MSK CATs Flashcards
Types of Disturbed fracture healing
Delayed union
- takes longer
Non-union (pseudoarthrosis)
- healing not occuring within 6-9 months
- common sites: scaphoid, femoral neck, tibial shaft
Malunion
- Healing in non-anatomical position
Refracturing
Causes of insufficiency fracture
Osteoporosis (most common)
Osteochondral injury staging system
Stage 3
- Detached but not displaced
- MRI shows high signal around the osteochondral fracture “rim sign” but not displaced
Stage 4
- fragment displaced
Stage 5
- subchondral cyst formation
mnemonic for causes of diffuse bony sclerosis is:
M: Myelofibrosis, Metastases, Lymphoma, Leukemia
S: Sickle cell disease
P: Pagets
R: Renal osteodystrophy
O: Osteopetrosis
F: Fluorosis
What is Primary myelofibrosis characterised by
extramedullary haematopoiesis
progressive splenomegaly
anaemia
variable change in the number of granulocytes and platelets including thrombocytopenia
Complications of Myelofibrosis
Gout: from hyperuricaemia due to increased haematopoietic turnover
Complications with splenomegaly
- infarction, rupture
- splenic vein thrombosis
- portal HTN
Bleeding due to thrombocytopenia
Thromboembolic event
- PE
- DVT
Stages of FICAT for AVN
Stage 2
- 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
Stage 3
- plain radiograph: crescent sign and eventual cortical collapse
- MRI: same as plain radiograph
Stage 4
- plain radiograph: end-stage with evidence of secondary degenerative change
- MRI: same as plain radiograph
Why femoral neck fracture prone to AVN?
Most of the femoral head blood supply is done by the extracapsular arterial ring, which is formed by the lateral femoral circumflex and the medial femoral circumflex arteries.
The femoral circumflex arteries arise from the deep femoral artery. Between them, the medial femoral circumflex artery supplies most of the blood to the head of the femur.
In cases of trauma proximal to the extracapsular arterial ring, such as femoral neck fractures, there is a considerable chance of avascular necrosis of the femoral head due to disruption of proper blood supply.
Which part of the bone is affected most by Bone Infarct and Why ?
Convex articular surfaces.
Because convex articular surfaces have smaller diameter of terminal vessels and the lack of collateral vascularisation**
Causes of Bone infarct ?
(Same causes as AVN)
- Trauma
- Sickle cell disease (rigid sickle cells leading to vaso-occlusive crises)
- vessel occlusion by nitrogen bubbles (caisson disease)
- Gaucher disease
Complications of Bone infarct ?
- MFH (most common)
- Osteogenic sarcoma
- Fibrosarcoma of bone
- Osteomyelitis
- Angiosarcoma of bone (super rare)
Nuclear medicine scan to do for bone infarct ?
Bone scan
- No uptake (photopenia) where blood supply absent
- Mildly increased uptake at periphery during acute phase
Define acute vs chronic osteomyelitis
Acute OM
- symptoms are present for <2 weeks
Chronic OM
- symptoms present for >4 weeks
Do cultures often yield positive for OM ?
No, low culture yields (only yield in ~35%). Often false-negative results
OM complications
- SCC (Marjolin ulcer)
- Osteosarcoma
- Pathological fracture
- Secondary Amyloidosis
Which of the following important features favours the diagnosis of osteomyelitis over neuropathic osteoarthropathy?
transcutaneous spread of disease — correct!
Explanation
>90% of cases of osteomyelitis spread through a transcutaneous route. Therefore, subcutaneous fat is usually involved.
Neuropathic osteoarthropathy is an aggressive form of degeneration therefore it is common to see subchondral cysts and bone erosions. It usually involves multiple joints with an articular epicenter. However, in osteomyelitis, there is a marrow epicenter.
How to diagnose early osteomyelitis in a diabetic foot with discordant bone marrow signal ?
A bone marrow to joint fluid signal intensity ratio of ≥53% on T2/STIR sequences
What is the most common location of osteomyelitis?
Lower limb
What are the 2 forms of Necrotizing fasciitis ?
