June 2010

Obesity impairs children’s response to orthotic therapy for flexible flatfoot

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Is earlier intervention needed?

Researchers and clinicians are only beginning to understand the relationship between pediatric flexible flatfoot and obesity, which becomes even more complicated in the context of orthotic treatment. Findings from Hong Kong appear to throw another wrinkle into the mix, suggesting that obese children are significantly slower to respond to orthotic therapy than their normal-weight counterparts.

Investigators from the North District Hospital in New Territories, HK, analyzed nine pairs of children with flexible flatfoot treated with insoles that provided support for the medial longitudinal arch. In each pair, one child met the study’s criteria for obesity, which was defined as body weight more than 20% greater than the median body weight in Hong Kong for a given height. The children were followed for a mean of 3.3 years.

Change in arch development was assessed using an ink footprint, from which the Staheli arch index was calculated. The researchers found that the obese children demonstrated a 68% slower rate of  arch index improvement than the non-obese children, said Sam Law, MPhil, BscPO, who presented his group’s findings at the ISPO meeting in Leipzig.

Law gave an example of a seven year old girl with an arch index of 1.40, who was predicted to improve at a rate of 0.16 per year. She would be 10 years old by the time the researchers would expect to see significant improvement.

This becomes an issue when considering the timing of surgical intervention in children who do not improve appreciably with orthoses. At North District Hospital, the optimal age for surgery is based on the resting calcaneal stance angle: 10.5 years if the RCSA is greater than 5º and 12.5 years if it is equal to or less than 5º. The findings suggest that more aggressive interventions should be considered at an earlier stage in children in whom a slower rate of arch development would be expected.

“These data can help us give appropriate treatment to these patients,” Law said.

Without appropriate intervention, obese children with flexible flatfoot will grow up to pose even greater clinical challenges as adults, according to Paul Scherer, DPM, founder of ProLab Orthotics in Napa, CA, and immediate past chairman of applied biomechanics at the California School of Podiatric Medicine in Oakland.

“As these children grow their dysfunctional feet are going to create problems that are going to make their way into our offices,” said Scherer, who presented on obesity and pediatric flexible flatfoot at the FIP meeting in Amsterdam.

Although not all children who develop flexible flatfoot are obese, a number of studies show an association between the two conditions, most recently a 2009 Taiwanese study in which flexible flatfoot was diagnosed in 56% of obese children vs 27% of normal-weight children.

“I could not find one study that said obese children have a lower rate of hypermobile flatfoot,” Scherer said.

The question of which children with flexible flatfoot should be treated with orthoses, however, remains controversial (see “Numbers needed to treat? The pediatric flexible flatfoot debate,” January, page 22).

At North District Hospital, all pediatric flexible flatfoot patients receive orthotic therapy, regardless of whether they are obese or symptomatic, Law said.

An evidence-based clinical pathway proposed last year, however, recommended that children who are asymptomatic be monitored rather than automatically treated with orthoses.

“We don’t need to treat every flatfoot,” Scherer said. “We will be criticized for overtreatment and that will reflect negatively.”

Despite pharmaceutical advances for RA, long-term foot pain, disability persist

Pharmaceutical interventions can significantly decrease symptoms associated with rheumatoid arthritis, but foot-specific pain and disability persists as the disease progresses, according to research from the Jan van Breemen Institute in Amsterdam.

In a cohort of more than 800 patients, investigators have found that metatarsophalangeal joint swelling decreases significantly with the first two years of taking medication, but then plateaus for the next six years. Similarly, disability decreases with medication from about 60% to 40%, but does not decrease further. Meanwhile, erosions increase significantly, from 20% in the first year to 60% by year eight.

“Those with walking disability at two years were very likely to still have a walking disability at eight years. So it’s very important to try to increase their walking ability early on,” said Marike van der Leeden, MSc, PT, a researcher in the department of rehabilitation medicine and psychology at the institute, who presented her group’s findings at the FIP meeting in Amsterdam.

In a subgroup of 62 patients, van der Leeden and colleagues found that plantar pressure, pressure time integral, and inflammation were correlated with pain, and that gait parameters were correlated with disability. They also found that disease duration was associated with increased forefoot plantar pressure, decreased toe contact, increased contact time, and a later heel rise during the rollover phase of gait.

“During the disease process, function of the foot decreases and you see a more shuffling gait,” van der Leeden said. “Don’t ignore the foot, even if the disease is inactive.”

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