ORTHOPEDIC PROBLEMS OF

METABOLIC BONE DISEASE

Bone

= Bone is an active organ, made up of

tissue and cells in a continual state of

activity throughout a lifetime

= Highly vascular structure.

= Storage of Ca, phosphate, Mg, …etc

= 1 – 2 kg Calcium,

= 1 kg Phosphate.

Compositions of the bone

• The matrix– 40% organic

• 30% Type 1 collagen (tensile strength)

• Proteoglycans (compressive strength)

• 5% Osteocalcin / Osteonectin

• Growth factors/Cytokines/Osteoid

– 60% inorganic : Calcium hydroxyapatite

• The cells – Osteoblast / clast / cyte /progenitor

Bone cells

Bone metabolism depends on

= PTH, Vitamin D, Calcitonin.= Other hormones

-Estrogen prevent bone loss

-Corticosteroids increase bone loss

-Thyroid hormones T4 bone resorption

-GH +ve calcium balance

-Growth factors (PDGF) bone & cartilage repair

Stages in bone development 1-The growth stage

Lasts until about age 20 when the length of

bone growth ends.

2-The modeling stage

Bones can change shape and become thicker

and more durable.

The growth stage

3-Remodeling stage

the replacement of old bone tissue with new

tissue, goes on throughout adulthood.

but after about age 34, the balance between

bone breakdown and reformation begins to

end, leading to an inevitable loss of bone

mineral density (BMD) with age.

Remodeling of Normal bone

– Osteoblasts Produces organic matrix

– Matrix maturation

– Mineralization of mature matrix

– Osteoclastic resorption of mineralized bone

Remodelling increases with age.

• 25% cancellous & 3% cortical bone / Y.

• 50% of trabecular & 30% of cortical bone in

lifetime in female.

• 18% of total skeleton deposited or removed /Y.

When bone turnover is increased, bone loss dominates

Factors affecting bone turnover

Local factors

*I-LGF 1 increased osteoblast prolif.

*TGF increased osteoblast activity

*IL-1/OAF increased osteoclast activity

(myeloma)

*PG’s increased bone turnover (#’s /inflam)

*BMP bone formation

Calcium

• Human body is very sensitive to “Calcium”

• CVS, Muscles, CNS need calcium for –

= Conductivity

= Contractility

= Irritability

• 99% stored in bones

Calcium

• +ve balance in the 1st 3 decades.

• Peak bone mass bet. 16-25y.

• -ve = = after 4th decades.

• 0.3% - 0.5%/y bone loss.

• 2-3% loss postmenopause.

• 400 mg released daily from bone.

Calcium Requirement

• 600 mg/day in children

• 1300 mg/day in adolescents and young adults

• 750 mg/day in adults

• 1500 mg/day in pregnant women

• 2000 mg/day in lactating women

• 1500 mg/day in postmenopausal women

and patients with fractures

Regulation of Calcium Metabolism

• Minerals serum concentration

– Calcium , Phosphate , Mg

• Organ systems

Skeleton, GI tract ,Kidney

• Hormones

– PTH - Calcitonin -Vitamin D

– Sex hormones

Phosphate

• Normal plasma concentration?

2.4 - 4.1 (mg/dL)

(Daily requirement 1-1.5 g/day)

• Absorption and excretion? GIT & kidneys

• Regulation PTH

• 85% stored in bone

Bone-derived GF

Serum

phosphate

lowering effects of FGF23

= Increases urinary excretion of phosphate by inducing the

expression of both FGF23 (in bone) and Klotho (in kidney),

which results in decreased serum phosphate levels.

= Facilitate increased intestinal absorption of phosphate, which

increases serum phosphate .

the membrane-

bound protein Klotho

increased Ca/PO4

release

indirect increase in calcium reabs by stimulting vitamin D metabolism

increased Ca reabsorption

increased excretion of PO4

PTH Control of calcium levels

Calcitonin

• Levels increased when serum Ca

>2.25mmol/L

– Bone - suppresses resorption

– Kidney - increases excretion

Vitamin D Sources of Vit D

• Diet

• UV light on precursors in skin

• Normal daily requirement

= 400 IU/day Child

= 1000 IU/day Adult

• Target organs

– Bone - increased Ca release

– Gut - increased Ca absorption

Metabolic Bone Diseases

• Low bone mass : Osteoporosis, Scurvy

• High bone mass : Paget’s / Osteopetrosis

• Hypocalcemia:

Osteomalacia / Rickets / Hypoparathyroidism

Hypophosphatasia/ Renal Osteodystrophy

• High bone turnover :Hyperpara.