Polymicrobial (Type 1)
- most common
- involves anaerob and aerobic organisms
- forms gas - due to anaerobes
Monomicrobial (Type 2)
- less common
- involves “Group A Strep” - flesh eating bacteria
- complicated by “Toxic shock syndrome”
- will not form gas, because group A strep dont form gas
Management of Necrotizing fasciitis
- Urgent surgical fasciotomy with aggressive debridement of the necrotic tissue
- Urgent empiric broad-spectrum antibiotics including anaerobic is recommended
Most common sites of septic arthritis in IV drug users ?
In intravenous drug users, the sternoclavicular and sacroiliac joints are more frequently affected.
Risk factors for septic arthritis
- Advanced age
- Bacteremia
- Sexually active
- Immunocompromised
- Rheumatoid arthritis
- Prosthetic joints
- Intraarticular injections
Ankylosing spondylitis associations
- Uveitis
- IBD
- Interstitial lung disease
- Psoriasis
- Cauda equina syndrome
DISH associations ?
- OPLL (accompanies around 50% of cervical DISH cases)
- Metabolic syndrome, obesity and diabetes mellitus
- Ossification of the stylohyoid ligament and Eagle syndrome
Ankylosing spondylitis genetics ?
HLA-B27 (+)
RF (-)
What are the 2 forms of Neuropathic arthropathy ?
- Atrophic
- most common
- acute progression
- No osteophytes
- Resorptive - Hypertrophic
- slow progression
- have osteophytes
- Fragmentations/Debris
- No osteoporosis
Neuropathic arthropathy causes for:
- foot and ankle
- shoulder
- hips
- knee
- spine
Foot / ankle
- Diabetes
Shoulder
- Syringomyelia
Hip
- Alcoholism, tabes dorsalis
Knee
- Neurosyphilis / Tabes dorsalis
Spine
- Trauma
Useful MRI features that support superimposed osteomyelitis on a Charcot joint include:
Sinus tract
Diffuse marrow signal abnormality
Replacement of soft tissue fat*
Thick rim enhancement
Joint erosion
Ghost sign (poor definition of the margins of a bone on non-contrast T1)
Aetiology of Pagets disease
- Paramyxovirus
- Disease of Osteoclasts
Markers of Pagets disease
Increased ALP
Increased Hydroxyproline
Normal Calcium
Findings of Renal osteodystrophy
- Osteomalacia (adults) or rickets (children)
- Secondary hyperparathyroidism: abnormal calcium and phosphate metabolism
- subperiosteal resorption
- bone sclerosis: rugger jersey
- brown tumours
- salt and pepper skull
- soft tissue calcifications
- looser zones insufficiency fracture
Causes of gout
Under secretion
- CKD
- Hyperparathyroidism
Overproduction
- Myeloproliferative disorder
- Hemolysis
Complication of HADD
When intra-articular, calcium apatite crystals can cause joint destruction. Any joint can be involved; the shoulder is most commonly affected, resulting in Milwaukee shoulder
Causes of CPPD
Idiopathic
Hereditary: AD with ANKH gene
Secondary:
- hemochromatosis
- hyperparathyroidism
- hypothyroidism
- hypermagnesaemia
Transient osteoporosis of the hip (TRO Transient regional osteoporosis) seen more commonly in what demographic ?
- Higher incidence during third trimester of pregnancy
- But still more common in man (M:F ratio 3:1)
Transient osteoporosis of the hip features (TRO Transient regional osteoporosis)
- Femoral head marrow oedema without features of AVN
- Indistinctiveness of the femoral head cortex (virtually pathognomonic; present in only 20% of cases after 4-8 weeks from symptom onset)
- Osteopenia of the femoral head and neck region (late)
- Joint effusion may be present
- Joint space always preserved
Transient osteoporosis of the hip if bilateral or if it migrates then its called ?
Regional migratory osteoporosis
Which is NOT a typical MRI feature of myositis ossificans at 4 weeks after suspected inciting trauma?
