Orthopaedic Topic on Osteomalacia

1. Osteoamalacia

2. Osteomalacia
• Rickets and osteomalacia are different
expressions of the same disease : inadequate
mineralization of bone.
• Osteoid throughout the skeleton is incompletely
calcified, and the bone is therefore ‘softened’
(Osteomalacia).
• In children there are additional effects on physeal
growth and ossification, resulting in deformities
of the endochondral skeleton (Rickets).

4. Etiology
• The inadequacy may be due to defects anywhere along
the metabolic pathway for vitamin D:
1) Nutritional lack
2) Underexposure to sunlight
3) Intestinal malabsorption
4) Decreased 25-hydroxylation (liver disease,
anticonvulsants)
5) Reduced 1α-hydroxylation (renal disease, nephrectomy,
1α-hydroxylase deficiency)
• The pathological changes may also be caused by calcium
deficiency or hypophosphataemia.

5. Active Form of Vit D

6. Pathology
• Defective bone mineralisation
• Decrease in Vitamin D
• Abnormal calcium and phosphate homeostasis
• Drugs interfere with the normal metabolism of
vitamin D to 25-hydroxyvitamin D and 1,25-
dihydroxyvitamin D

7. Clinical Feature of Osteomalacia
• Adults Osteomalacia has -
1) Insidious course
2) Patients may complain of bone pain
3) Backache and muscle weakness for many years before the diagnosis
is made.
4) Vertebral collapse causes loss of height, and existing deformities
such as mild kyphosis or knock knees – themselves perhaps due to
childhood rickets – may increase in later life.
5) Unexplained pain in the hip or one of the long bones may develop a
stress fracture.

8. Diagnosis
• With clear cut clinical and x-ray features the
diagnosis is obvious.
• In less typical cases a bone biopsy will provide
the answer.
• Osteoid seams are both wider and more
extensive, and tetracycline labelling shows
that mineralization is defective.

9. X-ray Finding
• The classical lesion of osteomalacia is the
– Looser zone, a thin transverse band of rarefaction in an otherwise normal-
looking bone. These zones, seen especially in the shafts of long bones and the
axillary edge of the scapula, are due to incomplete stress fractures which heal
with callus lacking in calcium.
– There is simply a slow fading of skeletal structure, resulting in biconcave
vertebrae (from disc pressure).
– Lateral indentation of the acetabula (‘trefoil’ pelvis) and spontaneous fractures
of the ribs, pubic rami, femoral neck or the metaphyses above and below the
knee.
• Features of secondary hyperparathyroidism characteristically appear in
the middle phalanges of the fingers, and in severe cases so-called ‘brown
tumours’ are seen in the long bones.

10. Fracture in the mid-diaphysis of a long bone
following low-energy trauma
Champagne glass pelvis
Biconcave vertebrae
Looser’s zones

11. Biochemistry
• Changes common to almost all types of vitamin D related Rickets and
Osteomalacia are
1) Diminished levels of serum calcium and phosphate
2) Increased Alkaline Phosphatase
3) Diminished urinary excretion of calcium.
• In vitamin D deficiency
1) 25-OH D levels also are low.
2) Calcium phosphate product is diminished in rickets and
osteomalacia (derived by multiplying calcium and phosphorus
levels expressed in mmol/L).
3) Values of less than 2.4 are diagnostic.

12. Osteomalacia /Osteoporosis
Osteomalacia Osteoporosis
o Generally Unwell Well
o Pain Generalized chronic ache Pain only after fracture
o Mascular Muscles Weakness Muscles Normal
o Looser’s zone Looser’s Zone No Looser’s Zone
o Alkaline Phosphate Increased Normal
o Serum Phosphorus Decreased Normal
o Ca * P <2.4 mmol/L > 2.4 mmol/L

13. Treatment
• Dietary lack of vitamin D (less than 100 IU per day) is common in strict
vegetarians, in old people who often eat very little and even in entire
populations whose traditional foods contain very little vitamin D. The use
of sun-blocking lotions, or overall cover by clothing, may seriously reduce
exposure to ultraviolet light. Some of these problems can be corrected by
simple social adjustments.
• Treatment with vitamin D (400–1000 IU per day) and calcium supplements
is usually effective; however, elderly people often require larger doses of
vitamin D (up to 2000 IU per day).
• Intestinal malabsorption – especially fat malabsorption can cause vitamin
D deficiency (fat and vitamin D absorption go hand in hand). If vitamin D
supplements are administered they have to be given in large doses (50
000 IU per day).
• Surgery Established long-bone deformities may need bracing or operative
correction once the metabolic disorder has been treated.

14. Oily fish
Milk
Cheese
Egg Yolk
Mushrooms
Soya, Beans
Broccoli
Oysters
Butter
Orange, Nuts