Reduced bone mass with normal mineralized

bone in reduced quantity.

• Excessive osteoclast bone resorption

• Increased risk of fracture at all skeletal sites

1-

Classification

• Primary Osteoporosis.

(Idiopathic) : more common

– Type 1 (Postmenopausal)

– Type 2 (Age-related or Senile)

Type 1: Post-menopause

• Menopausal loss 3% vs 0.3% previously

• Loss of oestrogen - Increase osteoclastic activity

Secondary Osteoporosis.

1- Metabolic (Acromegaly, Hypercorticism, Hyperthyroidism, Hyperparathyroidism, hypogonadism, pregnancy, D.M)

2- Congenital (OI, Ehlers DS, Gaucher disease)

3- Nutritional (alcoholism, malnutrition, calcium deficiency, scurvy)

4- Malignancy - Mets, M.M, Leukaemia

5- Drug-related (Steroids, Heparin, Smoking, Phenytoin)

6- Chronic disease - RA, AS, TB, CRF

7- Idiopathic - juvenile

Bone densitometry; Gold standard

1. Detection osteoporosis before fractures.

2. Determination disease severity.

3. Estimation risk of fracture.

* Serial BMD measurements enable determination of rate of bone loss or gain and thereby help in monitoring therapy.

Plain film; loss of 30% to 50% of bone is required before it is detected on conventional radiographs.

•To measure BMD in the spine, hip, wrist, or total body.

• Small DEXA machines that can measure the forearm,

finger, or heel are less expensive and are portable.

Screening - DEXA

Generalized osteopenia.

* Cortical thinning and accentuation of weight bearing trabeculae.

* The bone surfaces are well defined, with sharp margins.

= Generalized osteopenia, compression fractures.

= Biconcave vertebral endplates (fish vertebra).

= Thin, well-defined vertebral cortices.

Treatment of osteoporosis

Prevention

= Lifestyle factors

= Smoking

= Physical activity and exercise

= Falls prevention

= Public awareness

Without minerals

Without Collagen

Effects of steroids on bone loss

• Steroids for several days causes bone loss

more on axial bones ( 40 %) than on

peripheral bones ( 20%).

• Muscle weakness

• Prednisolone more than 5 mg /day for long

time

Preventing steroid induced

osteoporosis

• All: lifestyle advise, calcium and Vit D

= Age <65

DEXA- if T score -1.0 or less

Bisphosphonates

= Age >65 Bisphosphonates

1. Immobilization and disuse

2. RSDS

3. Transient regional osteoporosis

* Transient osteoporosis of the hip.

4. Inflammatory arthritis.

5. Tumors

6. Infection.

* RSDS : mediated by the SNS and is

characterized by

* aggressive osteoporosis,

* soft tissue swelling.

The cause is usually traumatic, but the

disease may also be idiopathic.

1. Pronounced demineralization of the bones, esp. the

periarticular region.2. No joint involvement.3. Associated soft tissue atrophy.

“Complex regional pain syndrome”.

* Rickets and Osteomalacia are similar

histologically.

* Abnormality in Vit. D metabolism.

* Incomplete mineralization of normal

osteoid tissue.

2-

Osteomalacia

= Stunted skeletal growth.

= Kyphosis, joint enlargement,

= Angular deformity, bowing, valgus.

= Fractures and SCFE.

Osteomalacia: more subtle.

* Fatigue, malaise, or bone pain.

* Proximal muscle weakness and

abnormal gait may be present.

Generalized osteopenia.* Coarsened and indistinct bony trabeculae.

* Looser's zone, or pseudofracture. (more specific but less common)

* End plate deformities and fractures of vertebral bodies, bowing and fractures of long bones.

Looser's zone.* Linear areas of undermineralized osteoid

that occur in a bilateral and symmetric distribution.