During the active phase, myositis ossificans is associated with prominent surrounding muscular oedema which can be a useful sign (in addition to peripheral calcification and history of trauma) in confidently differentiating it from sarcomas, which typically induce very little if any surrounding oedema.
What are the 3 types of osteochondromatosis ?
Para-articular Chondroma (intracapsular chondroma)
- most common in Hoffa’s fatpad of knee
- if seen calcifications (then cannot be PVNS)
Synovial osteochondromatosis
- appear as multiple intra-articular nodules in contrast to the solitary lesion of para-articular chondroma
- contains synovial cells
- It must be remembered that, in a minority of cases, the bodies in SC are not calcified enough to be visible on radiographs.
Soft tissue osteochondromatosis
Inheritance of Maffuci’s and Ollier’s
Sporadic*
Ollier and Maffuci associations ?
- Chondrosarcoma
- Pancreatic and Juvenille granulosa cell tumor of the ovary
- Gliomas
Ollier + osteochondromas =
metachondromatosis.
Clinical signs of malignant transformation of Ollier and Maffuci
- if pain occurs when child is OLDER (pain is normal during periods of rapid growth)
- Pathological fracture also present with pain
Management of Maffuci and Ollier
If extensive involvement, it might cause growth impairment, deformity (such as leg length discrepancy or Madelung deformity of the forearm), and functional impairment and these may require corrective surgery.
Maffucci syndrome genetic mutation ?
IDH1 or IDH2
Location and distribution of Maffuci / Ollier
Phalanges of Hands and Feet
Bilaterally Asymmetrical
Chondrosarcoma subtypes
- Conventional
- Clear cell
- Mesenchymal
- Dedifferentiated
Chondrosarcoma associated with
- Hyperglycemia due to paraneoplastic syndrome
- Hereditary Multiple Exostosis
- Ollier
- Maffucci
Chondrosarcoma management
- Usually surgery, unless it’s Mesenchymal type, then Chemo + Radiation therapy*
Fibrous Dysplasia genetic mutation
GNAS
Non-Ossifying fibroma most common location ?
metaphyses of long bones.
- giant cell rich bone tumours
Non-ossifying fibroma associations
NF-1
Jaffe Campanacii syndrome
Macrodystrophia lipomatosa pathology
- Can be thought of as lipomatosis of nerve resulting in visible deformity.
- Considered a progressive form of macrodactyly growth halts at puberty
Macrodystrophia lipomatosa associations
syndactyly
clinodactyly
polydactyly
Lipoma arborescens location
- affecting synovial linings of the joints and bursae
- can be seen in the setting of osteoarthritis, collagen vascular disorders, or previous traum
Lipoma arborescens associated findings
- Joint effusion (very common)
- Degenerative change (common)
- Meniscal tears (common)
- Synovial cysts (uncommon)
Types of liposarcoma ?
- Well differentiated (most common)
- De-differentiated
- Myxoid liposarcoma
- Pleomorphic liposarcoma
- Mixed liposarcoma
Prognosis of Liposarcoma in extremity vs retroperitoneum
Extremity (most common)
- indolent
- lower rate of recurrence
- better prognosis
Retroperitoneum (less common)
- high rate of recurrence
- tend to be high grade
Osteoid osteoma composition
Lucent Nidus
- represents neoplastic process
- releases prostaglandins (via the enzymes cyclo-oxygenase-1 and cyclo-oxygenase-2), resulting in pain
Fibrovascular rim
Surrounding reactive sclerosis
Osteoid osteoma treatment
- Radiofrequency ablation
Why is Aspirin contraindicated in Osteoid osteoma in children?
Aspirin is contraindicated in children <12 years old due to risk of Reye syndrome
When osteoid osteoma intra-capsular, what can it mimic ?
When intracapsular, the presentation is more atypical and more likely to mimic inflammatory arthropathy or synovitis.
Joint effusion is often present
When osteoid osteoma/osteoblastoma in spine, what does it cause ?
