBS stand for?
Traumatic, unidirectional, Bankart, surgical - a type of traumatic instability
What does AIOS stand for? AMBRI?
Acquired, instability, overstress, surgery - athletes, repetitive movements, microinstability
Atraumatic, multi-directional, bilateral, rehabilitation, inferior capsule shift - usu due to congenital joint laxity
Quadrilateral space margins?
Which structures travel through this?
What are imaging findings of syndrome?
Borders: HTTT Lateral humerus Medial long head of triceps Superior teres minor Inferior teres major
structures:
- axillary nerve
- posterior humeral circumflex artery
Imaging findings: isolated teres minor +/- deltoid atrophy
Imaging findings suprascapular nerve entrapment?
Atrophy of supra and infraspinatus muscles (often from paralabral cyst impinging on superior suprascapular nerve)
At the level of the spinoglenoid notch - will cause isolated atrophy of infraspinatus
What is Parsonage-Turner?
Idiopathic brachial neuritis (viral versus inflammatory)
Almost always involves the suprascapular nerve (uncommonly axillary and subscapular nerve involvement) - supra, infra, deltoid
Imaging - edema –> fatty replacement
R/o other entrapment neuropathies (look for paralabral cyst, mass etc.)
Most common type of carpal coalition
Lunotriquetral (#1)
Capitohamate (#2)
DDx dense metaphyseal bands
PRINCES Poisoning (heavy metals) Ricketts (healed) INfection (TORCH) Congenital (syphilis) Endocrine (hypothyroid) Scurvy, sickle cell
DDx for acro-osteolysis
PINCH FO
- psoriasis
- injury (thermal or frost bite)
- neuropathy (DM, leprosy)
- collagen vascular (scleroderma, reynauds)
- hyperPTH
- familial - Hadju-Cheney
- other - polyvinyl chloride
Findings in idiopathic tumoral calcinosis
Hereditary disorder of phosphate metabolism, causing massive periarticular calcification
Involves large joints (hip, elbow, shoulder, feet, but usually not knees)
Cloud like calcification around the joint
No erosive changes in bone
DDx: other causes of periarticular calcification - CTDs, hyperparathyroidism, HO, synovial osteochondromatosis
Ddx for diffuse periostitis
HOA (**lung Ca + other causes) Primary HOA (Pachydermoperiostitis) Vascular insufficiency Multifocal nodular periostitis (chronic voriconazole use) Thyroid acropachy (hands and feet)
Neuropathic joint findings
5 D’s = disorganization, debris, density, dislocation and joint distension (atrophic form: shoulder, knee, hip; well demarcated area of osseous resorption)
Causes of neuropathic joint
Central (i.e. shoulder) - Spinal cord tumour, syrinx, spina bifida, neurosyphilis (tabes dorsalis)
Peripheral (i.e. foot) - Diabetes**, nerve injury, leprosy, collagen vascular diseases
List the complications after arthroplasty
1) Aseptic loosening (most common reason for revision)
2) Infection
3) Particle disease (giant granulomatous reaction to cement particles, marked osteolysis)
4) Fracture
5) Dislocation
6) Malpositioning (creep - normal - central, polyethylene wear - eccentric)
7) Metal-on-metal (pseudotumour, ALVAL - this is on a spectrum with particle disease, more likely to have large fluid collection around joint)
What is FOP?
Fibrodysplasia ossificans progressiva (Munchmeyers disease) - MUMMY SYNDROME
- progressive fibrosis and ossification of muscles, tendons, fascia, ligaments starting in childhood
Location of peroneus quartus
Posterolateral ankle, adjacent to peroneus brevis and longus; frequently bilateral
Most common location meniscal ossicle
Posterior horn medial meniscus
Associated with posterior root tear
