Bone Pathology

Question 1

Vitamin D Life

Answer 1

skin and diet-> blood -> liver -> Vitamin D (OH)1-> kidney -> Vitamin D (OH)2

Question 2

In summary, for healthy bone

Answer 2

Ca, P (diet)
Vit D (diet, skin synthesis)
gut (absorbing Ca, P, Vit D)
kidney (makes Vit D (OH)2, resorbs/excretes Ca, P)
parathyroids (master gland for Ca, bone metabolism)

Question 3

bone healing complications

Answer 3

Mal-alignment: deformed healing

Non-union / mal-union / pseudoarthrosis

Osteomyelitis (compound fractures)

Growth disturbance (epiphyseal plate injury in children)

Arthritis (if fracture affects articular surface)

Fat embolism syndrome (within several days of fx)

Immobilization complications

• Thrombophlebitis/thromboembolism
• Osteoporosis of immobilized bone

Question 4

causes for osteopenia

Answer 4

osteopenia: Generalized decrease in bone mineralization

osteoporosis, osteomalacia, malignancy, rare hereditory diseases

Question 5

Pathological fracture

Answer 5

fracture through diseased bone—usually refers to fracture through tumorous or tumor-like bone

Question 6

best osteoporosis prevention

Answer 6

maximize peak bone mass (teens/young adults)

encourage weight-bearing exercise and Ca supplementation

Question 7

strong predictor of osteoporosis risk

Answer 7

Maternal hip fracture:

Question 8

Baseline labs: to exclude secondary causes of osteoporosis/osteopenia

Answer 8

serum Ca, P, alkaline phosphatase, 250H – Vit D, TSH, sometimes PTH (renal insufficiency or malabsorption)

Question 9

Most anti-osteoporosis meds

Answer 9

inhibit bone resorption

Question 10

Biochemical serum markers of bone formation and resorption:

Answer 10

currently NOT sufficiently standardized or studied to provide meaningful diagnostic or therapeutic guidance

Question 11

PRIMARY HYPERPARATHYROIDISM

Answer 11

Hypercalcemia due to primary hyperplasia or NEOPLASTIC enlargement of parathyroid glands

Spectrum of bony changes due to variable degrees of osteoclastic bone resorption—ranging from subtle subperiosteal cortical erosions to diffuse osteoporosis to tumor-like skeletal change (osteitis fibrosa cystica/”Brown tumor”)

Favors resorption of cortical bone over trabecular bone

Pathology: osteoclastic bone resorption/peritrabecular fibrosis = osteitis fibrosa
Some complications:
Fractures
Constitutional symptoms; metabolic impairment of kidneys; muscle weakness; neuropsychiatric syndromes (all direct effects of  Ca++)
Renal stone disease

NOTE: Secondary hyperparathyroidism (renal disease) may also produce gross skeletal change.

Question 12

OSTEOMALACIA

Answer 12

Definition: decreased bone mineralization with excess osteoid (wide osteoid seams)
Due to interference with calcium, phosphate, or vitamin D metabolism: diagnostic challenge—what’s causing the interference?

Radiologically appears osteopenic (like osteoporosis)

May present with diffuse skeletal pain (without fracture)

Associations:
Environmental: classic childhood rickets
Poor diet;  sun exposure in northern latitudes
Intestinal malabsorption—commonest cause of Vit D deficiency in USA
Liver or renal disease (impaired hydroxylation of Vit D)
Rare congenital/inborn errors of metabolism
-Deficient Vit D hydroxylation
-Renal tubular phosphate leak
-End organ resistance to Vit D (OH)2

Question 13

OSTEOMYELITIS

Answer 13

“Primary” mode of acquisition: hematogenous spread to bone from often occult source elsewhere

“Secondary” mode of acquisition: spread to bone from adjacent contiguous infection (joint infection/other soft tissue infection)

“Direct” infection: e.g., compound fractures allowing direct injection of common bacteria onto raw fracture surfaces; orthopedic procedures ± prosthetic devices