MSK Flashcards
MSK
A 33-year-old man with short stature and normal intelligence is being investigated for lower back pain. MRI of the thoracolumbar spine shows marked central stenosis with short pedicles. A comment of bullet-shaped vertebra with progressive narrowing of the lumbar interpedicular distance was noted on the report. Which of the following conditions is most likely?
A. Hurler’s syndrome
B. Congenital pituitary dwarfism
C. Achondroplasia
D. Thanatophoric dysplasia
E. Hunter’s syndrome
C. Achondroplasia
Spinal stenosis from congenital short pedicles along with reducing interpedicular distance towards the lumbar spine is a classic finding of achondroplasia.
Other associated findings include the ‘champagne glass pelvis’, bullet-shaped vertebra (cf. central vertebral beaking in Morquio syndrome and inferior vertebral beaking in Hurler’s and Hunter’s syndromes), trident hand and craniocervical stenosis from a small foramen magnum.
Platyspondyly, loss of vertebral height, specially affecting lumbar vertebra by 2–3 years of age, is a typical feature of Morquio syndrome (cf. vertebral height is normal in Hurler’s syndrome).
MSK
Regarding sporting injuries involving the upper limbs, all of the following statements are correct, except:
A. Anomalous anconeus epitrochlearis muscle results in Posterior Interosseous Nerve (PIN)entrapment.
B. Atrophy of extensor muscles can be seen in chronic PIN neuropathy.
C. Partial thickness tears of the biceps can involve either the long or short heads.
D. Cubital tunnel syndrome is the most common elbow neuropathy.
E. Oedema of flexor carpi ulnaris and ulnar nerve thickening suggests cubital tunnel nerve entrapment.
A. Anomalous anconeus epitrochlearis muscle results in PIN entrapment
Cubital tunnel syndrome is the most common entrapment neuropathy of the elbow. It is seen in throwing sports, tennis and volleyball. Traction injuries to the ulnar nerve can occur secondary to the dynamic valgus forces. Compression of the ulnar nerve within the cubital tunnel occur secondary to direct trauma, repetitive stresses, or replacement of the overlying retinaculum with an anomalous anconeus epitrochlearis muscle. Recurrent subluxation of the nerve due to acquired laxity from repetitive stress or trauma can lead to friction neuritis. Finally, osseous spurring within the ulnar groove caused by overuse and posteromedial impingement in throwers can cause nerve irritation. Ulnar nerve thickening and increased T2-weighted signal are typical MRI features. Oedema-like signal changes or atrophy of the flexor carpi ulnaris and flexor digitorum profundus muscles may also be secondary to ulnar neuropathy.
Radial nerve entrapment at the elbow can be subdivided into two major categories: radial tunnel syndrome and posterior interosseous nerve syndrome.
The posterior interosseous nerve is a deep branch of the radial nerve in the forearm that can be compressed from repetitive gripping combined with supination in weight lifters and swimmers.
The superficial head of the supinator muscle along the arcade of Frohse is the most common site of nerve entrapment. It is important to note that a small percentage of radial neuropathy cases can be associated with tennis elbow. MRI manifestations of PIN includes thickening and increased T2-weighted signal of the nerve fibres, as well as oedema-like signal changes in the innervated extensor compartment musculature in the acute and subacute setting and atrophy in the chronic stages.
MSK
An 11-year-old boy with left shoulder pain has a shoulder X-ray, which shows a lucent lesion in the metaphysis. This has distinct borders and lies in the intramedullary compartment. It is orientated along the long axis of the humerus. What is the most likely diagnosis?
A. Aneurysmal bone cyst
B. GCT
C. Simple bone cyst
D. Chondroblastoma
E. Non-ossifying fibroma
C. Simple bone cyst
SBC affects the young, aged 3–19 years, during the active phase of bone growth and has a slight male preponderance (M:F = 3:1). They are asymptomatic, unless fractured. They are commonly seen in the proximal femur or proximal humerus. They are solitary intramedullary lesions, centred at the metaphyses, adjacent to the epiphyseal cartilage (during the active phase) and migrating into diaphysis with growth (during the latent phase). They do not cross the epiphyseal plate. On a radiograph, they appear as an oval radiolucency with a long axis parallel to the long axis of the host bone, a fine sclerotic boundary and scalloping of the internal aspect of the underlying cortex. SBC appears as a photopenic area on a bone scan (if not fractured). Classic ‘fallen fragment’ sign if fractured (20%); centrally dislodged fragment falls into a dependent position.