Classic cause of painful scoliosis
Complications of Osteoblastoma intra-operatively
Lesions are prone to extensive intraoperative bleeding due to intrinsic vascularity
Primary vs Secondary osteochondromatosis
Primary synovial chondromatosis:
- Predominantly monoarticular disorder of unknown aetiology
Secondary synovial chondromatosis:
- Intra-articular loose bodies from Trauma, osteoarthrosis and neuropathic arthropathy*
- Large nodules vary in size vs small and uniform size in primary
What are the 3 phases of Primary osteochomdromatosis
Initial phase: metaplastic formation of cartilaginous nodules in the synovium
Transitional phase: detachment of those nodules and formation of free intra-articular bodies
Inactive phase: resolution of synovial proliferation, but loose bodies remain in the joint, and may increase in size obtaining nourishment from the joint fluid by diffusion
Diagnostic criteria for Hereditary Multiple Exostosis ?
essential: ≥2 radiological osteochondromas at the juxtaepiphyseal region of the long bones and positive family history and/or EXT gene germline mutation
Complications of Hereditary Multiple Exostosis ?
vascular impingement
neural impingement
fracture
bursitis
deformity and ankylosis
malignant transformation
Features of osteochondroma malignant (sarcomatous) transformation
more common than in sporadic cases*
G: growth after skeletal maturity
L: lucency (new)
A: additional scintigraphic activity
D: destruction (cortical)
P: pain after puberty
a: and
S: soft tissue mass
T: thickened cartilage cap >1.5 cm
How to approach planning to biopsy a potential sarcoma
The treating surgeon should be consulted to plan the biopsy track as this will require excision to reduce the chance of seeding. A poorly planned track that crosses compartments can result in a more extensive resection, potentially with poor outcomes for the patient.
Complication of parosteal osteosarcoma
Might progress to a high-grade sarcoma including other osteosarcoma variants, undifferentiated spindle cell sarcoma or rhabdomyosarcoma
Rhabdomyosarcoma 3 types
embryonal rhabdomyosarcoma (most common)
alveolar rhabdomyosarcoma: 20%
pleomorphic rhabdomyosarcoma: 5%
Rhabdomyosarcoma (RMS) is a malignant tumour with skeletal muscle cell morphology. It is one of the tumours of muscular origin.
What type of tumour is Ewing sarcoma ?
- Small round blue cell tumor
Ewing sarcoma closely related to what other tumours
- pNET
- Askin tumour
- Neuroepithelioma
All referred to as Ewing sarcoma family of tumors
Ewing sarcoma labs ?
ESR and serum LDH levels are elevated
Imaging features on MRI to differentiate giant cell tumor from aneurysmal bone cyst ?
Enhancing solid components can help to distinguish giant cell tumours with haemorrhagic areas and aneurysmal bone cyst-like changes from a pure aneurysmal bone cyst.
What is a useful nuclear study scan to do for Giant cell tumor, Aneurysmal bone cyst and Simple bone cyst (cystic lesions)
On bone scintigraphy, most giant cell tumours demonstrate increased uptake on delayed images, especially around the periphery, with a central photopenia (doughnut sign).
Increased blood pool activity is also seen, and can be seen in adjacent bones due to generalised regional hyperaemia (contiguous bone activity).
Treatment of benign metastasizing GCT / unresectable disease ?
Denosumab
inferior shoulder dislocation caused by?
- Sudden forceful hyperabduction
- Direct force on an abducted arm
- Humeral head forced against the acromion, leading to inferior glenohumeral capsule rupture and rotator cuff disruption
What injuries are SLAP tears associated with ?
- Bankart lesion (in young patient <40)
- Rotator cuff injury (in older patient >40)
SLAP tears vs ALPSA and Bankart
Unlike Bankart lesions and ALPSA lesions, they are uncommonly (20%) associated with shoulder instability
What is a Perthes lesion ?
One of the types of anterior glenohumeral injury in which the anterior inferior labrum is torn and lifted from the edge of the glenoid but still attached to the intact lifted periosteum from the anterior aspect of the glenoid.
Although the labrum may be normally positioned, functionally it no longer provides any stability to the humeral head, mainly as a result of impairment of the normal stabilising influence of the “inferior glenohumeral ligament”
What is Glenolabral articular disruption (GLAD) lesion ?
