The Risk of Slipped Capital Femoral Epiphysis and Adolescent Tibia Vara Depends On Where You Live

Purpose: Slipped capital femoral epiphysis (SCFE) and adolescent Blount’s disease (adolescent tibia vara, ATV) occur more frequently in obese children.  In order to understand the role that the food environment plays in the risk of these two musculoskeletal disorders of childhood obesity, we examined the risk of SCFE and ATV associated with increases in children’s RFEI. The retail food environment index (RFEI) is a ratio of retail food outlets near an individual’s home unlikely to offer healthy food choices to those more likely to do so.  Previous studies have demonstrated the association of the local retail food environment and the prevalence of obesity and diabetes among adults. 

Methods: The records of all patients treated for SCFE/ATV from 2000-2009 were reviewed.  After excluding patients with a metabolic bone disorder and those for whom the RFEI could not be calculated, 24 cases of SCFE/ATV were included in the study.  As a control group with a musculoskeletal disease unrelated to obesity, 127 gender/age-matched patients with a distal radius-ulna fracture were randomly selected.  Retail food outlet locations were obtained from the state department of agriculture and markets and the county health department and mapped, along with children’s home addresses, using geographic information system software.  Each child’s RFEI was calculated by dividing the number of fast-food restaurants and convenience stores by the number of grocery stores, produce vendors, and farmer’s markets around their home.  Multivariate analysis and logistic regression were used to determine the risk of SCFE/ATV associated with increases in RFEI.

Results:   There were no differences in the mean age or gender of the cases and controls.  The rate of obesity was higher among cases of SCFE/ATV (83.3%) than among controls (29.1%, p<0.0001).  The difference between the mean RFEI for patients with SCFE/ATV (11.5, SD=6.4) and the control group (6.6, SD=4.8) was statistically significant (p<0.01).  After multivariate analysis controlling for BMI, age, gender, race, and urban residence, there was still a statistically significant increase in the risk of SCFE/ATV associated with an increase in RFEI (OR: 1.13, 95% CI: 1.02–1.26).

Conclusions: This study found an association between an unhealthy RFEI score and the risk of SCFE/ATV independent of a child’s BMI.  Because the RFEI risk factor is independent of weight, we suspect the increased risk from living in areas with a high ratio of unhealthy to healthy food choices is due to factors beyond just increased calories and may be related to other nutritional or environmental factors.  Our study may be the first to evaluate the association of the local retail food environment and obesity-related musculoskeletal disorders in children.  These findings suggest health policies aimed at improving the food environment may help change the prevalence of obesity and the risk of associated health complications.