MSK
An elderly patient on long-term dialysis presents to the orthopaedic clinic with right shoulder pain. Plain films show juxta-articular swelling and erosions of the humerus, but the joint space is preserved. MRI shows a small joint effusion and the presence of low- to intermediate-signal soft tissue on all sequences covering the synovial membrane extending into the periarticular tissue. What is the likely diagnosis?
A. Amyloid arthropathy
B. Gout
C. Calcium pyrophosphate deposition disease (CPPD)
D. Pigmented villonodular synovitis (PVNS)
E. Reticulo-endotheliosis
A. Amyloid arthropathy
Amyloid arthropathy most typically affects the shoulders, carpal bones and hips in a bilateral fashion. It is typically associated with long-term renal dialysis, which results in deposition of thebeta-2 microglobulin. Affected joints demonstrate subchondral cystic lesions with juxta-articular swelling. The presence of low-to-intermediate signal soft tissue within and around the joint clinches the diagnosis, as this represents the signal characteristics of the deposited proteins (cf. other inflammatory/infectious arthropathies, which tend to produce higher water content than soft-tissue changes in the joint). Joint space is also typically preserved until the late stages of disease, similar to gout.
MSK
A 14-year-old boy complains of left knee pain and limp. He also has medial thigh pain. On examination, he has full range of movement with some discomfort on internal rotation. AP and lateral X-rays of the knee and femur are normal. What is the next investigation?
A. CT
B. Bone scan
C. MRI
D. Frog leg lateral of the hips
E. US
D. Frog-leg lateral of the hips
Diagnosis of SUFE (slipped upper femoral epiphysis) is made using anteroposterior (AP) pelvis and lateral frog-leg radiographs. CT is rarely needed, although it is very sensitive. MRI depicts the slippage earliest, and MRI can demonstrate early marrow oedema and slippage. It is also useful in identifying pre-slip changes in the opposite hip and shows differentials, for example, infection, tumour, synovitis and so on.
Although some institutions obtain a frog-leg lateral view, it is possible to further displace an acute or acute-on-chronic slip when the hips are placed in this position. Thus some institutions avoid them unless the request comes from an orthopaedic surgeon. Phraseology is important in all investigation-related questions; while the next investigation is frog-leg lateral in several/most places, the best investigation or the most appropriate examination would be MRI because it will provide the most information and cover all differentials.
MSK
An eccentric expansile lesion in the metaphysis of the humerus is noted incidentally following a routine plain radiograph investigation in a young patient following a rugby tackle. MRI performed for further characterization shows multiple cystic spaces, some with blood fluid level, with an intact low-signal periosteal rim. What is the diagnosis?
A. Unicameral bone cyst
B. Aneurysmal bone cyst
C. Eosinophilic granuloma
D. Enchondroma
E. Fibrous dysplasia
B. Aneurysmal bone cyst
Aneurysmal bone cysts or ABCs are most commonly seen between the first and third decades of life. They are typically a metaphyseal lesion and are often located in the humerus, femur, or tibia. The presence of fluid–fluid levels along with bone expansion, a narrow zone of transition and metaphyseal location in a long bone is characteristic. Note that fluid–fluid levels can also be found in giant cell tumours, telangiectatic osteosarcomas and simple bone cysts, but the other associated locations and characteristics of the lesion would tend to be different from an ABC. Eosinophilic granulomas are associated with Langerhans cell histiocytosis. Enchondromas are typically located in the small long bones of the hands and in the proximal humerus and femur with non-expansile characteristics. Fluid–fluid levels are not typically associated with fibrous dysplasia, which takes on the commonly described ‘ground glass’ appearance.
MSK
A 31-year-old man who is known to the gastroenterologist and rheumatologist presents to the ophthalmology department with visual disturbances. A pelvic radiograph done a year ago in the emergency department showed whiskering of the ischial tuberosities and greater trochanters, with symmetrical sclerosis of both sacroiliac joints. What is the most
likely diagnosis?
A. Reiter syndrome
B. Behcet’s syndrome
C. Ankylosing spondylitis (AS)
D. Rheumatoid arthritis
E. Systemic lupus erythematosus (SLE)
C. Ankylosing spondylitis (AS)
AS is characterised by the hallmark of bilateral and symmetrical sacroiliac joint involvement, though there may be unilateral involvement in the early stages of disease. Other common findings include periostitis with whiskering of the pelvic bones and the typical ‘bamboo’ spine appearance from syndesmophyte formation. Up to 10% of AS cases are associated with inflammatory bowel disease, and iritis is common in up to 40% of patients. Ninety-six percent of patients are HLA-B 27 positive, the antigen associated with the other seronegative spondyloarthropathies of psoriasis, Reiter’s syndrome and inflammatory bowel disease-associated spondyloarthritis.
