MBD - Radiology

Question 1

Can you see metabolic dysfunction on radiological scans?

Answer 1

No just structural failures such as fractures and ligamentous injuries which could indicate metabolic dyfunction is acting.

Question 2

Which imaging techniques show bone density? Which scans show biochemical composition and bone turnover?

Answer 2

Density:

• X-rays
• CT
• Bone Densitometry
• MRI - biochemical composition
• Radionuclide bone scans - bone turnover

Question 3

Where do radionuclide tracers commonly go to?

Answer 3

Radionuclide bone scan - tracer goes to sites of increased osteoblastic activity. Commonly goes to:

• • site of joins (wear and tear and degenerative changes)
• • site of fractures
• • site of tumours
• • site of metabolic bone dysfunctions

Question 4

Describe the pathological features of these vertebrae.

Answer 4

• This is a CT - dense things in white and less dense darker.
• Picture 1 : The vertebrae images are T1 MRI- on these the fat shows up as white. When the bone is bright/almost as white as fat, it is because of the bone marrow which consists of a lot of fat. The vertebra above it is much darker which would suggest oedema, soft tissue lesion etc inside the bone. The one below it is completely collapsed.
• Picture 2: The first few vertebrae stand out from the others. This patient had radiotherapy in the past (which causes a lot of changes in the bone marrow). This has made them very well demarcated - they are radiotherapy related changes.

Question 5

What is the difference between a radiological sign and pathology?

Answer 5

Pathology - disease process that gives rise to symptoms, signs and biochmical ditsurbances and changes in imaging appearance.

Radiological sign - change in imaging appearance, whether structural or functional, that may point towards a pathology.

Question 6

What si osteoporosis?

Answer 6

• Decreased quantity of bone mass - microstructure is not abnormal, you just have less of it.
• Microstructure normal

Can lead to: fragility fractures, bone deofrmity and pain.

Question 7

How is osteoporosis diagnosed?

Answer 7

By bone densitometry (aka dual-energy absortiometry, DEXA)

• Measure of BMD
• Compares BMD to normal reference databases (T-score or Z-score)
• T- score -1.5to -2.5=osteopenia; less than -2.5 = osteoporosis.
• Usually BMD is measured in lumbar spine and hips.

Question 8

What is used to assess fracture risk? How?

Answer 8

FRAX

The BMD T-scores are not very helpful at telling us about risks so we assess risks by typing in results into FRAX

• Age
• Sex
• Weight
• Height
• BMD

Tells you 10 year probability of a major fracture and the probability of a hip fracture.

You can then click onto the nogg guidelines which are linked below.

Question 9

What are the indications for deciding to do a DEXA scan?

Answer 9

We can’t just do a DEXA scan on all over 55’s so instead we do them when we see signs of osteoporosis:

• Loss of cortical bone/ thinning of cortex
• Loss of trabeculae
• Insufficiency fractures

Question 10

What is an insufficiency fracture and what are the common sites?

Answer 10

• These are stress fractures due to normal stress on abnormal bones(osteoporosis/osteomalacia)

Common sites:

• • Sacrum
• • Underside of femoral neck
• • verterbral bodies
• • pubic rami

Question 11

What are the radiological signs of osteoporosis? (CT/XR, Bone scan, MRI)

Answer 11

XR/CT

• • initially normal
• • can get periosteal reaction and callus formation in the later stage.
• • more commonly there is increased sclerosis around the fracture lines that never seems to heal.

MRI

• • bone oedema i.e. low signal on T1, high signal on T2 and STIR.

Bone scan

• • Increased osteoblastic activity i.e. increased uptake, as things attempt to heal.

Question 12

Describe what can be seen on these X-rays and which bone disorder could cause these radiological signs.

Answer 12

This is an example of a femoral fracture. This bone is normal but when compared to the bottom 2 images you can see that they are much darker, signifying osteoporosis. There is also a fracture on the right probably an insufficiency fracture.

Question 13

What is the name given to the radiological sign seen on the sacrum ? What other signs of osteoporosis are seen on the CT and MRI?

