rheumatology and orthopaedics

Question 1

what are metabolic bone diseases

Answer 1

group of diseases that cause reduced bone mass and

reduced bone strength

Question 2

what causes metabolic bone diseases

Answer 2

imbalance of various chemicals in the body

vitamins, hormones, minerals, etc

Question 3

effect of metabolic bone diseases on bone

Answer 3

altered bone cell activity, rate of mineralisation, or

changes in bone structure

Question 4

what bone mineral density T-score defines osteoporosis, and what measures this

Answer 4

-2.5 or lower, measured by DEXA (standard deviations different from mean peak bone mass BMD); normal microstructure but decreased bone mass

Question 5

2 primary causes of osteoporosis (no external cause)

Answer 5

age, post-menopause (5-7 years after)

Question 6

4 secondary causes of osteoporosis (external causes)

Answer 6

drugs, systemic disease, nutritional defects, genetic conditions

Question 7

high vs low turnover osteoporosis

Answer 7

high turnover (formation and resorption increased, but resorption > formation) vs low turnover (both decreased, but formation < resorption)

Question 8

osteoporotic bone vs normal bone

Answer 8

large sections of trabecular bone reabsorbed (free-floating, thinner), followed by thinning of cortical bone, causing compression fractures in long bone; identified by serum markers

Question 9

define pathology

Answer 9

disease process that gives rise to symptoms, signs,
biochemical disturbances and changes in imaging
appearance

Question 10

define radiological sign

Answer 10

change in imaging appearance, whether structural or functional, that may point towards a pathology

Question 11

2 functions of imaging relating to bone functions

Answer 11

reveal structural failures such as fractures and ligamentous injuries, serve as proxy to metabolic dysfunction

Question 12

5 imaging techniques

Answer 12

x-rays, CT, bone densitometry, MRI, radionuclide bone scans

Question 13

what 3 techniques look at density

Answer 13

x-rays, CT, (both: less dense = darker, more dense = lighter), bone densitometry e.g. DEXA

Question 14

what does MRI look at

Answer 14

biochemical composition (whiter areas show fat)

Question 15

what do radionuclide bone scans look at

Answer 15

bone turnover (e.g. hotter at degenerative disease sites)

Question 16

what T-score is classed as osteopenia

Answer 16

-1.5 to -2.5

Question 17

what 2 locations is used to image with DEXA for osteoporosis

Answer 17

lumbar spine, hips and femur

Question 18

DEXA for osteoporosis: after T-score

Answer 18

calculate likelihood of major fracture in 10 years time from femoral BMD; guidelines of management, including further imaging methods

Question 19

3 radiological signs of osteoporosis

Answer 19

loss of cortical bone/thinning of cortex, loss of trabeculae, insufficiency fractures

Question 20

what are insufficiency fracture /stress fractures due to, and 4 common locations

Answer 20

normal stress on abnormal bones; sacrum, underside of femoral neck, vertebral bodies, pubic rami

Question 21

X-ray/CT scan for insufficiency fracture

Answer 21

initially normal, can get periosteal reaction and callus, more commonly increased sclerosis around fracture lines

Question 22

MRI scan for insufficiency fracture

Answer 22

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

Question 23

radionuclide bone scan for insufficiency fracture if high turnover

Answer 23

increased osteoclastic activity > increased osteoblastic activity (increased bone turnover as bone attempts to heal - sclerosis)

Question 24

site for stress fracture in osteoporosis

Answer 24

principal tensile group e.g. underside of femoral neck

Question 25

DEXA scan on pelvis and sacrum

Answer 25

shows increased bone uptake (osteoclast activity) with dark patches, with white patches showing bone (marrow) oedema; H-sign on sacrum