Behcet’s syndrome affects the chest and gastrointestinal tracts and doesn’t involve the skeleton primarily.
MSK
An elderly woman presents with progressive atraumatic pain within her right knee over the course of the last month, particularly on the medial aspect, associated with functional impairment. Her clinical history includes a meniscal tear, which was treated arthroscopically 10 years ago with a good outcome. An MRI reveals florid marrow oedema within the medial femoral condyle associated with mild flattening of the weight-bearing surface.
What is the diagnosis?
A. Perthe’s disease
B. Sinding Larsen’s disease
C. Blount’s disease
D. Spontaneous osteonecrosis of the knee
E. Osteochondral defect
D. Spontaneous osteonecrosis of the knee
Spontaneous osteonecrosis of the knee (SONK) is a rapid and painful condition in elderly patients that ultimately results in subchondral collapse of the weight-bearing portion of the medial femoral condyle. It is often idiopathic but can be associated with minor trauma. It is now also increasingly recognized as a subchondral insufficiency fracture resulting in rapid secondary’ subchondral collapse. Perthes disease is a childhood disease with avascular necrosis of the femoral head. Sinding-Larsen disease is essentially tendinosis of the proximal origin of the patella tendon. Blount’s disease is a growth disorder of the tibia resulting in a ‘bow leg’ deformity from disturbance to the medial proximal tibial epiphysis. An osteochondral defect is a traumatic injury involving the articular cartilage and adjacent subchondral bone.
MSK
A 10 x 7 mm dense ossified focal lesion is noted in the neck of the right femur of a young man incidentally on a pelvic radiograph performed for an unrelated reason. The lesion has benign features and is consistent with a bone island (enostosis). No follow-up is suggested. All of the following are true of bone islands, except
A. If more than 2 cm, they are classified as a giant’ bone island.
B. They have a sclerotic appearance on imaging.
C. They show a characteristic brush border on plain films.
D. They can be positive on a bone scan.
E. Giant bone islands can be locally aggressive.
E. Giant bone islands can be locally aggressive
Bone islands arc benign entities and represent compact bone within the medullary space.
They do not exhibit aggressive features regardless of size. Classically they are sharply defined with thorny radiations (brush border). Then can occasionally show increase or decrease in size (about a third of them) (cf. osteoblastic metastasis, which shows aggressive features, cortical break/destruction, periosteal reaction or soft-tissue component; osteoid osteoma is associated with typical pain and a nidus).
MSK
A 53-year old woman presents to the A&E department with acute knee pain. She has had two previous similar episodes in the past, which settled with analgesics and anti-inflammatory medications. Plain films show extensive degenerative change, which is worst at the patellofemoral joint with large subchondral cystic change and chondrocalcinosis of the knee menisci. She informs the attending doctor that she is under review with the endocrinologist. What is the likely diagnosis?
A. Calcium pyrophosphate deposition disease (CPPD)
B. Gout
C. Rheumatoid arthritis
D. Ochronosis
E. Psoriasis
A. Calcium pyrophosphate deposition disease (CPPD)
This is a typical description of CPPD, which can be idiopathic or associated with endocrinological problems such as hyperparathyroidism and hypothyroidism. The joints of the knee, wrist and second/third MCP joints of the hand are most frequently involved. Differentials would also include gout, but the distribution of erosions are different, with gouty erosions tending to be juxta-articular and punched out (‘rat-bitten’) rather than subchondral. Joint space is also typically preserved in gout until the late stages. Psoriasis produces enthesitis and periostitis
with new bone formation. Ochronosis, or alkaptonuria, is a metabolic disorder whereby there is abnormal build-up of homogentisic acid in connective tissue with pigmentation of the sclera and urine appearing dark in colour. Diffuse multilevel vertebral disc calcification and early OA changes in multiple joints are associated with this condition.
MSK
A 7-year-old boy with a history of a penetrating injury from a tree branch was sent for CT orbits for further assessment. Which of the following statements regarding the CT detection of intra-orbital foreign bodies is false?