* Characteristic sites

Inner margins of femoral neck, proximal ulna, axillary margin of the scapula, pubic rami, and ribs.

Generalized osteopenia. * Increased lucency, widening, elongation,

irregularity, and cupping of the metaphyses.

* Earliest: Slight axial widening of the physis

* Next: Increased lucency of the zone of provisional calcification.

* More advance: The physis widens and its contour becomes irregular.

* In patients with rickets caused by chronic renal disease, increased sclerosis may be seen, due to associated secondary hyperparathyroidism.

Vitamin D Resistant Rickets

• In the renal tubular disorders, rickets and

osteomalacia develop in the presence of

normal intestinal function and are not cured

by normal doses of vitamin D.

• Resistant or refractory rickets.

Defective final conversion of Vit. D in

to active form.

= 1ry : Parathyroid adenoma

= 2ry hyperparathyroidism

*Compensates for chronic low Ca. :- e.g. Renal failure or MAS

*[Ca2+] and [PO42-] normal, PTH high

= Tertiary hyperparathyroidism

*Hyperplasia in longstanding secondary disease

Hyperpara. either bone resorption or bone formation, bone resorption usually dominates.

3-

Generalized osteopenia.

Bone resorption, bone sclerosis, brown tumors, chondrocalcinosis, soft tissue calcification

* Brown tumors appear as well-defined lytic lesions.

* Bone resorption : the most characteristic finding,

subchondral, trabecular, endosteal, intracortical, subperiosteal, subligamentous, and subtendinous.

* Subperiosteal resorption

* Usually occurs in the hands and feet.

* radial aspects of the middle phalanges.

* Subchondral resorption

SIJ, sternoclavicular joints, ACJ joints, symphysis pubis

Subperiosteal resorption

Secondary

* Bony sclerosis; focal or generalized.

* Rugger-jersey appearance of spine.

* Soft tissue and vascular calcification.

Primary

• Chondrocalcinosis

• menisci of the knee,

• TFCC of the wrist,

• Pubic symphysis

Chondrocalcinosis

Secondary HPT. showing diffuse osteosclerosis.

2ry hyperparathyroidism shows generalized bone sclerosis

horizontal, bandlike ("rugger jersey") sclerosis of the vertebral bodies.

= Focal subperiosteal resorption involving a single bone

Neoplasms or osteomyelitis.

= Bone sclerosis in pts with 2ry hyperparathyroidism.

Metastatic disease, hypoparathyroidism, myelofibrosis, sickle-cell disease, and Paget's disease.

= Chondrocalcinosis

Pyrophosphate arthropathy (CPPD).

= Brown tumorsGCT and fibrous dysplasia.

Renal Osteodystrophy4-

RENAL OSTEODYSTROPHY

Spectrum of disorders seen in patients with chronic renal disease.

A- Bone mineralization deficiency

B- Hypocalcemia

All related to disorders of :

– Mineral ions Ca++, PO4--, Mg++

– Parathyroid hormone (PTH)

– Vitamin D metabolism

Orthopaedic problems

– Bone Pain • Low back, hips, legs aggravated by weight bearing

– Skeletal deformity, Growth retardation

– Periarthritis with deposition of ca

phosphate crystals

– Muscle weakness

– Ectopic calcification

- AVN

- Carpal tunnel syndrome

- Pathologic fracture

from brown tumors or amyloid deposits

- Osteomyelitis and septic arthritis

= It combines features of

= Rickets, Osteomalacia,

= 2ry hyperparathyroidism,

= Osteoporosis.

1= In children with CRF findings of rickets 2= In adults with CRF findings of secondary hyperparathyroidism

3- Patients with renal osteodystrophy

insufficiency fractures.

4- Patients with renal transplantation,

= Osteonecrosis,

= Insufficiency fractures,

= Tendinitis, and tendon ruptures.

Disorder of the adult skeleton in

which there is

= Accelerated osteoclastic-mediated

bone resorption

Paget’s Disease of Bone 5-

*Disease of bone remodeling

*Disorganised mosaic pattern bone with increased vascularity and fibrosis

* Fractures

* Nerve entrapment

* Spinal stenosis

* Osteogenic sarcoma

Polyostotic:

Skull & others

Bone scan:

Huge isotope

uptake