Nine pediatric patients (mean age 3.5 yrs) with low energy femur fractures were treated with 90/90 spica casts and developed leg compartment syndromes, Volkmann contracture, and ankle skin loss. These cases are detailed and a proposed mechanism leading to this devastating complication is explained. The authors believe the technique of an initial below knee cast, and then using that cast for applying traction while immobilizing the child in the 90/90 spica is potentially dangerous. Alternative spica application methods are advocated.