The decision to choose between a CTLSO (Milwaukee brace) and a TLSO (such as the Boston system, Wilmington, Miami or Rosenberger orthosis) is affected by several factors including cosmesis, geographical preference and popularity of a given orthosis. Performance usually is a secondary consideration since objective comparisons have been difficultA finite element model was used to quantify and compare the effects of the CTLSO and TLSO in increasing spinal stability as measured in terms of the critical load of right primary thoracic with left lumbar compensatory and left primary lumbar with right compensatory idiopathic scoliotic curvesWhile the CTLSO and TLSO were equal in stabilizing lumbar primary curves, the TLSO was 25 percent less effective in stabilizing primary thoracic curves. Pad and counterforce placement were critical factors influencing stability for both the CTLSO and TLSO, demonstrating the importance of proper initial fit and timely growth adjustments to ensure proper pad placement throughout the duration of wear