Answer 13

• HONDA SIGN - looks like a H
• CT - normal bone would have a similar density throughout however on this picture there are areas which have increased density, called “sclerosis”on CT
• MRI - there are also areas of high intensity on this image (similar areas)

Bone scan shows increased bone turnover in the same areas; these points could cause an insufficiency fracture.

Question 14

What is the Honda sign and why does it occur?

Answer 14

The Honda sign (H sign / H pattern) is a term used to describe the appearances of bilateral sacral insufficiency fractures on a radioisotope bone scan.

Usually due to osteoporosis?

Question 15

what is the difference between osteomalacia and osteoporosis?

Answer 15

Osteoporosis is reduced amount of normal bone but no abnormalities to the architecture. Osteomalacia is decreased bon mineralisation but amount of bone is still normal.

Question 16

What is a Looser’s zone?

Answer 16

• They are pseudofractures at high tensile strength areas
• Considered a type of insufficiency fracture
• Have sclerotic irregular margins
• Occur at right angles to the cortex
• Transverse part way through a bone
• Associated with osteomalacia and rickets

Question 17

What can too much unmineralised osteoid lead to in osteomalacia?

Answer 17

Looser’s Zone

Question 18

What are the most common sites of Looser’s zone formation?

Answer 18

• Medial proximal femur
• Lateral scapula
• Pubic rami
• Posterior proximal ulna
• Ribs

Question 19

What is shown in this image? Which bone disorder does this correspond to?

Answer 19

• Looser’s Zone - luscent short line at right angle to cortex with irregular sclerotic margins surrounding it.
• This is a sign of osteomalacia.

The bone would also be bent due to being osteopenic causing the whole femur to be a curved shape

Question 20

What are cod-fish vertebrae? What conditions are they seen in?

Answer 20

Biconcave deformity of vertebrae

Seen in osteoporosis, osteomalacia.

Question 21

Differentiate between these 4 vertebral columns.

Answer 21

Picture 1 - normal
Picture 2 - wedge fracture, vertebral body collapse.
Picture 3 - cod fish vertebra due to biconcave appearance
Picture 4 - cod fish vertebra due to osteopenia and bone is darker than normal.

Question 22

List the radiological signs of rickets.

Answer 22

• Indistinct/frayed metaphyseal margin
• Widened growth plate without calcification
• Cupping/splaying metaphyses due to weight bearing
• Enlargement of anterior ribs
• Osteopenia

Question 23

Describe why there are differences in the radiology of osteomalacia and rickets. What are they?

Answer 23

Differences depend on age and closure of growth plates.

If the patient is an adult with mature skeleton and closed over growth plates then the signs of osteomalacia will be…

• Osteopenia
• Looser’s zones
• Codfish vertebrae
• Bending deformities

In children where growth plates are not closed yet, the signs of rickets will focus mainly on these growth plates.

• Before growth plate closure
• Signs centeres around growth plates
• changs of osteomalacia

Question 24

Compare the metaphysis of the first and second hand. What condition is this?

Answer 24

First is normal and second is rickets.

Second has a frayed metahyseal margin which is a sign of rickets. There is also cupping.

Question 25

What are enlarged anterior ends of ribs a sign of?

Answer 25

Rickets - bones are also bent and osteopenic.

Question 26

What are the differences between primary and secondary hyperparathyroidism (the effects of which will be seen in radiology)?

Answer 26

_Primary_ (due to parathyroid adenoma) * PTH UP, Ca DOWN, phosphate DOWN * **Bone resorption** _Secondary_ (due to systemic biochem imbalance, CKD, rickets/osteomalacia) * PTH UP, Ca DOWN, phosphate N/DOWN * **Bone resorption AND increased density** * (Tertiary (autonomous)* * *PTH UP, Ca UP, phosphate DOWN)*

Question 27

What are the different types of bone resoprtion seen in hyperparathyroidism?

Answer 27

* Subperiosteal * Subchondral * Intracortical * Brown tumours - if the lesions are large. ## Footnote *Image- if you compare the right and left edges of the second bone it is clear that the left edge is more sharp than the right. This is as a result of subperiosteal erosion.*

Question 28

What is the name of this lesion? What condition?