Superficial anterior inferior labral tear + anterior inferior glenoid articular cartilage injury.
Not tend to associate with “shoulder instability”*
What positoin can help visualize labral tears better on MR arthrography ?
ABER
- ABduction and External Rotation.
What is anterior labroligamentous periosteal sleeve avulsion (ALPSA) lesion ?
similar to a Bankart lesion, in that it too is usually due to anterior shoulder dislocation and involves the anterior inferior labrum.
- Detachment of the anteroinferior labrum + labrum remains attached to the periosteum
(Bankart lesion in which the labrum and glenoid periosteum are avulsed from the underlying glenoid)
Where is the cirtical zone of rotator cuff tear ?
8-20 mm proximal of the insertion site.
Indirect signs of Full-thickness tear
Subdeltoid bursal effusion, medial dislocation of biceps, fluid along biceps tendon, and diffuse loss of peribursal fat planes.
Muscle atrophy and fatty replacement is seen in chronic cases and can be graded using the Goutallier classification, or assessed with the tangent sign or scapular ratio
Supraspinatus tear associations (same as infraspinatus tear)
- posterosuperior tear extension into the infraspinatus tendon and muscle and the rotator interval
- ACJ osteoarthritis
- Proximal biceps tendon injury
- SLAP lesion
Full thickness tear of the supraspinatus tendon will lead to loss of what function
- Shoulder abduction
What are the Three patterns of subscapularis tendon tears
- Supraspinatus tear involvement (80%)
- “Rotator cuff interval” extension: Potentially involving the “superior glenohumeral ligament (SGHL)” and “coracohumeral ligament (CHL)” and can lead to “biceps instability”, especially when superior tears are present.
- Isolated (rare): most commonly traumatic in the setting of anterior glenohumeral instability
**almost always (>90%) start as articular-sided partial-thickness tears superomedially and progress inferolaterally
**entire tendon can be torn but the overlying superficial fascia and transverse humeral ligament can be intact
Subscapularis tear associations
Subcoracoid impingement (narrowing of the coracohumeral interval (space between the tip of the coracoid and the humerus)
SLAP tears in the context of biceps pulley injury
What are some signs of subscapularis tear
comma sign: full-thickness superior subscapularis tears along with SGHL and CHL tears retracted superiorly
axial plane: long head of biceps (LHB) tendon subluxation
sagittal oblique plane: subscapularis muscle belly atrophy
lesser tuberosity bone marrow oedema and cysts especially when combined with muscle belly fatty atrophy is indicative of chronic tears.
if the LHB is normally positioned in the bicipital groove (i.e. not subluxed), there is a low likelihood of a full-thickness subscapularis tear**
What are the types of Shoulder impingement ?
subacromial impingement: most common
- os acromiale
- type 3 acromium
- osteophytes
subcoracoid impingement: affects subscapularis, long head of biceps
- reduced coraco-humeral interval due to trauma or prior rotator cuff repair*
posterosuperior impingement: involves infraspinatus (rare)
- occurs when the shoulder is abducted and externally rotated (ABER position).
Complications of subacromial impingement ?
rotator cuff tear
subacromial bursitis
biceps tendinopathy
What structures do lateral epicondylitis affect (tennis elbow) ?
overuse syndrome of the common extensor tendon and predominantly affects the extensor carpi radialis brevis (ECRB) tendon.
- best clue for the diagnosis of lateral epicondylitis is abnormal thickening and increased signal intensity within the common extensor origin from the lateral epicondyle
- associated radial nerve entrapment may occur in 5% of cases
Complications of Scaphoid fracture
Osteonecrosis (Most common)
- proximal portion due to arterial supply entering distally
SNAC wrist
- Scaphoid non-union advanced collapse
- proximal fragment remains at the lunate while the distal fragment begins to rotate into flexion creating abnormal contact in the radio-scaphoid compartment that will progressively get worse.
SLAC wrist
- Scapholunate advanced collapse
- widening of the scapholunate interval, over time, this leads to increase load over the radial aspect of the radioscaphoid joint causing osteoarthritic changes.