A. Size, type and location of glass foreign body (FB) affects detection.
B. Wooden FB is hyperattenuating.
C. Old wood can be mistaken for air.
D. Attenuation of wood changes with water content.
E. CT can demonstrate metal FB less than a milli-metre.
B. Wooden FB is hyperattenuating.
CT is a very sensitive imaging modality that can demonstrate metal fragments less than 1 mm in size. Non-metallic foreign bodies are more problematic; not only the size of the glass fragment but also the type of glass and its location affect detection rates. Wooden foreign bodies usually appear hypoattenuating on CT images. Because of their low attenuation, they can be mistaken for air. If the low-attenuation collection on CT displays a geometric margin, wood or organic FB should be suspected. The attenuation of wood changes
MSK
A 56 year-old woman known to the endocrinologist has been going to her family doctor with a funny sensation in her right hand and fingers for the last few months. An MRI was organized along with nerve conduction studies by her family doctor. MRI revealed fusiform swelling of the median nerve in the distal forearm just before the entrance into the carpal tunnel with increased signal on T2. What is the likely diagnosis?
A. Cervical spondylosis
B. Ulnar tunnel syndrome
C. Carpal tunnel syndrome
D. Cervical rib with brachial plexus impingement
E. Neurofibroma of the median nerve
C. Carpal tunnel syndrome
Imaging of carpal tunnel syndrome is controversial and diagnosis is primarily made on clinical grounds and nerve conduction studies. However, there are some imaging findings that can be associated with the syndrome. These include the pseudo-neuroma’ appearance of the median nerve (swelling of the median nerve just before the carpal tunnel entrance), increased T2 signal changes and increased post-contrast enhancement. It is associated with acromegaly. Neurofibroma of the median nerve can account for the symptoms but would tend to be more distinct as a lesion and sometimes associated with a low-signal central region.
MSK
A 17-year-old teenager is under investigation for vague pain in the knee associated with a limp. A plain film radiograph shows an oval lucent lesion in the epiphysis of the distal femur. The pain was noticed following an injury sustained during a football match. What would be the next investigation of choice?
A. CT
B. MRI
C. Bone biopsy
D. Tc-99m bone scan
E. No imaging necessary since it looks benign
B. MRI
A main differential for a symptomatic lesion in the epiphysis of a long bone in an unfused skeleton is a chondroblastoma. MRI will reveal the presence of marked reactive surrounding marrow’ oedema. In a fused skeleton, the differentials would include clear cell chondrosarcoma, giant cell tumours and other benign causes like subarticular cyst and intraosseous ganglion.
Chondroblastomas are very well defined with sclerotic margin on plain X-ray and low-signal rim on MRI (cf. Langerhans cell histiocytosis, which appears less well defined with variable margins). Often definitive diagnosis requires surgical biopsy.
MSK
A plain lumbar spine radiograph of a 45-year-old woman shows marked posterior scalloping of the vertebral bodies extending over several vertebral lengths. All of the following are diseases associated with this finding, except
A. Marfan
B. Neurofibromatosis
C. Ependymoma
D. Achondroplasia
E. Hypothyroidism
E. Hypothyroidism
A common cause of localised posterior vertebral scalloping is increased intraspinal pressure secondary to an expanding mass. Widening of the interpediculate distance and alteration of the configuration of the pedicles are associated signs. Relatively large, slow-growing lesions that originate during a period of active skeletal growth (such as ependymomas) are most likely to give rise to posterior vertebral scalloping. Dural ectasia is thought to cause posterior vertebral scalloping due to loss of the normal protection provided to the vertebral body by a strong, intact dura. Dural ectasia classically occurs in association with inherited connective-tissue disorders such as Marfan syndrome (classical) and Ehlers-Danlos syndrome. Posterior vertebral scalloping is also commonly seen in patients with neurofibromatosis, most likely due to dural ectasia but also secondary to neurofibromas or a thoracic meningocoele. It has also been reported in patients with AS; in these cases, the development of associated arachnoid cysts may give rise to cauda equina syndrome. Acromegaly has been described as a further cause of diffuse posterior vertebral scalloping, probably because of a combination of soft-tissue hypertrophy in the spinal canal and increased bone resorption.
MSK
A young patient is followed up for a fractured tibia at the outpatient clinic. A repeat radiograph is acquired, which shows abnormal healing and callus formation at the fracture site. All the following are possible causes, except
A. Cushing’s syndrome
B. Osteogenesis imperfecta
C. Osteopoikilosis
D. Paralytic state
E. Asthmatic on steroids
C. Osteopoikilosis
Patients with co-morbidities like diabetes, anaemia and malnutrition can suffer from impaired bone fracture healing. Drug therapy like corticosteroids and NSAlDs can also produce similar problems. Osteogenesis imperfecta is a connective-tissue disorder with resultant abnormal bone density and structure, resulting in poor mineralisation and fragile, brittle bones. Osteopoikilosis is a benign condition and usually found incidentally. It is a form of sclerosing bone dysplasia with multiple enostoses. It is not associated with impaired fracture healing.
