Childhood obesity associated with endocrine factors, orthopaedic problems

“More than half of obese children had low enough vitamin D levels to have mild bone health effects and a high rate of thyroid hormone dysregulation. This may be partially due to the obesity itself but also might be due to the diet that the children have,” said Benjamin Alman, MD, during his presentation at the Pediatric Orthopaedic Society of North America annual meeting.

“Dietary factors and inappropriate levels of calcium may slow the growth plate and thyroid hormones. Insufficient vitamin D levels and inappropriate amounts of leptin may also inhibit the growth plate from normal development,” Dr. Alman added.

These growth plate problems can lead to unique orthopaedic challenges such as slipped capital femoral epiphysis (SCFE).

“Obesity can predispose the child to the development of SCFE by increasing the shear forces at the proximal femoral growth plate,” he explained. “Hormone abnormalities associated with obesity, such as hypothyroidism and Prader-Willi syndrome, may also predispose the young patient to SCFE.”

Treating the obese child with SCFE
Reports have shown that the traditional treatment for SCFE—placing a single percutaneous screw across the growth plate—has not always prevented slippage of the epiphysis in the obese child.

As a result, some surgeons have recommended that two screws be used. But Dr. Alman does not think this may be the most appropriate treatment. The single screw method was adopted to prevent the complication of screws migrating to the wrong position.

“A surgeon may decide to use multiple screws after doing a thorough risk/benefit analysis. If a slip heals but the deformity is unacceptable, the osteotomy can be done at a later date,” he said.

Acute slips are also being treated with surgical dislocations and open reductions. “In obese patients, a larger incision is needed and the size of the limb can complicate the approach” he noted. The larger incision that has to be made to accommodate for the size of the obese patient increases risk of infection.

While surgical dislocations can provide a direct view of the anatomy and may decrease the rate of osteonecrosis, it is a technically demanding procedure and requires specialized training. In addition, there is a lack of comparative studies demonstrating a superiority of one approach over another.

Other orthopaedic conditions
Blount’s disease is also common among obese children.

“The overload on the medial side of the growth plate along with tension on the lateral aspect is thought to cause asymmetric growth and the tibial deformity,” Dr. Alman explained.

“Analysis of forces and gait patterns suggests that obesity alone may be sufficient to cause this asymmetric growth,” he said.

Studies have also suggested obese children are at greater risk for fractures.

Dr. Alman believes this may be due to increased mechanical load and a relative decrease in bone density as a function of their weight. Obese children’s decreased overall activity level may also predispose them to injury. The extra mass and decreased condition may impart greater stresses on the bone with an injury causing a fracture.

“Fracture treatment may be complicated because the hardware may not be strong enough. A lot of these children have difficulty with protected weight bearing,” Dr. Alman explained. “It’s very hard for some of these children who weigh 300 pounds or 400 pounds to be partially weight bearing or use crutches.”

Very large children may require adult implants or different types of implants, according to Dr. Alman. For example, an overweight child with a mid-shaft femur fracture and open growth plates may not be a good candidate for flexible nails because the nails may fail due to the weight of the child.

Cast immobilization, particularly a short leg cast, can also be very challenging for a morbidly obese child.

In addition to a higher incidence of fractures, these children often have valgus foot with malalignment and sustain stress fractures. The weight is believed to cause a mechanical collapse of the foot causing this alignment.

“The management of painful feet in these children is problematic. Inserts in their shoes rarely seem to work. Weight reduction seems to be an essential component in pain relief,” he stated.

Next steps for the orthopaedic surgeon
“Obesity may also result from other conditions,” Dr. Alman said.

In a study of more than 1,000 patients who had obesity, 20 patients were diagnosed with other medical disorders (Table 1).

“If you see a child in your clinic who is overweight, he or she may have one of these conditions or syndromes. Medical treatment is available to manage these disorders and decrease the weight of the child,” he said.

Dr. Alman advocates using a multidisciplinary program when treating an obese child. “Any program needs to address what is causing the problem in that child. Modifications in both diet and activity levels may be required. Endocrine dysregulation may also need to be managed.”

“Orthopaedic surgeons can help patients and their parents find the appropriate dietary and activity programs that will facilitate weight loss. We can be part of the multidisciplinary team helping these children and their families find healthier lifestyles,” Dr. Alman concluded.

Dr. Alman, a pediatric orthopaedic surgeon with the Hospital for Sick Children at the University of Toronto, reports the following disclosure: Canadian Institutes of Health Research.

Annie Hayashi is the senior science writer for AAOS Now. She can be reached at hayashi@aaos.org

Fast Facts

• An estimated 22 million children younger than 5 years were overweight worldwide in 2007.
• 75 percent of the world’s overweight children live in low- and middle-income countries.
• The percentage of obese children in North America has more than tripled since 1970—from 5 percent to 16 percent.
• Genetics, diet, and a sedentary lifestyle—in part due to poverty and crime—contribute to the increase in childhood obesity

The hidden causes of childhood obesity
Poverty plays an important role in childhood obesity, according to Dr. Alman. The incidence of childhood obesity is lower in cities such as Manhattan Beach, Calif., and Beverly Hills, Calif.—areas of affluence and low crime rates.

But childhood obesity is higher in South Central Los Angeles—an area with very low incomes and high crime rates.

Dr. Alman doesn’t think that this disparity can be entirely blamed on fast foods or poor eating habits. He points to the high crime rate as a culprit in this obesity epidemic.

“Poorer children often have limited playground resources and there may be a lot of crime in the neighborhoods, making it very difficult for them to go outside and play,” he said.

“It is actually safer for parents to keep their children inside the house than to have them go outside and play—putting them in harm’s way. This lack of activity predisposes these children to obesity,” he explained.

In addition to these environmental factors, studies on twins have suggested that being overweight is a 50 percent to 75 percent inherited trait, according to Dr. Alman.

“If a young child has an obese biological parent, that child has an odds ratio of roughly 3 for obesity,” he said.

“Genetics also influences basal metabolic rate, feeding behavior, energy expenditure in response to overfeeding, lipoprotein lipase activity, and basal rate of lipolysis,” he added.