- capitate to migrate proximally and ultimately cause degeneration of the capitulate joint and further displacement of the lunate ulnarward
Delayed union
Bennett fracture
Epibasal fracture
Rolando fracture
Reverse Bennett fracture-dislocation
Boxer fractures
Bennett
- Base of 1st MC fracture
- intra-articular
- 2 piece
Epibasal fracture
- extra-articular fractures through the first metacarpal base
Rolando fracture
- comminuted intra-articular fracture through the first metacarpal base
Reverse Bennett fracture-dislocatoin
- fracture-dislocation of the base of the 5th metacarpal bone. It is pathologically and radiographically analogous to the Bennett fracture of the thumb.
Boxer fracture
- minimally comminuted, transverse fractures of the 5th metacarpal neck
Perilunate dislocation + Scaphoid fracture = ?
Trans-scaphoid perilunate dislocation
Perilunate dislocation injures what structures
- Radioscaphocapitat ligament
- Scapholunate interosseous ligament
- Lunotriquetral interosseous ligament
Describe midcarpal dislocation
A dislocation where neither the capitate or the lunate is aligned with the distal radius.
What is the classification used for carpal instability ?
Mayfield classification of carpal instability:
Stage I: scapholunate dissociation (rotatory subluxation of the scaphoid)
- disruption of the scapholunate ligament with resultant Terry Thomas sign
- exacerbated on clenched-fist views
- associated with DISI and VISI
stage II: perilunate dislocation
- the lunate remains normally aligned with the distal radius, and the remaining carpal bones are dislocated (almost always dorsally)
- the capitolunate joint is disrupted, and the lunate projects through the space of Poirier
- 60% are associated with scaphoid fractures
stage III: midcarpal dislocation
- lunotriquetral interosseous ligament disruption or triquetral fracture*
- neither the capitate or the lunate is aligned with the distal radius
stage IV: lunate dislocation
- dorsal radiolunate ligament injury*
- dislocation of the lunate in a palmar direction
- tipped teacup appearance
Madelung deformity associations
- Turner syndrome
- Hereditary multiple exostosis
- Ollier disease
- Achondroplasia
Ulnar impaction syndrome and its association
Painful degenerative wrist condition caused by the ulnar head impacting upon the ulnar-sided carpus (lunate) with the injury to the triangular fibrocartilage complex (TFCC).
- majority of cases occur in association with positive ulnar variance
Ulnar impingement syndrome and its association
- caused by a shortened distal ulna impinging on the distal radius proximal to the sigmoid notch.
- results in contraction of the extensor pollicis brevis, abductor pollicis longus, and pronator quadratus muscles which prevents normal buttressing of the radioulnar joint
- Most commonly, the syndrome is caused by surgical resection of the distal ulna as part of the management of wrist trauma, rheumatoid arthritis, or Madelung deformity. Less commonly, ulnar impingement may occur in de novo negative ulnar variance.
Scapholunate dissociation injured ligaments ?
scapholunate interosseous ligament (SLIL):
- Dorsal (strongest, most important)
- Intermediate
- Volar
scapholunate interval >3 mm on PA view
When does TFCC injury require surgery
- medial tears are in the vascularised zone and a surgical repair is a treatment option whereas central tears are in the avascular zone and are typically debrided
- TFCC degenerations are intrinsically high signal not extending to the articular surface
MRI wrist arthrogam, how to tell if TFCC injury ?
The injected wrist joint capsule and distal radioulnar joint (DRUJ) only communicate if there is a tear in the triangular fibrocartilage complex (TFCC).
As shown, contrasts opacifies the DRUJ, indicating a TFCC tear.
Mallet finger ?
Avulsion of the Common extensor tendon on the dorsal aspect of the distal phalanx at the DIP joint.
Due to sudden hyperflexion
Mallet finger complications
- Dorsal skin ulcer
- Nail deformity
- Swan neck deformity
- Secondary osteoarthritis
Jersey finger ?
Avulsion of the flexor digitorum profundus (FDP) from the volar aspect of the distal phalanx base
Due to sudden hyperextension