Answer 28

Brown tumour ## Footnote *Hyperparathyroidism although radiologically this is very hard to distinguish from causes such as inflammation, bone tumour, cancer of the bone etc. Differential diagnosis comes from the history.*

Question 29

How is renal osteodystrophy associated with HPT?

Answer 29

It is basically a type of secondary hyperparathyroidism.

Question 30

Describe the radiological signs of renal osteodystrophy.

Answer 30

* Osteomalacia and osteoporosis * Secondary hyperparathyroidism * Subperiosteal erosions, brown tumours * Sclerosis – vertebral endplates giving a rugger jersey spine * Soft tissue calcification (vessels, cartilages) Image below shows Looser's zone and osteopenia, bending of the bone aand unsufficiency fractures at end plates. This associated with osteomalacia and osteoporosis.

Question 31

What is worng with this knee joint?

Answer 31

menisci at the knee joint get calcified. Osteochondrosis. Calcification of soft tissue/vessels/cartilage is a complication of renal osteodystrophy which is effedctively secondary HPT.

Question 32

Compare these 3 vertebral column and name the radiological sign shown.

Answer 32

Picture 1 - shows normal vertebrae Compare with picture 3 Picture 3 - normal density at the end plates and reduced density in the middle. This is called a rugger jersey spine - happens in **renal osteodystrophy** due to sclerosis.

Question 33

What are the phases of Paget's disease?

Answer 33

Paget's is a disease of BONE REMODELLING. Three phases: * Lytic phase * Mixed lytic/sclerotic phase * Sclerotic phase

Question 34

Summarise the effects of Paget's disease on the body.

Answer 34

* Disease of bone remodelling * bone pain, deformity, spontaneous fractures * May cause nerve entrapment, spinal stenosis and deafness * Osteogenic sarcoma

Question 35

What are the biochemical signs of Paget's disease\>?

Answer 35

* Raised serum alkaline phosphate * Urinary hydroxyproline * Pyridinoline cross-links

Question 36

What are the radiological signs of Paget's disease?

Answer 36

* Cortical thickening * Bone expansion * Coarsening of trabeculae * Osteolytic, osteoclerotic and mixed lesions * Osteoporosis circumscripta - round holes in bones

Question 37

What is seen in early phases of Paget's disease?

Answer 37

Mainly lytic and some sclerotic areas. * Thickened cortical bone and trabeculae * Fractures seen at the femur neck and at the inferior ramus of the pubic bone

Question 38

How do you know that this is Paget's disease?

Answer 38

* **Cortex** on affected bone in Paget's disease is a lot **thicker** than of a normal bone (middle picture: compare top bone to bottom bone) * **Trabeculae is coarsened** inside especially at the femoral head and neck. * The **bone is bent.** * If you do a radionuclide bone scan at the sclerotic phases then there will be increased uptake and the **bone will be noticably larger**. * Paget's tends to affect one bone and d**oesn't move to adjacent bone.**

Question 39

What is the name of this sign on the vertebral column uptake?

Answer 39

Mickey mouse sign Common in Paget's disease if there is increased radiotracer uptake on the bone scan in the spinous process and pedicles *CT- thickened cortex and coarsened trabeculae on the bottom image affecting the ilium and affecting the vertebrae on the top image.*

Question 40

How does Paget's disease affect the skull?

Answer 40

* Paget's can affect the skull and can also affect the mandible. * There are multiple lucencies, particularly in the highlighted areas. * This is osteoporosis circumscripta = nothing to do with osteoporosis; this is just the name for lucencies in the setting of Paget's disease.

Question 41

What is meant by a pepper pot skull?

Answer 41

Lucencies on the skull which signify intracortical resorption. Lucencies can be very small as shown on the right. This is caused by resoprtion of bone in **hyperparathyroidism**. here is a loss of definition between the inner and outer tables of the skull and a ground-glass appearance as well as spotty deossification.