LOOKING AFTER THE BONE HEALTH IN CHILDREN WITH ARTHRITIS

by Dr Vinaya Kunjir

Commercial advertisements are a part of almost all television programs and serials. The most common advertisement is a mother chasing her school-going child with a glass of milk, requesting him to drink milk and the child making excuses not to drink it. The mothers frequently ask the doctors,’ Doctor, my child refuses to drink milk everyday. Why is daily intake of milk so important?”

Because milk contains calcium which is very important for bone growth in children. Bone has two functions:

1) It forms the skeletal framework and gives support to our body.

2) It allows the locomotion of the body.

3) Bone marrow contains blood forming elements.

70% of the bone is made of minerals and collagen fibres. Minerals are mainly calcium and phosphorus which provide rigidity and strength to the bones. Collagen fibres give elasticity and flexibility to the bones. 30% of bone is made up of proteins which contain bone-forming cells(osteoblasts) and cells responsible for bone resorption (osteoclasts).

Bone remodeling is the name given to the process of bone formation and resorption. Any disturbance in bone remodeling leads to decreased strength of the bone.

Osteoporosis may result from disturbances in bone remodeling where

1) there is normal bone formation but faster bone resorption.

2) decreased bone formation with normal resorption

3) both decrease in bone formation and resorption.

Normal bone growth during childhood

The bone mass increases rapidly when the baby is in mother’s womb and during early months of infancy.

Bone mass increases parallel to the linear growth during childhood years. There is rapid increase in bone mass during the pubertal growth spurt. Peak bone mass is achieved during late teens and is a result of continued bone growth throughout the childhood years.

If there is a disturbance in this process, there is a resultant decrease in the peak bone mass and the resultant fracture risk may be increased for life. Thus, to prevent osteoporosis (OPS) and fracture risk in old age, there is a need to increase the bone mass and density during childhood and adolescence.

There are many factors which influence childhood skeletal growth and bone mass and density

• Nutrition- 90% of the calcium of the body is present in the bones. Calcium supplementation in childhood especially in children before puberty increases the bone density. Calcium in the diet is preferable to Calcium tablets as it is easily absorbed from the intestine. Also, Vitamin D is required for calcium absorption. Vit D can be easily prepared by the body by exposure to sunlight.
• Hormones – Hormonal influences during childhood have great effects on bone growth. 60% of peak bone mass is achieved during puberty. In children with sex steroid deficiency e.g. – Turner’s syndrome- the bone mass is low.
• Mechanical loading – it is important for bone development. Children who play games or are engaged in physical activity have increased bone mass.
• Environmental factors – there are several studies which show that consumption of alcohol and tobacco have a negative effect on the bone health.
• Genetics – studies have shown that 80% of peak bone mass attainment may be due to genetics. A family history of osteoporosis is an important risk factor for development of osteoporosis.

Measurement of Bone Density.

Bone health which means the ability to avoid fracture with trauma. It depends upon the nature of trauma and bone strength.

Bone strength depends on the structure and the material properties of bone. Structure of bone means the geometry of the bones. People of different races and culture have different bone structure. E.g.-Chinese women have a different structure of the hip bone as compared to white women.

Material properties of bone mean calcium content (mineralization) of bones. There are two types of bones-

1) Cortical bone- it is 80% calcified, found in hip bone, long bones and usually occurs in adults.

2) Trabecular bone- it is 15-20% calcified, found in Spine and is seen in children. Changes in response to stress like dietary deficiency and drugs are seen faster in trabecular bones than cortical bones.

Bone Mineral Density (BMD) is assessed with the help of Dual energy xray absorptiometry (DEXA) scan. Osteoporosis can be evaluated by the measurement of BMD of the hip bone (cortical bone) and the Spine (Trabecular bone). Special pediatric software should be used to assess a child’s BMD.

Bone Health in Juvenile Idiopathic Arthritis(JIA).

It is seen that the bone health of children with JIA is poorer than that of healthy children. Many factors have adverse effect on the peak bone mass in patients with JIA.

1) Medications- it is well-known that corticosteroids used in the treatment of JIA, cause osteoporosis. Drugs like cyclosporine cause osteopenia. But the beneficial effects of the drugs in controlling arthritis are much more than the osteopenic effects of these drugs.

2) Disease- active arthritis itself can cause osteopenia around the affected joints. Several studies have shown that children with JIA had low bone mass – both, before puberty and also during the pubertal growth spurt.

3) Physical Activity- Children affected by JIA, lupus and other rheumatological illnesses are less active physically and hence have low bone mass.

Treatment- Some studies have shown that children with JIA who receive Calcium and Vitamin D supplementation have increased bone mass while some studies found no s igni f i cant inc rease in bone mas s . Bisphosphonates are medications which decrease the osteoclastic activity ( ie- bone resorption) of the bone. There are several reports of normal growth in children receiving bisphosphonate treatment.

Calcium Rich Foods

• Yogurt
• Milk, whole
• Cheese
• Milk shakes
• Eggs
• Salmon
• Tofu
• Sardines
• Nuts- almonds, walnuts
• Spinach
• Vegetables- French beans, broccoli, red kidney beans
• Fruits- figs, apricots, orange

Thus, optimal calcium intake, increased physical activity and exercise, minimal use of steroids and control of disease activity are the best ways to prevent osteoporosis in children with JIA and other rheumatological diseases.

References-

1) Textbook of Paediatric rheumatology, 5th Edition- J Cassidy et al.

2) Current Rheumatology Diagnosis and treatment, 2nd Edition- J Imboden et al.

3) Rheumatic diseases Clinics of North America- Pediatric rheumatology, 2002.